A COMPARATIVE ASSESSMENT OF PHYTOREMEDIATION AND SLOW SAND FILTRATION TECHNOLOGIES FOR THE SECONDARY TREATMENT OF SEWAGE EFFLUENT AND PUBLIC VIEWS ON THE USE OF TREATED EFFLUENT BY NAOMI ADRAKI (10105318) THIS THESIS IS SUBMITTED TO THE UNIVERSITY OF GHANA, LEGON IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE AWARD OF MPHIL ENVIRONMENTAL SCIENCE DEGREE JULY, 2014 DECLARATION I, Naomi Adraki, hereby declare that except for references cited, which I have duly acknowledged, this work is the result of my own research undertaken under supervision of Dr. Ted Annang and Dr. Dzidzor Yirenya-Tawiah of the Institute of Environment and Sanitation Studies (IESS) towards the award of a Master of Philosophy Degree in Environmental Science and that this work has neither in whole or in part, been presented anywhere for the award of any other degree. ……………………………………… ……………………………. NAOMI ADRAKI DATE (Student) ……………………………………… ……………………………. DR. TED ANNANG DATE (Principal supervisor) ………………………………………… ……………………………. DR. DZIDZOR YIRENYA-TAWIAH DATE (Co-supervisor) i DEDICATION This work is dedicated to my parents, Mr. and Mrs. Gabriel Anyigbah. ii ACKNOWLEDGEMENTS I am very grateful to the almighty God for the gift of life and for the wisdom to carry out this research. Many thanks to my supervisors, Dr. Ted Annang and Dr. Dzidzor Yirenya- Tawiah for their direction and support. I also wish to thank Dr. Aidan of Biogas Technologies Ltd for his great help. To the Environmental Unit of Valley View University, especially Mr. Solomon Adei, I say a very big thank you for granting me permission to use your Biogas facility for this research. Staff and students of IESS, thank you so much. To my family and friends, I say thank you for your support and prayers. God bless you. iii ABSTRACT This study evaluated and compared the performance efficiency of both technologies for treating sewage effluent from a Biogas facility at Valley View University (VVU) and also assessed public perception about the use of the treated effluent. Samples of the sewage effluent from the VVU Biogas facility were subjected to slow sand filtration over a ten week period using river bed sand and gravels, and phytoremediation using two plants, Pistia stratiotes L and Ipomoea aquatica Forsk. Pistia stratiotes survived in the raw effluent for five days, while Ipomoea aquatica survived longer (four weeks). The findings revealed that both plants reduce contaminant levels. However, Ipomoea aquatica had higher removal efficiency for phosphates (16.07%) and nitrates (100%). Pistia stratiotes on the other hand was more efficient at improving electrical conductivity (55.45%). The study showed that both slow sand filtration and phytoremediation using Ipomoea aquatica are equally efficient at improving turbidity and Chemical Oxygen Demand (COD). There were significant differences in values obtained for dissolved oxygen (DO), nitrates and phosphates. Based on the differences, SSF performed better at removing nitrates and phosphates while Ipomoea aquatica did better at enhancing dissolved oxygen. No significant differences were recorded for electrical conductivity (EC), Total Dissolved Solids (TDS), Total Suspended Solids (TSS), colour, and Biochemical Oxygen Demand (BOD). However, when the means were compared, SSF was better at removing TSS, BOD and colour whilst Ipomoea aquatica was better at removing EC and TDS. Both technologies were successful at reducing microbial load. This study also revealed that the parameters analyzed on the effluent discharged from the VVU Biogas facility fell within acceptable guidelines with the exception of EC. Majority iv of respondents agree that water is a scarce resource and that the Millennium Development Goal (MDG) on water cannot be achieved. Majority of people interviewed support the use of wastewater for medium contact options such as fire-fighting (71.6%), industry (52.9%), construction of buildings (71.6%), toilet flushing (81.4%), commercial car wash (46.1%), public parks and sports field irrigation (54.9%). Support for high contact options such as swimming pool, aquifer augmentation and laundry was low; 10.7%, 29.4% and 34.3% respectively and this is because respondents consider the treated water to be detrimental to health. Respondents supported the idea of wastewater reuse for reasons of water conservation and minimization of dependency on treated water whilst environmental protection ranked as the least frequent response. Education is needed to sensitize the public on treatment and use of wastewater. v LIST OF ABBREVIATIONS AAS Atomic absorption spectrophotometry ANOVA Analysis of variance BOD Biochemical oxygen demand COD Chemical oxygen demand DO Dissolved oxygen EC Electrical conductivity FC Faecal coliforms GEPA Ghana Environmental Protection Agency SSF Slow sand filtration TC Total coliforms TDS Total dissolved solids TSS Total suspended solids VVU Valley View University vi TABLE OF CONTENTS Content Page DECLARATION ................................................................................................................. i DEDICATION .................................................................................................................... ii ACKNOWLEDGEMENTS ............................................................................................... iii ABSTRACT ....................................................................................................................... iv LIST OF ABBREVIATIONS ............................................................................................ vi TABLE OF CONTENTS .................................................................................................. vii LIST OF PLATES .............................................................................................................. x LIST OF FIGURES ........................................................................................................... xi LIST OF TABLES ........................................................................................................... xiv CHAPTER ONE ................................................................................................................. 1 1.0 INTRODUCTION AND LITERATURE REVIEW .................................................... 1 CHAPTER TWO .............................................................................................................. 21 MATERIALS AND METHODS ...................................................................................... 21 2.1 Study site ................................................................................................................. 21 2.2 Materials .................................................................................................................. 22 2.3 Sewage treatment at VVU ....................................................................................... 23 2.4 Selection of sampling sites ...................................................................................... 23 2.5 Sampling of aquatic macrophytes ........................................................................... 23 vii 2.6 Preparation of filter media units ............................................................................. 25 2.7 Treatment of sample containers .............................................................................. 26 2.8 Monitoring of effluent quality at sampling site ....................................................... 26 2.8 Sampling of effluent for characterization................................................................ 27 2.9 Sewage effluent collection and experimental procedure ......................................... 28 2.9.1 Sewage effluent collection ................................................................................ 28 2.9.2 Slow Sand filtration (SSF) ................................................................................ 29 2.10 Phytoremediation ............................................................................................... 31 2.11 Laboratory analyses............................................................................................... 34 2.11.1 Physico-chemical analyses of raw and treated effluents ................................ 34 2.11.10 Analyses of Bacteriological Parameters of raw and treated effluents .......... 39 2.12 Social survey ......................................................................................................... 41 CHAPTER THREE .......................................................................................................... 42 3.0 RESULTS................................................................................................................ 42 3.1 Quality of sewage effluent from VVU biogas facility ............................................ 42 3.2 Phytoremediation using Pistia stratiotes and Ipomoea aquatica ............................ 43 3.3 Nitrogen and phosphorus uptake by plants ............................................................. 46 3.4 Contaminant removal efficiency of Ipomoea aquatica and Pistia stratiotes .......... 47 3.5 Weekly variations in water quality parameters after treatment with Ipomoea aquatica ......................................................................................................................... 49 viii 3.6 Performance of Slow Sand Filtration ...................................................................... 53 3.7 Comparison of phytoremediation using Ipomoea aquatica and slow sand filtration (SSF) technologies ........................................................................................................ 59 3.8 Microbial load ......................................................................................................... 80 3.9 Comparison of efficiency of experimental sand filter to the filtration system of the Biogas plant ................................................................................................................... 82 3.10 Quality assessment of safety of treated effluent for disposal/reuse ...................... 83 3.11 Public perceptions on water scarcity and the reuse of wastewater ....................... 87 3.11.1 Demographic background of respondents .......................................................... 87 3.11.2 Environmental perceptions ................................................................................. 87 CHAPTER FOUR ........................................................................................................... 102 4.0 DISCUSSION ....................................................................................................... 102 CHAPTER FIVE ............................................................................................................ 119 5.0 CONCLUSIONS ................................................................................................... 119 REFERENCES ............................................................................................................... 122 APPENDICES ................................................................................................................ 133 ix LIST OF PLATES Plate 1: Kpong Head Pond showing aquatic plants .......................................................... 22 Plate 2: Biogas facility of Valley View University .......................................................... 24 Plate 3: Filter media units; (a) gravels (5-10mm diameter), (b) coarse sand (2-3mm diameter), (c) fine sand (0.4mm diameter) .......................................................... 25 Plate 4: Sampling effluent from intermediary chamber for characterization ................... 28 Plate 5: Slow Sand Filtration experimental set up at the greenhouse .............................. 29 Plate 6: Pistia stratiotes in different dilutions of effluent ................................................. 33 Plate 7: Ipomoea aquatica planted in sewage effluent ..................................................... 33 Plate 8: Condition of Pistia stratiotes days after planting in sewage effluent ................. 43 Plate 9: Condition of Ipomoea aquatica days after planting in sewage effluent .............. 43 Plate 10: Sewage effluent before (A) and after treatment (B) with Pistia stratiotes ........ 44 Plate 11: Sewage effluent before (a) and after treatment (b) with Ipomoea aquatica ...... 45 Plate 12: Sewage effluent before (A) and after seventh week (B) of slow sand filtration 58 x LIST OF FIGURES Fig 1: Location map of study area .................................................................................... 21 Fig 2: Cross-section of slow sand filter media for Slow Sand Filtration of effluent ........ 30 Fig 3: Phosphate removal efficiency of Ipomoea aquatica and Pistia stratiotes ............. 47 Fig 4: Nitrate removal efficiency of Ipomoea aquatica and Pistia stratiotes ................... 47 Fig 5: COD removal efficiency of Ipomoea aquatica and Pistia stratiotes ..................... 48 Fig 6: EC removal efficiency of Ipomoea aquatica and Pistia stratiotes......................... 48 Fig 7: Concentration of dissolved oxygen (DO) in effluent after every week of treatment with Ipomoea aquatica ........................................................................................ 49 Fig 8: Biochemical Oxygen Demand (BOD) of effluent after every week of treatment with Ipomoea aquatica ........................................................................................ 50 Fig 9: Chemical Oxygen Demand (COD) of effluent after every week of treatment with Ipomoeaaquatica ................................................................................................. 50 Fig 10: Electrical conductivity (EC) of effluent after every week of treatment with Ipomoea aquatica ................................................................................................ 51 Fig 11: Total Dissolved Solids (TDS) of effluent after every week of treatment with Ipomoea aquatica ............................................................................................... 51 Fig 12: Concentration of phosphates in effluent after every week of treatment with Ipomoea aquatica ................................................................................................ 52 Fig 13: Concentration of nitrates in effluent after every week of treatment with Ipomoea aquatica ............................................................................................................... 52 Fig 14: Rate of filtration through experimental sand filter ............................................... 53 Fig 15: Weekly variations in turbidity of effluent treated using SSF method .................. 54 Fig 16: Weekly variations in electrical conductivity (EC) of effluent treated using SSF 54 xi Fig 17: Weekly variations in concentration of total dissolved solids (TDS) in effluent treated using SSF ................................................................................................. 55 Fig 18: Weekly variations in concentration of Total Suspended Solids (TSS) in effluent treated using SSF ................................................................................................. 55 Fig 19: Weekly variations in concentration of nitrates in effluent treated using SSF ...... 56 Fig 20: Weekly variations in concentration of phosphates in effluent treated using SSF 56 Fig 21: Weekly variations in concentration of dissolved oxygen in effluent treated using SSF ...................................................................................................................... 57 Fig 22: Weekly variations in Biochemical Oxygen Demand (BOD) of effluent treated using SSF ............................................................................................................. 57 Fig 23: Weekly variations in Chemical Oxygen Demand (COD) of effluent treated using SSF ...................................................................................................................... 58 Fig 24: Source of water for domestic use by respondents ................................................ 88 Fig 25: Proportion of respondents who consider water to be a scarce resource ............... 89 Fig 26: Causes of water scarcity stated by respondents .................................................... 89 Fig 27: Sources of wastewater stated by respondents ....................................................... 90 Fig 28: How wastewater is generated by respondents ...................................................... 90 Fig 29: Uses of wastewater generated at home ................................................................. 91 Fig 30: Type of toilet facilty respondents have access to ................................................. 92 Fig 31: Methods of disposal of sewage as stated by respondents ..................................... 93 Fig 32: Respondents reasons for supporting wastewater reuse ........................................ 94 Fig 33: Types of health risks associated with wastewater reuse as stated by respondents 95 Fig 34: Respondents response on how health risks can be minimized ............................. 96 xii Fig 35: Response of respondents to the use of treated wastewater for irrigation of food crops .................................................................................................................... 97 Fig 36: Response of respondents to the use of treated wastewater for fire fighting ......... 98 Fig 37: Response of respondents to the use of treated wastewater for industry ............... 98 Fig 38: Response of respondents to the use of treated wastewater for construction of buildings .............................................................................................................. 99 Fig 39: Response of respondents to the use of treated wastewater for swimming pool ... 99 Fig 40: Response of respondents to the use of trated wastewater for aquifer augmentation ........................................................................................................................... 100 xiii LIST OF TABLES Table 1: Quality of sewage effluent from intermediary chamber (A) and final outlet (B) of the Valley View University (VVU) Biogas facility. .................................... 42 Table 2: Phosphorus and nitrogen accumulation in Ipomoea aquatica and Pistia stratiotes at the end of experiment ................................................................................... 46 Table 3: Comparison of p H of effluent treated using SSF with effluent from treatment with Ipomoea aquatica ..................................................................................... 60 Table 4: Comparison of the concentration of dissolved oxygen (DO) of effluent treated using SSF with effluent treated with Ipomoea aquatica ................................. 61 Table 5: Comparison of turbidity of effluent treated using SSF with effluent from treatment with Ipomoea aquatica ..................................................................... 63 Table 6: Comparison of EC of effluent treated with SSF with effluent from treatment with Ipomoea aquatica ..................................................................................... 