Research On Coagulation-ozone-two-stage Anaerobic Ammonium Oxidation Technology For Treating Landfill Leachat

Landfill leachate belongs to refractory organic wastewater,which has the characteristics of large change in water quality,high ammonia nitrogen and high COD.The treatment process has some problems,such as difficult cultivation of microorganisms,high treatment cost and short service life of membrane separation equipment.Anaerobic ammonia oxidation（ANAMMOX）can be applied to the biological denitrification of landfill leachate together with shortcut nitrification process,which has a good application prospect.Seven typical domestic waste landfills（A-G）in Guizhou Province were selected to analyze the water quality characteristics of landfill leachate.The characteristics of organic matter in landfill leachate were analyzed by Fourier infrared spectroscopy and three-dimensional fluorescence spectroscopy;Then,the"Coagulation-Ozone-Two-Stage Anammox"landfill leachate treatment system is constructed to study the removal efficiency of the system for COD,ammonia nitrogen,total nitrogen and chromaticity in landfill leachate.The changes of organic components are analyzed by Fourier infrared spectroscopy and three-dimensional fluorescence technology,and the microbial action mechanism of the two-stage anaerobic ammoxidation reactor is analyzed by macrogenome technology.The main conclusions are as follows:（1）Water quality characteristics of landfill leachate from domestic waste landfills in Guizhou ProvinceThe average values of COD,ammonia nitrogen,total nitrogen,BOD₅ and total phosphorus in the leachate of domestic waste landfill in Guizhou Province are 3328.14mg/L,1642.34 mg/L,2562.00 mg/L,1031.89 mg/L and 71.10 mg/L respectively.The content of biodegradable organic matter accounts for 31%aboutly.The comprehensive pollution level of heavy metals in landfill leachate is a severe pollution level,in which the pollution level of total cadmium is the highest,while the pollution level of total lead is greatly affected by the region,and hexavalent chromium and total mercury are basically at a safe level.The dissolved organic matter in landfill leachate is mainly humic acid like substances,accounting for more than 80%of the total dissolved organic matter.In addition,there are many organic functional groups in landfill leachate,mainly including alcohol COH out of plane bending,olefin（CIS）CH out of plane bending,C-O-S symmetric stretching of sulfate R¹O-SO₂-OR²,carboxylate COO antisymmetric stretching and OH stretching functional groups of carboxylic acid dimer.（2）Construction and efficiency analysis of coagulation-ozone-two-stage anammox treatment system"Coagulation-Ozone-Two-Stage Anammox"is used to treat landfill leachate.The average removal rates of COD,ammonia nitrogen,total nitrogen and chromaticity in effluent are 81.98%,95.64%,93.31%and 97.70%respectively.In the"Coagulation-Ozone"treatment technology,the optimal control parameters for coagulation are 10g/LPAC+6 mg/LPAM,the optimal aeration time for ozone is 48 h,and the effluent COD,ammonia nitrogen,total nitrogen,and chromaticity are average The removal rates were56.86%,32.74%,38.49%,and 98.55%,respectively.On the basis of"Coagulation-Ozone",the first-stage anammox reactor adopts ABBR reactor,and its activated carbon packing group has the best treatment effect.69.62%,66.35%,97.66%.On the basis of primary anammox treatment,the secondary anammox reactor adopts UASB reactor,in which the operation mode of adding nitrite has the best removal effect on total nitrogen,but the removal effect on COD and chromaticity is not obvious.（3）Study on the treatment system mechanism of coagulation-ozone-two-stage anammoxThe removal of TOC,UV₂₅₄ and DOM in landfill leachate by"Coagulation-Ozone-Two-Stage Anammox"is mainly realized by coagulation and ozone treatment.The removal effect of microorganisms on these pollutants is not significant.The average removal rates of TOC and UV₂₅₄ are 80.76%and 92.61%respectively.Through infrared spectrum and three-dimensional fluorescence spectrum,it is found that coagulation treatment can not change the composition and structure of pollutants,while ozone treatment can change the structure of some organic substances in wastewater.The dominant genera of microorganisms in the primary anammox reactor mai-nly include Methanothrix,Nitrosomonas and Candidatus＿Kuenenia,the detected ana-mm ox bacteria are mainly distributed in A4 cell,which is Candidatus＿Kuenenia（34.80%）。The dominant genera of microorganisms in the secondary anammox reactor ma-inly include unclassified＿f＿＿Candidatus＿Brocadiaceae、Ignavibacterium、unclassi-fied＿p＿＿Chloroflexi、unclassified＿p＿＿Proteobacteria,anaerobic ammonia oxidizing bacteria are mainly unclassified＿f＿＿Candidatus＿Brocadiaceae（9.91%）、Candidatus＿Kuenenia（4.44%）。The nitrogen metabolism processes in the two-stage ANAMMOX reactor include ammonification,dissimilatory nitrate reduction,assimilated nitrate reduction,denitrification,nitrification,nitrogen fixation,and ANAMMOX.Fifty functional genes related to nitrogen metabolism were detected in the primary anammox reactor,among which the anammox functional genes（hzs A,hzs B,hzs C and hdh）in the A4compartment were relatively abundant in nitrogen metabolism functional genes.The highest degree of relative abundance is 13.16%.The secondary anammox reactor detected 49 functional genes related to nitrogen metabolism,among which the relative abundance of 4 anammox functional genes was 5.71% after adding nitrite.