Removal of Ammonia from a Biologically Treated Pesticide Wastewater by Struvite Precipitation

摘要

The aim of this study was to investigate ammonia removal from the effluent of a full-scale biofilm reactor treating pesticide wastewater through the formation of struvite (MgNH_4PO_4·6H_2O). The requirement of magnesium and phosphate ions for precipitation was met by adding MgO and Na_2HPO_4. Different NH_4~+:Mg~(2+):PO_4~(3-) molar ratios were tested in batch reactors to optimize the precipitation conditions. Ammonia was reduced to 25 mg/L from an initial concentration of 210 mg/L at the highest ratio tested (1:1.2:1.3), equating to 88% removal. However, the extent of ammonia removal was only slightly affected when the N:Mg ratio was reduced from 1:1.2 to 1:0.6; dropping to 83% from 88% on a percentage basis. Struvite precipitation can be easily incorporated within the existing post-treatment section of the full-scale plant, providing the pesticide manufacturing facility with a reliable backup process for its nitrification system.