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Excursion part 2 - Urban drainage

Follow-up steps of the sewage treatment process

Once again, the apprentice-sustainability team of SCHWARZ, under the leadership of Uwe Schwarz, visited the city drainage of Rottweil. After the sewer network and wastewater treatment of the city of Rottweil were explained during the first visit in the summer of 2022, this time the focus was on the subsequent steps of the treatment process.

From liquid to solid - this is more or less the process of sewage sludge treatment. After the wastewater has already passed through various purification stages, the remaining sewage sludge, which essentially consists of dead bacteria and water, is passed through several filters and draining stations. In the so-called clarification tower, high-energy gases are produced, which are then passed on to the neighboring combined heat and power plant.

The electrical energy and waste heat generated in this process are used 100% for the processes of the sewage treatment plant.
At the end, the sewage sludge has a residual moisture content of 30% and is then dried. The end product has a very high carbon content and finds its final use in energy-intensive production processes, such as cement production.

The SCHWARZ trainees were both amazed and enthusiastic about the technical effort with which our wastewater is treated and at the same time a closed cycle is pursued. A big thank you goes to Mr. Haak and his team of the city drainage, who again gave us deep insights into their work and sharpened our awareness in dealing with our resources.