In a study, “pre-fertilization” in the nursery phase of a biofloc system for shrimp was tested. The objective was to accelerate the biofloc formation to minimize ammonia concentrations, avoiding high peaks during culture.
Since un-ionized ammonia-nitrogen and nitrite-nitrogen are toxic to most finfish, controlling their concentrations in culture tanks is a primary objective in the design of recirculating aquaculture systems.
Ammonia nitrogen occurs in aquaculture systems as a waste product of protein metabolism by aquatic animals and degradation of organic matter, or in nitrogen fertilizers. Exposure can reduce growth and increase susceptibility to diseases in aquatic species.
Shrimp exposed to high concentrations of nitrate exhibit shorter antennae, gill abnormalities and hepatopancreas lesions. Nitrate toxicity is more of an issue for shrimp raised in lower-salinity waters.
Healthy populations of both ammonia- and nitrite-oxidizing bacteria must be present in aquaculture systems to support the nitrification of potentially toxic ammonia to nitrite, with further oxidation to less problematic nitrate.
Despite their relatively small footprint, low-space bioreactors deliver sustainable and cost-effective biological wastewater treatment, particularly in recirculating aquaculture systems, where ammonia removal is critical.