Bacteriological water quality changes in parallel pilot distribution systems

2016 ◽  
Vol 16 (6) ◽  
pp. 1710-1720 ◽  
Author(s):  
R. Fabris ◽  
K. Braun ◽  
L. Ho ◽  
J. Q. J. C. Verberk ◽  
M. Drikas
Keyword(s):  
Distribution System ◽  
Biological Treatment ◽  
Distribution Systems ◽  
Biological Stability ◽  
Cell Numbers ◽  
Cell Counts ◽  
Plate Counts ◽  
Heterotrophic Plate Counts ◽  
Treatment Step ◽  
Extensive Pilot

In a component of an extensive pilot distribution system (PDS) study, the effects of four different water qualities on biological stability in distributed water were investigated through identical (parallel) single-pass pipe arrangements. Through 24 months of monitoring, a number of key observations were made. Incorporation of a biological treatment step reduced the overall dissolved organic carbon (DOC) loss through the PDS by reducing biodegradable DOC (BDOC) within the water prior to distribution. In the absence of chlorine residuals, the proliferation of culturable organisms was favoured with considerably higher heterotrophic plate counts in samples at the outlet of the PDS. Despite different bacterial cell counts (measured by flow cytometry) entering each PDS from the four treatment streams, equivalent outlet cell numbers were achieved in all systems after 8 months' operation; however multi-step treatment streams took longer to reach equilibrium.

Coliforms and other microbial indicators occurrence in water and biofilm in full-scale distribution systems

2006 ◽  
Vol 54 (3) ◽  
pp. 41-48 ◽  
Author(s):  
M. Batté ◽  
C. Féliers ◽  
P. Servais ◽  
V. Gauthier ◽  
J.-C. Joret ◽  
...  
Keyword(s):  
Water Quality ◽  
Residence Time ◽  
Distribution Systems ◽  
Full Scale ◽  
Bacterial Indicators ◽  
Total Coliforms ◽  
E Coli ◽  
Plate Counts ◽  
Microbiological Water Quality ◽  
Heterotrophic Plate Counts

Biofilm and microbial water quality were studied in four middle size full-scale distribution systems (DS) in France serving 5,000–30,000 inhabitants (maximum residence time 23–160 h) through three sampling campaigns over 1 year. Three of these DSs were chosen because of a quite high occurrence of bacterial indicators (i.e. total coliforms), the last DS was considered as a reference. Biofilm was studied on cast iron coupons incubated for more than 1 month in devices continuously fed with water from the DS in conditions imitating those met in DS. The devices were located at different points (4–6) along each DS. The abundance of bacteria in biofilm was estimated by heterotrophic plate counts (HPC) after detachment of the biofilm from the support by sonication. Microbiological water quality was estimated in parallel; analysis of total coliforms, E. coli, enterococci and anaerobic sulphide-reducing bacteria spores (ASRB spores) was carried out in biofilm and water. Over the period of the study, 171 water samples and 57 biofilm samples were collected. Over these 171 waters, 19 (11%) were positive for at least one of the measured indicators while two biofilm samples were positive (3.5%). Significant differences were observed in the levels of contamination between the DSs. High residence time in the DS, low disinfectant residual and high temperature increased the risk of indicator occurrence in the water phase. Due to the low number of biofilm samples positive for bacterial indicators, the data collected in the present study did not allow observation of a direct association between biofilm and water contaminations, even if the occurrence of indicators in water appeared on DSs with the highest density of biofilm (HPC).

Characterization of Non-Enteric Bacterial Regrowth in the Water Supply Distribution Network from a Eutrophic Reservoir

1989 ◽  
Vol 21 (3) ◽  
pp. 49-53 ◽  
Author(s):  
R. A. Gibbs ◽  
C. R. Hayes
Keyword(s):  
Distribution System ◽  
Water Distribution ◽  
Pathogenic Bacteria ◽  
Seasonal Pattern ◽  
Distribution Network ◽  
Water Distribution Network ◽  
Bacterial Regrowth ◽  
Organic Carbon Concentration ◽  
Plate Counts ◽  
Heterotrophic Plate Counts

An area of a distribution network receiving organically rich treated water was studied for a period of one year to gain further understanding of the regrowth of bacteria in a water distribution network. These bacteria are considered to be harmless to man. Surveys additional to this study confirmed that enteroviruses and pathogenic bacteria (as defined by EC directives) were absent, consistent with the general absence of coliforms. Fixed points were sampled regularly for bacteriological analysis and for relevant physical and chemical parameters. Heterotrophic plate counts were carried out using standard methods and a study was conducted to test alternative techniques. It was found that bacterial regrowth occurred close to the treatment works and longer retention resulted in little increase in plate counts. Monochloramine residuals of 0.26mg/l or less did not prevent regrowth. The assimilable organic carbon concentration decreased through the distribution system and increased following booster chlorination. Plate counts showed a seasonal pattern peaking in the spring and autumn and decreasing in the summer and winter. The predominant genera of bacteria were Pseudomonas, Alcaligenes and Aeromonas with maximum counts of 17,000, 23,000 and 1,700 CFU/ml respectively. Heterotrophic plate counts using the R2A medium, spread plate method and 7 day incubation period were on average 190 times greater than counts using the UK standard method. The increase in count gained by using the alternative method was greatest at the sampling points furthest from the treatment works.

