Development and evaluation of compact aquaculture system for the application of zero water-exchange inland aquacultures

Abstract

This study evaluated the performance of land-based compact aquaculture system integrating fibrous nitrifying biofilters and solid removal unit. The first experiment indicated that the compact aquaculture system with total biofilter length of 6.0 m and single solid separating was able to accommodate aquaculture weight as high as 5.0 kg/m3, which corresponded to nitrogen loading rates of 8.4 mg N/L/day. In the second experiment, more effective solid-liquid separation and good water quality were achieved when solid separating unit was replaced by filtration unit with Japanese mats as filtered media, and cleaning of biofilters and filtration unit was conducted in every 4 days. Next, the compact aquaculture system was employed to cultivate tilapia without water-exchange for 60 days using the described strategies. TAN and nitrite were well below acceptable limit of 1.0 mg N/L; suspended solids varied between 20 and 35 mg SS/L; and harvesting fish weights were 10.4 kg/m3. Fish survival rate at 97% and average growth rate of 3.45 g/day were reported. Finally, solid removal remained the critical factor for successful aquacultures in the compact system even under extensive or semi-intensive aquaculture cultivation, and finally nitrogen mass balance indicated that nitrification-denitrification were main treatment pathways while solid removal only prolonged the activity of nitrifying biofilters.