Effects of chemical phosphate precipitation in the sidestream process on biological phosphorus removal at the anaerobic stage in an anaerobic—aerobic sequencing batch reactor

Abstract

This study investigates the effects of chemical phosphate precipitation on the performance of a sequencing batch reactor (SBR) operated in anaerobic—aerobic mode. Supernatants enriched with 50% phosphorus were removed from the SBR (i.e. sidestream) system at the end of the anaerobic stage and were placed into a reaction-sedimentation basin to recover the phosphorus. Results indicate that phosphorus removal efficiency increased from 95.26 to 97.22% during the first 40 d and then declined over the next 20 d. Intracellular polyphosphate (poly-P) storage remained low during sidestream stripping. The sludge was not dominated by organisms that accumulate poly-P, as confirmed by the low anaerobic phosphorusrelease/HAcuptake ratios, the phosphorus content in the sludge, and the high ratios of volatile suspended solids of mixed liquor to suspended solids of mixed liquor. These results imply the possibility of changes in population structure given the low level of intracellular poly-P storage during long-term stripping. Intracellular poly-P content may be considered a factor that affects biological phosphorus removal in the future work.