Evaluation and monitoring of the water quality of an Argentinian urban river applying multivariate statistics

In this work, we present the water quality assessment of an urban river, the San Luis River, located in San Luis Province, Argentina. The San Luis River flows through two developing cities; hence, urban anthropic activities affect its water quality. The river was sampled spatially and temporally, evaluating ten physicochemical variables on each water sample. These data were used to calculate a Simplified Index of Water Quality in order to estimate river water quality and infer possible contamination sources. Data were statistically analyzed with the opensource software R, 4.1.0 version. Principal component analysis, cluster analysis, correlation matrices, and heatmap analysis were performed. Results indicated that water quality decreases in areas where anthropogenic activities take place. Robust inferential statistical analysis was performed, employing an alternative of multivariate analysis of variance (MANOVA), MANOVA.wide function. The most statistically relevant physicochemical variables associated with water quality decrease were used to develop a multiple linear regression model to estimate organic matter, reducing the variables necessary for continuous monitoring of the river and, hence, reducing costs. Given the limited information available in the region about the characteristics and recovery of this specific river category, the model developed is of vital importance since it can quickly detect anthropic alterations and contribute to the environmental management of the rivers. This model was also used to estimate organic matter at sites located in other similar rivers, obtaining satisfactory results.

Legionella and other opportunistic pathogens in full-scale chloraminated municipal drinking water distribution systems

Water-based opportunistic pathogens (OPs) are a leading cause of drinking-water-related disease outbreaks, especially in developed countries such as the United States (US). Physicochemical water quality parameters, especially disinfectant residuals, control the (re)growth, presence, colonization, and concentrations of OPs in drinking water distribution systems (DWDSs), while the relationship between OPs and those parameters remain unclear. This study aimed to quantify how physicochemical parameters, mainly monochloramine residual concentration, hydraulic residence time (HRT), and seasonality, affected the occurrence and concentrations of four common OPs (Legionella, Mycobacterium, Pseudomonas, and Vermamoeba vermiformis) in four full-scale DWDSs in the US. Legionella as a dominant OP occurred in 93.8% of the 64 sampling events and had a mean density of 4.27 × 105 genome copies per liter. Legionella positively correlated with Mycobacterium, Pseudomonas, and total bacteria. Multiple regression with data from the four DWDSs showed that Legionella had significant correlations with total chlorine residual level, free ammonia concentration, and trihalomethane concentration. Therefore, Legionella is a promising indicator of water-based OPs, reflecting microbial water quality in chloraminated DWDSs. The OP concentrations had strong seasonal variations and peaked in winter and/or spring possibly because of reduced water usage (i.e., increased water stagnation or HRT) during cold seasons. The OP concentrations generally increased with HRT presumably because of disinfectant residual decay, indicating the importance of well-maintaining disinfectant residuals in DWDSs for OP control. The concentrations of Mycobacterium, Pseudomonas, and V. vermiformis were significantly associated with total chlorine residual concentration, free ammonia concentration, and pH and trihalomethane concentration, respectively. Overall, this study demonstrates how the significant spatiotemporal variations of OP concentrations in chloraminated DWDSs correlated with critical physicochemical water quality parameters such as disinfectant residual levels. This work also indicates that Legionella is a promising indicator of OPs and microbial water quality in chloraminated DWDSs.

Nitrification in Premise Plumbing: A Review

Nitrification is a major issue that utilities must address if they utilize chloramines as a secondary disinfectant. Nitrification is the oxidation of free ammonia to nitrite which is then further oxidized to nitrate. Free ammonia is found in drinking water systems as a result of overfeeding at the water treatment plant (WTP) or as a result of the decomposition of monochloramine. Premise plumbing systems (i.e., the plumbing systems within buildings and homes) are characterized by irregular usage patterns, high water age, high temperature, and high surface-to-volume ratios. These characteristics create ideal conditions for increased chloramine decay, bacterial growth, and nitrification. This review discusses factors within premise plumbing that are likely to influence nitrification, and vice versa. Factors influencing, or influenced by, nitrification include the rate at which chloramine residual decays, microbial regrowth, corrosion of pipe materials, and water conservation practices. From a regulatory standpoint, the greatest impact of nitrification within premise plumbing is likely to be a result of increased lead levels during Lead and Copper Rule (LCR) sampling. Other drinking water regulations related to nitrifying parameters are monitored in a manner to reduce premise plumbing impacts. One way to potentially control nitrification in premise plumbing systems is through the development of building management plans.

Effects of environmental storage conditions on survival of indicator organisms in a blend of surface water and dual disinfected reclaimed water

AIMS

The purpose of this study was to evaluate the effects of temperature, mixing and sunlight exposure on the 5-day survival of Escherichia coli, Enterococcus sp., F+/male-specific coliphages, somatic coliphages and Clostridium perfringens spores in an 80/20 blend of surface water and reclaimed water approved for potable reuse in North Carolina.

METHODS AND RESULTS

Grab samples of tertiary treated, dual disinfected North Carolina 'Type 2' reclaimed water were collected and mixed with ambient surface waters to create the 80/20 mix and then spiked with naturally occurring organisms present in the blended water or organisms isolated from sewage. Organism survival over the 5-day period was evaluated at 4 and 20°C, 0, 60 and 120 rev min^-1 mixing speeds and exposure to sunlight or darkness. The log₁₀ survival ratio was then calculated for each organism at each condition.

CONCLUSIONS

There were measurable differences between the log₁₀ survival ratios at 5 days for most organisms; indicating that storage can decrease microbial concentrations. Mixing conditions were not a significant factor in microbe survival over the 5-day storage period. Sunlight was the most effective treatment factor to decrease log₁₀ survival during 5-day storage.

SIGNIFICANCE AND IMPACT OF THE STUDY

No previous studies have evaluated the survival of micro-organisms in the NC approved 80/20 blend of surface and reclaimed water over the 5-day storage. This study provides the first results on the survival of regulated faecal indicator organisms stored for 5 days in blended water under different environmental conditions.

