French airport runoff pollution management (water and sludge): toward a new approach based on constructed wetlands? Case of Aéroports de Paris – Orly (France)

One of the environmental concerns for airport managers is stormwater management. Three kinds of contamination occur at airports: (1) chronic contamination, (2) seasonal contamination associated with de-icing procedures and (3) accidental pollution. At Orly Airport, a stormwater treatment plant (STEP) is devoted to removing chronic pollution. About 4 million m³ of water are processed yearly by the STEP, producing about 50–100 t of sludge. Mainly contaminated by petroleum hydrocarbons (Hc), it is removed as final wastes. During the winter, the STEP is unable to treat organic load associated with de-icers (formate and glycol). In order to improve onsite stormwater management, two experiments were carried out in real conditions between 2008 and 2010. The first one dealt with the ability of two vertical flow planted beds (VFPB) associated with two kinds of plant to treat waters contaminated by de-icers. Organic loads of up to 2,094 mg/L chemical oxygen demand (COD) were passed through sand filters in a closed-loop system. Organic degradation was characterized by a first-order kinetic constant driven by nutrient availability. Nutrient (N, P) addition was then necessary to reach treatment objectives (40 mg/L COD). The second system evaluated sludge Hc removal by four VFPB associated with several plant species. This experiment showed that the measured Hc removal rates of 70% for sludge and 95% for water did not depend on the choice of plant and that a rest time was necessary to allow Hc removal. Finally, a treatment system, based on VFPB, should be a good alternative which could optimize both sludge and contaminated water management.