Reducing energy costs and protecting against backflow

Karlshamns Municipality
Karlshamn, Sweden
Area of use 
Flood protection

Severe flooding occurred during periods of high water levels caused by storm events.  Flooding affected not only homes in the sea front area, but also caused inundation into the sanitary sewer leading to an overloading of the treatment plant. The existing pipe was DN1600mm (NPS 42").  It was important to have a low opening pressure in this area given that it is very flat with no fall in the stormwater pipes.


A single installation was undertaken with one large WaStop to allow the high flows through the valve, and three small valves to ensure low flows could be released.  All four valves withstand 5m (16') back pressure.

Stopping the flooding was essential, but the other positive effect of the installation was that flow to the treatment plant decreased by 100 000m3 per year.  Thereby reducing the cost of electricity for pumping and treating by €12 000 per year.

In order to handle large amounts of rain a small pump was installed to lift the water from a surface water chamber, situated just in front of the WaStop. The pump releases the water in an old unused sewer line which runs parallel to the current storm water pipeline.  This means that when the sea level is high and it is raining heavily, the water can still be evacuated from the system.  

Residents in the area have not suffered from flooding since installation and the treatment plant no longer needs to treat sea water, saving money for the Municipality and also saving the environment. By reducing the amount of seawater flow into the treatment plant it also eliminated the risk for overloading, and the subsequent dumping, from the treatment plant. This reduces the impact on the environment, and also reduces the fines levied to the Municipality by the Environment Protection Agency.  It is a win-win project.

For more information about this installation please contact Wapro.


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