De Kuil, Netherlands 

De Kuil was treated with 41.5 tonnes of Phoslock in May 2009 and on a second occasion with 32.5 tonnes in May 2017. Both applications were part of a “Flock and Lock” treatment, involving the additional use of flocculants, applied prior to a Phoslock treatment.   

Zwemplas De Kuil at Prinsenbeek is a former sand excavation pit used for recreation by swimmers and anglers. The lake is approximately 7 hectares and has an average depth around 4 m. The lake has a history of poor water quality and was first treated with Phoslock as part of a Dutch Government study project undertaken under the auspices of the European Union Water Framework Directive. 

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.

The effect on visibility and phosphorus concentrations because of the treatment was detected quickly. A subsequent Flock and Lock treatment was undertaken in May 2017.