Water

Clean drinking water is not a matter of course. The Zurich Airport Group therefore uses water resources sparingly.

Relevance

Clean water is a precious resource which Flughafen Zürich AG is committed to conserving at all its airports. Along with minimising the volume of fresh water consumed, the company also ensures wastewater is appropriately treated to keep watercourses clean. Various types of wastewater are produced at airports, each of which must be 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 around 20% of the water it needs from treated rainwater and wastewater, which it uses for toilet flushing, irrigation and fire service drills, among other things. All three majority-owned airports in Brazil have programmes aimed at reducing their consumption of fresh water and boosting the use of greywater.

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 will be 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 meet the regulations, the drainage plan includes stipulations relating to the operation and maintenance of the existing sewage and pump systems. During the reporting year, a completely revised GEP laying out plans for approximately the next twenty years was submitted. The plan includes various measures for extending the wastewater infrastructure as and when required in line with the further development of the airport.

Following the basic GEP principle, the wastewater produced at Zurich Airport is separated and then treated. All domestic wastewater, 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 likewise being sent on to the sewage plant.

The airports in Latin America all have their own wastewater treatment plants. 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 2021/2022 was mild with below-average precipitation. The amount of surface de-icing agents used was consequently only half the long-term average, while the amount of aircraft de-icer consumed was likewise well below average due to the continuing 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. This method of treatment has been used for many years already. In the period under review, following long-term monitoring, it was verified that this spraying of wastewater over green areas has no adverse effects on the vegetation. As a result, during the reporting year Flughafen Zürich AG received a permit to operate its de-icing runoff treatment plants indefinitely. These had previously been time-limited after phases 1 and 2.

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