Contribution to the oxygen input in a treated sewage channel by falls

Summary: In the control of the discharge of a large-scale sewage treatment being under enlargement it was repeatedly pointed out that the oxygen saturation of the water in the treated sewage channel at the mouth of the main water occasionally was much lower than 50 %, contrary to the demands of the public inspection of waters. The results of the oxygen input capacity investigated by oxygen measurements on the falls of the 17.5 km stretch of flow indicate a total of 2.67 t/d. For lack of information on the diffusing and biogenic oxygen input an oriented balance about the budget of the water in the treated sewage channel was made. From the resulting oxygen depletion of the sediment of only 1.8 t/d as well as from energy-related considerations concerning the oxygen input by falls, technical alterations and arrangements for the protection and improvement of the water in the treated sewage channel were derived. By this it is guaranteed that the oxygen content of the treated channel-water at the mouth of the main water does not decrease below 6.0 mg/l also during the daily periods of higher discharges of treated sewage waters.