Potential for biofilm development in drinking water distribution systems

Regrowth of micro-organisms in drinking water distribution systems is caused by the utilisation of biodegradable compounds which are either present in treated water or originate from materials in contact with drinking water. In the Netherlands most drinking water is distributed without disinfectant residual and regrowth is limited by achieving biostable drinking water. A combination of methods is used to assess the biostability of drinking water. These methods are: (1) determination of the concentration of easily assimilable organic carbon (AOC); and (2) assessment of the biofilm formation rate (BFR). Assimilated organic carbon concentrations in drinking water in the Netherlands range from a few μg C/l in slow sand filtrates and in ground water supplies to values of ～ 50 μg C/l in supplies using ozonation in water treatment. Biofilm formation rate values were found to range from < 1 pg ATP/cm(2)/d in supplies using anaerobic ground water as the source. Increase of heterotrophic plate counts is limited at AOC values below 10 μg C/l. At BFR values below 10 pg ATP/cm(2)/d the risk of exceeding the guideline value for aeromonads (90 percentile < 200 c.f.u./100 ml) is less than 20%. Calculations based on the decrease of the AOC concentration observed in distributions systems confirm that very low concentrations of AOC can cause considerable biofilm formation on the pipe wall. The methods for assessing the biostability of drinking water combine with the assessment of the Biofilm Formation Potential of materials in contact with drinking water, thus providing a framework, the Unified Biofilm Approach, for evaluating the biostability of drinking water and materials.     

Molecular assessment of bacterial pathogens - a contribution to drinking water safety

Human bacterial pathogens are considered as an increasing threat to drinking water supplies worldwide because of the growing demand of high-quality drinking water and the decreasing quality and quantity of available raw water. Moreover, a negative impact of climate change on freshwater resources is expected. Recent advances in molecular detection technologies for bacterial pathogens in drinking water bear the promise in improving the safety of drinking water supplies by precise detection and identification of the pathogens. More importantly, the array of molecular approaches allows understanding details of infection routes of waterborne diseases, the effects of changes in drinking water treatment, and management of freshwater resources.     

Pyrosequence Analysis of the hsp65 Genes of Nontuberculous Mycobacterium Communities in Unchlorinated Drinking Water in the Netherlands

Studies have shown that certain opportunistic pathogenic species of nontuberculous mycobacteria (NTM) can be present in distributed drinking water. However, detailed information about NTM population composition in drinking water is lacking. Therefore, NTM communities in unchlorinated drinking water from the distribution system of five treatment plants in the Netherlands were characterized using 454 pyrosequencing of the hsp65 gene. Results showed high diversities in unchlorinated drinking water, with up to 28 different NTM operational taxonomic units (OTUs) in a single sample. Each drinking water sample had a unique NTM community, and most (81.1%) OTUs were observed only once. One OTU was observed in 14 of 16 drinking water samples, indicating that this NTM species is well adapted to unchlorinated drinking water conditions. A clear influence of season, source type (groundwater, surface water), easily assimilable organic carbon (AOC) concentration, biofilm formation rate, and active biomass in treated water on the establishment of an NTM community in drinking water was not observed. Apparently, local conditions are more important for the development of a specific NTM community in the drinking water distribution system. A low (4.2%) number of hsp65 gene sequences showed more than 97% similarity to sequences of the opportunistic pathogens M. avium, M. genavense, and M. gordonae. However, most (95.8%) NTM hsp65 gene sequences were related to not-yet-described NTM species that have not been linked to disease, indicating that most NTM species in unchlorinated drinking water from distribution systems in the Netherlands have a low public health significance.     

Water economy in a terrestrial toad (Bufo bufo), with special reference to cutaneous drinking and urinary bladder function

Undisturbed toads, acclimated to a simulated terrestrial habitat with access to water, generally visited the water resource for cutaneous drinking before evaporative water losses had resulted in dehydration of the body, and often the bladder still contained ample amounts of urine. The toads did not urinate when they stayed out of water, but exposure to water in the terrestrially-acclimated state facilitated urination, even when the bladder contained only insignificant amounts of urine. Daily emptying of the bladder often resulted in substantial water deficits prior to drinking, but the severity and frequency of the deficits declined with time, concurrently with an increase in the frequency of cutaneous drinking. Volumes of urine stored in the bladder when the toads suspended cutaneous drinking varied from negligible to large, corresponding to up to 20% of the body mass. Daily emptying of the bladder tended to increase the volume of urine stored at the end of drinking episodes. It is concluded that toads and other terrestrial amphibians primarily maintain normal water balance by anticipatory cutaneous drinking; emergency drinking in response to dehydration plays a secondary role.     

