Articles & Case Studies


Posted: Wednesday 15th January 2014

Water Companies are under constant pressure to ensure sewage treatment works established decades ago can meet the needs of ever increasing treatment requirements. Thames Water has been making significant investments to improve the quality of its sewage treatment facilities, recently upgrading one of its largest sites in London.

Mogden is one of Thames Water’s largest sewage treatment works serving 1.9m people in and around London. Built in the 1930’s, the Mogden facility now has to cope with increased demand due to the growth in London’s population level and requirements to reduce the need for storm discharges to the River Thames.

In 2010, as part of the London Tideway Improvements programme, Thames Water started a £675m project to modernise and extend London's five major sewage treatment works. The £140m upgrade of Mogden Sewage Treatment Works will extend sewage treatment capacity by 50 per cent; greatly reducing the need for storm discharges to the river and improving water quality in the River Thames. The project is being delivered by Black & Veatch as principal contactor.

One of the major elements of the improvement project was to construct a completely new treatment stream. This includes a new five lane activated sludge plant, for which Xylem Water Solutions was appointed to provide key process mechanical equipment.

Julian Dempster at Black & Veatch explains:

“The new activated sludge plant will increase Mogden’s sludge treatment capacity. This will reduce the amount of storm sewage that overflows into the tidal stretches of the River Thames when the site becomes overloaded during heavy rainfall.”

In a sewage treatment plant, the activated sludge process is a biological procedure which relies on micro-organisms to remove contaminants within the wastewater. The process involves air or oxygen being introduced into a mixture of screened and primary-treated sewage combined with a high level of micro-organisms in order to reduce the organic content of the sewage.

At the time Xylem was submitting its tender, the new Sanitaire Gold Series was launched, a high efficiency diffuser that reduces the airflow needed for general aeration compared to standard diffusers. The Gold Series offers a greater standard of oxygen transfer rates and pressures, and when combined with high speed turbo blowers, will lower the overall energy consumption of a sewage treatment plant.

Xylem Water Solutions designed, installed and commissioned the new aeration equipment for the new five lane activated sludge tank. This equipment consisted of five high speed turbo compressors, stainless steel air main and 4,760 Gold Series diffusers.

The Mogden project is the largest installation of the new Sanitaire Gold Series and was one of the first systems to be installed in the world.

The Sanitaire Gold Series diffusers, combined with the high speed turbo blowers, is set to provide Mogden Sewage Treatment works with a whole life cost saving of over £3 million over the 20 year design life of the installation, achieving significant financial savings over the use of standard diffusers.

Phil Venables, Engineering Manager at Xylem concludes: “Not only does the Mogden installation highlight the cost effectiveness and efficiency of our product range, it also shows the difference made through sourcing a single package solution covering everything from installation, to design, to after care. Working closely with Thames Water and Black & Veatch allowed Xylem to design a bespoke system which not only maximises our customer’s energy and operational savings but also works to reduce the sewer overflow and improve the quality of the River Thames.

“Throughout the life of this project Xylem has developed a great working relationship with Black & Veatch and Thames Water. Through collaborative working the project has met the required time, cost and quality targets. Ensuring attention to detail and designing for safety in accordance with the CDM Regulations (2007) the plant was constructed safely and now allows for easy operation and maintenance through the lifetime of the installation.”

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