Antibiotic Concentrations and the Composition of Bacterial Communities in Municipal Wastewater and Reclaimed Water
Sapkota, Amy R
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Before reclaimed water is used more widely within the current United States (U.S.) wastewater treatment infrastructure, it is important to examine the potential public health impacts of this emerging, alternative freshwater resource. My dissertation evaluated antibiotic concentrations and the composition of bacterial communities in conventionally treated municipal wastewater and resulting reclaimed water. I also evaluated the efficacy of a point-of-use filtration system in reducing antimicrobials present in reclaimed water. My objectives were to: 1) Assess the fate of antibiotics and; 2) Characterize the total bacterial community structure of differentially treated wastewater, and reclaimed water that has undergone on-site treatment and storage; and 3) Evaluate zero-valent iron (ZVI)-biosand filtration as a potential point-of use treatment technology for the reduction of antimicrobials from conventionally treated reclaimed water. I extracted nine antibiotics and total genomic deoxyribonucleic acid (DNA) from differentially treated wastewater and reclaimed water samples from two Mid-Atlantic and two Midwest WWTPs, and one associated Mid-Atlantic spray irrigation site. I quantified the presence of antibiotics using high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS), and characterized total bacterial community structure using 16S rRNA gene sequencing. I also used HPLC-MS/MS to quantify the reduction of thirteen antimicrobials from conventionally treated reclaimed water after ZVI-biosand filtration. Statistical analyses included the Kruskal Wallis test, paired Wilcoxon signed-rank test, and differential abundance using normalization achieved by cumulative sum scaling. Activated sludge treatment used at all four WWTPs resulted in the reduction of some antibiotics and the increase of genera containing potentially pathogenic bacteria (Mycobacterium and Legionella). Treatment plant chlorination and spray irrigation site ultraviolet radiation (UV) treatment and open-air storage reduced the concentration of azithromycin and increased the relative abundance of Mycobacterium. ZVI-biosand filtration achieved significant reductions in azithromycin, ciprofloxacin, erythromycin, linezolid, oxolinic acid, pipemidic acid, penicillin and vancomycin. This research provided additional scientific evidence that activated sludge treatment and chlorination alone may not be sufficient for the removal of antimicrobials and potentially pathogenic bacteria from municipal wastewater and resulting reclaimed water. However, ZVI-biosand filtration may be an efficient reuse site technology for the reduction of antimicrobials from conventionally treated reclaimed water.