| Yongsheng landfill Site is located at the junction of Wenjiang District and Chongzhou City.Since 1995,the landfill had been used for collection and landfill of Wenjiang.The landfill was closed in 2002,however,a thin layer of soil was simply covered on the landfill area and the landfill was unsatisfactory in sanitary landfill conditions.Nowadays,there are many residential and industrial areas around Yongsheng landfill.The landfill has brought many environmental problems and make it difficult to be compatible with the local environment.In the 13 th Five-Year Plan of China,it is clearly proposed that the old landfills should be comprehensively renovated,to reduce environmental impacts.Located in the upstream of Minjiang Water Plant and Jinma Water Plant drinking water source protection area,Yongsheng landfill is the research object of this paper to discuss the scheme of comprehensive renovation design for its area.Aiming at the problems of Yongsheng landfill,such as the difficulty in landfill capacity,the influence on downstream drinking water source protection area and the pollution of leachate to surroundings,this paper carries out a preliminary investigation about surroundings of the landfill,analyses necessity and methods of the comprehensive renovation.Based on these investigation and methods,a comprehensive renovation scheme with a little environmental impact and is put forward,and the environmental impact of this scheme is evaluated.The main results are as fellows.(a)There are four landfill areas,with a total area of about 33,881 square meters to be renovated.The landfill was early sealed without leachate and landfill gas collecting system.A large amount of construction waste was covered on the rough surface of the landfill.There are great dangers to the water source,and influence to the surrounding residents.(b)Drilling tests at 29 samples show that construction waste and domestic waste are the main waste types.The organic matter content of waste is about 7.65% to 10.70%.The thickness of the landfill in Area A is 11.4-16.0m,in Area B is 4.2-8.5m,in Area C is 4.8-5.5m,and in Area D is 4.8-6.4m.The interpolation program was used to predict the amount of waste,and the total amount of waste was calculated about 310,000 cubic meters.(c)The "area A and new increased area" scheme was used to excavate and transport waste in four landfill areas to one area.The excavation depth of different landfill areas are 3.5m to 16.0m.The system of bottom anti-seepage of waste was designed in the new landfill area.The system of leachate control was designed as "collecting pipe,main pipe and leachate well".The system of landfill gas collection was designed as "landfill gas well,gas collecting pipe and gas vent".The height of the renovated landfill was 10 m,with the design of heap shaping in the area,which covers 29,815 square meters and was 12.0% lower than before.The system of closure was designed as "base layer,exhaust layer,impervious layer,drainage layer and soil cover layer".The rainwater collection system of the landfill was designed as "drainage ditch and drainage channel",with the length of 1,400 meters.With rainwater and sewage diversion design,the leachate sewage was disposed by Yongsheng sewage treatment plant.The maximum predicted concentration of COD in leachate is 122.0 mg/L,and the concentration of ammonia nitrogen is 44.6 mg/L,which all meet national standards.(d)After renovation,the area of landfill has been reduced by 12.0%,the impact area has been reduced by 67.54%,and the value of land assets has increased to 6.389 billion yuan.Through controlling the leachate,it is estimated that the emission of COD and ammonia nitrogen will be reduced by 44.58 t and 18.43 t in 10 years.All uncontrollable waste were in the sanitary landfill,which reduced the risk to the drinking water sources,and guaranteed the safety of drinking water about 2 million people in Wenjiang,Shuangliu and Tianfu New Area.The landfill gas around the landfill could meet the emission standards,and the living conditions of nearly 3000 people has been improved significantly in the Tuanjie Village,Yongsheng Town. |
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