Bacterial communities in sediments of a drinking water reservoir

Sediment microbial communities play crucial roles in biogeochemical cycles of aquatic systems. Knowledge of microbial community structure could aid in our understanding of these roles. In this study, the sediment bacterial community structure of a drinking water reservoir in China was investigated. A large difference in major bacterial groups was observed at different sampling sites. Proteobacteria was the largest bacterial phylum, with a marked shift in the proportions of its major subdivisions. Microorganisms within phylum Proteobacteria might play important roles in various biogeochemical processes.     

Microbial load of drinking water reservoir tributaries during extreme rainfall and runoff

Hygienic and microbiological examinations of watercourses are usually not carried out during heavy rainfall and runoff events. After rainfall or snowmelt, there are often massive increases in turbidity in flooding creeks in mountain ranges, which are frequently interpreted as an indication of microbial contamination. The aim of this study was to quantify the microbial loads of watercourses during such runoff events and to compare these loads with loads occurring during regular conditions. In a 14-month monitoring period we investigated the microbial loads of three tributaries of different drinking water reservoirs. A total of 99 water samples were taken under different runoff conditions and analyzed to determine physical, chemical, bacterial, and parasitic parameters. Thirty-two water samples were considered event samples during nine measuring series. The criteria for events, based on duration and intensity of precipitation, water depth gauge measurements, and dynamics, had been fixed before the investigation for each creek individually. Of the physical and chemical parameters examined, only the turbidity, pH, and nitrate values differed clearly from the values obtained for regular samples. Most of the bacteriological parameters investigated (colony, Escherichia coli, coliform, fecal streptococcal, and Clostridium perfringens counts) increased considerably during extreme runoff events. If relevant sources of parasitic contamination occurred in catchment areas, the concentrations of Giardia and Cryptosporidium rose significantly during events. The results show that substantial shares of the total microbial loads in watercourses and in drinking water reservoirs result from rainfall and extreme runoff events. Consequently, regular samples are considered inadequate for representing the microbial contamination of watercourse systems. The procedures for raw water surveillance in the context of multiple-barrier protection and risk assessment ought to include sampling during extreme runoff situations.     

Detection of activity among uncultured Actinobacteria in a drinking water reservoir

The abundance, identity and activity of uncultured Bacteria and Actinobacteria present in a drinking water reservoir (North Pine Dam, Brisbane, Australia) were determined using a combination of fluorescence in situ hybridization (FISH) alone or with catalysed reporter deposition (CARD-FISH) with microautoradiography. The CARD-FISH technique was modified relative to previous described procedures and performed directly on gelatine cover slips in order to allow simultaneous combination with microautoradiography. Almost twofold higher numbers of microorganisms could be identified as either Bacteria or Actinobacteria using the CARD-FISH technique as compared with the traditional FISH technique. A combination of FISH or CARD-FISH with microautoradiography showed generally higher activity among the Actinobacteria than among all Bacteria. Another important observation was that many cells within the FISH-negative populations of both Actinobacteria and Bacteria were actively assimilating thymidine. Thus, great care should be taken when extrapolating the active fraction of a prokaryotic community to be equivalent to the FISH-detectable population in such environments. Bacterial groups within Actinobacteria produce the odours geosmin and 2-methylisoborneol, which lower the quality of surface water when used for drinking. The results indicate that combined microautoradiography and CARD-FISH may serve as an effective tool when studying identity and activity of microorganisms within freshwater environments.     

Biosorptive removal of arsenic from drinking water

A biomass derived from the plant Momordica charantia has been found to be very efficient in arsenic(III) adsorption. An attempt was made to use this biomass for arsenic(III) removal under different conditions. The parameters optimized were contact time (5-150 min), pH (2-11), concentration of adsorbent (1-50 g/l), concentration of adsorbate (0.1-100mg/l), etc. It was observed that the pH had a strong effect on biosorption capacity. The optimum pH obtained for arsenic adsorption was 9. The influence of common ions such as Ca(2+), Mg(2+), Cd(2+), Se(4+), Cl(-), SO(4)(2-), and HCO(3)(-), at concentrations varying from 5 to 1000 mg/l was investigated. To establish the most appropriate correlation for the equilibrium curves, isotherm studies were performed for As(III) ion using Freundlich and Langmuir adsorption isotherms. The pattern of adsorption fitted well with both models. The biomass of M. charantia was found to be effective for the removal of As(III) with 88% sorption efficiency at a concentration of 0.5mg/l of As(III) solution, and thus uptake capacity is 0.88 mg As(III)/gm of biomass. It appears that this biomass should be used as a palliative food item. Further it also appears that the dietary habits may play a role in the toxic effects of ingested arsenic.     

