The Effect of Ozonation on Particle Removal in Drinking-Water Treatment

The effect of the introduction of additional process stages in a surface-water treatment plant was studied in order to investigate how particle removal could be optimized. Particle counting is considered to be a useful indicator of treatment performance. This paper is based on results which were obtained from trials on a water-treatment plant treating surface water; these consisted of a combination of modifications to existing full-scale plant and a specially constructed pilot plant.     

The Development of an Automatic Soil Sampler

A recently introduced EC Directive requires that soils receiving sewage sludge should be sampled to a greater depth (250 mm) than previously.
The Water Research Centre foresaw the difficulties that could arise for responsible Authorities if they were to cope with the extra workload and maintain the quality of sampling, and therefore it funded the development of an automatic sampler.
This report traces the development of the sampler which was mounted on an all-terrain vehicle, and illustrates its suitability for the task by reporting one year's operating experiences. Work rates have been up to eight times those with hand sampling.
A production machine from the first batch is also described.     

The Seaton Carew Sewerage Scheme: Design Features and Contractual Arrangements

Northumbrian Water Limited has thirty-four bathing waters and a substantial investment programme to ensure that these waters meet EC standards by 1995. One project within this overall programme is the Seaton Carew Sewerage Scheme. Seaton Carew lies on the southern edge of Hartlepool which has a population of 95000. The scheme will combine existing flows into new foul and storm-sewage outfalls. The headworks will incorporate screening, grit removal and pumping stations with substantial measures for odour control. Hydraulic operating regimes using active pump control and passive flume control have been investigated to ensure efficient treatment for a wide range of flows. The onerous design, manufacture and construction programme has required the development of new approaches to procuring the work, whilst maintaining a substantial element of competition. The various programmes have been substantially overlapped to ensure that the scheme is completed by April 1993.     

Biological Processes at Saints Hill Water-Treatment Plant, Kent

The new treatment plant at Saint's Hill has been operating since May 1992 and biologically treats ground-water to remove iron, ammonium/ammonia and manganese. The paper describes the project, the processes involved, the significance of pilot-plant studies, the different stages of commissioning and plant efficiency.
This method of treatment, although new to the UK, is well-established in France, and reference to existing plants using the processes is made for purposes of indicating the range of applicability of biological treatment processes.
Specific conditions are required for biological processes. Not all raw waters can be economically treated to produce an environment which is appropriate for bacterial activity. Conditions for biological iron and manganese removal are different. The paper illustrates the importance of pilot studies to establish the feasibility of biological processes and to determine the design parameters for industrial-scale works.     

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.     

The Use of Water for Agricultural Irrigation

This paper summarizes the present position of agricultural spray irrigation in England and Wales, providing (a) national statistics and regional information, (b) the reasons why farmers irrigate, (c) the place of agriculture in the economy, and (d) the value of irrigation. A review of the Ministry of Agriculture, Fisheries and Food irrigation surveys highlights the important crops in terms of area and volume of water used, sources of water and storage, and application methods. The predictions for the future, including the effects of climate change are reviewed with examples of how farmers, the EA, and the agricultural industry, are helping to overcome problems.     

Effectiveness of Secondary Digesters as a Pathogen Controller in Winter

A revision of the Regulations regarding the use of sewage sludge in agriculture has forced a change in emphasis in sludge treatment from stabilisation to achieving pathogen kill. Previous work carried out by United Utilities Service Delivery highlighted temperature as being a key factor in pathogen kill in mesophilic anaerobic digestion and a possible important factor in pathogen destruction in secondary digestion, which is normally carried out in large open tanks where temperature control is not possible. It was found that temperature is a key factor in the rate of pathogen de-activation under isothermal conditions. However, in the full-scale secondary digester trial under winter conditions it was found that there was a significant difference between the surface temperature and the bulk temperature within the sludge; at the surface the temperature decreased more quickly. There was no significant difference between the performance of the 'old'and 'new'design of concrete tank with respect to wall thickness, cooling rates and E. coli reduction rate. The glass-coated steel-tank design showed a marked increase in the cooling rate and, despite the low ambient temperatures and fluctuating sludge temperature, a minimum 1-log reduction in E. coli was achieved.     

Agricultural Pollution: Control and Abatement in the Upper Thames Region

The paper describes the approach and methods used during a three-year programme to improve river-water quality in an area seriously affected by agricultural pollution.
Low base-flow river systems serving clay catchments exhibit flash characteristics which required long-term permanent solutions to ensure improved river water quality under all weather conditions. The approach which was used needed to identify polluters and convince them (a) that effective remedies had to be found and implemented within a reasonable time scale, and (b) that there would be serious consequences of failure to undertake improvements. The initial contact with dischargers, the attitudes adopted and responses received are considered and discussed. Progress throughout each phase of the programme, the solutions used and the degree of improvement achieved are assessed. Legislative changes during the period of the programme, other factors influencing agricultural pollution of watercourses, and likely future implications of these, are discussed.
The success of the programme resulted in the elimination of all major sources of agricultural pollution.