An Assessment of the Cost of Recycling Household Waste in Britain and Ireland

A marginal cost model is developed based on published data relating to both bring- and collect-based household waste-recycling schemes. Both systems are judged to be capable of ensuring compliance for paper and glass with the EU packaging and packaging waste Directive's 15% recycling target. Only collect systems can ensure such compliance for metal and plastic packaging.     

Liquid Effluents: New Solutions to Old Problems

Effluent discharges from industrial processes will come under increasingly close scrutiny in the future, as legislation reduces the limits for discharges. Existing processes will, in many cases, be unable to meet the more stringent controls. Therefore a new generation of processes, capable of removing chemical pollutants from waste streams to nanogram levels, needs to be developed. Already the nuclear industry has extensive experience of applying some of these emerging technologies to control radioactive discharges, and is developing these processes further through the collaborative forum of AEA Technology's Effluent Processing Club so that they may be economically applied in the non-nuclear process and manufacturing industries.     

Coastal Wave Modelling

C oastal engineering works are designed to serve two main purposes. These are the prevention of flooding of land adjacent to the shoreline, and the protection of a stretch of coast against erosion. The design of a scheme to achieve either of these aims will require information on the wave conditions which are likely to occur at a coastal site. This paper describes some of the methods which are available to predict waves at a coastal site, and summarizes some of the techniques which may be used to aid the design of coastal works.     

Insights into Domestic Demand from a Metering Trial

Detailed metering trials together with a survey of property type, household size, and appliance ownership have provided an opportunity to study domestic demand in detail. The data are presented in a number of alternative ways to highlight the relationship between demand and features of the individual households. The uncertainties inherent in using small samples to estimate demands for an area are discussed, and the usefulness of ACORN classifications to characterize an area is examined.     

The Avalon Lakes: An Environmental Opportunity

The Avalon Lakes project was a concept to utilize, as water storage reservoirs, shallow basins left by commercial peat exploitation. There are, however, important nature-conservation interests in the project area. The proposed scheme ultimately incorporated measures to enhance these and, perhaps unusually for a source development, was broadly supported by conservation groups. The related cost was estimated at £4.2M, or 17% of the overall source works'price.
Plans and scientific investigations of the scheme occupied a span of 21 years to 1988. It was eventually abandoned as an option for future water supplies following the restructuring of Wessex Water Authority in preparation for privatization of the water industry. The grounds for terminating the project were substantially concerned with costs, though coloured by lingering apprehension about the consistency of water quality.
There is now a greater public awareness of the adverse environmental effects of water resource developments. It is suggested that this will lead to future schemes, less obviously suited to their surroundings than Avalon, incurring a higher conservation-related cost in order to gain acceptance.     

Energy Saving Using Jacked Aerators at Biddulph Sewage-Treatment Works

A means of improving the energy efficiency of an existing mechanically aerated activated-sludge system by mounting the existing aeration units on jacked platforms is described. The level of the platforms, and hence the immersion of the aerators, is automatically controlled to maintain a constant concentration of dissolved oxygen in the mixed liquor. Comparison of the controlled stream, in which there were two aerators, against an otherwise identical control stream showed energy savings of 20% and 13% respectively when the control involved both or only one aerator, without adverse effect on final effluent quality.     

Hydrology of Pesticides in a Chalk Catchment: Surface Waters

In an extensive study of pesticides in a Chalk catchment, twenty pesticides were selected for study; and this paper reports the findings of an eighteen-month programme of river and rainwater sampling. The results of periodic samples and an intensive river monitoring programme over the duration of a flood event are described.
Both rain and river water within the catchment were found to contain significant numbers of pesticides at varying concentrations. The paper describes the values and temporal variations which were discovered. Higher concentrations and greater numbers of pesticides appeared to be brought down by floods and high river flows; however, even during low flows, some pesticides were persistently found in the river.     

New Treatment Processes for Pesticides and Chlorinated Organics Control in Drinking Water

Sources of pesticides and chlorinated organic compounds potentially found in water sources are reviewed. International and UK drinking water standards for these compounds are discussed and compared with concentrations found in ground and surface waters derived from lowland agricultural and urban areas.
Water soluble herbicides including triazines, phenylamides (urons) and chlorophenoxy acids are the most commonly reported types of pesticide compounds found above 0.1 μg/l in water sources. The more toxic, and less water soluble, organo-chlorine and organophosphorus pesticides are rarely reported.
Chlorinated organic solvents are reported as contaminants of some groundwaters. Disinfection by-products, in particular trihalomethanes, formed during the chlorination of waters containing natural organics, are widely reported, sometimes at concentrations above current UK standards.
The effects of conventional water-treatment processes on the concentrations of these organic compounds are discussed. Additional water-treatment processes, designed specifically for trace organic micropollutant removal, are identified and reviewed. Ozonation, activated-carbon adsorption and air stripping are acknowledged as appropriate advanced water-treatment process solutions. Developments in novel technologies include organics destruction via advanced oxidation processes, biological processes, membrane technology and novel adsorbents.
Thames Water Plc is contributing to research in this area, investing over £5 million in pilot- and large-scale trials prior to a £200-£300 million capital investment programme in advanced water treatment in the 1990s.     

Strength of concrete under combined compression and tension-determination of interaction curve at failure from cylinder split test

Summary Interaction curve of concrete failure in the compression— tension combination of a biaxial stress situation is determined from the stress distribution existing on the loaded diameter of a cylinder under split test. From the analysis, the strength of concrete in pure compression and tension are also determined in terms of the splitting tensile strength. The results compare favourably with those of other investigators.

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Résumé D'après la distribution des contraintes sur le diamètre de la section chargée d'un cylindre soumis à l'essai brésilien, on détermine le diagramme d'interaction de la rupture du béton sous effort combiné en compression-traction. L'analyse permet de déterminer aussi, en termes de résistance à la traction déterminée par essai brésilien, la résistance du béton en compression et traction pure. Les résultats s'accordent assez bien avec ceux d'autres expérimentateurs.

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The SERC Flood Channel Facility

T he P aper describes a new large central experimental facility which has recently been built to investigate the hydraulic behaviour of rivers and flood alleviation channels when they flow in an out-of-bank condition. The SERC flood channel facility is jointly funded by the Science and Engineering Research Council (SERC) and Hydraulics Research Ltd (HR), on whose premises the facility has been built.
A five-year research programme has been identified and will be supported by the SERC together with a contribution from the Ministry of Agriculture, Fisheries and Food (MAFF). The authors outline the need for such a facility in flood channel research, the background to the design, construction and instrumentation of the facility, and give brief details of the initial phase of the research programme, which involves four university research teams.
It is hoped that the SERC flood channel facility will be a focus for other experimental researchers and will bring together theoreticians, numerical modellers and experimentalists concerned with river channel hydraulics. At present seven UK universities are involved in the SERC Working Party on Flood Channels, along with representatives from HR, MAFF and consultants.