Endotoxins associated with cyanobacteria and their removal during drinking water treatment

The aim of this study was to investigate endotoxin concentrations in cyanobacterial water blooms and strains, and to assess the removal of endotoxins during drinking water treatment. Endotoxin concentrations were measured from 151 hepatotoxic, neurotoxic and non-toxic cyanobacterial water blooms by using Limulus amebocyte lysate (LAL) assay, and the results were compared to bacterial data. Endotoxin activities ranged from 20 to 3.8 x 10(4) endotoxin units (EU) per ml. Endotoxicity of the samples correlated with phycobiliprotein concentration that was used to assess cyanobacterial abundance, heterotrophic plate count, and Aeromonas spp. but it did not correlate with the number of coliforms or streptococci. The high endotoxin concentrations occasionally detected in the water bloom samples were probably due to Gram negative bacteria that existed together with cyanobacteria since the 26 axenic cyanobacterial strains from different genera that were studied showed very low endotoxin activity. No differences in endotoxin activity were detected between hepatotoxic, neurotoxic and non-toxic strains. Removal of endotoxins during drinking water treatment was studied at nine waterworks that previously had been associated with high numbers of cyanobacteria and that used different processes for water purification. Endotoxin concentration in raw waters ranged from 18 to 356 EU ml(-1). The treatment processes reduced 59-97% of the endotoxin activity; in the treated water the concentration ranged from 3 to 15 EU ml(-1). The most significant reduction occurred at the early stages of water treatment, during coagulation, settling and sand filtration. Activated carbon filtration either increased or had no effect on endotoxin concentration. Ozonation and chlorination had little effect on the endotoxin concentrations.     

降低饮用水中残余铝的中试研究

研究了水处理过程中铝含量的影响因素和控制条件,结果表明:对水中铝含量的影响PAC投加量＞pH＞滤速＞活化硅酸投加量.控制余铝的最佳条件是:PAC投加量2.0 mg/L,pH值7.5,活化硅酸投加量1.5 mg/L,滤速8.0 m/h.过滤阶段对铝的影响小于混凝阶段,水厂实际运行时应尽量采用低滤速.为控制出厂水铝含量,建...     

Inactivation of Giardia muris cysts using medium-pressure ultraviolet radiation in filtered drinking water

The effect of medium pressure ultraviolet radiation on Giardia muris was studied using a collimated beam apparatus with filtered surface water from the Grand River, Kitchener, Ontario, Canada. UV doses ranged from 5 to 83 mJ/cm² and resulted in 2–3 log-units of reduction in infectivity measured by a C3H/HeN mouse infectivity model. In vitro excystation and nucleic acid staining with Live/Dead BacLight^™ greatly underestimated the inactivation of Giardia when compared with animal infectivity. Medium pressure ultraviolet radiation is a potential alternative to conventional chemical disinfection methods.     

Light adaptation and -inhibition: processes important in modelling the growth of algae in drinking water basins

The need to take into account the processes of light inhibition and -adaptation in models for algal-growth was studied. The results of recent work on inhibition cast doubt on the occurrence of inhibition in natural systems. On the basis of time constants it was concluded in this study that it is necessary to take adaptation into account in modelling. A model is proposed to describe the photosynthesis light relation which includes inhibition and adaptation.The model was compared with experimental results given in literature. The results of comparison seemed satisfactory, but further experimental work is recommended to verify this conclusion.     

黄河水异味和藻类控制的生产性试验研究

针对黄河水藻类高发的现象,对水源地和沉砂池进行了取样分析,确定藻类为异味产生的根源.预处理试验结果表明,在投加20 mg/L聚合铁和10 mg/L硅酸钠的同时,投加0.4-1.0 mg/L聚二烯丙基二甲基氯化铵(FL45C)对藻类和浊度的去除以及臭和味的控制效果较好.     