Factors affecting the drinking behavior of black howler monkeys (Alouatta pigra)

Water is essential for animals, and is particularly critical for thermoregulation. Animals obtain water from three main sources, free water, water contained in food, and water produced in the body during metabolism. Howler monkeys (Alouatta spp.) spend a small proportion of their time drinking water and some populations have not been observed drinking, suggesting they obtain most of their water requirements in food or by metabolism. However, when howler monkeys have been observed drinking there is evidence suggesting the drinking is associated with low precipitation, temperature, and fruit consumption, and high mature leaf consumption, although it remains unclear which factors determine drinking by this genus. In this study we tested the hypothesis that drinking by howler monkeys results from increased hydration requirements in drier climates and from lower consumption of foods rich in water (e.g., new leaves, fruit). We tested this hypothesis by comparative analysis of 14 groups of Yucatán black howler monkeys (A. pigra) living under different climatic conditions. From April 2005 to November 2008 we collected a total of 3,747.2 focal observation hours of the feeding and drinking behavior of 60 individuals, with data on ambient temperature and rainfall. Individuals spent more time drinking when they lived in habitats with higher maximum temperature and when they consumed more mature leaves. For this species, therefore, drinking seems to be linked to heat stress and a low availability of water in ingested food.     

Effect of high arsenic content in drinking water on rat brain.

The permissible limit of arsenic content in drinking water is 0.05 ppm, whereas, in many parts of West Bengal the arsenic level in drinking water is 0.1 ppm, frequently 0.3 ppm and even 3.0 ppm, though rarely. In order to assess possible risk to brain function by drinking such water, rats were given arsenic mixed in drinking water at the above four concentrations for 40 days. There was increased lipid peroxidation at all doses of arsenic, including the 'permissible limit', decrease in glutathione level, superoxide dismutase and glutathione reductase activities, indicating the free-radical-mediated degeneration of brain.     

Effect of saline intake on water flux and osmotic homeostasis in Pekin ducks (<Emphasis Type="Italic">Anas platyrhynchos</Emphasis>)

The physiological regulation of body water volume and concentration was evaluated in Pekin ducks, Anas platyrhynchos, slowly acclimated to increasingly saline drinking water (six equal 75 mM NaCl increments). Body mass, total body water (TBW), water flux, plasma osmolality (Osm(pl)), and ionic and osmoregulatory hormone concentrations were measured at the end of each increment. The salinity at which each variable deviates from its homeostatic set point was calculated by continuous two-phase linear regression. We hypothesized that, as drinking water salinity increases: (1) body water increases in concentration before it decreases in volume and (2) that regulating variables that help determine homeostatically set values (plasma hormone concentrations and water flux) deviate from values of freshwater ducks at lower drinking water salinities than the variables they regulate (Osm(pl), hematocrit, TBW). Osm(pl) was the first variable for which we could calculate a deviation from its homeostatically controlled value. It increases at much lower drinking water salinity than that at which TBW decreases, supporting our first hypothesis, but not our second hypothesis. We further hypothesized that, because the concentration of Pekin duck salt gland secretion is only slightly higher than that of their drinking water, they increase water flux (drinking) as salinity of drinking water increases, until the latter exceeds the secretion concentration and then they drink less. There was no change in water flux until it decreases when TBW decreases, 329 mM NaCl and 335 mM NaCl, respectively. The results do not support our hypothesis that Pekin ducks increase drinking as the salinity of their drinking water increases, but do indicate that, at tolerable salinities, Pekin ducks maintain body water volume while allowing body water osmolality to increase. At higher salinities, ducks decrease drinking and use body water to get rid of the excess salt.     

