Dissolved Nitrogen Gas Removal on Irrigation and Power Projects
This research will address how large volumes of water that are supersaturated with nitrogen gas can be brought back into equilibrium with natural gas concentrations in the atmosphere. Gas bubble disease is caused by exposing fish to nitrogen supersaturation. This can be fatal to fish and other aquatic organisms or produce chronic symptoms that weaken the entire fish community. Dissolve oxygen is often insufficient in nitrogen supersaturated water and, therefore, may not EPA's recommendation of 5.0 milligrams per liter (mg/L) of oxygen (O[v2]). This program will address how to maintain water delivery and power generation that often create nitrogen supersaturation problems and how stripping of the nitrogen gas from water can improve the fishery and water quality.
Need and Benefit
Triploid grass carp (_Ctenopharyngodon idella Val._) are being used by Reclamation`s Alamosa Field Division to control aquatic weeds in the Franklin Eddie Conveyance Channel (conveyance channel). Although the triploid grass carp have been successful in removing aquatic vegetation in the lower portion of the conveyance channel, aquatic macrophytes and algae continue to be a problem in the upper two thirds of the channel because the grass carp cannot can live there or are not healthy because of the high nitrogen supersaturated water in the upper reaches of the channel. Grass carp, weakened by high levels of nitrogen, are washed downstream until they reach better water quality found in the lower portion of the channel. Therefore, the upper two thirds of the conveyance channel require additional maintenance and herbicide control of aquatic weeds and algae. A secondary problem then arises, as grass carp move downstream, the density of fish increases in the lower portion of the system and stress and unhealthy conditions develop, regardless of water quality. This is largely due to the lack of adequate food for the number grass carp as well as other fish species in the lower portion of the channel.
Eliminating or controlling nitrogen supersaturation has far-reaching consequences. In water systems where grass carp are in use, water delivery and aquatic weed control become hampered--thereby increasing maintenance cost and ultimately the cost of water delivered to clients. At reservoirs and outlet structures where nitrogen supersaturation is created by power generation or releases, a sport fishery can be jeopardized, such as Yellowtail afterbay on the Big Horn River, below Canyon Ferry Reservoir or at Ridgway Reservoir, and mitigation costs for the fishery or poor water quality reduce the potential profit made from hydroelectric electric power generation and/or water deliveries.
The development of Coanda-Effect Screens, microbubblers as well as other techniques and structures that could be developed to treat large amounts of water, quickly would have tremendous value nationally as well as internationally.
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This information was last updated on May 3, 2015
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