Cryptosporidium and Giardia detection in water bodies of Galicia, Spain

The objective of this study was to determine the mean concentration (per litre) of Cryptosporidium oocysts and Giardia cysts in recreational river areas (n = 28), drinking water treatments plants (DWTPs; n = 52) and wastewater treatment plants (WWTPs; n = 50) in Galicia (NW Spain). Water samples from rivers and from the influent (50–100 l) and the treated effluent (100 l) of the water plants were filtered using Filta-Max filters (IDEXX Laboratories, Inc., Westbrook, ME, USA). A total of 232 samples were processed and the (oo)cysts were concentrated, clarified by IMS and then detected by IFAT. The viability was determined by applying fluorogenic vital dye (PI).In the recreational areas, infective forms of Cryptosporidium and Giardia were detected in 16 (57.1%; 1–60 oocysts per litre) and 17 (60.7%; 1–160 cysts per litre) samples, respectively. In the water flowing into the water treatment plants, oocysts were detected in 21 DWTPs (40.4%; 1–13 oocysts per litre) and cysts were observed in 22 DWTPs (42.3%; 1–7 cysts per litre). In the effluents from the treatment plants, Cryptosporidium oocysts and Giardia cysts were identified in 17 DWTPs (32.7%; 1–4 oocysts per litre) and in 19 DWTPs (36.5%; 1–5 cysts per litre), respectively. The highest concentrations of (oo)cysts were found in the WWTPs; specifically, oocysts were detected in 29 (58.0%; 1–80 oocysts per litre) and cysts in 49 (98.0%; 2–14.400 cysts per litre) WWTP effluents. Cryptosporidium and Giardia were detected in 32 (64.0%; 1–120 oocysts per litre) and 48 (96.0%; 2–6.000 cysts per litre) WWTP effluents, respectively. The percentage viability of the (oo)cysts ranged between 90.0% and 95.0%. In all samples analysed. Moreover, it was found that the effluents from coastal WWTPs were discharged directly into the sea, while inland WWTPs were discharged directly into rivers. The concentrations of both enteropathogens detected in effluents from WWTPs therefore represent a significant risk to human and animal health.These results demonstrate the wide distribution of Cryptosporidium and Giardia in the environment, the ineffectiveness of treatments in DWTPs and WWTPs in reducing/inactivating both protozoa and the need to monitor the presence, viability and infectivity of Cryptosporidium and Giardia in water bodies. In conclusion, the findings suggest the need for better monitoring of water quality and identification of sources of contamination.     

Comparison of the toxicity thresholds of water pollutants to bacteria, algae, and protozoa in the cell multiplication inhibition test

Using analogous methods of the cell multiplication inhibition test, the toxicity threshold (TT) of 156 potential water pollutants was determined for model organisms of biological self-purification, i.e. bacteria of the species Pseudomonas putida, green algae of the species Scenedesmus quadricauda, and flagellate protozoa of the species Entosiphon sulcatum. From the number of 156 inorganic and organic pollutants tested, 23 exhibited a pronounced selective toxic action on bacteria of the species Pseudomonas putida, 47 on algae of the species Scenedesmus quadricauda, and 43 on flagellate protozoa of the species Entosiphon sulcatum. It is seen from the ratios found that a determination of the toxicity threshold of potential water pollutants for these three model organisms from the microbiological spectrum would provide a broader basis for assessing the damaging action of water pollutants to model organisms active in the biological self-purification of water. Ecotoxicological testing of potential water pollutants to evaluate their toxicity involving only one model organism of biological self-purification would give an incomplete and biased picture of the effects of pollutants.     

Occurrence of Giardia cysts and Cryptosporidium oocysts in raw and treated water from two water treatment plants in Selangor, Malaysia

The occurrence of Giardia cysts and Cryptosporidium oocysts was determined both in the raw water and the treated waters from two water treatment plants in Selangor, Malaysia between July 1994 and January 1995. At each treatment plant, raw and treated water samples were collected fortnightly on 10 separate occasions. Physical parameters, including dissolved oxygen, pH, temperature, conductivity, turbidity and free and total chlorine were measured, and samples were also taken for faecal coliform analyses. The isolation and enumeration of cysts and oocysts was according to UK standard methods. Whilst Giardia cysts were detected in 90% of the raw water samples (range 0–60 cysts per litre) no Cryptosporidium oocysts were detected. Higher concentrations of cysts were detected in the raw water of the first treatment plant. All raw water samples were faecally contaminated, as faecal coliform counts ranged from 4.6 × 10⁴ to 1.3 × 10⁵ colony forming units per 100 ml. No correlation between the concentration of Giardia cysts and the concentration of faecal coliforms could be demonstrated statistically, nor was there any correlation between the concentration of Giardia cysts and the physical parameters tested for any of the raw waters. No cysts, oocysts or faecal coliforms were detected in samples of treated water.     

