Keywords: effluent quality, fixed-film processes, organic removal, wastewater treatment, water reuse, secondary biological treatment, aerobic submerged fixed film, anoxic, Dubai, activated sludge, water quality, irrigation, Arabian Gulf
Upgrading secondary biological treatment of wastewater using anoxic/aerobic attached growth systems for effluent quality improvement
A pilot plant was constructed and operated using both Aerobic Submerged Fixed Film (ASFF) and Anoxic/Aerobic Submerged Fixed Film (A/ASFF) processes at different loading rates in the range of 0.03–0.3 g BOD.g-1 BVS.d-1 corresponding to the Hydraulic Retention Times (HRTs) in the range of 0.7 to 8 hr. The results obtained revealed that both the ASFF and the A/ASFF processes are viable options to upgrade the activated sludge process for combined organic and ammonia removal with minimal excess sludge production. High removal efficiencies of up to 98% for BOD, 75% for COD and 97% for ammonia were obtained with both processes over a wide range of loading rates, but the A/ASFF process appears to be more capable of maintaining a stable and efficient treatment at higher loading rates. The treated effluent quality obtained from either upgrading process is considerably better than that achieved by the activated sludge process and satisfies the water quality requirements for reuse in irrigation, thus tertiary filtration may not be needed.