Towards a water-wise world Annual report 2014

Risk of algal blooming in infiltration pools is limiting factor 

Dunea can sometimes switch over from Meuse to Lek water for short periods

21 April 2014BTO

Thanks to a KWR scenario study, Dunea knows that the possibility is open – from March up until and including July – to switch over for a short period to Lek river water, without seriously raising the risk of algal blooms in the Meijendel infiltration pools. The Lek’s water quality is less rapidly affected by climate change than that of the Meuse, which is the normal source of Dunea’s water intake. The temporary switch to Lek water can therefore help the water company adapt to climate change.

From research to policy in the event of calamities

Dunea uses the Afgedamde (Dammed-Up) Meuse as the source for the water it infiltrates in the dunes. This is how the company produces excellent drinking water. Disasters or climate change might however seriously degrade the quality of the Meuse water in the future. To prepare itself for such eventualities, Dunea wants to know whether, in the event the water quality of the Meuse becomes poor, it can, without any negative consequences, switch to the Lek for its water intake. The Lek is connected to the
Rhine and therefore less dependent on rainwater than the Meuse. This also means that it is less susceptible to climate change. Research into the concentrations of pesticides and pharmaceuticals in both rivers demonstrates that the switch to the Lek water has little impact in terms of the risks presented by these substances.

A Dunea infiltration pool in the South Holland dunes

A Dunea infiltration pool in the South Holland dunes

Phosphorus content determines possibilities

Ton Knol, a treatment technology consultant at Dunea, explains: “In 2013, together with KWR, within the water sector’s joint research programme (BTO) Tailored Research theme, we studied whether it would be better during intake stops to let the infiltration areas – particularly the fragile wet dune valleys – temporarily dry up, or to switch to another water source. Because the latter option appeared the best, in 2014, we have researched in a scenario study whether a switch to the emergency Lek water intake would have any detrimental effects on the water quality in the Meijendel infiltration pools. Since the intake process of Lek water does not normally involve phosphorus removal, it is not always possible to switch to this river’s water: more phosphorus can cause algal blooms in the infiltration pools. However, between March and July (inclusive) this problem is limited as long, that is, that water is abstracted from the Lek for 1 week at the most. Switching over for a period of 2 weeks is only a possible option during the month of April, otherwise there exists an algal bloom risk. Any long-term abstraction of Lek water would require pre-treating the water through flocculation in the rapid filters at Bergambacht. We are currently incorporating the results of this tailored research into the update of our intake policy.”

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