Pseudomonas aeruginosa and Escherichia coli in sewage and fresh water

Pseudomonas aeruginosa was isolated consistently from domestic and hospital sewage. In domestic sewage the numbers were usually less than 30,000 per 100 ml whereas counts above 500,000 per 100 ml were frequently obtained in hospital sewage. Correspondingly high counts of Escherichia coli were not found in hospital sewage and the ratio of E. coli to P. aeruginosa was usually less than 25 compared to ratios of over 500 often found in ordinary domestic sewage. During passage through sewage treatment plants the numbers of both bacteria were reduced by about 90% so that their ratio in the effluent remained the same as in raw sewage.In samples from a fresh-water stream the numbers of P. aeruginosa reflected the levels of domestic pollution. Variations in the counts of the organism over the length of the stream usually closely parallelled those of E. coli. However, in samples taken from the stream in lightly populated, agricultural areas P. aeruginosa was frequently not isolated even when the counts of E. coli were high. This was consistent with results from examinations of faecal specimens which confirmed the presence of P. aeruginosa in humans but indicated that in animals the organism was not present in significant numbers.     

Report of the NATO/CCMS drinking water pilot study on health aspects of drinking water contaminants

Various methods of disinfection are being successfully used to control waterborne diseases due to biological contaminants in water (viruses, bacteria, protozoa). These methods of chemical control are adding chemical contaminants to the drinking water. For example, trihalomethanes may be formed by the interaction of chlorine with humic and/or fulvic acids. In addition, chemical contaminants may arise from natural, agricultural, industrial or distributional sources. Acute or chronic exposures to these chemicals may result in adverse health effects that are immediate or delayed, reversible or irreversible. Since these contaminants rarely occur singly, chemical interactions (additives, synergistic, antagonistic) must be considered. The nature of the adverse health effects can usually be determined from properly designed and executed animal experiments and/or human epidemiological studies. Potentially toxic agents may also be identified by the use of short term or in vitro tests. Other methods of identification of potentially toxic agents include chemical similarity with known toxicants.Attempts should be made to reduce the number of potentially toxic chemical contaminantsbut the microbiological quality of drinking water must not be compromised.     

Asbestos and drinking water in Canada

Samples of raw, treated and distributed tap water were collected from 71municipalities across Canada and analyzed for asbestos content by transmission electron microscopy. Chrysotile asbestos was identified as the major asbestos type present in drinking water with some 5% of public water supplies containing asbestos at concentrations greater than 10 million fibres per litre. Improvement factors of up to 300 were observed for the removal of chrysotile fibres from drinking water during treatment, indicating that coagulation/filtration treatment is efficient for this purpose. In certain cases there is evidence to suggest that erosion of asbestos from pipe material is taking place. Age-standardized mortality rates for gastro-intestinal cancers were calculated for each city for the period of 1966 to 1976. Rates for the 2 localities with the highest (?10⁸/L) concentrations of asbestos fibres in treated drinking water were compared with the weighted average of the rates for the 52 localities with asbestos concentrations not significantly greater than zero. Eleven localities had intermediate concentrations of asbestos and six were too small for meaningful statistical analysis. Relatively high mortality rates were apparent amongst males in city 1 for cancer of the large intestine except rectum, and in both sexes in city 1 and males in city 2 for stomach cancer. It is felt that these findings are probably related to occupational exposure to asbestos. Further statistical analyses are required, however, before the significance of these observations can be fully assessed.     

建立饮用水水质监控预警系统——《饮用水水质监控预警及应急技术研究与示范项目》要点

建设监控预警系统的必要性改革开放以来,我国城市供水发展迅速,截至2008年底,655个设市城市和1615个县城供水设施规模、服务人口分别达到3.4亿m3/日、4.5亿人,比1978年提高了11.1倍和5.6倍。除部分县城和少数城市外,供水能力基本已经基本满足城市生活和生产用水需要。     

Lead in drinking water and health

This paper reviews recent findings and actions in the United Kingdom concerning lead in tap water and its biological effects, discusses some problems which arise with action to reduce exposure and outlines the limitations in the scientific evidence, with particular emphasis on the evidence concerning neuropsychological effects.     

