Effect of phosphate releasing in activated sludge on phosphorus removal from municipal wastewater

Jie Ge , Xiaoguang Meng , Yonghui Song , Amalia Terracciano


Received 2017-06-05,Revised 2017-09-08, Accepted 2017-09-11, Available online 2017-09-20

Volume 67,2018,Pages 216-223

Aluminum and ferric salts are commonly used in municipal wastewater treatment plants (WWPTs) for phosphorus (P) removal. In this study, on-site jar tests were conducted to determine the removal of different P species from the fresh samples in the presence and absence of activated sludge (AS) with different doses of alum, poly-aluminum chloride, and ferric chloride at different pH. The soluble P (SP) concentration in the samples was about 0.63 mg/L. When the mixed liquor containing AS was treated with 8 mg/L of Al, SP could be reduced to 0.13 mg/L, while it was reduced to 0.16 mg/L with only 1 mg/L of Al after sedimentation removal of AS from sample. Chemical analysis determined that AS contained 59.8 mg-P/g-TSS and 43.8 mg-Al/g-TSS and most of the P was associated with the aluminum hydroxide. We discovered that the phosphate in the AS could readily be released from it, which was mainly responsible for ineffective removal of P to low levels in mixed liquor even with very high alum dose. This study provides new insight into the behavior and fate of P in the wastewater treatment plants that use alum to enhance P removal in the final effluent.

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