De Kuil, Netherlands

Zwemplas De Kuil at Prinsenbeek is a former sand excavation pit which is currently used for recreation by swimmers and anglers. The lake has an area of approximately 7 ha and an average depth around 4 m. The lake has a history of blue green algae blooms and was treated as part of a Dutch Government study project undertaken under the auspices of the EU "Water Framework Directive Innovation Program".

The Project was an initiative of three Dutch Water Boards (Brabantse Delta, Dommel and Aa en Maas) with scientific input from the Aquatic Ecology Department of Wageningen University. The treatment took place in the middle of May 2009 and consisted of an application of 41.5 tonnes of Phoslock (the majority of which was injected directly to the hypolimnion), preceded by an application of ferric chloride to flocculate algae and other particulate matter.  This method has been termed "Flock and Lock" in the Netherlands.

The effect on visibility and phosphorus concentrations as a result of the treatment was detected relatively quickly and significantly reduced concentrations of blue green algae have been measured since the application.  Full details of the treatment are contained in the downloadable report.

De Kuil just before the application (02/05/09)Application of ferric chloride at De KuilFlocs being formed after addition of flocculant at De KuilPhoslock application at De KuilClear water at de Kuil after the treatment at 22/05/2009