| Municipal solid waste incineration is a resource-based and harmless method to dispose of municipal solid waste which is widely used in China.Yet,due to the high water content（50～60%）of solid waste,incineration power plants usually ferment the waste in storage pits for 6～10 days to increase the calorific value of the waste.The natural dehydration of the waste produces a large amount of leachate.Therefore,the effective treatment of leachate from the incineration power plant has become a social problem.Nowdays,double membrane process（NF/RO）,membrane bioreactor（MBR）and multi-effect evaporation are widely used to treat leachate.However,due to the high content of organic matter in the leachate and blockage of the pipeline,membrane process needs to be cleaned constantly which resulted in high treatment costs.With high treatment efficiency,mature and stable technology and low cost,the"flocculation+activated sludge process"is a promising method of leachate treatment.The leachate treatment by adding traditional flocculant has some disadvantages,such as slow settling speed,long sedimentation time,loose flocs,small volume of supernatant,and low removal efficiencies of chemical oxygen demand（COD）and ammonia nitrogen（NH3-N）.Sequencing batch activated sludge process（SBR）,as a mature biological treatment process,is widely used in biological denitrification and degradation of organic compounds.However,due to the high salinity of leachate,the traditional sewage treatment plant can not adapt to such high salinity,resulting in dewatering and loss of biological activity.Therefore,how to make flocculation pretreatment complete flocculation and sedimentation in a short time and achieve efficient solid-liquid separation,and how to effectively remove COD and nitrogen from leachate supernatant under the condition of high salinity by SBR process has become an urgent problem to be solved in"flocculation+SBR"process.In view of inorganic mineral material bentonite（PRT）has high gravity force and adsorption effect,PRT was introduced into the flocculation process as colloid,Polyaluminum chloride（PAC）formed positively charged hydroxide in the process of hydrolysis,which neutralized,catched and absorbed pollutants in the leachate.At the same time,cationic polyacrylamide（C-PAM）maked small flocs polymerize into larger flocs and quickly settled down.The primary intensified flocculation pretreatment was realized through the synergistic effect of PRT,PAC and C-PAM.The activated sludge with high salt-tolerant was inoculated into the SBR reactor to construct the process of"Primary intensified flocculation pretreatment+High salt-tolerant activated sludge SBR"to treat leachate.Through the flocculation experiment of leachate with traditional flocculants polyaluminum chloride（PAC）and cationic polyacrylamide（C-PAM）,the flocs floated up and could not be separated after flocculation.When the optimum dosage of PRT,PAC and C-PAM was 8g/L,32m L/L and 20m L/L,the COD,turbidity,SS,TP and NH3-N of the supernatant were 5941mg/L,10.6 NTU,50 mg/L,1.76 mg/L and 279.6 mg/L,respectively.And the removal efficiencies were 72.3%,97.6%,93.8%,97.5%and 18.4%,respectively.Flocculation sedimentation reached 7.2%floc volume ratio in 1 min.Due to the shortening of the precipitation time,the release of organic pollutants from the flocs was greatly reduced.Through GC-MS’s qualitative and quantitative analysis,more than 90%of toluene and other volatile organic compounds could be removed by flocculation.And the removal efficiencies of caproic,heptanoic and caprylic were 42.1%,29.5%and 28.5%,respectively,which was basically consistent with the COD removal efficiency of 72.3%.Furthermore,the heavy metals such as Mn,Cu,Zn,Cd,Pb,Ni,Cr,Hg,Mg and Fe in the supernatant decreased to 0.342,0.032,0.421,0.061,0.053,0.410,0.036,0.002,9.797 and 12.197mg/L,respectively.The removal efficiencies were 42.1%,91.8%,91.2%,20.8%,28.4%,30.7%,33.3%,66.7%,7.36%and 46.1%,respectively,which greatly reduced the impact of heavy metals on subsequent biochemical treatment.The 16S r DNA analysis of the inoculated activated sludge with high salt-tolerant showed that Defluviicoccus,Actinomarinales,Vibrio,Trichococcus,Thauera,Betaproteobacteria and Truepera had a strong ability of biological nitrogen and phosphorus removal.In the SBR reactor,when salinity was 12.2 and C:N:P was controlled at 100:5:1,the concentration of COD and NH3-N in the effluent was reduced to 561 and 1mg/L,and the removal efficiencies of COD,NH3-N and TN were 90.7%,99.6%and 25.7%,respectively.Compared with traditional activated sludge,high salt-tolerant activated sludge had the advantages of shortening domestication and culture time and high ammonia nitrogen removal efficiency.In summary,the process of"Primary intensified flocculation pretreatment+High salt-tolerant activated sludge SBR"can provide a theoretical basis and basic data for the treatment of leachate from incineration power plant. |
