| Abstract: | The performance of an on site sewage treatment and disposal system consisting of a septic tank, a gravel filter, a sand filter and soil absorption trenches operated alternatively, was studied in relation to organic matter and nitrogen removal efficiency. The system was simulated with the aid of a laboratory scale model. BOD5 and SS removal efficiencies averaged 92.9 and 93.4% respectively. Substantial removal of nitrogen (up to 70%) was achieved due to nitrification followed by denitrification. Removal efficiencies were found to depend on the compaction characteristics of the filter media and the soil, the hydraulic loading applied and the flow conditions (saturated/unsaturated). The results indicate that the system under consideration is a feasible alternative for on site treatment and disposal of domestic sewage. |
