EAT can 'virtually eliminate' sludge

Energy consultancy EA Technology has been granted patent rights for a new sewage treatment process called Bio Logic, which 'virtually eliminates sludge'.

'In two years of trials our Bio Logic plant has cut the volume of sludge produced in the conventional treatment of industrial waste and domestic sewage by at least 95 per cent,' says EA Technology's Mike Colley. 'In many cases it is eliminated altogether.'

The company was aiming to improve the energy efficiency of sewage treatment plants, but in so doing it claims to have cracked the sludge disposal problem, too.

Colley adds: 'Disposing of sewage sludge is a growing headache. Last year the UK produced over 1.1 million tonnes of dry sludge. This will rise 30 per cent over the next three years.

However, sea dumping will be banned in 1998 and other disposal options are becoming increasingly regulated and expensive. Incineration is one possible answer to the problem, but that also has cost and environmental implications.

EA Technology's patent is for a novel variation on the established activated sludge process, with the addition of aerobic digestion within a single reactor vessel. The company has discovered that by using a specially-developed venturi injector to aerate the sewage biomass with very small bubbles and create high turbulence, it can create the ideal conditions for micro-organisms to digest virtually all the solid materials in suspension. The only pre-processing required is de-gritting and screening. Trials suggest that the cost of treating waste should be less than 2p/t.