Background The "suspension technique" used to produce most PVC (S-PVC) plastic is a batch process for polymerisation in an aqueous phase. It uses vinylchloride, fully demineralised water, as well as initiators, dispersing agents and other auxiliary substances. After several hours in an autoclave, approximately 90% of the vinylchloride converts to PVC. A degassing step removes the residual monomers from the PVC and water for recycling. However even after centrifuging, the water fraction still contains between 50-300g/m³ residual PVC (worldwide this amounts to around 40 000 metric tons PVC/year). Currently reuse of this water and PVC for batch processes is not possible due to major quality problems. Therefore, this water – about 2.7-3.7 m3 per metric ton of PVC (or worldwide 90 million m³/ year) – runs off to the wastewater treatment plant, where it leads to increased AOX (absorbable organic halogens) amounts in the sewage sludge, which then has to be treated as hazardous waste. Objectives The main objective of the project was to optimise the S-PVC process through the introduction of innovative filtration methods that would recycle up to 40% of the used process water and at least 80% of the separated PVC. Filtering the process water reduces the amount of PVC particles in the process water rendering it suitable for reuse in the polymerization process. The filtered PVC particles would then be fed back into the production process. As a result, there would be a significant reduction in freshwater use and unused PVC. Results The project substantially improved the liquid phase of the S-PVC production process. Conventionally, the decantation wastewater contains 50-500 mg/litre PVC and is treated in a biological wastewater treatment unit. Reuse, prior to the PVClean LIFE project, was not possible due to quality problems caused by the residual PVC content. The project developed a specially adapted ultra filtration to recuperate considerable amounts of the water. The treated water, free of PVC solids can be recycled into the polymerisation process. The project was very successful both ecologically and economically: The ceramic filter membranes chosen showed a high performance and long operating time. The large-scale demonstration plant was set up and run without problems. The demonstration phase showed a better than expected durability of the filter elements and enabled a very profitable overall operation. Technical highlights included: Water savings (m³/year de-ionised water) – 252 000; Recycling rate (water) – 50%; Water demand (m³ de-ionised water /tons PVC) – better than planned ie 1.5 compared with Reduction of wastewater (m³/year) – higher than forecast ie 300 000, compared with expected 252 000 due to fewer production lines; Savings on water, wastewater, additives (€/a) – 530 000; amortisation period at full capacity (annual savings – ie actual costs, divided by investment costs) is c. 5 years making the technology potentially very profitable.Finally, an unexpected benefit was the reduction of dispersion additive, as a large part of it is recycled with the permeate of the ultra filtration (parts of the additive of the S-PVC reactor are not retained by the ceramic filter). Additionally, the technology allows further optimisation (up to 90% recycling rate could be achieved in a test) in the future. However, the beneficiary says the current achievement of 50% will be tested for several years, before further investment. Further information on the project can be found in the project's layman report (see "Read more" section).