Detection of enteroviruses in untreated and treated drinking water supplies in South Africa

Enteric viruses have been detected in many drinking water supplies all over the world. A meaningful number of these supplies were treated and disinfected according to internationally acceptable methods. In addition, counts of bacterial indicators (coliform bacteria and heterotrophic plate count organisms) in these water supplies were within limits generally recommended for treated drinking water and these findings have been supported by epidemiological data on infections associated with drinking water. The shortcomings of conventional treatment methods and indicator organisms to confirm the absence of enteric viruses from drinking water, was generally ascribed to the exceptional resistance of these viruses. In this study, the prevalence of enteroviruses detected from July 2000 to June 2002 in sewage, river-, borehole-, spring- and dam water as well as drinking water supplies treated and disinfected according to international specifications for the production of safe drinking water was analysed. A glass wool adsorption-elution technique was used to recover viruses from 10--20 l of sewage as well as environmental water samples, in the case of drinking water from more than 100 l. Recovered enteroviruses were inoculated onto two cell culture types (BGM and PLC/PRF/5 cells) for amplification of viral RNA with nested-PCR being used to detect the amplified viral RNA. Results from the study demonstrated the presence of enteroviruses in 42.5% of sewage and in 18.7% of treated drinking water samples. Furthermore, enteroviruses were detected in 28.5% of river water, in 26.7% of dam/spring water and in 25.3% of borehole water samples. The high prevalence of coxsackie B viruses found in this study suggested, that a potential health risk and a burden of disease constituted by these viruses might be meaningful. These findings indicated that strategies, other than end-point analysis of treated and disinfected drinking water supplies, may be required to ensure the production of drinking water that does not exceed acceptable health risks. More reliable approaches to ensure acceptable safety of drinking water supplies may be based on control by multiple-barrier principles from catchment to tap using hazard assessment and critical control point (HACCP) principles.     

Harmful algae and their potential impacts on desalination operations off southern California

Seawater desalination by reverse osmosis (RO) is a reliable method for augmenting drinking water supplies. In recent years, the number and size of these water projects have increased dramatically. As freshwater resources become limited due to global climate change, rising demand, and exhausted local water supplies, seawater desalination will play an important role in the world's future water supply, reaching far beyond its deep roots in the Middle East. Emerging contaminants have been widely discussed with respect to wastewater and freshwater sources, but also must be considered for seawater desalination facilities to ensure the long-term safety and suitability of this emerging water supply. Harmful algal blooms, frequently referred to as ‘red tides’ due to their vibrant colors, are a concern for desalination plants due to the high biomass of microalgae present in ocean waters during these events, and a variety of substances that some of these algae produce. These compounds range from noxious substances to powerful neurotoxins that constitute significant public health risks if they are not effectively and completely removed by the RO membranes. Algal blooms can cause significant operational issues that result in increased chemical consumption, increased membrane fouling rates, and in extreme cases, a plant to be taken off-line. Early algal bloom detection by desalination facilities is essential so that operational adjustments can be made to ensure that production capacity remains unaffected. This review identifies the toxic substances, their known producers, and our present state of knowledge regarding the causes of toxic episodes, with a special focus on the Southern California Bight.     

Willingness to pay for reliable supplies of safe drinking water in Guatemala: A referendum contingent valuation study

Unreliability of water systems has become a major concern in many developing countries. A referendum-format contingent valuation (CV) survey was implemented to investigate household preferences, in monetary terms, for improved water services in the small town of San Lorenzo, Guatemala. A random sample of 500 households report that they currently adopt a variety of averting measures (e.g. in-home water storage and treatment) to cope with service interruptions and low water quality. Findings also indicate that households are willing to pay an increase of more than 200% in their water bill for reliable supplies of safe drinking water.     

The Avalon Lakes: An Environmental Opportunity

The Avalon Lakes project was a concept to utilize, as water storage reservoirs, shallow basins left by commercial peat exploitation. There are, however, important nature-conservation interests in the project area. The proposed scheme ultimately incorporated measures to enhance these and, perhaps unusually for a source development, was broadly supported by conservation groups. The related cost was estimated at £4.2M, or 17% of the overall source works'price.
Plans and scientific investigations of the scheme occupied a span of 21 years to 1988. It was eventually abandoned as an option for future water supplies following the restructuring of Wessex Water Authority in preparation for privatization of the water industry. The grounds for terminating the project were substantially concerned with costs, though coloured by lingering apprehension about the consistency of water quality.
There is now a greater public awareness of the adverse environmental effects of water resource developments. It is suggested that this will lead to future schemes, less obviously suited to their surroundings than Avalon, incurring a higher conservation-related cost in order to gain acceptance.     

