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Pilot testing of the Tetra SAF biological submerged aerated filtration system has further confirmed previous test results of the system’s ability to remove ammonium in cold weather applications.

The system, manufactured by Severn Trent Services, achieved ammonium removal rates of 20.2lb of N/1000 cf-d at a temperature of 57.5F (14.2C).

As a result, Severn Trent Services has established a base rate of 26lb of N/1000 cf-d at a temperature of 68F (20C) for the Tetra SAF system.

The system was also found to be 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 US, especially on the east coast where stringent discharge regulations protect waterways,’ said Joe Bonazza, Tetra business unit director of Severn Trent Services.

‘In the north east of the US, 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 UK, where we have a large installed base of SAF systems.

‘Additionally, our UK 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 US market’s conditions and further develop a predictive model to design and size the Tetra SAF systems to specifically meet these conditions,’ he added.

Tetra SAF is an up-flow, 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.

Severn Trent Services

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