Photoelectrocatalytic Oxidation Removal of Ammonia for Aquaculture Systems

Aquaculture involves the farming of organisms in water. Aquaculture systems that produce aquatic organisms year round in a closed controlled environment require significantly fewer land and water resources than open systems like pond net-pen and flow-through culture systems. Closed recirculating aquacultures also yield minimal effluent discharge which decreases contamination of nearby areas. These characteristics allow for construction and operation almost anywhere including within cities and close to major markets. However these aquaculture systems are economically unfavorable due to the high costs of constructing and operating the complex systems needed for water circulation solids capture oxygenation and nitrogenous waste removal. Nitrogenous waste removal is one of the biggest challenges to economic feasibility. Many existing approaches take advantage of biological filters which use bacteria to filter out nitrogenous waste such as ammonia. However these biological filters have high concentrations of nitrates have to compromise between the ideal temperature of the aquatic life and biofilter bacteria and experience additional bacteria growth that clogs the filters. Biofilters also cannot be installed instantaneously because the bacteria need to grow into place. Therefore aquaculture production would benefit from a nitrogenous waste removal system that does not include biofilters. UW-Madison researchers have developed a water recirculation device that removes nitrogenous waste using photoelectrocatalytic oxidation (PECO). This device avoids the disadvantages of biofilters in recirculation systems to allow for increasingly efficient and cost effective aquaculture production. A photocatalytic anode and cathode are combined to form an electrolytic cell. The photoanode is illuminated with ultraviolet (UV) light to create a highly oxidative surface. Ammonia that comes into contact with the photoanode is converted primarily into nitrogen gas. The products can be controlled by applying a potential difference to the photoanode. Technology Applications: 1) Water recirculation systems 2) Aquacultures 3) Nitrogenous waste removal