Biofilm Composition and Threshold Concentration for Growth of Legionella pneumophila on Surfaces Exposed to Flowing Warm Tap Water without Disinfectant

ABSTRACT Legionella pneumophila in potable water installations poses a potential health risk, but quantitative information about its replication in biofilms in relation to water quality is scarce. Therefore, biofilm formation on the surfaces of glass and chlorinated polyvinyl chloride (CPVC) in contact with tap water at 34 to 39°C was investigated under controlled hydraulic conditions in a model system inoculated with biofilm-grown L. pneumophila. The biofilm on glass (average steady-state concentration, 23 ± 9 pg ATP cm−2) exposed to treated aerobic groundwater (0.3 mg C liter−1; 1 μg assimilable organic carbon [AOC] liter−1) did not support growth of the organism, which also disappeared from the biofilm on CPVC (49 ± 9 pg ATP cm−2) after initial growth. L. pneumophila attained a level of 4.3 log CFU cm−2 in the biofilms on glass (1,055 ± 225 pg ATP cm−2) and CPVC (2,755 ± 460 pg ATP cm−2) exposed to treated anaerobic groundwater (7.9 mg C liter−1; 10 μg AOC liter−1). An elevated biofilm concentration and growth of L. pneumophila were also observed with tap water from the laboratory. The Betaproteobacteria Piscinibacter and Methyloversatilis and amoeba-resisting Alphaproteobacteria predominated in the clones and isolates retrieved from the biofilms. In the biofilms, the Legionella colony count correlated significantly with the total cell count (TCC), heterotrophic plate count, ATP concentration, and presence of Vermamoeba vermiformis. This amoeba was rarely detected at biofilm concentrations of <100 pg ATP cm−2. A threshold concentration of approximately 50 pg ATP cm−2 (TCC = 1 × 106 to 2 × 106 cells cm−2) was derived for growth of L. pneumophila in biofilms. IMPORTANCE Legionella pneumophila is the etiologic agent in more than 10,000 cases of Legionnaires' disease that are reported annually worldwide and in most of the drinking water-associated disease outbreaks reported in the United States. The organism proliferates in biofilms on surfaces exposed to warm water in engineered freshwater installations. An investigation with a test system supplied with different types of warm drinking water without disinfectant under controlled hydraulic conditions showed that treated aerobic groundwater (0.3 mg liter−1 of organic carbon) induced a low biofilm concentration that supported no or very limited growth of L. pneumophila. Elevated biofilm concentrations and L. pneumophila colony counts were observed on surfaces exposed to two types of extensively treated groundwater, containing 1.8 and 7.9 mg C liter−1 and complying with the microbial water quality criteria during distribution. Control measures in warm tap water installations are therefore essential for preventing growth of L. pneumophila.

Download Full-text

The impact of investment on drinking water quality in rural China

China Agricultural Economic Review ◽

10.1108/caer-05-2015-0062 ◽

2017 ◽

Vol 9 (2) ◽

pp. 255-269

Author(s):

Ai Yue ◽

Yaojiang Shi ◽

Renfu Luo ◽

Linxiu Zhang ◽

Natalie Johnson ◽

...

Keyword(s):

Water Quality ◽

Drinking Water ◽

Rural Areas ◽

Tap Water ◽

Rural China ◽

Ordinary Least Squares ◽

Content Type ◽

Representative Data ◽

Nationally Representative ◽

The Impact

Purpose Although access to safe drinking water is one of the most important health-related infrastructure programs in the world, drinking water remains a large problem in China today, especially in rural areas. Despite increased government investment in water resource protection and management, there is still an absence of academic studies that are able to document what path the investment has taken and whether it has had any tangible impact. The purpose of this paper is to analyze the impact of drinking water investment on drinking water in China. Design/methodology/approach The authors make use of nationally representative data from 2005 and 2012 to measure the impact of drinking water investment among 2,028 rural households in 101 villages across five provinces. Both ordinary least squares regression and probit regression are used to analyze the correlates and the impact of drinking water investment. Findings The authors demonstrate that water quality was likely a significant problem in 2004 but that China’s investment into drinking water appears to have resulted in initial improvements during the study period. The authors show that the most significant change came about in terms of hardware: villages that received more drinking water investment now have more piped tap water and more access to water treatment infrastructure (disinfecting and filtering facilities). High rates of rural resident satisfaction with drinking water suggest the effects of drinking water investment are being felt at the village level. Originality/value To the authors’ knowledge, this is the first empirical study on drinking water investment over time in rural China using nationally representative data.

