East End plant contractor hit with million-dollar holdback

There are days when the stench around Sault Ste. Marie's East End is enough to knock a buzzard off a gutwagon.

The never-ending problem, City officials concede, relates to unresolved issues at the new East End Wastewater Treatment Plant.

And last night, the stinky mess landed back on the desks of City councillors, who decided to withhold a million dollars from monies owed North America Construction Inc. until the air has cleared.

Councillors agreed to allow the contractor to try fixing the problem by installing a steam humidification system.

They also decided to cover their backsides by holding back sufficient funds to construct a cover over the plant's biofilter and a stack next year if the contractor's changes don't work.

City Director of Engineering Services Don Elliot told council last night that the plant is essentially complete.

But he asked for and got a million-dollar holdback to make sure the biofilter - an air pollution control system employing microorganisms to treat polluted air - doesn't continue acting up.

"What's changed?" asked Ward 1 Councillor Steve Butland. "Do we have assurances the problem will be solved?"

Elliot said experts are telling him that changes North America Construction Inc. intends to make to the humidification system will most likely keep microbes in the biofilter happily reproducing, munching up noxious gasses on the wood pile that houses them.

"We have a spray system to put water in the air for the wood chips and the microbes that live on them," Elliot told SooToday.com after the meeting. "They require a fairly consistent temperature of about 20 degrees and relative humidity of about 95 percent to keep functioning efficiently."

Elliot said the spray system has been cooling the air and, when the weather cooled the air even more in January, microbes on the wood chips went dormant until they warmed up again.

But now, they're functioning just fine.

"The contractor plans to install a steam humidification system to avoid evaporative cooling," said Elliot. "The system has been proven to work in functioning biofilters in other locations."

Just to make sure, though, the City will hang on to enough money to cover the cost of putting a cover on the biofiltration unit.

"The bottom line is that if it doesn't work, then we will have the money to put a cover on it," said Elliot.

He also said that at least two, possibly three other sources of odour at the plant have been identified.

All three are being dealt with, Elliot said.

"The first is centrate from the dewatering centrifuge," Elliot said. "The second is sludge in the trucks."

The smell of sludge that's left after all the water is squeezed out of waste water is particularly, er, potent.

At the East End plant, sludge is loaded into trucks and taken to the landfill after it's thoroughly treated.

But it's no less stinky.

Elliot said that the room the sludge is kept in always smells bad.

When the doors are opened for trucks, the smell escapes.

"This is a sewage plant," Eliiot said. "Once in a while there is going to be an odour."

The third possible stinker that City stenchhunters are investigating is the fomenter.

But that device is not as high on the suspects list as the centrate and sludge, Elliot said.

Most of the air from the sludge room, the centrifuge room and the fomenter is put through scrubbers and duct work, and then passed into the biofilter for a final cleansing by microbes in a pit about one-and-a-half-metres deep filled with wood chips.

As long as the microbes are active, little or no bad odour should be able to escape the biofilter, said Elliot.

Problems occur with air that escapes the buildings through open doors instead of being processed in scrubbers and the biofilter, he said.