Biofilm growth on cohesive sediment deposits: laboratory experiment and model validation

Abstract

Biofilm growth on cohesive sediment deposits plays a crucial role in the inherent properties of aqueous environment, such as the biostabilization of sediment deposits, sediment-associated contaminant transport, and habitat change. Here, a specially designed cylinder was used for biofilm cultivation under static water (with sediment sizes of 0.02–0.05, 0.05–0.1, and 0.1–0.2 mm) and dynamic water flow conditions. A biomass dynamics model, including the accrual term and detachment term (velocity-dependent and/or autogenic), was proposed to study the effects of sediment size and hydrodynamic condition on biofilm growth. The results showed that more biofilm formed on fine sediment than coarse sediment due to the greater surface area for bacterial attachment and nutrients accumulation. Increased flow velocity inhibited biofilm accumulation and a greater velocity caused more velocity-dependent chronic detachment, resulting in less biofilm growth on sediment particles. Under static water condition, there was more biomass compared with dynamic water flow condition. The proposed model can reasonably reflect the evolution of biofilm growth, as well as the effects of sediment size and hydrodynamic condition, which might be applied for the management of natural aqueous systems.