Simulation of biofilm formation at different assimilable organic carbon concentrations under lower flow velocity condition

A simulation model was established in this study to evaluate the impacts of assimilable organic carbon concentration on the growth of biofilm and bulk bacteria under lower flow velocity conditions. The experimental results showed that the growth trends of heterotrophic plate count bacteria of biofilm and bulk bacteria were coincident with the pattern of logistic growth model. The effects of the assimilable organic carbon level on the (specific) growth rates of biofilm and bulk bacteria were quite significant, and the higher the assimilable organic carbon level was, the higher the (specific) growth rate was. There was a growth and decline relationship between the maximum quantities of biofilm and bulk water bacteria at steady state. The maximum growth rate of biofilm bacteria exponentially increased with the increase of assimilable organic carbon level. The length of time that the maximum growth rate occurred was inversely decreased with the increase of assimilable organic carbon level. Some results of this study support the inference that the increase of bulk bacteria results mainly from the release or detachment of biofilm bacteria, not from the growth itself.