The removal of trace levels of antibiotics from anthropogenic wastewaters is essential to prevent the proliferation and emergence of resistant bacteria such as MRSA and ND-1. Unfortunately, standard primary and secondary wastewater treatments sometimes cannot achieve the desired quantitative removal of these pharmaceuticals. Therefore, Advanced Oxidation Processes (AOPs) for water treatment have been suggested as an appropriate final polishing step for the removal of these contaminants. These processes rely upon the generation of highly oxidizing species such as the hydroxyl (·OH) and sulfate (SO4-·) radicals, where these radicals quickly react with chemical contaminants to oxidatively destroy them. A large library of absolute rate constants for both the hydroxyl and sulfate radical reaction with various classes of antibiotics has now been reported. Mechanistic insight into these radical reactions has been inferred from the kinetic data. Many hydroxyl radical oxidations result in phenolic derivatives - but these species may still have antibiotic behavior! The different reaction mechanism of the sulfate radical of electron abstraction from electron-rich atoms has shown that it may be more efficient in ultimately destroying these particular antibiotics. To establish the cost-effectiveness of using AOPs for this purpose, here we have established the effectiveness of the hydroxyl radical in quantitatively destroying multiple different classes of antibiotics. Antibiotic solutions were subjected to varying levels of hydroxyl radical oxidation at their minimum inhibitory concentration using a steady state 60Co irradiator. The remaining antibiotic activity of the irradiated solutions was then established using model (mainly S. auras) bacterial systems. This allowed us to quantitatively measure bacterial growth inhibition, from which values for the equivalent number of hydroxyl radical reactions required to quantitatively destroy these antibiotics in water to be absolutely determined. Data was obtained for different contaminant-level conditions, with carbonate and dissolved organic matter impacts specifically elucidated.

Recycling wastewater:  Quantitative removal of antibiotic activity in waters using advanced oxidation processes

249th National Meeting (2015)

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