This paper outlines the increasing need for effluent polishing in the United Kingdom. It puts that need in the context of the more than 700 sewage treatment works serving populations of less than 2 000 in Severn Trent Water's area of the English Midlands. Constructed reed beds have their place in a design selection matrix. At the end of 1991, they were in use at 12 sites and more than 60 are programmed for completion in 1992. The design and construction of reed beds used for effluent polishing is described. Detailed results are given for five of the works commissioned between 1987 and late 1991. All produce high quality effluents in terms of BOD5 and total suspended solids. A cost comparison between reed beds and modular sandfilters, based on recent contract prices, is shown. Estimates of maintenance, labor costs, and asset life are included.zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA Water Environ. Res., 66, 188 (1994).

Right-angle branched filaments and rods micromanipulated from activated sludge foam and mixed liquor were identified as putatively novel members of the genera Gordonia, Mycobacterium and Rhodococcus using a combination of chemical, molecular and morphological data. Pyrolysis mass spectrometric analyses of gordoniae isolated in both the present and a previous study revealed pyro-groups, distinct from validly described Gordonia species, which could be equated with those based on morphological properties and 16S rDNA data. Putative gordoniae assigned to one of these groups were found to be closely related to strains currently identified as "Rhodococcus australis". These strains were also found to have properties consistent with their classification in the genus Gordonia. The results of this study highlight the limitations of the microscopic approach to filament identification and cast further doubt on the view that foaming can be attributed to members of one or a few Nocardia species.

The new United Kingdom drinking water standard of 10 μg/l arsenic will become a statutory obligation in 2003. To comply with the new standard, Severn Trent Water will require a new treatment process to be installed at 17 groundwater sites. The Company embarked on a development programme in 1995, with pilot studies commencing in 1996. Investigations have covered a range of potential treatment technologies including coagulation, ion exchange, reverse osmosis and adsorption. Adsorption with granular ferric media was found to be the best available technology for treating groundwater in Severn Trent. The paper details the development work undertaken, which has focused on the evaluation of aluminium and ferric based granular medias. This has enabled the design and construction of the first arsenic adsorption plant in the UK, with an output of 20 Ml/d.

This paper outlines the background, objectives, methodology, findings, outputs and recommendations from the Direct Toxicity Assessment (DTA) Demonstration Programme. This was a trial of a suite of bioassay methods and a seven-step protocol designed to deliver water quality improvements in catchments with well-defined water quality problems, where ecotoxicity from effluents was a contributing factor. The trial was run as a collaborative venture between the environmental regulators and water and manufacturing industries in the UK and was conducted at three project sites: -a reach of the river Aire near the city of Bradford in Yorkshire; -a reach of the River Esk near the town of Langholm on the border between Scotland and England; and -the lower Tees estuary on the north-east coast of England. The outcomes of each project are summarised in this paper. The learning points delivered by the programme were used to make recommendations to the regulators on how best to use bioassays for the assessment and control of complex effluents in the UK. Guidance was provided on how to carry out the bioassays and on how to use the data generated for regulatory decision-making. The programme also demonstrated how the regulators and the regulated can successfully work together to tackle environmental issues and deliver effective and workable solutions.

Reed bed treatment is put in the context of a major water company’s need to provide reliable, high quality, effluents from small sewage treatment works whilst seeking to minimise running costs. Design and operational information is given for reed bed applications in Severn Trent Water. Performance details are provided for application to secondary, tertiary and storm overflow treatment. The results give particular confidence in the system’s ability to deliver very high quality effluents when used for tertiary treatment, the company’s biggest application. Reed beds work well against less demanding criteria for secondary treatment at small sites and show great promise for storm overflow treatment.