Wastewater treament plants

The long-term goal is to prevent amphibians from getting into the pumping stations, rainwater retention basins or wastewater treatment plants or to reduce the number of amphibians that get there as much as possible. On the way to the wastewater treatment plant, the amphibians lose energy and may end up far from their habitat. In addition, not all wastewater treatment plant operators are equally open to innovations or to amphibian protection measures. Whenever possible, the amphibians should be able to get out on their own directly at or in the immediate proximity of where they entered.

Amphibian capture device at the wastewater screening

The amphibian capture device shown here (cf. Figures 1 – 10) is located immediately after the multi-rake bar screen
and in front of the rake press. Basically, every wastewater treatment plant has a multi-rake bar screen. Unfortunately, some of these screens are constructed completely differently and so there is no uniform solution. In certain systems the multi-rake bar screens are completely open and in others they are completely closed. If the screen has a completely open design without a cover grill, frogs will occasionally jump out. However, open structures often have a cover grill that makes it impossible or difficult for the frogs to jump out (cf. Figure 11). If the multi-rake bar screens are designed to be closed, employees are more likely to reject such an amphibian exit system because of the fear that the stench in the room could increase.

Incidentally, the rake distance is not the same in every wastewater treatment plant or for every rake. Experience has shown that from a rake distance (bar spacing) of 15 mm, the amphibians increasingly move on to the next system, a sand trap system with a grease separator. With a rake distance of 10 mm, however, the rake is the final stop for the amphibians.

Figure 1: Amphibian capture device immediately in front of the rake (grill)

Figure 2: The water flows through the rake. Most solid material is trapped this way. The smaller amphibians are less likely to survive the long journey and the larger amphibians usually cannot get through the rakes.

Figure 3: The rake (grill) press is deadly for amphibians.

Figure 4: You would no longer be able to recognize a frog in the pressed material.

Figure 5: The amphibian escape device is located immediately in front of the rake.

Figure 6: Once safe, the amphibians can no longer go back.

Figure 7: After a certain time, the basin empties and all the solid contents enter the press.

Figure 8: This alpine newt is lucky to have reached and used the amphibian escape device in time.

Figure 9: The two common toads were lucky to have reached and used the amphibian escape device in time. With this instrument, 300-500 amphibians are saved every year in this wastewater treatment plant alone.

Figure 10: Releasing the animals is an additional effort that makes it more difficult to install the amphibian escape devices in the wastewater treatment plants.

Figure 11: A grid in front of the rake makes it difficult for frogs to jump out. An amphibian escape device is still missing from this other facility.

Amphibian collector device in the aerated sand trap system with a grease separator.

Because the rake distance is too large, the amphibians in this wastewater treatment plant reach the sand trap with a grease separator. An amphibian collector device is now used there (cf. Figures 12 – 15). The amphibians that get into the collector device can no longer get out and can therefore be saved. Such an amphibian collector device could also be used in rain retention basins and other systems.

Figure 12: The perforated plate and a collecting bucket form the basic structure of the amphibian collector device.
© Christoph Noger

Figure 13: The lid prevents too much rainwater from entering and tempts the amphibians to crawl under it.
© Christoph Noger

Figure 14: When lifted, the lid goes up and the collecting bucket can be easily removed.
© Christoph Noger

Figure 15: The amphibian collector devices can be lifted out of this sand trap with grease separator system using a hand crank.
© Christoph Noger

Amphibians in the rain retention basins

Attached below is a photo album that mainly shows pictures of rescue operations from rainwater retention basins. The rain retention basins shown here are located directly next to the wastewater treatment plant. As a rule, there are also rainwater retention basins elsewhere in the community and not just at the wastewater treatment plant itself. Entering the rain retention basins may only be done with a gas warning device and the permission of the operator.