| Abstract: | The performance of a multistage passively aerated biological filter (PABF) packed with Nonwoven polyester fabric (NWPF) for municipal wastewater treatment was investigated under different operating conditions. The system was operated at different hydraulic retention times (HRTs) of 2.3, 1.72 and 1.38 h and corresponding to organic loading rates (OLRs) of 1.77, 2.15 and 2.9 kg BOD/m3. d. Increasing HRT and decreasing OLR, increased dissolved oxygen (DO) and consequently increased the removal rate of organic matters (87%), suspended solids (95.8%) and ammonia (88%). Profile results from different compartments showed that the major part of organic and suspended matters was removed in the upper layers of the system, whereas most of the suspended solids were trapped, while the nitrification process took place in the lower part of the PABF system because of the increase in DO concentrations. The results proved the advantage of using NWPF. It has pleated and rough surface which retain more biomass compared with plain surface. Excess biomass produced from PABF was negligible compared to conventional treatment systems. |
