Mark Zappi is on a mission to make sure ozone gets the respect it deserves. A gas found in the Earth's atmosphere, ozone has been in the headlines recently because of theories its depletion may contribute to global warming.
For the Mississippi State University chemical engineering professor, ozone offers a more down-to-earth benefit. He, along with forest products professor Hamid Borazjani and graduate students under their direction, are developing an ozone-based water treatment process for removing contaminants from polluted water.
"Ozone is used as a safe and effective drinking-water treatment by Paris, Los Angeles and other major cities of the world," Zappi said. "Despite that, it hasn't been considered aggressive enough for removing chemicals from industrial wastewater."
The MSU team recently tested a pilot-scale unit constructed by Ozonology Inc. of North Brook, Ill., at an industrial site in South Mississippi. Funding for the investigation was provided by the U.S. Environmental Protection Agency's Gulf Coast Hazardous Substance Center at Lamar University in Beaumont, Texas.
After test water was pulled from a flow to the site's bioreactor treatment system, it was treated, re-tested and put back into the bioreactor flow. The process was continuously repeated over a two-and-a-half week period.
The test unit involved four 20-foot tall Plexiglas columns through which wastewater is pumped downward. While ozone was pumped upward through the columns, hydrogen peroxide was injected into the downward flowing water.
"The process has promise for industries producing wastewater that requires a high degree of treatment," said Borazjani, who had helped the host industry install the microbe-based bioreactor used in the test. "In less than 10 minutes of treatment, the combination is very effective in destroying traces of wood-preserving wastes in the water."
At about 50 cents per 1,000 gallons of water treated, the tests also demonstrate that the ozone treatment is price-competitive with other methods of handling wastewater, Zappi said.
Ozone treatment has an additional advantage over some widely used organic methods of removing toxic chemicals from industrial wastewater.
"Using living organisms to remove contaminants is one of the problems with bioreactors," Zappi observed. "If something happens to kill off the organisms, you have manufacturing downtime while they are replaced."
Ozonology president Allen Morr said data generated by MSU's South Mississippi pilot project can be used to develop a system large enough for industrial use.
"We can take this technology and scale it up so it can do a full treatment of hundreds of gallons of water a minute," Morr said. "The pilot project results indicate this type of treatment can be used basically anywhere."
Zappi agreed with Morr's assessment. He said the project successfully shows that ozone can be an effective and efficient wastewater treatment, especially for one of the South's leading industries.
"This process has particular promise with wood-preserving waste streams and those containing similar chemicals," he said. "The result could be a new reliable and cost-effective treatment system for the numerous forest product industries in Mississippi and other Southern states."