A B C D E F G H I J K L M N O P Q R S T U V W X Y Z All
The landfill leachate in The Khajod Solid Waste Disposal Site, Surat usually contains quite high NH4+-N concentration, which is well known to inhibit nitrification in biological treatment processes. A common pre-treatment for reducing high strength of ammonium (NH4+-N) is by an air-stripping process. However, there are some operational problems such as carbonate scaling in the process of stripping. For this reason, some technical alternatives for NH4+-N removal from leachate need to be studied. In this study, a bench-scale experiment was initiated to investigate the feasibility of selectively precipitating NH4+-N in the leachate collected from a local landfill in Surat as magnesium ammonium phosphate (MAP). In the experiment, three combinations of chemicals, MgCl2.6H2O + Na2HPO4.12H2O, MgO + 85% H3PO4, and MgO + Na5P3O10, were used with the different stoichiometric ratios to generate the MAP precipitate effectively. The results indicated that NH4+-N contained in the leachate could be quickly reduced from 1108 mg/l to 40 mg/l within short period of time, when MgCl2.6H2O + Na2HPO4.12H2O were applied with a Mg2+:NH4+:PO43- mole ratio of 1:1:1. The pH range of the minimum MAP solubility was discovered to be between 8.5 and 9.0. Attention should be given to the high salinity formed in the treated leachate by using MgCl2.6H2O + Na2HPO4.12H2O, which may affect microbial activity in the following biological treatment processes. The other two combinations of chemicals [MgO + 85% H3PO4 and MgO + Na5P3O10] could minimize salinity after precipitation, but they were less efficient for NH4+-N removal, compared with MgCl2.6H2O + Na2HPO4.12H2O. COD had reduced up to 50% during this precipitation. It was found that the sludge of MAP generated was easily settled within 30 minutes to reach its solids content up to 50%.
