scholarly journals Deficiencies in drinking water distribution systems in developing countries

2005 ◽  
Vol 3 (2) ◽  
pp. 109-127 ◽  
Author(s):  
Ellen J. Lee ◽  
Kellogg J. Schwab
Keyword(s):  
Developing Countries ◽  
Drinking Water ◽  
Distribution System ◽  
Urban Areas ◽  
Distribution Systems ◽  
Water Distribution ◽  
Water Pressure ◽  
Drinking Water Treatment ◽  
Human Consumption ◽  
Drinking Water Distribution Systems

Rapidly growing populations and migration to urban areas in developing countries has resulted in a vital need for the establishment of centralized water systems to disseminate potable water to residents. Protected source water and modern, well-maintained drinking water treatment plants can provide water adequate for human consumption. However, ageing, stressed or poorly maintained distribution systems can cause the quality of piped drinking water to deteriorate below acceptable levels and pose serious health risks. This review will outline distribution system deficiencies in developing countries caused by: the failure to disinfect water or maintain a proper disinfection residual; low pipeline water pressure; intermittent service; excessive network leakages; corrosion of parts; inadequate sewage disposal; and inequitable pricing and usage of water. Through improved research, monitoring and surveillance, increased understanding of distribution system deficiencies may focus limited resources on key areas in an effort to improve public health and decrease global disease burden.

scholarly journals Prevalence of bacterial pathogens in biofilms of drinking water distribution systems

2007 ◽  
Vol 5 (2) ◽  
pp. 219-227 ◽  
Author(s):  
S. M. September ◽  
F. A. Els ◽  
S. N. Venter ◽  
V. S. Brözel
Keyword(s):  
Drinking Water ◽  
Distribution System ◽  
Distribution Systems ◽  
Water Distribution ◽  
Most Probable Number ◽  
Human Consumption ◽  
Probable Number ◽  
Drinking Water Distribution Systems ◽  
Colony Forming Units ◽  
Drinking Water Distribution

Water for human consumption is required to be free from any bacteria that might pose a health risk. The presence of biofilms in the drinking water distribution system may play a role in the presence of potential pathogens in the drinking water supply. Ninety-five biofilm samples from various parts of South Africa were tested for the presence of Escherichia coli, Aeromonas, Pseudomonas, Salmonella, Shigella and Vibrio spp. Members of these genera were quantified by the three-tube most probable number (MPN) approach using enrichment broths and plating on selective agars. The heterotrophic culturable counts were determined for both the planktonic and biofilm phases of the samples. Biofilm density varied between 10 and 1.9 × 109 colony forming units cm−2. The 16S rRNA identity of the putative pathogenic isolates revealed that high numbers of Aeromonas, Pseudomonas,Klebsiella and Enterobacter were present, but no putative Salmonella and Shigella could be confirmed. None of the Pseudomonas isolates belonged to the pathogenic Pseudomonas aeruginosa or Pseudomonas mendocina while the Aeromonas isolates showed relatedness to known pathogenic members of this group.

Control of biofilm growth in drinking water distribution system by biodegradable carbon and disinfectant residuals

2006 ◽  
Vol 6 (2) ◽  
pp. 147-151 ◽  
Author(s):  
X.-J. Zhang ◽  
W. Lu
Keyword(s):  
Drinking Water ◽  
Distribution System ◽  
Distribution Systems ◽  
Water Distribution ◽  
Free Water ◽  
Planktonic Cell ◽  
Biofilm Growth ◽  
Bacteria Growth ◽  
Drinking Water Distribution Systems ◽  
Drinking Water Distribution

Biofilm growth in drinking water distribution systems was studied in an annular reactor system which was designed to model the hydraulic conditions in water mains. Experiments were performed with chlorine-free water as well as with different disinfectant (chlorine or chloramine) residuals and different AOC concentrations added to the reactor influent to examine the effect of disinfectant residuals and AOC concentrations on biofilm accumulation and planktonic cell numbers. The dynamic parameters of bacteria growth were calculated in water with different disinfectant (chlorine or chloramine) and the results indicated that monochloramine may be more effective than free chlorine for control of biofilm accumulation.

