Power Generation

A new desalination process could generate electricity as well as clean water, according to a team of researchers from the US and China.

The team modified a microbial fuel cell, which uses bacteria to convert wastewater into clean water and electricity, to desalinate salt water.

“It currently takes a lot of electricity to desalinate water,” explains Bruce Logan from Pennsylvania State University. “Using the microbial desalination cells we could actually desalinate water and produce electricity while removing organic material from wastewater.”

Instead of requiring an electrical input and high water pressure to desalinate water, the new process uses organic matter to remove 90% of salt from brackish water or seawater.

Typical microbial fuel cells have two chambers – one containing wastewater or other nutrients and the other water – each fitted with an electrode. Bacteria in the wastewater consume the organic material, generating electricity in the process.

In the new process a third chamber containing seawater is added to the fuel cell in between the other chambers, separated by ion-specific membranes. When the bacteria consume the wastewater, charged ions are produced, which are separated by the membranes. Some are consumed at the electrodes – desalinating the water in the central chamber and generating a current.

“This is not a practical system yet as it is not optimized, but it is proof of concept,” says Logan. “Our main intent was to show that using bacteria we can produce sufficient current to do this.”

For further information:
www.psu.edu
A New Method for Water Desalination Using Microbial Desalination Cells. Xiaoxin Cao, Xia Huang, Peng Liang, Kang Xiao, Yingjun Zhou, Xiaoyuan Zhang and Bruce E. Logan. Environ. Sci. Technol., (July 24, 2009), DOI: 10.1021/es901950j