Research Of Removal Efficiency Of Environmental Estrogens In Large-scale Municipal Wastewater Treatment Plant And Bioaugmentation In Low Environmental Temperature

Environmental Estrogens?EEs?are one kind of typical pollutants in the aquatic environment.Their characteristic features are low concentration,great toxic and side effects,which bring potential biosafety and environmental safety problems.Therefore,they have become a crucial issue of ecological protection in the aquatic environment.The essay considered the occurrence and removal of EEs,microbial community and functional information in two types of biological systems,which involved activated sludge?AS?sewage treatment and sludge anaerobic digestion?AD?respectively.It is suggested to select commercial nitrifying bacteria product do the bioaugmentation research under low water temperature condition at AS biosystem to investigate the impacts on nitrification function and the activity and removal rate of EEs through bioaugmentation in municipal waste water treatment plant?MWWTP?.Detecting the EEs activity in wastewater by three bioassays,which include recombinant yeast,fancy carp VTG,and male fancy carp GSI,it was shown that these three bioassays methods had consistent results.Based on bioethics and manipulation considerations,this study selected recombinant yeast assay as the EEs bioassay method,and it is found that 93.5%⁹7.7%of the active equivalent of EEs existing in the liquid phase.Using GC-MS method to test EEs compounds concentrations in samples,it is found that the detection rates of bisphenol A?BPA?,17?-ethinylestradiol?EE2?,estrone?E1?and 17?-estradiol?E2?were 100%,33%,28%and 17%respectively.However,the 4-n-nonylphenol?4-n-NP?and 4-n-octylphenol?4-n-OP?were undetected.As the main representative compounds of EEs,the mass concentrations of BPA were 611¹420 ng/L and 110⁴06 ng/L respectively in raw wastewater and secondary sediment tank effluent.The essay focused on the nitration function,EEs activity removal ability,and microbial information of anoxia-anaerobic-aerobic?A²O?biosystem at different seasons.It is shown that the biosystem in the winter owed the lowest ammonia nitrogen removal rates?90.6%?and EEs activity biodegradation rates?76.9%?.Moreover,microbial richness and diversity were also the lowest.In the different seasons,the diversity of microbial communities is quite different.Six metabolic pathways such as lipid metabolism and biodegradation and metabolism of exogenous substances vary by more than 5%.Whereas,three main metabolism functions associated with amino acid metabolism,carbohydrate metabolism,and energy metabolism had no significant differences?variation ranges lower than 5%?.In summer,the ranking of nitrification capacity and EEs activity removal capacity in different process of sludge retention time?SRT?and hydraulic retention time?HRT?in AS system was:A²O+contact oxidation combined process?IV series?>A²O process with long SRT and HRT??series?>A²O process with short SRT and HRT?series??.There was no significant difference in the diversity of microbial communities in AS system between different technologies,SRT,and HRT.According to the functional genes of eight known EEs biodegradation enzymes,using known EEs biodegradation bacteria,Integrated Microbial Genomes&Microbiomes?IMG?system and PICRUSt software to analyze the 16S rDNA-PCR amplicon pyrosequencing testing results of different seasonal activated sludge.It is proposed that the three assessment models of EEs degradability of microbial communities including"abundance of known EEs degrading bacteria","EEs degradability index predicted by community dominant bacteria"and"abundance of EEs degradative genes predicted by PICRUSt".Based on the sequencing results of AS system??,?and?series?with different technologies in summer,SRT and HRT,the PICRUSt predicted EEs degradation gene abundance was consistent with the second-order removal efficiency of measured EEs activity,indicating that the model is suitable for evaluating AS systemic microbial EEs degradation ability.The concentrations of ammonia nitrogen,total phosphorus,and total nitrogen in the mixed sludge?primary sedimentation+concentrated residual sludge?after anaerobic digestion were 31,48 and 23 times before digestion,while the activity of EEs was slightly higher than that before digestion.Therefore,it is concluded that the reflux of the aqueous phase could not aggravate the load of EEs in the AS system.The genetic diversities of AS and AD systems predicted by PICRUSt were 0.174%-0.183%and 0.184%-0.202%respectively.However,due to the different biological reaction conditions,the diversity of microbial communities and the main metabolic function"carbohydrate metabolism"in AS and AD systems are quite different.Based on the above studies,with the purpose of improving the total removal rate of EEs from WWTPs,this research chose AS systems with poor EE activity removal as test objects and utilized commercial nitrifying bacteria as bio-synergist for nitrification under low water temperature,which is practical and significant for EEs degradability enhancement engineering test.Before the experiment,the secondary removal rates of AS systems to EEs were 84.1%,89.2%,and 89.2%respectively in the early and final stages of feeding.The degraded abundances of EEs by PICRUSt were 0.178%,0.185%,and 0.185%respectively.Apart from this,Nitrification Functional gene indexes were 0.30,0.33,and 0.36 respectively.Before and after the experiment,the average concentrations of ammonia nitrogen in effluent from the second sedimentation tanks were 15.6 mg/L and 4.37 mg/L respectively,the mean concentrations of nitrate nitrogen were 3.97 mg/L and 0.41 mg/L respectively,and the average nitrate-nitrogen concentrations were 5.48 mg/L,15.45 mg/L.Moreover,the ammonia nitrogen and nitrate nitrogen concentrations decreased,while the nitrate-nitrogen concentration increased.It is considered that the addition of nitrobacteria had no significant effect on the main metabolic function,COD_Cr removal efficiency,sludge yield coefficient and microbial equivalence of AS microorganisms.The nitrification-like functional gene index increased,and the ability of nitrate nitrogen to convert to nitrate nitrogen increased.EC:1.14.13.-and E1.14.-.-are the major BPA-degrading genes,adding agentia for germs,the index of key functional genes of the second type of metabolic pathways of BPA in the predominant microflora of AS system?E1.14.-.-and E4.2.1?rise.When the sludge load of BPA was increased from8.83 ng BPA/kg MLSS/d to 21.06 ng BPA/kg MLSS/d during the interim term of agentia addition,the secondary BPA removal rate was still maintained high reduction,which was 105.9 g/d.In the final stage of EEs degradability enhancement,the primary sedimentation tank was disturbed abnormally,resulting in a decrease of MLVSS to MLSS ratio from 0.75 to 0.57.MLSS increased from 2000 mg/L to 4300 mg/L.On the 12th day after turbulence,the effluent NH₃-N in the I series secondary settling tank was1.1 mg/L,and the nitrification ability of the AS system was recovered.In conclusion,the method of utilizing nitrifying bacteria bio-efficiency at low water temperatures could improve the nitrification capacity of AS systems in large urban sewage treatment plants,and it also maintains the ability at a relatively high level for a long time.It is believed that the removal of EEs activity is enhanced,and the anti-load disturbance ability in systems was intensified.Moreover,the recovery period of the system after the disturbance was shortened,which provides the essential engineered data for the application of bio-efficiency technology.