The effect of sodium thiosulfate dechlorination on fecal indicator bacteria enumeration: laboratory and field data

In microbiological water quality testing, sample dechlorination with sodium thiosulfate is recommended to ensure that results accurately reflect the water quality at sample collection. Nevertheless, monitoring institutions in low-resource settings do not always dechlorinate samples, and there is limited research describing how this practice impacts drinking water quality results. The effect of dechlorination on indicator bacteria counts was evaluated by spiking laboratory water with five Escherichia coli (E. coli) concentrations (10⁴-10⁸ CFU/100 mL), chlorinating at six doses (0-0.6 mg/L), holding samples with and without sodium thiosulfate for 5-7 hours, and enumerating E. coli by membrane filtration with m-lauryl sulfate media. Additionally, sub-Saharan African water suppliers enumerated thermotolerant coliform by membrane filtration in paired chlorinated water samples collected with and without sodium thiosulfate. Across all E. coli and chlorine doses in the laboratory, and all field tests, samples held without sodium thiosulfate had lower bacteria counts (p < 0.001). Additionally, chlorinated water supply samples held without sodium thiosulfate had an 87.5% false negative rate. Results indicate the importance of dechlorinating microbiological water quality samples, discarding data from chlorinated samples collected without dechlorination, and reinforcing dechlorination recommendations in resource-limited environments to improve water safety management.

Estimating the number of cases of acute gastrointestinal illness (AGI) associated with Canadian municipal drinking water systems

The estimated burden of endemic acute gastrointestinal illness (AGI) annually in Canada is 20·5 million cases. Approximately 4 million of these cases are domestically acquired and foodborne, yet the proportion of waterborne cases is unknown. A number of randomized controlled trials have been completed to estimate the influence of tap water from municipal drinking water plants on the burden of AGI. In Canada, 83% of the population (28 521 761 people) consumes tap water from municipal drinking water plants serving >1000 people. The drinking water-related AGI burden associated with the consumption of water from these systems in Canada is unknown. The objective of this research was to estimate the number of AGI cases attributable to consumption of drinking water from large municipal water supplies in Canada, using data from four household drinking water intervention trials. Canadian municipal water treatment systems were ranked into four categories based on source water type and quality, population size served, and treatment capability and barriers. The water treatment plants studied in the four household drinking water intervention trials were also ranked according to the aforementioned criteria, and the Canadian treatment plants were then scored against these criteria to develop four AGI risk groups. The proportion of illnesses attributed to distribution system events vs. source water quality/treatment failures was also estimated, to inform the focus of future intervention efforts. It is estimated that 334 966 cases (90% probability interval 183 006-501 026) of AGI per year are associated with the consumption of tap water from municipal systems that serve >1000 people in Canada. This study provides a framework for estimating the burden of waterborne illness at a national level and identifying existing knowledge gaps for future research and surveillance efforts, in Canada and abroad.

Microbiological and Chemical Quality of Packaged Sachet Water and Household Stored Drinking Water in Freetown, Sierra Leone

Packaged drinking water (PW) sold in bottles and plastic bags/sachets is widely consumed in low- and middle-income countries (LMICs), and many urban users in sub-Saharan Africa (SSA) rely on packaged sachet water (PSW) as their primary source of water for consumption. However, few rigorous studies have investigated PSW quality in SSA, and none have compared PSW to stored household water for consumption (HWC). A clearer understanding of PSW quality in the context of alternative sources is needed to inform policy and regulation. As elsewhere in SSA, PSW is widely consumed in Sierra Leone, but government oversight is nearly nonexistent. This study examined the microbiological and chemical quality of a representative sample of PSW products in Freetown, Sierra Leone at packaged water manufacturing facilities (PWMFs) and at points of sale (POSs). Samples of HWC were also analyzed for comparison. The study did not find evidence of serious chemical contamination among the parameters studied. However, 19% of 45 PSW products sampled at the PWMF contained detectable Escherichia coli (EC), although only two samples exceeded 10 CFU/100 mL. Concentrations of total coliforms (TC) in PSW (but not EC) increased along the supply chain. Samples of HWC from 60 households in Freetown were significantly more likely to contain EC and TC than PSW at the point of production (p<0.01), and had significantly higher concentrations of both bacterial indicators (p<0.01). These results highlight the need for additional PSW regulation and surveillance, while demonstrating the need to prioritize the safety of HWC. At present, PSW may be the least unsafe option for many households.

Biofouling on polymeric heat exchanger surfaces with E. coli and native biofilms

The biofouling affinity of different polymeric surfaces (polypropylene, polysulfone, polyethylene terephthalate, and polyether ether ketone) in comparison to stainless steel (SS) was studied for the model bacterium Escherichia coli K12 DSM 498 and native biofilms originating from Rhine water. The biofilm mass deposited on the polymer surfaces was minimized by several magnitudes compared to SS. The cell count and the accumulated biomass of E. coli on the polymer surfaces showed an opposing linear trend. The promising low biofilm formation on the polymers is attributed to the combination of inherent surface properties (roughness, surface energy and hydrophobicity) when compared to SS. The fouling characteristics of E. coli biofilms show good conformity with the more complex native biofilms investigated. The results can be utilized for the development of new polymer heat exchangers when using untreated river water as coolant or for other processes needing antifouling materials.

Real-time ArcGIS and heterotrophic plate count based chloramine disinfectant control in water distribution system

This study investigates the effect of chloramine residual on bacteria growth and regrowth and the relationship between heterotrophic plate counts (HPCs) and the concentration of chloramine residual in the Shanghai drinking water distribution system (DWDS). In this study, models to control HPCs in the water distribution system and consumer taps are also developed. Real-time ArcGIS was applied to show the distribution and changed results of the chloramine residual concentration in the pipe system by using these models. Residual regression analysis was used to get a reasonable range of the threshold values that allows the chloramine residual to efficiently inhibit bacteria growth in the Shanghai DWDS; the threshold values should be between 0.45 and 0.5 mg/L in pipe water and 0.2 and 0.25 mg/L in tap water. The low residual chloramine value (0.05 mg/L) of the Chinese drinking water quality standard may pose a potential health risk for microorganisms that should be improved. Disinfection by-products (DBPs) were detected, but no health risk was identified.