Water and Disease After Croydon: A Review of Water-borne and Water-associated Disease in the UK 1937–86

T here W ere 34 outbreaks of water-borne disease recorded in the UK between 1937 and 1986, comprising over 11794 cases and at least six deaths. A total of 21 outbreaks were due to public water supplies, 11 of them contaminated at source; in eight of these 11 the water was unchlorinated or defectively chlorinated. None of the six reported deaths was due to contamination of public supplies at source. About 1000 cases of gastro-intestinal illness were caused by consumption ofafoods, particularly milk and canned nicats, that had been contaminated by polluted water during processing. Shellfish harvested from pollutcd cstuarics gave rise to increasing numbers of outbreaks of viral gastroenteritis and hepatitis A. The recreational use of water was associated with about 400 serious infections and probably many minor illnesses. Sonie hospital infections may have hecn derived from the potable water supply. A total of 14 outbreaks of legionnaires' disease and eight of humidifier fever were associated with water in buildings.
The future control of water-borne and waterassociated disease demands not only continued vigilance in the water industry but closer collaboration between public health doctors and water engineers and scientists.     

Rentabilite des investissements de production de granulats et incidences economiques sur les politiques departementales des granulats

Since Decembe 1979, France has become involved in a policy of departmental Aggregates supplies. In order to enable the specialized authorities to set up serious forecasts, the economic and financial aspect that must necessarily go with the political solutions must not be forgotten. The study which is presented shows the principal encoded data of the granulats production industry in a french department: tonnages requirements, sales price, cost price, investments and renewals, needs in near funds and in loans, financial costs. We realize that this industry is a heavy industry, because investments can exceed twice the annual turnover, duty free. The profitability of invested money needs gross running margins of 40 per cent minimum, after general expenses, depreciation and before financial costs, a figure that is unfortunately rarely obtained. Therefore we have to be very careful when the poslitical will is to move production sites. The financial cost for the collectivity (customers) could easily be high if the solutions kept are brutal.     

Practical Implications of the Use of Groundwater-Protection Tools in Water-Supply Risk Assessment

The tools of vulnerability mapping and groundwater-protection zoning were developed during the early 1990s to enable the National Rivers Authority and its successor (the Environment Agency) to realise a national ground-water-protection policy for England and Wales. The resultant maps and protection zones cover more than 2250 public water supplies, tapping over 160 aquifers, and took almost five years to prepare. An opportunity for the UK water industry to assess their usefulness arose in 1999 when new Government regulations required water companies to conduct risk assessments for the troublesome parasite Cryptosporidium , and this paper reviews some results of that exercise. In the light of widespread doubts about the effectiveness of sporadic monitoring alone, in protecting the health of users of private ground-water supplies, a simple and pragmatic pollution hazard assessment procedure is suggested, employing combined use of sanitary surveys with an aquifer vulnerability flowchart.     

Using optimisation for integrated water network management

The water industry has undergone radical change in the late 1980s and changes continue apace. We have been, and will continue to be, under increasing pressure to reduce costs and increase service within a framework where regulations are becoming tighter and demanding more information to achieve and substantiate performance. The major challenge will lie with the leaders of the industry. They have to achieve the right attitude, management technique and technical excellence to meet the requirements of change and to create adaptable organizations that can manage the challenges of change in a positive and proactive way. Cultural change has started but has a long way to go. We must overcome the traditional attitude of many water suppliers, which has typically been one of the ‘professional stewardship’ of a resource in which they supply water in the way they believe to be best. This must change and is changing to a more commercially minded management which is ‘customer centred’ rather than ‘product centred’. We must realize that our organizations manage a complex asset base which has to work towards strictly defined objectives of service quality, operational efficiency and regulatory requirements, all of which, as time goes on, are influenced more and more by substantial external forces.     

