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Wastewater Treatment

Nearly one percent of total energy expenditures in the U.S. are spent on wastewater treatment. So when one Missouri engineer came up with a method that actually produces more energy than it uses, it’s no wonder that people started to take notice.

Most of the energy for current wastewater treatment processes is used to aerate the tanks to maintain an oxygen concentration of about 2 milligrams per liter. It has long been believed that this was necessary to keep the microorganisms alive and working at an optimum level. However, it was found that lower concentrations (about 0.5 milligrams per liter) produced the same results while using about 30 percent less energy. In addition, the microorganisms lived longer and enriched more.

A second system has also been designed which converts the sludge and organic matter by-products of wastewater treatment into biogas. The self-mixing, anaerobic digester operates totally on its own with no external power.

When used in combination, the technologies have been calculated to produce a net energy gain. Although the current systems are designed for producing water suitable for irrigation, it is possible to generate potable water as well.

For information: Jianmin Wang, Missouri University of Science and Technology, Civil, Architectural and Environmental Engineering, 223 Civil Engineering, Rolla, MO 65409; phone: 573-341-7503; email: wangjia@mst.edu; Web site: www.mst.edu

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