The most common antifreeze components for chilled water are monoethylene glycol (MEG) and monopropylene glycol (MPG)
Propylene glycol is usually preferred to ethylene glycol nowadays due it being less hazardous with less impact to the environment and on sewage treatment processes when discharged
Water containing glycol is more corrosive than pure water so it is essential that it is used in combination with corrosion inhibitors. It is also important to note that all water treatment chemicals should be checked to ensure they are compatible with glycol
Glycol solutions are also thicker than pure water, therefore harder to pump before they reach their freezing point
It is vital to keep glycol concentrations >20% – Lower concentrations provide a nutrient source (carbon) for bacteria, whereas higher concentrations are actually biocidal and kill bacteria!
It is therefore very important that glycol levels are checked and corrected after any water replacement as this could dilute the glycol. Levels can be tested using density measures or optical properties
pH is also important to monitor closely as the breakdown products of glycol are acidic
Presence of glycol can interfere with laboratory tests so labs should be informed of glycol presence prior to analysis