65 Table 7: Comparison of concentration Total Dissolved Solids (TDS) of effluent treated using SSF with effluent from treatment with Ipomoea aquatica ..................... 67 Table 8: Comparison of concentration of Total Suspended solids (TSS) of effluent treated using SSF with effluent from treatment with Ipomoea aquatica ..................... 69 Table 9: Comparison of colour of effluent treated using SSF with effluent from treatment with Ipomoea aquatica ..................................................................................... 71 Table 10: Comparison of concentration of nitrates in effluent treated using SSF with effluent treated using Ipomoea aquatica .......................................................... 73 Table 11: Comparison of phosphate concentration in effluent treated using SSF with effluent from treatment with Ipomoea aquatica ............................................... 75 Table 12: Comparison of Biochemical Oxygen Demand (BOD) of effluent treated with SSF with effluent from treatment with Ipomoea aquatica ............................... 77 xiv Table 13: Comparison of Chemical Oxygen Demand (COD) of effluent treated using SSF with effluent from treatment with Ipomoea aquatica ...................................... 79 Table 14: Microbiological characteristics of sewage effluent before and after treatment 80 Table 15: Comparison of the quality of effluent for ten weeks of SSF to quality of effluent passing through the filtration system of the VVU Biogas plant ......... 82 Table 16: Assessment of safety of effluent treated using SSF for disposal/reuse ............ 83 Table 17: Assessment of the quality of effluent treated using Pistia stratiotes for disposal/use ...................................................................................................... 84 Table 18: Assessment of the quality of effluent treated using Ipomoea aquatica for disposal/ use ..................................................................................................... 86 Table 19: Demographic characteristics of respondents .................................................... 87 xv CHAPTER ONE 1.0 INTRODUCTION AND LITERATURE REVIEW All around the world, the demand for water resources is accelerating with increasing population growth. Most water bodies are under threat due to pollution. It is becoming increasingly important to seek alternative sources of water to meet the demand of the ever increasing global population. Increasing demands on water resources for domestic, commercial, industrial and agricultural purposes have made wastewater reclamation an attractive option for conserving and extending available water supplies. Thus, wastewater reclamation and reuse have become essential components of water resource management plans throughout the world. One of the major water resource management concerns throughout the world is the safe disposal of sewage. In many countries especially the developing ones, disposal of raw untreated sewage into natural waters is a common practice. This poses a great hazard for the environment and a health risk for both human and animal life. In recent years, sewage treatment strategies have been shifted to one of the most promising methods i.e. biological anaerobic treatment. This method is capable of treating sewage to produce renewable energy (biogas), leaving behind an effluent which is usually discarded. This effluent is a substantial water resource that has to be sustainably managed, rather than discarded. Sewage effluent is composed of compounds of agricultural value including organic matter, nitrogen, phosphorus and a lesser amount of calcium, sulphur and magnesium. It may also contain pollutants such as heavy metals, organic pollutants and pathogens 1 which may have significant adverse effects on human health and the environment, thus limiting its use. However, further treatment of the effluent can produce a high quality effluent for use. Treatment technologies for wastewater need to be appropriate and sustainable. They should also be efficient but less costly and easy to operate and maintain. In developing countries with warm climates such as Ghana, natural systems are considered more suitable. Slow Sand filtration (SSF) and phytoremediation are natural treatment systems that can be used for treatment of wastewater. These technologies have proven to reduce contaminant levels to tolerable levels. Materials needed for the use of these technologies are readily available. Global water crises Fresh water is a scarce and unevenly distributed resource, not matching patterns of human development (Corcoran et. al., 2010). According to UNDESA (2009), nearly 900 million people worldwide still do not have access to safe water. The population of the world is increasing rapidly and is expected to grow by almost a third to over 9 billion people in the next 40 years (UNFPA, 2009), resulting in increased water usage. The African continent has the lowest total water supply coverage of any region in the world, with only 64% of the population having access to improved water supply (WHO, 2000). One other contributory factor to the water scarcity problem is water pollution. The available water resources which should cater for the needs of the ever growing global 2 population are constantly being polluted the chief sources of water pollution being sewage, industrial wastes, fossils, fuel and nuclear power plants (Egun, 2010). Currently, there is increasing awareness of the impact of sewage contamination on water bodies. According to the World Bank, the greatest challenge in the water and sanitation sector over the next two decades will be the implementation of low cost sewage treatment that will at the same time permit selective reuse of treated effluents for agricultural and industrial purposes (Jhansi and Mishra, 2012) Sewage treatment Wastewater (sewage) treatment is an expensive process, both in terms of land required and the energy consumed (Mekala et. al., 2008). More than 65% of sewage is treated in developed countries (WHO and UNICEF, 2000) for various reasons, but only after suitable treatment and guidelines are in place for recycling. In Africa, almost no sewerage is treated (WHO and UNICEF, 2000). Generally there is lack of sustainable options for treating sewage in many cities in developing countries. Most cities in developing countries have an aging, inadequate or even non-existent sewage infrastructure, unable to keep up with rising population. The United Nations Development Programme (UNDP) reports that in 2000 only 2 % of the cities in sub-Saharan Africa had sewage treatment and only 30 % of these were operating satisfactorily. The cities of Ghana are no exception to the poor sewage treatment coverage. It has been shown that out of the 44 wastewater treatment plants in Ghana, only 20 % are working, most of them below design standard (IMWI, 2012). Consequently, sewage sludge from 3 on-site sanitation systems (OSS) is collected and disposed-off in the raw and untreated form indiscriminately into drainage ditches, inland waters and coastal waters. Discharge of untreated effluent into water bodies puts at risk riparian communities which depend on these waters for domestic and personal use (Tchobanologous et al., 2003). Biodiversity is also affected as a result of water pollution. In many developing countries, contamination of faecal origin appears to be responsible for many enteric diseases notably in children. Africa has the worst statistics for cholera and child diarrhoea (Warner, 2000).WHO reported in 2000 that in Africa, 155 children die every hour of everyday from sanitation, hygiene and water related diseases. The number of cholera cases reported from Africa is increasing every year. A total of 187,545 cholera cases and 8,051 deaths were officially reported in the African Region (WHO, 2000). Recently, several cholera outbreaks were reported in different African countries: Zimbabwe, Tanzania, Rwanda, Kenya, Angola, Republic of Congo and Ghana due to contaminated drinking water (Bahri et al., 2012) Most of the current sewage treatment technologies in developing countries lack sustainability (Jhansi and Mishra, 2012). The conventional centralized system uses large volumes of water to dilute human excreta and thereafter transports them out of the settlement which makes this system unsustainable because apart from the fact that large volumes of water are lost, most of the sewage is transported and deposited in water bodies leading to contamination of the water causing public health hazards. There is also a loss of nutrient resources of agricultural value such as nitrogen and phosphorus. 4 Another reason for the unsustainable treatment systems in developing countries is that they are simply copied from western treatment systems without considering the appropriateness of the technology for the culture, land and climate. Thus, many of the implemented installations are abandoned due to high cost of running the system and repairs (Jhansi and Mishra, 2012). In order to achieve effective sewage treatment in developing countries, there is the need to apply appropriate treatment technologies which are effective, simple to operate and low cost in terms of investment, operation and maintenance. One of the effective treatment options for developing countries is anaerobic digestion (Jhansi and Mishra, 2012). This technology has been proven to have high treatment efficiency and its operation requires no or very low energy. Anaerobic digestion consists of several interdependent, complex sequential and parallel biological reactions in the absence of oxygen in which the products from one group of microorganisms serve as substrates for the next resulting in transformation of organic matter (Parawira, 2004). The products resulting from the transformation are biogas and nutrient rich effluent called digestate. In this system, anaerobic bacteria degrade organic materials in the absence of oxygen and produce methane and carbon dioxide. The methane can be reused as an alternative energy source or biogas. Other benefits include a reduction of total bio-solids volume of up to 50-80% and a final effluent that is biologically stable and can serve as rich humus for agriculture (Jhansi and Mishra, 2012). This anaerobic treatment technology can be 5 applied on a very small or a very large scale making it a sustainable option for a growing community. However, effluents from anaerobic reactors treating domestic sewage can rarely comply with the emission standards. Besides the remaining fraction of particulate and soluble organic matter, the main important constituents or components deserving attention are nutrients and pathogens. These are not removed efficiently in the most commonly used anaerobic reactors (Foresti, 2002). Wastewater reuse Current waste management practices propose that sanitation systems whenever feasible should allow for recycling of organic matter and nutrients in human excreta (Esrey et al., 1998). As a result, treatment strategies and technological options for sewage sludge and solid waste have to be developed to allow the optimum recycling of nutrients and organic matter. One of the important and sustainable ways to reduce the impact of water scarcity and pollution is wastewater recycling and reuse. Wastewater effluent is the most readily available and cheapest source of additional water and provides a partial solution to the water scarcity problem (Al-Dadah, 2013). In recent years, the reuse of treated effluent that hitherto was discharged into the environment from municipal wastewater treatment plants is receiving an increasing attention as a reliable water resource. In many countries, wastewater treatment for reuse is an important dimension of water resources planning and implementation. This is aimed 6 at releasing high quality water supplies for potable use. Some countries, such as Jordan and Saudi Arabia, have national policies aimed at reusing all treated wastewater effluents, thus have made considerable progress towards this end (Akpor and Muchie, 2011). In China, sewage use in agriculture developed rapidly several decades ago and millions of hectares are irrigated with sewage effluent (Akpor and Muchie, 2011). The general acceptance is that wastewater use in agriculture is justified on agronomic and economic grounds, although care must be taken to minimize adverse health and environmental impacts (Sowers, 2009). Furthermore, wastewater reuse is increasingly becoming important for supplementing drinking water needs in some countries around the world. The option of reuse of wastewater is becoming necessary and possible as a result of increased climate change, which leads to droughts and water scarcity, and the fact that wastewater effluent discharge regulations have become stricter leading to a better water quality (Rietveld et al., 2009). Wastewater can be an essential resource for supporting livelihoods with proper management. The treatment and reuse of wastewater in agriculture can provide benefits to farmers in conserving freshwater resources, improving the integrity of the soil and preventing discharge to surface and ground waters. In the State of California and in Mexico, reclaimed water is used for irrigation (Corcoran et. al., 2010). The use of raw untreated wastewater for irrigation is a common practice in Africa. Practices range from the use of polluted surface water/raw wastewater to the piped distribution of secondary or tertiary treated wastewater to irrigate different kinds of crops and trees (IWMI, 2006). Due to poor transportation systems, 70-90% of the most perishable vegetables consumed in many African cities such as Dakar, Bamako, 7 Ouagadougou, Accra, Addis Ababa and Nairobi are also grown within the city boundary, using highly polluted water sources, mostly of domestic origin (Drechsel et al., 2006). There are only a few countries in Africa namely South Africa, Tunisia and Namibia with experience in planned reuse and a record of wastewater treatment plants producing a safe effluent for irrigation. In most of the other countries, including Ghana partially treated or untreated urban wastewater is widely used to irrigate vegetables, rice and fodder for livestock. Wastewater irrigation, though a major economic contributor in terms of jobs and food supply can also be a major health risk for farmers and consumers Among the health risks of particular concern are endemic and epidemic diseases such as cholera and typhoid (WHO, 2006). Wastewater irrigation also raises issues related to environmental protection as its nutrient, salt and contaminant levels can be high. However, farmers do not have a choice to use “wastewater” or not, as it is often difficult to find clean water sources in and around most cities. Wastewater has many advantages for farmers as it contains significant amounts of nutrients for food crop production that reduce the need for chemical fertilizers. Organic matter, nitrogen, phosphorus, and potassium in wastewater may improve soil fertility, enhance plant development and increase agricultural productivity. More importantly, however, it is a reliable water supply, usually ‘free-of-charge’, and readily available. Wastewater reuse supports the livelihood of many farmers and traders and plays a significant role in poverty alleviation. It also provides a niche for urban food supply complementing rural production (Drechsel et al., 2007). 8 Other wastewater reuse options are landscape irrigation, industrial recycling and reuse, recreational/environmental uses, groundwater recharge, habitat wetlands, non-potable miscellaneous uses and augmentation of potable supplies (Hagare and Dharmappa, 1999). The reuse of wastewater for the above mentioned purposes can help to conserve water. Characteristics of wastewater Physico-chemical characteristics The composition of wastewater varies widely depending on the type of activity producing the wastewater. The physico-chemical characteristics of wastewater that are of special concern are pH, dissolved oxygen (DO), oxygen demand (chemical and biological), solids (suspended and dissolved), nitrogen (nitrite, nitrate and ammonia), phosphate, and metals (Larsdotter, 2006). The hydrogen-ion concentration is an important quality parameter of both natural and waste waters. It is used to describe the acid or base properties of wastewater. A pH less than 7 in wastewater effluent is an indication of septic conditions while values less than 5 and greater than 10 indicate the presence of industrial wastes. An indication of extreme pH is known to damage biological processes in biological treatment units (Gray, 2002). Another parameter that has significant effect on the characteristics of water is dissolved oxygen. It is required for the respiration of aerobic microorganisms. The actual quantity of oxygen that can be present in solution is determined by the solubility, temperature, 9 partial pressure of the atmosphere and the concentration of impurities such as salinity and suspended solids in the water (Metcalf and Eddy, 2003). Oxygen demand, which may be in the form of Biochemical Oxygen Demand (BOD) or Chemical Oxygen Demand (COD), is the amount of oxygen used by microorganisms as they feed upon the organic solids in wastewater (FAO, 2007). The five day BOD (BOD5) is the most widely used organic pollution parameter applied to wastewater. The presence of sufficient oxygen promotes the aerobic biological decomposition of an organic waste (Metcalf and Eddy, 2003). Although BOD test is widely used, it has a number of limitations, which include the requirement of a high concentration of active acclimated microorganisms and the need for treatment when dealing with toxic wastes, thus reducing the effects of nitrifying organisms. The BOD measures only the biodegradable organics and requires a relatively long time to obtain test results (Gray, 2002; Metcalf and Eddy, 2003) but the COD test measures the oxygen equivalent of the organic material in wastewater that can be oxidized chemically. The ratio of COD to BOD provides a useful guide to the proportion of organic material present in wastewaters, although some polysaccharides, such as cellulose, can only be degraded anaerobically and so will not be included in the BOD estimation (Metcalf and Eddy, 2003). The amount of solids in drinking water systems has significant effects on the total solids concentration in the raw sewage. In spite of this wastewater is normally 99.9 % water, 0.1 % of it is comprised of solids. Although there are different ways of classifying solids in wastewater, the most common types are total dissolved solids (TDS), total suspended solids (TSS), settleable, floatable and colloidal solids, and organic and inorganic solids. 