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Underpinning knowledge

Sources of funding

Scottish Water

Peer reviewed papers

Streftaris, G., Wallerstein, N., Gibson, G., and Arthur, S. (2013). Modeling Probability of Blockage at Culvert Trash Screens Using Bayesian Approach. J. Hydraul. Eng., 139(7), 716–726.

Wallerstein, N. P. & Arthur, S. (2013) A new method for estimating trash screen blockage extent. Proceedings of the ICE – Water Management 166, 3, p. 132-143 12 p.

Blanc, J., Wallerstein, N., Arthur, S. & Wright, G. (2013) Analysis of the performance of debris screens at culverts. Proceedings of the ICE – Water Management 167, 4, p. 219-229

Home > WaterR2B > Sectors > Water Utilities > How can sewer blockages from fats, oils and greases be reduced?

How can sewer blockages from fats, oils and greases be reduced?

The challenge

There are approximately 200,000 sewer blockages throughout the UK every year. It is estimated around 75% are caused by fats, oils and greases (‘FOG’). Blockages account for 55% of sewer flooding incidents in the UK and more than 3,000 properties are flooded each year as a result.

Problems caused by FOG in the sewer system not only affect the performance of the sewer system and waste water treatment works, but also reduce asset life and increase maintenance costs. Scottish Water spends around £7m/year clearing blocked sewers, and is keen to reduce this expense if possible.

The solution

Scottish Water asked CREW, and researchers at Heriot-Watt University, to carry out a desk-based study of the literature relating to FOG deposition and recovery, reviewing academic publications and trade journals internationally. This was supplemented with information from water authorities, sewerage providers, technology companies, government bodies, and social media outlets. A number of case studies were used to illustrate different approaches to FOG management currently being used.

Both residential and commercial properties contribute significantly to FOG in the waste water system. Case studies show that an active programme of education, licensing, inspection and enforcement can result in significant reductions in FOG related blockage and sewer overflows. In addition the research demonstrated that while FOG in the waste water system are a major problem, there is an opportunity to recover these materials and use them beneficially in processes that will improve both the environment and waste water treatment efficiency. Key to this is educating and encouraging communities and businesses to think of FOG as a valuable commodity rather than waste.

The research has highlighted that sewerage providers cannot be expected to manage FOG on their own. Where FOG has been dealt with effectively it has been through partnerships with sewerage providers, local authorities, technology companies, business and householders. 

Resulting benefits

Following the report, Scottish Water launched its largest ever campaign in October 2013 to highlight the impact of what Scots put down their sinks and toilets. A national television campaign ran for 8 weeks, and a website www.scottishwater.co.uk/cycle was created to advise customers how to dispose of household waste correctly.

Scottish Water asked its 3,400 employees to use their own social media presence to increase the visibility of the campaign. Two pilot campaigns in Hamilton and Dunfirmline, identified as key areas for improving service, also involved radio, direct mail, visits to schools and working alongside the NHS

Future directions

A second phase of Scottish water’s campaign was launched in February 2014, and the campaign has generated considerable publicity and support within Scotland. 

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