Research On The Mechanism Of Clogging In The Leachate Drainage System Of Hazardous Waste Landfill

Leachate drainage system is an important functional unit of landfill.However,in the long-term operation of landfill,the drainage system is often filled with clog deposits,resulting in the decrease of void ratio of drainage layer,the decrease of flow-through capacity,and the decline or even loss of drainage function,which leads to the rise of leachate level in landfill,the shortening of life of anti-seepage membrane and the increase of seepage.Leachate leakage risk affects landfill stability.Based on the field simulation experiments of predecessors,this paper studies the silting mechanism of the guided discharge layer of hazardous waste landfill.Through the analysis of the structure of landfill and the characteristics of leachate,the possibility of silting up of hazardous waste landfill and the formation mechanism of silt are confirmed by indoor simulation tests.On this basis,the single factor experiment was used to explore the mechanism of the main factors affecting the formation of silting,and the silting time and leachate water level in the actual scenario were predicted according to the simulation experiment.The results show that:Firstly,through the analysis of leachate composition,combined with the common silting mechanism in existing research,it is concluded that there are three possibilities of physical,chemical and biological silting in the guide layer of hazardous waste landfill.Then,through the indoor simulation test,it is determined that there are three kinds of blocking mechanism in the guide layer of hazardous waste landfill,and the increase of leachate concentration and permeation rate will accelerate the blocking process of the guide layer,which needs to be controlled in time.According to the analysis of the blocking material,it is found that the content of Ca²⁺in the blocking material is more,the main component is CaCO₃.Finally,three models are used to predict the leachate water level,among which Moore 80 method is more conservative,and the maximum leachate water level is 52.5cm.Moore 83 method is optimistic,the maximum leachate water level is 14.5 cm,representing the maximum leachate water level under optimistic conditions.Giroud 92method is relatively objective,and the maximum leachate water level is 24.5 cm.Therefore,with the aging of the mulch and the increase of the landfill operation time,the leachate water level will increase significantly.Based on the simulated silting test,the silting time and the maximum water level of leachate after silting are predicted,and the actual effect of silting on the permeability of drainage layer is confirmed,which provides a basis for risk assessment.