10 Heavy metals are one of the most persistent pollutants in wastewater. Heavy and trace metals are also of importance in water. The metals of importance in wastewater treatment are As, Cd, Ca, Cr, Co, Cu, Fe, Pb, Mg, Mn, Hg, Mo, Ni, K, Se, Na, V and Zn. Living organisms require varying amounts of some of these metals (Ca, Co, Cr, Cu, Fe, K, Mg, Mn, Na, Ni and Zn) as nutrients (macro or micro) for proper growth. Other metals (Ag, Al, Cd, Au, Pb and Hg) have no biological role and hence are non-essential (Hussein et al., 2005). Heavy metals in wastewater is due to discharges from residential dwellings, groundwater infiltration, and industrial discharges. The accumulation of these metals in wastewater depends on many local factors, such as the type of industries in the region, way of life and awareness of the impact on the environment through the careless disposal of wastes (Hussein et al., 2005; Silvia et al., 2006). The danger of heavy and trace metal pollutants in water lies in two aspects of their impact. Firstly, heavy metals have the ability to persist in natural ecosystems for an extended period, and, secondly, they have the ability to accumulate in successive levels of the biological food chain. Although heavy metals are naturally present in small quantities in all aquatic environments, it is almost exclusively through human activities that these levels are increased to toxic levels (Nelson and Campbell, 1991). The methods for determining the concentrations of these metals vary in complexity according to the interfering substances that may be present. Typical methods of determining their concentrations include flame atomic absorption, atomic absorption spectrophotometry (AAS), inductively coupled plasma (ICP), and inductively coupled plasma (ICP)/ mass spectrometry (APHA, 2001). Surface waters contain levels of phosphorus in various compounds, which are essential constituents of living organisms. In natural conditions, the phosphorus concentration in 11 waters is balanced. However, when phosphorus input to waters is higher than that which a population of living organisms can assimilate, the problem of excess phosphorus content occurs (Rybicki, 1997). An excess content of phosphorus in receiving waters usually leads to extensive algal growth (eutrophication). Controlling phosphorus discharge from municipal and industrial wastewater treatment plants is a key factor in preventing eutrophication of surface waters (Department of Natural Science, 2006). The following groups of phosphorus compounds are of great importance in wastewater: organic phosphates, condensed phosphates and inorganic phosphates. Although phosphate itself does not have notable adverse health effects, phosphate levels greater than 10 mg/L may interfere with coagulation in water treatment plants (McCasland et al., 2008). Nitrogen is important in wastewater management. It can have adverse effects on the environment, since its discharge above the required limit of 10 mg/L can be undesirable due to its ecological and health impacts (Kurosu, 2001; Amir et al., 2004). Nitrogen is required by all organisms for the basic processes of life to make proteins, grow and reproduce. It is recycled continually by plants and animals. Most organisms cannot use nitrogen in the gaseous form (N) for their nutrition, so they are dependent on other organisms to convert it into other forms (Jenkins et al., 2003). Ammonia, nitrate and nitrite make up the inorganic forms of nitrogen (Hurse and Connor, 1999). Organic and inorganic forms of nitrogen may cause eutrophication problems in nitrogen-limited freshwater lakes and in estuarine and coastal waters. In the environment, ammonia is oxidized to nitrate, creating an oxygen demand and low dissolved oxygen in surface waters (Kurosu, 2001). Despite the fact that nitrate levels that affect infants do not pose a 12 direct threat to older children and adults, they indicate the presence of other serious residential or agricultural contaminants, such as bacteria and pesticides (McCasland et al., 2008). Methemoglobinemia is the most significant health problem associated with nitrate in water. Usually, blood contains an iron-based compound (hemoglobin) that carries oxygen, but when nitrite is present, hemoglobin can be converted to methemoglobin, which cannot carry oxygen. Similarly, nitrogen in the form of ammonia is toxic to fish and exerts an oxygen demand on receiving water by nitrifiers (CDC, 2002). Microbiological characteristics The major microorganisms found in wastewater are viruses, bacteria, fungi, protozoa and helminthes. Although various microorganisms in water are considered to be critical factors in contributing to numerous waterborne outbreaks, they play many beneficial roles in wastewater influents (Kris, 2007). Traditionally, microorganisms are used in the secondary treatment of wastewater to remove dissolved organic matter (Akpor and Muchie, 2011). Apart from solid matter reduction, wastewater microbes are also involved in nutrient recycling, such as phosphate, nitrogen and heavy metals. If nutrients that are trapped in dead materials are not broken down by microbes, they will never become available to help sustain the life of other organisms in the breakdown process. Microorganisms are also responsible for the detoxification of acid mine drainage and other toxins in wastewater (Ward-Paige et al., 2005). Microbial pollutants can also serve as indicators of water quality. The detection, isolation and identification of the different types of microbial pollutants in wastewater are always difficult, expensive and time consuming. To avoid this, indicator 13 organisms are always used to determine the relative risk of the possible presence of a particular pathogen in wastewater (Paillard et al., 2005). For instance, enteric bacteria, such as coliforms, Escherichia coli, and faecal streptococci are used as indicators of faecal contamination in water sources (Momba and Mfenyana, 2005). Wastewater treatment Wastewater treatment is an expensive process thus many of the underdeveloped and developing nations of Africa and Asia have not been able to treat their wastewater to appropriate levels and continue to use it in agriculture with deleterious long-term effects on soil, groundwater and human health. However, many of the water scarce cities in Europe, North America and Australia are able to treat their wastewater to appropriate levels and recycle it in industries, residential areas, urban gardens and sports lawns. While the lack of wastewater treatment to appropriate levels before use is a major problem in developing countries, the high cost of wastewater recycling is the major problem in developed countries (Mekala et. al., 2008) The growing concern over the impact of sewage contamination on water bodies and the increasing scarcity of water in the world along with rapid population increase in urban areas give reasons to consider appropriate technologies for the post treatment of anaerobic effluent in order to achieve the desired effluent quality and save receiving water bodies. Slow sand filtration (SSF) The use of slow sand filtration (SSF) to improve the quality of water dates back to hundreds of years (Bourdon et. al., 2012) and is a sustainable approach to purifying 14 water. It is a desirable technology in developing countries where water purification capabilities are poor and in developed countries with technically advanced water treatment plants. The use of SSF requires minimal use of chemicals, low electricity requirements and marginal operation and startup costs. Slow Sand Filtration operates by allowing untreated water to slowly percolate through a bed of porous sand, with the influent water source introduced over the top surface of the filter area, and effluent collected and drained from the bottom. The ability of SSF method to purify water is the result of several mechanisms that occur during filtration. It requires a continuous filtration of raw water through the sand bed. As the raw water filters through the sand grains, particles in the raw water are removed by transport and attachment processes such as adsorption and ion exchange. The most basic transport mechanism that occurs in SSF is the straining of particles out of the water by the sand grains. Straining occurs when the particles in the water larger than the voids in the sand grains become trapped and lodged in the sand bed. As more and more particles become lodged in the sand bed, the pore size between the sand gains and the particles decrease, allowing for a larger percentage of particles in the water to be removed. The majority of this screening process occurs at the surface of the filter. Sedimentation of the particles onto the sand grains is another transport mechanism. The settling action occurs as gravity forces the particles to move downward onto the top surfaces of the sand grains. Since the flow rate through SSF is gradual, the particles will remain settled on top of the sand grains and removed from the effluent of the SSF system. The sedimentation removal of the particles is enhanced by attachment processes. Once the particle has made contact with the sand grains, Van der Waals forces can help 15 maintain that particle on the sand grain. Another and stronger attachment mechanism is the adhesion of particles to the “schmutzdecke” layer or “dirt cover”. The “schmutzdecke” layer consists of the organic matter that settles on the filter surface and becomes the breeding ground for bacteria and microorganisms. As the “schmutzdecke” layer develops it becomes a sticky, gelatinous film and adheres a great deal of the particles from the raw water. The layer takes several weeks to form and can consist of bacteria, fungi, protozoa, algae, and microscopic aquatic organisms, once fully developed. The organic matter in the raw water is trapped by the “schmutzdecke” layer and utilized by the bacteria and microorganisms as a food source, thus reducing the organic matter into water, carbon dioxide, and inorganic salts. The “schmutzdecke” layer provides the primary means for eliminating organic matter in the slow sand filtered effluent. The transport and attachment processes in an established SSF have the ability to greatly improve the quality of the raw water. No other single process in typical drinking water treatment plants has the ability to improve the physical, chemical, and bacteriological quality of the raw water as an established Slow sand filter (Bourdon et. al, 2012). Phytoremediation Phytoremediation is defined as the efficient use of plants to remove, detoxify or immobilize environmental contaminants in a growth matrix (soil, water or sediments) through the natural, biological, chemical or physical activities and processes of plants (Peuke and Rennenberg, 2005). Phytoremediation techniques require very low costs to carry out (Jamil et. al., 2009). The method is widely recognized and accepted as an 16 ecologically responsible alternative to the environmentally destructive chemical remediation methods (Ahmadpour et. al., 2010). Aquatic macrophytes can effectively reduce total nitrogen, total phosphorus and chemical oxygen demand (Sooknah and Wilkie 2004). The principles of phytoremediation system are to clean up contaminated water which includes the identification and implementation of efficient aquatic plant, uptake of dissolved nutrients and metals by growing plants and the harvest and beneficial use of the plant biomass produced from the remediation system (Lu, 2010). The most important factor in implementing phytoremediation is the selection of an appropriate plant (Stefani et.al, 2011) which should have high uptake of both organic and inorganic pollutants and grow well in polluted water. The uptake and accumulation of pollutants vary from plant to plant and from species to species within a genus (Singh et. al., 2003). The economic success of phytoremediation largely depends on photosynthetic activity and growth rate of plants (Xia and Ma, 2006) and low to moderate amount of pollution (Jamuna and Noorjahan, 2009). Numerous aquatic plants have demonstrated considerable potential for nutrient removal from various types of wastewaters (Sooknah and Wilkie, 2004). Some of the aquatic plants used in the treatment of wastewater include Water hyacinth (Eichhornia crassipes), water lettuce (Pistia stratiotes), duckweed (Lemna sp.), Bulrush (Typha sp), Vetiver grass (Chrysopogon zizanioides) and common reed (Phragmites australis) (Piyush et. al., 2012). In this study, Ipomoea aquatica and Pistia stratiotes were used. 17 Water lettuce (Pistia stratiotes L) Pistia stratiotes L is a floating perennial commonly called water lettuce belonging to the family Araceae. It floats on the surface of water and its roots hang submerged beneath floating leaves (Dipu et. al., 2011). The leaves can be up to 14 cm long and have no stem. They are light green with parallel veins, wavy margins and are covered in short hairs which form basket-like structures and help in trapping air bubbles, increasing the buoyancy of the plants. The flowers are dioecious and are hidden in the middle of the plant among the leaves. The plant can reproduce both sexually and vegetatively (Dipu et. al., 2011). Water lettuce has a minimum growth at temperature 15°C (Kasselmann, 1995). Fonkou et.al., (2002) stated that the water lettuce doubles its biomass in just over five days, triples it in ten days, quadruples it in twenty days and has its original biomass multiplied by a factor of nine in less than one month. This indicates that the maximum period to allow the plant in the system is twenty five days (Piyush et. al., 2012). In the tropics, water lettuce is used in phytoremediation systems because compared to native plants; it shows higher nutrient removal efficiency with increased nutrient uptake capacity, fast growth rate and big biomass production (Reddy and Sutton, 1984). Water spinach (Ipomoea aquatica Forsk) Ipomoea aquatica is a semi-aquatic tropical plant grown as a leaf vegetable belonging to the family Convolvulaceae. It is a very good source of nutrients (Visitacion et. al., 2011) and acts as a good metal and toxin accumulator (Teerakun and Reungsang, 2005). 18 Public perception and acceptance of wastewater reuse A successful implementation of a wastewater reuse project is dependent not only on its economic and environmental feasibility but mainly on the support and acceptability of the general public that ultimately patronize and might be affected by the reuse project. Reuse schemes may face public opposition resulting from a combination of prejudiced beliefs, fear, attitudes, lack of knowledge and general distrust often resulting from the frequent failures of wastewater treatment facilities worldwide (Jeffrey and Temple, 1999). Results from several surveys on public attitudes toward wastewater reuse options have been published, the data collected mainly in the United States of America, Western Europe and Australia. Results of these surveys indicate that, a large majority of the public support water reuse as a concept and public support for reuse decreases as the degree of contact with the reclaimed water increases. Crook (2003) reported that in the US the public generally supports non-potable reuse while acceptance of potable reuse is problematic, with typically less than 50% support. . Much less information is available regarding the attitude toward the issue in other regions and under different environmental and climatic conditions (Friedler et. al., 2006) The primary concerns of the public are costs and public health protection, thus uses that result in financial gains and involve minimal degree of contact with the reclaimed water are favoured (Friedler et. al., 2006). 19 Objectives The main objective of this study was to assess performance efficiency of slow sand filtration and phytoremediation for effective secondary treatment of sewage effluent from a biogas plant The specific objectives were to: 1. characterize the sewage effluent after anaerobic digestion of sewage in the Biogas facility of Valley View University (VVU) 2. conduct phytoremediation using two macrophyte species namely Pistia statiotes and Ipomoea aquatica to identify the better macrophyte for the uptake of specific pollutants 3. conduct slow sand filtration of the raw effluent using river bed sand 4. compare the experimental slow sand filter to the filtration system of the biogas facility 5. evaluate and compare the performance of slow sand filtration and phytoremediation technologies in treating sewage effluent 6. assess the safety of the treated effluent for disposal and/or reuse 7. assess public perception of wastewater reuse 20 CHAPTER TWO MATERIALS AND METHODS 2.1 Study site The study site was the Valley View University (VVU) located at Oyibi in the greater Accra Region of Ghana. Fig 1: Location map of study area 21 2.2 Materials (i) Raw sewage effluent The raw sewage effluent was obtained from the Biogas facility of the Valley View University (VVU) (ii) Sand and gravels for Slow Sand Filtration (SSF) The river sand and gravels for the SSF experiment were obtained from the Volta River at Asutuare (iii) Aquatic macrophytes for phytoremediation were obtained from the Kpong Head Pond Plate 1: Kpong Head Pond showing aquatic plants 22 2.3 Sewage treatment at VVU The method of sewage treatment at VVU is anaerobic digestion. In this system, there is a digestor (Plate 2) where anaerobic bacteria degrade organic materials (in the absence of oxygen) and produce methane and carbon dioxide. The methane is stored and used in the school’s kitchen (for cooking). The effluent from the digestor is transported to an intermediary chamber (Plate 2). From this chamber, the effluent passes into a filtration system made of activated charcoal and then discharged into a mango plantation (Plate 3.1d) 2.4 Selection of sampling sites The sewage effluent was obtained from the Biogas facility of the Valley View University. Samples were taken from two points for analyses; the intermediary chamber and the final outlet (Plate 2). Effluent samples for sand filtration and phytoremediation were collected from the intermediary chamber (Plate 3.1) 2.5 Sampling of aquatic macrophytes Two aquatic macrophytes namely Pistia stratiotes L and Ipomoea aquatica Forsk were selected and identified. Pistia stratiotes is a floating species whilst Ipomoea aquatica is an emergent species. Fresh and healthy macrophytes were collected from the Kpong Head Pond and transported along with adequate quantity of water from the source (to prevent wilting) to the greenhouse at the Botany Department of the University of Ghana, Legon. 23 (a) Digestor (b) Filtration bed Intermediary chamber (c) Final outlet (d) Mango plantation Plate 2: Biogas facility of Valley View University 24 2.6 Preparation of filter media units Sand and gravels harvested from the Volta River at Asutuare were washed thoroughly using ordinary tap water to remove sediments, sun dried and sieved to obtain desired fractions. Below are the different fractions of sand and gravels used for the Slow Sand Filtration (SSF). a b c Plate 3: Filter media units; (a) gravels (5-10mm diameter), (b) coarse sand (2-3mm diameter), (c) fine sand (0.4mm diameter) 25 2.7 Treatment of sample containers The following measures were adhered to in avoiding possible contamination of samples during sampling. The sampling containers with well-fitted stoppers were pre-treated by washing with acetone to get rid of organic substances such as grease and fat residues. They were then washed with detergent and rinsed with de-ionised water and then soaked in 0.1 M nitric acid solution for 48 hours. The containers were finally rinsed several times with de-ionised water before used for taking and holding water samples. Water samples that were not analyzed immediately at the site were transported on ice to the laboratory where they were stored in a refrigerator below 4oC. Precautions were taken as to the number of days the samples should be stored to avoid inaccuracy. 