Sewage Lagoons Leave Smell

Derry’s Deputy Director of Public Works said that a “rotten egg” smell coming from the town’s wastewater treatment plant lagoons will be dealt with as the “layers” of sewage blend in.

The odor was recognized by motorists in the Exit 4 area of Londonderry, and Londonderry officials identified the odor as coming from the Derry lagoons, which are part of the wastewater treatment system.

Thomas Carrier, deputy director of public works and supervisor of the treatment plant, said that “lagoon turnover” is a seasonal event. “Over the winter the lagoon waters get cold,” Carrier said in a phone interview. “The biological activity is less. In the spring the water warms, and the biological activity increases.”

The biological activity is released in gases, chiefly hydrogen sulfide, which release into the air, Carrier said. And the prevailing winds brought the odor to Interstate 93, the Market Basket area and other nearby businesses.

The lagoons are an aerobic method of treating waste and use air to help break down the raw sewage, Carrier said. The biological activity combined with the air break down the layers of sewage, he said. He said his operators have been measuring the level of oxygen in the area to make sure it’s adequate.

“Once we don’t have the multiple layers, the odor will disappear,” Carrier said.

Those wanting further information may call Public Works at 432-6144 or the treatment plant at 432-6750.