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THURSDAY, MARCH 15, 2007
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Malfunction created sewage smell
Plant had problems with boiler tubes; consultant to study ways to reduce odor that hit city

By Bayne Hughes
hughes@decaturdaily.com 340-2432

Boiler tube malfunctions at Decatur's waste-water plant created a recent stink that permeated the city, a Decatur Utilities manager said.

At the request of Gas, Water and Wastewater Manager Gary Borden, the DU board approved Wednesday spending $40,000 to replace malfunctioning boiler tubes that created the severe smell at least twice in the last 10 days.

The utility also plans to hire a consultant to get suggestions on how it can reduce the usual smell coming from the Alabama 20 plant.

The smell from the waste-water plant has been an issue for years, particularly because of its location across the highway from Leon Sheffield Elementary School. Students and teachers holding their noses is a familiar sight, especially when a north wind blows off the Tennessee River.

In 2002, the utility completed a $21 million upgrade, part of which included about $1.2 million for six covers for the primary clarifier and a duct system to pull odorous gas from the clarifier tanks and then "scrub" the gas with chlorine chemicals to remove the strong smell.

DU spent $5,500 last year to install a spraying system, somewhat like a large air freshener, to apply a mist on the sludge as a masking agent.

Borden said he expects the consultant will suggest more covers over the scrubber unit that strips odorous sulfides from the sludge.

"We can eliminate more of the smell, but it will be costly," Borden said.

That occasional pungent smell is not, however, nearly as bad as the odor that spread throughout the city when the boiler tubes broke.

Borden said the plant has two hot-water boilers with 182 tubes each. The boilers heat sludge taken out of the water before it goes into four digesters, creating methane gas. The boiler tubes quit, however, and stopped heating the sludge.

He said when a malfunction occurs, workers can burn off some of this gas. But the plant was producing too much sludge, creating a methane release through vents and sending the rank smell into the city.

Borden said he isn't sure what caused the malfunction, but it could have been faulty welding during installation in 2000.

DU crews got one of the boilers running again. Borden said that would be enough right now with the cool spring weather, giving them time to correct the problems.

Board member Hugh Hillhouse suggested the utility buy or have access to additional boiler tubes in case both boilers malfunction again at a time of year when both are needed.

In other sewer news, the utilities board approved spending $85,198 to install the first of two Vapex V1500 Hydroxyl Ion Control Systems at the Baker's Creek Wastewater Lift Station to reduce scum, grease, corrosion and odor. The cost includes a fence around the station.

In a memo to the utilities board, Borden said DU is spending $36,000 a year on ferrous chloride to reduce odor and prevent corrosion at Baker's Creek. Ferrous chloride is not, however, the most effective corrosion preventative. He said the Vapex unit should provide improved corrosion protection and smell reduction.

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