Prevalence, quantification and typing of adenoviruses detected in river and treated drinking water in South Africa

AIMS: Human adenoviruses (HAds), of which there are 51 serotypes, are associated with gastrointestinal, respiratory, urinary tract and eye infections. The importance of water in the transmission of HAds and the potential health risks constituted by HAds in these environments are widely recognized. Adenoviruses have not previously been quantified in river and treated drinking water samples. In this study, HAds in river water and treated drinking water sources in South Africa were detected, quantified and typed. METHODS AND RESULTS: Adenoviruses were recovered from the water samples using a glass wool adsorption-elution method followed by polyethylene glycol/NaCl precipitation for secondary concentration. The sensitivity and specificity of two nested PCR methods were compared for detection of HAds in the water samples. Over a 1-year period (June 2002 to July 2003), HAds were detected in 5.32% (10/188) of the treated drinking water and 22.22% (10/45) of river water samples using the conventional nested PCR method. The HAds detected in the water samples were quantified using a real-time PCR method. The original treated drinking water and river water samples had an estimate of less than one copy per litre of HAd DNA present. The hexon-PCR products used for typing HAds were directly sequenced or cloned into plasmids before sequencing. In treated drinking water samples, species D HAds predominated. In addition, adenovirus serotypes 2, 40 and 41 were each detected in three different treated drinking water samples. Most (70%) of the HAds detected in river water samples analysed were enteric HAds (serotypes 40 and 41). One HAd serotype 2 and two species D HAds were detected in the river water. CONCLUSIONS: Adenoviruses detected in river and treated drinking water samples were successfully quantified and typed. The detection of HAds in drinking water supplies treated and disinfected by internationally recommended methods, and which conform to quality limits for indicator bacteria, warrants an investigation of the risk of infection constituted by these viruses. The risk of infection may have implications for the management of drinking water quality. SIGNIFICANCE AND IMPACT OF THE STUDY: This study is unique as it is the first report on the quantification and typing of HAds in treated drinking water and river water. This baseline data is necessary for the meaningful assessment of the potential risk of infection constituted by these viruses.     

On the drinking water situation on the Cape Verde Islands (Island of Santiago)

On the Cape Verde Islands drinking water investigations were made. The drinking water was tested in chemical and bacteriological respects as well as on amebas and rotaviruses. The isolated germs were investigated on their reaction against several antibiotics and chemotherapeutics by means of the agar diffusion test. The changing of drinking water quality from water-supply-places to the households was investigated as well. According to the fact, that only 10.6% of 207 public water supplies investigated show drinking water quality after ONORM, and that nearly 30% and 80.2% of them contained E. coli and coliforme germs respectively, the urgency of extensive sanitations of water supplies on the Cape Verde Islands is evident.     

High levels of mutagenic activity in chlorinated drinking water in Finland

The organic extract from the drinking water of Kuopio, Eastern Finland, turned out to be highly mutagenic in the Ames test. The direct mutagenic activities of the acid/neutral fractions of 48 drinking water samples were on an average 1700 net revertants/l in strain TA100. The highest activities were more than 6000 net revertants/l, and one drinking water sample exceeded 10 000 net revertants/l. The drinking water of Kuopio is produced from lake water which has a relatively high content of humic substances. Water processing involved two chlorination phases. The organic constituents of the water samples were isolated either by continuous liquid-liquid extraction or by absorption on XAD 8 resin.     

饮用水系统硝化微生物分布规律、环境影响因素及调控应用的研究进展

硝化微生物广泛存在于饮用水系统中。水处理过程中,硝化微生物对含氮污染物的去除有突出贡献;而输配水过程中,硝化微生物会加剧消毒剂氯胺的降解,造成一系列饮用水微生物安全问题。本文介绍了常用硝化微生物检测方法,综述了硝化微生物在滤池、市政主管网、二次供水系统中的分布特征和规律,分析了环境因子及工程条件对硝化微生物的影响机制,探讨了硝化微生物强化应用及管控的实际工程措施,展望了未来饮用水系统中硝化微生物的研究重点与应用前景。     

