Deposition of manganese in a drinking water distribution system.

The deposition of manganese in a water distribution system with manganese-related "dirty water" problems was studied over a 1-year period. Four monitoring laboratories with Robbins biofilm sampling devices fitted to the water mains were used to correlate the relationship among manganese deposition, the level of manganese in the water, and the chlorination conditions. Manganese deposition occurred by both chemical and microbial processes. Chemical deposition occurred when Mn(II) not removed during water treatment penetrated the filters and entered the distribution system, where it was oxidized by chlorine and chlorine dioxide used for disinfection. Microbial deposition occurred in areas with insufficient chlorination to control the growth of manganese-depositing biofilm. At 0.05 mg of Mn(II) per liter, the chemical deposition rate was much greater than microbial deposition. Significant deposition occurred at 0.03 mg of manganese per liter, and dirty water complaints were not eliminated until manganese levels were continuously less than 0.02 mg/liter and chlorination levels were greater than 0.2 mg/liter. A guideline level of 0.01 mg of manganese per liter is recommended.     

Deposition of manganese in a drinking water distribution system

The deposition of manganese in a water distribution system with manganese-related "dirty water" problems was studied over a 1-year period. Four monitoring laboratories with Robbins biofilm sampling devices fitted to the water mains were used to correlate the relationship among manganese deposition, the level of manganese in the water, and the chlorination conditions. Manganese deposition occurred by both chemical and microbial processes. Chemical deposition occurred when Mn(II) not removed during water treatment penetrated the filters and entered the distribution system, where it was oxidized by chlorine and chlorine dioxide used for disinfection. Microbial deposition occurred in areas with insufficient chlorination to control the growth of manganese-depositing biofilm. At 0.05 mg of Mn(II) per liter, the chemical deposition rate was much greater than microbial deposition. Significant deposition occurred at 0.03 mg of manganese per liter, and dirty water complaints were not eliminated until manganese levels were continuously less than 0.02 mg/liter and chlorination levels were greater than 0.2 mg/liter. A guideline level of 0.01 mg of manganese per liter is recommended.     

Efficacy of bromochlorodimethylhydantoin againstLegionella pneumophila in industrial cooling water

Summary Free residual chlorine and bromine can be generated in water from bromochlorodimethylhydantoin (BCDMH). Efficacy of chlorine from inorganic sources has been studied extensively, but there is much less information on the efficacy of bromine againstL. pneumophila; only a few efficacy studies of organically-derived. halogen appear in the literature and the results from different studies conflict or are difficult to interpret. This paper describes the efficacy of halogen from BCDMH against planktonic, pure cultureL. pneumophila in an industrial cooling water. There was no difference in efficacy between halogen derived from organic or inorganic sources in controlled laboratory experiments. Effective doses in laboratory studies cannot be translated directly to field applications because of significant differences in the microbiology. However, the data suggest that disinfection (>99.9% reduction in viability within 10 min) of planktonic, pure cultureL. pneumophila can be achieved with about 1 ppm free residual halogen (expressed as chlorine) from BCDMH in a typical industrial cooling water.     

Examination of microbial contaminants of emergency showers and eyewash stations

To evaluate the effects of regular flushing, water from fifty emergency eyewash and shower stations was cultured for the presence of potentially pathogenic protozoa, heterotrophic bacteria, and Legionella species. This study also provided the opportunity to evaluate a commercially available molecular assay for the direct detection of Legionella sp in environmental samples. The Perkin Elmer Legionella EnviroAmp polymerase chain reaction (PCR) kit and culture on buffered charcoal yeast extract agar were used to detect Legionella species in water samples. Chemical and physical parameters of station water measured included: pH, hardness, alkalinity, turbidity, conductivity, total chlorine and assimilable organic carbon. Protozoal isolates were identified by classical identification methods, and isolates from the stations were identified as Hartmannella sp, Vexillifera sp, Vahlkampfia sp, Acanthamoeba sp, and Vanella sp. Heterotrophic plate counts ranged from 10² to 10⁶ CFU ml⁻¹ and acridine orange total counts ranged from 10³ to 10⁶ cells ml⁻¹ after regular flushing. PCR and gene probe analysis showed that 89% of the stations (eyewash and shower) were positive for Legionella species by PCR, while 6% of the samples were culture positive. These results indicate that routine flushing alone is not sufficient to control microbial contamination and disinfection must also be included in a routine maintenance program. In addition, regular maintenance, disinfection, and monitoring of emergency eyewash and shower stations is important in preventing potential secondary microbial infections by either direct inoculation or aerosol transmission. Received 02 September 1997/ Accepted in revised form 29 November 1997     

