In engine manufacturing, water is used to create an emulsion with coolants for milling and turning, and for washing or rinsing during the finishing of cylinder heads, crank cases, crank shafts and connecting rods.

BMW first introduced a waste water treatment system using nanofiltration technology at Steyr in 2003. The results from that system were so successful that BMW determined it could introduce a completely enclosed water cycle for production, according to Franz Hornbachner, responsible for planning “fluid technology.”

The waste water goes through three stages. First, oil residues are removed from the waste water by ultrafiltration. Then heavy metals and low-volatility lipophilic substances—i.e. surfactants (surface-active substances)—are removed from the water by nanofiltration. In the third stage of the waste water treatment, dissolved salts and short-chain organic compounds are removed by reverse osmosis. The process only uses these physical methods, without the addition of any chemicals.

The BMW Group has invested around €1.5 million (US$1.9 million) in these technologies over the last three years.