Biosolids reduction by the oxic-settling-anoxic process: Impact of sludge interchange rate

Abstract

. D. (2016). Biosolids reduction by the oxicsettling-anoxic process: impact of sludge interchange rate. Bioresource Technology, Biosolids reduction by the oxic-settling-anoxic process: impact of sludge interchange rate AbstractThe 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 0-22%. 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 were unaffected by SIR.

Incorporating the oxic‐settling‐anaerobic (OSA) process into an anoxic–oxic system for sewage sludge reduction and nutrient removal

“…This reduction has also been observed by other authors . Moreover, as can be seen from the reported values, the nitrate concentration in the effluent from Plant B was always lower than in Plant A, as the inclusion of an anoxic step in the biological process led to partial consumption of nitrate as an electron acceptor for the degradation of the substrate . The difference in nitrate concentration between the plants during the OSA phases was especially noticeable for Phase II.…”

Evaluation of sludge reduction of three metabolic uncouplers in laboratory-scale anaerobic–anoxic–oxic process

“…Sewage sludge is an undesired by-product of wastewater treatment, which needs to be treated, and otherwise, may have a significant environmental impact (Li et al 2015;Guo et al 2013;Semblante et al 2016). In Europe, the annual production of sewage sludge accounted for more than 10 million tons in 2010 and is expected to increase to 13 million tons in 2020 (Paul and Debellefontaine, 2007).…”

Effects of sludge retention time on oxic-settling-anoxic process performance: Biosolids reduction and dewatering properties

“…The occurrence of denitrification largely depends on the capacity of the preceding nitrification to produce nitrate, and therefore the efficiencies of the two reactions were related. In a previous OSA study, http://dx.doi.org/10.1016/j.biortech.2016.07.061 denitrification efficiency in the external aerobic/anoxic reactor declined due to insufficient biodegradable COD (Semblante et al, 2016). In this study, the soluble COD/nitrate-nitrogen ratio at different external reactor SRTs were similar to each other (Table 3) and were consistently close to the theoretical value of 3.7 (Chiu & Chung, 2003), which suggests that soluble COD would have been available for denitrification throughout the operation period.…”

“…A previous study have demonstrated that sludge reduction in this particular OSA configuration ( Figure 1) is due to the destruction of volatile solids in the external anoxic reactor, followed by the conversion of destroyed solids into inert products via nitrification/denitrification in the external aerobic/anoxic reactor (Semblante et al, 2016). In this study, the nutrient concentration ( Figure 5) and ORP ( Figure 6) of the external reactors were monitored to provide insight into the effect of SRT on the aforementioned biochemical reactions.…”