Surface water: a sustainable solution for good quality irrigation water

Waste water can be purified into good quality irrigation water. This is demonstrated by the ‘Delft Blue Water’ project. The project consists of two phases. In phase one, the best way of purifying wastewater has been researched. In phase two, the project was carried out at a Dutch tomato grower, Cock van Schie from Kwintsheul, the Netherlands. The surface water was modified into good quality irrigation water.

Greenhouse crops need a lot of irrigation water. The water, collected in the tanks is an important buffer. However, this is not sufficient. Additionally, groundwater is used which is purified into irrigation water by a reverse osmosis process. Nowadays, this technique knows more and more disadvantages, says Van Schie. “After the osmosis treatment, too much sodium remains in the purified water. This is a result of the salinization of the groundwater in the Westland region, the Netherlands. The salt surplus needs to be drained off, together with valuable nutrients, which is a financial and environmental disadvantage.”

Alternatively, water can be processed from surface water into good quality irrigation water on a local level. “The project at Van Schie is a trial version and is conducted together with his neighbour, Guus Van Leeuwen, a chrysanthemum grower. Between both greenhouses, a membrane installation has been installed. This installation processes good quality irrigation water, without sodium and chloride. “Membranes are filters with microscopic holes that are able to filter salt molecules out of the water”, explains Jan Willem Mulder from Evides, the Netherlands. According to him, this method provides the growers in the area with sufficient good quality irrigation water. "Rainwater is and remains the main source. However, especially in the summer, with little rain and high production, this will not be enough. Moreover, the government limits on the back pumping brine (salt residue after desalting groundwater) in the soil. Therefore, growers proper alternatives are essential."

Even though, environment and sustainability are of high importance to Van Schie, the economical situation in the sector also plays an important role. Economically speaking, the sector experiences difficulties. Therefore, it is important that this project will also bring advantages for the growers.

Currently, the membrane installation is in service. For now, only tap water is used. On the short term, purified surface water will be used.

Source: Glastuinbouw Waterproof, by Roger Abbenhuijs