Brown and Caldwell, Columbus Water Works Earn Top International Award

The International Water Association on Sept. 3 announced that Brown and Caldwell and the Columbus (Ga.) Water Works won the 2008 Global Project Innovation Superior Achievement Award for work on the Columbus Biosolids Flow-Through Thermophilic Treatment and Cogeneration System Project.

The award will be presented at the IWA World Water Congress and Exhibition in Vienna, Austria on Sept. 10. Cliff Arnett, senior vice president of operations at the water works, and John Willis, principal investigator and Randy Shaw, project manager, will accept the award.

"This is great news for BC and the Columbus Water Works," says Denny S. Parker, Ph.D., P.E., the company' s director of technology. "Our people are the best when it comes to originating innovative technology that promotes sustainability."

To retrofit an existing wastewater treatment plant with anaerobic digesters, the Columbus Water Works and Brown and Caldwell used first-of-its-kind engineering to develop the process to convert the existing mesophilic digestion process to low-cost, Class A thermophilic digestion and produce Class A biosolids. The biosolids flow-through thermophilic treatment reduces required batch processing times from 24 hours to 30 minutes, saving Columbus Water Works approximately $3 million in capital costs.

Cogeneration is being implemented that incorporates state-of-the-art, lean-burn engine-generator technology to produce about 40 percent of the treatment plant' s electricity demand (Green Power) using biogas (digester gas) that would otherwise be flared. These new engines offer roughly 20 percent more power than previous generation engines or 60 percent more power than microturbines with low exhaust emissions.

The project is under construction and represents the culmination of more than six years of research and engineering evaluations that will advance anaerobic digestion.

"The project is revolutionary in that it is the first thermophilic anaerobic digestion process in North America to be run entirely off heat derived from digester-gas fueled power generation," says Willis. "Coupled with other gains, generation of this Green Power will result in a net carbon-offset of 9,500 metric tons as CO2 per year for this 40-mgd treatment facility."

Other green innovations include:

• using all of the biogas from digesters to generate renewable thermal and electrical energy;

• heating the raw solids by first using heat recovered as digesting thermophilic biosolids are cooled to mesophilic temperatures in the TPAD system;

• continuing to heat solids to thermophilic temperatures and maintaining digesters at this level using heat recovered from the engines used to generate power; and

• treating digester gas to remove water, siloxanes, hydrogen sulfide, and particulates to levels required for the advanced engine-generators

The project also won the IWA' s 2008 grand prize in the Applied Research category, as well as the grand prize for research in the American Academy of Environmental Engineers' Excellence in Environmental Engineering awards competition in 2007.

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