The Research Based On Processing Of Concentrate Leachate Under Low-Temperature Vacuum Evaporation

In the process of landfill leachate treatment,60%to70%of the leachate can be discharge within standards after the reverse osmosis or nanofiltration treatment. But there are still40%to30%of the membrane-filtration-concentration which need further treatment and disposal, because of the complex pollution component and the high electrical conductivity. In this paper the membrane-filtration-concentration be processed with the method of low-temperature-vacuum evaporation. Based on the analysis of concentration liquid’s character and the compare of concentration liquid’s common treatment methods, we can analyze how the factors like operating vacuum degree (temperature), pH and the rate of evaporation impact the condensate water’s quality and major pollutants’removal through laboratory experiments. Then explore the variation of the residual concentrate’s heavy metals and propose a further processing to deal with the residual concentrate.The results of experiments showed that:①ith increasing the degree of vacuum operation, the operating temperature will decrease, so is the fouling mitigation of heating device, besides that the conductivity of the condensate will reduce, but the COD of condensate will increase.②pH of concentrate is also a major factor affecting water quality. Under neutral conditions, the removal efficiency of COD is the highest. But with higher pH, conductivity of condensate will fall, and will be a slight increase in the concentration of ammonia nitrogen.③The main factors which affect the water quality of the condensate are evaporation of volatile organics, evaporation of free ammonia and entrained vapor from boiling vigorously. Thus resulting in poor water quality during early and late evaporation processing and good water quality in the mid of processing. When the evaporation rate is62.5%to75%, the condensate should be collect.④By orthogonal experiment and cost analysis, the optimum operating parameters of processing membrane-filtration-concentration under low-temperature vacuum evaporation are:the degree of vacuum is0.070MPa, pH is neutral, the evaporation rate is62.5%. In this condition, we can reduce operating costs and ensure the condensate water quality within discharge standards.After the low-temperature-vacuum treatment of the concentrate liquid, there are still some residual concentrate needs further processing. Detective the concentration of heavy metals of the residual concentrate by using flame atomic absorption spectrometry. Experimental data show that: the vacuum and pH variation are not significantly affected on heavy metal concentrations. Over93%of the heavy metals are enriched in the residual concentrate. Recommend using Fenton-flocculation-adsorption treatment to process the residual concentrate.This study proposes a new approach to the use of low-temperature-vacuum evaporation processing the membrane-filtration-concentration. This study can broaden the handling method of membrane-filtration-concentration, and provide useful guidance for practical application of low-temperature-vacuum evaporation mehode.