The New Alchemy: Turning Waste into Energy

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The award-winning Southside Wastewater Treatment Plant commenced in 1964.  Since then, the plant has grown from less than 10 MGD to current permitted design of 110 MGD. Southside is one of the two wastewater treatment plants owned and operated by City of Dallas Water Utilities (DWU). Both plants are responsible for treating all of the wastewater generated by an estimated 1.25 million citizens of the City of Dallas along with eleven neighboring customer cities, which is about 260 MGD.

Southside stabilizes and disposes the biosolids generated by both of the City’s wastewater treatment plants. During the process of stabilizing the biosolids, methane (biogas) is produced as a by-product. Previously, the biogas was flared as a means of disposal, with only a small portion being used to generate hot water for plant needs. The Cogeneration project allows the City to recover and utilize all of the energy provided by the biogas.

The Cogeneration project is a twenty year lease agreement between the City of Dallas and Ameresco, Inc., in which Ameresco finances, designs, constructs, operates and maintains the cogeneration facility. The City of Dallas supplies the facility with approximately 1.3 million ft3 of biogas per day which is converted by engines into electricity and hot water. The electricity is sold back to the Plant and the hot water is returned to the plant’s hot water system and is used for heating purposes. The Cogeneration facility produces approximately 27,000,000 kWh/year which is sold back to the City at a cost of approximately 6.5 cents/kWh, less than what the City is paying for grid derived electricity.

Some Benefits of the Project Include:

  • The project generates Renewable Energy Credits (REC’s) which the City uses for LEED certification of City facilities.
  • The project will reduce the region’s overall emissions by eliminating the pollutants that would have been created by a power plant in the generation of 27 million kWh.
  • The Cogeneration Facility did not require any City capital upfront to construct. (Approximate cost to construct is $10 million dollars)
  • The Plant reduces its grid derived electrical needs by 27,000,000 kWh/year.  This is a 50-60% reduction for the plant and a 4% reduction by the City, as a whole.

DWU offers a way for its citizens to be a part of this waste-to-energy system through its nationally recognized Cease the Grease program (CtG).  CtG is an education and outreach program started in 2005 that helps Dallas rate payers to properly dispose of fats, oils and grease (FOG).  CtG also offers residential cooking oil recycling.  DWU has nearly 25 CtG drop-off stations where anyone can leave a sealed container of used cooking oil.  That oil is collected and taken to Southside and becomes part of the cogeneration process.  By having citizens being a part of the process, DWU has decreased grease-related sanitary sewer overflows by 93%.

Even after 10 years, CtG continues to get the word out by strong grassroots outreach, appearing on the local news, Facebook, Twitter, YouTube and a website.

CtG is still going strong and starting in February 2016 it will be the anchor for DWUs newest campaign, Defend Your Drains!  Check out what should and should not go down the drain by visiting our brand new website and Facebook page.

 

h_dulacHelen Cantril Dulac has been working in water since 1998 with the City of Worth Pretreatment Services. Then she went to Dallas Water Utilities in 2003 and worked for Pretreatment and Laboratory Services. She started in the Cease the Grease program in 2007 and helped launch the program into the national spotlight.  She left Cease the Grease in 2014 and is now with the City of Dallas Office of Environmental Quality on the Sustainability and Outreach Team. She graduated from Texas A&M University with a BS in Wildlife and Fisheries and a Master in Environmental Science from Texas Christian University. 

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