Feasibility study of the integrated septic tank with trickling filter for the municipal wastewater treatment in small communities

In response to increasing water scarcity and the pressing need for cost-effective and sustainable wastewater solutions, particularly in small communities, this study investigates the performance and feasibility of a simple, low-cost decentralized hybrid system combining a septic tank with a trickling filter. The system was designed to treat domestic and municipal wastewater with the goal of promoting safe reuse in water-stressed regions. A pilot-scale septic tank-trickling filter unit was constructed and tested using synthetic wastewater, raw sludge, and real municipal wastewater. Key performance indicators included chemical oxygen demand (COD), biochemical oxygen demand ( $${BOD}_{5}$$ ), total nitrogen (TN), total phosphorus (TP), ammonia nitrogen ( $${NH}_{3}-N$$ ), phosphate ( $${PO}_{4}^{2-}$$ ), total suspended solids (TSS), and hydraulic retention time (HRT).Under optimized conditions with synthetic wastewater, the system achieved removal efficiencies of 94% for COD, 83% for $${NH}_{3}-N$$ , and 63% for $${PO}_{4}^{3-}$$ at a 24-hour HRT. When tested with actual municipal wastewater over two weeks, the system showed removal efficiencies of 73.8% for COD, 77% for BOD₅, 78% for TN, 58% for TP, and 95% for TSS. These results confirm that integrating a conventional septic tank with a rock-bed trickling filter provides a reliable and efficient approach to decentralized wastewater treatment. The treated effluent met environmental standards, supporting its potential reuse in irrigation. This study highlights the practicality and scalability of simple treatment technologies as viable solutions for rural and underserved communities facing increasing water stress.