Q-303. Influences of Erythromycin and Erythromycin-H2O on Aerobic Sequencing Batch Reactor (SBR)

C. Fan, J. He;
Natl. Univ. of Singapore, Singapore, SINGAPORE.

One of the most popular antibiotics, erythromycin (ERY) and its derivative erythromycin-H2O (ERY-H2O) are detected at 0.1~200μg/l levels in most water or wastewater surveyed. However, many studies conducted on the effects of ERY on pure or mixed cultures are in the mg/l range (1~200mg/L). Hence, in this study, we investigated whether ERY or ERY-H2O in the μg/l range had inhibitory effect on aerobic SBR. Three SBRs were inoculated with same activated sludge from domestic WWTPs, fed with the same synthetic wastewater and controlled by Programmable Logic Controller (PLC) in a same 8-hour cycle. The three SBRs were then given ERY-H2O 50ug/l (R1), ERY 100μg/l (R2) and no antibiotics (R3) respectively. During a 2-month monitoring of daily effluent, no inhibition to carbon and nitrogen removal was observed in R1 and R2 compared with R3. Also, ERY showed minimal influence on the recovery of carbon and nitrogen removal from super-high COD (24000 mg/L) shock in R2. However, 13-month later, batch experiments of gradually increasing the dosage of ERY or ERY-H2O from 100 to 800μg/l, showed that ERY (100~800μg/l) slowed down ammonium oxidation (20~70% at the 24th hr) and nitrite oxidation (20~40% at the 40th hr) although no inhibition of ERY-H2O was observed. Most importantly, by extending reaction time, ERY inhibition was recovered identically in batch bottle samples with inocula from three SBRs sludge and ERY was biotransformed to other products than ERY-H2O in all above experiments. Therefore, extended reaction and ERY transformation may take account for no inhibition of ERY in first 2-month. For the microbiology community, the T-RFLP profiles of 8-month SBR sludge revealed the existence of four main microorganisms (base pair 120, 240, 320, 470), although their relative abundance in R1 was different from R2 or R3, which echoed recoverability of ERY inhibition. In conclusion, recoverable influence of ERY on SBRs was due to extended reaction and ERY biotransformation to other products which do not show antibiotic functions. ERY-H2O had no inhibition. This study clarifies potential influence of ERY on WWTPs, a public concern, exists but recoverable under certain conditions.