Using coagulation to restrict microbial re-growth in tap water by phosphate limitation in water treatment

Extensive microbial re-growth in a drinking water distribution system can deteriorate water quality. The limiting factor for microbial re-growth in a tap water produced by a conventional drinking water treatment plant in China was identified by determining the microbial re-growth potential (MRP) by adding different nutrients to stimulate growth of a natural microbial consortium as inoculum and flow-cytometric enumeration. No obvious change of MRP was found in tap water after addition of carbon, whereas, a 1- to 2-fold increase of MRP was observed after addition of phosphate (P). This clearly demonstrated that microbial re-growth in this tap water was limited by P. Most of the re-grown microbial flora (>85%) consisted of high nucleic acid content cells. A subsequent investigation of the MRP in the actual water treatment plant demonstrated that coagulation was the crucial step for decreasing MRP and producing P-limited water. Therefore, a comparison concerning the control of MRP by three different coagulants was conducted. It showed that all the three coagulants efficiently reduced the MRP and shifted the limitation regime from C to P, but the required dose was different. The study shows that it is feasible to restrict microbial re-growth by P limitation using coagulation in water treatment.

Biostability in distribution systems in one city in southern China: characteristics, modeling and control strategy

This study investigated the bacterial regrowth in drinking water distribution systems receiving finished water from an advanced drinking water treatment plant in one city in southern China. Thirteen nodes in two water supply zones with different aged pipelines were selected to monitor water temperature, dissolved oxygen (DO), chloramine residual, assimilable organic carbon (AOC), and heterotrophic plate counts (HPC). Regression and principal component analyses indicated that HPC had a strong correlation with chloramine residual. Based on Chick-Watson's Law and the Monod equation, biostability curves under different conditions were developed to achieve the goal of HPC < or = 100 CFU/mL. The biostability curves could interpret the scenario under various AOC concentrations and predict the required chloramine residual concentration under the condition of high AOC level. The simulation was also carried out to predict the scenario with a stricter HPC goal (< or = 50 CFU/mL) and determine the required chloramine residual. The biological regrowth control strategy was assessed using biostability curve analysis. The results indicated that maintaining high chloramine residual concentration was the most practical way to achieve the goal of HPC < or = 100 CFU/mL. Biostability curves could be a very useful tool for biostability control in distribution systems. This work could provide some new insights towards biostability control in real distribution systems.

Water quality indicators: bacteria, coliphages, enteric viruses

Water quality through the presence of pathogenic enteric microorganisms may affect human health. Coliform bacteria, Escherichia coli and coliphages are normally used as indicators of water quality. However, the presence of above-mentioned indicators do not always suggest the presence of human enteric viruses. It is important to study human enteric viruses in water. Human enteric viruses can tolerate fluctuating environmental conditions and survive in the environment for long periods of time becoming causal agents of diarrhoeal diseases. Therefore, the potential of human pathogenic viruses as significant indicators of water quality is emerging. Human Adenoviruses and other viruses have been proposed as suitable indices for the effective identification of such organisms of human origin contaminating water systems. This article reports on the recent developments in the management of water quality specifically focusing on human enteric viruses as indicators.

Seasonal dynamics of bacterial community structure and composition in cold and hot drinking water derived from surface water reservoirs

In temperate regions, seasonal variability of environmental factors affects the bacterial community in source water and finished drinking water. Therefore, the bacterial core community and its seasonal variability in cold and the respective hot drinking water was investigated. The bacterial core community was studied by 16S rRNA-based SSCP fingerprint analyses and band sequencing of DNA and RNA extracts of cold and hot water (60 °C). The bacterial communities of cold and hot drinking water showed a highly different structure and phylogenetic composition both for RNA and DNA extracts. For cold drinking water substantial seasonal dynamics of the bacterial community was observed related to environmental factors such as temperature and precipitation affecting source and drinking water. Phylogenetic analyses of the cold water community indicated that the majority of phylotypes were very closely affiliated with those detected in former studies of the same drinking water supply system (DWSS) in the preceding 6 years, indicating a high stability over time. The hot water community was very stable over time and seasons and highly distinct from the cold water with respect to structure and composition. The hot water community displayed a lower diversity and its phylotypes were mostly affiliated with bacteria of high temperature habitats with high growth rates indicated by their high RNA content. The conversion of the cold to the hot water bacterial community is considered as occurring within a few hours by the following two processes, i) by decay of most of the cold water bacteria due to heating, and ii) rapid growth of the high temperature adapted bacteria present in the hot water (co-heated with the cold water in the same device) using the nutrients released from the decaying cold water bacteria. The high temperature adapted bacteria originated partially from low abundant but beforehand detected members of the cold water; additionally, the rare members ("seed bank ") of the cold water are considered as a source.

