Downers Grove Wastewater Treatment Plant Achieves Net Zero

At SEDAC, we recognize the vital role water and wastewater treatment systems play in our mission to reduce the energy footprint of Illinois. These energy intensive systems account for about a third of a typical US municipality’s energy budget. SEDAC has found that wastewater plants participating in our energy assessment program use an average of 2,800 kWh per million gallons of water treated. In 2020 in ComEd, that would be equivalent to 1 metric ton of CO2 emitted into the atmosphere for every million gallons treated.

A combined heat and power engine.

Downers Grove Sanitary District is an exception! 10 years ago, the plant was an efficient but not outstanding facility. They used some bio-gas to heat their anerobic digesters but also purchased quite a bit of electricity and natural gas. Recognizing they had room to improve, the team doubled down on traditional energy efficiency improvements by switching to fine bubble aeration, adding turbo blowers, and retrofitting lighting. They even upgraded building heating to a water source heat pump using the steady temperature of the plant’s effluent to drastically improve efficiency. In all, site energy use dropped by about 33%. Read about all the plant’s efficiency improvements on their website.

Downers Grove Sanitary District did not stop at reducing their energy consumption, though. Noting that the plant’s anerobic digesters had additional capacity, the plant started accepting fat, oil, and gas (FOG) from local restaurants (for a dumping fee). The FOG doubled the digesters’ bio-gas production. For a total investment of $3.8 million (before grants and incentives), the plant was able to add equipment to clean and purify the gas for combustion in 2 new generators. With the electricity generated, the plant was able to gradually reduce their reliance on purchased energy. As can be seen in Figure 1, the plant ran almost entirely on bio-gas in 2021 with some electricity being returned to the grid. Downers Grove Sanitary District now sometimes receives checks from the utility company!

Figure 1. Energy Use at DGSD was reduced by energy efficiency measures from 2002-2012. After 2012, the district began accepting FOG and doubled biogas production. The system was refined to the point that this year, the plant has run almost entirely on biogas. The electricity below the zero line was returned to the grid. Data and chart courtesy of Downers Grove Sanitary District.
The District's Education Center

Downers Grove Sanitary District has done an amazing job of creatively engaging their community in the energy upgrade. The plant’s website is a great resource for learning about the energy production of the plant and improvements made, and they have created an informational space on site at the plant where visitors can learn about the system and upgrades while visiting. Further, the plant has creatively taken advantage of its location along a well-traveled commuter train line to educate the community about the net-zero wastewater plant. An energy score board informs community members about the system’s monthly energy production and use.

SEDAC thanks Amy Underwood, general manager of the Downers Grove WWTP, and the whole team for showing us the system and sharing their experience with us!

Image of equipment to clean and purify the biogas
Support from the Clean Energy Foundation helped purchase equipment to clean and purify the biogas

Is your WWTP or community ready to start your net-zero energy journey? Contact SEDAC for an energy assessment and support with incentives and grants. Or find more information about the Illinois Clean Energy Community Foundation’s Net-Zero Energy Wastewater Grant at www.illinoiscleanenergy.org. For plants who wish to apply, the first step is to contact the Foundation at 312-372-5191 to learn more and discuss your project before beginning the application.

The project was made possible in part by support from the Illinois Clean Energy Community Foundation’s Net-Zero Energy Wastewater Grant. The grant is open to all publicly owned and operated wastewater treatment facilities that have a path to net-zero energy. This includes grants of up to $500,000 per grant cycle for facilities that make a commitment to achieve and maintain site net-zero energy performance, make the energy performance publicly available, and provide public access for educational purposes.