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Seven antibiotics including norfloxacin (NOR) were tested via disk susceptibility test on E. coliculture isolated from the MLSS of the two types of lab-scale sequencing batch reactors (SBR), acommon SBR and an SBR with rnicrofiltration membrane (SB-MBR) for treatment of syntheticmunicipal wastewater. The same experiment treating the NOR-added wastewater to examine thepossible induction of resistance to itself and the other antibiotics. The MLSS from Banglculture (TISTR780) were spiked daily into both reactors. The reactors were continuously operatedunder 2hr/2hr of aeration/non-aeration cycle and resistances to antibiotics of E. coli in MLSS weremonitored. When NOR was not added, the SB-MBR showed lower percentages of resistant E. colithan the SBR did to amoxicillin/clavulanic acid, amikacin, nalidixic acid, tetracycline andchloramphenicol. Oppositely, the SB-MBR treating the NOR-added wastewater appeared topromote resistances of E. coli to nalidixic acid, sulfamethoxasole and tetracycline probably due to along SRT and low DO compared to that of SBR. Although its mechanism should be analyzed withmolecular techniques in further studies, this NOR-induced expression of resistance resulted in ahigher occurrence of multidrug resistant E. coli in the SB-MBR than that in the SBR. |