2.8 Monitoring of effluent quality at sampling site Characterization of sewage effluent, both for the intermediary and final outlets was carried out twice a month over a period of four months (February 2014-May 2014). Reject water samples from the intermediary and final out-let points of the plant were taken for physico-chemical analyses. Parameters including temperature, pH, conductivity, colour, turbidity, biochemical oxygen demand (BOD), chemical oxygen demand (COD), total suspended solids (TSS), total dissolved solids (TDS), nitrate, phosphate and heavy metals like Pb, Cd, Cu, Ni, Zn, Fe, Cr were determined. Microbiological parameters such as total heterotrophic bacteria (THB), total coliform and faecal coliforms were also determined. 26 2.8 Sampling of effluent for characterization 2.8.1 Sampling for physico-chemical tests and field measurements Cleaned 500 ml plastic bottles were filled with effluent samples from the intermediary chamber and the final outlet. This was subsequently used in the laboratory for off-site analyses. pH, temperature, conductivity and dissolved oxygen of the effluents were measured in-situ. 2.8.2 Biochemical Oxygen Demand (BOD) and Dissolved Oxygen (DO) Sampling A plain bottle and one dark bottle (painted with bitumen to prevent possibility of photosynthetic production of oxygen) were used for sampling. The plain one was used for dissolved oxygen sampling and the dark bottles were used for BOD sampling. The bottles were filled with the waste water to overflow in order to avoid any air bubbles from getting trapped in the bottles. The dissolved oxygen samples were fixed on site with 2 ml each of Winkler 1 (Manganous chloride) and Winkler 2 (alkaline-iodide-azide reagent). Samples, which were not analyzed within 2 hours of collection, were kept at or below 4oC but brought to 20oC before analysis in the laboratory. 2.8.3 Trace Metals Sampling Water samples for analysis of the trace metals Iron, Cadmium, Copper Nickel, Zinc, Lead and Chromium, were collected in plastic vials and fixed on the field with nitric acid. They were then kept at or below 4oC but brought to 20oC before analysis in the laboratory. 27 2.8.4 Bacteriological sampling Glass bottles of 500 ml capacity with metal caps were used to collect the effluents at the intermediary and final outlets. The bottles were sterilized before use and the mouths covered with aluminium foil to avoid contamination during sample collection. The samples were stored on ice at 4ºC and transported to the laboratory for analyses. Plate 4: Sampling effluent from intermediary chamber for characterization 2.9 Sewage effluent collection and experimental procedure 2.9.1 Sewage effluent collection Sewage effluent for the experiment was collected from the intermediary chamber of the VVU Biogas facility. The effluent was collected into 40 L plastic gallons and transported to the greenhouse at the Botany Department of the University of Ghana. 28 2.9.2 Slow Sand filtration (SSF) 2.9.2.1 Preparation of filter media Three plastic buckets each of 100 cm height and 100 L capacity were prepared, each with a tap fitted at the bottom to allow filtered effluent to be drained out. Two of the buckets were used to filter the raw sewage effluent and the third was used as a control. Each bucket was filled with gravel of 5-10 cm diameter at the bottom, coarse river sand of 2-3 mm diameter as mid layer each of 10 cm depth and fine river sand of 0.4 mm diameter at 40 cm depth. A diffusion plate was placed 10 cm above the fine sand to allow even distribution of the raw sewage effluent on the surface of the fine sand. Plate 5: Slow Sand Filtration experimental set up at the greenhouse 29 Diffusion plate Fine sand (0.4mm) 40cm 10cm Coarse sand (2 – 3mm) m Gravels (2 – 5mm) 10cm Fig 2: Cross-section of slow sand filter media for Slow Sand Filtration of effluent 30 2.9.2.2 Procedure for slow sand filtration of raw effluent Effluent was carefully poured from a bucket and allowed to percolate through the filter media. A water column of about 10 cm height was maintained above the sand to provide the needed pressure force to move the water through the sand bed system. The procedure was repeated for the control using distilled water. The rate of filtration through the filter media was determined weekly by measuring the volume of effluent per minute. Filtration was done once every week for ten weeks. Effluent samples and water for the control were analyzed for their various physico- chemical and microbiological characteristics before sand filtration and filtered effluents were also analyzed on a weekly basis for ten weeks using standard methods 2.10 Phytoremediation 2.10.1 Layout of the experiment The design of the experiment was a completely randomized. Two different macrophytes, namely Ipomoea aquatica and Pistia stratiotes were used. These plants were selected because they are readily available.There were two replicates each and one control unit using distilled water. Trial experiments were conducted to ascertain the performance of the plants in the sewage effluent. Two bowls of 40 L capacities were each filled with sewage effluent and the ten each of the plants, previously rinsed with tap water were planted in the bowls. In each bowl, twenty each of the individual plants were planted. Plant growth was observed. 31 For the actual experimental set up, Pistia stratiotes and Ipomoea aquatica plants collected from the Kpong Head Pond were rinsed and transferred into a large bowl containing tap water. Samples of the whole plants were oven dried at 105°C for 10 hours, ground into powder, digested and analyzed for the nutrient content. For each of the plants, two plastic bowls were each filled with sewage effluent to a height of 16 cm and kept outside in the open air. A third bowl was filled with distilled water to serve as a control. Each plant was then put in the bowls and one week was allowed for the plants to acclimatize to their new environment. It was observed during the first week that the Pistia stratiotes showed signs of wilting after the fifth day. Therefore, water samples from effluent treated with Ipomoea aquatica and Pistia stratiotes were taken after the fifth day for analyses. Starting from the second week, samples of water from effluent treated with Ipomoea aquatica were collected on a weekly basis for four weeks and analyzed for the physico-chemical and microbiological characteristics. At the end of the experimental period (five days for Pistia stratiotes and four weeks for Ipomoea aquatica), samples of the whole plant were taken from each bowl, oven dried, ground into powder, digested and analyzed to determine the nutrient and heavy metal content. Dilutions of the effluent (50% and 75%) were also prepared for planting Pistia stratiotes. This was done to determine whether Pistia stratiotes would survive for more than five days in the diluted effluent. The experiment was conducted in open air under natural daylight regime. 32 A B C Plate 6: Pistia stratiotes in different dilutions of effluent A- Pistia stratiotes in 50% dilution of effluent, B- Pistia stratiotes in 75% dilution of effluent, C- Pistia stratiotes in distilled water (control) Plate 7: Ipomoea aquatica planted in sewage effluent 33 2.11 Laboratory analyses Physico-chemical analyses were carried out at the Ecological Laboratory of the University of Ghana. Bacteriological analyses for Total coliforms, Total Heterotrophic Bacteria (THB) and faecal coliforms were undertaken at the Microbiological Laboratory at the Soil Science Department of the University of Ghana. The physico-chemical parameters determined included pH , temperature, conductivity, turbidity, dissolved oxygen (DO), biochemical oxygen demand (BOD), chemical oxygen demand (COD), total suspended solids (TSS), total dissolved solids (TDS), colour, phosphate and nitrate. 2.11.1 Physico-chemical analyses of raw and treated effluents The physico-chemical parameters were determined according to procedures outlined in the Standard Methods for the Examination of Water and Wastewater. At the sampling site, the effluent was collected into a plastic bucket for in-situ measurements. Temperature, pH and conductivity were measured using a digital meter (Model YSI 63), turbidity was measured using turbidimeter (Model HACH 2100P) NTU and Total Dissolved Solids (TDS) was measured with a portable digital TDS meter (Model HI 99301). 2.11.2 Total Suspended Solids Analysis The photometric (non-filterable residue) method was used. Five hundred millilitres of sample was blended at high speed for two minutes. This was poured into a 600 ml beaker. The sample was stirred and 25 ml immediately poured into a sample cell. The stored programme number for suspended solids, 630, was set to a wavelength of 810 nm. A 34 sample cell filled with 25 ml distilled water served as blank. This was placed into the cell holder and standardized. The sample was placed into the cell holder and the reading taken in mg/l suspended solids. 2.11.3 Heavy Metal Analysis The Atomic Absorption Spectrometry (AAS) method for heavy metals was used to determine the level of each heavy metal in the sample. The heavy metals whose concentrations were determined included: Cadmium (Cd), Copper (Cu), Nickel (Ni), Zinc (Zn), Lead (Pb), Iron (Fe) and Chromium (Cr). In flame atomic absorption spectrometry, a sample is aspirated into a flame and atomized. A light beam is directed through the flame, into a monochromator, and onto a detector that measures the amount of light absorbed by the atomized element in the flame. For some metals, atomic absorption exhibits superior sensitivity over flame emission. Because each metal has its own characteristic absorption wavelength, a source lamp composed of that element is used; this makes the method relatively free from spectral or radiation interferences. The amount of energy at the characteristic wavelength absorbed in the flame is proportional to the concentration of ion in the sample over a limited concentration range. 35 2.11.4 Dissolved Oxygen (DO) The azide modification of the Winkler method was used for this test. Two milliliter conc. H2SO4 was added to the samples which had already been fixed on the field with 2 ml each of Winkler 1 (Manganous chloride) and Winkler 2 (alkaline-iodide-azide reagent). One hundred milliliters of the sample was titrated with 0.025 M Na2S2O3 to a pale straw colour. Two milliliters of starch solution was added and titration was continued to first disappearance of blue colour. Calculation: For titration of a 100 ml sample, mg/l mg/l O2 = Vol. of M/80 thiosulphate used x 101.6 Vol. of sample used 2.11.5 Biological Oxygen Demand (BOD) The 5-day BOD test was used. Biochemical Oxygen Demand, or BOD, measures the amount of oxygen consumed by microorganisms in decomposing organic matter in stream water. BOD also measures the chemical oxidation of inorganic matter (i.e. the extraction of oxygen from water via chemical reaction). A test is used to measure the amount of oxygen consumed by these organisms during a specific period of time (usually 5 days at 20oC).This method consists of filling with sample an airtight bottle of the specific size and incubating it at the specific temperature for 5 days. Dissolved oxygen was measured initially and after incubation, and the BOD was computed from the difference between the initial and the final DO. In cases of dilution due to less amount of oxygen, BOD was computed from the formula below: 36 Calculation: BOD5 mg/l = D1 – D2 P Where; D1 = DO of diluted sample immediately after preparation, mg/l D2 = DO of diluted sample after 5 day incubation at 20 0C, mg/l P = Decimal Volumetric fraction of sample used. 2.11.6 Nitrogen-Nitrate (NO -3 -N) Analysis The Cadmium Reduction Method using Powder Pillows was used for the determination of nitrogen nitrate. The nitrate level in each sample was measured using Nitrate Powder Pillows in a direct reading Hach Spectrophotometer (Model DR 2000). Twenty five (25) ml of the sample was measured into sample cell of the spectrophotometer. One Nitraver 5 Nitrate Reagent Powder Pillow was added to the sample. The mixture was then shaken vigorously for 1 minute. Five minutes was allowed for the solution to react. An orange colour of the mixture indicates the presence of nitrate. After five minutes, another cell was filled with 25 ml of only the sample (blank). The blank sample was placed in the Spectrophotometer for calibration. The prepared sample was placed into the cell holder to determine the nitrate concentration at 500 nm in mg/l . 2.11.7 Phosphate (PO 3-4 ) Analysis A 25 ml of the prepared water sample was placed in the sample cell. PhosVer 3 Phosphate Powder Pillow was added to the cell content and swirled immediately to mix. 37 A two-minute reaction period was allowed. A blue colouration of the mixture indicates the presence of phosphate. Another sample cell (the blank) was filled with 25 ml of sample and placed into the cell holder to calibrate it. After reaction period, the prepared sample was placed into the cell holder and the level of phosphorus was determined at 890 nm. 2.11.8 Chemical Oxygen Demand (COD) A sample of sewage effluent (50 ml) was pipetted into a 500 ml refluxing flask. One gram of mercuric sulphate was added to the sample and several glass beads were added to the solution. Very slowly, 5 ml of sulphuric acid reagent was added and the flask was swirled while adding the reagent to help dissolve the mercuric sulphate. Twenty five millilitres of 0.250 N potassium dichromate solution was added and mixed. Distilled water was used as the blank.The sample flask and blank flask were refluxed after which the sample and blank were titrated with ferrous ammonium sulphate using ferroin indicator. The COD was calculated using the following formula: COD mg/l = (A-B) ×M×8,000 Volumeof sample, ml Where: A=ml of titrant used for sample B= ml of titrant used for blank M=normality of ferrous ammonium sulphate 38 2.11.10 Analyses of Bacteriological Parameters of raw and treated effluents Bacteriological analyses involved the determination of total Heterotrophic Bacteria (THB), Total Coliforms and Faecal Coliforms by the membrane filtration method. These parameters were determined only for the raw effluent and for the effluents at the end of the experiment. 2.11.10.1 Preparation of bacteriological media for bacteriological analyses of raw and treated effluents Preparation of Hicrome coliform agar Hicrome coliform agar was used. It is a selected medium recommended for the simultaneous detection of faecal coliforms and total coliforms in water and food samples. Twenty eight grams (28 g) of the powder was weighed and dissolved in 1 litre of deionized water. It was swirled to mix, sterilized by autoclaving for 15 min at 121ºC, cooled to 47ºC and poured into petri dishes. Preparation of nutrient agar Twenty eight grams of the dehydrated nutrient agar powder was weighed and dispensed in 1 litre of deionized water. The solution was allowed to soak for 10 min and sterilized by autoclaving for 15 min at 121ºC. It was allowed to cool to 47ºC and stored in the refrigerator. 39 Membrane Filtration Method The filter holding assembly constructed of stainless steel and consisted of a seamless funnel fastened to a base by a locking device. The design permitted the membrane filter to be held securely on the porous plate of the receptacle without mechanical damage and allowed all fluid to pass through the membrane during the filtration process. Firstly, the receptacle was sterilized with 96% alcohol, flamed and allowed to cool. A membrane filter of pore size 0.45 µm was gently placed on it and a filter funnel fitted unto it. Twenty millilitres (20 ml) of the effluent samples were diluted with distilled water, poured unto the funnel and extracted through a side tube, such that pressure could be exerted on the membrane filter. The filter was picked gently using sterilized forceps and placed in a petri dish containing sterilized Hicrome Coliform agar for the enumeration of total coliforms and faecal coliforms. Another filter was placed on nutrient agar for the enumeration of total heterotrophic bacteria. After incubation on Hicrome Coliform Agar for 24 hours at 35ºC to 37ºC, faecal coliforms appeared dark violet. Other colonies were counted for total heterotrophic bacteria. The Total and Faecal coliform present in water samples were determined using the Membrane Filter (MF) technique. Membrane filter with 0.45 µm pore size was sterilized in a system and used to filter 100 ml of water mixed with 10 ml of the sampled water. The results obtained from the colony counting were then multiplied by 10 to obtain the actual count per 100 ml for faecal and total coliforms M-Lauryl sulphate broth (LSB) was used as growth medium for the incubation of coliforms in a petri dish. Two milliliters of the broth was poured on an absorptive pad placed in a small Petri dish. The petri dish was then covered and inverted into ELE 40 paqualab incubator (model 50) for incubation at 37oC for total coliform and 44oC for faecal coliform. After 24 hours, the Petri dishes were removed from the incubator and the colonies counted and recorded in coliform forming units per 100 ml (cfu/100 ml) 2.12 Social survey Questionnaire Administration Questionnaires were administered to 120 randomly selected respondents. One hundred and twenty respondents from among students and staff of the Valley View University were selected due to the limited time for the study. During the time of the study, the University was on vacation so there were few people on the University campus and this accounted for the few number of respondents. One hundred and two questionnaires were returned and the data was coded and analysed using SPSS version 20. 2.13 Statistical analyses All data generated were double entered and cross checked for anomalies. The data was transferred into SPSS version 20. Comparison of phytoremediation and Slow Sand Filtration technologies was done using one-way ANOVA. The mean and percentage increase/ reduction were calculated for each parameter using Microsoft Excel. The questionnaires were analyzed using Statistical Package for Social Science (SPSS) version 20. 