Saving Energy and Reducing Costs at Wastewater Treatment Plants

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As energy costs continue to rise, many water and wastewater treatment plants are taking steps to significantly reduce energy use. 

North Conway Water Precinct’s wastewater treatment plant in North Conway, N.H., is one example. The plant implemented a number of energy saving measures on the equipment operation and water distribution side, and also invested in renewable energy. 

“The single highest cost of treatment plant operation is electricity,” says North Conway Water Precinct Superintendent David Bernier. “Eight years ago it was 35 percent of our operating budget; today, it is less than 18 percent.” 

The plant achieved this in a number of ways:

  • Pumping water at night when electrical rates are lower, reducing their electrical cost from 36 percent to 12 percent of the budget
  • Using efficient blue chip motors, many coupled with variable-frequency drives, saving $12,500 per year
  • Installing solar panels that generate about 22.5 percent of the plant’s consumption, saving $65,000 per year
  • Using geothermal wells for cooling in summer and heating in winter
  • Purchasing their power directly from the wholesale supplier, saving 5 to 8 percent in electrical costs 

The first steps 

Plants wanting to reduce energy can first benchmark their energy use, then perform an energy audit to see how they can operate more efficiently, and finally, implement the audit’s recommendations. 

Power providers, consumer organizations and regional WEF and other professional organizations can provide assistance. The U.S. EPA offers energy-efficient equipment, technology and operating strategies (www.epa.gov/region9/waterinfrastructure/technology.html). 

Many plants start by replacing older, less efficient motors and motor systems, installing variable frequency drives, switching to energy-efficient lighting and controls, and upgrading heating, cooling and ventilation systems. 

The Massachusetts Water Resources Authority (MWRA) saved $24 million a year with an energy program. They installed setback thermostats, motion sensors and an intermittent circulation heating system. More efficient lighting and motion sensors alone saved MWRA’s John J. Carroll Water Treatment Plant $24,000 a year in electrical costs and paid for itself in two years. 

Operational changes 

Changing the way your plant operates is another way to save energy:

  • Manage your electrical load by reducing peak demand
  • Shift to off-peak hours and improve the power factors of motors
  • Switch to sustainable biosolids treatment, transportation and end use 

In most treatment plants, aeration is a large energy user. The Jackson, Wy., wastewater treatment plant replaced its 75 and 40 hp aerator mixers with 50 and 25 hp models, and replaced the 250 hp fixed speed blower with a high-efficiency 150 hp variable speed blower. This has reduced the annual demand of 5.9 million kWh by about 1.95 million kWh and saved the plant around $85,000 a year. 

Renewable energy 

An increasing number of water and wastewater treatment plants are investing in renewable energy, such as solar, hydro, wind and geothermal. 

The Chelmsford (Mass.) Water District is one example. “Because our facilities were all pretty new, there wasn’t much we could do at that level, so we started looking at renewable energy,” says Environmental Compliance Manager Todd Melanson. Melanson attended an energy roundtable with the state DEP, the EPA and the University of Massachusetts, where he picked up some useful advice. 

Today, a solar array at the district’s Crooked Spring Water Treatment Plant is saving around $154,000 a year on electricity. The plant earns a renewable energy credit for every 1,000 kWh generated, for an annual savings of $30,000, in addition to the 54 percent reduction in electricity use. 

Nearly 50 percent of the energy used at the MWRA’s Deer Island Wastewater Treatment Plant is generated on site, and solar panels at the Carroll plant produce 5 percent of electricity used each year. Methane capture cogenerated at the Deer Island plant replaces around 5 million gallons annually of diesel fuel used for process heating, and over 27 million kWh ($2.8 million savings) in electricity. Hydroelectric power supplies 23 GWh ($1.8 million savings), while wind and solar annually provide 5 GWh ($580,000 savings) and 1.4 GWh ($240,000 savings), respectively. 

“Renewable energy projects and on-site power generation has yielded energy savings and revenue of around $177 million since 2001,” says MWRA Director of Planning Stephen Estes-Smargiassi. “Facility energy audits, energy-efficient design for new facilities, and using green technologies in power, vehicles and computing have saved $1.9 million a year over the past five years, with a one-time capital investment of only $2 million.” 

Funding sources 

Treatment plants have found various funding sources for energy projects, including:

  • Utility rebates
  • Energy cooperatives
  • Federal grants, loans, rebates
  • State Revolving Fund (SRF) loans
  • City and county aid grants 

Funding for the North Conway Water Precinct’s solar panels and geothermal wells came from American Recovery and Reinvestment Act (ARRA) grants and the New Hampshire Revolving Loan Fund. 

Money for the MWRA’s energy projects came from a variety of sources. “When the ARRA was announced, MWRA had a number of projects ‘shovel ready,’ ” says Estes-Smargiassi. “Of the $33 million in ARRA funds we received for water and sewer projects, nearly $10 million of that was used for renewable energy projects.” The authority also received over $2.5 million in state grants and around $680,000 in energy-efficiency project rebates. 

“Have a strategic plan for funding and look at all sources,” Bernier suggests. “Be sure and ‘sell’ your project to the public, your elected officials and the funding agencies.” 

Employee buy-in 

The Water and Wastewater Energy Best Practice Guidebook, funded by Wisconsin’s Focus on Energy (a part of the state Department of Administration), also recommends educating treatment system personnel in the relationship between energy efficiency and facility operations. Engage operators in the process by asking for input. The Carroll plant saved $200,000 per year after operators suggested eliminating the sodium carbonate mixers. 

“The green power and increased efficiency has been embraced by our staff, and we think about energy from reservoir to outfall,” says Carroll Plant Manager Dave Coppes. “Meeting regulatory targets is a given, but meeting energy targets is a way for operators to excel.”

Check out a full profile on the North Conway (N.H.) Water Precinct in the October print issue of Treatment Plant Operator



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