A novel fluidized bed respirometric technique for determination of in situ biofilm kinetics

Abstract

A respirometric approach has been developed to determine heterotrophic biofilm kinetics using fluidized bioparticles – particles with attached biomass. Lava rock particles of 600 μ m were used as a biomass carrier medium. The modified respirometer successfully estimates in situ biofilm kinetics of the bioparticles collected from a pilot-scale liquid–solid circulating fluidized bed (LSCFB) bioreactor. The observed maximum specific growth rates (μmax) of 3.69±0.44 d−1 and biomass yields (Y H ) of 0.36±0.03 g COD/g COD in the fluidized bed respirometers were significantly different from the μmax of 5.57–5.72 d−1 and Y H of 0.54–0.59 g COD/g COD observed in the conventional respirometric tests for bioparticles and detached biomass. The higher Monod half-saturation coefficient (K S ) of 186–219 mg COD/L observed in the fluidized bed respirometers relative to the 49–58 mg COD/L in the conventional respirometers reveals the presence of mass transfer resistance in the LSCFB despite fluidization. Significantly reduced yields in the fluidized bed respirometers and the estimated maintenance coefficient of 1.16 d−1 for the particulate biofilm in the LSCFB clearly emphasize that a substantial amount of substrate was utilized for cell maintenance at the low food to microorganism (S/X) ratio of 0.5 g COD/g VSS.