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

Agenda Over view of system Case for change Trial winter 2009/10 Aims and objective Scope of quick wins The Mayfield Farm process Contingency Forwards look Questions

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 5 discharge consents covering Heathrow 3 are significant as they drain operational areas of the airfield The other 2 drain roads and car parks (oil interceptors are all that’s needed on these sites) All are regulated by the Environment agency T5 (aka western) & Southern both have limits for de-icing chemical of 40mg/l biochemical oxygen demand (BOD). They both drain into Clockhouse Lane Pit and ultimately the River Thames at Hampton (upstream of drinking water abstraction point!). Eastern is under discussion with the EA but is likely to have a limit of 40mg/l. It drains into the River Crane and then River Thames at Twickenham (downstream of drinking water abstractions). System is designed to trap oil and treat de-icer but not other pollutants High level process = TEST –STORE – TREAT - TEST Photo’s Spout Lane Lagoon – 60,000m3 of storage prior to discharge to foul runoff flows in at upto 430l/s but discharge is limited 50l/s. site of last years £1.2m tankering operation Mayfield Farm Main Reservoir – 36,000m3 of storage prior to treatment in reed beds – focus of quick wins as overloading of the treatment process was the main cause of tankering operation CLP – view from outfalls to ski club run off discharges directly into cable tow water ski lake Causeway nature reserve – final polishing stage of treatment process prior to discharge. EBR combines treat and store in one place. Also provides firewater for majority of airport (except T5 and fuel farm)

The Case for Upgrading Mayfield Farm 2 Drivers – Increasing de-icer usage which results in increased regulatory pressure System was designed based on 90’s data – not surprising it doesn’t cope Exponential growth due to; Changes in aircraft de-icer mix 50:50 to 75:25 - SAE Worse winters Precautionary applications? 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

Aerated rate coefficients, low temperature runs Average CBOD5 (mg/L) k2TIS(d-1) Influent Effluent A 648.8 26.5 4.81 B 679.3 21.0 5.72 C 325.0 10.3 5.63 D 694.0 23.5 5.41 Average 5.39

PG degradation without aeration… Run Average CBOD5 (mg/L) k4TIS(d-1) Influent Effluent A 542.3 212.3 0.68 B 257.0 119.0 0.27 C 177.0 29.0 0.73 D 129.5 33.5 0.51 Average 0.55

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!

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Buffalo – Completed Treatment System

Comparing Heathrow and Buffalo wetlands Heathrow (prior to upgrade) Buffalo Design COD load 590 kg/d 4540 kg/d Area 2.08 ha 1.67 ha Bed Volume 12480 m3 28370 m3 COD Loading 47 g/m3-d 160 g/m3-d (clogging limited) Aeration None 750 kW Oxygen Transfer 2.4 – 7.7 g/m2-d 270 g/m2-d COD Removal 4 – 13 g/m3-d Up to 160 g/m3-d Flow Path Horizontal Vertical (due to high load) Comparing the two systems provides insights for optimizing the Heathrow reed beds and how to increase treatment capacity

Full- ScaleTrial Winter 2009/10

It was demonstrated that adding FBA and nutrient requirements the FBA removed 14 times more BOD than the control. It was found that temperature, whilst influencing the rate of treatment, is not a limiting factor. It was demonstrated that re-engineering the flowpath improved treatment performance. It was evident that a ramping-up regime needs to be implemented prior to the winter season.

Aims and objectives of quick wins Improve environmental outcomes Improve regulator perception Reduce unplanned OPEX Maintain biodiversity during construction and operation Out of scope Long term storage solution Aeration to meet oxygen demands of influent loads Online flow and organics monitoring to optimize performance Nutrient dosing to promote bacterial growth Optimized performance of existing Mayfield Farm works No new tanks or lagoons System optimization minimizes life cycle costs for BAA Mayfield Farm is an existing hard asset Upgrading the existing system improves performance by a factor of up to 14x Upgrade cost is a fraction of original capital expenditure Avoid loss of existing asset and capital expenditure on a new replacement asset

Scope of Heathrow Stormwater Quick Wins Mayfield Farm Treatment Upgrades to Floating Reedbeds, Balancing Lagoon, Horizontal Reedbeds, nutrient dosing facility, power and controls Aeration to Main Reservoir Eastern Balancing Reservoir Aeration to upper pond & lower pond including power and controls Clock House Lane Contingency Aeration including power and controls Spout Lane The ability to increase pumping to foul from 50l/s to 100l/s, improve reliability and reduce cost (subject to TWU approval) DECEMBER 2012 (LHRPSA1133K224P9)

Mayfield Farm Treatment Works Original System Re-engineered System Horizontal subsurface flow wetlands Balancing Reservoir Floating treatment wetlands

Mayfield Farm Treatment Process INFLUENT PRIMARY RESERVOIR FLOATING REED BEDS BALANCING LAGOON HSSF DISCHARGE BOD ANALYSIS PLC NUTRIENT DOSING

Primary Treatment Complete mix (CM) zone permits bacteria to grow relative to influent loads Minimum detention time of 1.5 days provides increased flow through Partial Mix (PM) zones designed for solids sedimentation, storage, and digestion

Secondary Treatment During optimisation phase, the balancing lagoon will be refined as a dynamic system for hydraulic equalization, load equalization, solids management, or treatment Inclusion of aeration provides flexibility with respect to managing variable flows and concentrations

Horizontal Flow Forced Bed Aeration™ Wetland Here we have a basic section through a horizontal system. This comprises a lined excavation filled with media with large stone on the periphery providing support. The Inlet distribution manifold runs along the length of the bed with adjustable ‘Ts’ positioned at intervals to allow adjustment of the flow to ensure it is evenly distributed across the whole bed. The effluent move across the bed and is collected via a field drain on the bottom of the discharge side of the bed from where the effluent passes out through the level control system. This controls the level of the effluent in the bed. It is common following commissioning to raise the level in the bed above the matrix to prevent weeds establishing on the exposed media before the reeds have established themselves. This also prevents rabbits etc from eating the young reeds.

Aerated Wetland Layout 30

Aeration Tubing Plow

Tertiary Treatment

Contingency at Clock House Lane Pit

Thank You for Your Attention