Biological Treatment Of The Mixture Of Acid Mine Drainage And Leachate

Acid mine drainage and landfill leachate are two kinds of waste water which cause serious environmental pollution and do great harm to human beings. Landfill leachate contains large amount of organic contaminants with the typical features of poor biodegradability, high concentration of salt and ammonia nitrogen. Acid mine drainage has large water yield, low pH value (usually 2-3), high concentrations of gulfate and soluble heavy metal ion. In this paper, landfill leachate and acid mine drainage were mixed before biological treatment. The mixture contained high concentration of sulfate, large amout of organic matter and heavy metal ions, as well as good pH buffer capacity from landfill leachate, which provided suitable conditions for the growth and reproduction of sulfate reducing bacteria and other anaerobic microorganisms. Under anaerobic conditions, organic matter was disassimilated by anaerobic microorganisms, which produces a certain basicity. At the same time, sulfate was reduced to sulfide which can form heavy metal sulfides with heavy metal ions, thus realizing the removal of sulfur and heavy metal ions simultaneously. To further reduce the concentration of organic matter and deal with the nitrogen in the effluent of anaerobic treatment, aerobic and anoxic denitrification of biological treatment technology was conducted. Methane and heavy metals can also be obtained or in the wastewater biological treatment process described above. Therefore, the research in this paper will support and help the better realization of using waste to treat waste and the resource transformation of wastewater.Firstly, this paper examined the effect of anaerobic biological treatment of the mixture of acid mine drainage and leachate which has different m(COD)/m(SO42-) ratios of 0.5,1 and 3, and determined the optimum ratio; secondly, started and operated an anaerobic reactor by using the mixture of acid mine drainage and leachate whithout inoculating anaerobic sludge; thirdly, started and operated aerobic and anoxic reactor by using synthetic wastewater and ananerobic reactor effluent as inffluent; finally, made realization of continuous treatment of the mixed wastewater by anaerobic, aerobic and anoxic biological reactors, to get the removal of organic matter, sulfate, heavy metal and nitrogen. The experimental results were showed as follows,1. Under anaerobic conditions, the mixed solution with m(COD)/m(SO42-) value of 3 has the best removal effect in 35℃ compared to the m(COD)/m(SO42") values of 0.5 and 1.The romoval rate of COD and sulfate reached 66.04% and 60.31%, respectively.2. According to the optimal m(COD)/m(SO42-),this two kinds of wastewater (acid mine drainage and landfill leachate) are mixed, the concentration of COD, sulfate and ammonia nitrogen was 7500 mg/L,2500 mg/L and 2000mg/L, respectively. The COD and sulfate removal rate of the effluent respectively reached 78% and 80% after anaerobic treatment with HRT of 20 d.3. The effluent of anaerobic reactor was treated directly by the aerobic reactor under HRT of 30 days at the temperature of 30℃, the removal rate of ammonia nitrogen and COD was 99% and 85%, respectively.4. The effluent of aerobic reactor effluent was treated directly by the anoxic reactor under HRT of 4 days at the temperature of 30℃, the removal rate of nitrate nitrogen and COD was 98% and 96%, respectively. The removal rate of total COD, sulfate and ammonia in the mixture of acid mine drainage and landfill leachate was 98 %,80% and 99%, respectively.