Comparison of culture methods and an immunofluorescence assay for the detection ofLegionella pneumophila in domestic hot water devices

The objective of this study was to compare an indirect immunofluorescence assay with culture methods for the identification ofLegionella pneumophila serogroups 1 to 6 in hot water samples taken from domestic environments. Hot water samples were obtained from the water heater, the shower heads, and the most frequently used faucet of 211 private houses. Concentrated water samples were inoculated on buffered charcoal yeast extract agar (BCYE) and on a semi-selective culture medium (GPV). Colonies with a morphology similar to that ofLegionellaceae were subcultured on BCYE and on blood agar plates; those that grew on the former but not the latter were further characterized and identified by direct immunofluorescence techniques. The concentrated samples were also smeared on multiple-well microscope slides and tested by indirect immunofluorescence with monoclonal antibodies againstL. pneumophila, serogroups 1 to 6. Of the houses studied, 30% were found to contain culturableL. pneumophila in at least one water sample, whereas 63% were positive by indirect immunofluorescence. The sensitivity of this assay compared with culture varied from 16.7–21.1%, and its specificity was between 76.7% and 88.3% depending on the sample source (water heater, shower heads, or faucet). In the 38 houses with at least one positive sample found by both immunofluorescence and culture, total or partial agreement between serogroups identified by both techniques was only 34%. The results obtained in this study strongly suggest that indirect immunofluorescence is not an adequate alternative for the identification ofL. pneumophila in hot water systems.     

Disinfection characteristics of waterborne pathogenic protozoaGiardia lamblia

Giardia lamblia is a parasitic protozoa which is transmitted in the form of a cyst through untreated water and also treated drinking water. Since its presence in water has led to frequent outbreaks of giardiasis and death in many countries, the removal and disinfection of this protozoan cyst from the water supply are of great concern for public health. This study examined the disinfection characteristics ofG. lamblia cysts isolated from a Korean patient with giardiasis. When using sodium hypochlorite includdig 5 or 10 ppm chlorine, the killing rate was initially rapid however, the disinfection slowed down and a Blog reduction could not be achieved even after 2 h. The disinfection effectiveness was also reduced at a lower temperature, thereby implying that the risk of a giardiasis outbreak will be higher in the winter season. A CT (concentration time) curve was constructed based on the results with sodium hypochlorite for use in designing and predicting disinfection performance. The organic chlorination disinfectant SDIC (sodium dichloroisocyanurate) produced a lower pH and a much higher residual effect than sodium hypochlorote. The disinfection of cysts by SDIC continued steadily throughout 2 h of contact, although the initial killing rate was lower than that with sodium hypochlorite.     

The influence of chlorination timing and concentration on microbial communities in labyrinth channels: implications for biofilm removal

Chlorination is an effective method to control biofilm formation in enclosed pipelines. To date, very little is known about how to control biofilms at the mesoscale in complex pipelines through chlorination. In this study, the dynamic of microbial communities was examined under different residual chlorine concentrations on the biofilms attached to labyrinth channels for drip irrigation using reclaimed water. The results indicated that the microbial phospholipid fatty acids, extracellular polymeric substances, microbial dynamics, and the ace and Shannon microbial diversity indices showed a gradual decrease after chlorination. However, chlorination increased microbial activity by 0.5–19.2%. The increase in the relative abundances of chloride-resistant bacteria (Acinetobacter and Thermomonas) could lead to a potential risk of chlorine resistance. Thus, keeping a low chlorine concentration (0.83?mg l^?1 for 3?h) is effective for controlling biofilm formation in the labyrinth channels.     

