| Organic micropollutants（MPs）are widely existed in the water environment.Although there is a low concentration in the water environment,their structure is stable and indestructible and they are easy to bioaccumulate and biomagnify in the way of food chain.Besides,they are carcinogenic,teratogenic,and mutagenic to organism.Moreover,conventional water treatment processes are difficult to remove MPs.Therefore,new water treatment technologies can control the migration,transformation and total amount of organic micro-pollutants and make organic pollutants in the environment reduced and harmless,which also have the qualities of simple,safe,reliable,low-cost,and efficient,need to be developed.In practical application,ultraviolet-based advanced oxidation technology has a good prospect in the removal of organic micro-pollutantsIn this study,a new water treatment system based on the nitrite-contained raw water,namely the UV365/NO2―system,was proposed.The removal efficiency of the UV365/NO2―system to deal with 6 organic micro-pollutants was investigated.The nitrite concentration,MPs structure,raw water quality,p H,DO,etc have been explored to find out the mechanism of UV365/NO2―system degraded and oxidized organic micro-pollutants.Under the conditions of this paper,electron-rich organic micro-pollutants,neutral or alkaline conditions,and water quality conditions with higher dissolved oxygen,the UV365/NO2―system can degrade MPs better.The effect of nitrite concentration on the efficiency of MPs degraded by UV365/NO2―system depends on the structure of MPs.For MPs with strong electron donating ability such as bisphenol A,CBZ and SDZ,with the increase of nitrite concentration,the degradation rate kept increasing,while the MPs with strong electron withdrawing ability such as BPS,ATZ,and NAX,the rate of degradation increased first and then decreased.In addition,taking bisphenol A and carbamazepine as examples,the reaction path of organic micropollutants being degraded and removed in the UV365/NO2―system was proposed.With the aid of liquid chromatography-triple quadrupole mass spectrometry,4 kinds of oxidation products of BPA and 10 kinds of oxidation products of CBZ were detected.Reactive nitrogen species induced nitrification and nitrosation while HO·induced hydroxylation,and they are the main reactions that occur in this system.The concentration of BPA oxidation products increased first and then decreased.Five of the CBZ oxidation products reach their maximum,and the other five kept to increase.Meanwhile,taking bisphenol A as an example,the effect of nitrite on the generation of chlorinated disinfection by-products after the pretreatment of organic micro-pollutants in the UV365system was studied,and the chlorinated disinfection by-products,especially chloronitromethane,were studied.The generation mechanism in this article.The effects of nitrite concentration,p H and UV flux on the yield and toxicity of Disinfection by-products（DBPs）were studied.When the nitrite-containing solution is pretreated by UV365or UV365/chlorine process,two disinfection by-products,chloroform and chloronitromethane（Chloropicrin,TCNM）will be generated after chlorination.Among them,TCNM has strong genotoxicity and cytotoxicity,and the output of TCNM cannot be underestimated.In the presence of nitrite,compared with UV365pretreatment,the yield of TCNM and TCM increased significantly after UV365/chlorine pretreatment.Therefore,when using UV/chlorine with a wavelength of～350 nm to treat BPA-contained water,the test conditions should be controlled to avoid the increase of DBPs cytotoxicity and genotoxicity after pretreatment.In the pretreatment of UV365/chlorine,higher nitrite concentration(0-5mg-N L-1),higher p H value（6.0-7.0）and moderate UV flux contribute to the generation of TCNM in the process of post-chlorination.In the UV365/chlorine pretreatment of bisphenol A,the total cytotoxicity and genotoxicity of its chlorinated DBPs mainly depend on the production of TCNM. |
