Could all wastewater treatment plants someday become energy neutral? The goal may sound unobtainable, but with the right technology, investments, and innovation it may not be.
According to the American Biogas Council, the wastewater sector consumes 22 terawatt hours of electrical energy each year, but has the potential to generate 851 trillion BTU of energy annually. “The wastewater industry could harness that energy and eliminate its net-consumption, generating excess energy for other uses at a competitive price. We have the equipment and processes available and ready for market,” writes the council in a fact sheet called “Energy from Wastewater.”
“Wastewater contains nearly five times the amount of energy needed for the wastewater treatment process — the majority in the untapped area of thermal energy.”
WWTPs have several options when its comes to energy recovery. These include anaerobic digestion, thermal conversion, heat recovery, microbial fuel cells, algae bioreactors, and hydro turbines, according to the paper *”Energy Production and Efficiency at Wastewater Treatment Plants” written by Allison Deines, Director of Special Projects Water Environment Research Foundation (WERF).
These energy conversation measures offer a variety of energy savings. According to Deines, the energy savings range for aeration system optimization is -15 to 38 percent, the energy savings range for the addition of pre-anoxic zone for BNR is -4 to 15 percent and the flexible sequencing of aeration basins has an -8 to 22 percent energy savings range. Those are just a few of the energy savings measures a WWTP can implement.
Recovering energy from wastewater treatment benefits both the WWTP and society as a whole.
According to the American Biogas Council, waste energy recovering has the potential to cut back on the amount of CO2 entering the environment by an estimated 18,000,000 tons, it can eliminate transmission losses by providing little or no outside power to the 100 largest facilities, it can reduce the number of power plants needed, and it can create more, local high-paying jobs in the wastewater sector. There is enough potential energy in wastewater that WWTPs could not only produce the energy needed to treat their water, but also help heat and power the cities that depend on them, reports the American Biogas Council.
They propose that investing $4.8 billion in the 100 largest wastewater facilities would make them energy neutral and could eliminate 17 percent of the wastewater industry’s energy use.
“With such an investment and using available technologies, the wastewater industry can become energy neutral today,’ writes the American Biogas Council. “With more resources devoted to research, the wastewater industry can hope to harness thermal resources and become a net energy exporter in the near future.”