INCINERATION ‐ IS THERE A CASE?

Incineration has suffered from a sustained campaign of misinformation. Consequently it has been regarded as the least sustainable option for the treatment of wastes, including sewage sludge. By looking carefully at the issues surrounding the incineration of sewage sludge, as an example, it can be seen that reality does not support the commonly held view. Modern plants are an effective means of recovering the energy value of sludge and at the same time offer a continuous operation, which is independent of weather or land constraints.
Of course incineration needs to be regulated and EU Directives and National Regulations set the emission standards. The technology is such that these standards can be met, and more than this, the systems are capable of upgrading as more stringent standards are imposed.
Concerns over NO_x, dioxins, metals and pathogens are highlighted. In addition the permitting process is discussed. None of these should present a barrier to the implementation of incineration projects. Indeed the paper goes further and demonstrates that there is likely to be an increasing role for incineration as landfill, recycling to agricultural land and other options become more restrictive.     

Cost-Effective Water-Quality Modelling of Potable Water Distribution Systems

Before privatization of the water authorities in England and Wales in 1989, future water companies were instructed to provide auditable proof of their investment requirements by the production of asset management plans.
With respect to distribution systems for potable water, asset management plan studies have established that unlined ferrous mains are often the main cause of complaints about discoloured water. It has also been found that the investment in water mains rehabilitation, which is driven by water quality problems, overshadows similar investment requirements driven by high burst rates and poor hydraulic performance.
This paper describes how certain techniques of water quality modelling have been developed and refined to provide a rapid, cost-effective method for identifying requirements for water-main rehabilitation.     

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.     

Health Risks of Chlorination - is there a Problem?

C hlorine is an effective and reliable disinfectant whose use in the treatment of drinking water has ensured water of high microbiological quality. Although the benefits of chlorination are beyond doubt, the fact that chlorine reacts with many of the organic substances in raw waters forming some substances of potential risk to health has led to concern and has stimulated a series of investigations. These investigations have used a variety of approaches and techniques, including advanced organic analysis, epidemiology, and toxicology. The paper reviews this research and discusses some of the factors affecting the risks associated with drinking chlorinated water.     

Design and Construction of an Ion-Exchange Denitrification Plant in South Staffordshire

Increasing concern about rising levels of nitrate in groundwater supplies and their subsequent removal to comply with EC drinking water standards has led to the construction of the first full-scale ion-exchange nitrate-removal plant in the UK by the South Staffordshire Waterworks Company.
This paper describes the development of the project from concept, through pilot-plant studies to final design, installation and commissioning. It explains the role of ion-exchange technologies, the use of recently developed nitrate-selective resins and the development of a novel dual regeneration system. The initial performance of the full-scale plant is discussed.     

Water-Recycling Technologies in the UK

Urban water recycling in the form of rain, grey or black water is becoming an important element of demand-management practice in the UK, and appropriate technology allows the use of three different water sources for similar applications. The level of pollution in the water source and the application to which it is being recycled, dictate the level of technology which is used. This paper describes current water re-use practices in the UK (in terms of water source, technology scale, type and efficiency) and examines five case studies. Of more than 150 schemes identified, most are rainwater-collection systems and these are generally sited in rural areas. There are various single-house greywater recycling sites, many of which are part of water company or Environment Agency monitoring programmes. Larger-scale schemes employ both natural and hi-tech treatment options. Operationally successful schemes utilise appropriate technology for the end-use, although the economic benefits of many of the schemes are poor.     

Mothproofing Agents in UK Wool Textile Effluents

Mothproofing is an essential part of the manufacture of wool and wool-blend carpets and until now has usually been combined with another textile wet process, such as dyeing, to save cost.
Environmental quality standards for mothproofing agents in surface waters have recently been introduced. Compliance with these standards will require a reduction of more than 90% in the mothproofing agent content of industrial effluents in parts of the UK where mothproofing activity is most concentrated. In order to achieve such a reduction, it is proprosed that the carpet industry should install new methods of applying mothproofing agents, aimed at source reduction, rather than by adopting end-of-pipe measures.
Two new low-pollution mothproofing technologies are described in detail, and a summary is given of other possibilities.     

Developments in the Thermal Drying of Sewage Sludge

The application of heat to dried sewage sludge has been practised by the water industry for many years. Early technologies were effective but their utilization of energy was not so efficient. Other industries have faced up to this problem and, as a result, have developed thermal-drying techniques which are more efficient and therefore more cost effective. In recent years, the transfer of this technology to sewage-sludge drying has been taking place, and some companies have designed dryers specifically for this purpose. Commercial and legal pressures have also focused attention on the final product and its use in agriculture, horticulture, land reclamation, landfill, incineration, and as a substitute for fuel.
This paper reviews the work which has been undertaken to determine the changes which occur as sewage sludge is dried, and discusses the technology which is available at present. Factors influencing capital and operating costs and product choice are also included.