鸟粪石结晶法回收垃圾渗滤液氨氮研究

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∶PO^3-₄=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。

Struvite crystallization for recovering ammonia nitrogen from landfill leachate

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 MgSO_4·7H_2O and Na_2HPO_4·12H_2O. 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 struc-ture of struvite crystallization was destroyed under high pH value condition resulted in ammonia nitrogen dissocia-ting 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 Mg~(2+) , NH_4~+ ,PO_4~(3-) were 9. 5, 25 min and 1.5:1:1.5 respectively. Results also showed that MAP hardly absorbed heav-y metal during struvite and crystallization, which was an excellent fertilizer-controlled release.