Water Quality for Renal Dialysis

Over 100000 renal failure patients are treated by dialysis in the European Community (EC), and the number is rapidly increasing due to better medical care. The full importance of the quality of water used for renal dialysis is only now being recognized. Aluminium intoxication, first described in the early 1970s, highlighted the need for adequate treatment of water used to prepare dialysate. Other materials harmful to dialysis patients, such as chloramines, may arise as a result of water treatment practice. The paper presents a European-wide assessment of the problems of trace contaminants in dialysis feed water, and examines some contaminant sources in mains water in the light of dialysis water standards and the current treatment techniques available.     

Mechanisms of Leakage through Synthetic Landfill Liner Materials

The introduction of synthetic lining materials for leachate containment and the prevention of groundwater contamination was an important development in landfill technology. These materials have a low hydraulic conductivity which results in minimal leachate release by bulk fluid flow (advection) provided that the barrier (and its construction) is free from defects. However, the effectiveness of these materials as barriers cannot be confirmed unless contaminant release by diffusion is also taken into consideration.
This paper reviews the mechanisms by which transport through barriers occur. It highlights the role of diffusion as a pathway for organic compounds to migrate through synthetic liners and indicates its importance in terms of environmental impact and landfill design.     

An Air Quality Impact Assessment for the Proposed Development of Stansted Airport

T he results of an air quality impact assessment conducted in 1980, for the proposed development of Stansted airport, Essex, to a capacity of 15 million passengers per annum, are presented. Air pollutant concentrations measured in the vicinity of the airport were found to be low in comparison to ambient air quality guidelines and also when compared with other airports and urban areas.
Atmospheric dispersion modelling to predict future emissions and ambient concentrations of air pollutants revealed that air quality standards would be unlikely to be infringed and that concentrations would be generally within the range of those measured at Gatwick airport in 1979.     

Results of the First Pilot-Scale Controlled Cohort Epidemiological Investigation into the Possible Health Effects of Bathing in Seawater at Langland Bay, Swansea

A pilot study was conducted to investigate the feasibility of using adult volunteers to examine the possible health effects of bathing in UK seawaters which passed the EC bathing waters Directive. Langland Bay, near Swansea, was chosen for this experiment, which was conducted on 2 September 1989. Adult volunteers were recruited from the City of Swansea and randomly divided into bather and non-bather groups. All volunteers were given medical examinations and medical questionnaire interviews before and after 2 September.
Water quality on the day of the test was relatively unpolluted, as indexed by the commonly-employed bacterial and viral indicator species. The detailed medical questionnaire resulted in higher reported attack rates of perceived illness in both bather and non-bather groups than those published in previous studies, which have commonly employed a single telephone interview to acquire disease perception data. Statistically-significant differences in the bather and non-bather cohorts were found for the following perceived symptoms: sore throat, ear symptom, eye symptom at 3 d after 2 September, and for diarrhoea at three weeks after the experiment. The clinical tests employed failed to confirm these significant perceived symptom attack rate differentials.
The significance of these results is discussed in the context of previous research protocols to demonstrate the feasibility of this novel prospective controlled cohort approach for the acquisition of scientifically robust data on the health effect of recreational water use. If taken to a full-scale study, it is argued that this research protocol could offer considerable advantages over past methods and lead to scientifically valid water-quality standards for recreational waters.     

Laboratory Simulation of Disinfection Regimes for Trihalomethane Control

A collaborative project between Anglian Water and Imperial College has been undertaken to investigate alternative disinfection regimes for the control of trihalomethane (THM) formation in lowland surface water treatment. A laboratory experimental protocol has been developed to measure THM formation as a consequence of both pre- and post-disinfection stages with chlorine dioxide, ozone and potassium permanganate, evaluated as alternative pre-disinfectants in direct comparison with breakpoint and sub-breakpoint pre-chlorination. The protocol has been applied to raw water samples from eight locations within the Anglian Water region under winter and summer conditions.
The results have shown that THM formation can be reduced substantially, either by the application of chlorine dioxide and ozone as substitutes to breakpoint pre-chlorination or by reducing the prechlorination dose. The application of potassium permanganate as a pre-disinfectant had little effect on diminishing the formation of THM compounds. A further substantial reduction in THM formation can be achieved by diminishing the contact period following post-chlorination between free-chlorine and the treated water (e.g. by conversion of free-chlorine to combined-chlorine through reaction with ammonium sulphate).     

Occupational Risks from Infectious Diseases in the Water Industry

Workers in the water industry are sometimes exposed to infectious micro-organisms, particularly during the treatment and disposal of sewage. There is a legal requirement for water companies to appraise the degree of risk to which employees are exposed and then take appropriate action to minimize such risks. This is accomplished, to a large extent, by first understanding how infectious diseases are spread, and then devising safety practices to minimize occupational exposure to pathogenic micro-organisms. Examples are given of types of communicable disease potentially associated with drinking water treatment (Legionnaires' disease and leptospirosis), as well as sewage treatment (viral gastroenteritis, AIDS and hepatitis B). The degree of perceived occupational risk associated with these pathogenic micro-organisms is discussed along with preventative measures that can be implemented to minimize actual risk. There is no justification for enhanced immunization of water industry employees.     

Pesticide Transport to Surface Waters within an Agricultural Catchment

This paper presents data on the distribution of seven pesticides in an agricultural catchment which is located within the Agricultural Development and Advisory Service farm at Rosemaund, 11 km north-east of Hereford, UK. Data for aldicarb, atrazine, carbofuran, dimethoate, MCPA and isoproturon, are available for both the soil and surface waters (drain and stream water), with simazine data available only for the stream. Measurements were taken before and after pesticide application, which was made following normal agricultural practice. Soil residue data showed the degradation rates of the pesticides to be within the range of literature values. Pesticide levels in the stream and drains during runoff events following rainfall ranged from below detection limits (typically 0.02-0.1 μg/1), to 264 μg/1 (for carbofuran). Over 90% of the events had detectable maximum concentrations. The percentage of pesticide applied, which was removed during individual rainfall events, was calculated. The maximum value estimated was 1.1%, again for carbofuran. Most of the events gave values several orders of magnitude below this value.
The data have been used to try to validate a range of models which could be used for screening new pesticides or for informing decisions on the use of existing pesticides. The results of the validations are summarized.     

Cement-based Stabilization of Wastes: Practical and Theoretical Considerations

Rapidly changing public and political attitudes to the environmental implications of industrial waste disposal are forcing a re-evaluation of the longstanding practice of directly landfilling such waste, either in a mono-disposal or co-disposal manner. As a result, more technology-orientated solutions to industrial waste disposal are being evaluated. This paper describes one such process, cement-based stabilization/solidification, and examines its physicochemical basis, present-day application and potential future uses, and outlines areas where research into fundamental and practical aspects of the process are needed.