Valuing the subsurface pathogen treatment barrier in water recycling via aquifers for drinking supplies

A quantitative microbial risk assessment (QMRA) was performed at four managed aquifer recharge (MAR) sites (Australia, South Africa, Belgium, Mexico) where reclaimed wastewater and stormwater is recycled via aquifers for drinking water supplies, using the same risk-based approach that is used for public water supplies. For each of the sites, the aquifer treatment barrier was assessed for its log₁₀ removal capacity much like for other water treatment technologies. This information was then integrated into a broader risk assessment to determine the human health burden from the four MAR sites. For the Australian and South African cases, managing the aquifer treatment barrier was found to be critical for the schemes to have low risk. For the Belgian case study, the large treatment trains both in terms of pre- and post-aquifer recharge ensures that the risk is always low. In the Mexico case study, the risk was high due to the lack of pre-treatment and the low residence times of the recharge water in the aquifer. A further sensitivity analysis demonstrated that human health risk can be managed if aquifers are integrated into a treatment train to attenuate pathogens. However, reduction in human health disease burden (as measured in disability adjusted life years, DALYs) varied depending upon the number of pathogens in the recharge source water. The beta-Poisson dose response curve used for translating rotavirus and Cryptosporidium numbers into DALYs coupled with their slow environmental decay rates means poor quality injectant leads to aquifers having reduced value to reduce DALYs. For these systems, like the Mexican case study, longer residence times are required to meet their DALYs guideline for drinking water. Nevertheless the results showed that the risks from pathogens can still be reduced and recharging via an aquifer is safer than discharging directly into surface water bodies.     

Investment Appraisal in the Water Industry of England and Wales

Since privatisation in 1989, the changing nature of the water industry in England and Wales has increased the need for effective investment appraisal. Previous research highlighted many aspects of the industry that could detract from the efficacy of conventional discounted cash-flow techniques, and found that an investment-appraisal technique must fulfil a number of criteria in order to overcome these difficulties. This paper examines a number of financial and strategic management techniques for investment appraisal, and assesses their suitability with reference to these criteria. It shows that, of the studied techniques, the 'balanced scorecard'appears to be most suited for use in the water industry of England and Wales.     

Incidence of adenoviruses in raw and treated water

Adenoviruses are of major public health importance and are associated with a variety of clinical manifestations, i.e. gastroenteritis, eye infections and respiratory infections. The importance of water in the epidemiology of adenoviruses and the potential health risks constituted by adenoviruses in water sources and supplies are widely recognised. This study was conducted to assess the incidence of human adenoviruses in raw and treated water systems. Various raw and treated water were routinely monitored for the presence of adenoviruses, over a 1-year period (July 2000-June 2001). The supplies were derived from acceptable quality surface water sources using treatment processes, which conform to international standards for the production of safe drinking water. Adenoviruses were detected by firstly amplifying the viruses in cell cultures and then amplifying the extracted nucleic acids of these viruses using molecular techniques (nested PCR). The results indicated human adenoviruses present in 13 (12.75%) of the raw and 9 (4.41%) of the treated water samples tested. The combination of cell culture and nested PCR has proved to be a quick and reliable method for the detection of adenoviruses in water environments.     

Radioactivity in Water Supplies

T his paper considers the general monitoring of radioactivity in the water industry and discusses radioactivity standards for potable water. Specific topics are considered such as the problem of radon in groundwater supplies and the effect of the Chernobyl accident on rivers, water supplies, and sludges in Western Europe and Russia.     

Introducing competition into England and Wales water industry – Lessons from UK and EU energy market liberalisation

This paper summarises the experience concerning electricity and natural gas in the UK and the European Union since the 1980s with a view to drawing lessons for potential liberalisation and the introduction of competition into the England and Wales water industry. The paper suggests that the main lesson from energy sector experience is the requirement is to develop upstream competition in the supply of bulk water both to retail supply companies and to large industrial consumers. The pattern of water supply and demand in England and Wales is that there are excess supplies in the North and West and supply shortages in the South and East. In consequence, provided that there is sufficient interconnection capacity within and between regions, there should be major potential gains from trade both in bulk water supplies as well as in trade of abstraction licences. Such trade can offer potentially sizeable environmental benefits in terms of water sustainability as well as in short and long-term efficiency benefits to consumers. The paper concludes with recommendations for some experiments with abstraction licence and bulk water trading, e.g. in the South East of England.     

