Assuring WWTP effluent for greenhouse horticultural sector

The provision of irrigation water for the greenhouse horticultural sector is under increasing pressure, in part as a consequence of climate change. Alternatives are therefore being sought. Moreover, in the South Holland region, there is a wish to see water handled in a more circular fashion and to investigate the opportunities for the reuse of wastewater more seriously.  Public authorities want to work towards a situation in which maximum reuse is made of treated wastewater, which also implies that less freshwater would flow away into the sea. These two elements are addressed by using treated wastewater as an alternative source of irrigation water in greenhouse horticulture. In this project we will be studying the options for achieving this.


Earlier research demonstrated the possibility of cultivating tomatoes using effluent that had been reprocessed into safe irrigation water, with no losses to crop quality or yield. For minimal safety risks to humans and plants, the quality of the irrigation water needs to be assured. Only then will the use of effluent as a source of irrigation water be accepted through the whole chain, from grower to consumer. In this research we focus on conducting a risk inventory, and on creating a broadly-based monitoring plan to enable the pursuit of follow-up steps within the greenhouse horticultural sector.


We will develop a collective guide that describes the conditions that effluent (but also wastewater from third-parties) needs to satisfy for it to be used as irrigation water. This will lead to greater harmonisation between the parties in the chain. Risks associated with the use of this water to the cultivation, sale, insurance and/or public opinion and public health must be avoided. The continuous monitoring of signal substances, the deployment of sensors, non-invasive monitoring techniques and decision-support systems will be examined. Greater clarity regarding the quality assurance of the water is necessary for it to be seen as a genuine alternative – both in vegetable and ornamental plant cultivation. The basic assumption is that the application of effluent is both technically and economically feasible.


The result will be an overview of the current legal and regulatory framework on the use of effluent in greenhouse horticulture. This overview will be combined with water-quality requirements, so that water that is safe for cultivation can be produced through the tailored processing of the effluent. A risk inventory will also be conducted and a monitoring plan framework created, which will include smart sensors and data processing for a safe use of the irrigation water. By involving the entire chain in stakeholder meetings, we will work towards developing broad acceptance of the use of effluent as a source of irrigation water; from grower to consumer.