Abstract
Abstract Given the availability of technological solutions and guidelines for safe drinking water, direct potable reuse of reclaimed water has become a promising option to overcome severe lack of potable water in arid regions. However, the growing awareness of the presence of antibiotic-resistant bacteria (ARB) and antibiotic resistance genes (ARG) in corresponding raw wastes has led to new safety concerns. This study investigated the fate of ARB and intracellular and extracellular ARG after each treatment step of an advanced water treatment facility in Windhoek, Namibia. The New Goreangab Water Reclamation Plant (NGWRP) produces drinking water from domestic secondary wastewater treatment plant effluent and directly provides for roughly a quarter of Windhoek's potable water demand. Procedures to study resistance determinants were based on both molecular biology and culture-based microbiological methods. TaqMan real-time PCR was employed to detect and quantify intracellular resistance genes sul1, ermB, vanA, nptII and nptIII as well as extracellular resistance gene sul1. The NGWRP reduced the amount of both culturable bacterial indicators as well as the resistance genes to levels below the limit of detection in the final product. The main ozonation and the ultrafiltration had the highest removal efficiencies on both resistance determinants.
Highlights
Population growth in various countries of the world together with the effects of climate change leads to a continuous increase of pressure on the availability of water resources for irrigation of agricultural crops and potable water (USEPA )
The increasing use of antibiotics brings along the increased occurrence of antibiotic resistance (AR) which is the ability of bacteria to withstand the antibiotic and compensate its effect (Davison et al )
In terms of water quality regarding AR, the results propose that controlled aquifer recharge with the final product of New Goreangab Water Reclamation Plant (NGWRP) is unlikely to cause a detectable increase in the abundance of antibiotic-resistant bacteria (ARB) and antibiotic resistance genes (ARG) in the aquifer water and could be considered safe
Summary
Population growth in various countries of the world together with the effects of climate change leads to a continuous increase of pressure on the availability of water resources for irrigation of agricultural crops and potable water (USEPA ). Current quality guidelines include an extensive list of microbial indicators, requirements for organic matter and suspended particles and physicochemical parameters (Lahnsteiner Du Pisani & Menge ; Water Reuse Research Foundation ; Hong et al ). Beside these conventional parameters, organic trace chemical constituents that have survived treatment are currently under close investigation by scientists and advisory boards regarding their significance for human health. One group of these trace constituents are pharmaceuticals and their metabolites, amongst which belong the antibiotics (Dulio et al ). AR is listed amongst the top ten global health threats (World Health Organization )
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