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Based on a preliminary study (ref 1) which identified a basic core technology system, essentially based on membrane technologies, capable of providing recovery of water from moderately contaminated waste waters like hygiene water and condensation water, a development work was initiated. Results from this development work are presented. The study covers the detailed design of a breadboard of a core system consisting of 3 successive membrane units : Ultrafiltration on mineral membrane, reverse osmosis and electrodialysis, plus an oxidation step. An alternative configuration including a Nanofiltration step is also considered with the aim of decreasing the operating pressure as compared to reverse osmosis. Experimental testing for the selection of individual components and for the definition of operating procedures have been performed. Feasibility demonstration tests on the complete core configuration are being performed using real shower water and condensation water from a cold room.

Electrodialysis (ED) is an electrically driven process that operates at ambiant temperature and pressure. It is of interest for removing ionized molecules, and reconcentrating them, specially at medium and low concentration. It is always used in association with other membrane technologies and/or pretreatment. It is of high interest to simulate the contact of ED membranes with candidate stabilizing or cleaning agents in a water recycling system. We selected among a large and representative range of commercial anionic and cationic membranes, 20 different ED membranes and tested them regarding their resistance to 5 chemical agents. The samples were immerged in the solution (480 h / 60 °C), and a physical characterisation was performed: dimensional stability, measure of electrical resistance, determination of exchange capabilities. Four membranes presented acceptable performances after contact with hydrogen peroxyde (300 ppm) regarding electrical resistance.