Organic Carbon Decay in Stream with Biofilm Kinetics

The importance of sessile microbial populations in aquatic environments has been recognized for many years especially the heterotrophic slimes under polluted conditions. However, models proposed by previous researchers to predict substrate decay rates have been based on first order or Monod kinetic expressions describing substrate utilization by suspended biomass. The investigation carried out looks at two important aspects of organic carbon modeling in a shallow stream: (1) It compares the importance of suspended microbial populations to the biofilm community and (2) it determines the kinetics of organic carbon uptake rate by river biofilms using an artificial stream channel. The results confirmed the dominance of attached microbial films in removing organic carbon in a shallow turbulent river. The study provided the organic carbon uptake rate $\left(R_B\right)$ and the net scour rate $\left(R_D\right)$ for the biofilms while establishing the validity of first order kinetics in a specified range of substrate concentrations, flow velocity and temperature. Mathematical models were formulated and verified under steady state conditions for the organic carbon and biomass change below a sewage outfall in a selected river system.