Up-flow sludge blanket filtration [USBF]: an innovative technology in activated sludge process

A new biological domestic wastewater treatment process, which has been presented these days in activated sludge modification, is Upflow Sludge Blanket Filtration [USBF]. This process is aerobic and acts by using a sludge blanket in the separator of sedimentation tank. All biological flocs and suspended solids, which are presented in the aeration basin, pass through this blanket. The performance of a single stage USBF process for treatment of domestic wastewater was studied in laboratory scale. The pilot of USBF has been made from fiberglass and the main electromechanical equipments consisted of an air compressor, a mixing device and two pumps for sludge return and wastewater injection. The wastewater samples used for the experiments were prepared synthetically to have qualitative characteristics similar to a typical domestic wastewater [COD=277 mg/l, BOD5=250 mg/l and TSS=1 mg/l]. On the average, the treatment system was capable to remove 82.2% of the BOD5 and 85.7% of COD in 6 h hydraulic retention time [HRT]. At 2 h HRT BOD and COD removal efficiencies dramatically reduced to 50% and 46.5%, respectively. Even by increasing the concentrations of pollutants to as high as 50%, the removal rates of all pollutants were remained similar to the HRT of 6 h