Beitrag zur Verbesserung der Reinigung von Abwasserkanälen
In Germany the cleaning of sewers takes place predominantly with the high pressure cleaning (jetting). Since the beginnings of the jetting 50 years ago the machine and instrument technique of this procedure was improved significantly. On the other hand operating strategies changed hardly until today. Nowadays, jetting is still applied according to the so called system cleaning in most cases. Starting from the initial reaches and ending at the waste water treatment plant this procedure cleans sewer systems gradually in cycles of months or years. A contemporary and area-wide removal of deposits is not possible with that discontinuously and punctually practiced cleaning method.An appreciable reduction or prevention of shocks of pollution load on storm water overflow discharge and waste water treatment in combined sewer systems caused of deposit cannot be achieved, since a reformation of deposit is probable within a few days or weeks by using the conventional cleaning procedure. Also unsoiled reaches are cleaned because neither control of cleaning performance nor an assessment of demand for attend measures is carried through in advance. In addition increasingly damage to fittings and channel walls are deplored due to high compression stresses as well as due to inappropriate application. A proper cleaning of sewer systems cannot be attained therefore with the form of the jetting practiced today any more. On purpose of an effective water pollution control and for the improvement of the operational situation therefore the anyway high financial expenses for sewer cleaning are either to be increased and/or changes of the cleaning strategies and/or the choice of cleaning methods are necessary.In context of the available thesis it was therefore examined whether an improvement of the current situation can be achieved by sewer flushing which is common for a long time and was enhanced during the last years. Following extensive laboratory experiments, field studies and mathematical-numerical simulations were accomplished. The laboratory experiments showed that also small flushing waves cause a significant resuspension of settled particles and can therefore be used successfully in the framework of flushing measures. The results of the field studies clarify that flushing devices can cause both a basic and a preventive cleaning of sewers within certain boundary conditions. Varying hydraulic and structural boundary conditions cleaning performance of flushing waves was determined by one-dimensional flow models. The average bottom shear-stress served as criterion for the determination of flushing lengths. Basing on the results of these investigations a planning procedure for the flushing was developed. It permits a problem-specific planning of flushing measures for successful cleaning of sewers on a long term basis. The economic advantages of the flushing in relation to the jetting became apparent in context of a consideration of costs including the different cleaning qualities of the two methods.Today the flushing is an alternative for cleaning of sewers and sewer systems. Sewers can be kept in durably deposit-free, lasting improvements on water pollution control as well as on operation and maintenance of sewers and treatment plants can be obtained by a quasi-continuous application of flushing devices.
info:eu-repo/classification/ddc/620, Ingenieurwissenschaften, Abwasserableitung, Planungsverfahren, Bemessung, Kanalreinigung, großtechnische Untersuchungen, mathematisch-numersiche Untersuchungen, urban drainage, sewer cleaning, flushing, dimensioning, planning
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