Circular water provision in horticulture: Water from the greenhouse Water treatment and reuse

Water supply is of crucial importance for greenhouse horticulture. An adequate supply of fresh (irrigation) water has to be available – during dry periods as well – and the water needs to be clean and not contain too many salts. Commitments have moreover been made to significantly decrease discharges of plant protection products from greenhouse horticulture in the years ahead and, ultimately, to eliminate them altogether.

This project is part of a coherent programme which should result in an integrated and sustainable (irrigation) water provision: the securing of ‘good irrigation water’, reduction of the use of disinfectants, and zero emissions of nutrients and environmentally-alien substances. The cluster research programme, ‘Circular Water Provision for (Greenhouse) Horticulture’, consists of four projects:

  1. Water to the greenhouse: freshwater provision and well technology
  2. Water in the greenhouse: microbially ‘healthy’ irrigation water
  3. Water from the greenhouse: water treatment and reuse
  4. Operate: operating circular irrigation water systems

Within these four projects the supply, discharge and use of water on a scale beyond that of the individual horticulturalist are studied. In this way, a sharper focus can be placed on closing the water cycle, increasing the sector’s self-sufficiency, assuring efficient water use, matching (regional) water surpluses and shortages in time and place, and reusing water.


This projects answers the question concerning the extent to which advanced oxidation processes (AOPs) can be used to improve the quality of discharge water through the transformation of plant protection products (PPPs). The research examines whether discharges with AOP-treated water have a negative impact on the (ecological) quality of the surface water. And we define the degree to which selected PPPs are degraded by different AOPs. The goal is to achieve the purification efficiency of 95% – which is officially prescribed starting 1 January 2018 – without any formation of substances that have a negative impact on water quality.

The objectives are pursued by the project partners named below, with the collaboration of Wageningen University’s Greenhouse Horticulture business unit.


Research is conducted into the removal of PPPs from ‘standard water’ using the typical treatment techniques. On the basis of previous research at Wageningen University & Research (WUR), the application of AOP was shown to be the most feasible for greenhouse agriculture. Not only specifically UV/H2O2 oxidation, but also alternatives like O3/UV and O3/H2O2 are studied on a pilot-installation scale. This involves the use of bio-assay analyses to determine, for different process settings, whether the AOP-treated discharge water has a negative impact on the (ecological) quality of the surface water. And we define the degree to which selected PPPs are degraded by different AOPs. There is no decision concerning the use of ACF following AOP. In view of cost increases, preference should be given to systems that are sufficiently efficient to render the use of ACF unnecessary. The pilot-installation research was carried out in 2015. The findings are currently being processed into a report.


To realise the objectives, the following deliverables are expected:

  1. Insight into the formation of potentially genotoxic compounds in the standard water under the impact of the AOP treatment.
  2. An impression of the impact of AOP treatment on the toxicity for aquatic organisms.
  3. Purification efficiency for 12 selected PPPs after the application of 7 (combinations of) AOP technologies.
  4. Overview of chemical parameters in the treated standard water.