41 CHAPTER THREE 3.0 RESULTS The results of the study are shown below 3.1 Quality of sewage effluent from VVU biogas facility Table 1: Quality of sewage effluent from intermediary chamber (A) and final outlet (B) of the Valley View University (VVU) Biogas facility. Parameters analysed A B p H 3.9-4.14 6.47-7.48 Temperature (°C) 29.2-32.4 25.2-30.3 Electrical conductivity (µs/cm) 5017-5420 3216-3603 Total dissolved solids (mg/l) 2508.5-2710 1608-1801.5 Total suspended solids (mg/l) 322-368 56-75 Colour (PtCo) 699-792 487-543 Phosphates (mg/l) 4.3-6.4 0.44-5.6 Nitrates (mg/l) 1.7-4.2 1.8-9.7 Dissolved oxygen (mg/l) 0.11-0.6 2.98-5.4 Biochemical Oxygen Demand (mg/l) 29-40 17-35 Chemical Oxygen Demand (mg/l) 224-368 64-132 Turbidity (NTU) 121-201 42-53 Zinc ND ND Lead ND ND Copper 0.11 0.11 Iron 0.413 0.231 Cadmium ND ND Nickel ND ND Chromium ND ND Total heterotrophic bacteria (CFU/ml) 1210 1124 Total coliforms (CFU/100ml) 348 322 Faecal coliforms(CFU/100ml) 162 101 *ND: Non Detectable; A- raw effluent from intermediary chamber; B- effluent from final outlet The table 1 above presents detailed results of the quality of effluent from the intermediary chamber (A) and final outlet (B) of the Valley View University Biogas facility 42 3.2 Phytoremediation using Pistia stratiotes and Ipomoea aquatica Plant growth in raw sewage effluent (A) (B) (C) Plate 8: Condition of Pistia stratiotes days after planting in sewage effluent A above represents fresh and healthy Pistia stratiotes planted in the raw sewage effluent on the first day. Three days after planting, the plants had started wilting as shown in B and after the fifth day all the plants had wilted (C). A B C D Plate 9: Condition of Ipomoea aquatica days after planting in sewage effluent 43 A above shows Ipomoea aquatica plants on the first day of planting in the raw sewage effluent. By the third day (B), new shoots had started coming out. C and D show the growth of the plants on the fifth and fourteen days respectively. A B Plate 10: Sewage effluent before (A) and after treatment (B) with Pistia stratiotes A above is the raw sewage effluent before phytoremediation. It can be seen that some level of treatment occurred after phytoremediation with Pistia stratiotes. The treated effluent (B) looks clearer and less turbid than the raw effluent (A). 44 b a Plate 11: Sewage effluent before (a) and after treatment (b) with Ipomoea aquatica Comparing the effluent before and after treatment with Ipomoea aquatica, it can be seen that, some purification has taken place. The treated effluent looks clearer than the raw effluent. 45 3.3 Nitrogen and phosphorus uptake by plants Table 2: Phosphorus and nitrogen accumulation in Ipomoea aquatica and Pistia stratiotes at the end of experiment Total nitrogen (%) Total phosphorus (%) P.S I.A P.S I.A Before the experiment 2.996 2.604 0.92 0.77 After the experiment 3.332 3.892 1.17 1.19 Percentage increase (%) 10.08 33.09 21.37 35.29 *P.S – Pistia stratiotes I.A – Ipomoea aquatica The table above show the nitrogen and phosphorus content of Ipomoea aquatica and Pistia stratiotes before and after the phytoremediation experiment. The results show that both plants took up nitrogen and phosphorus. Ipomoea aquatica took up more nitrogen and phosphorus than Pistia stratiotes. 46 3.4 Contaminant removal efficiency of Ipomoea aquatica and Pistia stratiotes 18 16 14 12 10 8 6 4 2 0 Pistia stratiotes Ipomoea aquatica Aquatic macrophyte Fig 3: Phosphate removal efficiency of Ipomoea aquatica and Pistia stratiotes 120 100 80 60 40 20 0 Pistia stratiotes Ipomoea aquatica Aquatic macrophyte Fig 4: Nitrate removal efficiency of Ipomoea aquatica and Pistia stratiotes 47 Nitrate removal efficiency (%) Phosphate Removal efficiency (%) 60 50 40 30 20 10 0 Pistia stratiotes Ipomoea aquatica Aquatic macrophyte Fig 5: COD removal efficiency of Ipomoea aquatica and Pistia stratiotes 60 50 40 30 20 10 0 Pistia stratiotes Ipomoea aquatica Aquatic macrophyte Fig 6: EC removal efficiency of Ipomoea aquatica and Pistia stratiotes 48 EC removal efficiency (%) COD removal efficiency (%) The figures 3,4,5, and 6 show that both plants were effective at reducing contaminant levels. However, Ipomoea aquatica reduced phosphate (16.07%), nitrates (100%) and COD (47.8%) to lower levels whilst Pistia stratiotes reduced electrical conductivity (EC) to lower levels (55.45%) (Fig 6) than did Ipomoea aquatica. 3.5 Weekly variations in water quality parameters after treatment with Ipomoea aquatica 4.5 4 3.5 3 2.5 2 1.5 1 0.5 0 1 2 3 4 5 Duration of experiment (week) Fig 7: Concentration of dissolved oxygen (DO) in effluent after every week of treatment with Ipomoea aquatica 49 DO (mg/l) 40 35 30 25 20 15 10 5 0 1 2 3 4 5 Duration of study (week) Fig 8: Biochemical Oxygen Demand (BOD) of effluent after every week of treatment with Ipomoea aquatica 400 350 300 250 200 150 100 50 0 1 2 3 4 5 Duration of experiment (week) Fig 9: Chemical Oxygen Demand (COD) of effluent after every week of treatment with Ipomoeaaquatica 50 BOD (mg/l) COD (mg/l) 6000 5000 4000 3000 2000 1000 0 1 2 3 4 5 Duration of experiment (week) Fig 10: Electrical conductivity (EC) of effluent after every week of treatment with Ipomoea aquatica 3000 2500 2000 1500 1000 500 0 1 2 3 4 5 Duration of experiment (week) Fig 11: Total Dissolved Solids (TDS) of effluent after every week of treatment with Ipomoea aquatica 51 TDS (mg/l) EC (µs/Cm) 10 8 6 4 2 0 1 2 3 4 5 Duration of experiment (week) Fig 12: Concentration of phosphates in effluent after every week of treatment with Ipomoea aquatica 40 35 30 25 20 15 10 5 0 1 2 3 4 5 Duration of experiment (week) Fig 13: Concentration of nitrates in effluent after every week of treatment with Ipomoea aquatica 52 NO3 (mg/l) PO4 (mg/l) 3.6 Performance of Slow Sand Filtration Fig 14 below shows a decreasing rate of filtration of the raw effluent through the experimental sand filter. Figures 15, 16, 17, 18, 22 and 23 show a decreasing trend in turbidity, electrical conductivity (EC), total dissolved solids (TDS), total suspended solids (TSS), Biochemical Oxygen Demand (BOD) and Chemical Oxygen Demand (COD) respectively. The concentration of nitrates (Fig 19) decreased after first week and increased from the second to fifth week after which it decreased till the tenth week. Phosphate concentration (Fig 20) decreased from start of the experiment to the fourth week after which it increased from the fifth to sixth week and decreased again from the seventh to tenth week. Fig 21 shows an increase in dissolved oxygen (DO) after the first week. It decreased after the second to the seventh week and then increased again to the end of the experiment. 800 700 600 500 400 300 200 100 0 1 2 3 4 5 6 7 8 9 10 11 Time (week) Fig 14: Rate of filtration through experimental sand filter 53 Filtration rate (ml/min) 180 160 140 120 100 80 60 40 20 0 1 2 3 4 5 6 7 8 9 10 11 Time (week) Fig 15: Weekly variations in turbidity of effluent treated using SSF method 6000 5000 4000 3000 2000 1000 0 1 2 3 4 5 6 7 8 9 10 11 Time (week) Fig 16: Weekly variations in electrical conductivity (EC) of effluent treated using SSF 54 TURBIDITY (NTU) EC (µs/CM) 3000 2500 2000 1500 1000 500 0 1 2 3 4 5 6 7 8 9 10 11 Time (week) Fig 17: Weekly variations in concentration of total dissolved solids (TDS) in effluent treated using SSF 12 10 8 6 4 2 0 1 2 3 4 5 6 7 8 9 10 11 Time (week) Fig 18: Weekly variations in concentration of Total Suspended Solids (TSS) in effluent treated using SSF 55 TDS (mg/l) nitrates (mg/l) 6 5 4 3 2 1 0 1 2 3 4 5 6 7 8 9 10 11 Time (week) Fig 19: Weekly variations in concentration of nitrates in effluent treated using SSF 250 200 150 100 50 0 1 2 3 4 5 6 7 8 9 10 11 Time (week) Fig 20: Weekly variations in concentration of phosphates in effluent treated using SSF 56 Phosphates (mg/l) TSS (mg/l) 7 6 5 4 3 2 1 0 1 2 3 4 5 6 7 8 9 10 11 Time (week) Fig 21: Weekly variations in concentration of dissolved oxygen in effluent treated using SSF 40 35 30 25 20 15 10 5 0 1 2 3 4 5 6 7 8 9 10 11 Time (week) Fig 22: Weekly variations in Biochemical Oxygen Demand (BOD) of effluent treated using SSF 57 BOD (mg/l) DO (mg/l) 400 350 300 250 200 150 100 50 0 1 2 3 4 5 6 7 8 9 10 11 Time (week) Fig 23: Weekly variations in Chemical Oxygen Demand (COD) of effluent treated using SSF A B Plate 12: Sewage effluent before (A) and after seventh week (B) of slow sand filtration 58 COD (mg/l) It can be clearly seen that the effluent has been purified to a great extent. The treated effluent looks clearer than the raw effluent (A). 3.7 Comparison of phytoremediation using Ipomoea aquatica and slow sand filtration (SSF) technologies One-way analysis of variance was employed in testing the hypotheses assuming normal distribution with equal variance: Ho: mus=mui=musc=muic. H1: The mean values are all not the same. 59 Table 3: Comparison of p H of effluent treated using SSF with effluent from treatment with Ipomoea aquatica Ph Week SSF Ipomoea Scontrol Icontrol aquatica 0 4.130 4.14 7.32 7.72 1 6.540 7.38 6.91 6.45 2 6.515 7.22 6.63 6.06 3 7.585 7.77 6.80 6.75 4 7.165 7.65 7.10 7.19 PH ANOVA Sum of Source DF Squares Mean Square F Value Pr> F Model 3 0.93173375 0.31057792 0.27 0.8457 Error 16 18.37221000 1.14826312 Corrected Total 19 19.30394375 R-Square CoeffVar Root MSE Water Mean 0.048266 15.87218 1.071570 6.751250 Source DF Anova SS Mean Square F Value Pr> F Group 3 0.93173375 0.31057792 0.27 0.8457 The ANOVA for the pH table shows that the means of all the water treatment methods are the same. Therefore, it does not matter which water treatment method is employed they will both yield the same results since we fail to reject the null hypothesis. The Scheffe's Test and Student-Newman-Keuls Test also show that the means of the water treatment method on pH are all not significantly different. This implies that both treatment methods are effective at changing acidic conditions to neutral. 60 Table 4: Comparison of the concentration of dissolved oxygen (DO) of effluent treated using SSF with effluent treated with Ipomoea aquatica DO (mg/l) Week SSF Ipomoea Scontrol Icontrol Aquatica 0 1.935 0.17 6.0 6.3 1 6.100 2.10 5.5 4.3 2 5.100 3.50 4.6 4.8 3 4.250 1.90 5.3 5.5 4 3.700 4.10 4.5 6.7 DO (mg/l) ANOVA The ANOVA Procedure Dependent Variable: Water Sum of Source DF Squares Mean Square F Value Pr> F Model 3 30.27672375 10.09224125 6.51 0.0044 Error 16 24.79960000 1.54997500 Corrected Total 19 55.07632375 R-Square CoeffVar Root MSE Water Mean 0.549723 28.83400 1.244980 4.317750 Source DF Anova SS Mean Square F Value Pr> F Group 3 30.27672375 10.09224125 6.51 0.0044 Student-Newman-Keuls Test for Water NOTE: This test controls the Type I experiment wise error rate under the complete null hypothesis but not under partial null hypotheses. Alpha 0.05 Error Degrees of Freedom 16 Error Mean Square 1.549975 Number of Means 2 3 4 Critical Range 1.6692018 2.0317383 2.2527514 Means with the same letter are not significantly different. SNK Grouping Mean N Group A 5.5200 5 ic A A 5.1800 5 sc A A 4.2170 5 s B 2.3540 5 i Since the p value (0.0044) of the F calculated from the DO ANOVA is less than the significant level (0.05), there is enough evidence against the null hypothesis and it can be 61 concluded that the means are all not the same. The analysis shows that the water treatment methods on DO (mg/l) are not the same. Therefore, Multiple Comparisons or Post Hoc analysis was performed since the means are not the same. The Scheffe's Test and Student-Newman-Keuls Test revealed that the treatment with Ipomoea aquatica was the best in this case since it has the higher mean for DO (mg/l). Water with a higher DO concentration is evident of lower contamination by aerobic microorganism and therefore more desirable. 62 Table 5: Comparison of turbidity of effluent treated using SSF with effluent from treatment with Ipomoea aquatica TURBIDITY (NTU) Week SSF Ipomoea Scontrol Icontrol Aquatica 0 159.50 143.0 0.8 4.00 1 119.00 147.0 1.1 2.18 2 12.50 20.2 1.0 5.40 3 10.95 54.0 1.0 1.80 4 9.75 12.9 1.0 6.30 Turbidity ANOVA Sum of Source DF Squares Mean Square F Value Pr> F Model 3 22508.97126 7502.99042 3.19 0.0523 Error 16 37664.08492 2354.00531 Corrected Total 19 60173.05618 R-Square CoeffVar Root MSE Water Mean 0.374071 136.0231 48.51809 35.66900 Source DF Ano va SS Mean Square F Value Pr> F Group 3 22508.97126 7502.99042 3.19 0.0523 Scheffe's Test for Water Treatment NOTE: This test controls the Type I experiment wise error rate. Alpha 0.05 Error Degrees of Freedom 16 Error Mean Square 2354.005 Critical Value of F 3.23887 Minimum Significant Difference 95.651 Means with the same letter are not significantly different. Scheffe’s Grouping Mean N Group A 75.42 5 i A A 62.34 5 s A A 3.94 5 ic A A 0.98 5 sc 63 The analysis of the turbidity data shows that there is no evidence against the null hypothesis since the p-value (0.0523) is greater than the significant level (0.05). Hence, we fail to reject the null hypothesis and conclude that all the means of the treatment methods are the same. Post hoc analysis also confirms this assertion. This implies turbidity of the water would not be significantly different irrespective of the treatment method used. 64 Table 6: Comparison of EC of effluent treated with SSF with effluent from treatment with Ipomoea aquatica EC (µs/CM) Week SSF Ipomoea Scontrol Icontrol Aquatica 0 5413.5 5365 347 309 1 3755.0 3122 345 287 2 3398.0 3105 326 276 3 2859.0 3075 355 255 4 2813.0 2030 352 231 EC (us/CM) ANOVA Sum of Source DF Squares Mean Square F Value Pr> F Model 3 50980178.94 16993392.98 25.88 <.0001 Error 16 10504475.20 656529.70 Corrected Total 19 61484654.14 R-Square CoeffVar Root MSE Water Mean 0.829153 42.62479 810.2652 1900.925 Source DF Anova SS Mean Square F Value Pr> F Group 3 50980178.94 16993392.98 25.88 <.0001 EC (us/CM) ANOVA The ANOVA Procedure Student-Newman-Keuls Test NOTE: This test controls the Type I experiment wise error rate under the complete null hypothesis but not under partial null hypotheses. Alpha 0.05 Error Degrees of Freedom 16 Error Mean Square 656529.7 Number of Means 2 3 4 Critical Range 1086.3598 1322.308 1466.149 Means with the same letter are not significantly different. SNK Grouping Mean N Group A 3647.7 5 s A A 3339.4 5 i B 345.0 5 sc B B 271.6 5 ic The EC (mg/l) data shows enough evidence that the means are all not the same since the p-value (0.0001) of the calculated F value is less than the significant level (0.05). In view 65 of this, Post Hoc analysis was conducted to ascertain how different they are. From the Student-Newman-Keuls Test, sand filtration method of water treatment is not significantly different from that of treatment with Ipomoea aquatica. However, since the mean of the sand filtration method on EC (mg/l) is higher than that of Ipomoea aquatica, it follows that phytoremediation with Ipomoea aquatica is better in this case than the sand filtration. 66 Table 7: Comparison of concentration Total Dissolved Solids (TDS) of effluent treated using SSF with effluent from treatment with Ipomoea aquatica TDS (mg/l) Week SSF Ipomoea Scontrol Icontrol Aquatica 0 2706.75 2683.0 173.5 154.5 1 1877.50 1901.0 172.5 143.5 2 1699.00 1552.5 163.0 138.0 3 1429.50 1537.5 177.5 127.5 4 1406.50 1015.0 176.0 115.5 TDS (mg/l) ANOVA Sum of Source DF Squares Mean Square F Value Pr> F Model 3 13252236.51 4417412.17 26.72 <.0001 Error 16 2645627.80 165351.74 Corrected Total 19 15897864.31 R-Square CoeffVar Root MSE Water Mean 0.833586 42.02996 406.6346 967.4875 Source DF Anova SS Mean Square F Value Pr> F Group 3 13252236.51 4417412.17 26.72 <.0001 Scheffe's Test NOTE: This test controls the Type I experiment wise error rate. Alpha 0.05 Error Degrees of Freedom 16 Error Mean Square 165351.7 Critical Value of F 3.23887 Minimum Significant Difference 801.66 Means with the same letter are not significantly different. Scheffe’s Grouping Mean N Group A 1823.9 5 s A A 1737.8 5 i B 172.5 5 sc B B 135.8 5 ic The analysis of the TDS (mg/l) data shows that there is enough evidence against the null hypothesis in favour of the alternate one. Since the p-value (0.0001) of the F calculated is less than the significance level (0.05), there is sufficient ground to say that the water 67 treatment methods do not produce same results. The multiple comparisons of the methods using Student-Newman-Keuls Test shows that sand filtration and treatment with Ipomoea aquatica are not significantly different. However, treatment with Ipomoea aquatica reduces TDS better than sand filtration since the mean of the former is less than that of the latter. 68 Table 8: Comparison of concentration of Total Suspended solids (TSS) of effluent treated using SSF with effluent from treatment with Ipomoea aquatica TSS (mg/l) Week SSF Ipomoea Scontrol Icontrol Aquatica 0 238.0 239 8 6 1 221.5 315 6 23 2 21.0 35 6 10 3 18.0 70 6 3 4 14.0 31 5 15 TSS (mg/l) ANOVA The ANOVA Procedure Sum of Source DF Squares Mean Square F Value Pr> F Model 3 65323.7375 21774.5792 2.84 0.0708 Error 16 122602.0000 7662.6250 Corrected Total 19 187925.7375 R-Square CoeffVar Root MSE Water Mean 0.347604 135.6628 87.53642 64.52500 Source DF Anova SS Mean Square F Value Pr> F Group 3 65323.73750 21774.57917 2.84 0.0708 TSS (mg/l) ANOVA The ANOVA Procedure Student-Newman-Keuls Test for Water NOTE: This test controls the Type I experiment wise error rate under the complete null hypothesis but not under partial null hypotheses. Alpha 0.05 Error Degrees of Freedom 16 Error Mean Square 7662.625 Number of Means 2 3 4 Critical Range 117.3641 142.85459 158.39436 Means with the same letter are not significantly different. SNK Grouping Mean N Group A 138.00 5 i A A 102.50 5 s A A 11.40 5 ic A A 6.20 5 sc On the analysis of the TSS (mg/l), the p-value (0.0708) of the F calculated is greater than the level of significance (0.05), hence we have insufficient evidence to reject the null 69 hypothesis and conclude that the means of the water treatment methods on the chosen parameter are the same. Therefore, it does not matter whether sand filtration or phytoremediation with Ipomoea aquatica method is used since both will yield the same result . The mean of treatment with Ipomoea aquatica method on TSS (mg/l) is greater than that of sand filtration method even though they are not significantly different. Thus sand filtration is a better method for the removal of suspended solids. 70 Table 9: Comparison of colour of effluent treated using SSF with effluent from treatment with Ipomoea aquatica COLOUR (PtCo) Week SSF Ipomoea Scontrol Icontrol Aquatica 0 731 738 7 21 1 565 218 5 20.1 2 234 718 4 19 3 217 664 4 15 4 210 334 4 10.4 Colour ANOVA The ANOVA Procedure Sum of Source DF Squares Mean Square F Value Pr> F Model 3 1072794.737 357598.246 12.28 0.0002 Error 16 465872.320 29117.020 Corrected Total 19 1538667.058 R-Square CoeffVar Root MSE Water Mean 0.697223 72.02157 170.6371 236.9250 Source DF Anova SS Mean Square F Value Pr> F Group 3 1072794.738 357598.246 12.28 0.0002 Colour ANOVA The ANOVA Procedure Student-Newman-Keuls Test for Water NOTE: This test controls the Type I experiment wise error rate under the complete null hypothesis but not under partial null hypotheses. Alpha 0.05 Error Degrees of Freedom 16 Error Mean Square 29117.02 Number of Means 2 3 4 Critical Range 228.781 278.4703 308.76238 Means with the same letter are not significantly different. SNK Grouping Mean N Group A 534.4 5 i A A 391.4 5 s B 17.1 5 ic B B 4.8 5 sc The colour analysis of the water treatment methods is significantly different since the p- value of the F calculated (0.0002) is less than the level of significance (0.05). According 71 to the Post Hoc analysis of the same data, phytoremediation and sand filtration methods of water treatment are not significantly different. This implies that they may yield the same result on the colour of the water. However, the mean of the phytoremediation method on colour is greater than that of sand filtration, hence rendering the method of sand filtration better at reducing colour. 