Study On Degradation Of Fulvic Acid And Advanced Treatment Of Landfill Leachate By Catalytic Ozonation

Landfill leachate is a kind of high concentration organic wastewater which produced from landfill and incineration plant. The main characteristics of landfill leachate are as follows: Variety of organic pollutants; high concentration of CODCr and BOD5, and its poor biodegradability; the high content of NH3-N and its high stability for a long time; a variety of heavy metal ions; deep color and bad smell. At present biological process is the common method for treatment of landfill leachate, but the concentration of organic matters and NH3-N are relatively high after biological treatment. Therefore, advanced treatment of landfill leachate is needed to meet the requirements of the discharge standard.The removal efficiency of fulvic acid (FA) by catalytic ozonation over Co-Mn-Ox catalyst was firstly investigated, and then the influencing factors and the reaction process of catalytic ozonation were studied in semi-continuous flow mode. Based on these results, the technical parameters of catalytic ozonation in continuous flow mode were optimized, and finally the efficiency of advanced treatment of landfill leachate by catalytic ozonation was investigated.The removal efficiency of CODCr is significantly improved by adding the catalyst, but the increase of catalyst dosage has little impact on the removal efficiency. The removal of CODCr is significantly improved when the solution is strongly alkaline; the removal efficiency of CODCr increased when pH increased from1.4to7in the buffer solution. While pH continues to increase, the removal efficiency of CODCr is unsignificantly changed. Inorganic anion Cl-had a significant negative impact on the oxidation of FA, and the negative effect increased with increasing the concentration of Cl-. The removal of FA was seriously inhibited by the addition of radical inhibitor HCO3-or CO32-. The presence of large amount of ammonium greatly promoted the degradation of FA; on the contrary, ammonia had a significant negative impact on the oxidation of FA. Low concentration of manganese ion or copper ion inhibited the degradation of FA, but calcium ion or ferrous ion promoted its degradation.The degradation of fulvic acid and the intermediates produced in catalytic ozonation were studied by liquid chromatography, ion chromatography and TOC analyzer. The results showed that oxalic acid, acetic acid and pyruvic acid was generated in the reaction process, and N and S atoms on the benzene ring of fulvic acid converted into nitrate and sulfate, respectively. The results of the dissolved ozone concentration in single ozonation and catalytic ozonation showed that Co-Mn-Ox catalyst promoted decomposition of ozone and improved its utilization efficiency.The effect of technical parameters on catalytic ozonation of fulvic acid (FA) in continuous flow mode was studied. The main parameters included hydraulic retention time (HRT), catalyst dosage, and Height to Diameter Ratio of reactor (H/D). The results proved that the increase of HRT, catalyst dosage, and H/D of reactor were helpful to improve degradation efficiency of FA, Considering the cost-effectiveness, the appropriate parameters are HRT58min, catalyst dosage0.5g, and H/D6.5:1respectively.The test results in advanced treatment of landfill leachate by catalytic ozonation showed that the degradation efficiency of organic pollutants in landfill leachate was much high. The chromaticity of the landfill leachate was completely removed and the removal efficiency of CODCr exceeded70%.