Occurrences And Distributions Of Several Cephalosporin Antibiotics In Wastewater Treatment Process And Investigation Of Their Environmental Behaviors

Pharmaceuticals and personal care products (PPCPs) issue is the hot topic in environmental research. Drugs in water environment have been globally concerned. Incompletely absorbed or improperly disposed pharmaceuticals could find their way into municipal sewage or hospital wastewater in their original structure or metabolites after being taken by human beings and animals. The"pseudo-persistent"pollution of drugs in water body could occur and render adverse effects on ecosystem and human health, as the removal efficiencies of them in wastewater treatment plants (WWTPs) are unsatisfactory nowadays. Firstly, this study developed a conceptional frame, which based on predicted environmental concentration, persistent and toxicity, to identify the"priority control pharmaceuticals"in the aquatic environment. Shanghai was selected to validate the model. Environmental risks of seven groups of drugs (totally 47) were assessed according to the screening scheme developed in this study. Five cephorasporins antibiotics (belonging toβ-lactam antibiotics), i.e. Ceftazidime (CAZ), Cefradine (CED), Cefaclor (CCR), Cefotaxime (CTX) and Cefoperazone (CPZ) were then chosen as the analytes in this study.A method to simultaneously determine the five cephalosporin antibiotics in the environmental samples (including different water and sludge samples) using solid phase extraction and high performance liquid chromatography with ultraviolet detector (SPE-HPLC-UVD) was developed. The recoveries of the analytes were satisfactory in all types of water samples. Method detection limits were found from 26.14 to 59.44ng/L. In addition, the method was applied to investigate the occurrences, distributions, behaviors and removals of the analytes in two local WWTPs (MH-WWTP and XZ-WWTP). The results showed that all the five cephalosporin antibiotics were determined in the influent, elementary sinking and effluent water samples, with the level of ng/L-μg/L. Moreover, the analyte concentrations in samples collected in July were relatively lower than those in samples collected in other seasons. This might be due to the usage fluctuation of cephalosporin antibiotics and the enhanced degradation by high temperature. It is indicated that higher removal efficiencies of cephalosporin antibiotics were obtained in the treatment process of oxidation ditch rather than that of A2/O. According to the daily mass flow of five cephalosporin antibiotics in effluent samples, it was noted that different cephalosporin antibiotics had different discharge load in varied seasons and may potentially pose dissimilar ecological and environmental risks on the receiving water.Additionally, studies on the hydrolysis, biodegradation, photolysis and adsorption of cephalosporin antibiotics in the aquatic environment were carried out. The degradation kinetic processes could be described by the First-order kinetic equations. The half-lives were 1.83, 3.73, 0.70 and 1.07d at 50℃for CAZ, CED, CTX and CPZ, respectively. It was found that hydrolysis was one of the main degradation ways of cephalosporin antibiotics. Increasing temperature or pH could accelerate their hydrolysis rates indicating that wastewater containing cephalosporin antibiotics could be treated by heating or alkalifying. In addition, the higher hydrolysis rates of cephalosporin antibiotics were observed in influents and effluents of WWTP rather than those in other types of water samples. Neither sterilization nor photolysis had significant effects on the degradations of cephalosporin antibiotics. HPLC analysis of hydrolysis products of cephalosporin antibiotics in ultralpure water, which was stored for 10d at 25℃, indicated that the main hydrolysis product was their parent substance, 7-aminocephalosporanic acid (7-ACA). It was found from the sludge adsorption study that the adsorption equilibrium time was 4h. In addition, adsorption could be described with Freundlich and Langmuir isotherms. Since adsorption constants (Kds) were all below 0.005, it was proved that the adsorptions of cephalosporin antibiotics on sludge were poor. Organic adsorption constants (Kocs) were all below 0.02, which indicated that the mobility of cephalosporin antibiotics in sludge was weak. All variation values of Gibbs free energy were below 20kJ/mol, which indicated that physical adsorption might occur with hydrophobic bond force as the main adsorption force.According to the activated sludge respiration inhibition tests, CAZ, CED, CCR, CTX and CPZ with the concentration of 0-40.0mg/L in the activated sludge could either inhibit or accelerate the respiration of organisms. The reasons might be that cephalosporin antibiotics could inhibit the activity of microbes; on the other hand, they could also accelerate the respiration of microbes as carbon source and nitrogen source. Besides, microbial communities in the activated sludge are very complicated and have varied drug-resistant.In sum, the occurrences of cephalosporin antibiotics in the aquatic environment further confirmed the bulk production and unreasonable usage of them in China. Effects of cephalosporin antibiotics as well as their degradation products on the aquatic ecosystem are not clear nowadays. Their"pseudo-persistent"pollutions in the aquatic environment should not be ignored. The study has great originality as the relevant reports are very scarce in a global scale. This study provides the important scientific references for administrative authority to establish the control strategy in terns of the protection of ecosystem and human health.