Coliform Sources and Mechanisms for Regrowth in Household Drinking Water in Limpopo, South Africa

Resource-limited communities throughout the developing world face significant environmental health problems related to the myriad of coliform sources within those communities. This study comprehensively investigated contamination sources and the biological and chemical mechanisms sustaining them in two adjacent communities in rural Limpopo, South Africa. An 8-month study was conducted of household (n = 14) and source water quality, measurements of biofilm layers on the inside of household water storage containers and water transfer devices, and also hand-based coliforms and hand-washing effectiveness. A 7-day water container incubation experiment was also performed to determine the biological and chemical changes that occur in a household water storage container independent of human interference. Results indicate that household drinking water frequently becomes contaminated after collection but before consumption (197 versus 1,046 colony-forming units/100 mL; n = 266; p < 0.001). The most important contamination sources include biofilm layers on the inside of storage containers (1.85 ± 1.59 colony-forming units/cm²; n = 44), hands (5,097 ± 2,125 colony-forming units/hand; n = 48), and coliform regrowth resulting from high assimilable organic carbon (AOC) levels during storage. A maximum specific growth rate, μ_max, of 0.072 ± 0.003 h^-1 was determined for total coliform bacteria on AOC, and a high correlation between AOC concentrations and the growth potential of total coliform bacteria was observed. These results support the implementation of point-of-use water treatment and other interventions aimed at maintaining the safe water chain and preventing biological regrowth.

Asellus aquaticus as a potential carrier of Escherichia coli and other coliform bacteria into drinking water distribution systems

Individuals of the water louse, Asellus aquaticus, enter drinking water distribution systems in temperate parts of the world, where they establish breeding populations. We analysed populations of surface water A. aquaticus from two ponds for associated faecal indicator bacteria and assessed the risk of A. aquaticus transporting bacteria into distribution systems. Concentrations of up to two E. coli and five total coliforms·mL-1 were measured in the water and 200 E. coli and >240 total coliforms·mL-1 in the sediments of the investigated ponds. Concentrations of A. aquaticus associated bacteria never exceeded three E. coli and six total coliforms·A. aquaticus-1. During exposure to high concentrations of coliforms, concentrations reached 350 coliforms·A. aquaticus-1. A. aquaticus associated E. coli were only detected as long as E. coli were present in the water and sediment. The calculated probability of exceeding drinking water guideline values in non-disinfected systems by intrusion of A. aquaticus was low. Only in scenarios with narrow pipes and low flows, did total coliforms exceed guideline values, implying that the probability of detection by routine monitoring is also low. The study expands the knowledge base for evaluating incidents with presence of coliform indicators in drinking water by showing that intruding A. aquaticus were not important carriers of E. coli or other coliform bacteria even when emerging from faecally contaminated waters.

Modeling the complexities of water, hygiene, and health in Limpopo Province, South Africa

Researchers have long studied the causes and prevention strategies of poor household water quality and early childhood diarrhea using intervention-control trials. Although the results of such trails can lead to useful information, they do not capture the complexity of this natural/engineered/social system. We report on the development of an agent-based model (ABM) to study such a system in Limpopo, South Africa. The study is based on four years of field data collection to accurately capture essential elements of the communities and their water contamination chain. An extensive analysis of those elements explored behaviors including water collection and treatment frequency as well as biofilm buildup in water storage containers, source water quality, and water container types. Results indicate that interventions must be optimally implemented in order to see significant reductions in early childhood diarrhea (ECD). Household boiling frequency, source water quality, water container type, and the biofilm layer contribution were deemed to have significant impacts on ECD. Furthermore, concurrently implemented highly effective interventions were shown to reduce diarrhea rates to very low levels even when other, less important practices were suboptimal. This technique can be used by a variety of stakeholders when designing interventions to reduce ECD incidences in similar settings.

Comparing removal of trace organic compounds and assimilable organic carbon (AOC) at advanced and traditional water treatment plants

Stability of drinking water can be indicated by the assimilable organic carbon (AOC). This AOC value represents the regrowth capacity of microorganisms and has large impacts on the quality of drinking water in a distribution system. With respect to the effectiveness of traditional and advanced processing methods in removing trace organic compounds (including TOC, DOC, UV(254), and AOC) from water, experimental results indicate that the removal rate of AOC at the Cheng Ching Lake water treatment plant (which utilizes advanced water treatment processes, and is hereinafter referred to as CCLWTP) is 54%, while the removal rate of AOC at the Gong Yuan water treatment plant (which uses traditional water treatment processes, and is hereinafter referred to as GYWTP) is 36%. In advanced water treatment units, new coagulation-sedimentation processes, rapid filters, and biological activated carbon filters can effectively remove AOC, total organic carbon (TOC), and dissolved organic carbon (DOC). In traditional water treatment units, coagulation-sedimentation processes are most effective in removing AOC. Simulation results and calculations made using the AutoNet method indicate that TOC, TDS, NH(3)-N, and NO(3)-N should be regularly monitored in the CCLWTP, and that TOC, temperature, and NH(3)-N should be regularly monitored in the GYWTP.

Assessment of the efficacy of the first water system for emergency hospital use

OBJECTIVE

The First Water Responder B package water treatment device was evaluated for its ability to reduce the levels of spiked indicators and pathogens (Escherichia coli, MS2 coliphage, murine adenovirus, and Cryptosporidium oocysts) in a surface water to partially evaluate its appropriateness to be used to provide safe drinking water to hospitals during emergency situations.

METHODS

Lake water was collected in 50-L carboys and spiked with selected indicators and pathogens (E coli, MS2 coliphage, murine adenovirus, and Cryptosporidium oocysts) at 2 different spike levels (low and high). This water was treated using the First Water Responder B, and the microorganisms were enumerated before and after treatment using US Environmental Protection Agency and Standard Methods. Microbial removal efficiencies were compared with Environmental Protection Agency guidelines.

RESULTS

E coli spikes ranged from 2.9 to 1059 colony-forming units (CFU)/100 mL with removals to below detection limits (1 CFU/100 mL) to 2.8 CFU/100 mL or 0.98 to 3.5 log(10) reductions. MS2 coliphage spikes ranged from 3 plaque-forming units (PFU) to 837 PFU/100 mL with removals to below detection limits (1 PFU/100 mL) to 11.7 PFU/100 mL or 0.65 to 1.9 log(10) reductions. Murine adenovirus spikes ranged from 203 to 8410 most probable number (MPN) of infectious units/100 mL with removals to below detection limits (23 MPN infectious units/100 mL) to 1370 MPN infectious units/100 mL or 0.79 to >1.2 log(10) reductions. Cryptosporidium parvum oocyst spikes ranged from 52 to 853 oocysts per liter with removals to below detection limits (<1 oocyst per liter) to 0.3 oocysts per liter or >2.2 to 3.4 log(10) reductions.

