Simultaneous Organics and Nutrients Removal from Domestic Wastewater in a Combined Cylindrical Anoxic/Aerobic Moving Bed Biofilm Reactor

The aim of present study was to design and construct an continuous up-flow pilot scale Moving Bed Biofilm Reactor (MBBR) which is consists of combined cylindrical Anoxic/Aerobic MBBR in nested form with anoxic/aerobic volume ratio equal to 0.16 to treated 4 m3/days of domestic wastewater in Chongqing city at Southwest China. The treatment must be satisfactory to meet with grade B of discharge standard of pollutants for municipal wastewater treatment plant in China (GB/T18918-2002). Kaldnes (K1) media was used as a carrier in both reactors at a media fill ratio equal to 50%. The reactors was operated under the Anoxic/Oxic (An/O) process which must meet stringent TN limits without sludge returning into the system and only an internal recycling was performed from aerobic to anoxic reactor. After developing the biofilm on the media, reactor was operated at 3 different Hydraulic Residence Time (HRT) ranging from 4.95 to 8.25 h. During operation the internal recycle ratio to eliminate nitrogen compounds were 100% of inflow rate and the average Dissolved Oxygen concentration (DO) in aerobic and anoxic MBBRs were 4.49 and 0.16 mg/L, respectively. The obtained results showed that the HRT of 6.2 h was suitable for simultaneous removal of COD, NH4+-N, TN and TP. In this HRT the average removal efficiencies were 93.15, 98.06, 71.67 and 90.88% for COD, NH4+-N, TN and TP, respectively.