Thames Water Ltd Once Again Selects Severn Trent Services Technology for Ammonia Removal at Sewage Facility

TETRA® NSAF technology to be used for sewage treatment works in Hertfordshire, South East England.

Severn Trent Services has been awarded a contract to supply its TETRA® NSAF (nitrifying submerged aerated filter) filtration technology to Thames Water Utilities Ltd, for the removal of tertiary ammonia down to 2 mg/l at its Standon Sewage Treatment Works. The technology's innovative design will be supplied in a glass-coated steel tank designed for an average flow of 900m3/day and will be constructed on site in February 2011.

Severn Trent Services has previously supplied the TETRA NSAF technology to Thames Water Utilities Ltd. In 2006 and 2007, contracts for three installations were awarded for the Waddesdon, Culworth and Byfield wastewater facilities as extensions to the existing works for tertiary nitrification to meet ammonia standards. An additional seven TETRA NSAF installations have since been completed for Thames Water Utilities Ltd.

TETRA NSAF is an established and proven technology for ammonia removal. The upflow, fixed-film biological process is extremely flexible and is available in a range of sizes - from small modular units suitable for above or below ground construction to custom-made configurations for large plants. It can be combined with various solids removal processes or enable direct discharge of the effluent depending on individual site circumstances.

According to Mick Pichur, capital delivery engineer at Thames Water Utilities, "Ammonia removal technology was needed at Standon to cope with increasing demand on the works. Because of our experience with the TETRA NSAF process at other Thames Water sewage treatment works, we had confidence in the technology to meet the consent limits at the Standon facility."

About Severn Trent Services
Severn Trent Services (, with global headquarters in Fort Washington, Pa., USA, is a leading supplier of water and wastewater solutions. The company's broad range of products and services is concentrated around disinfection, instrumentation and filtration technologies, and contract operating services. Our analytical services group is the United Kingdom's leading environmental testing organization, and our international operating services business provides worldwide contract operation and support for all aspects of water and wastewater utility operational development and business transformation. Severn Trent Services is a member of the Severn Trent Plc (London: SVT.L) group of companies. Severn Trent is a FTSE 100 company.

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Fran House
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Eric Risch
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