Study On Treatment Of Landfill Leachate By Two-Stage Biological Contact Oxidation Process

Landfill leachate which is produced in the process of sanitary landfill disposal is one kind of organic wastewater of high concentration. Its characteristics are complex component, deleterious and much fluctuation of water quality and quantity. Nowadays, environment has been polluted by landfill leachate seriously. Therefore, pollution control of landfill leachate has become a great research project in environmental protection field.Hydrolytic acidification-aerobic contact oxidation process was used to treat the wastewater in Hei Shizi Landfill. The aim of Hydrolytic acidification is to increase the biodegradability of landfill leachate. The following process is Biological Contact Oxidation which has characteristics of degradability. COD, NH3-N, TP, SS, color value and other index are tested and analyzed during experiment.The results showed that the effluence of COD, NH3-N, SS is below 900mg/L, 300mg/L respectively and SS is below 200mg/L. That comply the third standard of"Drainage Limits of Landfill Leachate (GB16889-1997)".The average removal rate of COD, NH3-N, TP is 64%, 74%, 54% respectively under low temperature. The effluence is balanced with fluctuation of water quality and quantity, which proves the loading capacity of Biological Contact Oxidation is good. The quantity and activity of microorganism under low temperature is not as good as microorganism at normal temperature. Sludge expand during low temperature, the main reason of that is temperature under growth need.The average removal rate of COD, NH3-N, TP is 73%, 91%, 77% respectively at low temperature, which is 9%, 17%, 23% higher than that under low temperature. For degradability of organism, nitrogen and phosphorus, the best DO of the fisrt and second Stage Biological Contact Oxidation is 2.5mg/L, 2.0mg/L respectively.The COD average removal rate of the first Stage Biological Contact Oxidation is 58% during volumetric loading of 0.33～0.47kgCOD/(m3·d) volumetric loading. In the second Stage Biological Contact Oxidation, the COD average removal rate is form 21% to 59% during volumetric loading of 0.10～0.21kgCOD/(m3·d).The TN average removal rate of the first Stage Biological Contact Oxidation is from 43% to 75% during C/N of 3.0~9.0. C/N rise to 12.4, the TN average removal rate is lower slightly. When C/N is more than 6.5, the TN average removal rate is more than 80% in the second Stage Biological Contact OxidationThe research also expressed that seven metals we detect in wastewater, six of them are priority control pollutants. Pb concentration exceed the value of concentration of heavy metals in landfill leachate in China. Fe, Zn, Cr have high concentration. Others are low. Biological Contact Oxidation can remove Cu, Pb, Fe, Zn efficiently. The removal rate of them is more than 60%. The removal rate of Cd, Ni is 40%～59%. Only Cr is blow 30%.