Study On The Removal Of Heavy Metal From Land Fill Leachate By Coagulation And Adsorption

Domestic landfill treatment method is used widely because of its simple way and investment saving. However, with increasing the amount of waste landfill, leachate from the landfill site for the harm of the ecological environment and human also increasingly prominent, especially the harm of heavy metals. Conventional biological treatment method can be a very good degradation of leachate in the indices such as COD, ammonia nitrogen and chroma, but little on the high concentration of heavy metal removal effect. Coagulation with use of adsorption method can effectively reduce the content of heavy metals in landfill leachate, and fewer emissions to the environment.Polymeric ferric sulfate (PFS) is widely used in various kinds of water treatment technology because it has advantages of floc forming speed, the density of particles sedimentation speed, raw water temperature and pH value wide application range, good effect of sludge dewatering, synthetic raw material widely and low price. Fly ash is a good adsorbent that are popular with water treatment workers because their large specific surface area, good adsorption capacity and cheap sources, as well as advantages of the acid modified fly ash has better adsorption capacity. In this paper, a domestic waste treatment plant in Jinzhong city, Shanxi Province in the leachate regulating pool as the research object. Choosing PFS as coagulant, acid modified fly ash as adsorbent for the research of coagulation and adsorption under the best conditions on heavy metal ions removal of Cd and Pb.Through jar experiment:(1)when the dosing amount of coagulant PFS is600mg/L, the reaction solution pH value of6.0for heavy metal Pb removal effect is best; PFS dosing quantity is600mg/L, the reaction solution pH value of8.0to remove heavy metal Cd works best.(2) when the additive amount of acid modified fly ash was12.0g/L, the pH of the reaction solution was8.0, the adsorption reaction time for60min of removing heavy metal Pb is best; When the amount of additive of fly ash is12.0g/L, pH value of8.0, adsorption reaction time of120min is the best to eliminate the heavy metal Cd.(3) after the first coagulation then adsorption experiment process of two kinds of heavy metal ions removal effect is very good, the best conditions of removal rate reached more than98%. Under the condition of optimum coagulation and adsorption experiments, the optimal dosing quantity of adsorbent is10.0g/L, the effect is best, to eliminate the heavy metals Cd and Pb removal rate reached98.20%and98.97%respectively; the Pb ion water concentration (0.05mg/L) is under the GB16889-2008standard of the prescribed discharge concentration (0.1mg/L).(4) synchronous coagulation adsorption of orthogonal experimental results show that the influence of heavy metals Cd and Pb removal effect of the most important factor is the pH of the reaction solution, followed by the additive amount of adsorbent, and at last the dosing amount of coagulant. The best combination for removing heavy metal ions Cd is:coagulant dosing quantity is600mg/L, adsorbent additive amount of12.0g/L, the solution pH value of8.0, under the optimal combination of removal rate can reach more than94.48%. The best combination for removing heavy metal ions Pb is:coagulant dosing quantity is600mg/L; adsorbent additive amount of10.0g/L, the solution pH value of8.0, under the optimal combination of removal rate is97.27%.Through the experimental study can be concluded that PFS coagulation and adsorption of acid modified fly ash can remove high concentrations of heavy metals in the leachate Cd and Pb. Although synchronization coagulation adsorption technology for heavy metal ions removal is worse than first coagulation then adsorption process, but it is better than simple coagulation and adsorption process. Therefore, this technology can be used as a pretreatment method for the actual engineering application.