Download Full-text

Nontuberculous Mycobacteria, Fungi, and Opportunistic Pathogens in Unchlorinated Drinking Water in the Netherlands

Applied and Environmental Microbiology ◽

10.1128/aem.02748-12 ◽

2012 ◽

Vol 79 (3) ◽

pp. 825-834 ◽

Cited By ~ 64

Author(s):

Paul W. J. J. van der Wielen ◽

Dick van der Kooij

Keyword(s):

Drinking Water ◽

Organic Carbon ◽

The Netherlands ◽

Legionella Pneumophila ◽

Water Samples ◽

Distribution System ◽

Nontuberculous Mycobacteria ◽

Opportunistic Pathogens ◽

Content Type ◽

Premise Plumbing

ABSTRACTThe multiplication of opportunistic pathogens in drinking water supplies might pose a threat to public health. In this study, distributed unchlorinated drinking water from eight treatment plants in the Netherlands was sampled and analyzed for fungi, nontuberculous mycobacteria (NTM), and several opportunistic pathogens by using selective quantitative PCR methods. Fungi and NTM were detected in all drinking water samples, whereasLegionella pneumophila,Pseudomonas aeruginosa,Stenotrophomonas maltophilia, andAspergillus fumigatuswere sporadically observed.Mycobacterium aviumcomplex andAcanthamoebaspp. were not detected. Season had no influence on the occurrence of these organisms, except for NTM andS. maltophilia, which were present in higher numbers in the summer. Opportunistic pathogens were more often observed in premise plumbing water samples than in samples from the distribution system. The lowest number of these organisms was observed in the finished water at the plant. Thus, fungi, NTM, and some of the studied opportunistic pathogens can multiply in the distribution and premise plumbing systems. Assimilable organic carbon (AOC) and/or total organic carbon (TOC) had no clear effects on fungal and NTM numbers or onP. aeruginosa- andS. maltophilia-positive samples. However,L. pneumophilawas detected more often in water with AOC concentrations above 10 μg C liter−1than in water with AOC levels below 5 μg C liter−1. Finally, samples that containedL. pneumophila,P. aeruginosa, orS. maltophiliawere more frequently positive for a second opportunistic pathogen, which shows that certain drinking water types and/or sampling locations promote the growth of multiple opportunistic pathogens.

Download Full-text

The Need for New Microbiological Water Quality Criteria

Water Science & Technology ◽

10.2166/wst.1991.0027 ◽

1991 ◽

Vol 24 (2) ◽

pp. 43-48 ◽

Cited By ~ 4

Author(s):

Helmy T. El-Zanfaly

Keyword(s):

