Phosphate recovery from anaerobic digester effluents using CaMg(OH)_4  

作　　者：Xueyu Liu Zhonghou Xu Jianfeng Peng Yonghui Song Xiaoguang Meng 

机构地区：[1]State Key Laboratory of Environmental Criteria and Risk Assessment, Chinese Research Academy of Environmental Sciences [2]College of Water Sciences, Beijing Normal University [3]Center for Environmental Engineering, Stevens Institute of Technology

出　　处：《Journal of Environmental Sciences》2016年第6期260-268,共9页环境科学学报（英文版）

基　　金：supported by the National Natural Science Foundation of China (No. 51078339)

摘　　要：Dolomite lime（DL）（CaMg（OH）4） was used as an economical source of Mg^2＋for the removal and recovery of phosphate from an anaerobic digester effluent of a municipal wastewater treatment plant（MWWTP） wastewater. Batch precipitation results determined that phosphate was effectively reduced from 87 to less than 4 mg-P/L when the effluent water was mixed with 0.3 g/L of DL. The competitive precipitation mechanisms of different solids in the treatment system consisting of Ca^2＋–Mg^2＋–NH4^＋–PO4^3-CO3^2-were determined by comparing model predictions with experimental results. Thermodynamic model calculations indicated that hydroxyapatite（Ca10（PO4）6（OH）2）, Ca4H（PO4）3·3H2O, Ca3（PO4）2（beta）, and Ca3（PO4）2（am2）were more stable than struvite（MgNH4PO36·H2O） and calcite（CaCO3）. However, X-ray diffraction（XRD） analysis determined the formation of struvite and calcite minerals in the treated effluent. Kinetic experimental results showed that most of the phosphate was removed from synthetic effluent containing NH4^＋within 2 hr, while only 20% of the PO4^3-was removed in the absence of NH4^＋after 24 hr of treatment. The formation of struvite in the DL-treated effluent was due to the rapid precipitation rate of the mineral. The final pH of the DL-treated effluent significantly influenced the mass ratio of struvite to calcite in the precipitates. Because more calcite was formed when the p H increased from 8.4 to 9.6, a pH range of 8.0–8.5 should be used to produce solid with high PO4^3-content. This study demonstrated that DL could be used for effective removal of phosphate from the effluent and that resultant precipitates contained high content of phosphate and ammonium.Dolomite lime（DL）（CaMg（OH）4） was used as an economical source of Mg^2＋for the removal and recovery of phosphate from an anaerobic digester effluent of a municipal wastewater treatment plant（MWWTP） wastewater. Batch precipitation results determined that phosphate was effectively reduced from 87 to less than 4 mg-P/L when the effluent water was mixed with 0.3 g/L of DL. The competitive precipitation mechanisms of different solids in the treatment system consisting of Ca^2＋–Mg^2＋–NH4^＋–PO4^3-CO3^2-were determined by comparing model predictions with experimental results. Thermodynamic model calculations indicated that hydroxyapatite（Ca10（PO4）6（OH）2）, Ca4H（PO4）3·3H2O, Ca3（PO4）2（beta）, and Ca3（PO4）2（am2）were more stable than struvite（MgNH4PO36·H2O） and calcite（CaCO3）. However, X-ray diffraction（XRD） analysis determined the formation of struvite and calcite minerals in the treated effluent. Kinetic experimental results showed that most of the phosphate was removed from synthetic effluent containing NH4^＋within 2 hr, while only 20% of the PO4^3-was removed in the absence of NH4^＋after 24 hr of treatment. The formation of struvite in the DL-treated effluent was due to the rapid precipitation rate of the mineral. The final pH of the DL-treated effluent significantly influenced the mass ratio of struvite to calcite in the precipitates. Because more calcite was formed when the p H increased from 8.4 to 9.6, a pH range of 8.0–8.5 should be used to produce solid with high PO4^3-content. This study demonstrated that DL could be used for effective removal of phosphate from the effluent and that resultant precipitates contained high content of phosphate and ammonium.

关 键 词：Phosphorus recovery Struvite Crystallization Supernatant 

分 类 号：X703[环境科学与工程—环境工程]