72 Table 10: Comparison of concentration of nitrates in effluent treated using SSF with effluent treated using Ipomoea aquatica NO3 (mg/l) Week SSF Ipomoea Scontrol Icontrol Aquatica 0 2.65 3.2 3.5 0.5 1 1.70 0.0 1.3 0.2 2 8.45 3.4 1.0 0.0 3 9.40 1.4 1.3 0.8 4 10.70 33.6 1.5 0.3 NO3 (mg/l) The ANOVA Procedure Sum of Source DF Squares Mean Square F Value Pr> F Model 3 949361.350 316453.783 10.37 0.0005 Error 16 488479.200 30529.950 Corrected Total 19 1437840.550 R-Square CoeffVar Root MSE Water Mean 0.660269 69.15821 174.7282 252.6500 Source DF Anova SS Mean Square F Value Pr> F Group 3 949361.3500 316453.7833 10.37 0.0005 NO3 (mg/l) The ANOVA Procedure Student-Newman-Keuls Test for Water NOTE: This test controls the Type I experiment wise error rate under the complete null hypothesis but not under partial null hypotheses. Alpha 0.05 Error Degrees of Freedom 16 Error Mean Square 30529.95 Number of Means 2 3 4 Critical Range 234.26615 285.14678 316.16513 Means with the same letter are not significantly different. SNK Grouping Mean N Group A 534.4 5 i A A 391.4 5 s B 80.0 5 ic B B 4.8 5 sc 73 The NO -3 data also shows enough evidence against the null hypothesis in favour of the alternative implying that the means are all significantly different. This is because the p- value of the F calculated (0.0005) is less than the level of significance (0.05). The treatment methods have effects on the NO3 of water. Post Hoc analysis shows that sand filtration is better at reducing nitrate concentration even though the means are not significantly different. 74 Table 11: Comparison of phosphate concentration in effluent treated using SSF with effluent from treatment with Ipomoea aquatica PO4 (mg/l) Week SSF Ipomoea Scontrol Icontrol Aquatica 0 5.470 5.60 1.44 1.70 1 3.550 4.70 1.14 0.20 2 3.030 3.90 1.09 0.10 3 2.810 5.64 2.49 1.20 4 3.350 8.24 2.54 7.04 PO4 (mg/l) The ANOVA Procedure Sum of Source DF Squares Mean Square F Value Pr> F Model 3 949361.350 316453.783 10.37 0.0005 Error 16 488479.200 30529.950 Corrected Total 19 1437840.550 R-Square CoeffVar Root MSE Water Mean 0.660269 69.15821 174.7282 252.6500 Source DF Anova SS Mean Square F Value Pr> F Group 3 949361.3500 316453.7833 10.37 0.0005 Scheffe's Test NOTE: This test controls the Type I experiment wise error rate. Alpha 0.05 Error Degrees of Freedom 16 Error Mean Square 30529.95 Critical Value of F 3.23887 Minimum Significant Difference 344.47 Means with the same letter are not significantly different. Scheffe’s Grouping Mean N Group A 534.4 5 i A B A 391.4 5 s B B C 80.0 5 ic C C 4.8 5 sc There is enough evidence against the null hypothesis in favour of the alternative since the p-value of the F calculated (0.0005) is less than the level of significance (0.05). This 75 implies that the means are all significantly different and sand filtration seems to be better at reducing phosphate concentration than phytoremediation with Ipomoea aquatica. 76 Table 12: Comparison of Biochemical Oxygen Demand (BOD) of effluent treated with SSF with effluent from treatment with Ipomoea aquatica BOD (mg/l) Week SSF Ipomoea Scontrol Icontrol Aquatica 0 35.00 35.0 6.2 6.2 1 25.00 16.0 4.5 4.3 2 21.50 15.1 0.9 3.2 3 11.00 18.0 0.2 1.8 4 8.50 4.1 0.2 0.9 BOD (mg/l) The ANOVA Procedure Sum of Source DF Squares Mean Square F Value Pr> F Model 3 1301.869500 433.956500 6.90 0.0034 Error 16 1006.380000 62.898750 Corrected Total 19 2308.249500 R-Square CoeffVar Root MSE Water Mean 0.564007 73.06194 7.930873 10.85500 Source DF Anova SS Mean Square F Value Pr> F Group 3 1301.869500 433.956500 6.90 0.0034 BOD (mg/l) 27 Student-Newman-Keuls Test for Water NOTE: This test controls the Type I experiment wise error rate under the complete null hypothesis but not under partial null hypotheses. Alpha 0.05 Error Degrees of Freedom 16 Error Mean Square 62.89875 Number of Means 2 3 4 Critical Range 10.633286 12.942746 14.350662 Means with the same letter are not significantly different. SNK Grouping Mean N Group A 20.100 5 s A A 17.640 5 i B 3.280 5 ic B B 2.400 5 sc 77 The BOD analysis shows that all the means are significantly different since the F test is in favour of the alternative hypothesis. Since the F calculated p-value (0.0034) is less than the significant level (0.05), there is enough evidence against the null hypothesis. In view of this, multiple comparison analysis revealed that sand filtration and phytoremediation with Ipomoea aquatica have mean values that are not significantly different. But the mean BOD of water treated with Ipomoea aquatica is greater than that of sand filtration implying making sand filtration a better method at reducing BOD. 78 Table 13: Comparison of Chemical Oxygen Demand (COD) of effluent treated using SSF with effluent from treatment with Ipomoea aquatica COD (mg/l) Week SSF Ipomoea Scontrol Icontrol Aquatica 0 368 368 256 256 1 288 192 224 160 2 240 160 192 128 3 176 96 160 64 4 144 64 128 32 The ANOVA Sum of Source DF Squares Mean Square F Value Pr> F Model 3 33830.4000 11276.8000 1.40 0.2802 Error 16 129228.8000 8076.8000 Corrected Total 19 163059.2000 R-Square CoeffVar Root MSE Water Mean 0.207473 48.63150 89.87102 184.8000 Source DF Anova SS Mean Square F Value Pr> F Group 3 33830.40000 11276.80000 1.40 0.2802 Scheffe's Test for Water NOTE: This test controls the Type I experiment wise error rate. Alpha 0.05 Error Degrees of Freedom 16 Error Mean Square 8076.8 Critical Value of F 3.23887 Minimum Significant Difference 177.18 Means with the same letter are not significantly different. Scheffe’s Grouping Mean N Group A 243.20 5 s A A 192.00 5 sc A A 176.00 5 i A A 128.00 5 ic The ANOVA analysis reveals that the F calculated p-value (0.2802) is greater than the level of significance (0.05). In view of this, there is sufficient information in the data in favour of the null hypothesis that the means of the treatment methods are the same. This 79 is also proven by the Post Hoc analysis of the data. Therefore, any method for water treatment on COD (mg/l) may yield similar results. 3.8 Microbial load Table 14: Microbiological characteristics of sewage effluent before and after treatment SAMPLE THB TC FC CFU/ml CFU/100ml CFU/100ml Raw sewage effluent 1210 348 162 Effluent after treatment using P.S 648 3 1 Effluent after using I.A 744 9 3 Effluent after treatment using SSF 767 0 0 P.S.: Pistia stratiotes, I.A: Ipomoea aquatica, CFU: coliform forming units, THB: Total heterotrophic bacteria, TC: Total coliforms, FC: Faecal coliforms Generally, there was a decrease in microbial load at the end of the experiment for both plants as well as for the sand filter. After the tenth week of slow sand filtration, there was zero count for total and faecal coliforms. 80 3.9 Comparison of efficiency of experimental sand filter to the filtration system of the Biogas plant Table 15: Comparison of the quality of effluent for ten weeks of SSF to quality of effluent passing through the filtration system of the VVU Biogas plant WEEKLY VARIATION IN EFFLUENT QUALITY Parameters analysed A 1 2 3 4 5 6 7 8 9 10 B pH 4.13 6.54 6.515 7.585 7.165 6.87 6.785 6.685 6.6 6.725 7.105 6.98 Temperature (°C) 30.25 29.2 31.05 31.45 32.6 33.45 25.65 30.25 29.8 30 25.55 27.75 DO (mg/l) 1.935 6.1 5.1 4.25 3.7 3.65 3.55 4.6 5.6 5.7 5.75 4.19 BOD (mg/l) 35 25 21.5 11 8.5 7.5 5.5 4.3 2.35 1.25 1.05 26 COD (mg/l) 368 288 240 176 144 96 64 64 64 32 32 98 Turbidity (NTU) 159.5 119 12.5 10.95 9.75 9.7 11.25 7.95 7.1 6.6 5.8 47.5 Colour (PtCo) 731 565 234 217 210 206.5 199.5 199 198.5 196.5 184 515 TDS (mg/l) 2706.75 1877.5 1699 1429.5 1406.5 1374.25 1345.85 1271.5 1286.5 1274.5 1226.25 1704.8 EC (µs/cm) 5413.5 3755 3398 2859 2813 2748.5 2692 2579.5 2573 2549 2452.5 3409.5 Phosphates(mg/l) 5.47 3.55 3.03 2.81 3.35 3.97 3 2.895 2.84 2.705 2.54 3.02 Nitrates (mg/l) 2.65 1.7 8.45 9.4 10.7 8.2 5.65 4.3 4.25 4.3 3.4 5.75 TSS (mg/l) 238 221.5 21 18 14 11.5 10.5 6.5 7 5.5 5 65.5 A: Raw sewage effluent from intermediary chamber, B: effluent from the filtration system of the VVU Biogas facility 82 3.10 Quality assessment of safety of treated effluent for disposal/reuse Table 16: Assessment of safety of effluent treated using SSF for disposal/reuse Parameters analysed 1 2 3 4 5 6 7 8 9 10 GEPA (2004) WHO (1993) p H 6.54 6.515 7.585 7.165 6.87 6.785 6.685 6.6 6.725 7.105 6-9 6.5-8.5 Temperature (°C) 29.2 31.05 31.45 32.6 33.45 25.65 30.25 29.8 30 25.55 < 3°C above ambient DO (mg/l) 6.1 5.1 4.25 3.7 3.65 3.55 4.6 5.6 5.7 5.75 BOD (mg/l) 25 21.5 11 8.5 7.5 5.5 4.3 2.35 1.25 1.05 COD (mg/l) 288 240 176 144 96 64 64 64 32 32 Turbidity (NTU) 119 12.5 10.95 9.75 9.7 11.25 7.95 7.1 6.6 5.8 75 5 Colour (PtCo) 565 234 217 210 206.5 199.5 199 198.5 196.5 184 TDS (mg/l) 1877.5 1699 1429.5 1406.5 1374.25 1345.85 1271.5 1286.5 1274.5 1226.25 1000 EC (µs/cm) 3755 3398 2859 2813 2748.5 2692 2579.5 2573 2549 2452.5 1500 700 Phosphates(mg/l) 3.55 3.03 2.81 3.35 3.97 3 2.895 2.84 2.705 2.54 Nitrates (mg/l) 1.7 8.45 9.4 10.7 8.2 5.65 4.3 4.25 4.3 3.4 TSS (mg/l) 221.5 21 18 14 11.5 10.5 6.5 7 5.5 5 Faecal coliforms 0 10 0 (CFU/100ml) Total coliforms 0 400 0 (CFU/100ml) 83 Table 17: Assessment of the quality of effluent treated using Pistia stratiotes for disposal/use Parameter Effluent treated GEPA (2004) WHO (1993) using (Max. permissible level) Max. value for drinking Pistia stratiotes for discharge into natural water waters p H 7.87 6-9 6.5-8.5 Temperature (°C) 25.1 <3°C above ambient - DO (mg/l) 2.2 - - BOD (mg/l) 17 - - COD (mg/l) 224 - - Phosphates (mg/l) 4.88 - - Nitrates (mg/l) 1 - - EC (µs/cm) 2975 1500 700 TDS (mg/l) 1488 1000 - TSS (mg/l) 96 - - Colour (PtCo) 530 - - Turbidity (NTU) 90 75 5 Faecal coliforms 1 10 0 (cfu/100ml) Total coliforms 3 400 0 (cfu/100ml) Table 15 compares the experimental values to those obtained from the filtration system of the Biogas plant. A is the raw effluent from the intermediary chamber of the Biogas plant. A was subjected to slow sand filtration over a ten week period and the values obtained on a weekly basis are shown. B is effluent obtained after the raw effluent went 84 through the filtration system of the biogas plant. From the table it is evident that there were improvements in effluent quality for both the experimental filters and the filtration system of the biogas plant. It can be seen from table 16 that, the experimental sand filters reduced contaminants to acceptable limits outlined by GEPA (2004) and WHO(1993) with the exception of TDS and EC. Table 17 above compares the quality effluent treated using Pistia stratiotes to standards stipulated by GEPA (2004) and WHO (1993). Turbidity, EC and TDS did not meet the standards. 85 Table 18: Assessment of the quality of effluent treated using Ipomoea aquatica for disposal/ use WEEK Parameter 1 2 3 4 GEPA (2004) WHO (1993) p H 7.38 7.22 7.77 7.65 6-9 6.5-8.5 Temperature (°C) 25.2 29.1 32 25.8 <3°C above - ambient DO (mg/l) 2.1 3.5 1.9 4.1 - - BOD (mg/l) 16 15.1 18 4.1 - - COD (mg/l) 192 160 96 64 - - Phosphates (mg/l) 4.7 3.9 5.64 8.24 - - Nitrates (mg/l) 0 3.4 1.4 33.6 - - EC (µs/cm) 3122 3105 3075 2030 1500 700 TDS (mg/l) 1901 1552. 1537.5 1015 1000 - 5 TSS (mg/l) 315 35 70 31 - - Colour (PtCo) 718 664 533 334 - - Turbidity (NTU) 147 20.2 54 12.9 75 5 Faecal coliforms (cfu/100ml) - - - 3 10 0 Total coliforms (cfu/100ml) - - - 9 400 0 86 3.11 Public perceptions on water scarcity and the reuse of wastewater 3.11.1 Demographic background of respondents A total of 120 questionnaires were administered to students and staff of the Valley View University. One hundred and two people completed the questionnaires, 46.1% male and 54% female. From the table, it can seen that higher proportions of the respondents were between the ages of 18-30 (72.5%) and educated to the tertiary level. Majority (86.3%). of the respondents are single. Table 19: Demographic characteristics of respondents Marital status Gender Age (Years) Educational level Single Married Male Female 18- 31- 41- Above SHS Tertiary Others 30 40 60 60 Frequency 89 13 47 55 74 12 14 2 15 86 1 Percentage 87.3 12.7 46.1 53.9 72.5 11.8 13.7 2 14.7 84.3 1 (%) 3.11.2 Environmental perceptions Fig 24 below shows that out of the 102 respondents interviewed, 57.8% have access to treated tap water whilst 23.5% use water from the borehole. 2% have their source of water from the stream whilst 6.9% harvest rain water for domestic use. 57.8% of respondents stated that they have regular supply of water whiles the remaining 42.2% do not have regular access. 87 Fig 24: Source of water for domestic use by respondents 88 3.11.3 Water as a scarce resource Fig 25: Proportion of respondents who consider water to be a scarce resource 3.11.4 Causes of water scarcity Fig 26: Causes of water scarcity stated by respondents 89 3.11.5 Sources of wastewater Fig 27: Sources of wastewater stated by respondents 3.11.6 How wastewater is generated Fig 28: How wastewater is generated by respondents 90 3.11.7 Use of wastewater generated at home Fig 29: Uses of wastewater generated at home All respondents admitted that they generate wastewater and the major source of wastewater mentioned is domestic washing (81%). 13.7% generate wastewater through work activities such as washing bay, tie and dye industry, catering industry and commercial laundry. Majority of the respondents (61.8%) mentioned that wastewater generated at home is thrown away (Table 4.15). 36.3% use the wastewater for flushing toilet whilst 2% use the wastewater for irrigation purposes. This result indicates that only 38.3% of the 91 respondents conserve water by reusing wastewater. From, Table 4.18 it is observed that 57.8% of respondents have regular access to water and this may explain why most of the respondents throw the wastewater away. 3.11.8 Type of toilet facility Fig 30: Type of toilet facilty respondents have access to From the figure above, 88.2% of respondents have access to a toilet facility, the main facility being water closet. However, only 47.1% have knowledge about how the human excreta is disposed of as shown in the table below. This suggests that many people are not conscious of their environment 92 3.11.9 Method of sewage disposal Fig 31: Methods of disposal of sewage as stated by respondents Out of the 48% of respondents who have an idea about the disposal of faecal matter, 26.5% mentioned dumping in the sea as the method of sewage disposal, while 17.65% are aware of the use of sewage for production of biogas. A small proportion of the respondents are aware of the use of sewage for compost (4.9) and irrigation of crops (3.9%). 93 3.11.10 Reasons for supporting wastewater reuse Fig 32: Respondents reasons for supporting wastewater reuse Most of the respondents (31.4%) support wastewater reuse for the reason that it will minimize dependency on treated water. 27.5% support use of wastewater for the reason that it conserves water. 31.4% did not specify any reason and this may correspond to the proportion of respondents (33.3%) who had no idea about wastewater reuse (Table 4.20). this statistics suggests that a greater proportion of people are concerned about water scarcity and water conservation. 94 42.2% of the respondents had no idea about health risks associated with wastewater reuse. Among the health risks associated with wastewater reuse mentioned by respondents are cholera (27.5%), bacterial infections (23.5%) and diarrhoea (5.9%). One person mentioned candidiasis as the health risk associated with using wastewater particularly for flushing toilets. 3.11.11 Health risks associated with wastewater reuse Fig 33: Types of health risks associated with wastewater reuse as stated by respondents 95 Fig 34: Respondents response on how health risks can be minimized Whilst 62% of the respondents stated that treating the wastewater before use would minimize the health risks, 11.8% prefer that the use of wastewater be avoided. This suggests that more people agree that with treatment, wastewater can be used. 96 Most of the respondents (68.6%) are of the view that the Millennium Development Goal (7) which highlights that the proportion of the population without sustainable access to safe drinking water and basic sanitation be halved by the year 2015 cannot be achieved 3.11.12 Uses of wastewater 3.11.12.1 Irrigation of crops Fig 35: Response of respondents to the use of treated wastewater for irrigation of food crops 97 3.11.12.2 Fire fighting Fig 36: Response of respondents to the use of treated wastewater for fire fighting 3.11.12.3 Industry Fig 37: Response of respondents to the use of treated wastewater for industry 98 3.11.12.4 Construction of buildings Fig 38: Response of respondents to the use of treated wastewater for construction of buildings 3.11.12.5 Swimming pool Fig 39: Response of respondents to the use of treated wastewater for swimming pool 99 3.11.12.6 Aquifer augmentation Fig 40: Response of respondents to the use of trated wastewater for aquifer augmentation Of the reuse options suggested, most people supported to the use of treated wastewater for irrigation (70.6%), firefighting (72.6%), industry (52.9%), construction of buildings (72.6%), toilet flushing (82.4%), public park/ sports field irrigation (54.9%) and commercial car wash (47.1%). This may be due to the belief that these options pose little or no threat to human health. Only 29.4% of the respondents agreed to the use of the treated water for aquifer augmentation and 53.9% were not sure. A higher percentage of the respondents (47.1%) disagreed with the use of treated water for general cleaning and 100 laundry and swimming pool (65.7%) probably because there is high contact and health risks may be high if the water is not properly treated. Most of the respondents (52.9%) would not recommend wastewater use to their communities and this means that more education is needed to encourage people to treat and use wastewater. 