Establishing minimum free chlorine residual concentration for microbial control in a municipal drinking water distribution system

Distribution system data from a Nova Scotia municipal drinking water supply was collected over four years, including free chlorine residual concentration, heterotrophic plate count (HPC) bacteria, and temperature. These data were analyzed for occurrences of HPC bacteria greater than 500 colony forming units (CFU)/mL. The municipality was interested in determining if secondary chlorination practices were sufficient in maintaining microbial health in their distribution system. Coliform data were non-detect (total coliforms and Escherichia coli) in the distribution system over this period and thus heterotrophic bacteria were used to assess microbial health. Results were compared to similar data collected from pilot-scale studies that had been carried out using the same municipal water as the source. Analysis showed that a similar trend was observed between pilot- and full-scale samples. Full-scale data analysis revealed that the minimum disinfection requirement of 0.2 mg/L did not consistently control occurrences of heterotrophic bacteria from being greater than 500 CFU/mL. By comparison, maintaining a concentration of 0.3 mg/L or above, particularly in warm-weather systems, maintained the number of heterotrophic bacteria at below 500 CFU/mL. Fortunately the majority of samples collected in the full-scale distribution system (>89%) had a free chlorine residual concentration of greater than 0.30 mg/L. While it is recognized that this system had 100% compliance for E. coli, the goal of this work will help utilities understand how to utilize microbial data to inform operational disinfection targets for their distribution system.

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Phylogenetic assessment of heterotrophic bacteria from a water distribution system using 16S rDNA sequencing

Canadian Journal of Microbiology ◽

10.1139/w05-007 ◽

2005 ◽

Vol 51 (4) ◽

pp. 325-335 ◽

Cited By ~ 37

Author(s):

Sima T Tokajian ◽

Fuad A Hashwa ◽

Ian C Hancock ◽

Pierre A Zalloua

Keyword(s):

Drinking Water ◽

16S Rdna ◽

Water Samples ◽

Distribution System ◽

Water Distribution ◽

Heterotrophic Bacteria ◽

Diagnostic Methods ◽

Plate Count ◽

Rdna Sequencing ◽

Drinking Water Samples

Determination of a heterotrophic plate count (HPC) for drinking-water samples alone is not enough to assess possible health hazards associated with sudden changes in the bacterial count. Speciation is very crucial to determine whether the population includes pathogens and (or) opportunistic pathogens. Most of the isolates recovered from drinking water samples could not be allocated to a specific phylogenetic branch based on the use of conventional diagnostic methods. The present study had to use phylogenetic analysis, which was simplified by determining and using the first 500-bp sequence of the 16S rDNA, to successfully identify the type and species of bacteria found in the samples. Gram-positive bacteria α-, β-, and γ-Proteobacteria were found to be the major groups representing the heterotrophic bacteria in drinking water. The study also revealed that the presence of sphingomonads in drinking water supplies may be much more common than has been reported so far and thus further studies are merited. The intermittent mode of supply, mainly characterized by water stagnation and flow interruption associated possibly with biofilm detachment, raised the possibility that the studied bacterial populations in such systems represented organisms coming from 2 different niches, the biofilm and the water column.Key words: intermittent water supply, 16S rDNA, biofilm, water column.

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Persistence and Decontamination of Bacillus atrophaeus subsp. globigii Spores on Corroded Iron in a Model Drinking Water System

Applied and Environmental Microbiology ◽

10.1128/aem.02899-06 ◽

2007 ◽

Vol 73 (8) ◽

pp. 2451-2457 ◽

Cited By ~ 38

Author(s):

Jeffrey G. Szabo ◽

Eugene W. Rice ◽

Paul L. Bishop

Keyword(s):

Drinking Water ◽

Distribution System ◽

Water System ◽

Bulk Water ◽

Free Chlorine ◽

Iron Surface ◽

Bacillus Atrophaeus ◽

Chlorine Residual ◽

Typical Distribution ◽

Hydraulic Shear

ABSTRACT Persistence of Bacillus atrophaeus subsp. globigii spores on corroded iron coupons in drinking water was studied using a biofilm annular reactor. Spores were inoculated at 106 CFU/ml in the dechlorinated reactor bulk water. The dechlorination allowed for observation of the effects of hydraulic shear and biofilm sloughing on persistence. Approximately 50% of the spores initially adhered to the corroded iron surface were not detected after 1 month. Addition of a stable 10 mg/liter free chlorine residual after 1 month led to a 2-log10 reduction of adhered B. atrophaeus subsp. globigii, but levels on the coupons quickly stabilized thereafter. Increasing the free chlorine concentration to 25 or 70 mg/liter had no additional effect on inactivation. B. atrophaeus subsp. globigii spores injected in the presence of a typical distribution system chlorine residual (∼0.75 mg/liter) resulted in a steady reduction of adhered B. atrophaeus subsp. globigii over 1 month, but levels on the coupons eventually stabilized. Adding elevated chlorine levels (10, 25, and 70 mg/liter) after 1 month had no effect on the rate of inactivation. Decontamination with elevated free chlorine levels immediately after spore injection resulted in a 3-log10 reduction within 2 weeks, but the rate of inactivation leveled off afterward. This indicates that free chlorine did not reach portions of the corroded iron surface where B. atrophaeus subsp. globigii spores had adhered. B. atrophaeus subsp. globigii spores are capable of persisting for an extended time in the presence of high levels of free chlorine.

