Aug 21, 2009

Dow Dual-Membrane Technology Enables Blowdown Reuse in China

Integrated technology helps realize more than 70% reuse of cooling tower blowdown

For the past 40 years, the Gaojing Power Plant has supplied heat and electricity to its local communities and industries. Facing increased environmental regulations from the Chinese government in 2003, the plant enlisted DOW Ultrafiltration modules and DOW FILMTEC brackish water reverse osmosis elements as a solution for reuse using the blowdown from their cooling towers as boiler feedwater.

“Water recycling systems for cooling tower blowdown have become more common in fossil fuel power plants because of the large volume of wastewater needed,” said Kelvin Cheung, strategic marking manager for Dow Water & Process Solutions. “Coupled with the proper pretreatment and chemical dosing, DOW Ultrafiltration modules and FILMTEC membranes help eliminate problems in subsequent wastewater reuse systems.”

Located in Mengtougou and constructed in the 1960s, Gaijing is one of the earliest power plants built by Datang Corp. in Beijing. Traditionally, the source of the cooling tower makeup was from surface water, but was changed to secondary effluent from the Gaobeidian Municipal Wastewater Treatment Plant in 2007. Due to the wastewater’s concentration, contaminants varied substantially with seasons and cooling tower makeup quality.

Dow Water & Process Solutions’ dual-membrane technology was able to overcome a waste stream containing high hardness, alkalinity, silicon dioxide and sulfate, typical in cooling water blowdown to help the power plant meet increasing environmental requirements from the government. The integrated technology, together with proper pretreatment and chemical dosing, helped the plant to realize more than 70% reuse of the cooling tower blowdown—even after five years of operation.

This dual-membrane solution consists of DOW Ultrafiltration SFP-2660 and DOW FILMTEC BW30-365FR and BW30-400 reverse osmosis membranes.