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Well chilled?

“The perch bite here a lot,” said Patrick Moser, angler and employee at Disruption Management (ESE/MW). “Here” is at the northern end of the BASF site premises on the Rhine, at the entrance to the harbor. At dusk, the Rhine embankment is a popular meeting spot for anglers as the fish promise a good haul.

But, why is that? Biologist Sascha Pawlowski (FEP/PA) explains: “There are several upstream inlets in the Rhine for our cooling water. The inlet feeds warmer water into the river – and the invertebrates and algae that are eaten by fish thrive in this warmth.” These areas are therefore ideal feeding grounds for fish. They do not mind that it is slightly warmer than in other areas of the river, as long as the supply of oxygen is sufficient.

 

Scientists call these areas “warm water plumes”: When cooling water is pumped back into the Rhine, it normally has a higher temperature than the river. The stream carries the cooling water along with the current, and if the temperature is measured, the cooling water is recognizable. After thoroughly mixing with the river water, the temperature difference is negated at around Mainz.

Upper temperature limit of 28°C for this river section

In general, the oxygen saturation of the Rhine is excellent over the course of a year – however, if the water temperature increases markedly, the oxygen content drops. Once the water reaches a certain temperature, the “air could get a bit thin” for some fish species. To protect the environment, lawmakers have defined an upper temperature limit of 28°C for this river section, which is based on the requirements of carps. During the summer months, BASF is therefore only allowed to feed cooling water with a maximum temperature of 33°C into the Rhine – as long as the 28°C upper limit has not yet been reached. This is a precautionary measure. Official investigations by the state of Rhineland-Palatinate have shown that there was no fish die-off in 2018 despite the extremely warm and long summer.

500

... types of invertebrate and 64 fish species can call the Rhine their home.

Last summer, water temperatures of 28°C were measured at Mainz leading SGD Süd (Struktur- und Genehmigungsdirektion; Structure and Approval Management) to request residents and businesses along the Rhine to reduce their thermal loads. This is a standard procedure at BASF: During summer, a large proportion of the cooling performance is provided by five main recooling plants. These systems compensate for the reduced cooling performance due to excessive water temperatures in the Rhine enabling the thermal load in the Rhine to sink to half the value recorded during winter. Nevertheless, there were still restrictions in production during 2018. The recooling plants were not able to fully compensate for the reduced cooling performance of the warm Rhine water. One large consumer of cooling water at BASF was totally removed from the production line while numerous production plants on site were forced to slightly scale back their production. “To prevent this scenario recurring this year, we are currently implementing various measures to increase the cooling capacities,” said Dr. Thomas Riede (ESI/E). “For example, we have installed more effective fluid distributors in the cooling cells of the main recooling plants, and have implemented measures to improve the air flow. Furthermore, we gain added cooling performance if specific plants pump their waste water into the main recooling plants at much higher temperatures than before: As a result of the waste water reaching the recooling plant with a higher temperature, the plants are able to deprive the waste water of more energy and to work more efficiently. We are working closely with the plants on this,” said Riede.

So, what’s next? Was last year just a one-off? Meteorologist Max Bangert (ESE/MU): “2018 really was an extraordinary year, it was extraordinarily dry and extraordinarily hot. Climate researchers forecast that the risk of these weather conditions to recur will increase over the next decades.”