Koholmens Wastewater Treatment Plant is designed for 57,000 inhabitants and is the heart of Karlskrona system for the resort's sewage management. To this place is headed wastewater from Karlskrona urban areas, from the neighboring islands, as well as from the sewage treatment plant at Sanda Island and from the population at Sturkö Island.
The purification process creates opportunities for a closed loop between a city and the countryside. Koholmens Wastwater Treatment Plant is designed for 57,000 inhabitants and is the heart of Karlskrona system for the resort's sewage management. To this place is headed wastewater from Karlskrona urban areas, from the neighboring islands, as well as from the sewage treatment plant at Sanda Island and from the population at Sturkö Island. The line between Sturkö and Koholmen is placed on the seabed and it is 6 km long. The outlet line includes over 4 km and ends at 20 meters depth in deep drains from the Karlskrona archipelago, south of Verkö. Together, they form the backbone of Europe's largest lake-line system. The lines are like a spider web from Koholmen and out to Karlskronas islands. The facility includes mechanical, biological and chemical treatments. Solid contaminants are separated in the mechanical part in the process with screens and grit chambers . In the biological pools the organic material breaks down by microorganisms , mainly bacteria that enter through the wastewater. The microorganisms grow , take up phosphorus and release nitrogen and form a sludge separated in the sedimentation . The majority of the sludge is returned to the bio pools , while the surplus ( the growth ) is taken out of the process and checked and analyzed. The sludge is an excellent fertilizer of very good quality - but is still used as the final cover of the municipality's old landfills . The reason for the major expansion of Koholmen Plant in 1995 was new regulationens for nitrogen removal. The old plant was at Sunna Channel , which at this time was a rather smelly waterway . The project was awarded by the County Council Architectural Award 1995.
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