CONCLUSIONS

Although the First Water system could remove a significant portion of the spiked organisms, it is recommended that this point-of-use system be coupled with chemical disinfection in a multiple-barrier approach to provide water of the highest reasonably achievable quality for hospital use in emergency situations.

Bacteria from drinking water supply and their fate in gastrointestinal tracts of germ-free mice: a phylogenetic comparison study

Microorganisms in drinking water sources may colonize in gastrointestinal (GI) tracts and this phenomenon may pose a potential health risk especially to immunocompromised population. The microbial community diversity of the drinking water was compared with the GI tracts of the mice using phylogenetic and statistical analyses of 16S rRNA gene sequences. A group of germ-free mice were fed with drinking water from public water supply that passed through an automated watering system with documented biofilm accumulation. From drinking water and GI tracts of the germ-free mice, 179 bacteria were isolated and 75 unique 16S rRNA gene phylotypes were sequenced as operational taxonomic unit (OTU, >97% similarity). Three major groups of the genus Acidovorax (21%), Variovorax (42%) and Sphingopyxis (15%) were found in drinking water. Three major groups of the genus Ralstonia (24%), Staphylococcus (20%) and Bosea (22%) were found in GI tracts. Ralstonia (6%, 24%), Sphingopyxis (15%, 2%), Bacillus (3%, 5%), Escherichia coli (3%, 2%) and Mesorhizobium (3%, 5%) were found in both sources - drinking water and GI tract. A lineage-per-time plot shows that the both bacterial communities have convex shape lines, suggesting an excess of closely related ecotypes. A significant F(ST) test (0.00000-0.00901) coupled with an insignificant P test (0.07-0.46) implies that the tree contained several clades of closely related bacteria. Both phylogenetic and statistical results suggest a correlation between the bacterial communities originating in the drinking water and those associated with the GI tracts. The GI tract showed a higher genetic diversity than the drinking water, but a similar lineage-per-time plot was obtained overall. It means a sudden evolutionary transformation and colonization occurred with high selective forces.

Phosphate limitation to control biofouling

Phosphate limitation as a method to control biofouling of spiral wound reverse osmosis (RO) membranes was studied at a full-scale installation fed with extensively pretreated water. The RO installation is characterized by (i) a low feed channel pressure drop increase and (ii) low biomass concentrations in membrane elements at the installation feed side. This installation contrasted sharply with installations fed with less extensively pretreated feed water (and therefore higher phosphate concentrations) experiencing a high-pressure drop increase and high biomass concentrations in lead elements. Membrane fouling simulator (MFS) studies showed that low phosphate concentrations (approximately 0.3 microg P L(-1)) in the feed water restricted the pressure drop increase and biomass accumulation, even at high substrate (organic carbon) concentrations. In the MFS under ortho-phosphate limiting conditions, dosing phosphonate based antiscalants caused biofouling while no biofouling was observed when acids or phosphonate-free antiscalants were used. Antiscalant dosage could increase both phosphate and substrate concentrations of the water. Therefore, antiscalant selection may be critical for biofouling control. Since no biofouling was observed at low phosphate concentrations, restricting biomass growth by phosphate limitation may be a feasible approach to control biofouling, even in the presence of high organic carbon levels.

Particle properties in granular activated carbon filter during drinking water treatment

The elemental composition and bacteria attached in particles were investigated during granular activated carbon (GAC) filtration. The experimental results showed that trapped influent particles could form new, larger particles on GAC surface. The sloughing of individuals off GAC surface caused an increase in effluent particles in the size range from 5 to 25 tm. The selectivity for element removal in GAC filters caused an increasing proportion of metallic elements in the effluent particles. The distribution of molar ratio indicated a complicated composition for large particles, involving organic and inorganic substances. The organic proportion accounted for 40% of total carbon attached to the particles. Compared with dissolved carbon, there was potential for the formation of trihalomethanes by organic carbon attached to particles, especially for those with size larger than 10 im. The pure carbon energy spectrum was found only in the GAC effluent and the size distribution of carbon fines was mainly above 10 microm. The larger carbon fines provided more space for bacterial colonization and stronger protection for attached bacteria against disinfection. The residual attached bacteria after chorine disinfection was increased to 10(2)-l0(3) CFU/mL within 24 hours at 25 degrees C.

Development and application of a bioluminescence-based test for assimilable organic carbon in reclaimed waters

Assimilable organic carbon (AOC) is an important parameter governing the growth of heterotrophic bacteria in drinking water. Despite the recognition that variations in treatment practices (e.g., disinfection, coagulation, selection of filter media, and watershed protection) can have dramatic impacts on AOC levels in drinking water, few water utilities routinely measure AOC levels because of the difficulty of the method. To simplify the method, the Pseudomonas fluorescens P-17 and Spirillum sp. strain NOX test bacteria were mutagenized by using luxCDABE operon fusion and inducible transposons to produce bioluminescent strains. The growth of these strains can easily be monitored with a programmable luminometer to determine the maximum cell yield via luminescence readings, and these values can be fitted to the classical Monod growth curve to determine bacterial growth kinetics and the maximum growth rate. Standard curves using acetate carbon (at concentrations ranging from 0 to 1,000 microg/liter) resulted in coefficients of determination (r(2)) between luminescence units and acetate carbon levels of 0.95 for P-17 and 0.89 for NOX. The bioluminescence test was used to monitor reclaimed water, in which average AOC levels range between 150 and 1,400 microg/liter acetate carbon equivalents. Comparison of the conventional AOC assay and the bioluminescent assay produced an r(2) of 0.92.