Characterization of Aeromonas and Vibrio species isolated from a drinking water reservoir

AIMS: To study the phenotypic and chemotaxonomic (i.e. phospholipid and cellular fatty acid composition) characteristics of environmental Aeromonas spp. and Vibrio spp. isolated from a drinking water reservoir near Vladivostok City, and the application of some chemotaxonomic markers for discrimination of the two genera and species. METHODS AND RESULTS: Presumptive Aeromonas species were dominant in surface water samples (up to 25% of the total number of bacteria recovered). These strains were consistent with respect to the cultural and biochemical properties used to define the species Aeromonas sobria (seven strains) and Aer. popoffii (three strains). Vibrio mimicus (two strains) and Vibrio metschnikovii (one strain) were identified according to phenotypic features and cellular fatty acid composition. CONCLUSION: Environmental Aer. sobria isolates were atypical in their ability to grow at 42 degrees C, and were haemolytic, proteolytic and cytotoxic. Although it was present in a high proportion in the water samples, atypical Aer. sobria is not an indicator of polluted water. SIGNIFICANCE AND IMPACT OF THE STUDY: The incidence of Aeromonas in the drinking water reservoirs in the Far East of Russia is reported for the first time.     

Nitrate removal from drinking water in a fluidized-bed biological denitrification bioreactor

In most industrially developed countries an increasing degree of nitrification can be observed in potential water reservoirs. High nitrate content is unacceptable by public health standards. Since contamination seems to be unavoidable, the only realistic solution is purification prior to utilization. One of the potential variations is biological denitrification with a highly intensive facility, a fluidized- or expanded-bed bioreactor. Based on laboratory and pilot plant experiments, a detailed analysis is presented on the problems arising and solutions offered in the construction of a purification system meeting high quality requirements of drinking water purification. The crucial point is selection of the denitrifying microorganisms and organic matter required for denitrification, which simultaneously determines the attachment of bacteria to the support material (autoimmobilization), the intensity of nitrate removal and the character of post-purification.     

Nitrate removal from drinking water using a membrane-fixed biofilm reactor

Biological treatment of drinking water is a cost-effective alternative to conventional physico/chemical processes. A new concept was tested to overcome the main disadvantage of biological denitrification, the intensive post-treatment process to remove microorganisms and remnant carbon source. The biological reaction zone and carbon supply were separated from the raw water stream by a nitrate-permeable membrane. Denitrification takes place in a biofilm, which is immobilized at the membrane. In a series of bench-scale runs, different types of membranes and reactor configurations were investigated. The best denitrification rates achieved were 1230 mg NO₃ ⁻-N m⁻² day⁻¹. In one run, raw water containing 100 mg NO₃ ⁻ l⁻¹ was completely freed from nitrate. The membrane and the attached biofilm also represent a barrier against the passage of the C source and nutrients into the raw water. At concentrations of 20 mg l⁻¹ ethanol and 15 mg l⁻¹ phosphate in the bioreactor no diffusion through the membrane into the treated water was observed. Without any post-treatment, the effluent met nearly all the relevant criteria for drinking water; only the colony count was slightly increased. Received: 18 December 1996 / Received last revision: 14 April 1997 / Accepted: 19 April 1997     

Biofilms in drinking water systems: a possible reservoir for Helicobacter pylori

A laboratory model system was utilised to investigate the persistence of Helicobacter pylori in mixed-species heterotrophic biofilms. A single-stage continuous culture vessel was linked to a modified-Robbins device (mRD) incorporating removable stainless steel coupons. The system was innoculated with H. pylori (NCTC 11637) and the fate of the organism monitored by polymerase chain reaction (PCR) analysis. Helicobacter pylori was detected in biofilm material for a period of up to 192 h. Theoretical washout would have occurred at around 48 h thus detection of H. pylori for a prolonged period after theoretical washout suggested that the organism possessed the ability to persist in the mixed-species heterotrophic biofilm. Preliminary studies using heat-inactivated H. pylori showed that the organism was not detected in biofilm material at any time post-challenge suggesting that the persistence of H. pylori in such material was a phenomenon requiring the organism to be in a viable state. Further investigations to assess the biological basis for the association of H. pylori with drinking water biofilms and the risk that this may pose to public health are being undertaken.     

