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The area of Alabama 20 in Northwest Decatur has been plagued by foul odor coming from the Decatur Utilities waste treatment plant.
Daily photo by Emily Saunders
The area of Alabama 20 in Northwest Decatur has been plagued by foul odor coming from the Decatur Utilities waste treatment plant.

Getting rid of a foul smell
$8 million
stench solution

Engineering firm identifies
Decatur plant's odor problem

By Catherine Godbey
cgodbey@decaturdaily.com 340-2441

Decatur Utilities may soon solve the mystery and the problem of the foul odor.

The investigators, ADL Inc. Engineering Services, analyzed the wastewater treatment plant, searching for clues to locate the guilty.

After a five-month investigation, ADL identified the culprit and proposed a solution for the problem plaguing the plant.

It is an $8 million solution.

The mystery began a year ago when the rotten egg odor, created by hydrogen sulfides, intensified. By March, the odor infiltrated Northwest Decatur and engulfed the neighboring communities, passing cars and school.

"This was one of the worst wastewater plant odor problems I've seen," Joe Downey, president of ADL said.

Resident Marjorie Ducate agreed.

"Last year it became intolerable. It smelled like dead bodies," she said. "It's not nearly as bad now as it was."

An ominous black purple haze, odorous black waste matter and increased ammonia levels were clues for the investigators.

Industrial waste problem

The conclusion: the wastewater treatment plant, initially designed to treat residential wastewater, was incapable of effectively treating the high levels of industrial waste.

Accounting for 60 to 70 percent of the plant's intake, industrial wastewater, taxed with hard-to-treat chemicals, bombarded the plant. Chemical tests revealed an excess of ammonia, depletion of oxygen and an elevated use of chlorine, resulting from the industrial waste burden.

Downey presented ADL's optimization study to members of the DU board last month. ADL's solution focuses on replacing deteriorating equipment and establishing an industrial pretreatment ordinance.

These proposals accompany changes the plant made in the spring that decreased the amount of time the wastewater spent in the plant.

"From ADL's preliminary recommendations, we reduced the number of primary clarifiers from 6 to 2," DU Interim General Manager Stan Keenum said. "The longer you hold the wastewater, the more likely hydrogen sulfates will transform to sulfides."

DU, however, wants to increase the plant's productivity, not just eliminate the stink.

"People think that if they don't smell it, everything seems to be OK. That's not the case, we actually want to fix the problem," board member Hugh Hillhouse said.

In response to ADL's study, DU plans for immediate action, which includes expenses totaling $850,000 in the fiscal year 2008.

More than 70 percent of the costs will fund replacing the air diffusers at the aeration basin, a section of the plant where bacteria consume the waste. The air diffusers provide the bacteria with oxygen, which keeps them healthy.

"We want active teenage bacteria, their appetites are endless," Downey said. "They are like human teenagers who eat one Big Mac after another."

Ammonia levels and chlorine consumption heightened because the bacteria struggled to consume the waste.

By keeping the bacteria healthy, they will eat more waste and decrease the amount of ammonia, which accompanies the waste. Reducing the waste also results in lowered amounts of chlorine, a chemical used to treat the waste remaining in the water.

Along with addressing issues internally, DU searched externally to lessen the impact of industrial wastewater chemicals on the plant. Discussions about how industries affect the plant resulted in an Industrial Pretreatment Ordinance.

According to Keenum, the ordinance monitors the chemical level of industrial wastewater and allows DU to recover expenses required to treat wastewater heavily induced with chemicals.

DU would initiate a surcharge fee to industries exceeding the permitted chemical level.

Either the industries will abide by the regulations or cover the costs of treating the chemicals.

With a plan established to deal with the past, questions about the future filled the room.

"What can we do going forward to avoid getting in a situation like this again?" Glynn Tubb, board secretary, asked.

"The pretreatment ordinance is critical," Downey answered. "Decatur (Utilities) is very lenient on industries, which helps to attract them to the area but hurts the treatment plant."

Along with the ordinance Gary Borden, DU's gas, water and wastewater manager, said DU would create a pretreatment coordinator position for the plant and increase chemical sampling.

The impending plant and policy changes will address the odor issue and also prepare the plant as it applies for a renewal of its national pollutant discharge elimination system permit in 2009.

The NPDES permit, which lasts five years, regulates water pollution by monitoring the chemicals present in discharged water.

During the recent odor situation the plant never exceeded the permit levels. With a new permit, however, NPDES may impose stricter guidelines, Downey said. Making changes to the plant now will help decrease chemical levels and prepare the plant for potential permit alterations.

Ducate supports DU's efforts to improve the plant.

"We love them as neighbors, as long as they don't stink," she said. "They just need to do what they have been doing just even better."

With the investigation closed, DU will begin implementing the recommendations and determine whether ADL solved the case.

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