Recovery of ammonia through struvite production using anaerobic digestate of piggery wastewater and leachate of sewage sludge ash

Anaerobic digestate of piggery wastewater (ADPW) contains high concentrations of ammonia and phosphorus with unbalanced molar ratio. Thus, ammonia remains at a high level even after phosphorus is completely removed through struvite formation. In this study, both ammonia and phosphorus were recovered by adding leachate of sewage sludge ash (SSA) into ADPW. It was demonstrated that 11,600mgL(-1) of total phosphorus and 7266.7mgL(-1) of -P were extracted from SSA by using sulfuric acid at the H2SO4/SSA mass ratio of 0.35. ADPW and the leachate of SSA were mixed at the volumetric ratio of 1:1.29, and then struvite was formed at the molar ratio of 1.2 (Mg2+):1.0 (-P):1.0 (NH3-N). Removal efficiencies of ammonia and phosphorus were 91.95% and 99.65%, respectively. The obtained struvite was analyzed by various methods and was found to meet the Korean fertilizer standards, except for copper.