Jaffer Y, Clark T A, Pearce P, Parsons S A
School of Water Sciences, Cranfield University, Bedfordshire, UK.
Water Res. 2002 Apr;36(7):1834-42. doi: 10.1016/s0043-1354(01)00391-8.
Formation of struvite (MgNH4PO4 x 6H2O) at sewage treatment works can cause operational problems and decrease efficiency. Struvite has a commercial value and the controlled formation and recovery of it would be beneficial. A mass balance was conducted at full scale across the whole sewage treatment plant in order to identify a stream to conduct bench-scale struvite crystallisation studies. The most suitable stream was identified as the centrifuge liquors. The average flow of the liquor stream was 393 m3 d(-1) and the composition was as follows: 167 mg L(-1) phosphorus, 44 mg L(-1) magnesium, 615 mg L(-1) ammonium, 56 mg L(-1) calcium and 2580 mg L(-1) of alkalinity. The pH averaged at 7.6 and the stream had a predicted struvite precipitation potential of 140 mg L(-1). Struvite crystallisation occurred quickly during the trials, by raising the pH of the centrifuge liquors to 9.0 and dosing with magnesium. Up to 97% phosphorus removal as struvite was achieved. Struvite formation occurred when the molar ratio of magnesium:phosphorus was at least 1.05:1. Below this ratio phosphorus removals of 72% were observed, but not exclusively as struvite. Annual yields of struvite were calculated to be 42-100 tonnes a year, depending on the dose regime. Revenue from the sale of produced struvite could be between Pound Sterling8400 and Pound Sterling20,000 a year.
污水处理厂中鸟粪石（MgNH4PO4·6H2O）的形成会导致运行问题并降低效率。鸟粪石具有商业价值，对其进行可控的形成和回收将是有益的。在整个污水处理厂进行了全规模的质量平衡分析，以确定一个用于进行鸟粪石结晶实验室规模研究的物流。最合适的物流被确定为离心机滤液。该滤液流的平均流量为393立方米/天，其成分如下：磷167毫克/升、镁44毫克/升、铵615毫克/升、钙56毫克/升以及碱度2580毫克/升。pH值平均为7.6，该物流的鸟粪石沉淀预测潜力为140毫克/升。在试验过程中，通过将离心机滤液的pH值提高到9.0并添加镁，鸟粪石结晶迅速发生。以鸟粪石形式实现的磷去除率高达97%。当镁与磷的摩尔比至少为1.05:1时，会形成鸟粪石。低于此比例时，观察到磷去除率为72%，但并非完全以鸟粪石形式去除。根据投加量方案，鸟粪石的年产量计算为每年42至100吨。所生产鸟粪石的销售收入每年可能在8400英镑至20000英镑之间。
