A new system that treats, filters and conserves water in fresh-water fish tanks has been developed by an Agricultural Research Service scientist and is being used at an ARS research facility in West Virginia.
The new system recirculates up to 90 percent of the water in two fish culture bays at the ARS National Center for Cool and Cold Water Aquaculture (NCCCWA) in Leetown, W.V.
ARS environmental engineer Brian Brazil custom-designed the system to support multiple rearing tanks, which are connected to a centralized water filtration and treatment system similar to that constructed by the Conservation Fund's Fresh Water Institute. The rainbow trout raised at the Leetown center are part of a selective breeding program and require a continuous supply of high-quality water.
Brazil's design supports two culture bays. When the water leaves the bay's fish tanks, it flows through a microscreen that removes fine particulate matter, and then through a biofilter that removes lethal wastes like ammonia and nitrites. In the next stage, carbon dioxide is removed from the water and oxygen is added before the water enters a storage tank. Finally, the water is treated with ultraviolet light for purification before returning to the fish culture tanks.
The system was designed to maintain water quality while recirculating up to about 90 percent of the culture water. This helps with conservation, because only 10 out of every 100 gallons of water used is fresh.
The system also cools the water to temperatures that rainbow trout need to survive--ideally, around 55 degrees Fahrenheit. Recirculated water is generally warmer than that, so chilling the fresh water as it's added reduces the temperature. Adding this fresh water helps maintain high water quality.
Brazil's innovation has cut NCCCWA's demand for fresh water at a time when fish culture activities have increased. As a result, NCCCWA is more efficient at utilizing its water resources.
ARS is the U.S. Department of Agriculture's chief scientific research agency.