Three-Stage BNR Filtration Pilot in China Successful

TETRA fixed-film biological nutrient removal (BNR) process from Severn Trent Services cost-effectively meets strict effluent discharge standards

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

The plant consists of a three-stage, fixed-film BNR 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 system at the Jiashan Yao-chuang plant uses no chemicals and doesn’t require use of an intermediary clarifier. Use of a primary clarifier ahead of the fixed-film BNR process may be required to remove suspended solids from the influent wastewater and filter backwash water.

An illustration of the Jiashan Yao-chung wastewater treatment plant set to begin operation in April

During the pilot study, average biological oxygen demand (BOD) 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 levels.

According to David Slack, Severn Trent Services’ TETRA business unit director, “The two-month pilot study at the Jiashan Yao-chuang wastewater treatment plant demonstrated the ability of the 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.

With global headquarters in Fort Washington, Pennsylvania, USA, Severn Trent Services (www.severntrentservices.com), is a leading supplier of water and wastewater solutions. A unit of Severn Trent Plc, it focuses on disinfection, instrumentation and filtration technologies, contract operating services and residential metering products and services.