Treatment Of Landfill Leachate Using Coagulation/Adsorption-Anoxic-Membrane Bioreactor

Landfill leachate is characterized by high concentration of pollutants, complex components and difficultly treatment. It would potentially contaminate the city residential environment and the groundwater if left appropriately untreated before being discharged into the receiving aquatic environment. Thus, it has become the emphasis and difficulty of sewage treatment fields in recent years.Over the years, new technologies for leachate treatment have gained a rapid development. Membrane bioreactor (MBR) and other biological treatment have gradually become the mainstream technology. This study adopts physicochemical and biochemical integrated technology for the treatment of landfill leachate. In the physicochemical treatment technology, an integrated treatment process including coagulation process using inorganic polymer coagulant and organic polymer flocculants and adsorption process with modified flyash is designed for the pretreatment of landfill leachate. A combined process incorporating with anoxic-aerobic submerged MBR was selected during the biological treatment process. Finally, the removal efficiency of typical pollution in leachate was investigated to study feasibility of the integrated technology in treatment landfill leachate.In physicochemical technology process, the efficient inorganic coagulant and organic was selected during the orthogonal experiment. Afterwards, the optimum coagulation process operation parameters were selected after the single factor experiments. The experiment results showed that the optimum coagulant and flocculant is polymeric aluminum ferric sulfate (PAFS) and cationic polyacrylamide (CPAM), respectively. When the coagulant dosage is1300mg/L, the flocculant dosing8mg/L, the coagulate efficiency is optimal after a30minutes static sink. In the adsorption process, after acid and alkali modification, the adsorption efficiency of flyash achieved its best performance when its dosage is1.6g/L and reaction time is25minutes.In biological treatment process, a series of orthogonal experiments were designed and conducted to investigate the system performance under different levels of hydraulic retention time (HRT), organic load fill (OLR), aeration intensity. The experiment results showed that the improvement of three factors above can increase the removal efficiency of CODcr, ammonia nitrogen in leachate and alleviate the membrane fouling rate. The raising of the OLR would reduce the removal efficiency of ammonia nitrogen. The interaction of the OLR and HRT, the aeration intensity and OLR, respectively, shows the significant effect on removal of CODcr and ammonia nitrogen.In addition, the biodegradability of leachate was also investigated through this study. The results showed that coagulation and adsorption process can both improve the biodegradability of leachate. The effects of three typical heavy metal ions (Cu2+, Pb2+and Ni2+) were also studied. The study indicated that the microorganism activity in the reactor were inhibited when the concentrations of Cu2+, Pb2+and Ni2+are5mg/L,10mg/L and10mg/L, respectively. There would be a synergistic inhibition on microbial respiration when Cu2+and Ni2+are co-existence.