Water

The careful use of water and the treatment of waste water is a given for the Zurich Airport Group.

Relevance

Airports use significant quantities of fresh water and at the same time produce large amounts of waste water. The Zurich Airport Group safeguards clean water at all its sites by reducing the use of fresh water to a minimum and ensuring that waste water is treated correctly. There is a wide range of different types of waste water that need to be treated separately. These include domestic waste water, aircraft sewage and waste water from workshops, as well as runoff from areas used for flight operations and from aircraft de-icing.

Approach

Fresh water

Zurich Airport Ltd. obtains drinking water for the entire Zurich Airport from the municipal water supply for the town of Kloten. It also pumps groundwater itself. This is because some of the infrastructure buildings are located in groundwater-bearing subsoil and are at risk if the groundwater table rises above a critical level. Pumped groundwater is used for technical and industrial processes and for flushing toilets. Rainwater collected on roofs is also used for some of the flushing water. This also helps to regulate the discharge volume of rainwater. As in the previous year, it was not possible to obtain groundwater to the full extent in the main airport complex due to construction work, which meant that more drinking water had to be fed in until summer.

The airports of the Zurich Airport Group in Latin America likewise obtain their drinking water from the public water supply and are constantly taking steps to reduce their demand for fresh water. The “Aqua Project” is still underway at the airports in Brazil. The project pursues three main objectives: reducing demand, measuring consumption accurately and treating used water.

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

Waste water

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 “prevent – separate – treat” approach, the aim is to produce as little waste water as possible. Along with measures to ensure that airfield drainage systems meet regulations, the drainage plan includes stipulations relating to the operation and maintenance of the existing sewage and pump systems.

In accordance with the drainage plan, the waste water produced at Zurich Airport is separated and suitably treated. All domestic waste water, from toilets or restaurant kitchens for example, is discharged completely into the intercommunal sewage treatment plant (STP) at Kloten-Opfikon, where it is treated. The contents of grease separators are sent to a biogas plant. Special waste water, 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 STPs from which the treated water is directly discharged into watercourses or, as in Florianópolis in Brazil and Antofagasta in Chile, used locally for irrigation purposes. The airport in Noida, India, also has its own STP, which will go into operation in 2026 and replace the existing temporary plant.

Aircraft and runway de-icing

To ensure safe flight operations, both the aircraft and the operating areas at Zurich Airport must be kept free of ice in winter. Overall, the winter of 2024/2025 was warmer than average. This was compounded by below-average rainfall, which is why the amount of de-icing substances applied was also below-average. In the case of aircraft de-icing agents, on the other hand, the amount used was higher than average, which is due to frequent weather conditions with temperatures around freezing point. Aircraft are de-iced with propylene glycol, while formates are used for runway de-icing. Conventional road salt is used on roads, in multi-storey car parks and in the maintenance workshop.

Waste water runoff from operating areas contaminated with de-icing agents is collected and treated in one of three ways depending on the degree of contamination (more information can be found online: Zurich Airport De-Icing Waste Water). One unique feature of treatment is the spraying of medium-contaminated waste water over suitable green areas. As the water percolates down through the soil, the carbon compounds from the propylene glycol and the formate degrade, thus cleaning the waste water in the process. To make even better use of the existing spray irrigation areas, further optimisation measures were implemented last winter. In addition, new areas were connected in the west and south to extend the catchment area to a total of 150 hectares.

To assess the success of the system, the degree of treatment is calculated for each winter season. This indicates what percentage of carbon contained in the collected waste water was removed. In winter 2024/2025, the treatment level was 95% (previous year: 90%). This means that the effective amount of carbon that was washed away untreated was reduced significantly compared to the previous year.

Key data