Treatment Technique Based On Ecological Safety For Mixed Landfill Leachate

Large amount of solid waste are produced during industrial production and mining process. The waste itself and its leachate in the storage process lead to serious environmental pollution to the surroundings. At present, the leachate, which contains polluted ingredients, is always treated by physical and chemical methods.This thesis is based on a mixed landfill leachate in Anhui Huainan City, and it originates from the reclamation area with chemical garbage, coal gangue and living garbage. The purpose of this study is to get an effective control technology for mixed landfill leachate on the basis of ecological security and to reduce its harm to the environment. First, routine water quality analysis of landfill leachate was carried out in laboratory, and the results showed that leachate water was strongly alkaline, high soluble salt, and it also contained a certain amount of nitrogen and phosphorus and a variety of heavy metal ions, resulting in great leachate toxicity. Therefore, an effective leachate treatment technology should be taken to reduce the toxicity of landfill leachate.Orthogonal tests were carried out to investigate removal effect of various kinds of pollutants with different pH, different dosing amount of coagulant, and different polyacrylamide additive quantity, and then toxicity tests were conducted to analyze the effect of the treated landfill leachate on Lolium multiflorum and Chlorella pyrenoidosa, Brachydanio rerio, Radix swinhoei. And finally comprehensive evaluation method was used to evaluate the effect of major pollutants and toxic removal of several coagulation sedimentation ways, the evaluation results showed that aluminium potassium sulfate and polyacrylamide in combination could achieve better effect than the other two combinations of coagulants and polyacrylamide, and it had the highest ecological security in the three combinations. The conclusion was that the optimal coagulation conditions for the landfill leachate were as follows:the pH of the leachate was adjusted to 9 and the dosage of aluminium potassium and polyacrylamide was respectively 1.5g·L-1 and 0.3g·L-1.Through orthogonal tests, the limestone, haydite, zeolite, and bamboo charcoal were used to explore the removal efficiency of major pollutants in different levels, and the toxicity removal efficiency evaluation index was used to evaluate constructed wetland technology. And the results showed that packings mainly achieved the purification of the leachate in constructed wetland without plants via the three combinations of physical adsorption, biodegradation and chemical reactions. For different packings, due to their special physical and chemical properties, the contribution rate of three mechanisms for different pollutants purification effect were different. The contribution rate of four kind packings of limestone, haydite, zeolite, and bamboo charcoal on the removal efficiency of nitrogen in the leachate was higher, but the contribution rates of removal effect of the total phosphorus and CODMn in leachate were low. When the filling height of limestone was 16 cm, and the filling height of haydite, zeolite, and bamboo charcoal respectively was 24 cm, the removal effect of pollutants and toxicity was the best in constrcted wetland without plants.The purification effect of leachate was studied through pilot study with the combinations of coagulation sedimentation and constructed wetland technology, and the results showed that combination of coagulation sedimentation technology and constructed wetland technology could both stably and efficiently remove the pollutants in landfill leachate, and the average removal rate of TN, NH4+-N, TP and CODMn respectively was 81.97%、81.93%、91.53%、72.66% during system operation, and the ecological security of treated leachate was higher, which has less harm to the surrounding environment.