Sequential UV- and chlorine-based disinfection to mitigate Escherichia coli in drinking water biofilms

This study was designed to examine the potential downstream benefits of sequential disinfection to control the persistence of Escherichia coli under conditions relevant to drinking water distribution systems. Eight annular reactors (four polycarbonate and four cast iron) were setup in parallel to address various factors that could influence biofilm growth in distribution systems. Eight reactors were treated with chlorine, chlorine dioxide and monochloramine alone or in combination with UV to examine the effects on Escherichia coli growth and persistence in both the effluent and biofilm. In general, UV-treated systems in combination with chlorine or chlorine dioxide and monochloramine achieved greater log reductions in both effluent and biofilm than systems treated with chlorine-based disinfectants alone. However, during UV-low chlorine disinfection, E. coli was found to persist at low levels, suggesting that the UV treatment had instigated an adaptive mutation. During UV-chlorine-dioxide treatment, the E. coli that was initially below the detection limit reappeared during a low level of disinfection (0.2 mg/L) in the cast iron systems. Chloramine was shown to be effective in disinfecting suspended E. coli in the effluent but was unable to reduce biofilm counts to below the detection limit. Issues such as repair mechanism of E. coli and nitrification could help explain some of these aberrations. Improved understanding of the ability of chlorine-based disinfectant in combination with UV to provide sufficient disinfection will ultimately effect in improved management and safety of drinking water.

Monitoring source water for microbial contamination: evaluation of water quality measures

Watershed management programs often rely on monitoring for a large number of water quality parameters to define contaminant issues. While coliforms have traditionally been used to identify microbial contamination, these indicators cannot discriminate among potential contaminant sources. Microbial source tracking (MST) can provide the missing link that implicates the sources of contamination. The objective of this study was to use a weight-of-evidence approach (land use analysis using GIS, sanitary surveys, traditional water quality monitoring, and MST targets) to identify sources of pollution within a watershed that contains a raw drinking water source. For the study watersheds, statistical analyses demonstrated that one measure each of particulate matter (turbidity, particle counts), organic matter (total organic carbon, dissolved organic carbon, UV(254) absorbance), and indicator organisms (fecal coliforms, enterococci) were adequate for characterizing water quality. While these traditional parameters were useful for assessing overall water quality, they were not intended to differentiate between microbial sources at different locations. In contrast, the MST targets utilized (Rhodococcus coprophilus, sorbitol-fermenting Bifidobacteria, and male-specific coliphages) pinpointed specific sources of microbial pollution. However, these targets could not be used for routine monitoring due to a high percentage of non-detects.

Characterization of bacterial coliform occurrences in different zones of a drinking water distribution system

AIMS

To compare the bacterial coliforms detected from occurrences in three zones of a water distribution system supplied by two separate water sources.

METHODS AND RESULTS

Conventional and standardized protocols for identifying enterobacterial populations were applied. Additional tests to confirm isolates were included. Analyses of diversity and population similarity were performed using the Phene Plate System, a miniaturized biochemical phenotyping method. Isolates were identified by the API 20E system in tandem with biochemical phenotyping. A total of 16 576 samples were taken from the water distribution system, with 1416 isolates analysed. A low number of coliform occurrences were observed (2%). Escherichia coli was not detected in either water origin or in Zone 2 samples; however, in Zones 1 and 3 a low number of cases of E. coli were recorded. The percentages of E. coli depended on the identification criteria. Eight biochemical profiles for coliform populations were defined according to the results of the confirmative tests. There was a high diversity among these populations in the three zones studied, although no significant variations in their composition (associated with occurrences in the different zones) were observed. Klebsiella oxytoca was the most commonly detected species irrespective of zone, although seven other enterobacterial genera were also found.

CONCLUSIONS

Analysis of the enzymatic activity of beta-glucuronidase or application of the criteria established in the norm ISO 9308-1, in tandem with thermotolerance was needed to evaluate the occurrence of E. coli in the distribution systems. Detected occurrences of bacterial coliforms could be associated with re-growth patterns for specific sampling points in the distribution system. Seasonal differences, independent of the studied zones, were observed.

SIGNIFICANCE AND IMPACT OF THE STUDY

Biochemical phenotyping of bacterial coliforms was shown to be a useful method on the characterization of occurrences in water distribution systems.

Accumulation and fate of green fluorescent labeled Escherichia coli in laboratory-scale drinking water biofilters

Biological filters combining microbial activity and rapid sand filtration are used in drinking water treatment plants for enhanced biodegradable organic matters (BOM) removal. Biofilms formed on filter media comprised of bacteria enclosed in a polymeric matrix are responsible for the adsorption of BOM and attachment of planktonic microorganisms. This study investigated the removal of Escherichia coli cells injected into laboratory-scale biofilters and the role of biofilm in retaining the injected E. coli. Green fluorescent protein was used as a specific marker to detect and quantify E. coli in the biofilms. About 35% of the total injected E. coli cells were observed in the filter effluents, when initial cell concentrations were measured at 7.4 x 10(6) CFU/mL and 1.6 x 10(7) CFU/mL in two separate experiments. The results from real-time PCR and plate count analysis indicated that 95% of the E. coli retained inside the filters were either non-viable or could not be recovered by colony counting techniques. Injected cells were unevenly distributed inside the filter with more than 70% located at the top 1/5 of the filter. Images obtained from an epifluorescent microscope showed that E. coli cells were embedded inside the biofilm matrix and presented mainly as microcolonies intertwined with other microorganisms, which was consistent with findings from standard plate count methods and qPCR.

