Comparison of specific oxygen uptake rates of two beach-scale activated sludge sequencing batch reactors operated using different operating strategies

Performance of sequencing batch reactor (SBR), a time-oriented periodic process activated sludge system, like any other biological wastewater treatment system depends heavily on the proper design of the aeration system. Therefore, the importance of accurate determination of the oxygen demands of the biological system and oxygen capability of the aeration equipment in designing a SBR system cannot be overemphasized. A common approach used in determination of biological oxygen demand and estimation of capacity of aeration equipment is to conduct bench-scale and/or pilot-scale studies. Operating strategy is one of the parameter that can influence the oxygen uptake rate and hence, the design of aeration equipment of the SBR. This paper presents the results of laboratory studies on oxygen uptake rates of two bench-scale activated sludge sequencing batch reactors fed with synthetic domestic wastewater of the same characteristics but operated using different operating strategies. While the influent of one reactor was neither aerated nor mixed, the influent of the other reactor was aerated and mixed during the FILL cycle. The determined values of oxygen uptake rate during the endogenous reaction phase (between 0.1054 and 0.3564 mgO2/L.minute) and concentrations of mixed liquor suspended solids (between 1183 and 1957 mgMLSS/L) are comparable to those reported elsewhere in literature. Results of specific oxygen uptake rate of the reactors were compared statistically by conducting t-tests to establish the effects of operating strategy on oxygen uptake rate. According to t-test results, mean values of SOUR for all reaction phases (endogenous, peak carbonaceous plus endogenous and peak carbonaceous plus nitrification) were found to be statistically insignificant (α = 0.05). Therefore, t-test results suggest that operating strategy may not have appreciable effects on oxygen uptake rate of biological system and design of aeration equipment for SBRs in this particular case.Journal of Building and Land Development Vol. 13 (1) 2006: pp. 13-2