Dayton battling dangerous gas levels in its wastewater system

Dayton’s water department recently declared an emergency to buy equipment and supplies to try to reduce dangerous levels of hydrogen sulfide in the wastewater collection system, but officials said the general public is not in danger.

The city of Dayton says the hydrogen sulfide concentration in a sewer interceptor on Wagner Ford Road has surpassed 2,000 parts per million (ppm), which is far higher than the level at which the gas is toxic and can be lethal, the city said.

Hydrogen sulfide levels above 100 ppm are life-threatening. The colorless, flammable and extremely hazardous gas is known for its "rotten egg" smell. It's also called sewer gas, sour gas or stink damp.

But the city of Dayton is working with companies Cargill and Tate & Lyle to try to fix the problem.

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The companies have industrial facilities along Wagner Ford Road, near Needmore Road, and hydrogen sulfide control efforts involving the two companies date back 25 years, according to city documents.

Hydrogen sulfide build-ups are concerning but do not pose a threat to the public because they are in the underground system, said Michael Powell, Dayton’s water department director.

The dangers are to crews that need to work in the sewers, but staff rarely need to enter the sewers for repairs because the city has equipment that can be operated remotely, Powell said.

Hydrogen sulfide has a foul odor, but the odors aren’t making it out of the system, he said.

The more pressing concern is that gas is eroding the sewer piping, shortening its lifespan, Powell said.

“We want to reduce it so not only is it a safe work environment, but also so it maintains the integrity of the sewer as well,” he said.

Since the start of the year, the city of Dayton has been in talks with Cargill and Tate & Lyle about ways to control hydrogen sulfide in the sewer system.

The city is planning to spend $850,000 on a plan that involves feeding Magnesium Hydroxide in the sewer and installing valving and piping to try to cool the interceptor and discharge. Cargill and Tate & Lyle have agreed to help fund the efforts.

Other potential measures for reducing hydrogen sulfide include industrial companies pre-treating their discharge to remove some of the sulfur-causing components, but that tends to be costly, Powell said.

Last year, the city agreed to accept a nearly $1.5 million settlement with Cargill over discharge issues that resulted in sewer blockages and foul odors.

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