Tag Archives: distribution systems

Occurrence of Nonylphenol and Bisphenol A in Household Water Pipes

Cheng YC, Chen HW, Chen WL, Chen CY, Wang GS. Occurrence of nonylphenol and bisphenol A in household water pipes made of different materials. Environmental monitoring and assessment 2015 Oct;188(10):562. doi: 10.1007/s10661-016-5556-0.

We assessed the occurrence of nonylphenol (NP) and bisphenol A (BPA) in tap water supplied through polyvinyl chloride (PVC), stainless steel, and galvanized pipes. Water samples were collected from selected households in Taipei and Kaohsiung (Northern and Southern Taiwan, respectively) in different seasons to elucidate the effects of pipeline materials and ambient temperatures on NP and BPA concentrations in tap water. We detected higher concentrations of NP in tap water from households using PVC pipes (64-195 ng/L) than from those using stainless steel pipes (17-44 ng/L) and galvanized pipes (27-96 ng/L). To verify that water can absorb NP and BPA from PVC pipes, we sealed Milli-Q and tap water in PVC and stainless steel pipes to assess the potential release of NP and BPA from the pipes into the water. Both NP and BPA concentrations initially increased with contact time in the PVC pipes, and the concentration profiles during the retention appeared to be more strongly affected by ambient temperatures. Concentration variations in the stainless steel pipes were smaller than those in the PVC pipes.

Bacterial Repopulation of Drinking Water Pipe Walls After Chlorination

Mathieu L, Francius G, El Zein R, Angel E, Block JC. Bacterial repopulation of drinking water pipe walls after chlorination. Biofouling. Biofouling. 2016 Sep;32(8):925-34. doi: 10.1080/08927014.2016.1212989/

The short-term kinetics of bacterial repopulation were evaluated after chlorination of high-density polyethylene (HDPE) colonized with drinking water biofilms and compared with bare HDPE surfaces. The effect of chlorination was partial as a residual biofilm persisted and was time-limited as repopulation occurred immediately after water resupply. The total number of bacteria reached the same levels on both the bare and chlorinated biofilm-fouled HDPE after a seven-day exposure to drinking water. Due to the presence of a residual biofilm, the hydrophobicity of chlorinated biofilm-fouled surface exhibited much lower adhesion forces (2.1 nN) compared to bare surfaces (8.9 nN). This could explain the rapid repopulation after chlorination, with a twofold faster bacterial accumulation rate on the bare HDPE surface. γ-Proteobacteria dominated the early stages of repopulation of both surfaces and a shift in the dominance occurred over the colonization time. Such observations define a timescale for cleaning frequency in industrial environments and guidelines for a rinsing procedure using drinking water.

Controlling Biofilm Growth in Drinking Water Distribution Systems

Liu S, Gunawan C, Barraud N, Rice SA, Harry EJ, Amal R. Understanding, Monitoring and Controlling Biofilm Growth in Drinking Water Distribution Systems. Environ Sci Techno. 2016 Aug 1.

In drinking water distribution systems (DWDS), biofilms are the predominant mode of microbial growth with the presence of extracellular polymeric substance (EPS) protecting the biomass from environmental and shear stresses. Biofilm formation poses a significant problem to the drinking water industry as a potential source of bacterial contamination, including pathogens and in many cases also affecting the taste and odor of drinking water and promotes corrosion of pipes. This article critically reviews important research findings on biofilm growth in DWDS, examining the factors affecting their formation and characteristics, as well as the various technologies to characterize, monitor and ultimately, to control their growth. Research indicates that temperature fluctuations potentially affect not only the initial bacteria-to-surface attachment but also the growth rates of biofilms. For the latter, the effect is unique for each type of biofilm-forming bacteria – ammonia oxidizing bacteria for example, grow more developed biofilms at typical summer temperature of 22○C compared to 12○C in fall , while the opposite occurs for the pathogenic V. cholera. Recent investigations have found formation of thinner yet denser biofilms under high and turbulent flow regimes of drinking water, in comparison to the more porous and loosely attached biofilms at low flow rates. Further, in addition to the rather well-known tendency of significant biofilm growth on corrosion-prone metal pipes, research efforts also found leaching of growth-promoting organic compounds from the increasingly popular use of polymer-based pipes. Knowledge of the unique microbial members of drinking water biofilms and importantly, the influence of water characteristics and operational conditions on their growth, can be applied to optimize various operational parameters to minimize biofilm accumulation. More detailed characterizations of the biofilm population size and structure are now feasible with fluorescence microscopy (epifluorescence and CLSM imaging with DNA, RNA, EPS, protein and lipid stains) and electron microscopy imaging (ESEM). Importantly, thorough identification of microbial fingerprints in drinking water biofilms is achievable with DNA sequencing techniques (the 16S rRNA gene-based identification), which have revealed prevalence of previously undetected bacterial members. Technologies are now moving toward in situ monitoring of biomass growth in distribution networks, including the development of optical fibres capable of differentiating biomass from chemical deposits. Taken together, management of biofilm growth in water distribution systems requires an integrated approach, starting from treatment of water prior to entering the networks, to potential implementation of ‘biofilm-limiting’ operational conditions and finally, to the careful selection of available technologies for biofilm monitoring and control. For the latter, conventional practices, including chlorine – chloramine disinfection, flushing of DWDS as well as nutrient removal, and emerging technologies are discussed with their associated challenges.

