„Adaptation to Climate Change at the Local Level“

In our daily lives, we use water for cooking, washing dishes, and going to the toilet. In factories, we also use water to clean products and even to produce products. So how should the wastewater generated be treated? On March 21, we came to the sewage treatment plant in Bissendorf.
I originally thought that the location of the sewage treatment plant would be chosen in a relatively low-lying location due to the cost of transporting sewage, but I didn't expect that the choice of location needs to consider many other factors, such as historical reasons and policy factors. In addition, the speed of collecting and treating sewage in this sewage treatment plant has reached a delicate balance. Bissendorf collects about 5,000 cubic metres of sewage every day, and the maximum capacity of the sewage treatment plant is about 10,000 cubic metres. It takes about 1.5 to 2 days to treat sewage, so there will not be too much sewage stored here.

The sewage treatment steps are roughly as follows:

1. Mechanical treatment: Through physical methods, solid components are removed from the sewage in a bar screen and a settling basin. The sewage is also cleaned from fats, oils, and greases in a grease separator before it is transported to biological treatment pools. The sludge is dewatered to 70 to 80% dryness through a press and transported to a garbage incineration.
2. Biological treatment: There are three pools, and each group of three pools is called a set. Each pool is a different bacterial treatment method. The first phase is denitrification by anaerobic bacteria, which use nitrogen to treat certain other substances in the sewage, the second phase is nitrification by aerobic bacteria, which use organic carbon dioxide in the sewage and added oxygen to transform ammonia into nitrate. Sedimentation will also occur. So the sewage in the second pool will be relatively cleaner than the sewage in the first pool, and the third pool will be relatively cleaner than the second pool. At present, two sets of biochemical pools are being built, which were not fully completed when we went there.
3. Sedimentation treatment: The sewage will finally enter a large pool. There will still be some static effects, and the solid components in the sewage will settle again and be separated from the sewage, and then the sewage at this time has basically reached the discharge standard.
4. Membrane filtration system: The managing director of the plant also told us about their further construction plans. In the future, they may build a membrane filtration system to make the treated water purer.

Their sediments are also properly treated. Four times a year, samples of sediments are sent to the laboratory to test whether heavy metals exceed the standard. If they are within the permitted range, they can be transported to the farm for cultivation. If they are not in compliance, they can be directly burned for treatment.

After that, the managing director of the sewage treatment plant also introduced us to their advanced energy supply system. They built solar panels above the plant for power generation. In addition to solar panels, they also have a dedicated biogas digester for energy supply.
Afterwards, we went to the Bürgerhaus Wedemark in Bissendorf, where we learned about the entire energy conversion process of Wedemark. An ecological park for water storage was built here to reduce the impact of climate change. With the support of policies and funds, many families choose to install solar panels on their roofs. On sunny days with wind, additional wind farms and solar parks contribute a lot to the energy supply in the municipality. A projected very large wind farm will produce enough energy for the whole Wedemark and additional municipalities. However, the unstable climate makes solar energy and wind energy uncontrollable. Energy storage is also a problem at present, and the difficulty of changing the personal wishes of residents is also an obstacle to energy conversion and carbon neutrality. However, everything is moving in a good direction. Wedemark strives to achieve carbon neutrality by 2035. Without taking the emissions of a federal motorway running through the Wedemark area into account, on which the municipality has no influence, there is even the ambitious goal to reach carbon neutrality by 2030.

We still had time, so we went to the local museum, Kavalierhaus Bissendorf, where we saw how people lived hundreds of years ago. We saw how rich people used the toilet 150 years ago (I had a similar experience when I was a child) and how to keep warm when giving birth. Moreover, the structure of the house was very interesting. The houses were all made of wood and infill, and the appearance of each house was very similar. There were also safety measures 400 years ago. Because the houses were all made of wood, they basically had two doors. They had a cellar for storing vegetables in winter, which contained 100 years of pickled vegetables. Although the tour guide said that we could try it if we were hungry, we still refused, hahahaha.
The whole trip was really fun, we learned a lot and it was entertaining.

Yue Pu