Influence of dissolved oxygen on phosphorus removal by polyphosphate-accumulating organisms biofilm: Performance and metabolic response

Abstract

The present study focused on investigating the effect of dissolved oxygen (DO) concentration on phosphorus (P) transformation and metabolism in the polyphosphate-accumulating organisms (PAOs)-biofilm system. Two biofilm sequencing batch reactors (BSBRs) with high-DO (6 mg/L, BSBR-H) versus low-DO (2 mg/L, BSBR-L) concentrations were typically operated for 90 days. Collectively, the high DO concentration in aerobic phase would force PAOs to preferentially and rapidly perform phosphate metabolism and be beneficial for them to establish the dominant ecological niche. Clear differences in stoichiometry and kinetics indicated a glycolytic pathway in BSBR-L, while it shifted to polyphosphate hydrolysis in BSBR-H. The expression of functional genes suggested that the high-affinity P transport system was mainly responsible for P transformation in BSBR-H while the low-affinity P transport system was accountable for BSBR-L. Moreover, the BSBR-H showed relatively higher abundances of Pseudomonas while Tetrasphaera were the most dominant PAOs in BSBR-L. Dechloromonas contributed substantially to poly-P metabolism by occupying the largest proportion of ppk1/2 and ppx genes in both BSBRs.