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Glycol Treatment at London’s Heathrow Airport. Scott Wallace and Mark Liner – Naturally Wallace Consulting David Cooper and Clodagh Murphy – ARM, Ltd. Russell Knight – British Airport Authority. Aircraft Deicing.
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Glycol Treatment at London’s Heathrow Airport Scott Wallace and Mark Liner – Naturally Wallace Consulting David Cooper and Clodagh Murphy – ARM, Ltd. Russell Knight – British Airport Authority
Aircraft Deicing • Deicing fluids include ethylene glycol (EG), propylene glycol (PG) and diethylene glycol (DEG). • Commonly used as a 50% concentrate form (CBOD5 approximately 200,000 mg/L). • Runoff can contain over 20,000 mg/L at 1 oC • New environmental regulations are requiring treatment of deicing runoff. • Major challenge for conventional treatment plants
Deicing Runoff Treatment Options • Anaerobic Digestion (biogas) • Shock loadings, limited net biogas • Mechanical Treatment (activated sludge, MBRs) • Shock loadings, energy intensive • Discharge to Regional Sewer • Long-term concerns over cost and capacity • Passive (ponds and open-water wetlands) • Land intensive, BASH • Subsurface Flow Treatment Wetlands • No water exposed, land intensive
Original Heathrow Constructed Wetlands • Papers published in 2001 and 2004 • 12 reed beds, total area 2.08 ha • Design flow rate 40 L/s; influent COD of 170 mg/L • Removal efficiency of 30-68%, 24-77 kg/ha-d Richter et al. 2004
Overview of pollution control at Heathrow Causeway Nature Reserve – part of Eastern Balancing Reservoirs Spout Lane Lagoon Clockhouse Lane Pit – Cable 1 part of Princes ski club Mayfield Farm main reservoir
The Case for Upgrading Mayfield Farm • Relatively mild winters post original construction (change in design basis) • More stringent consent limits
Buffalo Niagara International Airport • Heavy snow loads in winter • Airfield operations are heavily dependent on effective deicing operations
Treatability Testing • Measure glycol degradation in both warm and cold temperatures • With and without aeration
Comparing Treatment Effectiveness • Aerated rate coefficient: 5.30 d-1 • Non-aerated rate coefficient: 0.55 d-1 • An aerated wetland is 10X more effective in treating glycol!
Mayfield Farm Treatment Works Original System Re-engineered System Horizontal subsurface flow wetlands Balancing Reservoir Floating treatment wetlands