The Influence of Nitrifying Bacteria on Monochloramine Decay and Opportunistic Premise Plumbing Pathogen Growth
Drinking water infrastructure in homes and buildings provides a niche for water microbiomes. Higher surface area to volume ratios, stagnation, and disinfectant decay at point-of-use locations lead to microbial regrowth and a higher risk of exposure to opportunistic premise plumbing pathogens (OPPPs). Nitrifying bacteria are common inhabitants of drinking water systems and are known to contribute to the decay of disinfectant residuals, potentially leading to additional OPPPs growth. To examine the influence of nitrifying bacteria on monochloramine decay and opportunistic pathogen growth, simulated glass water heaters with and without the presence of nitrifying bacteria will be assembled. The microbial and chemical composition within the simulated glass water heaters set to different temperatures will be analyzed along the nitrifying bacteria’s optimal growth curve. High throughput Illumina sequencing of 16S rRNA amplicons, quantitative polymerase chain reaction, LegioLert Assays, and total cell count will be utilized to identify and quantify nitrifying bacteria and OPPPs, as modeled by Legionella pneumophila. Total chlorine, free chlorine, free ammonia, and monochloramine concentrations will all be determined using a HACH spectrophotometer. With these methods, the microbial and chemical composition of the simulated glass water heaters will be elucidated at different temperatures along the nitrifying bacteria’s optimal growth curve to gain insight into the relative influence of the bacteria on the rate of monochloramine decay and opportunistic pathogen growth. Future studies focusing on the relative growth and inactivation of nitrite-oxidizing and ammonia-oxidizing bacteria in water infrastructure would help utilities control opportunistic pathogen regrowth in the distribution system and limit pathogen exposure at point-of-use locations.
Author Bio
Darel Snead is currently attending Virginia Tech pursuing majors in Microbiology and Medicinal Chemistry. As a sophomore, he works in Dr. Marc Edwards’ lab which focuses on research into water treatment, aquatic chemistry, and chemical corrosion. Previously, he has worked on projects identifying copper concentrations that encourage opportunistic pathogen growth in water systems. Most recently, after receiving the Roop and Kavita Mahajan Research Grant, he has shifted gears into studying the effects of nitrification on disinfectant decay and opportunistic pathogen regrowth in water systems at on-site locations. During the summers, he works with the National Institute of Health to characterize novel functional elements using high throughput Illumina sequencing and study the functions of Legionella pneumophila effector proteins.
