Directional Acclimation And Mechanism Of Nitrifying Biomass Resistant To Biological Inhibition Of Phenolic Pollutants

With the rapid development of national economy,the discharge of municipal and industrial wastewater has increased dramatically,and the pressure on wastewater treatment has continued to increase.Most municipal wastewater treatment plants will receive some industrial wastewater containing phenolic pollutants through the municipal pipeline network in the actual operation process.During normal operation of factories,industrial wastewater should be pretreated and then be incorporated into the municipal pipe network after meeting the standards.However,sudden accidents,such as fluctuation of industrial raw material composition and failure of enterprise wastewater treatment facilities often lead to the discharge of industrial wastewater into the municipal wastewater treatment system without effective pretreatment.Nitrification is one of the most important processes in the wastewater treatment system of municipal wastewater treatment plant.As nitrifying bacteria grow slowly and are susceptible to external factors,their biological activity will be severely inhibited or even inactivated after being impacted by phenolic pollutants in the wastewater.Besides,it is difficult to recover effectively in a short time,thus resulting in excessive NH₄⁺–N concentration of effluent,causing a major sewage treatment accident.In order to reduce the impact of phenolic pollutants in the industrial wastewater on the nitrification ability of municipal wastewater treatment plants and carry out effective prevention work,it is of great theoretical and practical significance to study the domestication of nitrifying biomass which can resist the inhibition of phenolic pollutants,and to explore the mechanism.In this study,two representative phenolic compounds,phenol and 2,4,6-TCP?TCP?,were selected as research objects,and activated sludge capable of resisting the inhibition of phenol and TCP on nitrifying bacteria was acclimated respectively,which can also keep high nitrification rate.The attack of toxic pollutants is often sudden,based on this situation,whether the acclimated nitrifying sludge has sustained resistance to phenol or TCP was studied and the mechanisms of the phenomenon were discussed.Main research conclusions include:?1?Nitrifying biomass capable of resisting inhibition of phenol and TCP were acclimated.After biological acclimation of normal nitrifying biomass with phenol and TCP for nearly 2 months,nitrifying biomass with phenol and TCP resistance was obtained.Comparing with normal biomass,nitrification ability of acclimated biomass was still retained when it was suddenly exposed to phenol or TCP.To be specific,when initial concentration of 4.2 m M phenol was added to the acclimated biomass,the nitrification rate decreased slightly?about 32%?,but phenol was effectively degraded.Normal biomass almost lost its nitrification ability.Moreover,once phenol was removed,its nitrification ability could quickly recover to the initial level,while normal biomass recovered only 53% in a week.The acclimated biomass had 2.3-fold faster nitrification rate than normal biomass when exposed to 0.28 m M TCP,and it also achieved effective TCP removal.After TCP removal,the nitrification ability of acclimated biomass recovered completely after one week,while that of normal sludge only recovered by 71%.?2?It was found that normal nitrifying biomass acclimated by phenol and TCP can continuously resist the biological inhibition of phenol and TCP.At intervals of one week,two weeks and one month,phenol or TCP were added to the acclimated biomass system?no addition during the intervals?.It means acclimated biomass could continuously withstand the attack from phenol and TCP,maintain its nitrification ability,and had phenol or TCP degradation function.To be specific,when acclimated biomass was exposed to phenol or TCP at intervals of one or two weeks,the nitrification rates did not decrease significantly.Although their nitrification was weakened when they were attacked again after a month,they recovered almost to the initial nitrification rate after a week's recovery.?3?The sub-culturing acclimated biomass still had the ability to degrade phenol and TCP.In the absence of phenol or TCP,using glucose as carbon source,5 generations of acclimated biomass were cultured.The acclimated biomass still had the ability of simultaneously degrading phenol,TCP and NH₄⁺–N.?4?The microbial communities of nitrifying biomass with the ability of simultaneously degrading phenol or TCP and nitrification were analyzed.The results of high throughput sequencing showed that the diversity of microbial community was the main reason for the resistance of acclimated biomass to phenol or TCP inhibition.In addition to nitrifying bacteria,phenol or TCP degrading bacteria were also enriched in acclimated biomass,which alleviated the inhibition of phenol or TCP on nitrifying bacteria.In the process of sub-culturing,the comparative analysis of microbial communities in the first,third and fifth generation of biomass indicated that the acclimated biomass always contained nitrifying bacteria and heterotrophic bacteria capable of degrading TCP or phenol,although the key genera changed during subculturing.The interspecific cooperation of microorganisms enables the acclimated biomass to withstand the inhibition of target pollutants for a long time.?5?A method for recovering the nitrification activity of normal nitrifying biomass inhibited by phenol or TCP was proposed.Adding phenol-or TCP-acclimated biomass to the system inhibited by phenol or TCP can effectively enhance the system's ability to remove phenol or TCP and quickly recover its nitrification.