Chlorine requirement for biologically stable drinking water after nanofiltration

2013 ◽  
Vol 14 (3) ◽  
pp. 405-413
Author(s):  
Y. Ohkouchi ◽  
Y. Yata ◽  
R. Bun ◽  
S. Itoh
Keyword(s):  
Drinking Water ◽  
Water Distribution ◽  
Flow Reactor ◽  
Heterotrophic Bacteria ◽  
Tap Water ◽  
Biological Stability ◽  
Bacterial Regrowth ◽  
Chlorine Residual ◽  
Plate Counts ◽  
Heterotrophic Plate Counts

There is considerable interest in minimizing the chlorine residual in Japan's tap water because of increasing consumer complaints about the chlorinous odor of drinking water. However, minimization of the chlorine residual requires stricter control of biodegradable organics in finished water to ensure biological stability during water distribution. In this context, we investigated the improvement of biological stability of drinking water by nanofiltration (NF). The removal of assimilable organic carbon (AOC) was 52% on average, but showed large seasonal variation. It was found to be difficult to maintain the acceptable AOC level for biologically stable water by NF. In addition, significant bacterial regrowth in NF permeates was still observed without chlorination, although 52% AOC was removed. Then, the chlorine concentration required to prevent bacterial regrowth during distribution of nanofiltrated water was determined using continuous-flow reactor systems. The heterotrophic plate counts (HPC) densities in biofilm were monitored at different chlorine conditions. The results indicated that the NF process could significantly reduce the chlorine requirement of the finished water. The relationship between free chlorine residual and HPC in biofilm formed from 1 μgC AOC showed that a trace level of chlorine residual, <0.1 mg/L, could inactivate heterotrophic bacteria and prevent biofilm formation.

Bacterial Contamination Associated With Electronic Faucets: A New Risk for Healthcare Facilities

2001 ◽  
Vol 22 (4) ◽  
pp. 202-205 ◽  
Author(s):  
James Hargreaves ◽  
Larry Shireley ◽  
Shannon Hansen ◽  
Virginia Bren ◽  
Gordon Fillipi ◽  
...  
Keyword(s):  
Water Supply ◽  
Water Samples ◽  
Distribution System ◽  
Water Distribution ◽  
Healthcare Facilities ◽  
Surgical Critical Care ◽  
Plate Counts ◽  
City Water ◽  
Heterotrophic Plate Counts ◽  
The City

AbstractObjective:To investigate the safety of the hospital water supply following a major flood.Design:Surveillance was conducted of the hospital water supply as it entered the hospital and at randomly selected water faucets throughout the facility.Setting:A newly constructed surgical critical-care unit in a 265-bed community hospital that had to be evacuated and was out of operation for 6 weeks following a major flood of the city.Methods:Random water samples throughout the facility were analyzed for heterotrophic plate counts (HPCs), chlorine, and coliforms utilizing standard methods.Results:Water samples entering the hospital met appropriate standards, indicating the city water distribution system was not contaminated. Of 169 faucets tested, 13 (22%) of 59 electronic faucets exceeded the HPC threshold, and 12 (11%) of 110 manual faucets exceeded the HPC threshold (P<.14). A comparison of two brands of electronic faucets with manual faucets and with each other revealed that the HPC threshold was exceeded by 11 (32%) of 34 brand A faucets as compared to 12 (11%) of 110 manual faucets (P<.006). The HPC threshold was exceeded by 2 (8%) of 25 brand B faucets compared to 12 (11%) of 110 manual faucets (P<.94). Contamination rates of brand A and brand B faucets differed significantly (P<.003). Similar testing 2 months after hyperchlorination of the water supply indicated that the HPC threshold was exceeded by 16 (52%) of 31 brand A faucets compared to 10 (9.%) of 110 manual faucets (P<.0000003) and by 2 (18%) of 25 brand B faucets compared to 10 (9%) of 110 manual faucets (P=1.0).Conclusions:A certain brand of electronic water faucet used in the hospital was associated with unacceptable levels of microbial growth in water and was a continuing source of bacteria potentially hazardous to patients.

