09 July 2001

Turning muck into brass: engineer in line for £50,000

Sewage treatment may not be the world's most glamorous job, but someone has to do it. Now Southern Water engineer David de Hoxar could rake in £50,000 after being shortlisted for the UK's biggest engineering prize - the Royal Academy of Engineering MacRobert Award - for inventing a new settlement tank to separate muck from water.

The de Hoxar spiral separator started life in 1987 as a model made out of a cereal packet. Full-sized versions have now been installed at five sites in the South of England, including a £100 million modernisation of Portsmouth and Havant's water treatment plant serving over 400,000 people. The new separator is far more compact and efficient than conventional tanks and the design has been licensed so it can be developed for export as well as further use in the UK. As well as treating sewage, it is also being used to treat effluent from a food-processing factory in East Anglia and could be developed for use in other industries such as mining or paper - in fact any industry where solids have to be removed from liquids.

David's novel design uses a stack of giant plastic fins interlocked to form a cone up to 10 metres wide inside a circular tank. The entire cone rotates slowly as sewage is pumped continuously into the tank. The fins catch the solid waste and send it down to the bottom of the tank where it is removed (and used to make fertiliser). Meanwhile cleaned water moves up to the top of the tank and is taken off for further processing. "A similar technique called lamella separation also uses a series of plates to encourage the solids to separate out," says David. "But I realised that if the plates moved relative to the settling particles then it could be made a lot more efficient. This operation also helps to reduce odour from the plant."

One of the best things about David's design is that it is easy to scale up to cope with larger volumes of sewage - doubling the area of the glass-reinforced plastic plates doubles the cone's capacity. At present it still costs more than a conventional settling tank, but it is so compact that it is ideal for very small sites or environmentally sensitive ones where it makes less visual impact and is cheaper to enclose. The cost is already half that of the prototype, but David hopes to shave another 30 per cent off the price to enable the new separator to compete on equal terms with the conventional methods. "Gaining approval for spiral separators as activated sludge final tanks would be a major advance as the market potential is much greater than for primary settlement," he says.

David de Hoxar will receive his MacRobert Award finalist certificate from HRH the Duke of Edinburgh on Monday 9 July at the Academy's AGM in London.

ends

Notes for editors

1. Britain's biggest engineering prize, the Royal Academy of Engineering MacRobert Award, is worth £50,000 and the MacRobert gold medal to the ultimate winner, who will be announced in November.
   
2. Southern Water is one of three finalists for this year's MacRobert Award - the other two are Middlesex-based Sensaura Ltd for 3D audio and Belfast's Bombardier Aerospace for a new type of thrust reverser.
   
3. The Royal Academy of Engineering honours the UK's most distinguished engineers and aims to take advantage of the enormous wealth of engineering knowledge and experience that its one thousand Fellows possess. It exists to pursue, encourage and maintain excellence in the whole field of engineering to promote the advancement of the science, art and practice of engineering for the benefit of the public.

For more information please contact:

Jane Sutton at the Royal Academy of Engineering tel. 0171 227 0536 / 07989 513045

or

Tom James at Southern Water tel. 01903 272091 / 07802 604308

Links:

www.southernwater.co.uk

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