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Down by Nørreå stream
The overflow from a sewer system into a watercourse should contain as few substances as possible. This also applies to Nørreå stream in Randers.
Randers Municipality and Mosbaek collaborated on the construction of a system to meet the specific needs of the municipality:
- In addition to a small underground structure, there is a large inlet pipeline. This ensures a slow flow-velocity and is also where separation occurs.Heavy substances sink to the bottom and light substances float to the top. Both parts are diverted to the waste water treatment plant.
- In the structure, the water is diverted to a waste water treatment plant and, when it overflows, into the stream. A Mosbaek flow regulator on the pipeline leading to the waste water treatment plant controls the discharge during filling and emptying of the separator. It ensures that the diversion to the stream and the load on the waste water treatment plant are ideal in rainy weather.
- The flow regulator also ensures that the inlet pipeline is kept clean. This is explained by the regulator’s unique characteristic which has a high flow-velocity at both the beginning and end of the flow-through.
- The sieve does not trap very many substances because sedimentation upstream a dividing plate and a floating skimmer send as many substances as possible to the waste water treatment plant.
- This is confirmed by the experiences of the operating staff. The system works exactly as planned.
There is access to the system via a superstructure.
The structure is below the grate in the picture. This is where the large pipeline flows in.
An angled dividing plate, a sieve and a floating skimmer are installed inside the shaft.
The dividing plate separates the water flow and ensures the discharge of substances at bottom and top. The skimmer retains the floating substances and diverts them via a culvert to the waste water treatment plant.
The shaft inside the structure functions as an overflow. All overflowing water flows through the sieve. The sieve is hinged and balanced, so it opens by itself under heavy loads.