101 CHAPTER FOUR 4.0 DISCUSSION Results of the study showed that with the exception of nitrates, dissolved oxygen (DO) and pH, all other parameters analyzed had higher values in the effluent from intermediary point than in effluent from the final outlet. This suggests that the filtration system of the biogas facility reduced contaminant load although the EC and TDS did not meet Ghana EPA emission guidelines of 1500 µS/cm and 1000 mg/l respectively. The electrical conductivity (EC), though reduced in the final effluent (3216-3603 µs/cm) far exceeds the 1500 µS/cm set by GEPA (2010) maximum for disposal into the environment or for use in agriculture. The EC of effluent discharged into the mango plantation is important since the most influential water quality guideline on crop productivity is the water salinity hazard as measured by electrical conductivity (Hamid et. al., 2013). The primary effect of high EC water on crop productivity is the inability of the plant to compete with ions in the soil solution for water, a condition known as Osmotic drought (physiological drought). The higher the EC, the lesser is the water available to plants, even though the soil may appear to be wet. Plants can only transpire "pure" water thus usable plant water in the soil solution decreases dramatically as EC increases. The amount of water transpired through a crop is directly related to yield. Therefore, irrigation water with high EC reduces yield potential (Hamid et.al, 2013). Beyond effects on the immediate crop is the long term impact of salt loading through the irrigation water. Nitrates were also not efficiently removed as its concentration in the filtered effluent was higher and this may be due to the conversion of ammonia nitrogen into nitrates through a 102 denitrification process. However, this poses no problem as plants utilize nitrates for growth. The faecal coliforms are within the 103 -106 CFU/100 ml set by WHO (2006) for use in agriculture and aquaculture. The faecal coliforms are also within the WHO (2006) 1000 CFU/100ml limit for restricted irrigation and the 105/100ml for unrestricted irrigation. The dissolved oxygen recorded a high value (2.98-5.4 mg/l) after filtration and this may be due to a reduction in population of aerobic microorganisms. The pH of effluent from the intermediary chamber was acidic (3.9-4.14). However, after passing through the filtration system, the pH changed (6.47-7.48) and met the Ghana EPA recommended limit i.e. 6-9. The COD of the final effluent was also within the 250mg/l GEPA (2010) maximum permissible level for discharge into water bodies or for use in irrigation. The BOD was also within the GEPA maximum acceptable standard of 50 mg/l for discharge into water bodies and WHO (1989) standard of 20-100 mg/l for irrigation or aquaculture. The heavy metals analysed were Zn, Pb, Fe, Cd, Cr, Cu and Ni. Apart from Fe and Cu, all other heavy metals analysed were non detectable. In the digestion process, putrefactive bacteria are present to degrade heavy metals during hydrolysis, acetogenesis and methanogenesis (Issah and Salifu, 2012). From the results of this experiment, it can be inferred that, Zn, Pb, Cd, Cr, and Ni if present, were probably degraded by putrefactive bacteria but Cu and Fe could not be degraded by the putrefactive bacteria. Notwithstanding this, the values recorded for Cu and Fe in the final effluent did not 103 exceed the WHO (1993) guideline maximum value for domestic use of water (2 mg/l for Cu and 0.3 mg/l for Fe). The concentrations of Cu in the final effluent pose little threat to the environment. This is because, when copper ends up in the soil, it strongly attaches to organic matter and minerals. As a result, it does not travel far after release and it hardly ever enters groundwater (Baysal et. al., 2013). Fe is not toxic to plants in aerated soils. Contrary to a report by Foresti (2002) that effluents from anaerobic reactors treating domestic sewage can rarely comply with the emission standards and that the main important constituents or components deserving attention which are nutrients and pathogens are not removed efficiently in the most commonly used anaerobic reactors, the effluent from the VVU biogas, complies with guidelines for irrigation with the exception of EC which exceeded the limit of 1500 µS/cm. From the results of the phytoremediation experiment, it was observed that Pistia stratiotes survived for only five days whilst Ipomoea aquatica survived for four weeks in the raw sewage effluent. According to Piyush et. al. (2012), Pistia stratiotes is able to survive in wastewater for a maximum period of 25 days. Haller et. al., (1974) reported that Pistia Stratiotes has a higher survival rate at higher levels of electrical conductivity (> 4000 µs/cm) but does not do well at higher COD levels. The electrical conductivity for the raw sewage effluent used in this experiment was 5365 µS/cm which is tolerable but the COD was 368mg/l, which may have been too high to support the growth of the plant thus leading to the death of the plant after five days. When the raw effluent was diluted to 50% and 75%, the EC reduced to 2040 µs/cm and 1211µs/cm respectively but the COD 104 reduced to 354mg/l and 323mg/l respectively, Pistia stratiotes showed similar results, i.e. died by the fifth day. In the distilled water (control) which had lower EC (309 µS/cm) and COD of 256 mg/l, Pistia stratiotes survived for two weeks even though the nitrate and phosphate concentrations in the control were lower (0.5 mg/l and 1.7 mg/l respectively) than that in the raw effluent (3.2 mg/l nitrates and 5.6 mg/l phosphates). This implies that Pistia stratiotes can tolerate low nutrient levels. Ipomoea aquatica plants developed new shoots and leaves after three days and survived in the raw effluent for 28 days. In a study by Yu et. al. (2013) using Ipomoea aquatica to purify biogas slurry, Ipomoea aquatica reached the highest peak of growth after 60 days. This indicates that Ipomoea aquatica has high tolerance to contaminants and thus was able to survive despite the high contaminant load. The results showed that nitrogen and phosphorus were accumulated in both plants. Pistia stratiotes accumulated less nitrogen (10.08%) and phosphorus (21.37%) than Ipomoea aquatica (21.37%) which survived for four weeks. From the results of the experiment, Ipomoea aquatica accumulated more nutrients at the end of the experiment than Pistia stratiotes. This was expected since Ipomoea aquatica stayed longer in the sewage effluent than Pistia stratiotes. Ipomoea aquatica shows much higher nutrient removal efficiency with their high nutrient uptake capacity as shown in the figures 3 and 4 . It can be seen that, after five days, there was a greater reduction in the concentration of phosphates and nitrates when the raw effluent was treated with Ipomoea aquatica. Lu et. al. (2013) reported that low concentrations of nutrients may reduce the performance of 105 plants in removing nutrients. This may be responsible for the low nutrient removal efficiency of Pistia stratiotes. After the first and second weeks of experiment, there was a reduction in BOD with a corresponding increase in DO. This could be as a result of reduction in microbial activity and photosynthesis. Photosynthesis results in greater dissolution of oxygen due to a reduction in TDS. During the third week, a reduction in DO was observed corresponding to a rise in BOD and this may be due to dead leaves falling back into the water and decomposing leading to an increase in microbial activity. The microorganisms were using up the DO in the water and that accounted for the decrease in DO. However, during the fourth week, new shoots had sprouted and photosynthetic activity coupled with the uptake of microorganisms by the plant led to an increase in the DO and a corresponding decrease in the BOD. Reduction of EC and TDS throughout the study period was due to absorption of dissolved solids by Ipomoea aquatica. Reduction in phosphates and nitrates is due to uptake by the plant as nutrients for growth. The well-developed roots of aquatic plants have microbes attached to them and these help to utilize nutrients (Wijetunga et.al, 2009). An increase in the phosphate concentration after the second week may be due to falling leaves which decomposed and released the phosphates back into the water. All the nitrates were taken up after the first week of the experiment but increased again after the second week. Some of the plants died when all the nitrogen was used up and decomposition released the nitrates into the water which was used by the surviving plants 106 and new shoots developed. At the end of the experiment, there was an increase in nitrogen concentration (33.6 mg/l). The concentrations of nitrates and phosphates in the water were higher at the end of the experiment and this suggests that most of the nutrients were released back into the water. There was a progressive decrease in Chemical Oxygen Demand (COD) throughout the experiment. The mean COD of the raw sewage effluent was 368 mg/l but this reduced to 64 mg/l by the end of the experiment corresponding to an 82.6% removal of COD. This suggests that Ipomoea aquatica can assimilate COD. Decrease in COD may also be due to an increasing DO thereby providing a better environment for oxidation. The microbes around the roots of Ipomoea aquatica can also contribute to treatment by providing a comfortable environment for the microbes thus removing organic matter effectively. The filtration rate of the slow sand filter was high at the first run (733 ml/min) but decreased with time of filter run. This is because as time went on, the sand grains settled decreasing the voids which became clogged with particles from the raw sewage effluent. Because of this, a drop in the filtration rate was observed. Around the fourth week, the system started to level out with the filtration rate around 698 ml/min. At this point, the sand was fully settled and saturated. There was a notable positive reduction in the turbidity of the water samples after filtration (even though turbidity was high). Turbidity decreases due to reduction in TDS and TSS. These results agree with findings of El-Taweel (2000) that 92% of turbidity was removed when slow sand filter was used for wastewater treatment. The major turbidity reduction mechanism is believed to be through surface straining as predicted by Haarhoff and 107 Cleasby (1991). Excessive turbidity or cloudiness, in drinking water is aesthetically unappealing and may also represent a health concern. The concentration of nitrates reduced after the first run and shot up after the second week. It reached a peak value after the fifth week and declined. An increase in concentration of nitrates from the second week to the fifth week may be due to oxidation of ammonia nitrogen to nitrates. After the fifth week, the growth of algae may have commenced leading to the uptake of nitrates by the algae as nutrients for growth, thereby resulting in a decrease in the concentration of nitrates. A reduction in concentration of phosphates was observed until it increased from the fifth to sixth week then a decline was observed. The reduction in phosphate concentration after the sixth week may be due to uptake by algae growing on the surface of the filter bed. Dissolved oxygen (DO) of raw sewage effluent was low before filtration (1.935 mg/l). Low oxygen concentration is associated with heavy contamination by organic matter. There was an increase in DO at the beginning of the experiment and this may be due to the fact that the pores in the sand were filled with air and so there was a mixing of the effluent with atmospheric oxygen. However, there was a decline after the second week after which the concentration increased again after the 7th week. The decline was probably due to the fact that the air pores were filled with raw effluent and microbial activity was high. After the seventh week, enhancement of DO may be due to the minimization of organic pollution load and microbial population due to their retention in the filter bed and the simultaneous mixing with atmospheric oxygen. 108 Reduction in Biochemical Oxygen Demand (BOD) may be due to a reduction in the bacterial population due to their retention on the surface of the filter bed as a result of the formation of the dirt cover. Removal of BOD is related to the removal of TSS (Benth et.al., 1981). A reduction in TSS was observed in this study. The reduction in Chemical Oxygen Demand (COD) may be due to the fact that most of the organic wastes were oxidized as they moved through the filter bed. A similar trend was recorded by Rao et. al. (2003) when wastewater was filtered through slow sand filter. Reduction in total suspended solids (TSS) is due to retention time of sewage effluent in the filter bed. The sand filter primarily removes suspended solids and the effectiveness of the filter is related to the removal of TSS (Benth et. al., 1981) The main use of pH in water analysis is for detecting abnormal water (Tak et.al, 2012). The initial pH of the sewage effluent used for this study was 4.04 which is acidic. The pH of the water samples were taken (during the duration of the study) on a weekly basis. There was an increase in pH both with the aquatic plants and with the sand filters. For both technologies, pH ranged from 6.54 to 7.87. The increase in pH observed in effluent treated with plants is basically attributed to the biochemical processes. Plants can absorb anions such as NO -3 , NO - 3- 2 and PO4 for their growth and, eventually resulting in the reduction of acid forming anions leading to an increase in the pH. Temperature is an important parameter because it affects chemical and biological reactions and solubility of gases such as oxygen. Increasing temperature increases reaction rates and solubility up to the point where temperature becomes high enough to 109 inhibit the activity of most microorganisms (around 35°C). During the study, the temperature range was 25.1 - 33.45 which allows microbial activity. An assessment of the microbial load of the effluent showed that, generally, there was a decrease in microbial load at the end of the experiment for both plants as well as for the sand filters. After the tenth week of filtration, there was zero count for total and faecal coliforms. This is attributed to the fact that, the small sand grains provided a large total surface area for biofilm growth. This biofilm, also known as dirt cover or “schmutzdecke” layer may have resulted in the reduction in microbial load in the effluent from the sand filter. This layer consists of the organic matter from the raw effluent that settles on the filter surface and becomes a feeding ground for bacteria and microorganisms. Thus, microorganisms spend longer time on the surface of the filter resulting in a reduction in microbial load of effluent passing through the filter media. Microbes in wastewater perform a vital role for the releasing of nutrient to the wastewater by utilizing the organic compounds for their growth and development. Ipomoea aquatica and Pistia stratiotes, which showed good performances with regard to pollutant removal, had well developed root systems which facilitated the microbes to colonize well to form a satisfactory habitat for their growth and development. A reduction in the microbial load may be due to a migration of the microbes in the sewage effluent to the roots of the aquatic plants used in this study. Eventually, the benefits of degradation product of organic compounds are used by the aquatic macrophytes for their growth and development. Therefore, it can be concluded that microbes as well as macrophytes, work together to purify the polluted wastewater 110 A comparison of SSF and phytoremediation with Ipomoea aquatica using the one-way ANOVA shows no significant difference in the turbidity and Chemical Oxygen Demand (COD) of the treated effluent. This implies that if either of the two technologies is applied in treating wastewater which is high in turbidity and COD, the same result would be achieved. There were significant differences in values obtained for dissolved oxygen (DO), nitrates and phosphates. Based on these differences, SSF performed better at removing nitrates and phosphates while Ipomoea aquatica proved better at replenishing DO. No significant differences were recorded for electrical conductivity (EC), total dissolved solids (TDS), total suspended solids (TSS), Biochemical Oxygen Demand (BOD) and colour. However, when the mean values were compared, SSF was better at improving the quality of effluent by reducing TSS, BOD and colour while Ipomoea aquatica was better at reducing EC and TDS. Phytoremediation using Pistia stratiotes produced an effluent which is higher in EC, turbidity, total and faecal coliforms than the recommended values rendering the treated effluent unsafe for domestic use and for disposal into natural water bodies. Electrical conductivity of water is a useful and easy indicator of the salinity or total salt content of water. Wastewater effluents often contain high amounts of dissolved salts from domestic sewage. Build-up of salts from domestic wastes can interfere with water reuse by municipalities, industries manufacturing textiles, paper and food products, and agriculture for irrigation. High salt concentrations in waste effluents can increase the salinity of the 111 receiving water, which may result in adverse ecological effects on aquatic biota (Fried, 1991). Also, a very high salt concentration (> 1 000 mg/l) imparts a brackish, salty taste to water and is discouraged because of the potential health hazard (WHO, 1979, Quality of Domestic Water Supplies, 1998). The effluent obtained from treatment with Pistia stratiotes had a turbidity value higher (90 NTU) than the Ghana EPA recommended value for disposal into natural waters (75 NTU). An excessive value of turbidity is an indication of the presence of among other things disease causing organisms and makes water purification processes difficult which may increase treatment cost. High turbidity values are also an indication of microbiological contamination (DWAF, 1998). This suggests that the effluent cannot be consumed directly by human beings without treatment. Dissolved Oxygen (DO) concentration in unpolluted water is normally about 8-10 mg/l at 25oC (DFID, 1999). Concentrations below 5.0 mg/l adversely affect aquatic life. The treated effluent has a very low DO (2.2 mg/l) making it unsuitable for aquaculture. For the protection of fisheries and aquatic life, the EU guidelines stipulate the BOD target limits of 3.0-6.0 mg/l (Chapman, 1996). The high level in effluents treated with Pistia stratiotes (17 mg/l) disqualifies the effluent for use as an aquatic ecosystem. The GEPA (2010) proposes a BOD of 50-200 mg/l and 250-1000 mg/l COD for effluent discharge into water bodies. This implies that considering BOD and COD, the effluent from treatment with Pistia stratiotes can be safely discharged into water bodies. 112 The WHO safe limit for nitrate for lifetime use is 10 mg/l. Effluent treated with Pistia stratiotes is within this limit and thus can be used for non-potable domestic purposes. However, the effluents can be a source of eutrophication for the receiving water bodies as the values obtained exceeded the recommended limits for no risk of 0-0.5 mg/l (DWAF, 1998). The level of phosphate in water systems which will reduce the likelihood of algal and other plant growth is 5µg/l (DWAF, 1998). This limit is exceeded by effluent treated with Pistia stratiotes (4.88 mg/l). Based on this, treated effluent is not safe for disposal into water bodies. According to the WHO (1989) guidelines for coliform bacteria, a limit of 105 /100 ml is recommended for unrestricted irrigation (i.e. irrigation of cereal crops, industrial crops, fodder crops, pasture and trees) and 1000FC/100ml for restricted irrigation (irrigation of crops likely to be eaten uncooked, sports field or public parks). The effluent from treatment with Pistia stratiotes was well within the recommended limits and can be used for irrigation. In the current study, effluent obtained for each week of treatment was higher in EC, turbidity, total and faecal coliforms than the recommended values. None of the effluents obtained for any of the weeks is suitable for potable uses. Due to the high EC and TDS, the effluent is unsuitable for discharge into natural water bodies and irrigation. 