| Nitrogen and phosphorus are the main pollutants of domestic sewage.In recent years,the state has become more and more stringent on the quality of effluent from sewage treatment plants,and combined processes are gradually used for advanced sewage treatment.Traditional constructed wetlands will cause the effluent quality to be substandard.In this paper,the sulfur autotrophic denitrification technology is applied to the horizontal subsurface flow wetland system,and corncobs are added as an organic carbon source to construct an A/O biological contact oxidation-constructed wetland combined process system.A test study on decarbonization and phosphorus removal of simulated domestic sewage is aimed at strengthening the effect of deep denitrification and phosphorus removal of sewage.In the experiment,three-dimensional fluorescence spectroscopy was used to characterize the change process of dissolved organic matter(DOM)in the sewage treatment process,and the influence of the A/O biological contact oxidation reactor system on the removal of pollutants under different hydraulic retention times and reflux ratios was investigated.Under the condition of high ammonia nitrogen inflow,the system has the efficiency of nitrogen and phosphorus removal.Based on the sulfur autotrophic denitrification,R1 filled with processed pyrite,R2 filled with sulfur + corncob,R3 filled with sulfur + pyrite(1:4),and filled with sulfur + Cement R4,R5 filled with pyrite +corncob,R6 filled with the same pyrite as constructed wetland,and other six types of upflow reactors.The simulated sewage was tested for nitrogen and phosphorus removal,and the analysis and comparison of sulfur The by-products produced in nutrient denitrification are analyzed by microbial flora to prove the pollutant removal mechanism,aiming to find a suitable combination of fillers for use in sulfur autotrophic constructed wetlands.The main research contents and conclusions are as follows:(1)A/O biological contact oxidation-constructed wetland reactors are connected in series,using artificial inoculation and filming,the water temperature in the start-up phase is 26~29℃,and the dissolved oxygen in the aerobic pool is controlled at DO﹥2mg/L.0.2~0.5mg/L,the reflux ratio is set to 200%.Begin to use small flow for continuous water intake,and then gradually increase the flow until the design flow is 50L/d.After 20 days,the removal rate of NH4+-N,COD,TN,and TP by the A/O biological contact oxidation reactor reached 95%,90%,70%,and 50% respectively.The reactor was operating stably,and it was considered that the biofilm had been suspended.The maturity of the membrane marks the successful start-up of the A/O biological contact oxidation reactor.At the same time,the removal rate of NH4+-N,NO3--N and TP in the constructed wetland reaches about50%,90%,and 50%,and the COD concentration of the effluent is stable at about 15mg/L.The plants are growing well,marking the successful start of the constructed wetland reactor.(2)By adjusting the HRT of the A/O biological contact oxidation reactor to 11 h,16h,20 h,26h,and the reflux ratio of 50%,100%,200%,300%,respectively,the A/O biological contact oxidation reaction was investigated According to the treatment effect of the pollutants under different HRT and reflux ratios,the optimal HRT and reflux ratios of the A/O biological contact oxidation reactor were finally determined to be 20 h and 200%,respectively.Under the optimum HRT and reflux ratio,the A/O biological contact oxidation reactor maintains a C/N of 4,the ammonia nitrogen concentration in the influent is increased from 100mg/L to 250mg/L,and the TP concentration in the influent is gradually increased from 6mg/L to 12mg/L,to investigate the system denitrification and phosphorus removal effect of the combined process under the condition of high ammonia nitrogen inflow.With the continuous increase of influent ammonia concentration,the effluent COD and NH4+-N of the A/O section still maintain a good removal effect,but the removal effect on TN and TP is limited,and the effluent TN and TP cannot reach the national level A standard.When the effluent is treated by the constructed wetland,the TN concentration of the effluent is lower than 15mg/L,and the TP concentration is lower than 0.5mg/L,reaching the national level A standard.The removal of TN by constructed wetlands is mainly heterotrophic-autotrophic combined denitrification and denitrification.The carbon source released by the corncob is relatively stable,and the carbon source can be released stably for more than four months.The autotrophic denitrification effect of pyrite in the constructed wetland reactor is poor,and the start-up is very slow.When the experiment was carried out 200 days,the autotrophic denitrification of pyrite in the wetland began to occur,the final TN concentration of effluent stabilized at about 3mg/L.(3)Using three-dimensional fluorescence spectroscopy and combined parallel factor analysis methods,the changes of dissolved organic matter in the wastewater treatment process during the stable operation of the combined process reactor were investigated.The parallel factor method was used to successfully analyze the fluorescent substances in the effluent from each processing unit of the combined process reactor.The results show that there are mainly protein-like,fulvic acid-like and humic-like acid in the wastewater treatment process of the combined process reactor.The protein-like fluorescent substance gradually weakened from the water inlet to the final water outlet,and the effluent from the constructed wetland reactor mainly contained humic acid-like and fulvic acid-like acid.(4)Among R1 to R6,the sulfur-added reaction device has always maintained a high-efficiency removal effect on NO3--N,but its effluent by-product SO42-is relatively high and the p H is relatively low.Compared with unprocessed pyrite,the autotrophic denitrification of pyrite after grinding and processing starts faster.In the experiment,R6 began to have a certain effect on the degradation of nitrate nitrogen on the 74 th day,and finally had a certain effect on the degradation of nitrate nitrogen.The removal rate is stable at about 29%.The use of pyrite + corn cob combined filler has a better removal effect on nitrate nitrogen,and can accelerate the occurrence of pyrite autotrophic denitrification.During the reaction,it was detected that the effluent from R1 to R6 all had the accumulation of ammonia nitrogen,which may be related to the effect of DNRA.Sulfur has almost no removal effect on TP,while pyrite has a certain removal effect on TP.Grinding pyrite has the best removal effect on TP,with a removal rate of about 94%,and the average removal rate of TP by unprocessed pyrite is 46.5%.In the reaction device with corncob added,there is mainly protein-like fluorescence peak in the effluent,and the fluorescence intensity has a good linear relationship with the COD concentration.Therefore,the three-dimensional fluorescence technology can be used to quickly detect the COD concentration of the effluent from the sewage treatment process.(5)The 16 S rRNA high-throughput gene sequencing technology was used to analyze the microbial flora structure in R1~R6.At the phylum level,Proteobacteria is the most important functional bacteria in the R1~R6 system,and it was detected to be related to anammox and DNRA.The functional bacteria.At the genus level,functional bacteria Sulfurimonas and Thiobacillus related to sulphur autotrophic denitrification were detected in R1~R6,which confirmed the occurrence of sulphur autotrophic denitrification.Figure [39] table [6] reference [70]... |
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