Application of nitrification and denitrification processes in a direct water reuse system for pacific white shrimp farmed in biofloc system

Abstract The aim of the present study was to propose a low-cost nitrogen removal system through the nitrification / denitrification process in order to maintain the water quality required for the Pacific white shrimp superintensive cultivation in closed systems without water renewal. The increase in productivity consequently causes the accumulation of organic matter and nitrogenous compounds, especially ammonia nitrogen and nitrite, which in high concentrations can be lethal to aquatic organisms. In addition, the accumulation of solids in the system provides conditions for the emergence of opportunistic pathogens, microalgae booms, and increases the producer's cost of inputs to maintain the equilibrium physicochemical relationships required for shrimp farming. The experimental productive cycle lasted 36 days using Litopenaeus vannamei shrimps with 7.1 g ± 0.56 g and density of 350 shrimps m−³. The nitrogen removal efficiency observed during the study period was 71.3 ± 5.3 %, and the shrimp had a survival of 92.9 % and a final weight of 13.1 ± 1.4 g. Thus, we established a system (ammonia and nitrite), capable of managing solids without interaction with the sea, ensuring high biosecurity against exogenous diseases in marine shrimps farms.