Factors Affecting BPR Performance

The enhanced biological phosphorus removal (EBPR) process plays an increasingly important role in controlling eutrophication of natural waters. But EBPR system is not stable.Using SBR to investigate the impact of environmental factors (TOC/P, pH, DO) on biological phosphorus removal system to determine their effects on capability and stability of system. Optimal micro-entironment of biological phosphorus removal was sought: pH range from 6.5 to 7.5, DO under 0.35 in anaerobic stage and 2 to 4 in aerobic stage, TOC/P range from 15 to 20. Supplied with acetate as the role substrate, to research phosphorus release situation while pH changed from 5.5 to 8.0. Low pH had inhibition on phosphorus release. The higher pH in SBR, the greater amount of phosphorus released. In a whole running cycle, phosphate concentration raised in the anaebobic stage and decreased in the aerobic stage while pH behaved oppositely. Anaerobic condition had a great effect on anaerobic phosphorus release. The lower DO, the more phosphorus released in the anaerobic stage. High DO in aerobic stage would accelerate bacteria to consume themselves, detroy the structure of sludge and affect anaerobic condition in the next cycle. Phosphate removal reached the greatest level when the ratio of TOC/P was between 15~20. The phosphorus-accumulating organisms were the dominant microorganisms and less TOC was required for the same amount of phosphorus removal when system was TOC limiting, when the TOC/P was above 20, the amount of common heterotrophic bacteria increased.Lower pH had more influence on the system, while impact of high DO in anaerobic stage was easy to recover.Comparasion of BPR system fed on three kinds of carbon source validated acetate was the best carbon source of biological phosphorus removal, and optimal micro-entironment found in acetate system was effective to BPR system fed with other substrates.