Pilot Test Confirms Success of TETRA® Biological Submerged Aerated Filter in Cold-Weather Ammonium Removal

Test will help system's manufacturer, Severn Trent Services, design and apply the system to meet the needs of the fast-growing U.S. market for nutrient removal of secondary municipal effluent.

FORT WASHINGTON, Pa. - October 8, 2009 - Pilot testing of the TETRA® SAF biological submerged aerated filtration system at the City of Lebanon (Pa.) Authority's wastewater treatment plant (WWTP) in March 2009 has further confirmed previous test results demonstrating the system's ability to remove ammonium in cold weather applications. The system, manufactured by Severn Trent Services, achieved ammonium removal rates of 20.2 lb of N/1000 cf-d at a temperature of 57.5 degrees F (14.2 degrees C). As a result, Severn Trent Services has established a base rate of 26 lb of N/1000 cf-d at a temperature of 68 degrees F (20 degrees C) for the TETRA SAF system.

In addition the TETRA SAF system was found to be very effective in the removal of carbonaceous biological oxygen demand and total nitrogen without supplemental chemical addition at a two-to-one recycle ratio.

"There is a growing nutrient removal market in the United States, especially on the East Coast where stringent discharge regulations protect waterways," said Joe Bonazza, TETRA business unit director of Severn Trent Services. "In the Northeast, seasonal temperature changes require a biological treatment system capable of working in colder winter months. It was important to test performance of the TETRA SAF system in these climatic conditions, which are quite different than those in the United Kingdom, where we have a large installed base of SAF systems. Additionally, our U.K. systems are not subject to ammonium loads that approximate TETRA SAF's maximum treatment capacity. The testing enabled us to confirm performance of the system in the U.S. market's unique conditions and further develop a predictive model to design and size the TETRA SAF systems to specifically meet these conditions."

For more than ten years, the TETRA SAF system has offered proven performance, reliability and operational and maintenance cost savings over competitive systems. The system is a simple process that can be configured for biological oxidation of ammonium and CBOD or biological reduction of nitrate-nitrogen for municipal and industrial wastewaters. TETRA SAF is an upflow, fixed-film biological reactor that uses coarse media requiring no backwashing. A robust and small footprint system, it can be used as either a secondary or tertiary treatment. When combined with primary and final settlement, the system offers a complete high-performance treatment process. TETRA SAF is a simpler alternative to more complex treatments such as activated sludge and biological aerated filters, which require more extensive operator input and process monitoring and control. The design encourages the growth of a robust biomass capable of consistently producing high quality effluents, even during large variations in hydraulic and biological loadings.

About Severn Trent Services

Severn Trent Services (www.severntrentservices.com), 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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