Public Health ◽

Water Quality ◽

Drinking Water ◽

Plate Count ◽

Resistant Bacteria ◽

Water Quality Criteria ◽

Antibiotic Resistant Bacteria ◽

Gram Positive ◽

Antibiotic Resistant ◽

Gram Negative

The microbiological criteria for water quality have been directed towards protection of consumers from possible microbial pollution which may cause public health hazards. Therefore, the bacteriological standards for drinking water are based mainly on bacterial indicators. Another problem of prime concern to public health is the presence of antibiotic-resistant bacteria in drinking water Antibiotic–resistant bacteria were found among standard plate count populations of Chlorinated drinking water from two districts in Cairo. Most strains appeared to be ampicillin resistant (89%). Those were followed by sulfaguanidine (78%) and streptomycin (57%). The majority of the tested strains (62.4 to 98%) were multiple antibiotic resistant (MAR). Identification of 363 MAR strains revealed that Gram-positive rods were dominant, while Gram-negative fermentative rods, Gram-positive cocci and Gram-negative nonfermentative rods represent the second, third and fourth group. A total of 101 strains isolated from underground water pumped from three water works in Cairo were classified and tested for their resistance towards four commonly used antibiotics; chloramphenicol, tetracycline, neomycin, penicillin and one chemotherapeutic agent namely sulfanilamide pyrimidine. Results showed that 77, 64 and 32 isolates have resistance towards penicillin, sulfanilamide pyrimidine and tetracycline, respectively. Only 18 and 8 isolates were resistant to chloramphenicol and neomycin, respectively. It was also found that 19 isolates belonging to 6 genera or groups were sensitive towards all of the tested compounds. Therefore, any source of antibiotic~resistant bacteria must be viewed with concern and use of data on MAR bacteria should be made in future water quality deliberations and in regulating effluent quality discharges.

Download Full-text

How Perceptions of Trust, Risk, Tap Water Quality, and Salience Characterize Drinking Water Choices

Hydrology ◽

10.3390/hydrology8010049 ◽

2021 ◽

Vol 8 (1) ◽

pp. 49

Author(s):

Madeline A. Grupper ◽

Madeline E. Schreiber ◽

Michael G. Sorice

Keyword(s):

Water Quality ◽

Drinking Water ◽

Risk Perceptions ◽

Anthropogenic Impacts ◽

Tap Water ◽

Water Utilities ◽

Global Changes ◽

Water Utility ◽

The Public ◽

Water Behavior

Provision of safe drinking water by water utilities is challenged by disturbances to water quality that have become increasingly frequent due to global changes and anthropogenic impacts. Many water utilities are turning to adaptable and flexible strategies to allow for resilient management of drinking water supplies. The success of resilience-based management depends on, and is enabled by, positive relationships with the public. To understand how relationships between managers and communities spill over to in-home drinking water behavior, we examined the role of trust, risk perceptions, salience of drinking water, and water quality evaluations in the choice of in-home drinking water sources for a population in Roanoke Virginia. Using survey data, our study characterized patterns of in-home drinking water behavior and explored related perceptions to determine if residents’ perceptions of their water and the municipal water utility could be intuited from this behavior. We characterized drinking water behavior using a hierarchical cluster analysis and highlighted the importance of studying a range of drinking water patterns. Through analyses of variance, we found that people who drink more tap water have higher trust in their water managers, evaluate water quality more favorably, have lower risk perceptions, and pay less attention to changes in their tap water. Utility managers may gauge information about aspects of their relationships with communities by examining drinking water behavior, which can be used to inform their future interactions with the public, with the goal of increasing resilience and adaptability to external water supply threats.

Download Full-text

Predicting Source Water Quality Following Wildfires Using Hydrologic Modeling

10.5194/egusphere-egu21-78 ◽

2021 ◽

Author(s):

Katie Wampler ◽

Kevin D. Bladon ◽

Monireh Faramarzi

Keyword(s):

Water Quality ◽

Drinking Water ◽

Organic Carbon ◽

The United States ◽

First Year ◽

Model Parameters ◽

Source Water ◽

Forested Watersheds ◽

Field Samples ◽

The World

<p>Forested watersheds are critical sources of the majority of the world&#8217;s drinking water. Almost one-third of the world&#8217;s largest cities and two-thirds of cities in the United States (US) rely on forested watersheds for their water supply. These forested regions are vulnerable to the increasing incidence of large and severe wildfires due to increases in regional temperatures and greater accumulation of fuels. When wildfires occur, increases in suspended sediment and organic carbon can negatively affect aquatic ecosystem health and create many costly challenges to the drinking water treatment process. These effects are often largest in the first year following a wildfire. While past research has shown the likelihood of source water impacts from wildfire, the magnitude of effects remains uncertain in most regions. In our study, we will quantify the projected short-term effects of three large (>70,000 ha) wildfires on key water quality parameters (sediment and organic carbon) in two important forested source watersheds in the Cascade Range of Oregon, US. We calibrated and validated a modified Soil and Water Assessment Tool (SWAT) to simulate streamflow, sediment loads and transport, as well as in-stream organic carbon processes for a historical period prior to wildfire. The calibrated model parameters were then modified based on literature values and burn severity maps to represent post-fire conditions of the three large wildfires. The parameter adjustments for simulating wildfire will be validated with post-fire water quality field samples from the wildfires. We will present estimations of future water quality impacts in the burned watersheds under different precipitation conditions at a daily scale for the first year following the wildfires, which will provide testable hypotheses. Additionally, we will determine catchment characteristics most critical in determining the post-fire water quality response. This work will help predict the magnitude of effects from these historic wildfires, which can inform forest and drinking water management decision making.</p>

