Water and water protection

Flughafen Zürich AG uses fresh water frugally. Waste water is cleaned in different ways depending on its origin.

Fresh water

The fresh water used at Zurich Airport comes from three different sources: firstly, drinking water comes from the municipal water supply for the town of Kloten. During the year under review, consumption of this was 7.2% less than in the previous year. Secondly, groundwater is pumped away from under the main airport complex to keep dry older buildings that cannot be adequately sealed. Some of this water is used in technical processes and the remainder is channelled into the river Glatt. Thirdly, rainwater is used for flushing some toilets.

GENERAL DRAINAGE PLAN

In line with its “avoid-separate-treat” approach, Flughafen Zürich AG aims to produce as little waste water as possible. Along with measures to ensure drainage systems comply with the law, its general drainage plan includes stipulations relating to the operation and maintenance of the existing sewage and pump systems.

Domestic and industrial waste water

The various types of waste water that arise at Zurich Airport are treated in different ways. All domestic waste water, from toilets or restaurant kitchens for example, is channelled into the local sewage treatment plant at Kloten-Opfikon where it is treated. The sewage plant, which is a joint venture between Flughafen Zürich AG and the municipalities of Kloten and Opfikon, is currently being renovated and extended (while operations continue uninterrupted). 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 on the airport premises before it can likewise be sent to the sewage plant.

Aircraft and runway de-icing

In order to ensure safe flight operations, in winter it is essential to keep both aircraft and operational areas free of ice. During the winter of 2018/19, 2,113 m3 of de-icing agents (propylene glycol) were used for aircraft de-icing (2% less than the previous year). 1,364 m3 of liquid de-icing agents (–14%) were required for runways, taxiways and aprons. 349 tonnes of conventional de-icing salts were additionally used on service roads, in the car parks and around the maintenance area. The total amount of de-icing agents applied was higher than the long-term average. However, the quantity of de-icing agents used can vary considerably from one winter to another depending on the amount of precipitation and ambient temperatures.

Treatment of waste water from de-icing operations

Highly concentrated de-icer runoff is collected in a basin then distilled in the airport’s own plant.

De-icing aircraft with hot water and propylene glycol as well as spraying potassium formate-based de-icing agents on operating surfaces results in waste water contaminated with carbon compounds. If waste water were to enter natural watercourses untreated, it would remove oxygen from the water and therefore cause problems for aquatic organisms. To prevent this, the waste water is collected and is then treated depending on the level of carbon concentration. Water that is only slightly polluted is first channelled through retention filter basins and then into the Glatt. Medium-contaminated waste water is sprayed over grassed areas using a special sprinkler system. As the water filters down through the soil, the glycol it contains biodegrades completely. Heavily contaminated waste water is treated in the airportʼs two distillation plants, where the glycol is concentrated and then supplied as a raw material to industrial companies.

Over the winter of 2018/19, at 94% the amount of run-off collected was slightly higher than the previous year. Of the 512 tonnes of carbon captured, 30 tonnes (2018: 40 tonnes) or 6% flowed untreated into the Glatt. Flughafen Zürich AG is continually investing in further optimisation measures and adding new airside operating areas to the treatment system.

Amount of collected run-off from de-icing operations.