Municipal: Trysil, Norway


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Project Name:
Innbygda WWTP

Trysil, Norway

Type of Plant:

Technology Used:
CFAS® + DAF Separation (chemical precipitation of P)

Operational Since:
November 2010


The Challenge

The municipality of Trysil is home to the largest ski resort in Scandanavia. Due to seasonal tourism in the region, the treatment plant must handle fluctuations in load depending on the number of tourists visiting at any given time. In addition, the plant had to have the ability to withstand extremely cold temperatures during the winter months. The existing wastewater treatment system was at the end of it’s useful life.


The Design

Many factors affected the design. As mentioned, the cold temperatures and load fluctuations as well as the customer’s desire for a compact, highly efficient technology. Biowater was in competition with conventional MBBR technology combined with a separation unit. In the end, Biowater CFAS® (IFAS) Combined Fixed-film Activated Sludge process was chosen because of it’s small footprint and reliability.



By choosing the Biowater CFAS® biological process combined with DAF separation the client was able to build the plant as compact as they had planned and still achieve the effluent quaility that they were aiming for. Due to the use of DAF separation, the plant could be built without a gravity thickener unit which was in the original design. The plant is so flexible that in the off season only one Biowater CFAS® reactor is needed and the other is shut down to save energy.

Trysil St

The Biowater CFAS® (IFAS) process utilizes the benefits of a traditional activated sludge process combined with a biological fixed-film system to create a highly efficient wastewater treatment plant in a much smaller footprint.