The Research Of Chemical Blocking Occuring In Leachate Drainage System Of Municipal Solid Waste Landfill

The municipal solid waste landfill drainage system of leachate is usually filled by some obstruction.The blocking of drainage system will bring about the decreasing of drainage system volume and discharge capacity of drainage system. Afterwards leachate water level of landfill will rise higher than required water level of landfill leading to the instability of landfill dam and increasing the risk of leachate leaking into groundwater and external environment.This paper constructed an indoor model to simulate 5 degradation phases of anaerobic landfill to explore landfill drainage system obstructive degree by using Chengdu Changan landfill leachate as researched object. Based on the research result before, single factor experiment method is used to explore the changing rule of the factors influencing the blocking of the diversion system in methane-producing phase and stabilization phase of anaerobic landfill degradation. According to research result before, this paper also do some exploration about the best working condition of preventing waste landfill drainage system blocking. Researches show that:1. In the aerobic decomposition phase, transition phase of aerobic and anaerobic and acid fermentation phase, landfill column is in acidic condition (pH=5-6), the temperature is between 15-20℃. In this moment calcium and magnesium ions can not form sediment and calcium ion concentration is on the rise, the growth rate is between 14%-17%; In methane-producing phase and stabilization phase of anaerobic landfill degradation, landfill column is in neutral and alkaline (pH=7-8), the temperature is between 20-30℃,at this moment the calcium ion concentration in the leachate show downward trend, calcium ion concentration rate of change (Ca(out)/Ca(in) is 0.74. This means landfill column has already generated carbonate deposition and there is the probability of blocking of landfill drainage system. In the all phases of in door simulation experiment, the magnesium ion concentration in the leachate did not show too much change, magnesium ion concentration rate of change (Mg,out)/Mg (in)) is 0.9. In the landfill leachate pH range, magnesium can hardly block the landfill drainage system. The obstruction of landfill drainage system is mainly consist of CaC03 and the percentage of CaCO3 in obstruction is 52-76%. This indicating that calcium ion is the main contributor of obstruction.2.In methane-producing phase and stabilization phase, pH is 6-9, temperature is below 20-40 ℃. Obstructive degree of drainage system will go rise with the leachate temperature rises and go down with the pH go rise. The chosen leachate drainage system blocking influencing factors’primary and secondary relations is:pH> temperature; the minimum obstructive work condition is:pH=7, temperature is 40 ℃, and at this moment Calcium ion concentration rate of change (Ca(Out)/Ca(in)) is 0.895 and 0.868 respective.3. Based on indoor simulation experiment result, this paper proposed to regulate the leachate pH to preventing drainage system Obstruction. Through regulating the leachate pH value was proposed to control the basic ideas of diversion system obstruction. Specific measures include:①Optimize the design of the drainage system and material selection;② Use vertical air guide well to control leachate pH;③add scale inhibitor at the proper time to prevent the blocking phenomenon occurrence.This research can provide a new train of thought and basis in solving municipal solid waste landfill drainage system blocking.