Successful pilot test of three-stage BNR filtration process in China

A patented three-stage biologically active reactor system for treating wastewater has been successfully pilot tested in China's Zhejiang Province. The TETRA fixed-film BNR process from Severn Trent Services enabled the Jiashan Yao-chuang wastewater treatment plant in Jiashan City to reduce effluent to levels that conform with the country's Class 1A effluent discharge standards of

• TETRA® fixed-film BNR process from Severn Trent Services cost-effectively meets the strictest effluent discharge standards

FORT WASHINGTON, PA, Feb. 29, 2008 -- A patented three-stage biologically active reactor system for treating wastewater has been successfully pilot tested in China's Zhejiang Province. The TETRA® fixed-film BNR process from Severn Trent Services enabled the Jiashan Yao-chuang wastewater treatment plant in Jiashan City to reduce effluent to levels that conform with the country's Class 1A effluent discharge standards of <10 milligrams per liter (mg/L) Biological Oxygen Demand, <5 mg/L ammonium-nitrogen and <15 mg/L total-nitrogen.

The plant consists of a three-stage, fixed-film biological nutrient removal system. The first stage was a submerged denitrification filter reactor utilizing 2 meters of gravel media. The second stage was a submerged aerated filter reactor utilizing 3.5 meters of gravel media. The last stage was a TETRA DeepBed™ filter utilizing 1.8 meters of sand media. The TETRA system at the Jiashan Yao-chuang plant uses no chemicals and doesn't require the use of an intermediary clarifier. The use of a primary clarifier ahead of the TETRA fixed-film BNR process may be required in order to remove suspended solids from the influent wastewater and filter backwash water.

During the pilot study, average Biological Oxygen Demand was reduced from 200 to 2 mg/L, ammonium-nitrogen from 82 to 3 mg/L, total-nitrogen from 88 to 11 mg/L and total suspended solids from 165 mg/L to non-detect.

According to David Slack, TETRA business unit director of Severn Trent Services, "The two-month pilot study at the Jiashan Yao-chuang wastewater treatment plant demonstrated the ability of the TETRA fixed-film BNR process to cost-effectively deliver a final effluent meeting the Class IA effluent discharge standards without the use of chemicals."

"In order to meet more stringent U.S. effluent standards, methanol is needed to reduce Oxidized Nitrogen (NOx-N) to 1 mg/L or less. Among biological nutrient removal systems, the TETRA system with the addition of methanol can guarantee compliance with the U.S. standard."

Based on the results from the pilot plant, a full-sized treatment plant has been designed utilizing the three-stage treatment process. The plant is currently under construction in Jiashan, and is scheduled to be in operation in April 2008.

Severn Trent Services, with global headquarters in Fort Washington, Pa., USA, is a leading supplier of water and wastewater solutions.

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