Energy Efficiency

The U.S. EPA has estimated that conventional wastewater treatment plants account for 3 percent of the entire U.S. electrical demand and that the demand for electricity at these plants is expected to grow by approximately 20 percent over the next 15 years. Depending on the scale of the wastewater treatment system, RAC technology-based wastewater treatment systems can require 50 to 75 percent less energy to operate than other biological processes. Additionally, systems utilizing rotating photosynthetic algal contactor wheels typically generate 95 percent less waste solids that would require energy intensive handling and disposal transportation costs. Thermal processes can be used in conjunction with larger RAC-based systems to generate significant amounts of renewable energy.

Solids Handling

By design, RAC-based systems generate more biomass solids than traditional systems. RAC-based systems leverage the nutrients in the wastewater to maximize biomass production. The ultimate goal being to generate enough biomass to make thermal processing of the biomass economically feasible for wastewater treatment plants. Thermally processing this btu-rich biomass algae and solids mixture generates significant amounts of energy, while reducing the waste solids by 95 percent or more and leaving valuable byproducts. For smaller package plants, algae biomass can be dried and used as "green coal," fertilizer, or can be processed through a digester. More becomes less, and overall waste solids handling expenses and risks are dramatically reduced or eliminated.

Wheels with algae growth Photo: Jackson Bishop