Efficiency and mechanism of ferric salt enhanced biological phosphorus removal
- SUN Cuiping, ZHOU Weizhi, ZHAO Haixia
JOURNAL OF SHANDONG UNIVERSITY (ENGINEERING SCIENCE). 2015, 45(2):
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An efficient phosphorus (P) removal bacterium strain was screened from deep-sea bacteria, and phosphorus removal efficiency and mechanism by iron enhanced biological treatment were studied in the high salinity synthetic wastewater. The effects of molar ratio Fe(III)/P, initial pH on phosphorus removal and kinetics of iron enhanced biological phosphorus removal were investigated by batch tests, and the surface morphology of bacteria was studied by SEM-EDS (scanning electron microscopy-energy dispersive X-ray spectroscopy). Results showed that the phosphorus removal efficiency of iron enhanced biological treatment was high and stable at more than 95% compared to those of independent iron and biological treatment. Removal efficiency of phosphorus reached the maximum of 98.5% with molar ratio of Fe(III) and P being 1, which increased 30% than that of the biological treatment, whereas the maximum phosphorus removal was 90% with molar ratio of Fe(III) and P ranging from 2 to 3 by independent iron treatment. Phosphorus removal was mainly ascribed to bacterial growth and aided by iron, and pH was kept stable at about 7.2 when molar ratio of Fe(III) and P being not more than 1. Phosphorus removal was mainly by chemical precipitation with molar ratio of Fe(III) and P being more than 1 because that the pH reduced to 5.5 or even lower by Fe(III) hydrolysis and significantly influenced bacterial growth. Phosphorus removal was kept at above 95% at pH of 6～9 with molar ratio ofFe(III) and P being 1. The dynamic pseudo-first-order model could fit the biological phosphorus removal process well, and the pseudo-second-order model could well describe the iron enhanced biological phosphorus removal without phosphorus releasing for a long time. Except the uptake of part of the phosphorus by bacterial growth and bio-sorption by extracellular polymeric substance, the hydroxyl phosphate iron complex compound and iron phosphorus precipitation induced by bacterium also contributed to the phosphorus removal.