Study On Advanced Treatment Of Municipal Wastewater By Ultraviolet-fenton-like Advanced Oxidation Technology

In recent years,ultraviolet-Fenton-like advanced oxidation technology based on free radicals has attracted wide attention,which can effectively remove refractory organic pollutants in sewage.Effluent Organic Matter(EfOM)is the most important component of refractory dissolved organic substances remaining after primary and secondary biochemical treatment in municipal sewage treatment plants,and also the main limiting factor affecting secondary effluent discharge.Therefore,four different oxidants were activated by ultraviolet light to carry out treatment of EfOM,and the optimal reaction parameters and reaction mechanism for the removal of refractory micro-organic matters and new pollutants by this process were studied,which provided theoretical basis and technical support for the practical municipal wastewater treatment technology.At the same time,different spectral characterization methods are used in this paper to further explore the organic composition in EfOM.First,benzoic acid(BA),p-chlorobenzoic acid(p-CBA)and 1,4-dimethoxybenzene(DMOB)were used as targeted pollutants to construct a Fenton-like advanced oxidation technology using four typical oxidants(PS,PMS,H2O2,NaCIO)and ultraviolet(UV)combined to treat refractory organics in EfOM.According to the previous literature research,the oxidant concentration of 0.588 mM was used for the degradation,which proved that the four oxidants had the degradation effect on the model pollutant.After changing the oxidant concentration gradient,the best degradation effect was finally determined when the oxidant concentration was 2.352 mM,pH was 7.90 and optical power density was 1.217 mW/cm2.In addition,the pollutants in the UV/oxidant degradation model conform to the pseudo-first-order reaction kinetics,so the method of competitive kinetics can be used to determine the most active substances in the UV/oxidant system.It is proved that the free radicals(HO·,SO4-·,ClO·)are the main active substances in the oxidation system.The second order reaction rate constants of each active radical and EfOM were determined as(5.027±0.643)×102(SO4-·),(3.192±0.153)×104(HO·)and 1.35×106(ClO·)(mg-C/L)-1s-1.In addition,the concept of Rct was introduced to evaluate the role of each active radical in system,so as to understand its reaction mechanism more intuitively.Finally,the structure and properties of organic compounds were characterized by various spectroscopy methods.The characterization results showed that EfOM was mainly composed of protein-like,fulvic acid-like(FA-like)and humic acid-like(HA-like)organic substances.The preferential order of oxidation was FA-like>HA-like>protein-like.The order of degradation performance was HA-like>protein-like>FA-like.