The need for an integrated approach to water-supply and sanitation in developing countries

During the coming decade much greater emphasis will be placed in developing countries on groundwater exploitation for drinking water-supplies and on unsewered sanitation. In certain hydrogeological conditions these low cost technologies may be in conflict and an integrated approach is required to avoid new pollution hazards. This paper briefly reviews the factors influencing the survival and migration of faecal bacteria and viruses in groundwater systems, assesses the threat of chemical pollution, and identifies the critical factors in the evaluation of groundwater pollution risk.     

Optimal preparation and purification of PRD1-like bacteriophages for use in environmental fate and transport studies

Bacteriophages are bacterial viruses with unique characteristics that make them excellent surrogates for mammalian pathogenic viruses in environmental studies. Simple and reliable methodologies for isolation, detection, characterization and enumeration of somatic and F-specific bacteriophage are available in the literature. Limited information or methods are available for producing high-titer purified phage suspensions for studying microbial transport and survival in natural and engineered environments. This deficiency arises because most research on the production of high-titer phage suspensions was completed over half a century ago and more recent advances on these methods have not been compiled in a single publication. We present a review of the available methods and new data on the propagation, concentration and purification of two bacteriophage host systems (somatic PRD1/Salmonella thyphimurium and F-specific PR772/Escherichia coli) that are commonly utilized in laboratory and field-scale assessments of subsurface microbial transport and survival. The focus of the present study is to recommend the approach(es) that will ensure maximum bacteriophage yields while optimizing suspension purification (i.e. avoiding modification of surface charge of the phage capsids and/or inadvertent introduction of dissolved organic matter to the study system).     

Molecular detection of pathogens in water - The pros and cons of molecular techniques

Pollution of water by sewage and run-off from farms produces a serious public health problem in many countries. Viruses, along with bacteria and protozoa in the intestine or in urine are shed and transported through the sewer system. Even in highly industrialized countries, pathogens, including viruses, are prevalent throughout the environment. Molecular methods are used to monitor viral, bacterial, and protozoan pathogens, and to track pathogen- and source-specific markers in the environment. Molecular techniques, specifically polymerase chain reaction-based methods, provide sensitive, rapid, and quantitative analytical tools with which to study such pathogens, including new or emerging strains. These techniques are used to evaluate the microbiological quality of food and water, and to assess the efficiency of virus removal in drinking and wastewater treatment plants. The range of methods available for the application of molecular techniques has increased, and the costs involved have fallen. These developments have allowed the potential standardization and automation of certain techniques. In some cases they facilitate the identification, genotyping, enumeration, viability assessment, and source-tracking of human and animal contamination. Additionally, recent improvements in detection technologies have allowed the simultaneous detection of multiple targets in a single assay. However, the molecular techniques available today and those under development require further refinement in order to be standardized and applicable to a diversity of matrices. Water disinfection treatments may have an effect on the viability of pathogens and the numbers obtained by molecular techniques may overestimate the quantification of infectious microorganisms. The pros and cons of molecular techniques for the detection and quantification of pathogens in water are discussed.     

Effects of pH, ionic strength, dissolved organic matter, and flow rate on the co-transport of MS2 bacteriophages with kaolinite in gravel aquifer media

Viruses are often associated with colloids in wastewater and could be transported with colloids into groundwater from land disposal of human and animal effluent and sludge, causing contamination of groundwater. To investigate the role of colloids in the transport of viruses in groundwater, experiments were conducted using a 2 m long column packed with heterogeneous gravel aquifer media. Bacteriophage MS2 was used as the model virus and kaolinite as the model colloid. Experimental data were analyzed using Temporal Moment Analysis and Filtration Theory. In the absence of kaolinite colloid, MS2 phage traveled slightly faster than the conservative tracer bromide (Br), with little differences observed between unfiltered and filtered MS2 phage (0.22 μm as the operational cut-off for colloid-free virus). In the presence of kaolinite colloids, MS2 phage breakthrough occurred concurrently with that of the colloidal particles and the time taken to reach the peak virus concentration was reduced, suggesting a colloid-facilitated virus transport in terms of peak-concentration time and velocity. Meanwhile mass recovery and magnitude of concentrations of the phages were significantly reduced, indicating colloid-assisted virus attenuation in terms of concentrations and mass. Decreasing the pH or increasing the ionic strength increased the level of virus attachment to the aquifer media and colloids, and virus transport became more retarded, resulting in lower peak-concentration, lower mass recovery, longer peak-concentration time, and greater apparent collision efficiency. Increasing the concentration of dissolved organic matter (DOM) or flow rate resulted in faster virus transport velocity, higher peak-concentrations and mass recoveries, and lower apparent collision efficiencies. The dual-role of colloids in transport viruses has important implications for risk analysis and remediation of virus-contaminated sites.     

