A Whiff of Spring

Travelers along the Exit 4 interchange on Interstate 93 caught a whiff of it. And some abutters have had enough of it. What, dear God, is that smell?

Calls were placed to the town of Derry because, as WMUR's Josh McElveen put it, something was amiss with the "Derry air."

The local noses were not deceiving them.

The "facultative aerated lagoons" that are a key part of Derry's wastewater treatment facility have had an uncommonly potent spring, according to Mike Fowler, Director of Public Works for Derry.

"This has been the most severe year," Fowler tells Patch.

There are typically occasional odors from the lagoons, where are tucked in close to the clover leaf of Exit 4 (see Google map attached). It is natural – just as natural as the breakdown and reduction of pollutants and restoration of oxygen in the lagoons. The wastewater is retained within the lagoon system for about 60 days to "properly remove harmful bacteria and other microorganisms," according to the Derry wastewater treatment plant.

This odor of late is due to recent temperatures, as well as other factors, including amount of rainfall, humidity and wind direction. With the warmer weather this spring, the sludge at the bottom tends to float to the top, Fowler explained in the interview with Patch.

The treatment plant will continue to monitor levels of dissolved oxygen and, as necessary, pump air into it with a mechanical blower system.

It's a biological process, and a balancing one. Fowler compared it to a recipe. Pumping too much air into a lagoon is as bad as pumping too little. So they monitor it – the ingredients plus the aerated actions –and look for that sweet spot.

Nearby travelers and residents need not have to hold their breath – or their noses – for much longer. Fowler says the warmer weather over the weekend should help settle the sludge, and the issue.