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Biofilm bacterial communities and abundance in a full-scale drinking water distribution system in Shanghai

Journal of Water and Health ◽

10.2166/wh.2010.048 ◽

2010 ◽

Vol 8 (3) ◽

pp. 593-600 ◽

Cited By ~ 6

Author(s):

Xiaohui Bai ◽

Fan Wu ◽

Binhui Zhou ◽

Xinghua Zhi

Keyword(s):

Drinking Water ◽

Distribution System ◽

Bacterial Communities ◽

Water Distribution ◽

Water Distribution System ◽

Full Scale ◽

Community Diversity ◽

Plate Count ◽

Drinking Water Distribution System ◽

Drinking Water Distribution

Community diversity and abundance of biofilms from a full-scale drinking water distribution system in Shanghai were characterized by denaturing gradient gel electrophoresis (DGGE) analysis of 16S rRNA sequences and heterotrophic plate count (HPC), respectively. Bacteria affiliated to the Beta- and Gamma-Proteobacteria were dominating in both in-situ and HPC-culturable bacterial communities. Other bacteria present included members of Alphaproteobacteria, Bacteroides, Actinobacteria, Nitrospirae and Firmicutes. Acidovorax, Ralstonia and Acinetobacter were common species in biofilms. Klebsiella pneumoniae and Enterobacter sp. were detected in the local distribution system. Dissolved organic carbon (DOC), residual disinfectant and temperature were the most important factors influencing both bacterial abundance and composition. HPC for biofilm sample was not correlated with its community diversity.

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Association between over-chlorinated drinking water and suckling, nursery and fattening pig death losses

Veterinární Medicína ◽

10.17221/1585-vetmed ◽

2011 ◽

Vol 56 (No. 7) ◽

pp. 358-361

Author(s):

A. Tofant ◽

M. Ostovic ◽

S. Wolf ◽

A. Ekert Kabalin ◽

Z. Pavicic ◽

...

Keyword(s):

Adverse Effect ◽

Drinking Water ◽

Data Analysis ◽

Free Chlorine ◽

Residual Concentration ◽

Pig Production ◽

Chlorine Residual ◽

Chlorinated Drinking Water ◽

The Impact ◽

Fattening Pigs

Following our report on reproductive failure in gilts and sows caused by drinking over-chlorinated water at a pig-breeding farm, the present study investigated the impact of water over-chlorination on the different pig production categories on the farm. Pigs were given over-chlorinated water with a free chlorine residual concentration of 2.11 mg/l for seven days, from the onset of mechanical failure of the chlorinator dispenser connected to the water supplying system until its detection. Data analysis revealed that the adverse effect of over-chlorinated drinking water manifested as an increase in the percentage of death losses in suckling, nursery and fattening pigs (all P < 0.01).

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Effect of chloramine residual on iron release in drinking water distribution systems

Water Science & Technology Water Supply ◽

10.2166/ws.2009.476 ◽

2009 ◽

Vol 9 (4) ◽

pp. 349-355 ◽

Cited By ~ 3

Author(s):

Y. Wang ◽

X. J. Zhang ◽

Z. B. Niu ◽

C. Chen ◽

P. P. Lu ◽

...

Keyword(s):

Drinking Water ◽

Cast Iron ◽

Distribution System ◽

Distribution Systems ◽

Water Distribution ◽

Iron Release ◽

Residual Concentration ◽

Drinking Water Distribution Systems ◽

Chlorine Residual ◽

Drinking Water Distribution

Iron release from scale brought about serious problems such as noticeable increases in turbidity and colour of the water in distribution system and taps. Field study and bench scale experiment on iron release from corrosion scale were carried out. In old cast iron pipe, higher iron release occurred with lower chlorine residual concentration, while lower iron release occurred with higher chlorine residual concentration. The reason lay in the structure of scale and the electro-chemical reactions occurring on the scale and in the bulk. The passivated-out-layer of scale was formed by ferric oxide. It could be broken down by reductive reaction in an atmosphere of low chlorine residual concentration. In contrast, the situation was quite different with new cast iron pipe, the age of which was only half a year. Iron release was considered as the product of the iron matrix and chlorine since the passivated-out-layer of scale had not formed yet. This iron release was consistent with chlorine residual concentration. It is suggested that maintaining a high chlorine residual concentration in a drinking water distribution system is beneficial to controlling both microorganism' regrowth and iron release.

