Wastewater recycling in laundries—From pilot to large-scale plant

A new, innovative wastewater recycling process for industrial laundries has been developed through cooperation between Textil-Service Klingelmeyer (a medium-size laundry in Darmstadt, Germany) and the University of Applied Sciences in Karlsruhe, Germany. The project “Laundry Innovative Wastewater Recycling Technology—LIWATEC” was sponsored by the European Community in its LIFE-Environment programme. The purpose of the LIWATEC project was to design and start up a new, innovative, integrated process using membrane technology for wastewater reuse on a large scale in the Klingelmeyer laundry. The large scale plant was designed for wastewater treatment capacity of 200 m3/day. This integrated process has been successfully tested for 5 years in the form of two pilot plants at the laundry in Darmstadt and at the University of Karlsruhe (capacities: 10 m3/day and <1 m3/day). The pilot plant data provided a scale up basis for designing the large plant. This paper gives a summary of the pilot plant data in comparison with the initial results of the large-scale unit, which went into operation in June 2006. The integrated process comprises a membrane bioreactor (MBR) with submerged plate and frame microfiltration membranes as the principal cleaning unit. The results of the pilot agree with those of the large-scale plant. The chemical oxygen demand (COD) removal efficiency was around 90%; the average flux was approximately 14 L/m2 h. The MBR permeate provides a water quality that can be used as washing water since it fully meets the requirements of the washing process. Part of the MBR permeate is subsequently treated by reverse osmosis (RO) filtration using spiral wound modules in order to remove salts. The average flux of the RO unit is 25–30 L/m2 h at around 16 bar. The salt retention rate exceeds 99%. The high quality of the reverse osmosis permeate meets the demands of the rinsing processes. In general, up to 90% of total wastewater can be reused. Moreover, it is an easy-handling and cost-efficient wastewater recycling process that could be adapted to different types of laundries due to its modular structure.