| With the widespread use of Disc Tubular Reverse Osmosis(DTRO)process in water treatment,especially in landfill leachate treatment,DTRO membrane concentrates with the complicated matrix and the continuous accumulation of refractory organics became an emerging environmental problem.Therefore,exploring the main components of refractory organics and the evolution of their transformation products and toxicity were critical for harmless disposal of DTRO membrane concentrates.In this study,four common refractory pharmaceuticals,sulpiride,diclofenac,sulfisomidine and sulfamethoxazole were detected in the DTRO membrane concentrate with concentrations ranging from 0.85 to 11.57 ?g/L.These refractory pharmaceuticals showed rapid degradation in ultrapure water which were observed to be fitted by pseudo first order kinetic during UV-Fenton process,with a removal of more than 95% within 4 min.Their degradation pathways were well expounded and some new transformation products were identified.Except diclofenac,the treatment effluents of other pharmaceuticals all showed significant increase in cytotoxicity on HepG2 cell during treatment process and the highest inhibition effect of 55.0% was observed at the sulpiride degradation.With the same initial reaction condition,reaching the same pharmaceutical removal rate of 95%,reaction occurred in DTRO membrane concentrates needed more time with 30 to 60 min which was approximately 7.5 to 15 times longer than reaction occurred in ultrapure water.Radical competition resulted from high concentration of dissolved organic matters might be responsible for the decreasing efficiency.Finally,combined with the cytotoxicity data,peak area evolution of transformation products and quantitative structure activity relationship tool,nine toxicity-causing transformation products were identified.This study would offer some inspirations about harmless disposal of DTRO concentrates and refractory pharmaceuticals detected in aquatic environment. |
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