World first in the environmental field: purifying water using iron-sand


World first in the environmental field: purifying water using iron-sand

5 May 2020
In the heart of Grenspark Kalmthoutse Heide (the Netherlands) lies ‘De Groote Meer’ (The Large Mere’), one of our northern neighbours largest ponds. An iron-sand filter there will make water originating from agricultural plots, phosphate-free and purer, a unique process on such a large scale.

Sweco and Royal HaskoningDHV provided the preliminary study for the client ‘Natuurmonumenten’ (multi-criteria analysis, consideration of purification techniques) and the basic design of the phosphate filter. Contractor Harteman and Arcadis did the construction.

In order to maintain the water quality in De Groote Meer, it was decided to purify the water using a filter made of iron-sand. This innovative project is part of the European financing programme LIFE and the LIFE HELVEX project.

Valuable nature reserve
De Groote Meer is extremely attractive to special plants and animals such as littorella, strapwort and the black-necked grebe, which are not found elsewhere in Europe. The rare plants grow in a clean environment with nutrient-poor sand and clear water. The water quality however, has been deteriorating for many years. This is partly due to the supply of water from agricultural areas, mainly De Steertse Heide in Kalmthout. Fertiliser excess causes algae growth and an increase in species such as reed and bulrush. 

Special processing
The water is first diverted to a buffer basin, after which it gradually flows through the iron-sand. Iron-sand consists of sand with a layer of iron oxide and is a by-product of the production of drinking water. The phosphate in the surface water, which binds to the iron-sand in the treatment plant, causes algae growth to occur and makes the peat soil rich in nutrients. The remaining water passes through the filter, which purifies the water supply to the pond. As a result, De Groote Meer is fed with water of a much better quality than is currently the case.

Website Natuurmonumenten

Photos: Guy Geudens (Sweco)