Improving Energy Efficiency and Performance of Wastewater Recycling

This project advanced the science and engineering of the raceway pond process, an algae based wastewater treatment technology that has lower electricity usage than conventional  activated sludge processes and better treatment performance than conventional treatment  ponds. The principle underlying raceway ponds is the ability of green microalgae to use  sunlight through photosynthesis to facilitate wastewater treatment. Instead of relying on  energy-intensive mechanical aeration to oxygenate the wastewater, microalgae use  photosynthesis to provide a part of the oxygen needed for treatment of bacteria in wastewater  to break down the organic matter and transform ammonium. While raceway ponds are already  proven to accomplish secondary treatment at full scale, advancements developed and tested  during this project increased their nitrogen removal capability.

These advancements were developed and tested at laboratory, pilot, and full scale. Process  improvements developed at pilot scale were implemented at a community facility in California’s  Central Valley, including equipment additions and process modifications to maintain sufficient  dissolved oxygen, increased algal and bacterial concentrations, and including a filtration stage  of treatment. The resulting effluent quality produced by raceway ponds is intended to meet an  annual average discharge limit of less than 10 milligrams per liter of total nitrogen and the  requirements for disinfected tertiary recycled water, as defined in Title 22 of the California  Code of Regulations.