Rheological study and valorization of waste sludge from wastewater treatment plants in the dredging operation of hydraulic dams

The wastewater resulting from various urban activities cannot be directly released back to natural environment because they contain various pollutants, including organics and minerals causing potential various types of diseases. Instead, wastewater must be purified prior to its release, which leads the production of waste sludge. A large quantity is produced from a wastewater in the purifications plants. An activated treatment of sewage wastewater also results in the generation of a considerable amount of excess sludge. This sludge must be disposed of safely. Commonly used disposal practices comprise of incineration, landfilling and application. The cost for sludge treatment is highly dependent on the volume and water content of the produced waste sludge. Treatment and disposal of an excess sludge in a biological wastewater treatment system requires a very high cost which accounts for approximately 35–60% of the whole operation cost of a wastewater treatment. In this study we propose a technique less expensive and more convenient. This technique is based on the use of sludge to reduce the loads losses during the dredging operation of hydraulic dams. The rheological study of mixtures of mud of dam and sludge from purifications plants showed a reduction of the yield stress of mud of dam up to 95%. Therefore the use of sludge from purifications plants during the dredging operation of dams facilitates the transport of sludge of dam.