Biosand Filtration as A Green Approach to Septic Tank Effluent Management in Accra Technical University

Abstract

Introduction: Sewage and household effluents at Accra Technical University (ATU), Ghana have been discharged into the ocean for years. This degrades environmental media and is detrimental to ecological systems. The institution also lacks adequate water for non-edible purposes. The Biosand Filter (BSF) is an innovation on the slow sand filter which has found use in preventing the discharge of raw sewage into the environment. The study aimed to test the performance of a BSF on sewage tank effluent and assess the suitability of the filtrate for non-drinking purposes. Method: Three modified interconnected BSF were constructed on-site, with last filter connected to a storage tank. The modification was the provision of an additional media (charcoal) in the second barrel. Samples were collected of raw STE (pre-filtrate) and after passing through the BSF (post-filtrate). Samples were analysed for physical and microbiological parameters at designated laboratories. Measured values of the parameters in pre- and post-filtration samples were compared with EPA (Ghana) reference values. The removal efficiency was determined as the difference between pre- and post-filtrate parameters and expressed as a percentage of the pre-filtrate. Results: Most of the effluent parameters from the PBSF were within the EPA standards, while others were unacceptable. However, the ability of the BSF to effectively improve effluent quality was demonstrated by removing excess quantity of nutrients and coliforrns varied significantly (P<O.05). Nitrogen (83.3%), Phosphorus (89.5%), TSS (71.3%), TDS (66.2%), Total coliform (99.9%), Faecal coliform (99.7%) and E. coli (97.6%). Conclusion: BSF is effective for upgrading physical and microbial quality of sewage at household and institutional level, prior to discharge in the environment. It produced a filtrate that meets EPA standards for irrigation of non-edible crops. Keywords: wastewater, sewage, effluent, biosand filter, Ghana, liquid waste.