113 After the second week of treatment, Ipomoea aquatica reduced the turbidity to a value lower (20.2 NTU) than the recommended value for discharge into natural waters (75 NTU). However, after the fourth week of treatment, the turbidity was still too high (12.9 NTU) for potable use (5 NTU). This implies that after two weeks of treatment of sewage effluent with Ipomoea aquatica, the effluent can be discharged into natural waters. For the protection of fisheries and aquatic life, the EU guidelines stipulate the BOD target limits of 3.0-6.0 mg/l (Chapman, 1996). This is met by the effluent after the fourth week of treatment (4.1mg/l). This means that, considering BOD, sewage effluent can be used as an aquatic ecosystem only after the fourth week of treatment. The GEPA (2010) proposes a BOD of 50-200 mg/l and 250-1000 mg/l COD for effluent discharge into water bodies. This implies that considering BOD and COD, the effluent from treatment with Ipomoea aquatica can be safely discharged into water bodies. The effluent obtained from the first to third weeks of treatment meets the recommended limit for nitrate for lifetime use (10 mg/l). After the fourth week, the limit was exceeded. This means that effluents obtained from the first three weeks of treatment with Ipomoea aquatica can be used for non-potable domestic purposes but effluent obtained after the fourth week is not safe for lifetime use. The effluents can be a source of eutrophication for the receiving water bodies as the values obtained exceeded the recommended limits for no risk of 0-0.5 mg/l (DWAF, 1998). The level of phosphate in water systems which will reduce the likelihood of algal and other plant growth is 5µg/l (DWAF, 1998). This 114 limit was exceeded by effluent treated with Ipomoea aquatica. The treated effluent is therefore not safe for disposal into water bodies. According to the WHO (1989) guidelines for coliform bacteria, a limit of 105 /100 ml is recommended for unrestricted irrigation (i.e. irrigation of cereal crops, industrial crops, fodder crops, pasture and trees) and 1000FC/100 ml for restricted irrigation (irrigation of crops likely to be eaten uncooked, sports field or public parks). The faecal coliform count of effluent obtained from treatment with Ipomoea aquatica is within the recommended limits and can be used for irrigation. In this study pH and temperature of all effluents were within the recommended limits for domestic use, irrigation and discharge into natural waters. Concentrations of DO below 5 mg/l adversely affect aquatic life. In this study, it was observed that only the effluent from the first (6.1mg/l), second (5.1mg/l), eighth (5.6 mg/l), ninth (5.7mg/l) and tenth (5.75mg/l) weeks are suitable for discharge into an aquatic environment. The EU guidelines for BOD for the protection of fisheries and aquatic life i.e. 3.0-6.0 mg/l was met only by effluent obtained after the eighth (2.35mg/l), ninth (1.25mg/l) and tenth (1.05 mg/l) weeks of SSF. The GEPA (2010) proposes a BOD of 50-200 mg/l and 250-1000 mg/l COD for effluent discharge into water bodies. The BOD for discharge into water bodies is met by all effluents. Considering the COD limit for discharge into water bodies, only the effluents from the second to tenth weeks of treatment meet the limit. The COD from effluent from the first week of SSF exceeds the limit for discharge into water bodies. 115 Although SSF reduced EC and TDS progressively, the values obtained after the tenth week were still too high and do not meet guidelines for irrigation, discharge into water bodies and potable uses. The turbidity of effluent obtained from the second to tenth weeks of SSF are within the Ghana EPA guideline for discharge into water bodies (75 NTU) but none of the effluents met the WHO guideline for drinking water (5 NTU). It is possible that if the length of time for SSF is prolonged, the EC and turbidity would be reduced to recommended limits. The WHO safe limit for nitrate for lifetime use of 10 mg/l was met by effluent obtained for all weeks of the SSF experiment with the exception of the fourth week which recorded a value of 10.7 mg/l. The effluents obtained from all the weeks with the exception of the fourth week can be used for domestic purposes such as toilet flushing, laundry and cleaning of floors. However, the effluents can be a source of eutrophication for the receiving water bodies as the values obtained exceeded the recommended limits for no risk of 0-0.5 mg/l (DWAF, 1998). None of the effluents meet the 5 µg/l limit for prevention of algal and other plant growth in water systems. According to the WHO (1989) guidelines for coliform bacteria, a limit of105 /100 ml is recommended for unrestricted irrigation (i.e. irrigation of cereal crops, industrial crops, fodder crops, pasture and trees) and 1000FC/100ml for restricted irrigation (irrigation of crops likely to be eaten uncooked, sports field or public parks). Effluent from the tenth week of is well within the recommended limits and can be used for irrigation. 116 In this study, the performance of the experimental SSF was compared to that of the filtration system of the Biogas plant. Both filtration systems changed the pH of the effluent from acidic (4.13) to neutral. The experimental filters performed better at replenishing the DO after the first four weeks and also after the seventh to tenth weeks. During the fourth to sixth weeks, the filtration system of the Biogas facility performed better. The experimental sand filter was better at reducing the Biochemical Oxygen Demand (BOD). After the first week of SSF the BOD was reduced to 25 mg/l which is lower than that obtained for the filtration system of the Biogas facility (26 mg/l). EC and TDS values were also lower after the second week of SSF than that obtained from the Biogas facility. From the table, it can be seen that, after the tenth week, the SSF experiment was better at enhancing DO, and reducing BOD, COD, turbidity, colour, TDS,TSS,EC, total and faecal coliforms of the final effluent. The results of the social survey show that the degree of close human contact is important in determining public support of wastewater reuse. The results of this study seem to parallel those of other studies by Bruvold (1984), EPA (1992), Crook et.al., (1994), Freidler et al., (2006) and Hartley (2006), where high support was to low and medium contact reuse options. In this study, medium contact options received high support. These options are fire-fighting (71.6%), Industry (52.9%), construction of buildings (71.6%), toilet flushing (81.4%), commercial car wash (46.1%) and public parks irrigation (54.9%). There was low support for the high contact options such as swimming pool 117 (10.7%), aquifer augmentation (29.4%), and laundry (34.3%). Irrigation of food crops which was considered to be a high contact option received high support (69.6%) probably because it was perceived by the public as a medium contact option. Most of the participants (65.7%) agreed that water is a scarce resource. Participants in the survey who identified themselves as supporters of wastewater reuse revealed that the most important reasons for their support minimization of dependency on treated water (37.3%) and water conservation (36.3%) Environmental protection ranked as the third most frequent response (26.5%). The demographic data shows that 83.3% of respondents are educated to the tertiary level. However, only 48% are aware of how faecal matter is disposed of. Of the disposal options, dumping into the sea and treatment to produce biogas are well known among respondents. Very few know about the use of sewage for irrigation and treatment to produce compost. Only 44.1% of the respondents are familiar with the concept of wastewater reuse. These suggest that the level of environmental awareness among the public is low. Domenech and Sauri (2010) found out that the perception of health risks and environmental awareness are in different degrees significant determinants of public acceptance. According to these authors, improving the level of knowledge of health risks and environmental awareness would reduce the risk of social refusal of wastewater recycling. The objectives of this study were achieved. The quality of sewage effluent from the VVU Biogas facility was monitored. Slow sand filtration and Phytoremediation technologies were successful at treating the raw effluent to some extent. 118 CHAPTER FIVE 5.0 CONCLUSIONS The results of this study substantiate that phytoremediation and Slow Sand Filtration are effective methods for the treatment of wastewater. Phytoremediation and Slow Sand Filtration (SSF) are effective methods for treating sewage effluent. Generally, both technologies reduce contaminant levels. However, phytoremediation with Ipomoea aquatica is better than sand filtration at reducing EC and TDS. Sand filtration performed better at enhancing DO whilst reducing colour, nitrates, phosphates and BOD. Both technologies are equally effective at reducing turbidity, TSS, and COD since there was no significant difference in mean values obtained for these parameters. Both technologies changed the p H from acidic to neutral. Pistia stratiotes and Ipomoea aquatica are both effective at reducing contaminant load. However, the results of this study show that Pistia stratiotes does not survive for long in sewage effluent. Dilution of effluent gave similar results. Most of the parameters analysed with respect to the sewage effluent from the Valley View University Biogas facility fell within the acceptable guidelines with the exception of EC. Treated effluents were of different qualities and are applicable, depending on the quality, for use in irrigation, aquaculture and non-potable domestic uses as well as safe for disposal into water bodies. The effluents are however not safe for potable uses. 119 Majority of respondents agree that water is a scarce resource and that the Millennium Development Goal (MDG) on water cannot be achieved. Majority of people interviewed support the use of wastewater for medium contact options such as fire- fighting (71.6%), Industry (52.9%), construction of buildings (71.6%), toilet flushing (81.4%), Public parks and sports field irrigation (54.9%). Support for high contact options such as swimming pool, aquifer augmentation and laundry was low; 10.7%, 29.4% and 34.3% respectively and this is because respondents consider the treated water to be detrimental to health. Respondents supported the idea of wastewater reuse for reasons of water conservation and minimization of dependency on treated water whilst environmental protection ranked as the least frequent response. Education is needed to sensitize the public on treatment and use of wastewater. RECOMMENDATIONS 1. It is recommended that a strategy be put in place to reduce the electrical conductivity of the effluent discharged from the VVU Biogas facility into the mango plantation. Salt loading of the irrigated soil should be monitored periodically due to the high EC of discharged effluent 2. Plant biomass of plants used for the phytoremediation experiment should be reduced by methods such as anaerobic digestion, drying and disposed at a landfill site 3. 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Journal of Environmental protection, 2013,4, 1230-1235.( www.scirp.org/journal/jep) 132 APPENDICES Appendix one: Filtration rate through slow sand filter column WEEK RAW SEWAGE CONTROL(ml/min) EFFLUENT (ml/min) 0 733 733 1 730 732 2 729 730 3 704 726 4 698 719 5 605.5 719 6 564 711 7 553 708 8 448 705 9 431 703 10 416 701 133 Appendix two: Performance of slow sand filtration (SSF) WEEK PH TEMP (°C) TURBIDITY (NTU) EC (µs/CM) TDS (mg/l) MEAN CO NTROMLEAN CO NTRO LMEAN CO NTRO L MEAN CO NTRO LMEAN CO NTRO L 0 4.13 7.32 30.25 27 159.5 0.8 5413.5 347 2706.75 173.5 1 6.54 6.91 29.2 33.5 119 1.1 3755 345 1877.5 172.5 2 6.515 6.63 31.05 25.6 12.5 1 3398 326 1699 163 3 7.585 6.8 31.45 29.9 10.95 1 2859 355 1429.5 177.5 4 7.165 7.1 32.6 29.6 9.75 1 2813 352 1406.5 176 5 6.87 6.68 33.45 31.6 9.7 0.9 2748.5 345 1374.25 172.5 6 6.785 6.82 25.65 25.6 11.25 0.7 2692 339 1345.85 169.5 7 6.685 6.5 30.25 30.2 7.95 0.6 2579.5 334 1271.5 167 8 6.6 6.92 29.8 30.2 7.1 0.7 2573 323 1286.5 161.5 9 6.725 7.01 30 29.6 6.6 0.6 2549 318 1274.5 159 10 7.105 7.23 25.55 27.2 5.8 0.6 2452.5 312 1226.25 156 WEEK TSS (mg/l) CO LO R (PtCo) NO 3(mg/l) PO 4 (mg/l) DO (mg/l) BO D (mg/l) CO D (mg/l) CO NTRO L MEAN CO NTROMLEAN CO NTRO L MEAN CO NTRO LMEAN CO NTRO LMEAN CO NTRO LMEAN CO NTRO L MEAN CO NTRO L 0 238 8 731 7 2.65 3.5 5.47 1.44 1.935 6 35 6.2 368 256 1 221.5 6 565 5 1.7 1.3 3.55 1.14 6.1 5.5 25 4.5 288 224 2 21 6 234 4 8.45 1 3.03 1.09 5.1 4.6 21.5 0.9 240 192 3 18 6 217 4 9.4 1.3 2.81 2.49 4.25 5.3 11 0.2 176 160 4 14 5 210 4 10.7 1.5 3.35 2.54 3.7 4.5 8.5 0.2 144 128 5 11.5 4 206.5 3 8.2 1.4 3.97 2.56 3.65 5.1 7.5 0.1 96 96 6 10.5 4 199.5 0 5.65 1.2 3 1.96 3.55 6.5 5.5 0.1 64 64 7 6.5 4 199 0 4.3 0.8 2.895 1.86 4.6 6.6 4.3 0.1 64 32 8 7 4 198.5 0 4.25 0.8 2.84 1.82 5.6 6.5 2.35 0.1 64 32 9 5.5 4 196.5 1 4.3 0.6 2.705 1.76 5.7 6.3 1.25 0 32 32 10 5 3 184 0 3.4 0.6 2.54 1.62 5.75 5.9 1.05 0.1 32 32 Appendix three: Quality of effluent after treatment with Ipomoea aquatica and Pistia stratiotes for five days PH TEMP (°C) DO (mg/l) EC (µS/cm) TDS (mg/l) MEAN CONTROL MEAN CONTROL MEAN CONTROL MEAN CONTROL MEAN CONTROL RAW EFFLUENT 4.04 7.72 30.5 33.6 0.17 6.3 5365 309 2682.5 154.5 P.S treated effluent 7.87 6.76 25.1 29.9 2.2 3.1 2975 295 1488 147.5 I.A treated effluent 7.38 6.45 25.2 25.1 2.1 4.3 3122 287 1901 143.5 TSS (mg/l) COLOUR (PtCo) TURBIDITY (NTU) PO4 (mg/l) NO3 (mg/l) BOD (mg/l) COD (mg/l) MEAN CONTROL MEAN CONTROL MEAN CONTROL MEAN CONTROL MEAN CONTROL MEAN CONTROL MEAN CONTROL RAW EFFLUENT 239 6 738 21 143 4 5.6 1.7 3.2 0.5 35 6.2 368 256 P.S treated effluent 96 16 530 190 90 2.99 4.88 0.95 1 0.2 17 1.8 224 96 I.A treated effluent 315 23 718 201 147 2.18 4.7 0.2 0 0.2 16 3 192 96 134 Appendix Four: Weekly variations in water quality parameters after during treatment with Ipomoea aquatica PH TEMP (°C) DO (mg/l) EC (mg/l) TDS (mg/l) WEEK MEAN CONTROL MEAN CONTROL MEAN CONTROL MEAN CONTROL MEAN CONTROL 0 4.14 7.72 30.5 33.6 0.17 6.3 5365 309 2683 154.5 1 7.38 6.45 25.2 25.1 2.1 4.3 3122 287 1901 143.5 2 7.22 6.06 29.1 29 3.5 4.8 3105 276 1552.5 138 3 7.77 6.75 32 32.2 1.9 5.5 3075 255 1537.5 127.5 4 7.65 7.19 25.8 22.7 4.1 6.7 2030 231 1015 115.5 TSS (mg/l) COLOUR (PtCo) TURBIDITY(NTU) (NTU) PO4 (mg/l) NO3 (mg/l) BOD (mg/l) COD (mg/l) WEEK MEAN CONTROL MEAN CONTROL MEAN CONTROL MEAN CONTROL MEAN CONTROL MEAN CONTROL MEAN CONTROL 0 239 6 738 21 143 4 5.6 1.7 3.2 0.5 35 6.2 368 256 1 315 23 718 20.1 147 2.18 4.7 0.2 0 0.2 16 4.3 192 160 2 35 10 664 19 20.2 5.4 3.9 0.1 3.4 0 15.1 3.2 160 128 3 70 3 533 15.2 54 1.8 5.64 1.2 1.4 0.8 18 1.8 96 64 4 31 15 334 10.4 12.9 6.3 8.24 7.04 33.6 0.3 4.1 0.9 64 32 135 Appendix Five: Questionnaire UNIVERSITY OF GHANA INSTITUTE FOR ENVIRONMENT AND SANITATION STUDIES (IESS) QUESTIONNAIRE One of the pressing environmental problems in the world today is water scarcity. It is increasingly becoming important to seek alternative sources of water to supplement the available water. One attractive option is wastewater treatment and reuse. This questionnaire is designed to get your views on reuse of wastewater. This questionnaire is solely for academic purposes and confidentiality is assured. Please answer the following questions regarding the treatment and reuse of wastewater. (A) Demographic background (Please tick) Gender M Age 18-30 F 31-40 41-50 51-60 Above 60 Highest level of education (a)Primary (b)JHS © SHS (d)Tertiary (e)Other (Please specify) Marital status single Married Widowed Number of children…………………………………………………………… Place of residence…………………………………………………………… 136 Monthly Income (GH¢) (Please tick) Below 100 100-300 500-1000 Above 1000 (B) Environmental perceptions 1. How do you get water for domestic use? (Please tick as many options as possible) (a)Treated tap water (b)Borehole © River/stream (d)Rain water harvesting (e) Other (please specify)……………………………….. 2. Do you have regular access to water? Yes/ No 3. If yes, how regular is your supply of water? (a) Daily (b) Once a week (c) Once a month (d) Other (please specify)………………………………………. 4. Do you consider water to be a scarce resource? Yes/No 5. What are some of the causes of water scarcity you know about? (Please tick as many options as applicable) (a) Water pollution (b) Drought (c) Depletion of aquifers (d) Others (please specify)…………………………………………………………………… ……………………………………………………………………………… ……………… 6. What do you understand by the term “wastewater”? (a) Any dirty and unclean water (b) Water which has already been used 137 (c) Water which cannot be used any longer (d) Others (please specify)…………………………………………………………………… ……………………………………………………………………………… ……………. 7. What are some of the sources of wastewater you know about? (Please tick as many options as applicable) (a) Domestic washing (b) Sewage © Washing bay (e) Industries (f) Rainfall run off (g) Others (please specify) ……………………………………………………………………………… ……………………………………………………………………………… ……………… 8. Do you generate wastewater? Yes/No 9. If Yes, how do you generate wastewater? (a) Domestic washing (b) Work activities (c) Others (please specify)…………………………………………………………………… ……………………………………………………………………………… ……………… 10. What do you do with wastewater generated at home? (Please tick as many options as applicable) (a) Throw it away (b) Flushing toilet (c) Irrigation (d) Others (please specify)…………………………………………………………………… ……….. 138 11. Do you have access to a toilet facility? Yes/No If yes, indicate (by ticking) which toilet facility you have access to. (a) Water closet (b) KVIP (c) Pit latrine (d) Open defecation 12. Do you have any idea about how the faecalmatter generated by humans is disposed off? Yes/ No 13. If yes, please indicate (by ticking), the methods of disposal you know about (a) Dumping into the sea (b) Irrigation of crops (c) Treatment to produce compost (d) Treatment to produce Biogas (e) Others (please specify)………………………………………………………………………… ………………………………………………………………………………… ………………………………………………………………………………… ………………………. 14. Are you familiar with the concept of wastewater reuse? Yes /No 15. Do you support the idea of wastewater reuse? Yes/No 16. If yes, what are your reasons for supporting wastewater reuse? (Please tickas many options as applicable) a. Wastewater reuse is good for the environment b. Wastewater reuse conserves water c. Wastewater reuse will minimize dependency on treated water 17. Do you know of any health risks associated with wastewater reuse? Yes/No 18. If yes, please indicate (by ticking) the health risks you know about (a) Cholera (b) Bacterial infections (c) Diarrhoea (d) Others (please specify)…………………………………………………………………… ……………………………………………………………………………… ……………. 19. Do you know how the health risks mentioned above can be minimized or prevented? Yes/No (a) By treating water before use 139 (b) Avoiding the use of wastewater (c) Others (please specify)……………………………………………………………………………… ……………………………………………………………………………………… ………………. 20. The Millenium Development Goal 7 targets that the proportion of the population without sustainable access to safe drinking water and basic sanitation be halved by the year 2015. Can this be achieved? Yes/No 21. Please indicate ( by ticking) whether you support the following options for wastewater reuse Wastewater Strongly Agree Not disagree Strongly reuse option agree sure disagree Irrigation of food crops Fire fighting Industry Construction of buildings Toilet flushing Public park/sports field irrigation Commercial car wash Swimming pool Aquifer augmentation General cleaning and laundry 22. Would you recommend wastewater use to your community? Yes/No 140