Genotoxic activity of organic chemicals in drinking water

The information summarized in this review provides substantial evidence for the widespread presence of genotoxins in drinking water. In many, if not most cases, the genotoxic activity can be directly attributed to the chlorination stage of drinking water treatment. The genotoxic activity appears to originate primarily from reactions of chlorine with humic substances in the source waters. Genotoxic activity in drinking water concentrates has been most frequently demonstrated using bacterial mutagenicity tests but results with mammalian cell assay systems are generally consistent with the findings from the bacterial assays. There is currently no evidence for genotoxic damage following in vivo exposures to animals. In some locations genotoxic contaminants of probable industrial and/or agricultural origin occur in the source waters and contribute substantially to the genotoxic activity of finished drinking waters. The method used for sample concentration can have an important bearing on study results. In particular, organic acids account for most of the mutagenicity of chlorinated drinking water, and their recovery from water requires a sample acidification step prior to extraction or XAD resin adsorption. Considerable work has been done to determine the identity of the compounds responsible for the mutagenicity of organic concentrates of drinking water. Recently, one class of acidic compounds, the chlorinated hydroxyfuranones, has been shown to be responsible for a major part of the mutagenic activity. Strategies for drinking water treatment that have been evaluated with respect to reduction of genotoxins in drinking water include granular activated carbon (GAC) filtration, chemical destruction, and the use of alternative means of treatment (i.e., ozone, chlorine dioxide, and monochloramine). GAC treatment has been found to be effective for removal of mutagens from drinking water even after the GAC is beyond its normal use for organic carbon removal. All disinfectant chemicals appear to have the capacity of forming mutagenic chemicals during water treatment. However, the levels of mutagenicity formed with the alternative disinfectants have been generally less than those seen with chlorine and, especially in the case of ozone, highly dependent on the source water.(ABSTRACT TRUNCATED AT 400 WORDS)     

Longitudinal Exposure to Selected Pesticides in Drinking Water

The presence and temporal fluctuations of concentrations of insecticides and herbicides in natural waters has been well documented. Little, however, is known about exposure to pesticides through drinking water for the general population. Concentrations often pesticides, including 4,4′DDE and atrazine, were measured up to six times at equally spaced intervals over a 1-year period in drinking water of 80 randomly selected residences in Maryland. Atrazine was detected in 228 (57.9%) of the drinking water samples with a mean of 0.15?µg/L, with standard deviation 0.12?µg/L, median 0.17?µg/L, and range <0.037 to 0.46?µg/L. 4,4′DDE was found in 22 (5.6%) water samples; no other target analytes were detected. Concentrations of atrazine in drinking water were found to vary over a 12-month period with the greatest concentrations in the late summer and fall and the lowest in the early spring. Atrazine concentrations in drinking water were influenced more by differences in levels among residences than by time of year. Seven-day average exposures and exposures per unit body weight to atrazine in drinking water exhibited a similar temporal pattern. Among individuals, drinking water consumption rate was a more important determinant of atrazine exposure (µg/d) and exposure per unit body weight (µg/kg/d) than atrazine concentration in drinking water or body weight.     

Flexibility of the drinking mechanism in adult chickens (Gallus gallus) (Aves)

Summary Drinking was studied in adult chickens by cinematography and radiography. Three subsequent behavioral phases occur. (1) Water is transported from the water box into the oropharynx when the beak is immersed. Then delicately tuned cyclic motion patterns of beaks, tongue, and larynx transport water by capillarity, squeezing, and suction. (2) During the elevation of the head the tongue is elevated and the larynx is depressed to keep the water in the pharynx against the gravitational and centrifugal forces that result from the upward swing of the head. (3) During the tip up phase gravity transports the water to the esophagus, while the adhering water is pushed and squeezed caudad by tongue and larynx movements. Flexibility in the adult drinking mechanism was analyzed by comparing the drinking of normal and beak-trimmed chickens under normal drinking conditions, as well as while drinking small drops. Three modes of behavioral flexibility were discussed: conservative, regressive, and progressive flexibility. Most behavioral elements of the modal action pattern in drinking are so flexible that a chicken can reorganize the movement patterns of jaws, tongue, larynx, and head to adapt the mechanism to external (drop drinking) or internal (beak-trimming) changes. However, in drop drinking, the normal chicken relies upon a regressive takeover by an ontogenetically earlier developed pattern in the craniocervical motion system. Presence of the observed progressive flexibility in lingual and cervical motion patterns is shown to be a precondition for the avian drinking mechanism to keep up with dominant evolutionary changes in feeding mechanisms.     

Phosphorus and bacterial growth in drinking water.

The availability of organic carbon is considered the key factor to regulate microbial regrowth in drinking water network. However, boreal regions (northern Europe, Russia, and North America) contain a large amount of organic carbon in forests and peatlands. Therefore, natural waters (lakes, rivers, and groundwater) in the northern hemisphere generally have a high content of organic carbon. We found that microbial growth in drinking water in Finland is highly regulated not only by organic carbon but also by the availability of phosphorus. Microbial growth increased up to a phosphate concentration of 10 micrograms of PO4-P liter-1. Inorganic elements other than phosphorus did not affect microbial growth in drinking water. This observation offers novel possibilities to restrict microbial growth in water distribution systems by developing technologies to remove phosphorus efficiently from drinking water.     

