Studies On The Combined Process And Its Treatment Characteristics Of Leachate From Waste Incineration Power Plant

In the waste incineration plant,leachate was generated by the fresh waste fermentationwhich could increase the waste calorific value,and it had the characteristics of dark greencolor,obvious excitant odour,high SS content,high ammonia nitrogen concentration andrefractory components.Disposal of leachate is a difficult problem in the field of wastewatertreatment,and the main process of leachate treatment included biological treatment,coagulation, advanced oxidation technology and reverse osmosis,et al.it was difficult toachieve the ideal processing effect for a lot of efficient biological treatment processes whichwere developed in recent years.The effluent have high organic matter concentration, lowBOD,and it was needed to further treatment.The membrane treatment process was widelyused to treat the effluent of biological treatment.However, due to the effluent with high COD,SS content,the life of the membrane was seriously influenced by organic pollution after themembrane treatment.Therefore the development of new technology or the improvement oftraditional process had become the current development trend.Therefore,a process combined with physicochemistry biological treatment and advancedtreatment was employed to treat the leachate from incineration plant.The combined processperformance characteristics of coagulation and biological treatment, the dynamics of upflowanaerobic sludge bed (UASB) which treated the leachate and combination process foradvanced treatment of biotreatment effluent of landfill leachate were investigated,respectively,and the dissolved organic matters (DOM) composition structure characteristicsand the mechanism were also analyzed. Research results were as follows.(1) The study of combined process performance characteristics of coagulation andbiological treatment had showed,with the PAC as coagulant,as its dosing quantity (effectiveconstituent), initial pH were600mg/L,7.0,respectively, the COD removal efficiency ofleachate in coagulation process reached20%,and the influent COD (17825mg/L) could bedegraded to the effluent COD (14260mg/L).The combined process of UASB,SBR,aerobic1and aerobic2was employed to treat the effluent of coagulation pretreatment.The process unitsof significant cut for COD and ammonia nitrogen were UASB and aerobic2in the combinedprocess,respectively,and the removal rates for COD and ammonia nitrogen were70%and80%.Under the optimal process condition, the removal rates of COD and ammonia nitrogenreached94%and98%in the combination technology of coagulation and biologicaltreatment,respectively, and the effluent COD,ammonia nitrogen were965and25mg/L,respectively. (2) The dynamics study of upflow anaerobic sludge bed (UASB) which treated theleachate had showed,When the hydraulic retention time (HRT) of UASB shortened graduallyfrom6d to4,3,2,1and0.5d, COD removal rate decreased gradually from76%to30%.Inthe Monod equation,the yield coefficient Y,death rate constant Kd, maximum specific growthrate μ were0.0563mg cells COD/mg COD,0.00328d-1,0.128d-1,respectively.In the ModifiedStover-Kincannon equation,substrate maximum utilization rate coefficient Rmaxand saturatedcoefficient KBwere10,11.063g COD/(L day),respectively.In the Grau second-ordermulticomponent substrate removal equation,a larger kinetic parameter a (a=influentconcentration/(substrate removal rate*microorganism concentration)) was obtained,its valuewas1.1266.It showed that UASB reactor had strong shock load capability.In addition,by thecomparison of the predicted values and the actual value of three kinds of substratedegradation dynamics model, it was found the predicted value and actual value of Grausecond-order equation was the closest,the linear correlation coefficient was0.999,and theGrau second-order equation was best-fit for the prediction of UASB performance.(3) The studies on combination process for advanced treatment of biotreatment effluentof landfill leachate indicated,with the PAC as coagulant, as its dosing quantity (effectiveconstituent),initial pH were600mg/L,6.0,respectively, the COD removal efficiency ofleachate in coagulation process reached50%, which could reduce the refractory CODeffectively and would be conducive to shorten the treatment time in subsequentelectrochemical process. Following this, electrochemical process was used to treat thecoagulation effluent. Under the optimal electrochemical process conditions: pH6.0, current I1.2A (current density18.18mA/cm2),Cl-dosing quantity1000mg/L, plate distance2cm,electrolytic time30min,COD removal efficiency reached36%along with the content ofrefractory toxicants decreased significantly,and leachate biodegradability TbOD/CODincreased from10%to maximum64%. Finally,the Continuous Stirred Tank Reactor (CSTR)was employed to further treat electrolysis effluent, and the effluent COD,ammonia nitrogenand chromaticity were100-150mg/L,7-13mg/L and25times, respectively.(4) The characteristics study of dissolved organic matters in waste incineration plantleachate treatment process which included coagulation1,UASB,SBR,aerobic1,aerobic2,coagulation2,electrochemistry and aerobic3showed,the total removal efficiencies of CODand NH4+-N achieved approximately99%. The influent COD (17825mg/L) and NH4+-N(1946mg/L) could be degraded to the effluent COD (57mg/L) and NH4+-N (5mg/L)respectively. In the combination process, the total COD removal efficiencies of HA, FA andHyI reached approximately99%. The process units of significant cut for HA, FA, HyI were coagulation2, anaerobic, granular activated carbon(GAC), respectively. The removalefficiencies for HA, FA, HyI reached86%,77%,84%, respectively. The effluent COD valuesof HA, FA and HyI were10,23and6mg/L, respectively, FA of small molecular weight wasthe major component. The DOM ultraviolet absorbance value dropped significantly during thetreatment. E254and E253/E203decreased from1.55and0.64to0.012and0.024, whichindicated that the aromaticity and complexity of DOM reduced significantly.The content ofaliphatic chain increased gradually during the treatment process. In addition, E300/E400andE465/E665increased from2.65and2.17to9.78and8.03, which also illustrated that thehumification and aromatization degree reduced constantly.