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Memstill: water cycle closure for good irrigation water

In the context of the European Water Framework Directive, the Dutch greenhouse horticulture sector has made agreements with the national government on targets that will reduce emissions of pesticides and nutrients almost to zero in 2027. Purification initiatives and emission reductions are expected in 2016. TNO's Memstill technology, a combination of distillation and membrane filtration, gives the greenhouse horticulture sector options.

Several years ago TNO developed a distillation technology with membranes for sea water desalination: Memstill. This technology also has applications in greenhouse horticulture, as this sector now has to contend with stricter rules for the discharge of nutrients and pesticides and also wants to reduce energy consumption. Good quality irrigation water is important for the health and productivity of crops. Irrigation water often consists of rainwater and groundwater and is reused several times as recirculation water. However, groundwater is often saline and recirculation water contains xenobiotic substances such as pesticides. Therefore neither is clean enough to use as irrigation water without purification.

Pilot study membrane distillation

As part of the Greenhouse Horticulture Waterproof Substrate Culture project, the feasibility of Memstill was studied at a greenhouse horticulture operation using a pilot installation in 2012. The project's goal was to prevent emissions of nitrates, phosphates, and pesticides from substrate crops in greenhouses.

The Memstill pilot installation was able to reduce the concentration in the supplied drain water by a factor of 7 to 8, which means that more than 80% of the water can be recovered. The pilot shows a high retention of salts and nutrients. The Memstill membrane distillation technology offers possibilities. It is expected that following market development and upscaling it will be possible to reduce the current initial costs, while the variable costs are now already lower than for reverse osmosis.

Wilfred Appelman MSc MBA

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Wilfred Appelman MSc MBA

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