Water

The availability of sufficient clean drinking water is by no means a matter of course. The Zurich Airport Group therefore uses this resource sparingly.

Relevance

Clean water is a precious resource which the Zurich Airport Group is committed to conserving at all its airports. Along with minimising the volume of fresh water consumed, the company also has wastewater appropriately treated to save on fresh water so a sufficient supply of it remains available for the region.

Various types of wastewater are produced at airports, each of which are treated in different ways. These include domestic wastewater, aircraft sewage and wastewater from workshops, as well as runoff from operational areas and from aircraft de-icing.

Approach

Fresh water

Zurich Airport obtains drinking water from the municipal water supply for the town of Kloten. In addition, groundwater is used as process water and for toilet flushing. As some parts of the airport’s infrastructure are located below ground, they are at risk if the groundwater table rises above a critical level. Groundwater is therefore constantly pumped away from under the main airport complex. Rainwater is used to flush some toilets, which additionally helps to control rainwater runoff.

The airports in Latin America likewise obtain their drinking water from the public water supply. Florianópolis gets 30–50% of the water it needs from treated rainwater and wastewater, which it uses for toilet flushing, irrigation and fire service drills, among other things.

Noida Airport in India plans to meet 80% of its fresh water needs with treated rainwater. As Noida lies in a tropical zone with seasonal heavy precipitation, rainwater is stored in tanks for use later in the year.

Wastewater

Like the municipalities in the canton, Zurich Airport has its own general drainage plan (GEP) which sets out the basic principles for water protection on the airfield. Following the “avoid – separate – treat” approach, the aim is to produce as little wastewater as possible. Along with measures to ensure airfield drainage systems comply with the law, the drainage plan includes stipulations relating to the operation and maintenance of the existing sewage and pump systems.

After separation, the wastewater produced at Zurich Airport is treated in different ways. All domestic waste water, from toilets or restaurant kitchens for example, is discharged into the local sewage treatment plant at Kloten-Opfikon where it is treated. The contents of grease separators are sent to a biogas plant. Special wastewater, from workshops or from aircraft toilets for example, requires pre-treatment before it can likewise be sent on to the sewage plant.

The airports in Latin America all have their own wastewater treatment plants. In Macaé, Brazil, a new treatment plant will also be built by 2023 as part of the new terminal construction project. Whereas treated wastewater is discharged into the ocean in Iquique in Chile, in Antofagasta it is used for irrigating green areas.

A separate wastewater treatment plant is planned for Noida in India in order to produce greywater that can be used for cooling and irrigation purposes, for instance.

Aircraft and surface de-icing

In order to ensure safe flight operations, in winter it is essential to keep both aircraft and operational areas at Zurich Airport free of ice. The winter of 2020/2021 was marked by frequent snowfalls. The actual precipitation volume was nevertheless average, and temperatures were relatively mild from a long-term standpoint. While an average amount of surface de-icing agents was used, the amount of de-icing agent consumed was well below average due to the low volume of air traffic. Propylene glycol is used for aircraft de-icing, whereas formate is used as a surface de-icing agent. Conventional de-icing salts are used on service roads, in the car parks and around the maintenance area.

Wastewater runoff from operational areas contaminated with de-icing agents is collected and, depending on the degree of contamination, is treated in one of three ways (more detailed information can be found online at Zurich Airport De-Icing Wastewater). One unique feature is the spraying of medium-contaminated wastewater over suitable green areas. As the water percolates down through the soil, the carbon compounds from the propylene glycol and the formate biodegrade, thus cleaning the water in the process. To assess the success of the cleaning systems, the degree of treatment is calculated for each winter season. This indicates what percentage of carbon contained in the collected wastewater was removed. Owing to the exceptional situation with far less aircraft de-icing required but at the same time a relatively large volume of wastewater runoff from operational areas, the degree of treatment fell from 98% to 88% during the 2020/2021 winter season. At 23 tonnes, the effectively untreated amount of carbon was slightly below the long-term average however.

Key data