Study on technological parameters of the treatment of landfill leachate by MAP method using response surface methodology

Key words: 
• response surface methodology /
• landfill leachate /
• ammonia-nitrogen /
• chemical precipitation method /
• crystal shape

Abstract: The effect factors of ammonianitrogen removal by magnesium ammonium phosphate (MAP) process for landfill leathate, using singlefactor tests and response surface methodology (RSM) were studied. The variance of ammonianitrogen removals were analyzed under the conditions of high and low levels of pH values, ratio ofn(Mg)∶n(N) and n(P)∶n(N)8.0 to 11.0, 0.8 to 1.6 and 0.8 to 1.3 respectively. Data were analyzed by the software of Design-Expert 5, a quadratic response surface model and optimum level values in terms of actual factors was obtained based on the experimental data. pH value be adjusted from the optimum level value (8.3) to 9.5, ratio of n(Mg)∶n(N) and n(P)∶n(N) were 1.40，1.19 respectively from the optimum level values. Ammonia-nitrogen removal efficiency reached to 92.2%. Although the removal rate was 2 percentage lower compared with that under the optimum conditions, the advantage of economy and condition of operation was obvious. The morphology of precipitate was studied by scanning electron microscope (SEM) and X-ray diffraction (XRD). Most of the composition was magnesium ammonium phosphate.