LABORATORY EXPERIMENT AND NUMERICAL COMPUTATION OF GROWTH OF PERIPHYTON ON FLAT CHANNEL BED

摘要

Laboratory experiments on the growth of periphyton were conducted in 4 juxtaposed laboratory channels to identify the effects of hydraulic conditions on the growth of periphyton. The environmental conditions, such as light, water temperature and concentrations of nutrients, were controlled to be exactly the same in all 4 channels, but each channel was subjected to different hydraulic conditions. Filament-type periphyton proved to be dominant for the case where the bed slope is large. This condition also induced a larger specific growth of periphyton. The detachment of periphyton from the channel bed was found to be more closely associated with the physiology and the species composition of the communities of periphyton rather than with the shear stress due to the flow. A numerical simulation model is presented to describe the growth of periphyton in details, in which the effects of hydraulic conditions on the periphyton growth is taken into account via the turbulent diffusion of substrate in the periphyton biofilm. The model predicts the temporal increase of periphyton biomass at the early growth stage fairly well.