Struvite precipitation in anaerobic swine lagoon liquid: effect of pH and Mg:P ratio and determination of rate constant

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• 作者：Nelson ; Nathan O. ; Mikkelsen ; Robert L. ; Hesterberg ; Dean L.
• 关键词：Magnesium&ndash ; ammonium&ndash ; phosphate ; Struvite ; Solubility curve ; Animal waste treatment ; Crystal growth ; Phosphorus ; Precipitation kinetics
• 刊名：Bioresource Technology
• 出版年：2003
• 出版时间：September, 2003
• 年：2003
• 卷：89
• 期：3
• 页码：229-236
• 全文大小：322 K

文摘

Because of increased concern about surface water eutrophication from nutrient-enriched agricultural runoff, many swine producers are encouraged to decrease application rates of waste-based P. Precipitation and subsequent removal of magnesium ammonium phosphate (MgNH₄PO₄·6H₂O), commonly known as struvite, is a promising mechanism for N and P removal from anaerobic swine lagoon effluent. The objectives of this research were to (i) quantify the effects of adjusting pH and Mg:P ratio on struvite precipitation and (ii) determine the rate constant pH effect for struvite precipitation in anaerobic swine lagoon liquid. Concentrations of PO₄-P in liquid from two anaerobic swine lagoons were determined after 24 h of equilibration for a pH range of 7.5–9.5 and Mg:P ratios between 1:1 and 1.6:1. Struvite formation reduced the PO₄-P concentration in the effluents to as low as 2 mgl⁻¹. Minimum concentrations of PO₄-P occurred between pH 8.9 and 9.25 at all Mg:P ratios. Struvite precipitation decreased PO₄-P concentrations by 85 % within 20 min at pH 9.0 for an initial Mg:P ratio of 1.2:1. The rate of PO₄-P decrease was described by a first-order kinetic model, with rate constants of 3.7, 7.9, and 12.3 h⁻¹ at pH 8.4, 8.7 and 9.0 respectively. Our results indicate that induced struvite formation is a technically feasible method to remove N and P from swine lagoon liquid and it may allow swine producers to recover nutrients for off-farm sale.