鸟粪石法回收制肥工业废水中氨氮的中试研究

制肥工业废水中氨氮浓度高,难以直接进行生化反应,采用鸟粪石沉淀法可有效去除并回收氨氮。利用中试反应器回收某制肥工业废水中的氨氮,采用氯化镁与氧化镁作为联用镁源,通过考察不同进料方式、搅拌速度、停留时间等因素的影响,确定了鸟粪石法回收氨氮的最佳工况:采用间歇进水、固体投加镁源的投料方式,搅拌速度300 r/min,停留时间2 h。最佳条件下,氨氮去除率达到93.5%,磷残余率小于0.3%,生成的鸟粪石纯度可达85.6%,砷和铅的质量分数分别为0.0036和0.0008,符合肥料中重金属限值(GB/T 23349-2009),其他重金属均未检出。因此,回收产品有很好的利用价值。经济分析表明磷源是此方法处理成本较高的主要原因。

A pilot-scale study on ammonia-nitrogen recovery from fertilizer industry wastewater using struvite precipitation

High-strength ammonia-nitrogen usually exists in wastewater of fertilizer industry, which is difficult to be treated directly using biological technology. Struvite precipitation can efficiently remove and recover ammonia-nitrogen. In this study, a pilot-scale reactor was used to recover ammonia from fertilizer industry wastewater. MgCl₂ and MgO were used as magnesium agents. Effects of feeding mode, stirring speed and reaction time were investigated. The optimal conditions for ammonia-nitrogen recovery using struvite precipitation technology were as follows: intermittent feeding mode with addition of solid magnesium agents, stirring speed of 300 r/min, reaction time of 2 h. Under the above optimal conditions, the removal efficiency of ammonia-nitrogen was 93.5% and the residual phosphorus was less than 0.3%. The purity of the harvested struvite reached 85.6%. Mass fractions of arsenic and lead were 0.0036 and 0.0008, respectively, which were below the limits of heavy metal contents regulated by the fertilizer standards in China (GB/T 23349-2009), and other heavy metals were not detected. Therefore, the harvested struvite has good application value. Economic analysis showed phosphorus source is the main reason for high cost of this technology.