Veolia Water Technologies UK (VWT UK) completed a pioneering glycol removal plant at Heathrow Airport, the first of its kind to treat glycol in this application in the UK.
VWT UK was selected due to its expertise in water treatment technologies and services, and for the cost-effective bespoke solution its experienced team put forward.
The challenge was to provide a biological wastewater treatment plant to treat the glycol runoff from the airport runways prior to its discharge into the River Crane. Glycol is commonly found in anti-freeze solutions and is used as a de-icer on aircrafts during the winter months.
Given this seasonal demand, it was also necessary to create a solution that could be kept in a semi-ready state throughout the summer.
After a competitive bid, VWT UK was selected to design, supply, install, commission and operate the plant. This means that VWT UK will continue to operate the new plant for the next nine years, having secured a further operations contract which began in December 2019.
The new glycol removal plant takes water from a runway collection lagoon, processes it and discharges it into a separate four-part clean water lagoon, prior to its release into the River Crane. The plant itself includes two 1,100m3 AnoxKaldnes™ Moving Bed Biological Reactor (MBBR) biological treatment tanks, through which the effluent passes.
Next, the water enters a coagulation tank, followed by a flocculation tank before the solid flocs are filtered through one of VWT UK’s Hydrotech Discfilters. The filtered solids, or sludge, are then thickened and disposed of while the treated water is discharged to the clean side of the lagoon. In total, the plant processes 720,000 litres of runoff water per hour and 550kg of biochemical oxygen demand (BOD) per day.
An aerobic wastewater treatment method, MBBR systems use active biofilm carriers made from plastic with large surface areas on which bacteria can grow with optimal culture conditions. The carriers are kept constantly in motion within the tanks using aeration, allowing the bacteria to break down organic material in the wastewater – in this case BOD, of which glycol is rich, and ammonia. The large surface area of the carriers in the AnoxKaldnes™ patented MBBR systems enable the treatment of a high quantity of wastewater using a very small footprint. The bespoke MBBR solution for Heathrow was developed and tested on a small scale at the AnoxKaldnes™ laboratory in Sweden using sample water provided by Heathrow to ensure that the technology would provide the necessary level of ttreatment.
The plant also has space to increase the hydraulic capacity with the addition of a third MBBR system, should it be required by Heathrow in the future.
"Working with Veolia Water Technologies on this project has been great,” commented the Heathrow project team. “We had some testing conditions and difficult situations early on during the project but the Veolia project team really turned site performance around.”
“Health and safety protocol on site has also been brilliant and the project team were always willing to help and provide solutions to changes in the works information and delivery of the plant. Any problem we threw at them – the VWT UK team came up with a solution.”