Acanthamoeba castellanii: Cellular changes induced by chlorination

Chlorination is a well-known disinfection method, used in water treatment to inactivate various microorganisms, it induces numerous cellular changes. Even though Acanthamoebae are frequently found in water, the cellular changes induced in Acanthamoebae have not been described in the literature. Acanthamoebae are pathogenic amoebae and may provide a reservoir for pathogenic bacteria such as Legionellapneumophila; it is consequently important to understand the response of this amoeba to chlorination, and our study was indeed aimed at examining cellular changes in Acanthamoebae following chlorination. Acanthamoeba trophozoites were treated at various chlorine concentrations (1-5 mg/L). A 3-log reduction in Acanthamoebae population was achieved with 5 mg/L of free chlorine. Confocal microscopy and flow cytometry experiments indicated that chlorination induced cell permeabilization, size reduction and likely intracellular thiol concentration. Our data show that among the non-cultivable cells some remained impermeabilized (negative staining with propidium iodide), thereby suggesting that these cells might remained viable. A similar state is described in other microorganisms as a VBNC (viable but not cultivable) state. Electron microscopy observations illustrate drastic morphological changes: the pseudopods disappeared and subcellular components, such as mitochondrion, were pronouncedly affected. In conclusion, depending on the concentration used, chlorination leads to many cellular effects on Acanthamoeba that could well arise in cell inactivation.     

Accumulation and Fate of Microorganisms and Microspheres in Biofilms Formed in a Pilot-Scale Water Distribution System

The accumulation and fate of model microbial “pathogens” within a drinking-water distribution system was investigated in naturally grown biofilms formed in a novel pilot-scale water distribution system provided with chlorinated and UV-treated water. Biofilms were exposed to 1-μm hydrophilic and hydrophobic microspheres, Salmonella bacteriophages 28B, and Legionella pneumophila bacteria, and their fate was monitored over a 38-day period. The accumulation of model pathogens was generally independent of the biofilm cell density and was shown to be dependent on particle surface properties, where hydrophilic spheres accumulated to a larger extent than hydrophobic ones. A higher accumulation of culturable legionellae was measured in the chlorinated system compared to the UV-treated system with increasing residence time. The fate of spheres and fluorescence in situ hybridization-positive legionellae was similar and independent of the primary disinfectant applied and water residence time. The more rapid loss of culturable legionellae compared to the fluorescence in situ hybridization-positive legionellae was attributed to a loss in culturability rather than physical desorption. Loss of bacteriophage 28B plaque-forming ability together with erosion may have affected their fate within biofilms in the pilot-scale distribution system. The current study has demonstrated that desorption was one of the primary mechanisms affecting the loss of microspheres, legionellae, and bacteriophage from biofilms within a pilot-scale distribution system as well as disinfection and biological grazing. In general, two primary disinfection regimens (chlorination and UV treatment) were not shown to have a measurable impact on the accumulation and fate of model microbial pathogens within a water distribution system.     

Effects of Assimilable Organic Carbon and Free Chlorine on Bacterial Growth in Drinking Water

Assimilable organic carbon (AOC) is one of the most important factors affecting the re-growth of microorganisms in drinking water. High AOC concentrations result in biological instability, but disinfection kills microbes to ensure the safety of drinking water. Free chlorine is an important oxidizing agent used during the disinfection process. Therefore, we explored the combined effects of AOC and free chlorine on bacterial growth in drinking water using flow cytometry (FCM). The initial AOC concentration was 168 μg.L^-1 in all water samples. Without free chlorine, the concentrations of intact bacteria increased but the level of AOC decreased. The addition of sodium hypochlorite caused an increase and fluctuation in AOC due to the oxidation of organic carbon. The concentrations of intact bacteria decreased from 1.1×10⁵ cells.mL^-1 to 2.6×10⁴ cells.mL^-1 at an initial free chlorine dose of 0.6 mg.L^-1 to 4.8×10⁴ cells.mL^-1 at an initial free chlorine dose of 0.3 mg.L^-1 due to free chlorine originating from sodium hypochlorite. Additionally, free chlorine might be more obviously affected AOC concentrations than microbial growth did. These results suggested that AOC and free chlorine might have combined effects on microbial growth. In this study, our results showed concentrations determined by FCM were higher than those by HPC, which indicated that some E. coli detected by FCM might not be detected using HPC in drinking water. The level of free chlorine might restrain the consumption of AOC by inhibiting the growth of E. coli; on the other hand, chlorination might increase the level of AOC, thereby increase the potential for microbial growth in the drinking water network.     

