Antifreeze and Engine Coolant Recycling
There was a great debate for nearly a decade surrounding the technologies that were used to "recycle" engine coolant. Finally, ASTM published two specifications: ASTM D6471 pertaining to pre-diluted light coolants, and ASTM D6472 for light duty antifreeze concentrates. ASTM D6210 mandates that, for heavy duty diesels, recycled coolant must be as free from contaminates and perform as well as virgin coolants.
Coolant can be recycled properly using distillation, or a combination of reverse osmosis and ion exchange.
Proper recycling cleans all the chemicals from used engine coolant and results in a clear recovered base fluid. The recovered coolant base is then treated with an inhibitor to result in a recycled coolant that is literally impossible to differentiate from virgin coolant mixed with purified water.
Since 1990 a number of companies have entered the coolant recycling market with various systems. The debate as to the merit of these systems and their applicability to cars and trucks still hasn't been completely settled, and perhaps considering the commercial pressures that are present, they may never be.
It is accurate to say that filtration systems do not, and can not, remove many of the chemical contaminants in used coolant. They argue that they have developed offsetting technology that returns the coolant to a serviceable condition, at least for a while.
It is also accurate to report that technology exists that completely cleans used engine coolant, recovering pure glycol or glycol and water. Properly reinhibited, these coolants perform just like virgin coolants, and since many of them are sold as "ready to use" (prediluted) products they even eliminate concerns relating to hard water or chlorinated water.
A heavy duty diesel engine, at a cost of $30,000 to 300,000 is a major piece of equipment. None of the diesel OEMs permit filtration recycled coolant in their systems. Properly recycled coolant, that meets the virgin specification, is accepted. This is evidence that the job can be well, benefiting the environment and conserving fossil fuel resources (from which glycols are derived)
Coolants recycled by professional, commercial companies using distillation or a combination of reverse osmosis and ion exchange are cost-effective and have been demonstrated to work as well as virgin products
Coolants processed by filtration systems are, at best, controversial.
