In the BMBF-funded WaterReTUNe project, a key objective is to test innovative concepts for the desalination of further purified wastewater treatment plant effluents. In the future, the effluents from municipal wastewater treatment plants can become an important resource for covering agricultural water needs in particular. The concept pursued in the project consists of feeding the largely pre-purified wastewater treatment plant effluents into a two-stage membrane plant consisting of a nanofiltration stage (NF) and a reverse osmosis stage (RO). The NF has the task of carrying out partial desalination and using the permeate (filtrate) to produce very high-quality service water with almost drinking water quality.
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Since the very well purified wastewater treatment plant effluent has only a relatively low salt content, partial desalination is sufficient in the first step. However, the NF concentrate contains all the salts and other constituents of the treated wastewater in concentrated form. To minimise the volume and increase the total yield of low-salt water, this concentrate is fed into a second membrane stage RO. This RO produces a very low-salt water as filtrate and a very small concentrate flow.
The two membrane stages were assembled by EvU Innovative Umwelttechnik GmbH in a test plant container according to the specifications and dimensioning by FiW with all the necessary containers, pumps, fittings, pipelines and electrical engineering to form a transportable test plant. Special requirements such as heat resistance and high pressure resistance had to be taken into account. In addition, an uninterruptible power supply was installed.
The plant integrated into the container is now located in Tunisia and is operated by CERTE - a Tunisian state water research institute in research mode. It reliably produces desalinated water for various other experimental fields and also concentrate, which is also used for experiments.