Greenhouse horticulture must be virtually emission-free by 2027, which is why a lot of attention is being paid to water reuse. But how do you monitor the quality of the water in the greenhouse? The project 'Water quality quickly in focus' tested the possible use of sensors, with promising results. “This can help horticulturists enormously,” says Arie Draaijer of sensor technology company Sendot.
Quickly check the water quality in the greenhouse with a simple measuring set-up. It is a development that greenhouse horticulture has a great need for. Within a few years, the sector may no longer discharge water into surface water. That is why there is a strong focus on water reuse. But that water must of course be of the right quality to be able to use it for cultivation.
Fast and affordable monitoring
For growers and propagators, focusing on water reuse is a development in which they are looking for affordable and fast ways to monitor water quality themselves. Because conventional methods such as sending water samples to a laboratory are very time-consuming. Being able to act independently on a routine basis is a question to which the project 'Water quality quickly in focus' has been addressed. This was done by testing where correlations can be found between sensor measurements on various parameters and the presence of micro-organisms – a measure of biological water quality.
Relationship between oxygen content and pathogens
“We have found evidence of an association between the occurrence of aerobic microorganisms and the occurrence of pathogens such as Fusarium, a fungus that is harmful to plants,” says Draaijer, scientific manager at Sendot. “For example, by measuring the oxygen content in the water, you could say something about the presence of these aerobic microbes. We want to see if more such relationships can be found. This allows the horticulturist to intervene more quickly when necessary.”
Part of the answer
During the project, Sendot, as a technology supplier, was responsible for developing a simple water quality measurement setup. Besides oxygen and oxygen consumption, pH, UV and chlorophyll fluorescence, turbidity, conductivity and redox potential were also included as parameters. The redox potential, as an estimation of the chemical oxygen demand, seems to be a useful parameter to indicate a possible connection with the microbiology of the water. Nevertheless, KWR researcher Joep van den Broeke has some reservations about this. KWR carried out measurements of the colony number for the project and discovered that an ATP test may be a faster alternative to detect microbial activity in water. “We should conduct more research into the question of whether the redox potential is a good indicator of microbiological water quality in greenhouse horticulture,” says Van den Broeke. “This would be a great development for the horticulturist. For example, with a fairly simple sensor it is possible to find out whether the disinfection used is effective, or whether it needs to be adjusted.” Draaijer is also critical: “Although the measurement set-up can already be used in practice, it needs to be looked at how we can use it to substantiate statements about the growth of micro-organisms in the recirculation water even better. We only have part of the answer.”
Low-tech mobile setup
André van der Wurff can confirm that the attention for water quality in greenhouse horticulture is growing. Van der Wurff works at Groen Agro Control, the project partner that carried out the same measurements on water samples with standardized methods in the laboratory parallel to the sensor setup. The Control in Food & Flowers Foundation was the party that collected all data, analyzed it and brought it together in the final report. Van der Wurff: “When we received a request from Plantum – the trade association for companies in the breeding, propagation and cultivation of seeds and young plants – to come up with something that would give faster insight into water quality, we gladly accepted. . The wish was to have a mobile measuring set-up, with which horticulturists can easily take measurements at various places in the entire water system, including where the emission takes place. Two years later, at the end of the project, there had to be an operational setup. That worked. We opted for a low-tech approach with existing techniques. By linking different sensors to each other, the values can be viewed together on a well-arranged dashboard. This creates an increasingly better picture of the complexity of the water. With the new measurement setup you can say much more about the water quality than with each sensor individually.”
Added value of TKI
The measurement set-up that resulted from the project 'Quickly visualized water quality' can count on enthusiasm from the sector. For example, the setup is now in the greenhouse of a large tomato grower and several growers have come forward who want to try it out, says Draaijer. He is sure that the work will be continued. “A TKI project like this helps us reach the market with our product. In addition, the collaboration with other partners ensures that together we can provide the pieces of the puzzle that horticulturists can use.” For KWR, the project meant performing microbiological analyzes on a new water matrix; that of greenhouse horticulture. And for Groen Agro Control, the project strengthens the service provision to their customers. “The greater the awareness about the importance of water quality, the better we like this,” says Van der Wurff. “In addition to measurements that horticulturists may do themselves in the future with this sensor set-up, we remain the preferred party for performing impartial, certified measurements.”
The project 'Water quality quickly in focus' was carried out by a consortium consisting of renowned research organizations in the field of water quality in horticulture (Foundation Control Food & Flowers and KWR Water Research Institute), specialized measurement and technology companies (Groen Agro Control and Sendot ) and interest groups from crop cultivation (LTO Glaskracht, Plantum). This project is financed by TKI Water Technology, TKI Horticulture & Propagation Materials and STOWA.