Reuse of Biologically Treated Process Water: Industrial Water Management in the Paper and Sugar Industry

Internal process water cycles have been installed in many industries throughout the last decades. Closing the water cycle is advantageous from the ecological as well as from the economic point of view, mainly because of savings of water and energy. However, closed water cycles may lead to serious operational problems in the production process, such as biofouling and encrustations of limescale. These problems can be avoided by implementing biological wastewater treatment in the internal water cycles. Moreover, energy can be recovered by biological wastewater treatment, particularly if the first treatment step is anaerobic. Examples of heat recovery in the paper industry are presented as well as an example of reuse of biologically treated wastewater in a beet sugar factory. Trends in the application of biological process water treatment for reuse are discussed.