CFD simulation of airborne pathogen transport due to human activities

Computational Fluid Dynamics (CFD) is an increasingly popular tool for studying the impact of design interventions on the transport of infectious microorganisms. While much of the focus is on respiratory infections, there is substantial evidence that certain pathogens, such as those which colonise the skin, can be released into, and transported through the air through routine activities. In these situations the bacteria is released over a volume of space, with different intensities and locations varying in time rather than being released at a single point.     

Transport and deposition of sediment-associated Escherichia coli in natural streams

The association of microorganisms with sediment particles is one of the primary complicating factors in assessing microbial fate in aquatic systems. The literature indicates that the majority of enteric bacteria in aquatic systems are associated with sediments and that these associations influence their survival and transport characteristics. Yet, the nature of these associations has not been fully characterized. In this study, a combination of field experiments and mathematical modeling were used to better understand the processes which control the fate and transport of enteric bacteria in alluvial streams. An experimental procedure, involving the use of a tracer-bacteria, was developed to simulate the transport and deposition of bacteria-laden bed sediments in a small alluvial stream during steady flow conditions. The experimental data and mathematical model were used to determine dispersion coefficients, deposition rates, and partitioning coefficients for sediment-associated bacteria in two natural streams. The results provided evidence that bacterial adsorption can be modeled as an irreversible process in freshwater environments. Net settling velocities of fine sediments and associated bacteria were typically two orders of magnitude lower than those predicted from Stokes equation, due to re-entrainment of settled particles. The information presented in this study will further the development of representative microbial water quality models.     

Groundwater quality in the netherlands — collection and interpretation of data

In The Netherlands many groundwater quality data are available. At the same time, much research is being done on groundwater quality and groundwater pollution. This paper deals with problems of interpretation of groundwater quality data related to hydrogeological conditions, location of boreholes and sample handling. Attention will be paid to the quality of groundwater in The Netherlands.     

基于山区水文地质条件下燃煤电厂贮灰场地下水生态环境影响预测

基于我国以煤炭为主的能源结构,火力发电厂仍然在发电领域占有绝对的统治地位。但与此同时,火力发电的副产品粉煤灰堆放问题日益成为社会性问题。由于京津冀地区空气和地下水污染防控的巨大压力,环保问题成为困扰电厂灰场的一大问题。通过对石家庄井陉某大型火力发电厂灰场(灰渣体积31×10~4m^3)的地下水资料收集、现场调查、水质检测、数据分析预测,对井陉地区水文地质条件进行模型概化,用数值模拟的方法预测灰场特征污染物氟化物和六价铬的污染运移情况,探讨分析了灰场污染物泄漏进入地下水环境的迁移范围和影响程度,认为该灰场地下水对周边环境影响很小,从而对灰场的地下水生态环境保护提供指导作用。     

Effect of Antarctic solar radiation on sewage bacteria viability

The majority of coastal Antarctic research stations discard untreated sewage waste into the near-shore marine environment. However, Antarctic solar conditions are unique, with ozone depletion increasing the proportion of potentially damaging ultraviolet-B (UV-B) radiation reaching the marine environment. This study assessed the influence of Antarctic solar radiation on the viability of Escherichia coli and sewage microorganisms at Rothera Research Station, Adelaide Island, Antarctic Peninsula. Cell viability decreased with increased exposure time and with exposure to shorter wavelengths of solar radiation. Cell survival also declined with decreasing cloud cover, solar zenith angle and ozone column depth. However, particulates in sewage increased the persistence of viable bacteria. Ultraviolet radiation doses over Rothera Point were highest during the austral summer. During this time, solar radiation may act to partially reduce the number of viable sewage-derived microorganisms in the surface seawater around Antarctic outfalls. Nevertheless, this effect is not reliable and every effort should be made to fully treat sewage before release into the Antarctic marine environment.     

Virus survival in solid waste leachates

Disposal of domestic solid waste either in open dumps or in sanitary landfills results in leachates which may find their way into groundwater aquifers. This study is concerned with the survival of microorganisms of sanitary significance, with particular emphasis on enteric viruses, in leachates produced by model disposal systems. Data are presented that indicate the presence of considerable amounts of human and animal feces in fresh domestic refuse. Significant numbers of coliforms, fecal coliforms, and fecal streptococci are present in refuse and also persist for weeks in the leachates produced.A method for the concentration and recovery of virus from relatively large volumes of leachate is evaluated. Viruses were sporadically recovered for periods up to 20 weeks from leachates generated by systems to which poliovirus was purposely introduced as well as from control systems. The leachates produced were shown not to be acutely toxic to poliovirus.     

