鸟粪石结晶法回收垃圾渗滤液氨氮研究
Struvite crystallization for recovering ammonia nitrogen from landfill leachate
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摘要: 采用MgSO4·7H2O和Na2HPO4·12H2O使NH3-N生成MgNH4PO4·6H2O（鸟粪石）结晶沉淀法回收渗滤液中NH3-N。考察了pH值、反应时间、药剂配比对NH3-N去除率的影响。结果表明，鸟粪石结晶回收NH3-N反应的适宜pH值为9～9.5之间，过高的pH会破坏鸟粪石晶体结构，导致固定氨从MgNH4PO4中游离出来，不利于氨氮的去除。在pH值为9.5、反应时间为25 min、Mg2+∶NH+4∶PO3-4=1.5∶1∶1.5的最佳条件下，渗滤液中NH3-N浓度由初始3 500 mg/L,经结晶沉淀后降低至175 mg/L，去除率达95%。鸟粪石结晶沉淀过程中几乎不吸收重金属，同时回收了氨氮，其沉淀产物鸟粪石是一种优良的缓释肥原料。Abstract: A lab-scale study was conducted to precipitate the ammonia from landfill leachate in the form of magnesium ammonium phosphate(MAP) by applying such chemicals as MgSO4·7H2O and Na2HPO4·12H2O. The influences of pH value, reactive time and concentration on removal rate of ammonia nitrogen were tested. Results showed that the feasible pH values of crystallization and precipitation were between 9 and 9.5. The structure of struvite crystallization was destroyed under high pH value condition resulted in ammonia nitrogen dissociating from MAP, which reduced the removal rate of ammonia nitrogen. Results also demonstrated that ammonia nitrogen was effectively reduced from initial 3 500mg/L to final 175 mg/L, which removal efficiency reached 95% with crystallization and precipitation method when the optimal pH, precipitation time mole ratio of Mg2+,NH+4,PO3-4 were 9.5, 25 min and 1.5∶1∶1.5 respectively. Results also showed that MAP hardly absorbed heavy metal during struvite and crystallization, which was an excellent fertilizercontrolled release.
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Key words:
- landfill leachate /
- ammonia nitrogen /
- struvite /
- crystallization
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