water airplane

During the winter months, runoff from waste water contaminated with glycol is produced when planes are de-iced. In the winter of 2005 – 2006 the waste water contaminated with glycol was collected and stored at various locations at Schiphol airport. The concentrations of glycol varied from 3% to 10%. In the past, waste water containing glycol was discharged to external treatment plants. Schiphol no longer regards this as desirable and has contacted Evides Industrial Water in connection with this specific waste water problem. As the operator of the existing Schiphol waste water treatment plant located at Schiphol-Oost, Evides was happy to work on developing a solution to this waste water problem.
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Action plan
Evides Industrial Water conducted market research on the possible techniques for treating waste water contaminated with glycol. In the United States and Canada, concentrators are widely used for the physical treating of such water. Evides Industrial Water presented an action plan to Schiphol that calls for using a concentrator to concentrate water containing glycol into an end product that can be used as a raw material for industrial processes. Killfrost type 2, the de-icing product used during the winter of 2005/2006, contains additives, including polymers. The type 2 de-icer is used at Schiphol because of the longer distances plans must taxi to reach the runways for takeoff. Inland Technologies, which supplies the concentrator, had no experience with this type of de-icing product. Inland Technologies saw the effects of the additives in the type 2 de-icer as a problem in terms of clogging and dirtying, and because of this could not guarantee that operations would be done efficiently and economically. It was necessary to pre-treat the de-icer before use to remove the polymers.

Pre-treatment and test location
Prior to a full-scale test, the de-icer was subjected to ultra-filtration to separate out the polymers. On the basis of financial and operational considerations, this pre-treatment was not selected. On the basis of robustness of technology and lower operating costs, a coagulation/flocculation pre-treatment was selected. During the period from May until September of 2006, a glycol concentrator for pre-treatment was erected on the Schiphol grounds and the full-scale test was performed. The treatment capacity of the installation was approximately 20 cubic metres daily, depending on the glycol concentration in the waste water. The amount of runoff of wastewater contaminated with glycol is strongly influenced by weather conditions. In the winter of 2005/2006, approximately 10,000 cubic metres of waste water contaminated with glycol (in both high and low concentrations) were produced. The high concentrate was worked up with the concentrator and the low concentrate was treated biologically in the aerating ponds built by Schiphol.

Conclusions
During the period from May until September of 2006, Evides Industrial Water was commissioned by Schiphol to operate the concentrator for pre-treating. The following results were achieved:
- Treating of the waste water contaminated with glycol is feasible using a combination of the concentrator and a coagulation/flocculation pre-treatment.
- The end product is of a commercial quality and will be used subsequently as a raw material in industrial processes.
- Following an aerobic post-treatment, the residual product is suitable for discharge to surface water.

And further
Evides has been awarded a subsequent contract by Schiphol to continue operating the concentrator and the aerating ponds for the coming year.