Innovation

Startup electrifies the water supply

A duo from DTU aims to make India’s water supply safer. They are behind an invention that purifies water directly in rooftop collection tanks using just a small amount of electricity.

The water supply is unreliable in large parts of India. Consequently, houses typically have their own tanks – often on the roof – which are filled with water when it is available. The water is stored here until needed. Photo: Njord aqua

Tuesday 07 July 2026

Miriam Meister

Danes are used to clean water flowing steadily when we turn on our taps. In stark contrast, a huge proportion of the population in the world’s most populous country, India, gets their water from rooftop collection tanks. These are vulnerable to contamination from disease-causing microorganisms, and the water therefore requires purification before it is safe to use.

Njord aqua, a DTU start-up, has set out to ensure people have access to potable water from such tanks with their product, which uses electricity to convert naturally occurring salt in the tank water into chlorine. This makes the water suitable for drinking, cooking and washing.

A vital resource

“When you see these water installations, you sometimes can’t believe your own eyes, because they’re at optimal temperatures for microbial growth, and some of them are partially uncovered or have holes in them. One of our test users even told us that he had problems with monkeys opening the tank and swimming around in it,” says co-founder Andreas Sixten Hallstein Rygaard.

On a reconnaissance trip to India with his business partner Viktor Ryle Tamstorf, he witnessed first-hand the challenges with the water supply there.

The latter is behind the award-winning idea, which was conceived during his bachelor’s project and in 2023 was named the best bachelor’s project at DTU’s student conference for green projects, Grøn Dyst. He continued working on the idea as part of his master’s degree.

“There is a massive need for solutions like this in countries such as India on a scale that is simply impossible to comprehend. Water is, after all, a vital resource that we simply take for granted here in Denmark because we have access to groundwater,” he says.

Promising laboratory data

Installing the Njord aqua system does not require a specialist, and once it is set up, it can run for years without any interference—unlike if people were to try their hand at purifying the water in their tanks with chlorine.

“Chlorine in bottles or tablets degrades over time and therefore has an expiry date. It is also difficult to dose, and it has to be transported to where it is needed,” explains Viktor Ryle Tamstorf, continuing:

“With our invention, chlorine is produced directly in the water right where it is needed. The purification unit continuously purifies the water in the tanks, so the chlorine level in the water remains stable over time.”

Laboratory tests show that NJORD aqua’s invention can reduce the bacterial contamination in tank water just as effectively as reverse osmosis systems, which are currently the most widespread purification method in India (see fact box). Furthermore, their device requires no more electricity than a solar cell the size of an A4 sheet can generate.

“This way, you are not dependent on a supply chain of consumables such as filters or a power socket, which means our system can also be used in remote locations,” explains Andreas Sixten Hallstein Rygaard.

Facts

About water purification

The most used method for purifying water in domestic tanks in India is a combined water purifier that uses reverse osmosis—a system comprising e.g. a pump, UV lamps and filters that must be inspected and replaced regularly. This constitutes an ongoing expense. According to Njord aqua, such systems typically take an hour to purify 10 litres of water.

Njord aqua’s system consists of a unit installed on the tank which passes an electric current through the water. This converts the water’s natural salt content into chlorine, which purifies the water. A sensor outside the tank monitors and controls the process.

Once the system is up and running, it is expected to be able to purify up to 5,000 litres of water within an hour of the daily refill without requiring ongoing maintenance. Users can verify the water’s purity using a test strip that is dipped into the water revealing the result.

Water purification using chlorine has been widely used worldwide for the past 100 years and is therefore a well-established technique, with a formula specifying the concentration of chlorine required to keep disease-causing bacteria at bay. 

Two men doing fieldwork by some water tanks on a rooftop in India. Photo: Njord Aqua
Viktor Ryle Tamstorf (left) and Andreas Sixten Hallstein Rygaard have gained first-hand insight into the challenges related to the water supply in India during a reconnaissance trip there. During the trip, they carried out fieldwork to, among other things, test the water quality in the tanks. Photo: Njord aqua

A long-standing partnership

While the company is brand new, the partnership between the duo behind it dates back to their first day of school at Toftevangskolen in Birkerød a good 20 years ago. Since then the good friends have been, among other things, scout leaders, climbing partners, secondary school classmates and DTU students together.

“It was always on the cards that we would try to start a business. Even back in primary school, we had a little shop where we sold various snacks to the children who weren’t yet allowed to leave the school grounds during break times,” says Andreas Sixten Hallstein Rygaard.

He adds with a laugh that the “shop” ended up being shut down by the headteacher, who nevertheless gave the boys credit for the business idea.

Throughout the process of developing the NJORD aqua product, the co-founders, who both hold master’s degrees from DTU, have had access to the university’s laboratory facilities and expert guidance from water purification specialists with insight into India.

They have also benefited from DTU’s innovation ecosystem through, among other things, funding and a stay at the DTU Skylab innovation hub.

They believe it is of great significance to have emerged from and be based at DTU.

“There is a sense of legitimacy among Danish investors in coming from DTU, as they then trust that the technology is sound,” says Andreas Sixten Hallstein Rygaard.

Over the coming year, the duo will be working full-time on the start-up from their space at DTU Skylab, thanks to a grant from Innofounder, which will cover their salaries for a year. The focus is on further developing the system so that, by the end of the year, they can conduct a pilot study involving many units at once to validate the technology and then raise the funds to bring the product to market.