Wetlands - Nature as a water filter
The central question during the evaluation of the cooperation contract between Dow Benelux and Evides Industriewater was: 'how can we make water use more sustainable in an innovative way?' The answer to this question, both parties believe, lies, among other things, in nature. In the pilot project that started last year, wetlands - which are swampy areas rich in natural vegetation - are used as a natural water filter. This purifies wastewater from the local industrial and domestic wastewater treatment plants and provides proper pretreatment for a downstream desalination step. Studies on this should reveal in 2021 whether it works or not.
Two 350 m² wetlands have been created on the site of Evides Industriewater, on the border of the industrial park where Dow has several plants. The plant roots and microbes in the soil must ensure the biological stabilization of brackish wastewater before it is desalinated. The quality of the water is closely monitored via a newly built research location near these two test wetlands and the impact on further purification into demineralized water (mineral and salt-free water) is investigated. A special feature of this application is that additional functionality has been added to these natural systems through additional aeration, among other things.
Cooperation with local farmers
At the same time, in the Braakman-Zuid area, in cooperation with local farmers, we are investigating the possibility of storing rainwater and polder water underground. In this way, reserves can be made available during droughts. This is an aspect that, certainly with the increasingly dry summers, can contribute to reducing the need to use water that is also suitable as a source of drinking water. Both projects receive financial support from the Deltafonds [Delta fund] and the EU Interreg Twee Zeeën [Two Seas] program respectively.
Working towards results
If the pilot is successful, it can be expanded to 6 to 8 hectares of wetlands. The result: a lot more (re)use of treated wastewater and a lot less use of Biesbosch water. And that is important, because Biesbosch water is an important source for the production of drinking water. In addition, the quality of the cooling water will be improved to such an extent that Dow will need less water and chemicals in the cooling towers.