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such a way that it would reduce lifecycle and OPEX costs as well as increase biodiversity and improve monitoring.


PROVEN OUTPUTS ELSEWHERE A $9m, FBA™ wastewater treatment system was being used at Buffalo Airport, New York and recording outstanding removal rates. It was an aerated, wetland system situated alongside the runway with little risk of bird strike as it had no areas of open water as it was was planted with grass. Heathrow was able to reconfigure its constructed wetland with aeration such that it would remove a minimum of 3,500 kg of BOD per day.


FBA™ ON TRIAL Full scale trials were set up in the winter of 2009-10 to monitor the contaminant load and to test the constructed wetlands’ ability to remove deicer components. “The trial showed FBA™ could remove ten times the BOD load compared with passive wetlands,” says Tori. “We knew Heathrow would definitely see a ten-fold increase as we had yet to fine-tune the system to optimise energy use and oxygen transfer rates. We also wanted to cater for the higher volumes and concentrations of contaminated wastewater which come with harsher winters,” says Tori. WORKS START BAA commissioned ARM to optimise all of its 12 constructed wetlands at its Mayfield Farm Treatment Facility in October 2010. By retrofitting FBA™, Heathrow would see a much higher return on its investment – both economically and environmentally. Even with a harsh winter, the new


FBA™ system has delivered beyond the promise it showed at the trial by improving removal rates by a factor of 14.


ONGOING MAINTENANCE Heathrow’s operations staff need only occasionally intervene with the water treatment works at Mayfield which is managed via a SCADA (supervisory control and data acquisition) system to ensure it remains flexible to storage and treatment demands as loadings fluctuate with the climate. “Natural wastewater treatment


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systems require management of nutrient and bacteria levels to ensure there is enough biomass to treat the contaminants,” says Tori. “Heathrow now has online instrumentation at its Mayfield site which monitors and controls various stages of the treatment process so that they work together as an integrated whole.”


Before


Design loading rate of 590Kg COD/d


Designed to receive 40L/s


Primary reservoir


Floating reed bed (FRB) section


After


Design loading rate of 1900kg COD/d


Designed to receive 40L/s


Primary reservoir now regu- larly dosed with nutrient


Half of the FRB section was relocated to another Heathrow Airport Ltd site. Submerged aeration was retro-fitted creating a com- plete mix zone. Remaining FRB is now partially aerated (partial mix zone). Nutrient dosing added


Balancing lagoon


HABITAT ZONE Heathrow has seen three major benefits by upgrading to FBA™: Cost: upgrading the original facility is considerably cheaper than installing a new one and will reap considerable savings in the long-term. Performance monitoring: the new SCADA system means the environment team can control and monitor performance remotely which means minimal on-site intervention. Biodiversity: the reeds provide habitats for birds, bats and the insects on which they feed, contributing to the airport’s biodiversity action plan. Safety is the watchword at Heathrow so these constructed wetlands are located well away from the danger zone. “By upgrading yet staying within the


12 HSSF Constructed wetlands 0.5m deep


Aeration improved in balancing lagoon


12 existing passive systems re-engineered (distribution, collection & reconfigura- tion) and retro-fitted with FBA with gravel depth increased by 83%


Total of 36,000m3 of storage prior to reed beds


Glycol removed anaero- bically


Low microbe count due to lack of nutrients – limiting factor


Unchanged


Glycol removed aerobically Nutrient dosing added to ensure maximum microbial communities to provide treatment


to integrated, sustainable, wastewater treatment solutions to meet the demands of best and worst deicing scenarios. All in all, Heathrow is very pleased with their investment in FBA™,” says Tori. “It’s raised their game in reducing the airport’s environmental impact as well as cutting operating costs for many years to come.” Russell Knight, Heathrow’s


footprint of the original facility, the dramatic results we saw in the trials have come true in the full-scale project so we’ve created headroom to cater for severe winter conditions,” says Tori. “In order to minimise the impact of deicing activities on the environment and the inherent costs in managing wastewater, airports will need to commit


environmental operations manager, adds: “This facility allows us to continue fulfilling our commitments to running Heathrow responsibly and efficiently. We’re delighted that this upgrade has improved treatment performance by a factor of 14 which is a huge step forward in getting the most out of this innovative solution.”


AF


For more information visit: www.airportfocusinternational.com


AF / January 2014 / 13


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