Abbeystead Outfall Works: Background to Repairs and Modifications – and Lessons Learned

The explosion at the Abbeystead valve house in May 1984, with its attendant loss of life and injury, forcibly drew the attention of the public to the dangers of methane and other natural gases. It also reaffirmed to the water industry and engineering professions the pervasive nature of the gas and the need to take appropriate measures in the construction, design and operation of any scheme which involves a possible methane presence. The investigations into the source and mechanism of the methane gas ingress, and the design of the permanent repairs and modifications to the scheme, have illustrated many of the risks and problems associated with methane and the measures for dealing with them.
The paper describes the essential repairs and modifications which had to be carried out, the main lessons learned, and the recommendations which are felt to be applicable to new and existing water schemes where methane may be present.     

Pre-Filtration of Very Highly Turbid Waters Using Pebble Matrix Filtration

As A SOLUTION to very high turbidity problems associated with slow sand filters, a new pretreatment method has been developed at University College, London. Initial experiments with a model using a bed of fine sand (effective diameter d. = 0.32 mm) demonstrated that maximum loadings on slow sand filters should not exceed 25 mg/1 at a filtration velocity of 0.2 m/h for satisfactory run times (approximately 5 weeks). However, a literature survey revealed that many tropical rivers may carry several hundred (or even a few thousand) milligrammes per litre of suspended solids during monssoon periods. A need for pretreatment methods is therefore obvious.
A novel process, called pebble matrix filtration, can protect slow sand filters by reducing the suspended-solids concentration of monsoon river waters (containing up to 5000 mg/1) to below 25 mg/1. The paper briefly describes the principles lying behind the treatment process of pebble matrix filtration, and suitable operational parameters are given at flow rates of 0.72–1.56 m/h for tested suspended-solids concentrations of 500, 1000, 2000 and 5000 mg/1 kaolin clay in London tap water, with achieved run times of up to 116 h to head losses not exceeding 1.5 m. Filter cleaning is described by a method called 'drainage and backwash'.     

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.     

Thermal-Distillation and Reverse-Osmosis Case Studies

During the past eight years, interest in thermal-distillation and membrane-separation processes has increased in the UK. Whilst distillation is a mature technology, and reverse osmosis has had setbacks in the last decade, both processes continue to be developed. To illustrate this development, two case studies have been selected.     

Fluvial Flood Forecasting

This paper describes some of the latest developments in real-time fluvial flood-forecasting systems which utilise quantitative weather radar information. Rain-gauge, flow-measuring stations, weather radar and other sources of information are fully integrated by the real-time flood-forecasting system and provide flood warnings for civil protection. The systems have been commissioned in various regions within the UK and are undergoing continuous development in conjunction with the UK water industry and through close involvement with various European partners via the auspices of the European Union.     

关联规则挖掘在煤矿安全监测中的应用

为了从大量的煤矿安全监测数据中获取有用的知识,来指导煤矿安全预警工作,本文将关联规则挖掘算法应用于安全监测数据的数据挖掘。根据数据的特点,对数据进行了预处理后,采用了多维关联规则挖掘算法。文章设计并实现了安全监测数据的关联规则挖掘系统。通过该系统,用户在设置最小支持度和最小置信度阈值后,就可以挖掘出关联规则。     

Developments in UK Reservoir Engineering and Management

This paper presents an overview of recent developments in reservoir construction and maintenance in the UK. It highlights the increasing importance of environmental issues to successful scheme promotion and provides advice on the key issues which need to be addressed. Research into dam safety is leading to further guidance for engineers in assessing existing structures. Comments are made on future capital expenditure on the existing stock of dams, and the status of dam safety legislation is reviewed.     

Milestones in the Development of the Activated-Sludge Process Over the Past Eighty Years (Abridged)

The biological filter was introduced during the latter part of the last century but, in 1913, a radical new process was developed which resulted in a four-fold reduction in the size of sewage-treatment plants. This new method was called the 'activated-sludge process', and whilst biological filters are still in use - especially for small works - activated sludge is now the dominant secondary treatment process and is the 'engine'around which modern treatment systems are constructed.
This paper (a) reviews the milestones in the evolution of the activated-sludge process from 1913 to 1954, centering on reliable removal of BOD and suspended solids, (b) highlights the improvements in design capabilities (1955-74), with the emphasis on the attainment of consistent nitrification, and (c) discusses the removal of nitrogen and phosphorus (1975-97), with brief reference to computer modelling and the control of sludge properties.