鸟粪石结晶法去除垃圾渗滤液中NH_4~+-N的效果研究

研究了鸟粪石结晶法对经混凝预处理后的垃圾渗滤液中NH4+-N的去除效果,考察了不同影响因素对NH4+-N去除效果的影响,并进行了磷酸铵镁(MgNH4PO4·6H2O,简称MAP)沉淀的表征及成分分析,并提出了反应后溶液中Mg2+、PO43-及MAP的回收利用办法。结果表明,反应的最佳条件为:pH8.5～9.5,Mg2+∶NH4+∶PO34-(摩尔比)=1.1∶1.0∶1.3,反应温度30℃,反应时间为25 min时,此时NH4+-N的去除率达94.70%;最佳沉淀剂投加组合为MgCl2.6 H2O与Na2HPO4·12H2O;pH为9.0时生成的沉淀符合典型MAP沉淀的晶体结构,生成的沉淀大部分为MAP,且没有氰化物、酚等有害物质的检出,而pH为10.5时生成的沉淀由许多疏松的微小沉淀颗粒组成,排列较杂乱,影响了沉淀的纯度。利用鸟粪石结晶法去除混凝预处理后的垃圾渗滤液中NH4+-N技术可行,经济效益合理,具有广阔的应用前景。

Removal of NH_4~+-N from pre-treated landfill leachate by struvite crystallization

The method of struvite crystallization was applied for NH_4~+-N removal from coagulation pre-treated landfill leachate. Theeffect of pH, Mg~(2+) dosage, PO_4~(3-) dosage, temperature, contacting time on treatment efficiency was investigated. The obtained MAP deposition was characterized by SEM and XRD. The optimum reaction conditions were found as follows temperature of 30 ℃ , pH ranged from 8. 5-9. 5, molar ratio of Mg~(2+) , NH_4~+ and PO_4~(3-) was 1. 1: 1. 0: 1. 3 and reacting time of 25 min. Under these conditions, the NH_4~+-N removal rate could reach 94. 70%. The composition of MgCl_2 · 6H_2O and Na_2HPO_4 ? 12H_2O had best effeiciency for NH_4~+-N removals the deposition obtained at pH of 9. 0 presented typical MAP crystal structure, the main component of deposition was MgNH_4 PO_4 · 6H_2O, while the deposition obtained at pH of 10. 5 had irregular structure and lower MAP purity. The given technology was practicable and economical and had broad application prospect.