Concepts for the treatment of spent process water in the food and beverage industries

In the food and beverage industries, spent process water streams containing very different levels of contamination are combined and routed to the mixing and equalizing tank where problems in biological wastewater treatment occur. It could be shown that the treatment of the partial streams for different applications resulted in major benefits while problems with biological wastewater treatment could be minimized or even eliminated. For example, tests showed that the product could be recovered from the highly contaminated pre-rinsing water in production plants and water of drinking quality could be produced from the mixed spent process water. The process steps to achieve this, can be simplified as follows: a) for product recovery: integrated microfiltration and oil skimming; for water reuse: 1) pretreatment to remove suspended solids, droplets and the bulk amount of dissolved organic impurities as well as to reject the microorganisms (membrane biology); 2) Membrane filtration to remove residual dissolved inorganic and organic impurities (two-stage nanofiltration); 3) UV disinfection to ensure that the treated water will ultimately meet the legal bacteriological standards for drinking water.

It was possible to illustrate that, in the food and beverage industries, the product can be recovered from the highly contaminated spent process water and water of drinking quality for reuse can be obtained from the mixed spent process water by appropriate treatment: For product recovery: integrated microfiltration and oil skimming. For water reuse: pretreatment (membrane bioreactor), two-stage NF and UV disinfection. It was shown by numerous chemical and microbiological analyses that with appropriate design and build-up of the treatment plants as well as suitable cleaning procedure for the plants that the limit values for water reuse could be adhered to at all times.