Sequential aerobic-anaerobic treatment of municipal wastewater: effect of different parameters
By: Syeda Amber Hameed, Safia Ahmed, Naeem Ali
Key Words: Municipal wastewater, Sequential aerobic-anaerobic treatment, Dual treatment, Wastewater treatment, Biological treatment
Int. J. Biosci. 9(4), 182-199, October 2016.
Sequential application of aerobic and anaerobic system for domestic wastewater treatment experiences certain limitations under low temperature regime and further requires optimization of exogenous inoculum size and treatment time. In order to address the aforesaid issues, a sequential aerobic-anaerobic digester was locally designed and operated for 8-14 days for wastewater treatment. Overall, the treatment efficiency varied from 92-100 % in terms of biochemical oxygen demand (BOD), chemical oxygen demand (COD), turbidity and NO2-N at 25ºC (non-significantly differed at 45ºC). Increase in aerobic retention time from 1-3 days helped improvement in treatment efficiency by 5-20 % in most of the parameters. However, a slight increase in COD (94 – 97%) and BOD (95- 97%) removal was observed when temperature raised from 25 to 45ºC. Whereas, almost 60% decrease in treatment efficiency was observed in term of BOD and COD removal when temperature decreased from 45-5ºC.The low temperature treatment efficiency of the whole system was recovered to maximum within 6-8 days when reactor was bioaugmented with activated sludge (amount/L). Nitrifying bacteria including Nitrososmonas sp. and Nitrobacter sp were enriched and identified from wastewater and activated sludge using specific activity analysis on different concentration of substrates. The specific activity verification was confirmed with their oxidizing capability of utilizing ammonium nitrogen and nitrite nitrogen. Thus, integrated aerobic and anaerobic system in sequence showed its feasibility to treat municipal wastewater under low to moderate temperature regimes.