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Sensory aspects of drinking water in contact with epoxy lined copper pipe

Water Science & Technology ◽

10.2166/wst.2007.175 ◽

2007 ◽

Vol 55 (5) ◽

pp. 161-168 ◽

Cited By ~ 14

Author(s):

T.H. Heim ◽

A.M. Dietrich

Keyword(s):

Water Quality ◽

Drinking Water ◽

Organic Compounds ◽

Sensory Analysis ◽

Water Samples ◽

Distribution System ◽

Distribution Systems ◽

Free Chlorine ◽

Copper Pipe

Pipe relining via in situ epoxy lining is used to remediate corroded plumbing or distribution systems. This investigation examined the effects on odour, TOC, THM formation and disinfectant demand in water exposed to epoxy-lined copper pipes used for home plumbing. The study was conducted in accordance with the Utility Quick Test, a migration/leaching method for utilities to conduct sensory analysis of materials in contact with drinking water. The test was performed using water with no disinfectant and levels of chlorine and monochloramines representative of those found in the distribution system. Panelists repeatedly and consistently described a “plastic/adhesive/putty” odour in the water from the pipes. The odour intensity remained relatively constant for each of two subsequent flushes. Water samples stored in the epoxy-lined pipes showed a significant increase in the leaching of organic compounds (as TOC), and this TOC was demonstrated to react with free chlorine to form trichloromethane. Water stored in the pipes also showed a marked increase in disinfectant demand relative to the water stored in glass control flasks. A study conducted at a full scale installation at an apartment demonstrated that after installation and regular use, the epoxy lining did not yield detectable differences in water quality.

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First Derivative UV Spectra of Surface Water as a Monitor of Chlorination in Drinking Water Treatment

The Scientific World JOURNAL ◽

10.1100/tsw.2001.13 ◽

2001 ◽

Vol 1 ◽

pp. 39-43 ◽

Cited By ~ 2

Author(s):

V. Zitko

Keyword(s):

Drinking Water ◽

Water Treatment ◽

Surface Water ◽

Distribution System ◽

Drinking Water Treatment ◽

Uv Spectra ◽

Free Chlorine ◽

Residual Chlorine ◽

First Derivative ◽

Derivative Spectra

Many countries require the presence of free chlorine at about 0.1 mg/l in their drinking water supplies. For various reasons, such as cast-iron pipes or long residence times in the distribution system, free chlorine may decrease below detection limits. In such cases it is important to know whether or not the water was chlorinated or if nonchlorinated water entered the system by accident. Changes in UV spectra of natural organic matter in lakewater were used to assess qualitatively the degree of chlorination in the treatment to produce drinking water. The changes were more obvious in the first derivative spectra. In lakewater, the derivative spectra have a maximum at about 280 nm. This maximum shifts to longer wavelengths by up to 10 nm, decreases, and eventually disappears with an increasing dose of chlorine. The water treatment system was monitored by this technique for over 1 year and changes in the UV spectra of water samples were compared with experimental samples treated with known amounts of chlorine. The changes of the UV spectra with the concentration of added chlorine are presented. On several occasions, water, which received very little or no chlorination, may have entered the drinking water system. The results show that first derivative spectra are potentially a tool to determine, in the absence of residual chlorine, whether or not surface water was chlorinated during the treatment to produce potable water.

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Degradation of Bacterial Water Quality in Drinking Water after Bottling

The Open Microbiology Journal ◽

10.2174/1874285802014010078 ◽

2020 ◽

Vol 14 (1) ◽

pp. 78-83

Author(s):

Ali Shahryari ◽

Charlotte D. Smith ◽

Abolfazl Amini

Keyword(s):

Water Quality ◽

Drinking Water ◽

Heterotrophic Bacteria ◽

Positive Association ◽

Ambient Air ◽

Bottled Water ◽

Plate Count ◽

Biochemical Tests ◽

Storage Duration

Background: The consumption of bottled water globally, including Iran, has increased tremendously in recent years. This study was designed to assess the bacteriological quality of bottled water and its compliance with the drinking water regulations. In addition, we evaluated bottled waters for the presence of a variety of genera of bacteria and the effect of storage duration on the extent of bacterial contamination. Methods: Four hundred samples of bottled water belonging to ten different Iranian brands with various production dates were purchased from supermarkets in Gorgan, Iran, from 2017 to 2018. Bacterial quality of bottled water was assessed using heterotrophic plate count (HPC) followed by usual biochemical tests for identification of bacterial genera, and by the API system. Results: The average HPC of bottled water was 9974 colony-forming units per milliliter (CFU/ml). Twelve genera were isolated, among which Bacillus spp. and Escherichia coli were the most and least abundant, respectively. Statistical analysis showed that there was a positive association between water quality and storage duration so that the highest microbial load occurred within the first to third months after bottling. Furthermore, the highest rate of contamination was observed in May when ambient air temperatures commonly reached 40 °C. Conclusion: The bacterial quality of bottled water was not according to the standard of drinking water quality. This study demonstrated the variation in bacterial levels after bottling, which indicates the presence of waterborne heterotrophic bacteria, some of which can pose severe health risks to consumers.

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