Effects of typical antibiotics on denitrifying performance in the pyrite/sulfur-based remediation system
In order to evaluate the performance of denitrification process in the pyrite/sulfur-based remediation system(FeS2/S0)under different types of typical antibiotics,sulfonamides(sulfamethoxazole(SMZ)and sulfadiazine(SDZ)),fluoroquinolones(enrofloxacin(ENR)and ofloxacin(OFL)),tetracycline(tetracycline(TCY)and oxytetracycline(OTC)),macrolides(erythromycin(ERY)and spiramycin(SPM))which are usually highly detected in groundwater were taken as typical antibiotics with a set range of concentrations from 100ng/L to 500ug/L.Based on the simulated groundwater microcosm experimental system in this study,the changes in nitrogen,nitrate reductase(NAR),nitrite reductase(NIR)and electron transfer activity(ETSA)during the denitrification in the FeS2/S0 remediation system were investigated.The results show that denitrifying inhibition effect was significantly associated with concentration and species of antibiotic at the order of inhibition degree as:OFL(5.81％～27.73％)＞ENR(3.06％～14.17％),OTC(1.95％～14.25％)＞SMZ(2.54％～11.75％),SDZ(1.87％～10.90％)＞TCY(1.98％～9.44％),SPM(2.45％～9.43％)＞ERY(2.13％～8.47％),and the higher the concentration,the greater the level of inhibition.In all experimental groups,the removal rate of NO2-N was lower than that of NO3-N,the activity of both NAR and NIR increased and then decreased,resulting in a single peak change with the greatest reduction.There was a positive correlation of the removal rate of NO3-N to the concentrations of SO42-S,TFe and Fe2+in effluent.The most significant denitrification inhibition occurred in OFL interrupting groups.Contrasting to the control group,the average value of ETSA in each experimental system(especially in the OFL stressing group)decreased.Meanwhile,the k value in each reaction system of antibiotics did not change much at the ng/L level but varied significantly at the pg/L concentration level,and the k value was significantly lower in the OFL reaction system than in other reaction systems.
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