Evides Industriewater has now been working in partnership with one of Europe’s largest chemical production sites for 20 years to introduce water conservation and circular economy concepts that will ensure a reliable water supply for the future despite the location in a water stressed region.
Dow Chemicals at Terneuzen is Dow’s second largest site globally and manufactures essential chemicals such as ethylene, propylene, butadiene, and benzene.
The drought in Europe in 2018 was a wake-up call for industry and water abstraction for cooling was restricted. Chemical companies are aware of just how important fresh water is to their operations but targeting growth means more water will be needed. In addition some routes to decarbonisation, such as biofuels, hydrogen and lithium batteries – will also increase water consumption. Lack of water has huge potential to derail the economy as well as efforts to combat climate change.
At Dow Terneuzen, 10 billion litres of water is used each year for cooling and steam production and since 2001, the production of the water for these processes was outsourced to Evides Industriewater with a long-term ambition to reduce the site’s reliance on the region’s freshwater resources, which are also required for public supply and agriculture.
Water reuse
The first step introduced at Dow was to analyse the wastewater streams from the site. Evides introduced new wastewater treatment that made it possible to reuse some water from wastewater flows, that were otherwise being discharged to the Sea. Other on-site water sources were then introduced: condensate from steam production was recovered and treated to be reused again and rainwater falling on the site was intercepted, cleaned, stored in large tanks and used to re-supply the site.
After all the on-site sources were maximised, a public-private partnership was set up between Evides and the municipality of Terneuzen. In this partnership Evides financed a new sewage treatment plant for the City’s urban wastewater. The MBR (membrane bio-reactor) designed, built and operated by Evides produces a much cleaner effluent than traditional wastewater treatments, which makes it possible to take the effluent and reuse it. Project developer at Evides Bas van Eijk explains, “We are treating 20% of the city’s sewage through our MBR and we have a dedicated pipeline to Dow 11km away to transfer the clean effluent. Once it reaches Dow, our treatment plant there produces demineralised water for Dow’s processes.”
Despite these innovations, Dow still requires 4–5 billion litres of freshwater every year from the Biesbosch – one of the last extensive freshwater tidal wetlands in Europe. Now Evides and Dow have committed to expand water reuse on site to reduce this reliance on freshwater to zero. The idea is to replace it with more treated wastewater from the city of Terneuzen, as well as more of its own effluent and rainwater.
Constructed wetland
The concept and potential of constructed wetland is illustrated by Colin “Whenever water is treated you get two flows, a clean flow and a reject flow. The efficiency of your water treatment is measured by the ratio of clean to reject flows. In order to achieve ours and Dow’s goal of 100% water supply from reuse, we need to improve the efficiency of our water treatment. The first step in this project has been to carry out a two year pilot of using a constructed wetland to pre-filter water before it enters our treatment plant.”
“The wetland does not use energy or chemicals and it actually supports biodiversity in the area. By passing the wastewater through the roots of the wetland, the plants soak up nutrients to benefit their growth. What the plant calls nutrients, we call pollutants and we would otherwise have to remove these mechanically or chemically to clean the water.
With the water pre-filtered by the Wetland, our treatment plant can achieve a much higher efficiency of water treatment, since less water needs to be rejected, more of it is recovered for reuse.”
Following successful deployment of water reuse at Dow Terneuzen, Evides now has a number of other pilot schemes in Europe to reuse industrial and municipal effluent as industrial process water. “These local, industrial reuse solutions are much easier to deploy than city wide water reuse projects, and they have a huge impact on preserving water resources. Every litre of reuse water supplied to industry is a litre preserved in a river or reservoir that can support biodiversity or protect drinking water resources.”
