Ammonium Removal from Landfill Leachate by Means of Multiple Recycling of Struvite Residues Obtained through Acid Decomposition

The treatment of landfill leachate, due to its great polluting load, is a very difficult task.In particular, the abatement of high ammonium concentrations represents one of the main issues.Among the available techniques, struvite precipitation is an effective method for the removal andrecovery ofNH4+ load. However, due to the lack of phosphorus and magnesium amounts, the struviteformation results in an expensive process in the leachate treatment. To overcome this issue, in thepresent work, we developed a simple and suitable method for ammonium removal by the multiplerecycling of struvite decomposition residues. In this regard, a procedure for acid dissolution ofstruvite, produced by using industrial grade reagents, was initially defined. The effect of pH,temperature, and acid type was investigated. The experimental results proved the effectiveness ofboth hydrochloric and acetic acid, which allow a high and selective release of ammonium at T = 50 Cand pH = 5.5. The multiple reuse of decomposition products, combined with the supplementationof a small quantity of phosphorus and magnesium at molar ratios of n(N):n(Mg):n(P) = 1:0.05:0.05,guarantees stable NH4+ abatement of about 82%. The proposed process allows a cost saving ofaround to 74% and can be easily applied in industrial treatment plants