Brewing beer with rainwater

Luc Vermeersch from the De Leite Brewery in Oostkamp, Belgium, brews beer like no other, but he would like to reduce his use of mains water. "How can I use one litre of mains water per litre of beer instead of four litres?" was the question he put to the Smart Services Bridge, the partnership that builds bridges between entrepreneurs and colleges in West Flanders and Zeeland. Researcher Mireille Martens and lector Niels Groot of the Water Technology lectorate, and Water Management student Johan Diepeveen, investigated the matter for him.

Eugène de Kok and Pieter-Bart Visscher, editors HZ Discovery

Brewer Luc Vermeersch has been working on making his company more sustainable for years. He wants to be ‘water neutral’ by 2030. "Issues relating to water soon lead to the HZ (University of Applied Sciences)," says researcher Mireille Martens. "And luckily also when it involves beer", she adds, laughing. Together with student Johan Diepeveen she has investigated how Vermeersch can reduce the amount of process water in the brewing process and whether he could use purified process water and rainwater. The majority of the water Vermeersch needs is for cleaning his tanks. Currently, it goes directly to the sewer after use.


To check the quality of the water used, Mireille and Johan took monthly samples from January 2021 onwards at different times during the brewing process. Johan analysed these in the lab in Vlissingen. He specifically looked at the concentration of metals, salts, nutrients and possible pathogens. "Because I carried out the sample analyses myself, I felt responsible for the research," he says of his assignment. "I was a small cog in the project. I was in a good position to answer questions from someone like lector Niels Groot about my readings.”

Membrane technology

Ultimately, Vermeersch would like to purify and reuse the process water itself. This is achievable after several stages. "First, you separate the large parts of the water, as the draff (malt residues and so on) settles. Then you filter out smaller particles and as for further treatment we are thinking of wetlands or membrane technology and a UV treatment, which kills bacteria," Mireille explains.

Degrees of contamination

It was difficult to take and compare samples because brewing only takes place a few days a month and the different types of beer contain varying proportions of ingredients, which in turn cause different degrees of pollution.

According to Mireille and Johan, Vermeersch can meet his target of one litre of water per litre of beer. "You can turn any wastewater into drinking water, but it comes at a cost. Vermeersch will have to make significant investments. The question is, to what extent economic preconditions will thwart his ideal of sustainability."

Using rainwater is easier than purifying process water. This is because rainwater is less polluted. After filtering and purification with UV light, it can be used as drinking water. However, aside from the fact that it has to be legally permitted, the brewer is required to build a large catchment basin to guarantee sufficient water. Given his production of about 10,000 litres of beer a month, a basin of at least 125 cubic metres is needed. "This also involves a substantial investment."


It was the first time that the Water Technology lectorate participated in an SSB project. Mireille is pleased with how it went. Especially with a student like Johan at our side. He stays focussed when he is in the lab. I find this an approachable work practice. Entrepreneurs outline their current situation and their objective and we guide them with our expertise. It is nice to work on real scenarios, particularly when you know that someone like Luc is going to do something with the solution provided. This is in line with the HZ's research and education philosophy.”

Earlier this year, Omroep Zeeland paid attention to the project. Read the article here.