Finavia aims to reduce environmental loading resulting from substances used in anti-skid treatment and in anti-and de-icing of aircraft through good planning at the construction stage. Water quality is monitored regularly.
At airports the following substances cause loading on waterways
Finavia uses acetates and formates for runway anti-skid treatment. Ground-forwarding companies use propylene glycol based liquids for aircraft anti-icing and de-icing treatment. The substances are not classified as harmful, but they still cause loading on waterways.
Airport winter maintenance is in key position in Finland to ensure the safety and punctuality of air traffic. The northern conditions in Finland require diversely skilled maintenance units and efficient machinery. Winter maintenance at Finavia airports is of high and competitive international standard.
Mechanical methods, sweeping and ploughing, are the main skid-prevention methods used on runways. Chemical anti-skid agents are required for removing frost and ice from the runway surface and for skid prevention.
Substances currently used are sodium acetate, potassium acetate, sodium formate, potassium formate. Liquid substances containing some 50% water, potassium acetate and potassium formate, are used for defrosting and removing thin ice, while thicker ice removal requires granular agents such as sodium acetate or sodium formate. Granular de-icing agents thaw the ice though to the runway survey when necessary, after which the surface is cleared by snow ploughs or sweepers. Most of the anti-skid agents (80%) used at airports are liquid agents, since runways seldom acquire a thick ice surface.
Anti-skid agent usage quantities are listed in the 2012 Annual Report.
Anti-skid agents used at airports are water soluble organic biodegradable substance compounds. While soil’s microorganisms decompose these compounds, they this process consumes oxygen. Up to the mid-90s, the main anti-skid agent was urea, which is a nitrogenous substance that causes surface waters to become eutrophic and increases the amount of nitrogenous compounds in groundwater. The use of urea has been abandoned almost completely due to its environmental impact. In 2000, Finavia published internal instructions forbidding the use of urea at the airports where it impacts groundwater.
Acetates and formates are non-nitrogenous substances that are also used in food and cosmetics industries. Soil bacteria decompose them to water (H2O) and carbon dioxide (CO2). The most notable negative impact of using acetates and formates is the oxygen consumption (0.2–0.7 g O2/1 gram) caused by biodegradation, which is still less than oxygen consumption caused by urea.
Finavia monitors the quality of groundwater and surface waters at most of its airports. We monitor water quality independently and according to the permit conditions or as agreed with environmental authorities. Samples taken from wells, standpipes, outlet ditches of runoff waters and waterways located in the vicinity of airports are analysed for nitrogen compounds (ammonium, nitrate and nitrite), water acidity, chemical oxygen consumption, conductivity and oxygen content. The amount of nitrogen compounds in groundwater is still monitored because of former use of urea.
Owing to the cold and humid winter conditions is Finland, it is common that snow and ice gathers on the surface of the aircraft. For flight-security reasons, they must be removed, as they disrupt the performance and controllability of the aircraft. Moreover, pieces of ice separating from the aircraft surface may be ingested into the engine and cause a failure. De-icing treatment prevents snow from attaching to the aircraft surface and the formation of an ice layer on it during the take-off run and take-off. On cruising level, the humidity and air pressure are low, so the ice-formation is negligible. Aircrafts are equipped with electronic or mechanical de-icing mechanisms in case of ice-formation during the flight. The ground-forwarding companies are responsible for anti-icing and de-icing treatments of aircraft.
In Finland, propylene glycol based liquids are used for both de-and anti-icing. During the preparation, de-icing fluids are added 20–50% water and 1–2% additives. Propylene glycol (C3H6(OH)2) is a highly water soluble and quickly biodegradable substance also used widely is the cosmetics industry. Its greatest hazards are the depletion of oxygen in waters caused by its degradation and the unpleasant odour of the degradation products. Propylene glycol solution requires a relatively large amount of oxygen (0.8–1.2 g 02/ 1 gram of solution), depending on the consistency. In conditions, where the only little oxygen is dissolved in water, the degradation slows down.
Glycol liquid usage quantities are listed in the Environmental information section of the Annual Report.
There is currently no environmentally friendlier alternative for using propylene glycol. The environmental impacts caused by glycol can, however, be mitigated through improved working methods requiring less chemicals and through introducing alternative methods or recovering glycol-contaminated runoffs. The glycol-contaminated runoffs collected at Helsinki-Vantaa airport are processed by the municipal water treatment works. At other airports, glycol water is recovered using suction vehicles in the apron area. Water is recovered at Tampere-Pirkkala, Kuopio, Oulu and Jyväskylä airports. The water is stored in pools and later transferred to the municipal water treatment works. Recovered glycol water can be used in energy production in Imhoff tanks or in water treatment process as a source of carbon. Finavia is responsible for the recovery of glycol water.
Glycol fluids can also be recycled. A few airports abroad have adopted this practice and this possibility is being studied also at Helsinki Airport. The wider introduction of recycling glycol fluids has been hindered by the costs.