Apr 12, 2001

Illinois Researchers Remove Toxins from Wastewater with Sludge

Nasrin Khalili, an environmental engineer, and her team at the Illinois Institute of Technology developed a patented process that can turn sludge from municipal wastewater plants or paper mills into activated carbon, an ingredient used by manufacturing plants to remove toxic chemicals such as nitrogen oxides from their emissions.

"Activated carbon is used by virtually every manufacturing plant to remove NOx in order to comply with the 1990 Clean Air Act Amendment," says Khalili. "We have come up with a way to turn toxic paper mill sludge into something manufacturers including paper mills need."

NOx is the generic acronym for a group of highly reactive gases, all of which contain nitrogen and oxygen in varying amounts. These gases form when fuel is burned at high temperatures in fossil fuel-fired electric utilities and other industrial facilities such as paper mills.

Khalili gets her sludge for free from a paper mill in Green Bay, Wis., and turns it into "IIT carbon," named after the institute.

Sludge from manufacturing plants must be treated and dried before it can be deposited at landfills. This is an expensive process that companies would like to avoid, especially considering that a days production of sludge can amount to 250 tons.

Activated carbon is pressed into a wafer-shaped filter that is fitted into the smokestack. As emissions pass through the filter on their way out, NOx is removed. "But the process isnt very efficient," says Khalili.

She has tested her activated carbon against the commercially produced equivalent and claims that her product works better with a NOx removal capability of 66 percent to 94 percent.

"The NOx isn't in contact with the activated carbon for very long as it passes through the filter. I am working on developing a method where the activated carbon is introduced into the smokestack as a aerosol. That way, the emissions will interact with the activated carbon during their entire trip through the smokestack instead of just at one point," Khalili explained.

To do an even better job of eliminating toxic NOx emissions, Khalili is working on combining IIT carbon with bacteria that metabolizes NOx to produce a biocatalytic activated carbon.