Due to water scarcity and water pollution, the importance of water reuse is increasing more and more. As part of a German research programme on water reuse, the effluent of a wastewater treatment plant in the coastal region of northern Germany was used to investigate the direct treatment of tertiary effluent within the project MULTI-ReUse. A modular constructed pilot system has been operated to optimize different treatment chains producing different water qualities simultaneously. The technological focus was put on membrane technologies, namely ultrafiltration (UF) and reverse osmosis (RO), and also biofiltration, adsorption and disinfection were part of the piloting. Beside the development of monitoring strategies for ensuring biological and chemical safe water qualities, the operational stability and the safe transport of water to the consumers were examined. The direct treatment of wastewater is a demanding task due to the lack of dilution and hydraulic retention time in the receiving water (environmental buffer). However, the multiple barrier approach guaranteed constant secure water. Fine adjustments of individual processes were particularly important. A stable operation of the UF could be realized in particular by using more or less intermitting inline coagulation as coating. The RO performance could be improved significantly by using monochloramine as disinfectant to minimize biofouling.


  • The first project in Germany on direct reuse of municipal wastewater for industrial purposes.

  • Optimization of UF operation by initial hydroxide coating followed by low levels of coagulant dosing.

  • Implementation of an ultra-low-pressure reverse osmosis membrane (ULPRO).

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