Water purification alternatives for greenhouses
What’s the best way to remove impurities in irrigation water for greenhouse horticulture?
Research by the Platform Duurzame Glastuinbouw (‘Sustainable Horticulture Platform’) at Wageningen UR has shown that three water purification technologies are capable of removing 80-100% of crop protection agents present in greenhouse horticulture drainage water. These technologies can help improve the quality of surface water in horticultural regions and contribute to maintaining the availability of crop protection agents for the greenhouse horticulture sector.
Source: Wageningen UR
Last year  the Wageningen UR Greenhouse Horticulture Innovation and Demo Centre (IDC) for Water researched four water purification technologies to determine their effectiveness and feasibility for professional practice:
- ozone with and without an activated carbon filter
- hydrogen peroxide and low-pressure UV system
- hydrogen peroxide and medium-pressure UV system
- electrochemical flocculation
The technologies were tested under semi-real-life conditions using Standard Water, a standardised greenhouse horticulture drainage water containing typical amounts of fertilisers, impurities, and twelve crop protection agents. This was also compared to drainage water from a professional rose business.
Ozone without a carbon filter and hydrogen peroxide with low-pressure and medium-pressure UV systems resulted in an average purification level of 80% (individual substances were broken down at a higher or lower level than this).
When ozone is used with an activated carbon filter, a purification level of 100% can be achieved in the beginning. However, with long-term use, a carbon filter loses some effectiveness and allows some substances through, resulting in a lower level of purification. It is therefore necessary that carbon filters be replaced regularly.
An activated carbon filter can also be used in combination with the other technologies.
In general, all three technologies are equally feasible for use in the horticulture sector.
Cost calculations show that hydrogen peroxide with a low-pressure UV system is the least expensive technology and ozone without a carbon filter is the most expensive. For a business with five hectares of land, the annual costs would range from €1.00 to €2.70 per cubic metre and from less than €0.09 to €0.17 per square metre, depending on the amount of drainage water and the technology used. The use of an activated carbon filter would add about €0.30 to €0.80 per cubic metre and about €0.03 to €0.04 per square metre, assuming it is replaced once every two years.
Electrochemical flocculation achieved purification levels of approximately 40%. In the current pilot set-up, this technology is insufficiently feasible, but with further development it may become a more interesting possibility.
A follow-up study will focus on reducing the costs and improving the effectiveness of the combination of an activated carbon filter with oxidation technology. New purification technologies will also be tested.
More information: ir. EAM (Ellen) Beerling