The operational strategy of intermittent cycle extended aeration system intreating sewage

Intermittent Cycle Extended Aeration System (ICEAS) offers advantages for t reating sewage; such as easy operation, process flexibility, and low capita l cost. A laboratory-scale study was made with synthetic-domestic wastewate r (COD=300 mg dm(-3); BOD=210 mg dm(-3)) to investigate appropriate conditi ons for reduced operating cost. The results from this study indicated that the maximum hydraulic loading and organic loading were 3.5m(3)m(-3)d(-1) an d 0.735kg BOD m(-3)d(-1) respectively. The BOD and COD of effluent were 15. 5 mg dm(-3) and 29.6 mgdm(-3) for the cycle time and aeration time of 3.4h and 2.65h. It was not necessary to supply external artificial substrates in the reactor to deal with low wastewater flow that caused the starvation of sludge. Specific oxygen uptake rate (SOUR) was used as the index of microb ial activity. The study indicated that the microbial activity could be rest ored (SOUR=20.5mgg(-1) MLVSS h(-1)) after 5-6 days of cultivation when the sludge was deprived of substrate for 17 days. (C) 1999 Society of Chemical Industry.