The Inactivation Effect Of UV-NaClO Combined Disinfection On Pathogenic Microorganisms And ARGs Removal In Sewage

Disinfection,as the last process of sewage treatment,plays an important role in inactivating pathogenic microorganisms and reducing the spread of water-borne diseases.At present,ultraviolet(UV)disinfection commonly used in sewage treatment is greatly affected by the water quality,no continuous disinfection ability,after disinfection will appear the phenomenon of microbial resurrection;sodium hypochlorite(NaClO)disinfection can not inactivate giardia,cryptococcus and other microorganisms,and can produce disinfection by-products(DPBs)in the process of disinfection.It is of great significance to develop appropriate wastewater disinfection technology to prevent the water quality safety in the process of wastewater discharge or reuse.In order to make up for the disadvantages of UV and NaClO disinfection,this studytook the filtered secondary effluent of sewage treatment plant as the research object,and investigated the feasibility of UV-NaClO combined disinfection technology,which firstly subjected the secondary effluent to UV radiation and then carried out NaClO disinfection.The disinfection effects of UV,NaClO and the combination of UV and NaClO on coliforms,ARB and ARGs and the changes of DBPs production were studied at different doses.The characteristics of photoreactivation and dark repair of microorganism after disinfection at different doses of UV were analyzed.The effects of NaClO disinfection dosage and disinfection time on the disinfection effect were also analyzed.(1)Study on the inactivation effect of UV-NaClO combined disinfection on coliforms in secondary effluent of sewage treatment plantUV disinfection could effectively inactivate coliforms,and the higher the dose,the higher the inactivation rate of coliforms.However,after UV inactivation,the three kinds of coliforms could be revived under light and dark conditions,and the ability of photoreactivation and dark repair of coliforms is negatively correlated with the UV disinfection dose.NaClO disinfection could also effectively realize the inactivation of coliforms,and the inactivation effect was related to the disinfection time and the disinfection dose.The effect of UV-NaClO disinfection on coliform colony inactivation was significantly better than that of UV disinfection alone or NaClO disinfection.(2)Study on DBPs generation in secondary effluent of wastewater treatment plant by UV-NaClO combined disinfectionThe production of trihalomethanes increased with the increase of NaClO dosage.When the NaClO dosage was greater than 10 mg/L,the production of THMs showed a trend of significant increase.When NaClO dosage was constant,the generation rate of DBPs gradually slowed down with the prolonging of disinfection reaction time,and the DBPs production gradually stabilized after 30 min of reaction.In UV-NaClO combined disinfection,the combination of a lower dose of UV and NaClO could achieve the same disinfection effect under the condition of a higher dose of NaClO alone.Therefore,UV-NaClO disinfection could reduce the dosage of NaClO,and then reduced the generation of DBPs.(3)Study on inactivation effect of UV-NaClO combined disinfection on ARB in secondary effluent of sewage treatment plantThe higher the UV dose,the higher the inactivation rate of ARB.However,after UV inactivation,part of ARB could be revived under light and dark conditions.The photoresuscitation and dark repair abilities of ARB were negatively correlated with UV disinfection dose,but UV disinfection alone could not effectively control the spread of ampicillin resistant bacteria.NaClO disinfection could effectively realize the inactivation of ARB.When the reaction time of NaClO disinfection was the same,the number of ARBs decreased with the increase of NaClO disinfection dose.When the disinfection dose of NaClO was fixed and the disinfection reaction time was 30 min,the inactivation rate of ARB gradually tended to stabilize.When UV or NaClO disinfection was used alone,four types of ARB were completely inactivated,requiring UV dose of 80 m J/cm~2or NaClO dose of 30 mg/L.In the combined UV-NaClO disinfection,only 15 m J/cm~2 UV and 10 mg/L NaClO combination could realize the complete inactivation of the four ARB colonies.(4)Study on the removal effect of UV-NaClO combined disinfection on ARGs in secondary effluent of sewage treatment plantUV or NaClO disinfection could remove 18 kinds of ARGs in the secondary effluent of sewage treatment plant.When the UV disinfection dose was 20 m J/cm~2,the removal effect of ARGs was not significant,only 48.1 of ARGs was removed,and when the UV disinfection dose was 100 m J/cm~2,81.2%of ARGs could be removed.When NaClO disinfection dosage was 50 mg/L,about 99.7%ARGs could be removed.The repair ability of ARGs after UV disinfection was negatively correlated with UV disinfection dose.UV-NaClO combined disinfection can achieve a large number of ARGs removal in the case of low NaClO disinfection dose.When 20 m J/cm~2 dose of UV was used for radiation and 20 mg/L NaClO was added,98.5%ARGs could be removed.