Factors Influencing Bacterial Diversity in Municipal Drinking Waters, Ohio

Stanish LF, Hull NM, Robertson CE, Harris JK, Stevens MJ, Spear JR, et al. (2016) Factors Influencing Bacterial Diversity and Community Composition in Municipal Drinking Waters in the Ohio River Basin, USA. PLoS ONE 11(6): e0157966. doi:10.1371/journal.pone.0157966

The composition and metabolic activities of microbes in drinking water distribution systems can affect water quality and distribution system integrity. In order to understand regional variations in drinking water microbiology in the upper Ohio River watershed, the chemical and microbiological constituents of 17 municipal distribution systems were assessed. While sporadic variations were observed, the microbial diversity was generally dominated by fewer than 10 taxa, and was driven by the amount of disinfectant residual in the water. Overall, Mycobacterium spp. (Actinobacteria), MLE1-12 (phylum Cyanobacteria), Methylobacterium spp., and sphingomonads were the dominant taxa. Shifts in community composition from Alphaproteobacteria and Betaproteobacteria to Firmicutes and Gammaproteobacteria were associated with higher residual chlorine. Alpha- and beta-diversity were higher in systems with higher chlorine loads, which may reflect changes in the ecological processes structuring the communities under different levels of oxidative stress. These results expand the assessment of microbial diversity in municipal distribution systems and demonstrate the value of considering ecological theory to understand the processes controlling microbial makeup. Such understanding may inform the management of municipal drinking water resources.

 

Another GI Illness and Emergency Dept Visit Study, Atlanta, Georgia

The use of water residence time as a proxy for contamination by intrusion into a water distribution system is unsupported and speculative at best. It seems these researchers do not fully understand drinking water distribution systems.  Lastly, the ORs and CIs mentioned here are very low and are well within the range of no-effect.  Why speculate with such a weak finding?  Let’s use some common sense to operate and maintain water distribution systems and disinfectant residuals.

Levy K, Klein M, Sarnat SE, Panwhar S, Huttinger A, Tolbert P, Moe C. Refined assessment of associations between drinking water residence time and emergency department visits for gastrointestinal illness in Metro Atlanta, Georgia. Journal of Water and Health. 2016 Aug;14(4):672-681.

Recent outbreak investigations suggest that a substantial proportion of waterborne disease outbreaks are attributable to water distribution system issues. In this analysis, we examine the relationship between modeled water residence time (WRT), a proxy for probability of microorganism intrusion into the distribution system, and emergency department visits for gastrointestinal (GI) illness for two water utilities in Metro Atlanta, USA during 1993-2004. We also examine the association between proximity to the nearest distribution system node, based on patients’ residential address, and GI illness using logistic regression models. Comparing long (≥90th percentile) with intermediate WRTs (11th to 89th percentile), we observed a modestly increased risk for GI illness for Utility 1 (OR = 1.07, 95% CI: 1.02-1.13), which had substantially higher average WRT than Utility 2, for which we found no increased risk (OR = 0.98, 95% CI: 0.94-1.02). Examining finer, 12-hour increments of WRT, we found that exposures >48 h were associated with increased risk of GI illness, and exposures of >96 h had the strongest associations, although none of these associations was statistically significant. Our results suggest that utilities might consider reducing WRTs to <2-3 days or adding booster disinfection in areas with longer WRT, to minimize risk of GI illness from water consumption.