Download Full-text

Improving water age estimation in a drinking water distribution network by field study and digital modeling

10.5194/egusphere-egu21-14741 ◽

2021 ◽

Author(s):

Jon Kristian Rakstang ◽

Michael B. Waak ◽

Marius M. Rokstad ◽

Cynthia Hallé

Keyword(s):

Water Quality ◽

Drinking Water ◽

Network Model ◽

Age Estimation ◽

Water Distribution ◽

Distribution Network ◽

Distribution Networks ◽

Plate Count ◽

Water Age ◽

Drinking Water Distribution

<p>Municipal drinking water distribution networks are complex and dynamic systems often spanning many hundreds of kilometers and serving thousands of consumers. Degradation of water quality within a distribution network can be associated to water age (i.e., time elapsed after treatment). Norwegian distribution networks often consist of an intricate combination of pressure zones, in which the transport path(s) between source and consumer is not easily ascertained. Water age is therefore poorly understood in many Norwegian distribution networks. In this study, simulations obtained from a water network model were used to estimate water age in a Norwegian municipal distribution network. A full-scale tracer study using sodium chloride salt was conducted to assess simulation accuracy. Water conductivity provided empirical estimates of salt arrival time at five monitoring stations. These estimates were consistently higher than simulated peak arrival times. Nevertheless, empirical and simulated water age correlated well, indicating that additional network model calibration will improve accuracy. Subsequently, simulated mean water age also correlated strongly with heterotrophic plate count (HPC) monitoring data from the distribution network (Pearson&#8217;s R= 0.78, P= 0.00046), indicating biomass accumulation during distribution&#8212;perhaps due to bacterial growth or biofilm interactions&#8212;and illustrating the importance of water age for water quality. This study demonstrates that Norwegian network models can be calibrated with simple and cost-effective salt tracer studies to improve water age estimates. Improved water age estimation will increase our understanding of water quality dynamics in distribution networks. This can, through digital tools, be used to monitor and control water age, and its impact on biogrowth in the network.</p>

Download Full-text

Natural organic matter removal by ion exchange at different positions in the drinking water treatment lane

Drinking Water Engineering and Science ◽

10.5194/dwes-6-1-2013 ◽

2013 ◽

Vol 6 (1) ◽

pp. 1-10 ◽

Cited By ~ 29

Author(s):

A. Grefte ◽

M. Dignum ◽

E. R. Cornelissen ◽

L. C. Rietveld

Keyword(s):

Water Quality ◽

Drinking Water ◽

Organic Matter ◽

Water Treatment ◽

Organic Carbon ◽

Natural Organic Matter ◽

Drinking Water Treatment ◽

Biological Stability ◽

Sand Filtration ◽

Slow Sand Filtration

Abstract. To guarantee a good water quality at the customers tap, natural organic matter (NOM) should be (partly) removed during drinking water treatment. The objective of this research was to improve the biological stability of the produced water by incorporating anion exchange (IEX) for NOM removal. Different placement positions of IEX in the treatment lane (IEX positioned before coagulation, before ozonation or after slow sand filtration) and two IEX configurations (MIEX® and fluidized IEX (FIX)) were compared on water quality as well as costs. For this purpose the pre-treatment plant at Loenderveen and production plant Weesperkarspel of Waternet were used as a case study. Both, MIEX® and FIX were able to remove NOM (mainly the HS fraction) to a high extent. NOM removal can be done efficiently before ozonation and after slow sand filtration. The biological stability, in terms of assimilable organic carbon, biofilm formation rate and dissolved organic carbon, was improved by incorporating IEX for NOM removal. The operational costs were assumed to be directly dependent of the NOM removal rate and determined the difference between the IEX positions. The total costs for IEX for the three positions were approximately equal (0.0631 € m−3), however the savings on following treatment processes caused a cost reduction for the IEX positions before coagulation and before ozonation compared to IEX positioned after slow sand filtration. IEX positioned before ozonation was most cost effective and improved the biological stability of the treated water.