The effect of surface characteristics on the transport of multiple Escherichia coli isolates in large scale columns of quartz sand

Bacteria properties play an important role in the transport of bacteria in groundwater, but their role, especially for longer transport distances (>0.5 m) has not been studied. Thereto, we studied the effects of cell surface hydrophobicity, outer surface potential (OSP), cell sphericity, motility, and Ag43 protein expression on the outer cell surface for a number of E. coli strains, obtained from the environment on their transport behavior in columns of saturated quartz sand of 5 m height in two solutions: demineralized (DI) water and artificial groundwater (AGW). In DI water, sticking efficiencies ranged between 0.1 and 0.4 at the column inlet, and then decreased with transport distance to 0.02-0.2. In AGW, sticking efficiencies were on average 1 log-unit higher than those in DI (water). Bacteria motility and Ag43 expression affected attachment with a (high) statistical significance. In contrast, hydrophobicity, OSP and cell sphericity did not significantly correlate with sticking efficiency. However, for transport distances more than 0.33 m, the correlation between sticking efficiency, Ag43 expression, and motility became insignificant. We concluded that Ag43 and motility played an important role in E. coli attachment to quartz grain surfaces, and that the transport distance dependent sticking efficiency reductions were caused by motility and Ag43 expression variations within a population. The implication of our findings is that less motile bacteria with little or no Ag43 expression may travel longer distances once they enter groundwater environments. In future studies, the possible effect of bacteria surface structures, like fimbriae, pili and surface proteins on bacteria attachment need to be considered more systematically in order to arrive at more meaningful inter-population comparisons of the transport behavior of E. coli strains in aquifers.     

Carbamazepine as a possible anthropogenic marker in the aquatic environment: investigations on the behaviour of Carbamazepine in wastewater treatment and during groundwater infiltration

Sewage treatment plant (STP) effluents are significant sources of pharmaceutical residues in surface waters, where high concentrations of the antiepileptic drug Carbamazepine have been detected. The solids retention time (SRT) is the most important parameter for the design of STPs. It relates to the growth rate of microorganisms and to effluent concentrations. The influence of SRT on the removal of Carbamazepine was studied on lab-scale plants. The results from these tests were then validated on several full-scale plants. Due to the lack of suitable receiving waters and groundwater resources, one of these STPs has to infiltrate the treated wastewater into unsaturated soil. Here, groundwater samples at equal distances from the infiltration point were taken to estimate the behaviour of Carbamazepine during soil passage and within the groundwater. This antiepileptic drug seems to be very persistent in the environment, therefore qualifying as a suitable marker for anthropogenic influences in the aquatic environment.     

Plant viruses in aqueous environment - Survival, water mediated transmission and detection

The presence of plant viruses outside their plant host or insect vectors has not been studied intensively. This is due, in part, to the lack of effective detection methods that would enable their detection in difficult matrixes and in low titres, and support the search for unknown viruses. Recently, new and sensitive methods for detecting viruses have resulted in a deeper insight into plant virus movement through, and transmission between, plants. In this review, we have focused on plant viruses found in environmental waters and their detection. Infectious plant pathogenic viruses from at least 7 different genera have been found in aqueous environment. The majority of the plant pathogenic viruses so far recovered from environmental waters are very stable, they can infect plants via the roots without the aid of a vector and often have a wide host range. The release of such viruses from plants can lead to their dissemination in streams, lakes, and rivers, thereby ensuring the long-distance spread of viruses that otherwise, under natural conditions, would remain restricted to limited areas.The possible sources and survival of plant viruses in waters are therefore discussed. Due to the widespread use of hydroponic systems and intensive irrigation in horticulture, the review is focused on the possibility and importance of spreading viral infection by water, together with measures for preventing the spread of viruses. The development of new methods for detecting multiple plant viruses at the same time, like microarrays or new generation sequencing, will facilitate the monitoring of environmental waters and waters used for irrigation and in hydroponic systems. It is reasonable to expect that the list of plant viruses found in waters will thereby be expanded considerably. This will emphasize the need for further studies to determine the biological significance of water-mediated transport.     

