Kinetics, design and biomass production of a bacteria reactor treating RAS effluent streams

The kinetics and design of a suspended bacteria growth reactor, which can be integrated in a 100MT African catfish farm, were determined. Such a reactor converted nitrogen (N) and phosphorus (P) from RAS effluents into heterotrophic bacteria biomass. The determined kinetics were: yield = 0.537 g VSS/g C; endogenous decay coefficient = 0.033 h−1; maximum specific growth rate = 0.217 h−1; half-velocity constant = 0.025 g/l; maximum rate of substrate utilization = 0.404g C/g VSS h. A reactor integrated in a 100MT farming facility would have a volume of 11 m3, based on a minimum HRT of 6 h. The kinetics and reactor design were integrated in a model to predict the VSS production (volatile suspended solids as measure of bacteria biomass) and nutrient conversions. The VSS production was on average 187 ± 2 g VSS/kg feed and the inorganic nutrients (N and P) were removed with an efficiency of 85 ± 3.0% and 95 ± 2.5%, respectively. A carbon (C) supplementation level of 455 g C/kg feed was required to ensure optimal C:N ratios for heterotrophic bacteria production. The production of heterotrophic bacteria biomass is, therefore, a prospective tool to lower nutrient discharge and to increase nutrient retention and sustainability of RAS in the future.