Prediction of chlorine and trihalomethanes concentration profile in bulk drinking water distribution systems from laboratory data

2003 ◽  
Vol 3 (1-2) ◽  
pp. 239-246 ◽  
Author(s):  
G. Kastl ◽  
I. Fisher ◽  
V. Jegatheesan ◽  
J. Chandy ◽  
K. Clarkson
Keyword(s):  
Drinking Water ◽  
Distribution System ◽  
Distribution Systems ◽  
Water Distribution ◽  
Laboratory Data ◽  
Water Distribution Systems ◽  
Optimum Level ◽  
Drinking Water Distribution Systems ◽  
Drinking Water Distribution ◽  
Chlorine Decay

Nearly all drinking water distribution systems experience a “natural” reduction of disinfection residuals. The most frequently used disinfectant is chlorine, which can decay due to reactions with organic and inorganic compounds in the water and by liquid/solids reaction with the biofilm, pipe walls and sediments. Usually levels of 0.2-0.5 mg/L of free chlorine are required at the point of consumption to maintain bacteriological safety. Higher concentrations are not desirable as they present the problems of taste and odour and increase formation of disinfection by-products. It is usually a considerable concern for the operators of drinking water distribution systems to manage chlorine residuals at the “optimum level”, considering all these issues. This paper describes how the chlorine profile in a drinking water distribution system can be modelled and optimised on the basis of readily and inexpensively available laboratory data. Methods are presented for deriving the laboratory data, fitting a chlorine decay model of bulk water to the data and applying the model, in conjunction with a simplified hydraulic model, to obtain the chlorine profile in a distribution system at steady flow conditions. Two case studies are used to demonstrate the utility of the technique. Melbourne’s Greenvale-Sydenham distribution system is unfiltered and uses chlorination as its only treatment. The chlorine model developed from laboratory data was applied to the whole system and the chlorine profile was shown to be accurately simulated. Biofilm was not found to critically affect chlorine decay. In the other case study, Sydney Water’s Nepean system was modelled from limited hydraulic data. Chlorine decay and trihalomethane (THM) formation in raw and treated water were measured in a laboratory, and a chlorine decay and THM model was derived on the basis of these data. Simulated chlorine and THM profiles agree well with the measured values available. Various applications of this modelling approach are also briefly discussed.

Spatial variation of loose deposit characteristics in a 40 km long operational drinking water distribution system

2019 ◽  
Vol 5 (10) ◽  
pp. 1689-1698
Author(s):  
Xu Ma ◽  
Guiwei Li ◽  
Ying Yu ◽  
Ruya Chen ◽  
Yao Zhang ◽  
...  
Keyword(s):  
Drinking Water ◽  
Distribution System ◽  
Distribution Systems ◽  
Water Distribution ◽  
Water Distribution System ◽  
Eastern China ◽  
Drinking Water Distribution Systems ◽  
System P ◽  
Loose Deposit ◽  
Drinking Water Distribution

Discoloration problems have occurred in drinking water distribution systems continuously for several years in a rural area of eastern China.

scholarly journals Effect of Phosphorus on Survival of Escherichia coli in Drinking Water Biofilms

2007 ◽  
Vol 73 (11) ◽  
pp. 3755-3758 ◽  
Author(s):  
Talis Juhna ◽  
Dagne Birzniece ◽  
Janis Rubulis
Keyword(s):  
Escherichia Coli ◽  
Drinking Water ◽  
Distribution System ◽  
Distribution Systems ◽  
Water Distribution ◽  
Water Distribution System ◽  
Phosphorus Addition ◽  
Drinking Water Distribution Systems ◽  
E Coli ◽  
Drinking Water Distribution

ABSTRACT The effect of phosphorus addition on survival of Escherichia coli in an experimental drinking water distribution system was investigated. Higher phosphorus concentrations prolonged the survival of culturable E. coli in water and biofilms. Although phosphorus addition did not affect viable but not culturable (VBNC) E. coli in biofilms, these structures could act as a reservoir of VBNC forms of E. coli in drinking water distribution systems.

