Author(s): Thomas Rosch; Frank Tonsmann
Linked Author(s):
Keywords: Hydro power; Reaeration; Gas bubble disease; Oxygen; Supersaturation
Abstract: Lack of oxygen used to be a severe problem in many rivers. Today this problem is almost solved. But there is still not all clear for the environment because the so called gas bubble disease caused by supersaturation is spreading. This disease leads from damages to gill, to paralysis up to death of aquatic life. Despite the problem of supersaturation oxygen deficits still occur in some places. Especially downstream of damms or reservoirs, which are stratificated in summertime, oxygen deficits occur every year. The outflowing water, which is usually almost oxygen free takes a long time to gain a recommended oxygen level. In all this cases the turbine aeration can improve the oxygen level. In this paper the range of possible improvement and calculation results are presented. The mass transfer is calculated with the model of volumetric mass transfer coefficients. Apparently this coefficient has a similar value for different plants, so that the mass transfer rate on other plants can be calculated out of simple parameters like the pressure below the runner and length and volume of the draught tube. The results of calculations and experiments show great improvement for oxygen deficits as well as for supersaturated conditions. An economical comparison of different reaeration devices at different plants indicated that the turbine aeration is the most economic method for most situations.
Year: 1999