Membrane biofouling by chlorine resistant Bacillus spp.: effect of feedwater chlorination on bacteria and membrane biofouling

In this study, bacteria isolated from a lake were characterised for their chlorine resistivity and the effects of chlorination on growth, mortality, protein expression and attachment propensity towards membranes. Biofouling and membrane performance were analysed. All isolated chlorine resistant strains, characterised by 16s rRNA gene sequencing, belonged to the genus Bacillus. Chlorination caused limited effects on bacterial growth and mortality. B. safensis and B. lechinoformis suffered the maximum effects due to chlorination. Live-to-dead ratios immediately after chlorination were above 1.3, with some exceptions. The membrane pure water flux recovery was highly strain dependent. Irreversible membrane fouling was observed with B. aquimaris. Membrane flux decreased substantially during ultrafiltration of water containing chlorine resistant bacteria.     

Chlorination-mediated EPS excretion shapes early-stage biofilm formation in drinking water systems

Microbial surface adhesion to surfaces and subsequent biofilm establishment are ubiquitous in drinking water systems, which often contribute to deteriorated water quality. Disinfectants are common agents applied to drinking water controlling microbial propagation, yet the underlying mechanisms of how disinfectants function to regulate microbial activity and thereby biofilm development remains elusive. We experimentally studied the effects of chlorination on extracellular polymeric substance (EPS) production, and its impacts on early-stage biofilm formation in a model drinking water system. Results showed that low-level chlorine (≤ 1.0 mg/L) stimulated microbial EPS (especially of proteins) excretion that favored early-stage biofilm formation. Microbes experiencing higher chlorination (>1.0 mg/L) exhibited clearly suppressed growth associated with reduced EPS release, consequently yielding less biofilm formation. Removal of cell-attached proteins and polysaccharides diminished biofilm formation, which highlighted the critical role of EPS (especially protein components) in biofilm development. A negative correlation between chlorination-mediated microbial protein production and cell surface charge suggested that chlorine disinfection may modify cell surface properties through regulation of microbial EPS excretion and thereby mediate biofilm formation. With these quantitative estimations, this study provides novel insights into how chlorination-mediated EPS excretion shapes early-stage biofilm formation, which is essential for practical functioning of drinking water systems.     

Population diversity in model potable water biofilms receiving chlorine or chloramine residual

Abstract

Most water utilities use chlorine or chloramine to produce potable water. These disinfecting agents react with water to produce residual oxidants within a water distribution system (WDS) to control bacterial growth. While monochloramine is considered more stable than chlorine, little is known about the effect it has on WDS biofilms. Community structure of 10-week old WDS biofilms exposed to disinfectants was assessed after developing model biofilms from unamended distribution water. Four biofilm types were developed on polycarbonate slides within annular reactors while receiving chlorine, chloramine, or inactivated disinfectant residual. Eubacteria were identified through 16S rDNA sequence analysis. The model WDS biofilm exposed to chloramine mainly contained Mycobacterium and Dechloromonas sequences, while a variety of alpha- and additional beta-proteobacteria dominated the 16S rDNA clone libraries in the other three biofilms. Additionally, bacterial clones distantly related to Legionella were found in one of the biofilms receiving water with inactivated chlorine residual. The biofilm reactor receiving chloraminated water required increasing amounts of disinfectant after 2 weeks to maintain chlorine residual. In contrast, free chlorine residual remained steady in the reactor that received chlorinated water. The differences in bacterial populations of potable water biofilms suggest that disinfecting agents can influence biofilm development. These results also suggest that biofilm communities in distribution systems are capable of changing in response to disinfection practices.     

