Water

A meters-high milk cooling tank at the University of Twente does not store milk, but water. The tank, which has been in operation since 2023, is intended to lend a hand during heavy rainfall.    

The rain barrel has a capacity of 35,000 liters and serves as a "buffer" for the sewer system in Enschede and the surrounding area. "Once in a while you have to deal with heavy rainfall, which leads to a lot of water on the streets because the sewer system cannot handle the water," said Richard Bults, creator of the smart rain barrel. The idea is to put together a network of smart rain barrels to create a buffer capacity in Enschede and surrounding municipalities.  

However, the smart rain barrel does more than just collect water. Based on the weather forecast, this rain barrel can empty itself, so as not to overload the sewer system. The water can also be refreshed, and the stored water can be used to water surrounding vegetation and sports fields. 

We have installed a water buffer and infiltration system with a hollow space under the car park of De Boerderij building (formerly the Faculty Club): AquaBASE. This water storage system was one of the first of its type in the Netherlands. The system consists of permeable stones interspaced with small joints to guarantee a good flow rate and infiltration capacity. The substrates feature hollow spaces, in which water is stored and have sufficient load-bearing capacity and stability to be used in car parks. This system retains water for longer, so that it infiltrates into the soil more slowly. For more technical information, visit the website of AquaBASE (Dutch only).

Underneath P2 is a thick layer of gravel which lets the soil retain more water, so that it can infiltrate deeper into the soil at a lower pace.

The cold circulation system of the UT consists of a large basin measuring 10 metres deep and 36 metres wide that holds 10 million litres of cold water, which is used during the day to cool the connected buildings and research equipment. The chillers mainly cool the water at night, because the water temperature is naturally colder then, which saves a lot of energy. On top of that, it also saves costs, because the night rate for energy is lower than the day rate. The cool nighttime climate and air-cooled chillers join forces to cool the water down to approximately 8 to 10 degrees Celsius. For more information, visit the page on ‘Energy’.

On the Hogekampplein, there there is a water purification lab that is used for research from UT's membrane cluster, as well as filtering rainwater. Water is filtered to drinking water quality (although it cannot be used for that purpose as it would need certifications). The filtered water is then stored in the 'reinwaterkelder', or water storage cellar, under the athletics track. It can be used for irrigation of the nearby sports fields. Even artificial pitches need to be watered quite frequently to keep them usable. Using rainwater for this is ideal, as we want to stop using tap water for that purpose. The rainwater needs to be filtered before it can be used, as rainwater has impurities causing algae growth. By filtering this pond water, around 1500-1600m3 of drinking water has been saved. Further insight can be gained by checking out the Energy Data Platform. 

Watch this informative video on the topic (in Dutch):

At Langezijds, infiltration crates of 25m3 per garden store rainwater. This is used for drip irrigation. There is surplus storage, from which plants can be watered that are present elsewhere in the building.

A retention pond is a pond which collects the overflow of the Roombeek and lets the water slowly infiltrate to replenish the groundwater table. This water can also be used in the terrain management to water sensitive plants and trees. The banks of the Roombeek behind Zilverling have a section where they are a little lower. When the Roombeek is transporting water after heavy rainfall, the water will flow over at this section to the retention pond and reduce the water flow in the Roombeek. All this contributes to reduced flood risk. 

In the Technohal building, collected rainwater is used to flush toilets. The rainwater is stored in a 20m3 tank adjacent to the building. The softened water that is used 1000 hours a year for misting over condensers is also reused for flushing the toilets.

In the Sports centre, Paviljoen and the ground floor of Zilverling, all urinals are waterless.

Many water taps in toilets are equipped with a sensor: on use, the tap runs for 6 seconds. This is shorter than the average user would leave the tap on, resulting in savings of 3,000l/day.

The UT encourages the use of tap water, as this prevents unnecessary plastic use. Several outdoor Join the Pipe water points can be found on campus: on the O&O square, at the athletics track and at the multi-field. Inside, you can refill a bottle in the toilets or at one of the coffee machines. Join The Pipe uses the income generated by these points to fund clean drinking water projects in developing countries. The less plastic bottles we use, the less plastic bottles will have to be transported. For more information, visit Join the Pipe’s website.