高层建筑电气设计中几个问题的思考与处理

在高层建筑电气设计中,楼梯走廊灯、设备房照明、小区路灯等的双电源自动切换开关可以用接触器构成,给出了自复式和手动自复式两种双电源自动切换开关控制电路;对较小的单相负荷可采用由微型接触器构成的双电源单相切换开关。给出了高层建筑楼梯灯的控制方案。分析了高层建筑中水泵房、空调冷水机组设备房的中性线截面偏大的问题,提出单相负荷配电线路和动力配电线路分开供电,和减小N线截面,保护断路器加附件两种解决方案。     

浅谈工程管理在水利行业中的应用

水利行业中工程管理工作对水利工程的正常顺利建设运行具有非常重要的意义和作用。因此,必须要提高水利行业中工程管理的应用质量和水平,从而更好地提高水利工程的建设运行质量和效益。     

湖南省资兴市城市湿地资源网络连通性的生态水文水质效应研究

目前,城市湿地水文连通性的科学性问题研究仍然不够充分。为了进一步探讨城市湿地水文连通性的生态水文水质效应,根据湖南资兴城市总体规划的土地利用、湿地的位置与面积、形态设置了4组实验,运用SWMM模型进行水文和水质的模拟研究。结果表明,增加城市湿地间的连通性对于固体悬浮物(SS)、COD、氮磷污染物的减少有积极作用,并且建立植被缓冲带、增设人工湿地等低影响措施可以有效降低城市的地表径流,对于污染物的消减作用较为显著。其中在增加湿地连通性的基础上加入低影响设计方案的生态水文水质效应最优,能够较好地解决城市湿地中的湿地水质问题。     

浅谈施工企业安全生产投入与经济效益的关系

根据多年从事施工管理工作的实践经验,就安全生产投入与经济效益的关系谈了一些看法,指出施工企业要生存发展,必须实现安全生产,必要的安全生产投入是施工企业减少事故、实现安全生产、从而提高企业经济效益和社会效益的基本条件。     

THE 1999 CRYPTOSPORIDIUM RISK ASSESSMENT EXERCISE IN ENGLAND AND WALES- A GROUNDWATER OVERVIEW

Regulations Introduced in 1999 obliged water companies In England and Wales to conduct risk assessments of their treatment works to establish whether there was a significant risk from Cryptosporidium oocysts in the water supplied. More than 330 treatment works were identified as being at risk, just over half of which were plants treating groundwater. This paper provides an overview of what water companies themselves identified as the most at-risk settings for their groundwater-based works in terms of aquifer and type of supply. Evaluation of results from the subsequent continuous monitoring regulatory regime that came into force on many of these supplies could validate the primarily qualitative nature of the initial assessments of at-risk settings. There would also be public health benefits from confirmation of whether currently-employed risk assessment methods are well-founded because similar procedures could then be applied with confidence to the many small private supplies In Britain.     

Microbiological surveillance of private water supplies in England - The impact of environmental and climate factors on water quality

A passive surveillance system captured information on 34,904 microbiological samples from 11,233 private drinking water supplies within England as well as the associated constructional, climatic and environmental variables. Escherichia coli was detected in 6588 (18.87%) of samples and at least one positive sample was detected from 3638 (32.39%) of sites. However, this estimate of supplies failing to meet the European drinking water E. coli standard was probably an underestimate as the more samples taken per supply, the more likely the supply was to fail. A multivariable model of private water supplies data showed a strong seasonal impact, with samples between January and May being significantly less contaminated with E. coli than samples between June and December. Samples from springs (OR 2.5, CI 2.0-3.1) or surface waters (OR 2.4, CI 0.8-7.0) were more likely to fail than groundwater sources, as were supplies with no effective treatment (OR1.8, CI 1.5-2.3). Commercial supplies were less likely to fail than domestic supplies (OR 0.63, CI 0.48-0.83) and the probability of failure was linearly associated with the density of sheep in the area and rainfall on the previous day. A Monte Carlo modelling approach was used to estimate that, had sufficient samples been taken, 54% (95% confidence intervals 49-59%) of all private water supplies in England were likely to be unsatisfactory. These findings will be able to inform risk assessments of private water supplies prior to microbiological results being available.     

浅谈预拌混凝土生产的质量控制和监管

随着混凝土行业发展,必然存在企业众多且良莠不齐的情况;盲目进行投资建设,造成产能过剩;竞争的加剧,使企业以质量来换取利润。这些情况制约着混凝土行业的发展。本文针对混凝土生产现状及监管中发现的问题谈一点看法和建议。