Factors affecting the formation of DBPs by chlorine disinfection in water distribution system

Relation between AOC concentration and bacterium regrowth in drinking water network was investigated to obtain biostability criteria. Comparably obvious linear relationship was found between the maximum HPC and the maximum content of AOC of the distribution system. By extrapolation of the line，HPC would decline to 0 when AOC was 57µg/L. That result showed that substrates cannot support bacterium growth when AOC was less than 57µg/L. Similar obvious linear relationship was also derived between the maximum AOC content and the maximum AOC consumption (∆AOC) of the distribution system. AOC consumption (∆AOC) would decline to 0 when AOC content was 43.8µg/L. it also showed that bacteria cannot growth and AOC do not be utilized when AOC was less than 43.8µg/L. Some researchers had proposed biostability criterias, i.e. Van der Kooij’s criteria of 10µg/L and LeChevallier’s criteria of 50～100µg/L. We proposed that the biostability criteria under chlorine disinfection was AOC <40µg/L.

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Chlorine Disinfection of Atypical Mycobacteria Isolated from a Water Distribution System

Applied and Environmental Microbiology ◽

10.1128/aem.68.3.1025-1032.2002 ◽

2002 ◽

Vol 68 (3) ◽

pp. 1025-1032 ◽

Cited By ~ 129

Author(s):

Corinne Le Dantec ◽

Jean-Pierre Duguet ◽

Antoine Montiel ◽

Nadine Dumoutier ◽

Sylvie Dubrou ◽

...

Keyword(s):

Distribution System ◽

Contact Time ◽

Water Distribution ◽

Arrhenius Equation ◽

Water Distribution System ◽

Mycobacterium Fortuitum ◽

Nutrient Media ◽

Medium Ph ◽

Chlorine Disinfection ◽

Different Temperatures

ABSTRACT We studied the resistance of various mycobacteria isolated from a water distribution system to chlorine. Chlorine disinfection efficiency is expressed as the coefficient of lethality (liters per minute per milligram) as follows: Mycobacterium fortuitum (0.02) > M. chelonae (0.03) > M. gordonae (0.09) > M. aurum (0.19). For a C · t value (product of the disinfectant concentration and contact time) of 60 mg · min · liter−1, frequently used in water treatment lines, chlorine disinfection inactivates over 4 log units of M. gordonae and 1.5 log units of M. fortuitum or M. chelonae. C · t values determined under similar conditions show that even the most susceptible species, M. aurum and M. gordonae, are 100 and 330 times more resistant to chlorine than Escherichia coli. We also investigated the effects of different parameters (medium, pH, and temperature) on chlorine disinfection in a chlorine-resistant M. gordonae model. Our experimental results follow the Arrhenius equation, allowing the inactivation rate to be predicted at different temperatures. Our results show that M. gordonae is more resistant to chlorine in low-nutrient media, such as those encountered in water, and that an increase in temperature (from 4°C to 25°C) and a decrease in pH result in better inactivation.

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Chlorination contributes to multi-antibiotic resistance in a pilot-scale water distribution system

Water Science & Technology Water Supply ◽

10.2166/ws.2021.185 ◽

2021 ◽

Author(s):

Jinmei Li ◽

Shuting Zhang ◽

Lizheng Guo ◽

Lihua Chen ◽

Zhisheng Yu

Keyword(s):

Antibiotic Resistance ◽

Distribution System ◽

Water Distribution ◽

Water Distribution System ◽

Water System ◽

Antibiotic Resistance Genes ◽

Pilot Scale ◽

Free Chlorine ◽

Chlorine Disinfection ◽

Community Shift

Abstract The generation and dissemination of antibiotic resistance bacteria (ARB) and antibiotic resistance genes (ARGs) in the environment has become a critical risk to human health. This study is based on a pilot-scale simulated water distribution system to understand the effects of chlorine disinfection treatment (without free chlorine) on ARB and ARGs in biofilms. The hydraulic parameters and pipe materials of the system were simulated based on a drinking water system. The results of the colony counts showed that bacterial multi-antibiotic resistance could be enhanced 13-fold in the biofilms of pipeline. The use of high-throughput qPCR (HT-qPCR) indicated that the total relative abundance of ARGs in biofilm samples increased significantly (p < 0.05), while the diversity of bacteria was shown to be reduced via taxonomic analysis of the V3–V4 region of 16S rRNA. The prominent types of ARGs were conferred resistance by aminoglycoside and β-lactam after the chlorine disinfection treatment, and antibiotic deactivation was the main mechanism. Phyla Proteobacteria had the highest abundance in both treatment and control groups but decreased from 70.81% (initial biofilm sample) to 26.09% (the 6th month biofilm sample) in the treatment groups. The results show that the chlorine disinfection plays a role in the risk of development of bacteria antibiotic resistance in pipe networks owing to bacteria in biofilms. This study was the first to investigate the contribution of chlorination without free chlorine to the bacterial community shift and resistome alteration in biofilms at a pilot test level.

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