Project Details

Project Delivery

Project Results

Discussion

Situation

In recent years, the recycling rate for plastics and thus the plastic recycling wastewater treatment in Croatia has increased by leaps and bounds. The reason for this was Croatia’s accession to the European Union in 2013, which means that Croatia is also obliged to comply with the Green Deal. Among other things, this provides for a gradual increase in the recycling share of newly manufactured plastic products. Plastic recycling wastewater treatment plays a decisive role in this.

A plastic bag manufacturer first recycles the incoming plastic before processing it further. Washing is an important step in the recycling process. This separates dirt particles, chemicals or coarse solids from the plastic. This results in increased COD as well as BOD₅. The client planned to reuse the 15 cubic metres of wastewater per hour at two different stations in the recycling process.

Problem

The challenge in this plastic recycling wastewater treatment was to split the two wastewater streams. About 10 cubic metres of wastewater per hour were to be cleaned in the conventional way to be reused at the beginning of the recycling process. The remaining five cubic metres were to be ultra-clean to be used for the final step of the washing process.

Solution

To meet this challenge, PPU Umwelttechnik GmbH offered two separate treatment processes. A ClearFox® DAF with upstream mechanical screen was suitable for the larger wastewater flow. The flotation removes up to 99% of all oils and fats dissolved in the wastewater. By adding flocculants, the dissolved substances in the wastewater bind together and leave the plant as sludge.

For ultra-pure wastewater, PPU combined an FBBR module with ultrafiltration. First, the biological process lowers the COD and BOD₅, before the membrane process filters almost all residual substances such as microplastics out of the wastewater. Since the fixed bed biological reactor already metabolises a large part of the dissolved substances, the ultrafiltration is not heavily loaded, which is why the membrane only needs to be replaced very rarely.

Both, the ClearFox® DAF and the ClearFox® FBR produce sludge, which the customer has to remove regularly. To extend these intervals and thus save costs, he also opted for a sludge press, which reduces its volume to a minimum. The ClearFox® team integrated the entire wastewater treatment process into the plastic recycling plant and thus optimally met the customer’s wishes.