Degradation Of Pharmaceutical And Antibacterial Agents From Wastewater Induced By Ionizing Irradiation Combined With BAF

Pharmaceutical and personal care products(PPCPs)in natural water bodies are potentially harmful to human and environment,they cannot be effectively removed in conventional wastewater treatment processes,and how to remove them has gained attention from researchers.Ionization irradiation technology is an advanced oxidation process with a broad application prospects.In this paper,trimethoprim,carbamazepine and triclosan were selected as the representative of PPCPs,their degradation characteristics by 60Co-? radiation was investigated,including the influencing factors,the degradation kinetics,the effect of radiation technology incorporating other oxidation process on PPCPs degradation.The possible degradation pathway was proposed and biodegradability improvement of PPCPs after irradiation was evaluated.The main conclusions have been obtained as follows:(1)The main factors influencing the degradation of PPCPs were studied,including the initial concentration of PPCPs,the dosage of other oxidants and the initial pH value of the solution.The results showed that the lower concentration was beneficial to the degradation and mineralization of PPCPs.The addition of persulfate had a significant effect on the degradation of PPCPs.When the concentration of K2S2O8 was 1.5 mM,the mineralization ratio of PPCPs increased from 16%-34% to 32%-94.1% at 1000 Gy absorbed dose.The addition of ferrate inhibited the removal of PPCPs at the initial stage of radiation degradation,and then improved the mineralization ratio to a certain extent.The acidic conditions(pH = 6.5)was favorable to the degradation of PPCPs.(2)The kinetics of irradiation degradation of PPCPs in different irradiation systems was analyzed.The results showed that the degradation of the three PPCPs in different irradiation systems conformed to the pseudo first-order kinetic equation.(3)The degradation pathway and mechanism of each PPCP in different irradiation systems were discussed.The results showed that trimethoprim was degraded and mineralized mainly by hydroxylation,demethylation,cleavage and dehydrogenation.The degradation of carbamazepine was achieved mainly by hydroxylation and cleavage,while hydroxylation,dechlorination and cleavage played an important role in the degradation of triclosan.During the process of PPCPs degradation,HO· played a major role,SO4-· accelerated the degradation by electron transport,while Fe(VI)reacted directly with PPCPs to decompose them.(4)The biodegradability of PPCPs before and after irradiation was investigated by comparing the amount of oxygen consumed by activated sludge.The results showed that each PPCPs could not be used or be toxic to activated sludge before irradiation,and their biodegradability could be improved after irradiation.The removal efficiency of COD,TOC and NH4+-N were significantly increased after combination treatment of irradiation technology and biological aerated filter,before irradiation trimethoprim or triclosan was added in the secondary effluent at the concentration of 1 mg/L.This results provided a theoretical basis and technical support for the combined treatment of waste water containing PPCPs by irradiation technology and biological treatment process.The results provided a theoretical basis and technical support for the combination of irradiation technology and biological aerated filter used in secondary effluent treatment.This study has important theoretical and practical value for the treatment of waste water containing PPCPs by irradiation technology.