Phytoplankton community of the drinking water supply reservoir Borovitsa (South Bulgaria) with an emphasis on cyanotoxins and water quality

The phytoplankton diversity, algal biomass, and selected physicochemical parameters were investigated in the drinking water reservoir (Borovitsa) located in the Kardzhali region, Bulgaria. Particular attention was given to Cyanoprokaryota and presence of cyanotoxins in the water samples. Twenty-nine species belonging to six divisions (Cyanoprokaryota, Chlorophyta, Zygnemophyta, Dinophyta, Euglenophyta and Bacillariophyta) were identified. The microscopic examination of the phytoplankton samples showed the dominance of Ankyra judayi, Oocystis lacustris (Chlorophyta) and Aphanizomenon flos-aquae (Cyanoprokaryota) in July 2006, and Microcystis pulverea, Synechococcus elongatus (Cyanoprokaryota), Radiococcus planktonicus (Chlorophyta) and Melosira varians (Bacillariophyta) in September 2006. A blooming event due to Aphanizomenon flos-aquae was observed in July 2006. The reservoir exhibits a tendency to shift from an oligotrophic environment to a state of mesotrophy. Presence of cyanotoxins such as anatoxin-a, microcystins and saxitoxins were analyzed by HPLC and ELISA methods. Our results demonstrated the presence of anatoxin-a and microcystins (0.09 μg/L) in the raw water samples from July 2006, and saxitoxins (2.5 μg/L) and microcystins (0.18 μg/L) in the raw water samples from September 2006. The study underlines that permanent monitoring programs of Cyanoprokaryota in the reservoirs used as sources of drinking water and toxicity assessments should be implemented. Indirect exposure and transfer of cyanotoxins through food chains must also be considered.     

饮用水处理流程中的微藻及其去除率

为了解某市饮用水处理流程中的藻类状况,对某市饮用水源及自来水厂各主要处理过程中的水样进行藻类检测鉴定。在各水样中共检测到藻类72种,蓝藻、绿藻和硅藻为优势藻群,并检出微囊藻、颤藻和鱼腥藻等潜在产毒的种类,其中微囊藻在源水中的细胞密度为1.9×106cell·L-1。源水中藻类细胞密度为2.8×106cell·L-1,处理后自来水中藻类的细胞密度为4.6×104cell·L-1,藻类总去除率为98.3%,其中滤池对藻类的去除率为82.7%,但其对蓝藻的去除率仅为11.8%。研究结果表明,该市水源可能已受到藻毒素的污染;现有自来水处理工艺中的滤池难以对个体较小的有毒蓝藻有效去除。针对该地区水源藻类的分布情况提出了优化过滤工艺的建议。     

Membrane bioreactors for the removal of anionic micropollutants from drinking water

Biological treatment processes allow for the effective elimination of anionic micropollutants from drinking water. However, special technologies have to be implemented to eliminate the target pollutants without changing water quality, either by adding new pollutants or removing essential water components. Some innovative technologies that combine the use of membranes with the biological degradation of ionic micropollutants in order to minimize the secondary contamination of treated water include pressure-driven membrane bioreactors, gas-transfer membrane bioreactors and ion exchange membrane bioreactors.     

Assessment of water quality in groundwater resources of Iran using a modified drinking water quality index (DWQI)

An innovative drinking water quality index (DWQI) based on the Canadian DWQI was developed as “modified DWQI” and applied for assessing the water quality in all of the groundwater resources that are used as the source of drinking water in urban areas of Iran in 2011. Assignment of weight factors for input parameters was the modification carried out in the DWQI. In development of the modified DWQI, twenty-three water quality parameters and relevant Iranian standards for drinking water quality were selected as input parameters and benchmarks, respectively. The modified DWQI is calculated for each sampling station over one year using three factors: the number of parameters that excurse benchmarks, the number of measurements in a dataset that excurse benchmarks and the magnitude of excursion from benchmarks in the violator measurements. The modified DWQI contains two sub-indices: health-based index as “modified HWQI” and acceptability index as “modified AWQI”. The modified DWQI and its sub-indices scores range from 0 to 100 and classify water quality in five categories as poor, marginal, fair, good and excellent, respectively. The results of the case study revealed that the nationwide average scores of the modified DWQI, HWQI and AWQI in the groundwater resources were 85, 79 and 91, respectively and overall situation of water quality in the groundwater resources was described as good. According to the modified DWQI value, about 95% of the groundwater flowrates were in the good condition, also in 3 and 2% of the groundwater flowrates, water quality was determined to be fair and marginal, respectively. This study indicated that the modified DWQI and its sub-indices could describe the overall water quality of water bodies easily, reliably and correctly and have the potential suitability for extensive application all over the world.     

