CONSTRUCTED WETLANDS FOR AIRPORT RUNOFF ―THE LONDON HEATHROW EXPERIENCE

摘要

The winter of 2001/2002 sees the operational commissioning of a ￡0 million integrated constructed wetland at Heathrow Airport. In recent years the Airport authorities have been concerned about the potential ecological and environmental stresses that runoff from the airfield can cause on receiving water bodies. In particular, the impact of de-icant contaminated runoff containing glycols has been of primary interest. In selecting a remediation technique for the treatment of de-icant contaminated runoff, the Airport authorities reviewed the performance of a number of technologies including reverse osmosis and catalytic oxidation, as well as discharge to the local sewage treatment works. Included in this review was the use of constructed wetlands but although a great deal of experience existed in using such systems for domestic wastewater no data was available on their performance for treating glycol. In response to this Heathrow commissioned the design and construction of trial reedbed system and sponsored a three year research programme managed by Middlesex University. The trial system comprised surface and sub-surface flow reedbeds and rafted reedbeds. The beds were dosed with glycol both at 'background' levels and as 'shock' loads. Besides treatment performance, the microbiological function of the systems was investigated. The results from the trials were used to inform the selection process for an appropriate treatment technique and the eventual design of a full-scale scheme. The resulting scheme, known as The Heathrow Constructed Wetlands, is made up of an integrated system of aerated balancing ponds together with rafted and sub-surface reedbeds covering an area of over 10 hectares. The process of design and construction has been guided by a commitment to sustainable development and the scheme demonstrates a variety of techniques and novel engineering solutions. Various key performance indicators have been applied to the scheme with the outcome that the Heathrow Wetlands have been nominated as a demonstration project in the British Government's 'Movement For Innovation' initiative. This paper presents the findings of the trial reedbed performance for glycol attenuation and the process by which the implementation of the scheme has achieved recognised sustainable development status.