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Largo's wastewater has excess dissolved organic matter

LARGO — The water appears clear, according to Irvin Kety, director of the city's Environmental Services Department, but there's something in it. Some things, actually. Dissolved bits of plants and other organic material that interfere with ultraviolet light that otherwise would disinfect the water.

And though you can't see it in the water, the stuff could make Largo's pricey wastewater system upgrades even more expensive. But Kety is optimistic it won't.

"We are on budget, and we are on schedule," he told the City Commission at Tuesday night's work session.

Kety and city engineer Leland Dicus are overseeing a $13.6 million project to replace the system that disinfects Largo's wastewater before it's pumped into Tampa Bay or sent out to reclaimed water customers. The project is part of an estimated $73 million overhaul of the city's sewer system necessitated by a 2006 consent order from the Florida Department of Environmental Protection for city violations of federal and state regulations.

Largo is taking on the overhaul piece by piece, and this year, Kety and Dicus are focused on replacing the system that disinfects wastewater. Largo's Wastewater Reclamation Facility uses chlorine to disinfect the water, then sulfur dioxide to remove the chlorine before the water leaves the facility.

While disinfecting the water, though, chlorine also creates a little byproduct with a big name — bromodichloromethane — that experts say is harmful to animals and may cause cancer in humans. Largo discharged wastewater with too much of the byproduct from May 2001 through March 2005, and Dicus told commissioners Tuesday the city is still struggling to get its wastewater within regulatory limits.

To fix this problem, Largo will replace the old disinfectant system with a new one that uses ultraviolet light. Unfortunately, as Dicus and Kety explained to the City Commission on Tuesday, Largo's wastewater has too much dissolved organics in it.

While they're not visible, the organics can cause the UV light to twist and bend as it travels through the water, inhibiting its disinfecting powers. Greeley and Hansen, an environmental engineering firm Largo is paying $2.8 million to design the new system and accompanying pumps, will test various methods to reduce the amount of dissolved organics in the city's wastewater later this summer.

If the engineers can't come up with a solution, then the new system will need more UV lamps and rack up a bigger electric bill. But Kelly and Dicus are optimistic that won't happen.

Dicus told commissioners Tuesday that there is contingency built in to the original $13.6 million price estimate, but he did not guarantee the price wouldn't go up. Dicus will be back in front of them in January with the final design. The new system is scheduled to be built in 2013 and be operational in 2014.

"We will have a much better understanding of the cost when we come back in January," Dicus said.

Will Hobson can be reached at (727) 445-4167 or whobson@sptimes.com.

Largo's wastewater has excess dissolved organic matter 07/16/11 [Last modified: Saturday, July 16, 2011 5:31am]

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