Microbiological quality of drinking water from dispensers in Italy

Background  

Water coolers are popular in office buildings and commercial stores and the quality of this source of drinking water has the potential to cause waterborne outbreaks, especially in sensitive and immunocompromised subjects. The aim of this study was to determine the quality of water plumbed in coolers from commercial stores in comparison with tap water in Italy.     

Case study of complaints on drinking water quality

Several families of Talca city, Chile complained to health authorities for what they attributed to consumption of copper (Cu)-contaminated drinking water. We assessed the situation 6–12 mo after the initiation of complaints by characterizing the symptoms reported, the chemistry of drinking water, and the Cu concentration in stagnant drinking water. After completing a census, 1778 households accepted participation and were categorized as follows: category 1, Cu plumbing for tap water and dwellers reporting health complaints (HC); category 2, Cu plumbing for tap water and dwellers reporting no HC; category 3, plastic plumbing for tap water and dwellers reporting no HC. Questionnaires recorded characteristics of households and symptoms presented by each member of the family in the last 3 mo. The Cu concentration in drinking water was measured in a subsample of 80 homes with Cu pipes. In category 1, participants presented significantly more abdominal pain, diarrhea, and/or vomiting (gastrointestinal [GI] symptoms) in comparison to category 3 and to categories 2 plus 3. The stagnant Cu concentrations measured in drinking water in all houses studied were below the US Environmental Protection Agency guideline value (<1.3 mg Cu/L). In summary, data obtained by interviews suggested that individuals in some areas of Talca city were suffering more GI symptoms potentially related to Cu excess, but measurement of Cu concentration in stagnant tap waters ruled out the association between Cu exposure and GI symptom reports at the time of this study. The dose-response curves for GI symptoms and Cu exposure now available were crucial in the analyses of results.     

董铺水库水质及营养水平生物学评价

2003年7月到2004年6月对董铺水库的浮游生物进行了调查,对其种类组成、生物量、种群数量、污染指标种等相关指数进行了初步分析,得出结果是综合指数为1.46,种群数量为2.256×105个/升(浮游植物),多样性指数的值在3.01~3.22之间。这些指数表明:目前董铺水库的水质仍属清洁水体,从营养水平来看处于贫营养与中营养之间,并向中营养水平演化,水质存在着向轻度污染转化的趋势。     

Phytoremediation: green technology for the removal of mixed contaminants of a water supply reservoir

The Iraí Reservoir, a water supply in Brazil, is constantly impacted by anthropogenic activities such as waste inputs from agriculture, hospitals and urbanization, resulting toxic cyanobacterial blooms causing economic, social and environmental problems. This study assessed the concentration of some common contaminants of the Iraí Reservoir, namely paracetamol, diclofenac and microcystin-LR and tested whether a laboratory scale Green Liver System^® would serve as a suitable technology to remove these contaminants. Further, the study investigated whether the pollutants caused adverse effects to the macrophytes using catalase as a biomarker for oxidative stress and investigated whether biotransformation (glutathione S-transferase) was a main route for detoxification. Egeria densa, Ceratophyllum demersum and Myriophyllum aquaticum were exposed to a mixture of the three contaminants for 14?days in a concentration range similar to those detected in the reservoir. The plants removed 93% of diclofenac and 100% of MC-LR after 14?days. Paracetamol could not be detected. Catalase and glutathione S-transferase enzyme activities remained unaltered after the 14-day exposure, indicating that the mixture did not cause oxidative stress. The study showed that the aquatic macrophytes used are suitable tools to apply in a Green Liver System^® for the remediation of mixed pollutants.     

Heterotrophic microorganisms and viruses in the water of the Gorky reservoir during a period of anomalously high water temperature

During the anomalously hot summer of 2010, the water temperature in the Gorky reservoir reached 27–33°C. Pronounced cyanobacterial blooms occurred in the limnetic part of the reservoir. The average values for bacterioplankton abundance (11.58 ± 1.25 × 10⁶ cell/mL), biomass (886 ± 96 mg/m³), and production [169 ± 32 mg C/(m³ day)] were twice as high as in the year with temperatures comparable to long-term average values. These parameters were higher in the limnetic part than in the river one. The abundance (4.86 ± 0.75 × 10³ cell/mL) and biomass (138 ± 9 mg/m³) of heterotrophic nanoflagellates were 2.3 and 1.7 times higher, respectively, than in years with regular temperature regimes. The average number of plank-tonic viral particles (N _v) in 2010 was 48.89 ± 9.54 × 10⁶ particles/mL, while virus-induced bacterial mortality (VMB) accounted for 26.9 ± 4.6% of the bacterial production. The N _v and VMB values in the limnetic part of the reservoir were, respectively, 1.5 and 1.8 times higher than in the river one.