Wastewater treatment plant generates clean water and energy

ROCKFORD — The Rock River Water Reclamation District's electric bill was as high as $80,000 per month in 1998. Today it's about $55,000 per month.

"That's a staggering savings when you consider how much inflation has taken the price of power up during the same period of time," said Larry McFall, RRWRD plant operations manager.

Driving the district's power consumption down is its ability to convert waste to energy in its state-of-the-art co-generation facility, an onsite operation where a single fuel source, such as natural gas or in RRWRD's case, methane gas, is used to produce electrical and thermal energy.

The main component of the co-generation facility is a commercial-size digester, which breaks down "sewage sludge" or solids.

"The beauty of putting solids in a digester is two-fold," RRWRD Executive Director Steve Graceffa said. "One, the digester is going to consume 40 to 50 percent of what you put in there. It gets consumed by the bacteria that eats the sludge, and two the byproduct of that is making methane gas. So, not only did you reduce your volume, you've made a byproduct of gas."

The methane gas is used to fuel engines, which make electricity, and the heat generated from the engine is funneled back into the digester to keep the bacteria alive. Nutrient-rich solids also are used as fertilizers while other bio-degradable solids are taken to a landfill.

Typically, an onsite co-generation system is more efficient than a utility-operated power plant because thermal energy that would otherwise be wasted is captured and used at the facility for a more efficient use of fuel. Graceffa said the energy savings is passed on to RRWRD customers.

The Rock River Water Reclamation District covers nearly 100 square miles of Winnebago County and serves more than 240,000 people. The district has about 1,100 miles of buried sewer lines that extend from residences, industrial sites and other businesses to the Kishwaukee Street treatment plant in southeast Rockford where about 30 million gallons of wastewater a day is processed.

Graceffa said the treated water meets or exceeds EPA guidelines before most is discharged into the Rock River. Treated water also is used to help heat and cool the district's 40,000-square-foot office administration building.

The award-winning facility, completed in 2009, received Leadership in Energy and Environmental Design or LEED Silver certification in 2010.

Certification took into account conservation requirements such as materials used during construction, how the trash was handled, storm water drainage, the availability of bicycle parking and a bus route, as well as how the building is heated, cooled and lit, Graceffa said.

The administration building features seven rain gardens to reduce and reuse storm runoff. Inside is a 6-by-16-foot interactive replica of the treatment plant's layout and the sequential steps in processing solid and liquid waste and generating energy as a byproduct of that process.

Chris Green: 815-987-1241; cgreen@rrstar.com; @chrisfgreen