Formation of natural biofilms during chlorine dioxide and u.v. disinfection in a public drinking water distribution system

AIMS: The influence of two disinfection techniques on natural biofilm development during drinking water treatment and subsequent distribution is compared with regard to the supply of a high-quality drinking water. METHODS AND RESULTS: The growth of biofilms was studied using the biofilm device technique in a real public technical drinking water asset. Different pipe materials which are commonly used in drinking water facilities (hardened polyethylene, polyvinyl chloride, steel and copper) were used as substrates for biofilm formation. Apart from young biofilms, several months old biofilms were compared in terms of material dependence, biomass and physiological state. Vital staining of biofilms with 5-cyano-2,3-ditolyl tetrazolium chloride (CTC) and the DNA-specific 4',6-diamidino-2-phenylindole (DAPI) staining resulted in a significant difference in physiological behaviour of biofilm populations depending on the disinfection technique. Compared with chlorine dioxide disinfection (0.12-0.16 mg l-1), the respiratory activities of the micro-organisms were increased on all materials during u.v. disinfection (u.v.254; 400 J m-2). The biofilm biocoenosis was analysed by in situ hybridization with labelled oligonucleotides specific for some subclasses of Proteobacteria. Using PCR and additional hybridization techniques, the biofilms were also tested for the presence of Legionella spp., atypical mycobacteria and enterococci. The results of the molecular-biological experiments in combination with cultivation tests showed that enterococci were able to pass the u.v. disinfection barrier and persist in biofilms of the distribution system, but not after chlorine dioxide disinfection. CONCLUSIONS: The results indicated that bacteria are able to regenerate and proliferate more effectively after u.v. irradiation at the waterworks, and chlorine dioxide disinfection appears to be more applicative to maintain a biological stable drinking water. SIGNIFICANCE AND IMPACT OF THE STUDY: As far as the application of u.v. disinfection is used for conditioning of critical water sources for drinking water, the efficiency of u.v. irradiation in natural systems should reach a high standard to avoid adverse impacts on human health.     

Attachment as a factor in the protection of Enterobacter cloacae from chlorination

Enterobacter cloacae attached to drinking water distribution particles was subjected to chlorination. Attachment resulted in the protection of these organisms from disinfection. This effect was found to be dependent upon both the level of chlorine in the system and attachment time. The results obtained in this study indicate that attached organisms may play an important role in coliform outbreaks.     

Attachment as a factor in the protection of Enterobacter cloacae from chlorination.

Enterobacter cloacae attached to drinking water distribution particles was subjected to chlorination. Attachment resulted in the protection of these organisms from disinfection. This effect was found to be dependent upon both the level of chlorine in the system and attachment time. The results obtained in this study indicate that attached organisms may play an important role in coliform outbreaks.     

Microbial challenges for domestic heating oil storage tanks

Microbial growth on hydrocarbons is common in nature and used in bioremediation of contaminated sites, whereas in fuel storage tanks this phenomenon can affect the stability of the fuel and the tank. The impact of microbial growth and produced metabolites on materials, which are used in the construction of storage tanks, were analyzed. In contrast to metal tank components, polymeric materials did not affect or were influenced by microorganisms. Zinc was highly corroded by microbial growth, most likely due to the formation of organic acids that were produced during microbial growth on hydrocarbons. A contaminated water phase in a storage tank of a heating system was simulated with a self‐constructed pump test bench. Microbial growth began in the water phase of the storage tank and microbes were distributed throughout the tank system, through water‐in‐oil microemulsions. No microbial growth was observed in oil that was previously contaminated, indicating that essential nutrients had been depleted. The identification and removal of these essential nutrients from fuels could minimize or prevent microbial contamination. The results are discussed with regard to developing recommendations for the design and operation of domestic heating oil storage tanks to lower the risk of technical failure due to microbial contamination.     

Necessity and Effect of Combating Legionella pneumophila in Municipal Shower Systems

The objective was to obtain research-based, holistic knowledge about necessity and effect of practiced measures against L. pneumophila in municipal shower systems in Stavanger, Norway. The effects of hot water treatment and membrane-filtering were investigated and compared to no intervention at all. The studies were done under real-world conditions. Additionally, a surveillance pilot study of municipal showers in Stavanger was performed. The validity of high total plate count (TPC) as an indication of L. pneumophila was evaluated. A simplified method, named “dripping method”, for detection and quantification of L. pneumophila was developed. The sensitivity of the dripping method is 5 colony-forming units of L. pneumophila/ml. The transference of L. pneumophila from shower water to aerosols was studied. Interviews and observational studies among the stakeholders were done in order to identify patterns of communication and behavior in a Legionella risk perspective. No substantial effects of the measures against L. pneumophila were demonstrated, except for a distally placed membrane filter. No significant positive correlation between TPC and L. pneumophila concentrations were found. L. pneumophila serogroup 2–14 was demonstrated in 21% of the 29 buildings tested in the surveillance pilot. Relatively few cells of L. pneumophila were transferred from shower water to aerosols. Anxiety appeared as the major driving force in the risk governance of Legionella. In conclusion, the risk of acquiring Legionnaires'' disease from municipal shower systems is evaluated as low and uncertain. By eliminating ineffective approaches, targeted Legionella risk governance can be practiced. Risk management by surveillance is evaluated as appropriate.     

