Treatment performance of an aerated constructed wetland treating glycol from de-icing operations at a UK airport

摘要

Mayfield Farm Treatment System receives effluent collected from the Southern Catchment of Heathrow Airport, a total of 290 ha. During winter operations, weather-related de-icing activity results in large shifts in the flow and concentrations of airport run-off. The biological treatment of spent de-icing fluids is challenging because it involves the treatment of a cold and nutrient-deficient wastewater of variable flow and strength. After a successful full scale trial to determine the efficacy of aerated wetlands, the entire treatment system was upgraded and optimized in 2010. It consisted of a primary reservoir, partial and complete mix zones, a balancing lagoon, and 12 aerated horizontal sub-surface flow (HSSF) treatment wetlands operating in parallel, with a total wetland area of 2.08 ha. The original non-aerated HSSF wetland system, commissioned in 2001 had a design cBOD(5) loading rate of 374 kg/day at a flow rate of 40 l/s (Revitt et al., 2001; Richter et al., 2003). The aerated HSSF wetlands now have a design cBOD(5) loading rate of 2073 kg/day at a maximum flow rate of 80 l/s. Due to the weather conditions of the UK, the system is event-driven with highly variable flows and loads, with peak cBOD(5) loadings of up to 12,188 kg/day.