SEQUENCING BATCH REACTORS: A REVIEW

Sewage treatment using the activated-sludge process evolved from the fill-and-draw system which was developed by Ardern and Lockett in 1914; the sequencing batch reactor is a modern development of this system. Its success is due to modern technology particularly the programmable logic controller which controls operational sequences. The process has a single rectangular reaction tank where the various sequences of wastewater fill and aeration, activated-sludge settlement and effluent decanting are carried out. This paper reviews the sequencing batch reactor compared with conventional activated sludge, and explains (a) the similarities and differences, (b) the circumstances in which the system is likely to be cost competitive, and (c) modifications that could increase the effectiveness of sequencing batch reactor systems in the future.