Study On Removal Of The Nitrate In Landfill Leachate With The Bio-electorde Process

Nitrate is one of the main pollutants in water. Among many available methods of water denitrification, but biological denitrification is the only one that can completely deoxidize nitrate to harmless nitrogen gas, and is considered as the most promising process. Bio-electrode process, which combines the biological process and electrochemical process, is a new developing denitrification method. Comparing with the traditionary biological denitrification methods, bio-electrode process is economical since organic carbon as external carbon source is avoidable, and has no need of the post-treatment. In addition, the denitrification efficiency can be greatly increased with an amount of external organic carbon What's more, the process is simple, easy to operate and maintain. But it isn't applied for denitrification of Landfill leachate.The liquid volume of the internal cylinder was 0.7L and the total volume of the internal cylinder was 1.0L. The thermostated water was supplied by water bath. There were 4 (four) carbon electrodes in series as cathodes and 1(one) carbon electrode as anode in the reaction chamber. The length of cathode was 250mm and the length immersed in the liquid was 210mm. The diameter of cathode was 11mm.Application of a bio-electrode reactor for treating the nitrate polluted landfill leachate of region was investigated experimentally in this paper. To get the optimum process condition, a 4-factors and 4-levels orthotropic experiment(L16(44)) was carried out in this study on the simulated water prepared by dissolving sodium nitrate(200 mg-N/L) into tap water. The 4 factors were temperature, C/N ratio, HRT and electric current. When the temperature, the electric current, the C/N ratio and the HRT is respectively 30℃, 80mA, 3 and 8 hour, a higher effect of TN(total nitrogen, nitrate concentration + nitrite concentration) removal rate was achieved. The range of each factor was shown as follows, electric current(21.09, average TN removal rate) > temperature (18.06) > C/N(10.18)> HRT(5.33). It was concluded that electric current should be the predominant factor.The bacteria of denitrification like the middling temperature, Whatever the temperature is excessive low or excessive high, the bacteria of denitrification will be controled. And the favorable temperature is 30℃. The TN and the TOC will be simultaneously eliminated when the C/N rate is 1, and is lower than the theoretic value (1.07). The current experiment comfirmed that the current could improve the efficiency of the nitrate removal ratio, and the nitrate's eliminating ratio relates to the current, In this experiment, 80mA is the best current. The nitrate's eliminating ratio will be improved when the HRT is longer.At last, it was confirmed that a higher nitrate removal ratio more than 96% could be achieved to the polluted water in natural when the NO3—N is100 mg/l and C/N is 1 and HRT is 8h.