July 25, 2012 By Michael Greenhouse
Editor’s Note: Michael Greenhouse is a writer and a member of the Ridgewood Environmental Advisory Committee, which advises the New Jersey village on environmental concerns, energy reduction and sustainability.
For years, Ridgewood, N.J., engineer Chris Rutishauser would look at the bio-gas flare coming from the water pollution control facility he oversees and lapse into a troubling thought: “There goes a lot of wasted energy — a lot of money.”
Now, thanks to some creative thinking by Rutishauser and facility superintendent Robert Gillow, and some careful planning by leaders in Ridgewood, a project is under way that will capture that energy, shrink the facility’s carbon footprint, and cut its operating costs.
Ridgewood’s Sustainable Energy Project will cost the village’s 26,000 residents nothing. And it reaches beyond the energy needs of the water pollution control facility itself, potentially serving as a catalyst for the village’s longer term vision for sustainability.
An Anaerobic Overhaul
From 2002 to2005, the facility was completely overhauled to meet stricter federal and state environmental standards. It now features two anaerobic “digesters” that break down and reduce the amount of organic waste that must be processed and disposed of by the plant. The digesters create methane bio-gas. Some of this gas is cycled back into the digesters to heat and break down the sludge. The rest is safely burned off into the air.
Despite these improvements, Rutishauser and Gillow still felt they could better harness the energy flowing through the facility and perhaps reduce the cost of running it in the process.
“It’s the largest consumer of energy that the village owns, costing upwards of $250,000 a year for natural gas and electricity,” Rutishauser said. “That’s a big cost and a big opportunity.”
The two began looking into an innovative new system that turns digester gas into reusable heat and electrical power. This Combined Heat and Power (CHP) system uses the bio-gas produced by the anaerobic digesters to both heat the sludge entering the digesters and produce power to run the plant. A number of waste water treatment plants in Europe have used CHP to become energy self-sufficient. A few large facilities in the U.S. are also using CHP to get closer to energy self-sufficiency.
The U.S. Environmental Protection Agency (EPA) has been evaluating the feasibility of CHP since the mid-2000s. In 2007, it published a report on CHP implementations at more than a dozen wastewater treatment facilities. The EPA concluded that “CHP is a reliable, cost-effective option for [wastewater treatment facilities] that have, or are planning to install, anaerobic digesters.”
At the time, the EPA said that CHP was a good option only for large plants with flow rates greater than 5 million gallons per day. However, in October 2011, an updated EPA report concluded that CHP could also be viable and cost-effective for smaller plants like the 3 million-gallon-a-day facility in Ridgewood.
Officials in Ridgewood believed they could get the same results with CHP. They also believed a CHP project could be a model for good environmental practices in the community and a platform for adopting renewable energy throughout the village.
And, just as importantly, they believed it could be done without any upfront capital outlays by the village — an important criterion for village officials.
In October 2011, New Jersey-based Natural Systems Utilities was selected and approved by the Ridgewood Village Council to perform project engineering and construction.
Engineering and hardware installation for the CHP system began this year. Natural gas-powered turbines will capture the excess gas, and generators will power the facility and keep the sludge heated at an optimal temperature.
Several New Energy Saving Technologies
During construction, the team will also install a new, chemical-free system for disinfecting the liquid effluent that is discharged from the plant after it has been treated. The system uses ultraviolet lights and eliminates the need to use chemical disinfectants during the treatment process.