Environmentally friendly removal of phosphorus-rich sediment from lake Öljaren and re-using it as a fertilizer in agriculture

Author: Jenny Herbertsson, the municipality of Katrineholm, 2022.

Full report in Swedish

Summary

Action C 12 is about environmentallyfriendly removal of phosphorus-rich
sediment from lake Öljaren and re-using it as a fertilizer in agriculture. The
sediments will be gathered up with a low flow dredging device and pumped up to
a gesosack for dewatering. The dewatered sediments will be spread on arable or
forest land as a fertilizer. The rejectwater flows back to Öljaren through a natural
ditch. Katrineholms Munipacility (KAT) is responsible for action C12.
Hjälmarens vattenvårdsförbund (HJVVF) are responsible for parts of the
monitoring in C12. C 12 is linked to action C 11 which are going to develop a tool
to identify lakes with internal loading. Some of the sediment samples is sent to
C11 for further analyzdes.

The method of dredging to be employed is considered to have minimal direct
negative environmental effects as the dredging device hovers over the lake floor
removing loose sediment through suction. In that way it is virtually no dispersion
of sediment particles into the water phase occurs. Many lakes in the district are
highly eutrophied and internal loading from the sediments play a significant part.
Action C12 will therefore serve as a case study to increase the knowledge,
experience and allow for the evaluation of the environmental effects of dredging.
The experience gained will be highly useful for possible future application of the
technology in other eutrophied lakes across Sweden. The action will also produce
knowledge and lessons learned concerning this rather new technique used. It will
also increase the knowledge about reusing sediments as fertilizers. Effective
recirculation of nutrients have the potential to reduce the need of artificial
inorganic fertilizers. Hopefully it leads to an increase in recreational value for
Lake Öljaren through improved water quality, wildlife, potential for fishing
swimming

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