On 11th and 12th June, around 20 students from Leibniz University took advantage of the opportunity to visit exciting sites in the field of municipal water and waste management, organized and accompanied by the ISAH. The first stop was Drewsen Spezialpapiere GmbH & Co KG, in Lachendorf (see DREWSEN SPEZIALPAPIERE), which provided a guided tour through the individual production stages and the in-house sewage treatment plant. Paper production is a very water-intensive process that, despite a water reuse rate of 90 %, requires the addition of freshwater of about 6000 m³ per day. The wastewater produced during production is treated in a partial stream in a specially designed Moving Bed Bioreactor (MBBR) with an agitator, which uses less energy than conventional MBBRs with aeration systems. All wastewater is then treated in a biofilter.
In the afternoon, the visit to the VW factory in Wolfsburg took place (see Volkswagen). The VW plant uses groundwater, surface water, and rainwater for drinking water supply and production. Wastewater treatment takes place at the plant in three different wastewater centers. The first two are used exclusively for mechanical purification, while the last wastewater center is used for biological purification in an aeration tank with surface aeration. The effluent from the sewage treatment plant is temporarily stored in a retention basin, part of which is discharged into the Aller river, and the remaining part is reused, for example, as cooling water or flushing water for toilets. (See also Environmental Statement of the Wolfsburg site (Dokument).
On the second day of the excursion, the Seehausen wastewater treatment plant of hanseWasser GmbH in Bremen was visited (see hanseWasser and Kläranlagen). A total of 50 million m³ of wastewater per year is treated here in what is, in size and whole, a typical municipal wastewater treatment plant. However, a special feature of the WWTP is that it has been climate-neutral since 2015. For this purpose, the CO2 emissions of the aeration tank are collected; and biogas from sludge stabilization, and renewable energies such as wind and solar energy, are used for the energy supply. The Seehausen sewage treatment plant produces more energy than it consumes. In addition to wastewater treatment, hanseWasser is also responsible for rainwater management in Bremen. Here, they have the means to actively divert the rainwater into various collection systems in the city of Bremen and thus prevent flooding.
The last station of the excursion was the residual waste treatment plant (RABA) of AbfallWirtschafts-Gesellschaft (AWG) mbH, in Bassum (see RABA Bassum). To treat the residual waste, it is first divided into three fractions (> 6 cm, 4-6 cm, < 4 cm), and iron and other metals are removed. The fraction < 4 cm is fermented and then composted together with the > 6 cm fraction. The 4-6 cm fraction is composted together with the biowaste, thus obtaining high-quality plant substrate for use in agriculture and gardens. In total, 80% of the residual waste is converted into Refuse Derived Fuel (RDF).
Acknowledgment
We would like to thank Drewsen Spezialpapiere GmbH & Co KG, the VW mill, hanseWasser, and AWG, as well as their employees, for the interesting insights into practice and the different methods of wastewater and waste treatment. We would also like to thank the Oswald Schulze Foundation, which provided financial support for this instructive excursion.
