Showering gets you basil:

Using wastewater for herb cultivation

In the park at the Berlin Gleisdreck, right next to the volleyball fields of "Beach 61", lettuces, basil, rocket, chard, sage, oregano and parsley sprout on a wooden wall four meters wide. The plants are stuck in eight white steles placed next to each other and connected by a couple of hoses, the Berliner Zeitung reports.

The whole thing looks like an art installation, but it is a model project of the TU Berlin: "We want to test and show here how wastewater can be treated in a mobile plant and reused on site," says Grit Bürgow. She is a lecturer in the Department of Urban Planning and Settlement and project coordinator of the Roof Water Farm in Kreuzberg. An IBA housing project from 1987 combines water treatment with space-saving cultivation methods for salad and vegetables. The model project at the beach volleyball facility is now a continuation of this, which is being funded by the Ministry of Education as part of the Gardening Services research project.

The plants growing on an outer wall of the showers are supplied with the treated wastewater. "Every day, 1000 liters of shower water are collected here, cleaned and then used to water the plants," says Andreas Horn. Horn studies urban design at the TU and designed and built the so-called shower towers together with Grit Bürgow and students from the Roof Water Farm project workshop.

Microorganisms clean the water
The heart of the system is the water house: In three large black tanks, microorganisms clean the water of soap residues, shampoo, skin particles and other dirt until it is clean enough to be used for irrigation without any problems. Water samples are taken regularly to ensure that the applicable guidelines are adhered to.

From the water house a pipe leads past several vats with reed once around the shower installation up to the plant steles. The purified water finally ends up in a 200-liter tank, where it is enriched with fertilizer, regulated to the appropriate pH value and transported to the plants.

The herbs and lettuces do not grow in soil, the roots come directly in contact with the nutrient solution. Expanded clay balls give them the necessary hold. Every hour they are sprinkled from above for five minutes. The water flows down in the steles and from there back into the irrigation tank. A closed circuit. "Such a system, which can do without soil and is therefore much lighter, is called hydroponics. It has the advantage that you only use a small amount of water and can fertilize the plants precisely," says Horn.

Actually, the plant wall should already be installed in spring. But because of corona, construction was delayed by several months. The showers of the beach volleyball facility can only be used again since July.

So for just under two months now, wastewater has been accumulating again, which can be used to water the plants after they have been treated. On Tuesday the first harvest was made. In normal years, at least four to five harvests are possible during the beach volleyball season from May to September. Then the yield should also be large enough to be used in the affiliated gastronomy.

Source: Berliner Zeitung 

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