Integrated Anaerobic and Aerobic Processes for Treatment of Municipal Wastewater

In this study, integrated anaerobic and aerobic treatment processes for municipal wastewater treatment were investigated for its feasibility to replace the existing conventional activated sludge process. Three types of anaerobic systems – anaerobic sludge blanket, anaerobic sequencing batch reactor and anaerobic filter, as the pretreatment step were studies. High solids and organics removal efficiency was observed during the start-up period at a hydraulic retention time (HRT) of 16 h, as well as during 6 h HRT operation. The UASB was found to require the shortest start-up time (80 days) and it produced the highest amount of methane gas (0.16 L/(g tCOD removed) during start-up and 0.13 L/(g tCOD removed) during 6 h HRT operation). However, it was a challenge to operate the UASB due to sludge floatation problems encountered during the start-up period when the HRT was 16 h. The performance characteristics of conventional activated sludge system and membrane bioreactor were also assessed to evaluate their effectiveness for treating the effluent of the UASB system. Both aerobic systems were able to produce an excellent final effluent with quality meeting that of the secondary effluent discharge standards. However, the membrane bioreactor was noted to be a better option as it offered the advantages such as smaller footprint and higher removal efficiencies.