Ammonia removal from landfill leachate by struvite formation: an alarming concentration of phosphorus in the treated effluent
This study examined the removal of ammonia nitrogen from the leachate of a landfill site using the chemical precipitation of struvite (MgNH4PO4.6H2O). This procedure achieved a reduction in the ammonia concentration that was higher than 99% when the molar ratio of 1.8:1.0:1.4 for Mg2+:NH4+:PO43− was adopted. The metal concentration found in the precipitate formed was lower than the limits set by Brazilian and American regulations (CONAMA 375/2006 and US EPA, 40 CFR 503.1993). This demonstrates the potential use for this practice in agriculture. However, the effluent obtained from the tests presented a phosphorus concentration higher than the one in the raw leachate. This shows that removing this compound from the effluent must be further studied. Otherwise, adopting the chemical precipitation of ammonia by the formation of struvite may become unfeasible.