Composition and dynamics of bacterial communities of a drinking water supply system as assessed by RNA- and DNA-based 16S rRNA gene fingerprinting

Bacterial community dynamics of a whole drinking water supply system (DWSS) were studied from source to tap. Raw water for this DWSS is provided by two reservoirs with different water characteristics in the Harz mountains of Northern Germany. Samples were taken after different steps of treatment of raw water (i.e., flocculation, sand filtration, and chlorination) and at different points along the supply system to the tap. RNA and DNA were extracted from the sampled water. The 16S rRNA or its genes were partially amplified by reverse transcription-PCR or PCR and analyzed by single-strand conformation polymorphism community fingerprints. The bacterial community structures of the raw water samples from the two reservoirs were very different, but no major changes of these structures occurred after flocculation and sand filtration. Chlorination of the processed raw water strongly affected bacterial community structure, as reflected by the RNA-based fingerprints. This effect was less pronounced for the DNA-based fingerprints. After chlorination, the bacterial community remained rather constant from the storage containers to the tap. Furthermore, the community structure of the tap water did not change substantially for several months. Community composition was assessed by sequencing of abundant bands and phylogenetic analysis of the sequences obtained. The taxonomic compositions of the bacterial communities from both reservoirs were very different at the species level due to their different limnologies. On the other hand, major taxonomic groups, well known to occur in freshwater, such as Alphaproteobacteria, Betaproteobacteria, and Bacteroidetes, were found in both reservoirs. Significant differences in the detection of the major groups were observed between DNA-based and RNA-based fingerprints irrespective of the reservoir. Chlorination of the drinking water seemed to promote growth of nitrifying bacteria. Detailed analysis of the community dynamics of the whole DWSS revealed a significant influence of both source waters on the overall composition of the drinking water microflora and demonstrated the relevance of the raw water microflora for the drinking water microflora provided to the end user.

Advantage provided by iron for Escherichia coli growth and cultivability in drinking water

The presence of iron, used both as a nutrient and as an electron acceptor, was demonstrated to give an advantage to Escherichia coli bacteria in drinking water. Slight additions of ferrous sulfate to water with initial low iron concentrations led to a significant increase in the number of E. coli bacteria. The presence of ferric oxide in water under anaerobic conditions increased bacterial cultivability.

Pipeline materials modify the effectiveness of disinfectants in drinking water distribution systems

We studied how pipe material can modify the effectiveness of UV- and chlorine disinfection in drinking water and biofilms. This study was done with two pipe materials: copper and composite plastic (polyethylene, PE) in a pilot scale water distribution network. UV-disinfection decreased viable bacterial numbers in the pilot waterworks and outlet water of pipes on average by 79%, but in biofilms its disinfecting effect was minor. Chlorine decreased effectively the microbial numbers in water and biofilms of PE pipes. In outlet water from copper pipes, the effect of chlorination was weaker; microbial numbers increased back to the level before chlorination within a few days. In the biofilms present in the copper pipes, chlorine decreased microbial numbers only in front of the pipeline. One reason for weaker efficiency of chlorine in copper pipes was that its concentration declined more rapidly in the copper pipes than in the PE pipes. These results means that copper pipes may require a higher chlorine dosage than plastic pipes to achieve effective disinfection of the pipes.

Coliform culturability in over- versus undersaturated drinking waters

The culturability of Escherichia coli in undersaturated drinking water with respect to CaCO3 (corrosive water) or in oversaturated water (non-corrosive water) was tested in different reactors: glass flasks (batch, "non-reactive" wall); glass reactors (chemostat, "non-reactive" wall) versus a corroded cast iron Propella reactor (chemostat, "reactive" wall) and a 15-year-old distribution system pilot (chemostat, "reactive" wall with 1% corroded cast iron and 99% cement-lined cast iron). The E. coli in E. coli-spiked drinking water was not able to maintain its culturability and colonize the experimental systems. It appears from our results that the optimal pH for maintaining E. coli culturability was around 8.2 or higher. However, in reactors with a reactive wall (corroded cast iron), the decline in E. coli culturability was slower when the pH was adjusted to 7.9 or 7.7 (i.e. a reactor fed with corrosive water; pH<pHs) than in non-corrosive water (pH 8.64 or 8.24; pH>pHs). We tentatively deduce that corrosion products coming from chemical reactions driven by corrosive waters on the pipe wall improve E. coli culturability.

Escherichia coli behavior in the presence of organic matter released by algae exposed to water treatment chemicals

When exposed to oxidation, algae release dissolved organic matter with significant carbohydrate (52%) and biodegradable (55 to 74%) fractions. This study examined whether algal organic matter (AOM) added in drinking water can compromise water biological stability by supporting bacterial survival. Escherichia coli (1.3 x 10(5) cells ml(-1)) was inoculated in sterile dechlorinated tap water supplemented with various qualities of organic substrate, such as the organic matter coming from chlorinated algae, ozonated algae, and acetate (model molecule) to add 0.2 +/- 0.1 mg of biodegradable dissolved organic carbon (BDOC) liter(-1). Despite equivalent levels of BDOC, E. coli behavior depended on the source of the added organic matter. The addition of AOM from chlorinated algae led to an E. coli growth equivalent to that in nonsupplemented tap water; the addition of AOM from ozonated algae allowed a 4- to 12-fold increase in E. coli proliferation compared to nonsupplemented tap water. Under our experimental conditions, 0.1 mg of algal BDOC was sufficient to support E. coli growth, whereas the 0.7 mg of BDOC liter(-1) initially present in drinking water and an additional 0.2 mg of BDOC acetate liter(-1) were not sufficient. Better maintenance of E. coli cultivability was also observed when AOM was added; cultivability was even increased after addition of AOM from ozonated algae. AOM, likely to be present in treatment plants during algal blooms, and thus potentially in the treated water may compromise water biological stability.

