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Microbial community response to chlorine conversion in a chloraminated drinking water distribution system
Citation:
Wang, H., C. Proctor, M. Edwards, M. Pryor, J. Santodomingo, H. Ryu, A. Camper, A. Olson, AND A. Pruden. Microbial community response to chlorine conversion in a chloraminated drinking water distribution system. ENVIRONMENTAL SCIENCE & TECHNOLOGY. American Chemical Society, Washington, DC, 48(18):10624-10633, (2014).
Impact/Purpose:
To study the the occurrence of nitrifying bacteria before, during and after a chlorine burn a chloraminated distribution system
Description:
Temporary conversion to chlorine (i.e., “chlorine burn”) is a common approach to controlling nitrification in chloraminated drinking water distribution systems, yet its effectiveness and mode(s) of action are not fully understood. This study characterized occurrence of nitrifying populations before, during and after a chlorine burn at 46 sites in a chloraminated distribution system with varying pipe materials and levels of observed nitrification. Quantitative polymerase chain reaction analysis of gene markers present in nitrifying populations indicated higher frequency of detection of ammonia oxidizing bacteria (AOB) (72% of sites)relative to ammonia oxidizing archaea (AOA) (28% of sites). Nitrospira nitrite oxidizing bacteria (NOB) were detected at 45% of sites, while presence of Nitrobacter NOB could not be confirmed at any of the sites. During the chlorine burn, the numbers of AOA, AOB, and Nitrospira greatly reduced (i.e., 0.8-2.4 log). However, rapid and continued regrowth of AOB and Nitrospira were observed along with nitrite production in the bulk water within four months after the chlorine burn, and nitrification outbreaks appeared to worsen 6-18 months later, even after adopting a twice annual burn program. Although high throughput sequencing of 16S rRNA genes revealed a distinct community shift during the chlorine burn, it steadily returned towards a condition more similar to pre-burn than burn stage. Significant factors associated with nitrifier and microbial community composition included water age and sampling location type, but not pipe material. Overall, these results improve practical understanding of the effect of chlorine burn on nitrifying populations and its long-term effectiveness.
