Removal of Phosphorous by Polyphosphate-accumulating Microorganisms under Different Substrates Conditions

摘要

Due to an increased eutrophication of rivers, lakes and coastal waters, the interest in removing phosphorus from municipal wastewaters has increased dramatically in recent years. However, one of the wastewater's character, low C/P, often leads to the failure of enhanced biological phosphorus removal process (EBPR). In this work, A three-factor and three-level orthogonal experiment was designed to study the effect of the variety of added carbon source, the quantity of added carbon source and the quantity of added phosphate on the behavior of EBPR process. The L9_3_4 orthogonal tests were carried through 3 months in a 10L SBR reactors, while the municipal wastewater was used as the basic carbon source. During this process, the variations of PO_3 _(-4)-P, COD, sludge characteristics and predominant bacterial group were investigated to determine the phosphorus removal ability of EBPR process under different carbon source conditions. The results testified that the three factors could affect the phosphorus removal rate effectively although they could not influence the phosphorus uptake and phosphorus release apparently. The variety of carbon source was found to be the most important factor, and glucose was the best carbon source compared with sodium acetate and sodium propionate. The phosphorus removal rate raised along with the increase of the quantity of added carbon source(from 100mg/L to 300mg/L) and decrease of the quantity of added phosphate source(from 21mg/L to 5mg/L), and the phosphate removal rate obtained its highest value, 99.17%, when 100mg/L glucose and 19mg/L phosphate were added respectively(C/P averaged about 45 ). Fluorescence in situ hybridization (FISH) technique testified the existence of a large amount of poly-phosphate accumulating organisms in this biomass. Based on this, raising the C/P by increasing the quantity of added glucose leads to the deterioration of EBPR due to the enrichment of glycogen accumulating organisms. Only by involving a large amount of sodium acetate (C/P ＞ 50) could the phosphorus removal be achieved efficiently. So the variety of the carbon source and a proper C/P is crucial for bio-treatment of high phosphorus concentration wastewater.