To handle this situation each deicing pad is equipped with its own supply station, including storage tanks for Type I and Type IV fluids, refill taps for the deicing vehicles, ready room for staff, control system for pumps, tank-heating equipment and floodlights. The control of the collecting system is also performed from each station.
Eventually the airport built 12 of these deicing pads and supply stations. Approximately 95 percent of all aircraft flying out of the airport are deiced at these sites.
Each deicing pad is supplied with a fleet of Vestergaard deicing vehicles, namely, the Elephant Beta and the Elephant Beta-15. EFM, the airport’s deicing company, nicknamed these vehicles, “polar bears.” Each polar bear can hold approximately 6,000 liters (1,585 gallons) of Type I and 2,000 liters (528 gallons) of Type IV fluid. (EFM also uses the company’s Elephant My for the 5 percent of planes that are deiced on the apron.)
THE FIRST STEP
All remote deicing pads drain the used fluid into underground tanks. About 60 percent of the fluid is routinely recaptured in this way.
As you can imagine, the fluid is mixed with plenty of water from melted snow and ice.
“High dilution of the collected fluid creates a water logistics problem,” Bergstrom added, “and the recycling costs rise dramatically.
To combat this, the collected fluid is first sent to small diversion tanks that measure the glycol concentration. Fluid with a 5 percent glycol concentration or more is pumped to another underground tank for transportation by tanker trucks to the recycling plant. Concentrations lower than 5 percent are pumped into the storm water retention basin where it is metered to the local sewage treatment plant.
Once at the plant, the reclaimed fluid is treated in four steps:
A mechanical cleaning removes impurities such as sand, oil, aircraft fuel and other “dirt.”
A chemical cleaning uses absorption and ion exchanger units to remove heavy metals and controls the pH of the fluid. This step essentially results in a water and glycol mix, but which still contains too much water.
An evaporation process vaporizes the excess water and, therefore, concentrates the glycol. An interesting side note to this process: The steam produced is fed back by a heat exchanger to the airport’s district heating system. About 90 percent of the energy consumed by the evaporation process is recovered for the heating system.
When enough water is evaporated and the glycol reaches the correct ratio, it’s pumped into a batch tank. During the pumping, an additive package is dosed into the fluid. These additives are specially designed by Clariant for the process and returns to the fluid the “missing links” so that all specifications for Type I are met.
When one 43,000-liter (11,359-gallon) batch tank is filled, the process switches to the next batch tank. A quality control check on the produced batch is performed. All data is logged and a certificate is made for each batch. One liter from each batch tank is kept for one year at the plant and 0.1 liters is sent to Clariant for backup control.
What can go wrong? Normally, a monitoring system provides an alarm and corrects the process automatically before large volumes are incorrectly produced. However, disapproved fluid is pumped back to the original collecting tanks and processed from the start all over again.
One last quality check is performed when trucks are filled at the plant before transporting the recycled fluid to each of the deicing pad’s supply stations. A sample from each tanker is also kept for one year.
“All fluid movements and data are logged by the recycling personnel,” Bergstrom said. “Due to this system, it is possible to follow the fluid throughout the entire system.”
From start to finish, the recycled fluid can be put back into use in a matter of just a few days.