Mud on the cheek
Lobbe desludges ponds in Bad Homburg
"We can't find a buyer for the sludge because it's too clean," says Udo Mai, project manager of the renaturation of two ponds in Bad Homburg. The site of the Werner Reimers Foundation is located directly behind the spa gardens and is a little gem of nature: at the foot of the gently sloping hill is a stream dammed up to form a smaller and a larger pond, surrounded by trees and inhabited by frogs and newts. The latter were taken out of the ponds by the environmental office of the city of Bad Homburg for the duration of the sludge removal and relocated for a short time.
The sludge, caused by leaves, soil ingress through rain and other natural influences, must be removed from the pond so that it can continue to function as a natural biotope. Lobbe took on this task, which had already been rejected by other suppliers. After all, the sludge in the pond is 1.20 metres high. "Not every company in the disposal and remediation sector has the corresponding know-how," Udo Mai knows.
But the excavated sludge, completely free of any pollutants, must - as the law prescribes - be "disposed of professionally". The natural soil, which would be suitable for horticulture or agriculture, is not suitable for the specialised disposal companies and their treatment plants, because the pollutants are missing. Now the soil is to be landfilled after a drying phase.
It is no coincidence that the experienced Lobbe team is carrying out this desludging. The detailed implementation requires a great deal of experience and know-how. Lobbe spent three days using submersible pumps - each pumping 500 litres of water per minute - to empty the ponds and transport the water into the stream. To remove the excess sludge from the pond, Lobbe resorted to a special excavator. "The sludge is first stored on the higher ground and then filtered through big bags with a membrane," explains Udo Mai. These big bags with built-in membrane filters are usually called filter bags. The membrane is permeable to water, so that only the solid components such as soil and suspended particles remain, and the water flows off into the stream according to the natural landscape gradient of the pond system. After one week with three employees and two excavators, about 350 cubic metres of sludge have been removed from the pond.
After Lobbe has treated the pond, landscapers and gardeners will rework the pond banks and embankments before frogs and newts can move back into their renovated home.
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