Circular Rain

With Circular Rain we are investigating the innovative storage, purification and use of rainwater. By buffering and simultaneously purifying harvested rainwater, a variety of useful applications can be envisaged for the water.


EWB has developed an innovative filter based on washed seashells and a mineral mixture. The filter can be used to purify harvested rainwater. Laboratory research will determine the filter’s impact on the water quality.

A desk study has also been conducted to identify the substances present in the harvested rainwater, as well as their concentrations. This was followed by an investigation, for several projects, of the quality standards that the water must satisfy according to the current regulations, and what this implies for the requirements that need to be set for a purification method for harvested rainwater.


Column experiments have been carried out in KWR’s lab to determine the purification performance on the rainwater of the shells, of the mineral mix, and of the combination of the two systems. Based on these results, a measurement programme has been set up for the five pilots.


This project is being conducted through the following five pilots:

  • Goes (start 2015): sprinkling water for artificial-grass pitches at Sportpark ’t Schenge
  • Wijster (start 08-2019): extinguishing water at the Brandweer Oefencentrum Noord in Wijster
  • Amsterdam, Landtong Nieuw West (start 10-2020): recreational water at Waternet
  • Wetteren/Belgium (start 01-2021): recreational and irrigation water at Aquafin
  • Den Helder (start 03-2021): process water for Helderse Jongens brewery

Water quality measurements have been carried out 4 times on the input (rain)water and on the purified water. The pilot in Wetteren is being measured 8 times, and the difference between the quality of the water filtered by the shells and by the minerals is also being determined. The actual load of the system is also being measured in Wetteren by means of a flow-volume meter.

elasting van het systeem gemeten met een volumestroommeter.

Seashells used in the rainwater (Source: EWB)
Sprinkling buffer water for artificial-grass pitches at Sportpark ’t Schenge in Goes.