Water consumption management in polyethylene terephthalate (PET) bottles washing process via wastewater pretreatment and reuse.

The increasing recycling of polyethylene terephthalate (PET) bottles requires more and more fresh water during washing the bottles. The post-washing wastewater is often treated as effluent, whereas it could be reused in the technological process after appropriate pretreatment. In this paper, coagulation together with flocculation is proposed for use in the pretreatment of the wastewater arising during PET bottles washing. Five flocculants and six coagulants were tested. The turbidity and total organic carbon (TOC) were reduced by up to 98% and 69%, respectively. Out of the tested flocculants, Praestol 611 BC at a dose of 2 mg/dm3 had the best performances. The best coagulant in TOC reduction was PIX-123. As for turbidity reduction, ALS was the best, but PIX-123 was comparable, and therefore, PIX-123 was indicated as most suitable in simultaneous reduction of TOC and turbidity. The coagulation and flocculation together reduced the amount of pollutants and contaminants in the post-washing wastewater to the levels allowing the water to be reused in the washing process, which could bring both economical and ecological benefits.