The Prevention of Oil and Chemical Pollution: Proactive Approaches in the UK and Canada

In the UK, various initiatives have been launched in an attempt to provide guidance on the occurrence and avoidance of oil and chemical pollution. Despite these efforts, oil and chemicals remain a major cause of pollution. In Canada, similar initiatives have been more successful due to a participative approach to campaign development and implementation. This paper compares UK and Canadian initiatives and identifies factors which led to the success of the Canadian campaigns.     

Upgrading Biological Filter Effluents Using the TF/SC Process

The trickling filter/solids contact process has been shown to be an excellent means of upgrading biological filter plants in North America, and about 100 plants have been built since 1979 in both cold and warm climates, and on both large and small works. A variety of effluent requirements has been satisfied consistently, including monthly average BOD and SS concentrations of 10 mg/l and 10 mg/l respectively. Key design features are described, including the use of an aerated solids contact tank to flocculate dispersed solids. Also, a flocculator-clarifier with special design features allows the use of high overflow rates and smaller sedimentation tanks.     

Satisfying the Water Supply Demand of the Channel Tunnel

When Europe's largest civil-engineering construction site, the Channel Tunnel, requested a guaranteed source of water during 1988, the Folkestone District Water Company was experiencing the first signs of the drought conditions which were to prevail for the next three years. Whilst infrastructure changes allowed for supplies to be made available to the Channel Tunnel contractors, the increasing reduction of resources meant that an alternative supply of water was required.
The solution to the problem was to utilize desalination by reverse osmosis of sea water taken from the English Channel. The process design and operation of this most arduous of feed water is discussed, demonstrating the successful application of this technology.     

Vacuum Sewerage – The Four Crosses Experience

The paper describes the installation of a vacuum sewerage system in a village on the Welsh border west of Shrewsbury. Reasons are given for the choice of system, design criteria, and installation experience, together with observations on the system's performance over the last four years.
The scheme is self-contained in that it has a dedicated sewage-treatment works in the form of a proprietary rotating biological contactor, and it is about to be extended in a second phase of vacuum sewerage.     

用于高频的新颖开关电容积分器

本文研究了用于开关电容(SC)滤波器的离散积分器,所推荐的积分器是由无耗离散积分器(LDI)和双线性离散积分器的最佳线性结合而成,因此,称之为组合离散积分器(CDI)。由于这个积分器使正常转折频率增加一倍,并使高频离散积分器误差减少到最低限度,所以它对高频应用是理想的。文中给出了组合离散积分器的几种SC实现,并且还给出了以组合离散积分器为基础,模拟一般一阶和二阶的模拟滤波器单元的SC电路。     

Beckton Demonstration Biological Nutrient-Removal Plant

Thames Water have recently built a demonstration-scale biological nutrient-removal plant at Beckton sewage-treatment works to provide (a) operational experience of nutrient removal, and (b) accurate design and cost information. The paper (i) outlines the basic principles of biological nutrient removal, (ii) describes the plant layout at Beckton, and (iii) presents results from the first three months of operation. The plant has removed over 50% of both nitrogen and phosphorus present in the settled sewage but has not been able to meet consistently the most stringent standards proposed by the urban waste water treatment Directive. Periods of good performance are compared with periods of poor performance, and differences in operating conditions are highlighted. From these findings, steps to improve performance are indicated and will be included in the future operational programme.