The Laboratory Study of Drinking Water Biofilms

2014 ◽  
Vol 535 ◽  
pp. 455-459
Author(s):  
Jing Guo Zhao ◽  
Yu Long Yang ◽  
Cong Li
Keyword(s):  
Drinking Water ◽  
Water Temperature ◽  
Distribution System ◽  
Distribution Systems ◽  
Water Distribution ◽  
Future Research ◽  
Pipe Material ◽  
Drinking Water Distribution Systems ◽  
Drinking Water Distribution ◽  
Key Aspects

Due to the existence of some kinds of minim organic matters in drinking water distribution systems, biofilms are commonly found on the inner walls of pipe networks, and it can contribute to the deterioration to water quality and influence water supply security. The current situations of the study of the biofilm are summarized. Two typical kinds of reactors often used in laboratories are stated. And numerous environmental factors influencing biofilm formation, including hydraulic condition, water temperature, pipe material, water temperature, disinfectant residuals and nutrient element, are reviewed. Furthermore, some key aspects for future research to control the development of biofilms are proposed. Keywords: drinking water distribution system; biofilm; simulation system; disinfectant residual

The biological safety of distribution systems following UV disinfection in rural areas in Beijing, China

2013 ◽  
Vol 13 (3) ◽  
pp. 854-863 ◽  
Author(s):  
Wenjun Sun ◽  
Wenjun Liu ◽  
Lifeng Cui ◽  
Leibin Liu
Keyword(s):  
Drinking Water ◽  
Rural Areas ◽  
Distribution System ◽  
Distribution Systems ◽  
Water Distribution ◽  
Water Distribution System ◽  
Drinking Water Treatment ◽  
Uv Disinfection ◽  
Biological Safety ◽  
Drinking Water Standard

In rural areas, UV disinfection has a great potential for drinking water treatment because of the ability to achieve target disinfection levels and the ease of operation and maintenance; however, UV disinfection provides no disinfection residual to the water distribution system. This study examines the biological safety of rural water distribution systems following UV disinfection. The results showed that in all the tested villages, heterotrophic plate counts (HPC) were below 500 colony-forming units (CFU)/mL and total bacterial counts (TBC) were below 100 CFU/mL. Both meet the drinking water standard in China. The HPC concentration was related to the water temperature, the assimilable organic carbon (AOC) and water distribution system conditions. Total coliforms were detectable at some water distribution system sampling points in two out of eight villages.

scholarly journals Persistence of Nontuberculous Mycobacteria in a Drinking Water System after Addition of Filtration Treatment

2006 ◽  
Vol 72 (9) ◽  
pp. 5864-5869 ◽  
Author(s):  
Elizabeth D. Hilborn ◽  
Terry C. Covert ◽  
Mitchell A. Yakrus ◽  
Stephanie I. Harris ◽  
Sandra F. Donnelly ◽  
...  
Keyword(s):  
Drinking Water ◽  
Distribution System ◽  
Distribution Systems ◽  
Water Distribution ◽  
Cold Water ◽  
Nontuberculous Mycobacteria ◽  
Treatment Plant ◽  
Water System ◽  
Drinking Water Treatment ◽  
Drinking Water System

