The potential of producing heterotrophic bacteria biomass on aquaculture waste

The effluent from the drumfilter of a recirculation aquaculture system was used as substrate to produce heterotrophic bacteria in suspended growth reactors. The effects of organic carbon supplementation (0, 3, 6, 8 g/l sodium acetate) and of hydraulic retention times (11–1 h) on bacteria biomass production and nutrient conversion were investigated. Bacteria production, expressed as volatile suspended solids (VSS), was enhanced by organic carbon supplementation, resulting in a production of 55–125 g VSS/kg fish feed (0.2–0.5 g VSS/g carbon). Maximum observed crude protein production was ∼100 g protein/kg fish feed. The metabolic maintenance costs were 0.08 Cmol/Cmol h, and the maximum growth rate was 0.25–0.5 h−1. Ninety percent of the inorganic nitrogenous and 80% of ortho-phosphate were converted. Producing bacteria on the drumfilter effluent results in additional protein retention and lowers overall nutrient discharge from recirculation aquaculture systems.