23.7 Application
23.7.1 Application equipment shall be cleaned thoroughly before the first fill with de-icing/anti-icing fluid, in order to prevent fluid contamination. Fluid in trucks should not be heated in confined or poorly ventilated areas such as hangars. The integrity (viscosity) of the Type II and IV fluids at the spray nozzle should be checked annually, preferably at the beginning of the winter season.
23.8 Environment and health
23.8.1 Besides water, de-icing/anti-icing fluids contain glycols and different additives as main ingredients. Type II and IV fluids also contain a thickener system. The glycols used are bivalent alcohols. Glycols are colorless fluids with a sweet taste (not recommended to try).
Issue II 02.07.2009 Rev. 0
23.8.2 Regarding environmental compatibility, the most important criteria are biodegradability and toxicity.
23.9 Biological degradation
23.9.1 The single glycols, like monoethylene, diethylene and propyleneglycol, are entirely biodegradable. Biodegradable means that a conversion is achieved by aerobe bacteria changing glycol to water and carbon dioxide by the aid of oxygen.
23.9.2 For the different glycols, there are minor differences with regards to the rapidity of biodegradation and the oxygen used. Also, the temperature is an important parameter. Biodegradation occures faster at higher temperatures, and slower at lower temperatures. The best way to handle waste fluids is to drain them into local waste water treatment plants. Fluids can be drained into surface waters during winter, as the oxygen content will be higher than during summer. The colder the water, the more oxygen is available. Substantial drainage into surface waters during summer is not ideal as the biodegradation occurs faster and, moreover, less oxygen is available. The overall effect on surface waters can be adverse in such a case.
23.9.3 The glycols mentioned are practically non-toxic versus bacteria. Exceptionally high amounts (10 to 20 grams per liter water) would be necessary to adversely affect the biodegradation. These concentrations are effectively never reached, therefore biodegradation generally occurs. Nevertheless, caution should be exercised in this matter. The thickener system of Type II and IV fluids, approximately 1% of volume of the fluid, is totally neutral to the environment. It will not be biodegraded but has no negative effects on the environment; it may be compared to a pebble. The additives and inhibitors can have an effect on the overall biodegradability. In any case, the fluids have to meet local regulations concerning biodegradability and toxicity.
23.10 Toxicity
23.10.1 Although biodegradable, monoethylene-glycol should be considered as harmful if swallowed. The principal toxic effects of ethylene glycol are kidney damage, in most cases with fatal results.
23.10.2 Several reports concerning the toxicity of diethyleneglycol showed that it can be compared to glycerin in this matter; glycerin is considered to be non-toxic. Propyleneglycol is classified as non-toxic. A special pure quality is used in the pharmaceutical, cosmetic, tobacco and beverages industry. Propyleneglycol is not irritating and the conversion in the human body occurs via intermediate products of the natural metabolism. However, the standard precautions taken when handling chemicals should be adopted when handling glycols.
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