污泥脱水滤液水质对以鸟粪石形式回收磷的影响

为了研究污泥脱水滤液水质对以鸟粪石(MgNH_4PO_4·6H_2O)形式回收磷的影响,利用六联搅拌机模拟序批式搅拌反应器.结果表明:保持各试验均在搅拌转速为200 r/min,反应历时为180 min,沉淀历时为60 min条件下运行,在无需加入任何药剂的情况下,经搅拌后,污泥脱水滤液pH值升高,但还不足以生成鸟粪石沉淀;当PO_4~(3-)初始浓度为4.00 mmol/L时,虽然90%以上的PO_4~(3-)会以磷酸盐形式从污泥脱水滤液中沉淀下来,但须将污泥脱水滤液中Mg~(2+)初始浓度提高到5.00 mmol/L才能抑制Ca~(2+)与PO_4~(3-)的结合,使PO_4~(3-)、Mg~(2+)和NH_4~+回收浓度比接近3种离子在鸟粪石晶体中的化学计量比(1:1:1),即以鸟粪石形式回收的磷最多;当污泥脱水滤液在pH值为10.0～10.5条件下反应时,鸟粪石产量最高;污泥脱水滤液浊度越高,Mg~(2+)回收物质的量浓度越低,相应鸟粪石产量也越低.

Influence of Sludge Dewatering Filtrate Components on Phosphorus Recovery in Form of Struvite

Effects of the constitutes of sludge dewatering filtrate on phosphorus recovery in form of struvite (MgNH_4PO_4·6H_2O) were studied by using batch stirring reactors.The results showed that with keeping stirring speed at 200 rpm,stirring time at 180 min and precipitation time at 60 min in all experiments,pH of sludge dewatering filtrate rose after stirring without reagent addition;however,it was not enough to form struvite.When the concentration of PO_4~(3-) was at 4.00 mmol/L,more than 90% of the PO_4~(3-) was recovered. But only the initial concentration of Mg~(2+) in sludge dewatering filtrate exceeded above 5.00 mmol/L,the reaction between Ca~(2+) and PO_4~(3-) was inhibited distinctly and the ratio of the recovery molar concentration of PO_4~(3-)、Mg~(2+) and NH_4~+ could nearly reach 1:1:1.which means that the most quantity struvite were formed. When pH ranged from 10.0 to 10.5,the most quantity of struvite formed.Turbidity of sludge dewatering filtrate had negative effect on the recovery of Mg~(2+) and struvite formation.