Effects of botulism on ducks drinking saline water

Mallard (Anas platyrhynchos) ducklings (2 wk old) were given water from natural saline wetlands or fresh water as drinking water for 1 or 2 wk prior to, and after, receiving material containing Clostridium botulinum type C toxin. Water with conductivity ranging from 3,460 to 6,690 mu mhos/cm had no detectable effect on the occurrence or severity of clinical signs of botulism. Ducks drinking water with conductivity of 7,130 mu mhos/cm for 1 wk prior to receiving toxin had more severe clinical signs and greater mortality than did birds drinking fresh water. Ducks given the same water for 2 wk prior to receiving toxin did not differ from the controls in response to toxin. Fewer ducks in groups drinking the most saline water tested (conductivity = 13,500 mu mhos/cm) had clinical signs of botulism than in groups drinking fresh water.     

Tet-On Induction with Doxycycline after Gene Transfer in Mice: Sweetening of Drinking Water is not a Good Idea

Gene transfer to skeletal muscle leads to long-term, stable expression of transferred genes. An exiting development is the use of inducible expression systems. Using the inducible Tet-On system, it has been customary to administer doxycycline in drinking water with added sucrose to ameliorate the bitter taste. During a study aiming at regulating electrotransferred genes through the Tet-On system, we observed excessive drinking behavior among mice. Removal of sugar from the drinking water led to normal drinking behavior and most importantly did not affect the level of gene expression. Based on this study, the practice of adding sucrose to drinking water in doxycycline induction studies should be abandoned.     

Assessing Children's Exposures and Risks to Drinking Water Contaminants: A Manganese Case Study

Background: Compared to adults, children maybe more highly exposed to toxic substances in drinking water because they consume more water per unit of body weight. The U.S. Environmental Protection Agency (USEPA) has developed new guidance for selecting age groups and age-specific exposure factors for assessing children's exposures and risks to environmental contaminants. Research Aim: To demonstrate the application and importance of applying age-specific drinking water intake rates, health reference values, and exposure scenarios when assessing drinking water exposures because these approaches illustrate the potential for greater potential for adverse health effects among children. Methods: manganese, an essential nutrient and neurotoxicant, was selected as a case study and chemical of potential concern for children's health. A screening-level risk assessment was performed using age-specific drinking water intake rates and manganese concentrations from U.S. public drinking water systems. Results: When age-specific drinking water intake rates are used to calculate dose, formula-fed infants receive the highest dose of manganese from drinking water compared to all other age groups. Estimated hazard quotients suggest adverse health effects are possible. Use of USEPA's standardized childhood age groups and childhood exposure factors significantly improves the understanding of childhood exposure and risks.     

Tet-On induction with doxycycline after gene transfer in mice: sweetening of drinking water is not a good idea

Gene transfer to skeletal muscle leads to long-term, stable expression of transferred genes. An exiting development is the use of inducible expression systems. Using the inducible Tet-On system, it has been customary to administer doxycycline in drinking water with added sucrose to ameliorate the bitter taste. During a study aiming at regulating electrotransferred genes through the Tet-On system, we observed excessive drinking behavior among mice. Removal of sugar from the drinking water led to normal drinking behavior and most importantly did not affect the level of gene expression. Based on this study, the practice of adding sucrose to drinking water in doxycycline induction studies should be abandoned.     

DGGE分析东江流域农村饮用水源中微生物多样性及其与环境因子相关性

为评价东江流域农村饮用水源中微生物多样性及其与环境因子的相关性, 分别采集了集中式供水井、塘坝型水井、猪场附近水井、普通村落水井、水库水5种水样, 进行基因组总DNA的提取和主要理化指标的测定, 运用DGGE技术分析各水样总DNA的PCR产物。UPGMA聚类分析DGGE指纹图谱结果表明, 相同类型水样的微生物群落结构相似性较高, 聚集到一个分支上; 典型相关性分析(CCA)结果表明, 水体中总磷(TP)和总氮(TN)的浓度与微生物群落结构的关联度最高, 即磷和氮两种生命过程的基本元素对微生物群落影响最大; 序列分析表明农村饮用水源中微生物群落结构丰富, 包含了螺旋体门(Spirochaetes)、蓝藻门(Cyanobacteria)、变形菌门(Proteobacteria)、放线菌门(Actinobacteria)、酸杆菌门(Acidobacteria)5个门的细菌, 且每类水样拥有各自的优势菌。