建筑排水立管内微生物组成及特性分析

排水立管肩负输送、排放污废水的功能,与我们的生活密切相关。但排水管道内壁易附着污物,滋生细菌,产生生物膜,生物膜可能包含各式各样的微生物,有些微生物在排水管道中会产生臭气甚至有毒有害气体,这些气体若进入室内则会污染室内环境卫生,危害人体健康。本文通过实地采集了排水立管内的生物膜,研究了其生物相及采用菌种分离的方法培养确定了常见建筑排水立管内微生物的种类及数量,同时分析排水立管内的生物相及可能产生的危害,为室内环境的保护提供基础数据和针对性的改善措施。     

基于混菌产电微生物燃料电池的最新研究进展

混菌微生物燃料电池(MFC)是直接利用环境中多种微生物附着于阳极而产电的方式,相对于纯菌MFC的前期菌种培养和富集,混菌电池的启动不仅省时且更节约成本,同时其抗环境冲击的能力也更强,电池稳定性更高。介绍了混菌MFC的最新研究现状,详细讨论了产电微生物的种类、电子传递机制、影响混菌MFC产电效能的主要因素,以及目前存在的问题等,并指出了混菌MFC的未来研究重点和方向。     

Statistical assessment of the accuracy and precision of bacteria- and virus-sized microsphere enumerations by epifluorescence microscopy

Fluorescent microspheres are increasingly used in environmental studies to evaluate threats of viral and bacterial pathogens in drinking water and to investigate colloid-facilitated contaminant transport. A commonly accepted technique for the enumeration of viruses, bacteria, and virus- and bacteria-sized particles by microscopy involves a field-of-view (field) approach to estimate concentration. Few studies have focused on those factors that are most important in ensuring precise and accurate measures of concentration. Microsphere counts in suspensions of artificial groundwater and deionized water were contrasted in this study to gain a greater understanding of the effect of ionic strength and the presence of precipitates in groundwater matrices that can bias microsphere enumerations. To investigate microsphere enumeration with minimal bias from other factors, a commonly used standard method was used to prepare slides and enumerate microspheres, with particular care to randomly select fields for counting. A factorial experiment evaluated two factors, (1) the density of microspheres in each field and (2) the number of counts in an enumeration. Two parameters, relative standard deviation and percent error, were used to assess methodological precision and accuracy. Visual observations of the slides indicated that some biases, such as undulation in the filter membrane or bubble entrained in the mounting medium, create biases in microsphere enumeration. Additional biases were introduced by the presence of precipitates that form in artificial groundwater saturated with calcite. Microsphere density was found to be critical for ensuring methodological precision, whereas the total number of microspheres counted was essential to ensuring methodological accuracy. The results suggested that to minimize variability using the field approach, the enumeration of at least 350 microspheres and 25-40 microspheresfield (-1) is necessary.     

氮污染地下水的原位修复试验研究

将人工脱氮菌剂分别与乙醇、乙酸钠、葡萄糖、白糖等组合应用，开展了对受NO3^- -N污染地下水的原位修复试验研究。结果表明，当采用乙醇、乙酸钠作为碳源时可对地下水中的NO3^- -N污染产生明显的去除效果，但由于地下水的自然渗流缓慢，导致投入物与地下水体的交换性能较差，对污染物的净化总量不大。对此可采取如下措施：在污染区中心至边缘的范围内实施人工抽水与注水。伴随注水按一定比例连续投加碳源，同时间歇投加人工脱氮菌剂。经此改进后可大大改善所投加营养物与地下水体的交换性能，取得更好的污染治理效果。     

Fates of bacteriophages and bacterial indicators in the Moselle river (France)

It has been suggested that bacteriophages can provide useful information about the pathogenic microorganisms, particularly enteric viruses, present in water. This information is complementary to that obtained from bacterial indicators of faecal contamination, which would be of great value for evaluating the risks associated with the use of certain types of water. Before bacteriophages can be used as indicators of faecal contamination, we need to confirm that bacteriophages give a different response to that given by the well-known bacteria indicators and to determine what happens to bacteriophages in river water. Indeed, drinking water is often produced from river water, either by natural filtration through the soil or after undergoing various treatments. We collected 96 river water samples from six different sites between February and November 2000. The samples were analysed for three faecal indicator bacteria (thermotolerant coliforms, enterococci and spores of sulphite-reducing anaerobes) and three types of bacteriophages (somatic coliphages, F-specific phages and Bacteroides fragilis phages). The densities of thermotolerant coliforms and enterococci depended mainly on physical factors such as flow rate and water temperature. High temperature and low flow rate led to a decrease in the density of these microorganisms, especially in the absence of a major input of faecal pollution. Conversely, the densities of somatic coliphages, F-specific phages and spores of sulphite-reducing anaerobes remained constant regardless of the flow rate and temperature. The density of Bacteroides fragilis phages was too low for unambiguous determination of their fate in river water.