Microbial effects on phosphorus release in aquatic sediments

Microbial effects on phosphorus release were studied for the sediments of Tianjin source water by controlling DO and pH. The results show that: (1) In sterilised water, phosphorus began to release when pH = 9.1 and the stable release rate was 9.51 mg/(d·m²). It indicates that microorganisms may utilise anaerobic iron respiration to release Fe-P. (2) With unsterilised water, phosphorus release rate is 2.14 mg/(d·m²) when pH = 6.5, 8.60 mg/(d·m²) when pH is uncontrolled, and gets to 8.51 mg/(d·m²) when pH = 9.1. This indicates that microorganisms can dissolve insoluble phosphates to accelerate the ion exchange of OH⁻ and PO₄³⁻, which are derived from iron-bound ortho-P and aluminium-bound ortho-P.