Wastewater Energy Consumption in a Nutshell
Water and energy resources are mutually linked. Satisfying water consumption requires energy and, often, in large quantities. For example, energy is needed for wastewater pumping, wastewater treatment, water distribution, water treatment, and discharge of wastewater. This is called water or wastewater energy consumption.
For many municipal governments, drinking water and wastewater plants are typically the largest energy consumers and account for 30 to 40% of total energy consumed. Nationwide, potable water and wastewater systems account for approximately 2% of energy use in the United States. This adds over 45 million tons of greenhouse gases to our atmosphere annually! However, wastewater treatment plants are the real energy hogs here. A 2013 study by the Electric Power Research Institute and Water Research Foundation reported that treatment plants consumed about 30 billion kilowatt-hours of electricity per year, or about 0.8% of the total electricity used in the United States. In California, it takes approximately 475-1,400 kWh of energy to treat 300,000 gallons of wastewater.
So how does the wastewater treatment process work?
Wastewater treatment involves four main steps: Primary treatment, Secondary treatment, Anaerobic Digestion, and the Disinfection phase. Primary treatment separates solids from liquid waste, while Secondary treatment has bacteria break down dissolved waste that contains ammonia and other pollutants. The remaining solids are then separated from the treated liquid. An anaerobic step occurs when solids from the primary and secondary steps are digested by microorganisms in a sealed tank without oxygen. Then finally, the Disinfection phase. Bacteria plays a key role in breaking down our sewage and industrial wastewater by consuming organic pollutants and inorganic nutrients such as ammonia.
However, they require certain conditions to thrive: optimal temperature, food, and oxygen. Getting bacteria, the oxygen they need requires one-quarter to half of the energy used by a wastewater treatment plant. Traditional plants pump air into the tank where the bacteria do their work, diffusing it through small holes to create oxygen bubbles the bacteria can access. This process wastes a lot of energy because most the bubbles rise to the top and pop without the bacteria using them. An example of this, can be read from our case study about the South San Francisco Water Quality Control Plant.
How can you reduce wastewater energy consumption?
Ironically, the organic matter found in wastewater contains up to five times as much energy as the treatment plants use. Despite all the energy seemingly there for the taking, reducing fossil fuel demand of treatment plants is challenging and requires myriad approaches. Utilizing energy efficient solutions could save money and reduce those greenhouse gas emissions. Today, the industry is experimenting with new technologies and evaluating them as energy and cost reduction measures.
For example, our PredictEnergy Analytics Software allows effective visualization for plant operators, enabling the process of wastewater at the lowest cost and creates wastewater energy cost savings. PredictEnergy’s analytics platform with near real-time data, provides a level of visibility into plant health like never before and further reducing costs by eliminating unnecessary downtime. Innovators, like PredictEnergy, are using a variety of technologies to reduce the electricity they use through energy efficiency and to generate electricity onsite to offset what they do use.
If you are a plant operator, how much energy does your water treatment facility use? Have you considered reducing your wastewater energy consumption?