Suspension PVC is produced in an aqueous process. Approx. 2.3 m3 of precious water are used in a conventional process per ton of PVC. Up to now this water could only be used for flushing purposes, but the demand for flush water in the downstream units is small compared with the water demand for polymerization. So the water is usually discharged after treatment in a biological waste water treatment to a recipient.
Re-use of the waste water in the polymerization was so far inhibited by quality problems caused by the residual PVC solid content. But today the required purity can be achieved by a tailor-made special filtration process.