Selenium is a potent environmental contaminant produced by oil refineries and chemical plants. Removing it from industrial wastewater takes time and money. To date, the process has involved a chemical process that employs catalytic reduction to convert selenium to an inert form.
Japanese researchers from Osaka University and Shibaura Institute of Technology have now developed a new way to use a strain of bacteria to recover selenium in wastewater. The researchers’ novel approach uses a bioreactor. In the reactor, the conversion of toxic selenium to a nontoxic form takes about 50 hours.
Once the recovery process is completed, the resulting waste sludge is burnable ash instead of water-laden sludge, which is costly to remove and dispose. Another benefit: the process permits recovery of Se, which has gone up in price from $2.01 per pound in 1996 to $47.4 per pound in 2005.
Researchers Satoshi Soda of Osaka University and Mitsuo Yamashita of Shibaura Institute of Technology have a developed a pilot plant reactor with Shinko Chemical in Japan that was completed last year. It has two bioreactor vessels and is able to process 400 liters of sludge at a time and 0.2 million gallons in a year. The researchers have plans to build larger systems for testing and validation. Researchers recently presented their findings at the Japanese University Network in the Bay Area (JUNBA) 2009 symposium in San Francisco.–Lee Bruno