A Case Study of Stormwater Runoff Containing Deicing / Anti-icing Fluids Treatment at DFW Airport 2003-01-2123
Airline tenants at Dallas/Fort Worth International Airport (DFW Airport) use deicing/anti-icing chemicals, as may be needed, to maintain wintertime operations. DFW Airport has implemented best management practices for pollution prevention measures relating to deicing/anti-icing activities. However, as the planes leave the deicing pads, deicing/anti-icing fluids can drip from the planes onto the runways, taxiways, and ramp areas. As planes take off, the fluids can also shear off onto Airport property. During winter storm events, these deicing/anti-icing fluids are flushed off the runways, etc., with the stormwater. Stormwater containing deicing/anti-icing fluids can discharge through outfalls into Trigg Lake located in the southwestern part of the DFW Airport property.
Due to concerns regarding deicing/anti-icing fluids discharged to Trigg Lake during wintertime inclement weather conditions, especially freezing precipitation events, a process definition of the condition of Trigg Lake was performed. Samples were collected to define the important water chemistry relative to both the biology of Trigg Lake and biodegradation of glycol in Trigg Lake. Aquatic toxicity tests and Trigg Lake ethylene glycol biodegradation simulation studies were also performed using Type 1 and Type 4 deicing fluids. Concept engineering analyses were performed for process definition of the engineered solutions for adequate treatment of glycol, oxygen dissolution, and mixing requirements in Trigg Lake. Both the oxygen demand and oxygen transfer or dissolution requirements into Trigg Lake were defined under projected operating conditions (glycol releases).
A Phase I concept design was developed from the Trigg Lake simulation studies and implemented at the beginning of the 2001-2002 deicing season. Brush rotor aeration equipment was installed in the main body (deep water portion) of Trigg Lake. No notices of violation were received from any regulatory agency for glycol discharges into Trigg Lake during the 2001-2002 deicing season. Lake monitoring data for the 2001-2002 deicing season are presented along with the study program methodology, test results, conclusions, and concept engineering design recommendations.
Following the 2001-2002 deicing season, Phase II process engineering evaluations of the condition of Trigg Lake were performed to assess the needs for addition of more brush rotor aeration capacity in the shallow water portion of Trigg Lake. A concept engineering study and design were performed to develop the best technical and economical solution for mixing/aeration of the north shallow zone of the lake. A detailed analysis of the 2001-2002 Trigg Lake deicing season water quality monitoring data was performed. Factors evaluated included water temperature, dissolved oxygen concentrations, pH, turbidity, and glycol concentrations. Data was evaluated from the monitoring stations at the north end, south end, and middle lake locations. The lake was profiled (gauged) in order to develop locations and aerator sizing to accomplish the most efficient mixing and aeration of the north part of the lake. The number and size of the aerators were designed to match the lake contour, depth, and area in the north shallow zone. The results of the Phase II process engineering evaluations are presented.