Fat trap

Experts at The University of Portsmouth are taking part in a three-year nation-wide study into how fats and oils from restaurants are congesting Britain’s sewage pipes and costing utility companies dearly.


Water companies spend over £25 million annually in treating sewers clogged with fatty residues from restaurant waste. It causes reduced capacity in sewage pipes, creating blockages and in some cases can result in the backing up of waste into restaurant toilets and into people’s homes. It has also been linked to flooding in areas where combined sewers carry both sewage and surface water.


The problem has been connected in particular to fast food restaurants and as part of the study the University’s waste-water experts will investigate the effects of different types of oil and fat used in various types of cooking.


Dr. John Williams of the University’s civil engineering department said: “Problems start when hot fat is poured down the sink, which goes solid, as it cools in the pipe and furs up the drains. The problem is worse in areas where there is a high concentration of restaurants.”


“Water companies are becoming more interested in preventative measures rather than treating the problem once it occurs,” said Williams. “There is a big gap in our knowledge because very little research has been done into the problem.”


Tests will also investigate the best ways to alleviate the problem, including a review of commercial detergents and ‘fat traps’, a device that physically traps fats and grease from wastewater before it enters sewers. Recommendations from the study will be given to the water industry, which will decide on best practices for the future.


Much of the research will be carried out at the University’s laboratories in the Centre for Environmental Technology at Petersfield sewage works. A PhD student will be employed and required to undergo special training to deal with working in confined spaces.


The research is funded jointly by the Engineering and Physical Science Research Council (EPSRC) and by the Water Research Centre, a private company that provides consultancy services to the water, waste and environmental industries.