Mitigation of Antibiotic Resistance Using Ultraviolet Light-Emitting Diodes for Water Treatment

The presence of antibiotic-resistant bacteria (ARB) and antibiotic resistance genes (ARGs) in the environment is a growing issue, which has been exacerbated by the overuse and misuse of antibiotics in health care and agricultural systems. One means of mitigating antibiotic resistance is through drinking water and wastewater treatment, specifically during disinfection processes. Ultraviolet light-emitting diodes (UV-LEDs) are an emerging disinfection technology featuring adjustable peak wavelength emissions. We assessed the use of UV-LED for treating waterborne ARB (Escherichia coli and Aeromonas hydrophila) and ARGs (intracellular and extracellular) compared to conventional low-pressure UV (LP-UV). Overall, less efficient reduction (bacterial inactivation and/or gene degradation) of ARGs was observed compared to the ARB, where the rates of reduction (Chick–Watson coefficients of specific lethality) determined for ARB were typically 2–3 orders of magnitude greater than those for ARG. Furthermore, intracellular ARGs were more difficult to treat than extracellular ARGs, possibly because of the protective cellular structures that encompass intracellular ARGs and/or cellular repair mechanisms. Differences in ARB/ARG absorbance at different UV wavelengths and the UV lamp output efficiency led to different relative efficiencies among the four different wavelengths tested. The electrical energy per order for the different wavelengths was generally best for LP-UV (<3.25 kWh/m3), followed by 265 and 285 nm (<≈130 kWh/m3), and 255 nm (<≈150 kWh/m3). Overall, UV-LEDs can successfully treat water/wastewater contaminated with ARB and ARGs; however, for UV-LEDs to become more competitive with LP-UV systems, improvements in energy efficiency are necessary.