A systematic approach for the assessment of bacterial growth-controlling factors linked to biological stability of drinking water in distribution systems

2016 ◽  
Vol 16 (4) ◽  
pp. 865-880 ◽  
Author(s):  
E. I. Prest ◽  
F. Hammes ◽  
S. Kötzsch ◽  
M. C. M. van Loosdrecht ◽  
J. S. Vrouwenvelder
Keyword(s):  
Drinking Water ◽  
Organic Carbon ◽  
Bacterial Growth ◽  
Distribution System ◽  
Distribution Systems ◽  
Systematic Approach ◽  
Controlling Factors ◽  
Full Scale ◽  
Growth Potential ◽  
Biological Stability

A systematic approach is presented for the assessment of (i) bacterial growth-controlling factors in drinking water and (ii) the impact of distribution conditions on the extent of bacterial growth in full-scale distribution systems. The approach combines (i) quantification of changes in autochthonous bacterial cell concentrations in full-scale distribution systems with (ii) laboratory-scale batch bacterial growth potential tests of drinking water samples under defined conditions. The growth potential tests were done by direct incubation of water samples, without modification of the original bacterial flora, and with flow cytometric quantification of bacterial growth. This method was shown to be reproducible (ca. 4% relative standard deviation) and sensitive (detection of bacterial growth down to 5 µg L−1 of added assimilable organic carbon). The principle of step-wise assessment of bacterial growth-controlling factors was demonstrated on bottled water, shown to be primarily carbon limited at 133 (±18) × 103 cells mL−1 and secondarily limited by inorganic nutrients at 5,500 (±1,700) × 103 cells mL−1. Analysis of the effluent of a Dutch full-scale drinking water treatment plant showed (1) bacterial growth inhibition as a result of end-point chlorination, (2) organic carbon limitation at 192 (±72) × 103 cells mL−1 and (3) inorganic nutrient limitation at 375 (±31) × 103 cells mL−1. Significantly lower net bacterial growth was measured in the corresponding full-scale distribution system (176 (±25) × 103 cells mL−1) than in the laboratory-scale growth potential test of the same water (294 (±35) × 103 cells mL−1), highlighting the influence of distribution on bacterial growth. The systematic approach described herein provides quantitative information on the effect of drinking water properties and distribution system conditions on biological stability, which can assist water utilities in decision-making on treatment or distribution system improvements to better control bacterial growth during water distribution.

Biological Stability of Drinking Water in an Eastern China City

2011 ◽  
Vol 356-360 ◽  
pp. 2109-2113
Author(s):  
Lu Chen ◽  
Meng Hui Wang ◽  
Rui Bao Jia ◽  
Li Li
Keyword(s):  
Drinking Water ◽  
Organic Carbon ◽  
Distribution System ◽  
Distribution Systems ◽  
Eastern China ◽  
Great Influence ◽  
Available Phosphorus ◽  
Biological Stability ◽  
Pipe Water ◽  
The Difference

In this study, the indicators assimilable organic carbon (AOC), dissolved organic carbon (DOC), heterotrophic plate counts (HPC) and microbially available phosphorus (MAP) were measured to evaluate the biological stability of drinking water in Jinan, an east China city, which uses different water sources in its distribution system. The results were shown that the concentration of AOC below 50μg ac-C•L-1 covered the detection of 58% sampling points in the city distribution systems. The difference of source water exercised a great influence to the concentration of AOC. The lower heterotrophic colony counts were detected when the AOC values were higher, and vice versa. The value of AOC/DOC showed its irregularity. MAP was negatively correlated with the AOC. Higher values of AOC and HPC were detected in pumping water than that in pipe water, while values of MAP were equivalent to each othe

Continuous Ozonation of Polycyclic Aromatic Hydrocarbons in Oil/Water-Emulsions and Biodegradation of Oxidation Products

1999 ◽  
Vol 40 (4-5) ◽  
pp. 107-114 ◽  
Author(s):  
A. Kornmüller ◽  
U. Wiesmann
Keyword(s):  
Polycyclic Aromatic Hydrocarbons ◽  
Aromatic Hydrocarbons ◽  
Biological Treatment ◽  
Reaction Rate ◽  
Oxidation Products ◽  
Direct Reaction ◽  
Biological Degradation ◽  
Polycyclic Aromatic ◽  
Oil Water ◽  
Treatment Step

The continuous ozonation of polycyclic aromatic hydrocarbons (PAH) was studied in a two stage ozonation system followed by serobic biological degradation. The highly condensed PAH benzo(e)pyrene and benzo(k)fluoranthene were oxidized selectiely in synthetic oil/water-emulsions. The influence of the ozone mass transfer gas-liquid on the reaction rate of benzo(k)fluoranthene was studied for process optimization. The dissolved ozone concentration is influenced by temperature to a higher degree than the reaction rate of PAH. In dependence on pH, PAH oxidation occurs by a direct reaction with ozone inside the oil droplets. Two main ozonation products of benzo(e)pyrene were quantified at different retention times during ozonation and their transformation could be shown in the biological treatment step.

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