Wastewater treatment in plastics recycling

Recycling lines for plastics are the circular economy’s lynchpins – and as such, make a vital contribution towards protecting our natural environment and economizing on valuable resources. On the other hand, they also consume resources, chief among them water.

Which goes to show - A recycling technology’s sustainability must not be assessed by the quality of its end-product alone. The processes used to make this product play an equally important role. As a recycling line manufacturer, Krones sees itself as bearing a particular responsibility for meeting these sustainability criteria.

Sustainable product, sustainable process

The Group’s MetaPure technology recovers materials like PET bottles and polyolefin packages – in a quality enabling the recyclate obtained to be used in equivalent applications. In their work aimed at continuous system optimization, the development people at Krones have now also been proactively examining the washing module’s water consumption.

Product Manager Astrid Kadlubski explains the background involved, “In the recycling process, the plastics are ground into flakes in wet mills and then washed. This produces wastewater containing various dissolved substances, depending on the input material concerned.” In addition to a common soiling, these include organic residues of the packages’ content, such as cleaning agents from the washing process and printing ink particles removed from bottles and labels.

Lower water consumption, higher output quality

Kadlubski explains, “In many recycling lines, the water is recirculated and treated in a bypass. With the result that the process water’s dirt load keeps on rising and ultimately impairs the end-product’s quality.” To counter this, Krones has, in conjunction with a prestigious associate, developed an intelligent solution for the complete treatment of the washing and mill water. That entails several advantages for recycling-line operation.

“Firstly, this reduces both freshwater consumption and wastewater incidence. Secondly, the recycling process is kept at a consistently high level of quality,” explains Kadlubski. “And last but not least, such treatment makes sure that the wastewater discharged into the municipal system complies with the relevant specifications. This also applies to the ultra-stringent regulations in Germany.”