Peracetic acid as an alternative wastewater disinfectant to chlorine dioxide

AIMS: The aim of this study was to compare the efficiency of peracetic acid with that of chlorine dioxide in the disinfection of wastewater from a sewage treatment plant (serving about 650 000 inhabitants) that has been using peracetic acid as a disinfectant since 1998. METHODS AND RESULTS: A total of 23 samplings were made, each consisting of three samples: from secondary effluent, effluent disinfected with 2 mg l(-1) of peracetic acid and effluent disinfected with 2.2 mg l(-1) of chlorine dioxide (contact time 20 min). For each sample, measurements were made of the heterotrophic plate count at 36 degrees C, total and faecal coliforms, Escherichia coli, enterococci, pH, suspended solids and chemical oxygen demand (COD). During the first phase of the experiment the peracetic acid was seen to be less efficient than chlorine dioxide. To improve the disinfectant action a system of mechanical agitation was added which led to a greater efficiency in the inactivation of bacteria of faecal origin. CONCLUSIONS: Both products were found to be influenced by the level of microbial contamination, the amount of suspended solids and COD but not by the pH of the effluent before disinfection. The immediate mixing of the wastewater and disinfectant caused a greater reduction in enterococci. SIGNIFICANCE AND IMPACT OF THE STUDY: Since peracetic acid was seen to produce a high abatement of micro-organisms, it can be considered as a valid alternative to chlorine dioxide in the disinfection of wastewaters.     

Drinking water chlorination in dairy beef fattening bulls: water quality,potential hazards,apparent total tract digestibility,and growth performance

The first study aimed to evaluate the effect of drinking water disinfection (chlorination: NaClO 15%) and conditioning (acidification: H₃PO₄ diluted 1:5 in water) on water quality, water and feed consumption, apparent total tract digestibility, and its potential hazardous effects on Holstein bulls fed high-concentrate diets. Twenty-four animals (221 ± 20.9 kg of BW, and 184 ± 9.9 days of age) were individually assigned to one of four treatments according to a 2 × 2 factorial arrangement: conditioning (with or without acidification) and disinfection (with or without chlorination). The entire study lasted 210 days. Physicochemical and microbiological water quality, water and feed consumption, haematological and biochemical blood parameters, and apparent total tract digestibility were measured; data were analysed via a mixed-effects model. Chlorination and acidification increased (P = 0.02) free residual chlorine in water, and chlorination reduced (P = 0.01) total coliform and Clostridium perfringens counts in water. Treatment did not affect water consumption, total DM intake, or blood parameters. At the beginning of the study, NDF digestibility decreased (P = 0.04) with acidification, however, this was restored at the end of the study. The second study evaluated the potential benefit of drinking water chlorination and acidification on the performance of crossbred Holstein bulls fed high-concentrate diets under commercial conditions. Ninety-six animals (322 ± 35.0 kg of BW, and 220 ± 14.2 days of age) were allocated into six pens assigned to one of the two treatments: untreated drinking water or drinking water treated with chlorination and acidification for a total of 112 days. Physicochemical and microbiological water quality, water and concentrate consumption, eating behaviour, growth performance, and carcass quality were analysed via a mixed-effects model. Water conditioning and disinfection increased (P = 0.01) free residual chlorine concentration and reduced (P = 0.04) total coliform count in water. Although water consumption and eating behaviour were similar between treatments, water conditioning and disinfection increased average daily weight gain (P = 0.03), BW before slaughter (P = 0.01), and hot carcass weight (P = 0.01). In conclusion, drinking water chlorination and acidification in fattening dairy beef bulls is recommended as it improves growth performance without any detrimental side effects on health or nutrient digestibility.