Download Full-text

Impacts of temperature alteration on the drinking water quality stored in plastic bottles

Applied Water Science ◽

10.1007/s13201-021-01505-2 ◽

2021 ◽

Vol 11 (10) ◽

Author(s):

Abdelkader T. Ahmed ◽

Mohammed Emad ◽

Mohammed A. Bkary

Keyword(s):

Water Quality ◽

Drinking Water ◽

Tap Water ◽

Research Work ◽

Bottled Water ◽

Physiochemical Parameters ◽

Heating Water ◽

Long Time ◽

The Impact ◽

Concentration Levels

AbstractMany people prefer to drink bottled water instead off the tap water. The bottled water is stored in the plastic bottles sometimes for long time. These plastic bottles might leach out some harmful materials into the water especially when exposed to temperature alteration, which may affect human health. This research work focused on investigating the effect of changing temperature on the bottled water quality. The work studied the effect of heating water in plastic bottles by sun, oven, and microwave. The study included also the impact of cooling and freezing the bottled waters. Results showed that temperature alterations caused changes in some physicochemical properties of bottled waters such as decreasing the values of pH and TDS and increasing levels of fluoride and chloride. In addition, the concentration levels of some physiochemical parameters exceeded the permissible values for drinking water. With temperature alterations, all levels of heavy metals in bottled waters were minimal except some small concentrations of copper and zinc. Results confirmed also differences in behavior between the bottled water brands exposed to the same temperature alterations. Heating bottled waters above 50 °C is alarming problem on the water quality. This is because above this degree, many alternations were observed in the water content. The outcomes of this work are useful for improving the current legislation on bottled waters and their storage.

Download Full-text

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.

Download Full-text

Small-scale drinking water treatment unit of filtration and UV disinfection for remote area

Water Science & Technology Water Supply ◽

10.2166/ws.2020.109 ◽

2020 ◽

Vol 20 (6) ◽

pp. 2106-2118

Author(s):

Kassim Chabi ◽

Jie Zeng ◽

Lizheng Guo ◽

Xi Li ◽

Chengsong Ye ◽

...

Keyword(s):

Water Quality ◽

Drinking Water ◽

Water Treatment ◽

Organic Carbon ◽

Dissolved Organic Carbon ◽

Bacterial Community Composition ◽

Drinking Water Treatment ◽

Small Scale ◽

Treatment Unit ◽

Remote Areas

Abstract People in remote areas are still drinking surface water that may contain certain pollutants including harmful microorganisms and chemical compounds directly without any pretreatment. In this study, we have designed and operated a pilot-scale drinking water treatment unit as part of our aim to find an economic and easily operable technology for providing drinking water to people in those areas. Our small-scale treatment unit contains filtration and disinfection (UV–C irradiation) stages to remove pollutants from source water. The water quality index was determined based on various parameters such as pH, temperature, dissolved oxygen, nitrate, nitrite, ammonium, phosphorus, dissolved organic carbon and bacteria. Water and media samples after DNA extraction were sequenced using Illumina MiSeq throughput sequencing for the determination of bacterial community composition. After the raw water treatment, the reduction of bacteria concentration ranged from 1 to 2 log10. The average removal of the turbidity, ammonium, nitrite, phosphorus and dissolved organic carbon reached up to 95.33%, 85.71%, 100%, 28.57%, and 45%, respectively. In conclusion, multiple biological stages in our designed unit showed an improvement of the drinking water quality. The designed drinking treatment unit produces potable water meeting standards at a lower cost of operation and it can be used in remote areas.

Download Full-text