Occurrence of nitrifiers and diversity of ammonia-oxidizing bacteria in developing drinking water biofilms

We studied the population dynamics of nitrifying bacteria during the development of biofilms up to 233 or 280 days on polyvinylchloride pipes connected to two full-scale drinking water distribution networks supplying processed and chloraminated surface water. The numbers of nitrifiers in biofilms were enumerated at intervals of 10-64 days by the most probable number (MPN) method at waterworks and at several study sites in distribution network areas. The numbers of nitrifiers increased towards the distal sites. The highest detected MPN counts of ammonia-oxidizing bacteria (AOB) for study areas 1 and 7 were 500 MPN cm(-2) and 1.0 x 10(6) MPN cm(-2), and those of nitrite-oxidizing bacteria (NOB) 96 MPN cm(-2) and 2.2 x 10(3) MPN cm(-2), respectively. The diversity of AOB was determined by PCR amplifying, cloning and sequencing the partial ammonia monooxygenase (amoA) gene of selected biofilm samples presenting different biofilm ages. The PCR primers used, A189 and A682, also amplified a fragment of particulate methane monooxygenase (pmoA) gene of methane-oxidizing bacteria. The majority of biofilm clones (24 out of 30 studied) contained Nitrosomonas amoA-like sequences. There were only two pmoA-like sequences of Type I methanotrophs, and four sequences positioned in amoA/pmoA sequence groups of uncultured bacteria. From both study area very similar or even completely identical Nitrosomonas amoA-like sequences were obtained despite of high difference in AOB numbers. The results show that the conditions in newly formed biofilms in drinking water distribution systems favor the growth of Nitrosomonas-type AOB.

Effects of oxalic acid on the regrowth of heterotrophic bacteria in the distributed drinking water

Three laboratory-scale water pipe systems were set up to study the effects of adding oxalic acid on the bacterial regrowth and biofilm formation in the distributed drinking water. The results of water pipe experiment displayed that around 38% carbon in the oxalic acid could be converted to bacterial biomass. The maximum HPCs in biofilm were equal to 3.5x10(4), 3.38x10(5) and 2.8x10(6) CFUcm(-2) while the maximum HPCs of free bacteria were equal to 1.2x10(3), 2.54x10(3) and 3.78x10(4) CFUml(-1) for the blank and with addition of 10 and 50 micrograms OA eq-Cl(-1), respectively. These results imply that the addition of oxalic acid to distributed water has positive effect on the assimilable organic carbon content of drinking water and bacterial regrowth in water pipe. This effect is enhanced with addition of high-level oxalic acid. Batch tests were also conducted using water samples collected from a Taiwanese drinking water distribution system. The bacterial regrowth potentials (BRPs) of the blank were equal to 4.25x10(3), 1.46x10(4), 4.9x10(4) and 7.54x10(4) CFUml(-1) for water samples collected from treatment plant effluent, commercial area, mixed area, and residential area, respectively. These results show that the biological stability of distributed drinking water is the highest in treatment plant effluent, the moderate in the commercial area and mixed area, and the lowest in the residential area.

Speciation analysis and the occurrence of aluminum turbidity

Determinations of particulate Al (pAl), leachable particulate Al (lpAl), and soluble Al (sAl) along the treatment sequence were used to investigate the occurrence of turbidity at drinking-water plants using aluminum coagulation. The behavior of Al species during filtration was normal when sAl remained at a constant level, while pAl was completely eliminated. When sAl was constant while pAl was not completely eliminated, the presence of residual pAl could be attri buted to problems of filtration effectiveness. When sAl decreased during filtration, the residual pAl could also originate from transformations such as precipitation occurring in the filtration media. When sAl increased, the residual pAl could also originate from precipitate detachments. Increases in sAl during filtration or the presence of partially leachable pAl were associated with deteriorations in residual pAl along filtration runs. The presence of nonleachable pAl denoted the existence of different aluminum forms. This was a supplementary indicator of treatment problems and affected the relationship with turbidity. In addition to demonstrating the occurrence of aluminum turbidity, speciation analysis offered a characterization of turbidity and its origin. By contributing to the evidence as well as the understanding of treatment problems, these speciation methodologies can be useful to minimize aluminum turbidity.

UV disinfection in a model distribution system:; biofilm growth and microbial community

Two model distribution systems were operated in parallel to investigate the impact of UV disinfection on water distribution system biofilms and microbial community composition. One system received an influent irradiated with UV light, whereas the control received the same influent with no treatment. The biofilm in the UV system, as compared to the control, was more responsive (i.e., had a greater increase in steady-state density of heterotrophic bacteria) to the increased nutrient availability afforded by a decrease in HRT from 12 to 2 h. However, the UV treatment did not have a consistent impact on the biofilm community, indicating the processes controlling HPC density were independent of the specific strains of bacteria forming the biofilm. There was evidence that particle shielding contributed to the survival of UV-susceptible bacteria. This hypothesis was consistent with the presence of UV-susceptible bacteria in the UV system, as well as the high similarity of the biofilm communities in the UV and control systems in one of the experiments. To simulate an intrusion event, opportunistic pathogens were added to each system after the biofilm community reached steady-state. Opportunistic pathogen attachment was not affected by the UV treatment, but was instead correlated to the biofilm density of heterotrophic bacteria.

Dynamic simulation of multicomponent reaction transport in water distribution systems

Given the presence of nutrients, regrowth of bacteria within a distribution system is possible. The bacterial growth phenomena, which can be studied by developing a multicomponent (substrate, biomass and disinfectant) reaction transport model, is governed by its relationship with the substrate (organic carbon) and disinfectant (chlorine). The multicomponent reaction transport model developed in the present study utilizes the simplified expressions for the basic processes (in bulk flow and at pipe wall) such as bacterial growth and decay, attachment to and detachment from the surface, substrate utilization and disinfectant action involved in the model. The usefulness of the model is further enhanced by the incorporation of an expression for bulk reaction parameter relating it with the organic carbon. The model is validated and applied to study the sensitive behavior of the components using a hypothetical network. The developed model is able to simulate the biodegradable organic carbon threshold in accordance with the values reported in the literature. The spread of contaminant intruded into the system at any location can also be simulated by the model. The multicomponent model developed is useful for water supply authorities in identifying the locations with high substrate concentrations, bacterial growth and lower chlorine residuals.