Treatment of synthetic domestic wastewater by integrated aerobic/anoxic bioreactor (IAAB)

An integrated aerobic/anoxic bioreactor with total liquid volume of 180 L was utilized for the treatment of synthetic domestic wastewater. Bioreactor performance was monitored by the removal of biochemical oxygen demand (BOD). Organic loadings simulating low and medium strength domestic wastewater with a BOD concentration of 110 and 235 mg/L were used to evaluate the bioreactor in stages 1 and 2 respectively. Hydraulic retention time (HRT) was varied between 12 and 7.2 days. Biomass from a sewage treatment plant was used as seed sludge. BOD removal was monitored from the aerobic, anoxic and effluent compartments of the bioreactor every two days. Results at HRT of 12 days show that the bulk of organic matter removal was prominent in the aerobic compartment with an effluent concentration of 28.7 and 30.5 mg/L at the steady states of stages 1 and 2 respectively. The anoxic compartment showed slight BOD removal with effluent concentration of 24.2 and 27.7 mg/L at the steady states of stages 1 and 2 respectively. The BOD concentration in the effluent compartment was 4.5 and 14.5 mg/L at the steady states of stages 1 and 2. BOD removal took a downtrend when HRT was decreased from 12 to 7.2 days in the aerobic and anoxic compartments, but was constant for the effluent compartment at steady state. Ammonia, nitrate, COD and MLVSS were all monitored. Ammonia, nitrate and COD removal were about 93, 83 and 92 respectively. Growth of biomass (MLVSS) was more prominent in the aerobic compartment. This study demonstrates that an IAAB has the potential to treat wastewater.