News article

Practical solutions for water reuse in Horticulture

By Richard Crowhurst for Greenhouse Yearbook & Buyers Guide
Priva Vialux-Line
Water Management
27 July 2022

Increased emphasis on resource use and preventing pollution, together with the potential for climate change to make water an increasingly scarce (or even costly) resource, means that growers are looking to maximise water use efficiency. In controlled environments, such as greenhouses and indoor farms, one option is to treat, clean and re-use drain water for crop irrigation and fertigation.

While the idea is not new, challenges remain about the potential for the build-up of disease, nutrients and crop protection chemicals. Priva offers solutions to enable water reuse and recycling to be carried out effectively and efficiently.

A sustainable environment with healthy surface water is becoming more and more important
Kathryn Smethurst

Business Development Manager - Horticulture and Indoor Growing UK

Kathryn Smethurst

Kathryn Smethurst, Business Development Manager at Priva continues: “There has been movement in recent years from government authorities to tighten up the use of natural resources and where we get our water from, and the next logical step would be further legislation in this area. Many growers are seeing these signals and the interest in investment for this technology is growing rapidly. There is also pressure on the industry to show green credentials and sustainable responsibility to the supply chain and ultimately the consumer.”

Savings on fertilizers

She also points out that as well as the ‘push’ factors, there are also benefits for growers when it comes to recycling water: “The good news is that there is also a financial case for reduction in water and fertilizer use by using recirculation technology, particularly in these times where fertilizer is hard to get hold of and very expensive. An added side benefit will be helping to ensure longevity of crop protection agent use.”

“A good percentage of new primary supply is still necessary because the balance of the fertilizer used by the crop needs to be refreshed,” points out Kathryn. “Recirculation technology can be used on any growing system but the more water that has to be treated then the bigger that system needs to be. The main options include thermal disinfection, ultra-filtration, ozone and UV disinfection and there are pros and cons for each technology.”

Approved by Wageningen University

Priva has developed products using UV disinfection which has a relatively inexpensive operational expenditure, no harmful chemicals or toxic by-products, and a highly controlled process with multiple safeguards and feedback to the customer. “The products have been independently tested with Wageningen university and Priva can advise on the level of dose required for each crop,” adds Kathryn.

Priva Vialux M Line E Line 20170725 (2)

How does UV disinfection work?

The Priva system collects the drain water, which is filtered and then stored in the ‘dirty’ drain water basin. As a precautionary measure, the drain water is then disinfected by the Priva Vialux UV disinfection systems, which can remove moulds, bacteria and nematodes, and make viruses inactive – including specific viruses such as the Pepino mosaic virus. “This allows continuous recirculation of irrigation water in a safe way,” says Kathryn. “As a result, expensive fertilizers are not flushed down the drain and do not contaminate the environment. The EC pre-mixing allows you to reuse the drain water to the greatest possible extent; this is mixed with the necessary ratio of fresh water before fertilizers are added. This means that you are not only looking after the environment but saving money on your water and fertilizer costs.”

Research & development

One feature that Priva and others are working on is providing growers with more real time information about the nutrient content of the drain water. “The holy grail for companies like Priva would be to be able to provide real time feedback on fertilizers in the drain water, so that the perfect mix could be dosed for the crop in the next irrigation cycle,” says Kathryn. “Research and development in this area has been tried for many years so far though without the level of consistency in results that is required for any commercial release. We will keep working on it though.”

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