Gas = Electric

By Charles Sowell  

MARCH 19, 2010 9:21 a.m. (0)

The Upstate’s largest sewer treatment authority is entering the design phase of a $2.6 million project to generate electricity using methane gas, said Ray Orvin, executive director of Renewable Water Resources.

Part of the cost for the authority’s project will be offset by a $500,000 grant from the state Energy Office.

The authority, also known as ReWa, plans to start with a $1.6 million project at the Mauldin Road treatment plant and carry it through with a similar facility at the Pelham Road plant, said Glen McManus, director of operations.

“We also plan (eventually) to install a low flow turbine at Pelham since we have a good bit of drop between our plant site and the Enoree,” Orvin said.

Methane is a natural byproduct of the digestive treatment process used by ReWa to treat raw sewage and the agency currently uses part of the methane to heat water which is, in turn, piped through a water exchanger to heat the treatment tank to an optimal temperature for processing the waste.

“Think of it as a high-tech digestive system,” said McManus. “Like our own digestive tract it performs best at a certain temperature.”

ReWa’s technical staff has even experimented with the digestive reprocessing tank and found a way to maximize methane production by the bacteria used to “eat” the sewage.

Normally methane produced from sewage treatment is burned on a tower, a process called “flaring.”

People who drive by the Mauldin Road plant at night can clearly see the brilliant yellow flame roaring above the facility.

If the agency is able to bring its plans to fruition that flare will go dark in the foreseeable future as all of the methane will be piped into a power generating station, similar in function to Greenville County’s generating station at the old Enoree Landfill.

“We haven’t settled on just what kind of engines we’ll used to drive the generators,” McManus said. “We’ve got several options including a kind of turbine that would fit in a small cabinet.”

In addition to the small size, the turbine would be fairly quiet when compared to the massive reciprocating Caterpillar G3520 engines used at Enoree, he said.

Orvin said that, after figuring costs and financing, ReWa expects to turn a $250,000 yearly profit from selling power back onto the electric grid, or by using the electricity to power the agency itself.

“Either way it will be a win for our customers, the environment, and for ReWa,” he said.

Methane is one of the most potent greenhouse gases, Orvin said.

Orvin said state lawmakers recently approved a bill to change ReWa’s charter to allow it to branch out into areas like power generation and selling treated wastewater for uses like irrigation through a purple pipe system.

“The bill is sitting on the governor’s desk, the last I heard,” Orvin said.

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