Dynamics of liquid flow in an up‐flow reactor‐used for anaerobic treatment of wastewater

Abstract By means of stimulus‐response experiments with a Li + tracer, a description of the fluid flow in a 30 m 3 reactor, used for anaerobic treatment of wastewater, was derived. It appeared that of the three parts that could be distinguished in the reactor (the sludge bed. The sludge blanket, and the settler), the sludge bed could be described as a combination of two perfectly mixed regions with bypassing and return flows; the sludge blanket was perfectly mixed, while the fluid flow in the settler could be described as plug flow. From experiments performed under different conditions it was concluded that 60 m 3 gas/day were sufficient to provide good mixing and also that the height of the sludge bed should be 2–3 m. From this last conclusion it follows, e.g., that scale‐up of the 30 m 3 reactor should be done by increasing the cross section of the reactor while homogeneously distributing the influent over the bottom.