Dynamics of drinking water biofilm in flow/non-flow conditions

Drinking water biofilm formation on polyvinyl chloride (PVC), cross-linked polyethylene (PEX), high density polyethylene (HDPE) and polypropylene (PP) was followed in three different reactors operating under stagnant or continuous flow regimes. After one week, a quasi-steady state was achieved where biofilm total cell numbers per unit surface area were not affected by fluctuations in the concentration of suspended cells. Metabolically active cells in biofilms were around 17-35% of the total cells and 6-18% were able to form colony units in R(2)A medium. Microbiological analysis showed that the adhesion material and reactor design did not affect significantly the biofilm growth. However, operating under continuous flow (0.8-1.9 Pa) or stagnant water had a significant effect on biofilm formation: in stagnant waters, biofilm grew to a less extent. By applying mass balances and an asymptotic biofilm formation model to data from biofilms grown on PVC and HDPE surfaces under turbulent flow, specific growth rates of bacteria in the biofilm were found to be similar for both materials (around 0.15 day(-1)) and much lower than the specific growth rates of suspended bacteria (around 1.8 day(-1)).     

Development and validation of a drinking water temperature model in domestic drinking water supply systems

Domestic drinking water supply systems (DDWSs) are the final step in the delivery of drinking water to consumers. Temperature is one of the rate-controlling parameters for many chemical and microbiological processes and is, therefore, considered as a surrogate parameter for water quality processes. In this study, a mathematical model is presented that predicts temperature dynamics of the drinking water in DDWSs. A full-scale DDWS resembling a conventional system was built and run according to one year of stochastic demands with a time step of 10 s. The drinking water temperature was measured at each point-of-use in the systems and the data-set was used for model validation. The temperature model adequately reproduced the temperature profiles, both in cold and hot water lines, in the full-scale DDWS. The model showed that inlet water temperature and ambient temperature have a large effect on the water temperature in the DDWSs.     

饮用水的臭氧氧化技术

通过介绍臭氧在饮用水处理中的应用，分析了臭氧处理系统的功能及其与污染物的反应机理。臭氧氧化技术与其他处理方法的联用在给水深度净化领域有十分广阔的应用前景。     

Nanofiltration in drinking water supply

The paper has presented an analytical review of the state of the art in scientific developments and technological solutions of nanofiltration in drinking water treatment. The article has shown the possibilities of nanofiltration and analyzed reasons restricting its wide-scale use in drinking water supply. It has covered new approaches to the solution of problems related to membrane fouling.     

Detection of microsporidia in drinking water, wastewater and recreational rivers

Diarrhea is the main health problem caused by human-related microsporidia, and waterborne transmission is one of the main risk factors for intestinal diseases. Recent studies suggest the involvement of water in the epidemiology of human microsporidiosis. However, studies related to the presence of microsporidia in different types of waters from countries where human microsporidiosis has been described are still scarce. Thirty-eight water samples from 8 drinking water treatment plants (DWTPs), 8 wastewater treatment plants (WWTPs) and 6 recreational river areas (RRAs) from Galicia (NW Spain) have been analyzed. One hundred liters of water from DWTPs and 50 L of water from WWTPs and RRAs were filtered to recover parasites, using the IDEXX Filta-Max® system.Microsporidian spores were identified by Weber’s stain and positive samples were analyzed by PCR, using specific primers for Enterocytozoon bieneusi, Encephalitozoon intestinalis, Encephalitozoon cuniculi, and Encephalitozoon hellem. Microsporidia spores were identified by staining protocols in eight samples (21.0%): 2 from DWTPs, 5 from WWTPs, and 1 from an RRA. In the RRA sample, the microsporidia were identified as E. intestinalis.To the best of our knowledge, this is the first report of human-pathogenic microsporidia in water samples from DWTPs, WWTPs and RRAs in Spain. These observations add further evidence to support that new and appropriate control and regulations for drinking, wastewater, and recreational waters should be established to avoid health risks from this pathogen.     

A bioassay application for quantitative toxicity measurements, using the green algae Selenastrum capricornutum

This method, for use in the laboratory, requires a sample of only one litre, and is based on the measurement of growth inhibition of the unicellular alga Selenastrum capricornutum Printz. The assay involves making several dilutions in triplicate, enriching them with a known quantity of nutrients, and then introducing algae and incubating them until they reach the maximum standing crop. The resulting biomass is then compared with the theoretical biomass for each concentration, and the observed percentages of growth inhibition are plotted on “log-probit” graph paper to obtain the straight line of toxicity and from that the value of IC 50 (the concentration which inhibits algae growth by 50%); this value enables us to obtain an absolute measure of toxicity, expressed as a number of toxic units.