| Article ID | Journal | Published Year | Pages | File Type |
|---|---|---|---|---|
| 679029 | Bioresource Technology | 2016 | 7 Pages |
•Effect of SIR on OSA was studied using unsettled and settled sewage.•SIR of 11% by volume achieved the highest sludge reduction.•OSA performance was linked to nitrification/denitrification in the external reactor.•Sludge reduction by OSA was more evident at higher influent sCOD.•Effluent suspended solids and nutrients were unchanged with all SIRs studied.
The impact of sludge interchange rate (SIR) on sludge reduction by oxic-settling-anoxic (OSA) process was investigated. The sludge yield of an OSA system (a sequencing batch reactor, SBR, integrated with external anoxic reactors) was compared to that of a control (an SBR attached to a single-pass aerobic digester). SIR (%) is the percentage by volume of sludge returned from the external reactor into the main bioreactor of the OSA, and was varied from 0% to 22%. OSA achieved greater sludge reduction when fed with unsettled sewage (sCOD = 113 mg/L) rather than settled sewage (sCOD = 60 mg/L). The SIR of 11% resulted in the highest OSA performance. At the optimum SIR, higher volatile solids destruction and nitrification/denitrification (i.e., conversion of destroyed volatile solids into inert forms) were observed in the external anoxic and intermittently aerated (i.e., aerobic/anoxic) reactors, respectively. Denitrification in the aerobic/anoxic reactor was inefficient without SIR. Effluent quality and sludge settleability of the main SBR were unaffected by SIR.
