Most discharges to water from the airports take place during the winter when aircraft and runways are de-iced for aviation safety reasons. The use of more environmentally chemicals, the collection of chemicals and treatment of water from the runways are examples of measures that reduce the impact on watercourses in the vicinity of our airports.
De-icing of aircraft and runways
Snow and ice on the wings and stabilisers of aircraft could dramatically impede operation of the aircraft and in the worst case could cause an accident. So prior to take-off, aircraft are de-iced with a mixture of propylene glycol and hot water.
To prevent take-off and landing runways from becoming slippery, field maintenance vehicles such as ploughs and sweepers are mainly used. When this is insufficient, de-icing agents must be used to melt the ice. For several years now, potassium formate – a compound that has far better environmental properties than its predecessor, urea – has been used. This has improved the quality of surface water and reduced the risk of eutrophication or overenrichment of watercourses.
Measures to reduce Swedavia’s environmental impact
Both propylene glycol and potassium formate as such have a low level of toxicity and are readily biodegradable. The problem is that this requires a great deal of oxygen to break down the compounds, thus causing a lack of oxygen in watercourses and surface water if large quantities are discharged.
Therefore, during the winter most of the glycol that runs off the plane is suctioned up by special vehicles. The glycol collected is recycled into new glycol, broken down for the production of biogas or used as a source of charcoal for the nitrogen removal process in water treatment. The de-icing agent used on runways and the glycol that drips off aircraft as they taxi out end up in the surface water from runways and aprons. The surface water at most airports is directed into water treatment ponds before it reaches a watercourse.
Another measure to reduce glycol use is preventive de-icing. This involves spraying a smaller amount of glycol on the aircraft immediately after landing. The glycol serves as protection so that ice does not form on the body of the aircraft during turnaround. If the plane is free of ice for take-off, no further de-icing is necessary. Glycol can be saved using this method, thus reducing the environmental impact.
All airports must comply with the criteria outlined in the EU Water Framework Directive*, so a number of airports have also updated their control programmes for monitoring the airport’s impact on water.
Wastewater sent to water treatment facilities
Polluted wastewater from Swedavia’s workshops, firefighting sites, vehicle washing facilities and aircraft lavatories as well as from external properties at the airports is directed via wastewater sewage pipes to water treatment facilities. Wastewater from the airports contains oil and some heavy metals. Inspections of chemical handling and grease separators at the airports minimise the environmental impact of discharges into the wastewater system.
* EU Water Framework Directive: In the EU, there has been a common framework since 2000 to ensure good water quality for Europe’s surface water and groundwater. The directive requires that EU Member States work in a standardised way with a focus on reducing pollution, promoting sustainable water use and improving the condition of water-dependent ecosystems.
The EU Water Framework Directive covers all lakes, watercourses, coastal waters and groundwater. The general objective is for all occurrences of water to have good water status by 2015, or by 2027 at the latest. This applies to biological and chemical conditions in surface water as well as groundwater status. These standards are applied, for instance, when government agencies and local authorities exercise environmental oversight or are involved in social planning.