ABSTRACT There is evidence that drinking water may be a source of infections with pathogenic nontuberculous mycobacteria (NTM) in humans. One method by which NTM are believed to enter drinking water distribution systems is by their intracellular colonization of protozoa. Our goal was to determine whether we could detect a reduction in the prevalence of NTM recovered from an unfiltered surface drinking water system after the addition of ozonation and filtration treatment and to characterize NTM isolates by using molecular methods. We sampled water from two initially unfiltered surface drinking water treatment plants over a 29-month period. One plant received the addition of filtration and ozonation after 6 months of sampling. Sample sites included those at treatment plant effluents, distributed water, and cold water taps (point-of-use [POU] sites) in public or commercial buildings located within each distribution system. NTM were recovered from 27% of the sites. POU sites yielded the majority of NTM, with >50% recovery despite the addition of ozonation and filtration. Closely related electrophoretic groups of Mycobacterium avium were found to persist at POU sites for up to 26 months. Water collected from POU cold water outlets was persistently colonized with NTM despite the addition of ozonation and filtration to a drinking water system. This suggests that cold water POU outlets need to be considered as a potential source of chronic human exposure to NTM.

scholarly journals Dynamic Hydraulics in a Drinking Water Distribution System Influence Suspended Particles and Turbidity, But Not Microbiology

Water ◽  
2021 ◽  
Vol 13 (1) ◽  
pp. 109
Author(s):  
Emmanuelle I. Prest ◽  
Peter G. Schaap ◽  
Michael D. Besmer ◽  
Frederik Hammes
Keyword(s):  
Drinking Water ◽  
Distribution System ◽  
Distribution Systems ◽  
Water Distribution ◽  
Water Age ◽  
Short Term ◽  
Drinking Water Distribution Systems ◽  
Hydraulic Conditions ◽  
Drinking Water Distribution ◽  
Particle Counts

Spatial and short-term temporal changes in water quality as a result of water age and fluctuating hydraulic conditions were investigated in a drinking water distribution system. Online measurements of total and intracellular adenosine tri-phosphate (ATP), total and intact cell concentrations measured with flow cytometry (FCM), turbidity, and particle counts were performed over five weeks at five subsequent locations of the distribution system. The high number of parallel FCM and ATP measurements revealed the combined effect of water age and final disinfection on spatial changes in microbiology in the system. The results underlined that regular daily dynamics in flow velocities are normal and inevitable in drinking water distribution systems, and significantly impact particle counts and turbidity. However, hydraulic conditions had no detectable impact on the concentration of suspended microbial cells. A weak correlation between flow velocity and ATP concentrations suggests incidental resuspension of particle-bound bacteria, presumably caused by either biofilm detachment or resuspension from sediment when flow velocities increase. The highly dynamic hydraulic conditions highlight the value of online monitoring tools for the meaningful description of short-term dynamics (day-scale) in drinking water distribution systems.

The occurrence of filamentous fungi in drinking water distribution systems

1982 ◽  
Vol 28 (6) ◽  
pp. 667-671 ◽  
Author(s):  
L. A. Nagy ◽  
B. H. Olson
Keyword(s):  
Drinking Water ◽  
Filamentous Fungi ◽  
Distribution System ◽  
Membrane Filtration ◽  
Distribution Systems ◽  
Water Distribution ◽  
Drinking Water Distribution Systems ◽  
Colony Forming Units ◽  
Drinking Water Distribution ◽  
Fungal Colony

The densities of filamentous fungal colonies, together with physicochemical and bacteriological parameters, were assessed in a chlorinated and unchlorinated drinking water distribution system at eight separate times over a period of 1 year. Filamentous fungal colonies were enumerated by membrane filtration on Czapek–Dox agar. The mean number of filamentous fungal colony-forming units per 100 mL of drinking water was 18 in the unchlorinated and 34 in the chlorinated system. The majority of filamentous fungi isolated were saprophytic Deuteromycotina. The four most frequently occurring genera were Penicillium, Sporocybe, Acremonium, and Paecilomyces. In the chlorinated system, only physicochemical parameters correlated with observed fungal frequencies, whereas in the unchlorinated system, none of the parameters exhibited significant correlations with fungal numbers.

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