| In present, the secondary pollution caused by the landfill leachate has been one of the important problems. Especially that the mature landfill leachate characteristic with bad biodegradability, massive ammonia nitrogen and complicated composition is particularly intractable. There exit many key issuess in the area such as higher running cost, lower removingrate for COD and ammonia nitrogen. The biochemical methods and chemical oxidation were combined organically to deal with landfill leachate in the study. The respected results were achieved through system study.The mature landfill leachate from a local landfill named Yangeryu landfill in Anshan of Liaoning province was taken as research project. The leachate was treated with the processes of ferric-carbon micro-electrolysis, shortcut nitrification, anaerobic ammonium oxidation, and Fenton oxidation. And the technical parameters, influencing factors and controlling parameters of each unit of the combined technique, nitrogen transformation of shortcut nitrification, and bio kinetics of shortcut nitrification and anaerobic ammonium oxidation were studied too.The landfill leachate was pretreated with the processes of ferric-carbon micro-electrolysis in the homemade reactor. The influence of pH, stirring, reaction time and the amount of iron and activated carbon added, the particle size, the ratio of iron to carbon, copper-catalyzed and electrolytes on iron internal electrolysis pretreatment were studied where the indicators such as COD, Chroma, ammonia, and biodegradability were taken as the criterion. It canbe found that Ferric-carbon could occur when pH was 7.5 to 8. The optimal terms were as follows:the added iron was 19g/L, the added carbon was 26.6g/L, the stiring time was 40min. After pretreatment of micro-electrolysis, COD removal efficiency was up to 43%, and chroma removal rate was above 61% and BOD/COD (B/C) was increased from less than 0.1 to 0.27. The action improved the biodegradability of the leachate greatly and created the conditions for the subsequent biochemical processing.Shortcut nitrification study was carried out on landfill leachate after ferric-carbon micro-electrolysis pretreated. The sludge qualified for short-cut nitrification was cultivated and acclimated successfully by controlling the conditions of temperature, pH, dissolved oxygen, sludge age, hydraulic retention time (HRT). The optimal parameters for the temperature was 30℃, pH was 8.0 to 8.5, the HRT for 11-13 hours, NH3-N volumetric loading 2.62g/(L.d). Then the operating state of the reactor was stable, nitrite accumulation rate reached 90% or more, most of biodegradable organics were removed in shortcut nitrification reactor. On this basis, the biological dynamics and nitrogen transformation of short-cut nitrification were studied systematically. Dynamics study with Grau model and Lawrence-Mc Carty model results the Kinetic parameter values and dynamics formulas.The drainage from shortcut-nitrification system then entered into anaerobic ammonium oxidation system which was started with the anaerobic ammonium oxidation sludge cultivated and reserved in environmental engineering laboratory of University of Science and Technology Liaoning. The temperature, pH, and NO2-N/NH3-N ratio were studied. The anammox bacteria were active and denitrification rate was comparable high when the temperature was maintained at about 35 ℃ in anaerobic reactor. The pH value directly affected reaction matrix. Anammox reaction worked best when the pH value was of about 8.0. NO2-N/NH3-N value was another factor that affects the reaction. It was favorable to anammox reaction when the ratio was 1.1:1 to 1.3:1 drawn from experiment.Fenton oxidation was adopted to dispose water from anaerobic ammonium oxidation system. The results showed that how to add hydrogen peroxide and the type of catalyst have a certain impact on the removal of COD in wastewater, but in a limited extent. The optimal terms of Fenton oxidation process were drawn from conditions experiment as follows:the initial pH was 7.0, H2O2/Fe2+was 4:1, the dosage of H2O2 was 30mmol/L and the reaction time was 2h.The landfill leachate was treated by the Internal Electrolysis-shortcut nitrification-ANAMMOX-Fenton oxidation joint process, the removal rate for NH3-Nwas above 99%, for total N was 65-75% and for COD was above 95%. the effluent quality reached the requirement of "water pollutant concentration limits discharged from existing and new municipal waste landfill" (GB16889-2008). |
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