Hypothetical Study of Intentional Microbial Contamination of Distribution Systems

A hypothetical study such as this useful but can be very alarming. Keep in mind that actually contaminating a distribution system is much easier said than done. The threat is considered low because the contaminant will be diluted during hyrdaulic transport through the piping system and may not reach the tap. Factors such as chlorine residual disinfectant in the distribution system will inactivate microbial pathogens. Shower exposures are important not only here but also in the case of other drinking water contaminants such as radon.

Jack Schijven, Jean Marie Forêt, Jurgen Chardon, Peter Teunis, Martijn Bouwknegt, Ben Tangena. Evaluation of exposure scenarios on intentional microbiological contamination in a drinking water distribution network. Water Research, Volume 96, 1 June 2016, Pages 148-154.

Drinking water distribution networks are vulnerable to accidental or intentional contamination events. The objective of this study was to investigate the effects of seeding duration and concentration, exposure pathway (ingestion via drinking of water and tooth brushing and inhalation by taking a shower) and pathogen infectivity on exposure and infection risk in the case of an intentional pathogenic contamination in a drinking water distribution network. Seeding of a pathogen for 10 min and 120 min, and subsequent spreading through a drinking water distribution network were simulated. For exposure via drinking, actual data on drinking events and volumes were used. Ingestion of a small volume of water by tooth brushing twice a day by every person in the network was assumed. Inhalation of contaminated aerosol droplets took place when taking a shower. Infection risks were estimated for pathogens with low (r = 0.0001) and high (r = 0.1) infectivity. In the served population (48 000 persons) and within 24 h, about 1400 persons were exposed to the pathogen by ingestion of water in the 10-min seeding scenario and about 3400 persons in the 120-min scenario. The numbers of exposed persons via tooth brushing were about the same as via drinking of water. Showering caused (inhalation) exposure in about 450 persons in the 10-min scenario and about 1500 in the 120-min scenario. Regardless of pathogen infectivity, if the seeding concentration is 106 pathogens per litre or more, infection risks are close to one. Exposure by taking a shower is of relevance if the pathogen is highly infectious via inhalation. A longer duration of the seeding of a pathogen increases the probability of exposure.

Archaeal and Bacterial Community Structure, Nitrifying Microorganisms

Zsuzsanna Nagymáté, Zalán G. Homonnay, Károly Márialigeti. Investigation of Archaeal and Bacterial community structure of five different small drinking water networks with special regard to the nitrifying microorganisms. Microbiological Research, Volumes 188–189, July–August 2016, Pages 80-89.

Total microbial community structure, and particularly nitrifying communities inhabiting five different small drinking water networks characterized with different water physical and chemical parameters was investigated, using cultivation-based methods and sequence aided Terminal Restriction Fragment Length Polymorphism (T-RFLP) analysis. Ammonium ion, originated from well water, was only partially oxidized via nitrite to nitrate in the drinking water distribution systems. Nitrification occurred at low ammonium ion concentration (27–46 μM), relatively high pH (7.6–8.2) and over a wide range of dissolved oxygen concentrations (0.4–9.0 mg L−1). The nitrifying communities of the distribution systems were characterized by variable most probable numbers (2 × 102–7.1 × 104 MPN L−1) and probably originated from the non-treated well water. The sequence aided T-RFLP method revealed that ammonia-oxidizing microorganisms and nitrite-oxidizing Bacteria (Nitrosomonas oligotropha, Nitrosopumilus maritimus, and Nitrospira moscoviensis,Candidatus Nitrospira defluvii’) were present in different ratios in the total microbial communities of the distinct parts of the water network systems. The nitrate generated by nitrification was partly utilized by nitrate-reducing (and denitrifying) Bacteria, present in low MPN and characterized by sequence aided T-RFLP as Comamonas sp. andPseudomonas spp. Different environmental factors, like pH, chemical oxygen demand, calculated total inorganic nitrogen content (moreover nitrite and nitrate concentration), temperature had important effect on the total bacterial and archaeal community distribution.