ANAEROBIC-ANOXIC-AEROBIC PROCESS WITH RECYCLING AND SEPARATED BIOMASSFOR ORGANIC-CARBON AND NITROGEN REMOVAL FROM WASTE-WATER

A study was made of an anaerobic-anoxic-aerobic process with recycling and different biomasses to maximize the.removal of organic material a nd nitrogen from domestic wastewater by varying the recycling ratio be tween the aerobic and anoxic reactors. The anaerobic and anoxic reacto rs were UASB type and the aerobic was submerged filter packed with PVC tubes. With a 3:1 recycling ratio, 80% of the TOCs, 62% of N and 90% of TSS were removed. The concentration of TSS in the treated water was lower than 20 mg L-1 (12 mg TSS L-1) making unnecessary the use of fi nal settlers. The concentration of TOCs and N-NH4 in the system efflue nt operating with a 3:1 ratio was 7 and 4.6 mg L-1, respectively. The proposed system may be used in treatment schemes designed to provide w ater for reuse or discharge at low operational cost.