Reduction of water consumption and wastewater quantities in the food industry by water recycling using membrane processes

Due to the rising costs for fresh and wastewater, the treatment and reuse of low-contaminated process water streams from food processing companies is increasingly gaining in importance. In this study it was shown that water for reuse could be produced from this water by a specific treatment using membrane processes while achieving reduction of water consumption and wastewater quantities. Three examples of low-contaminated wastewater will be discussed: firstly a vapour condensate from milk processing, secondly chiller shower water from the meat processing industry and thirdly wash water from bottle washing machines. Due to the promising laboratory and pilot-scale experimental results, a demonstration plant with a capacity of 1-2m(3)/h, consisting of the following stages, was set up: pretreatment; main treatment - 1st nanofiltration stage; post-treatment - 2nd nanofiltration or low-pressure reverse osmosis stage and UV water disinfection. Economical water treatment was possible in all three examples. The treated low-contaminated process water from chiller showers or bottle washing machines was of drinking quality and therefore suitable for reuse. After treatment, the vapour condensate could be reused as boiler make-up water which is subject to higher standards than drinking water. The experimental technology underwent an authorization procedure at the Saarland Ministry for Health, Germany, and was granted approval.