De Rauwbraken, Netherlands

Located near Tilburg in the Netherlands, De Rauwbraken is a manmade recreational lake, which is popular among swimmers and divers. It was created in 1967 by sand excavation and has a total surface area of approximately 4 hectares.

The treatment was an initiative of the Aquatic Ecology Department of Wageningen University who proposed that the lake be treated by a combination of Phoslock and a flocculent due to persisting problems of cyanobacteria and high phosphorus (P) concentrations in the lake. The aim was to flocculate the algal biomass to the bottom of the lake using the flocculent and then use Phoslock to capture any orthophosphate in the water column as well as phosphorus released from decomposing algae and the sediment.  Eighteen tonnes of Phoslock and two tonnes of the flocculent solution were applied

The treatment of  "De Rauwbraken" had an immediate and sustained effect on the lake's appearance and ecological status.  Algae and other particles were rapidly removed from the water column, with the result that the lake was able to reopen for swimming soon after the application, while  phosphate and total phosphorus concentrations have remained at very low levels since the application.  This has prevented blue green algae from reappearing in large numbers, with the result that no blue green algal blooms have been recorded since the treatment. The diversity of fauna and flora in the lake are indicative of a healthy ecosystem.

Underwater video by F. Van Oosterhout


Underwater video by M. Schloesser


Algal bloom at Rauwbraken just before applicationApplication system used at RauwbrakenApplication of Phoslock at Rauwbraken on the first dayArrival of PACPAC (and buffer) being applied at Rauwbraken at day 2Application of Phoslock at Rauwbraken on day 3Blue glacier lake effect after the application of Phoslock on day 3