The attention for water systems in greenhouse horticulture has increased due to legislation, with the purification obligation for greenhouse horticulture on discharging water. A grower then right away looks at the filters in the watering system, which are a major source of discharges with their backwash.
What is filtration intended for?
Until a few years ago, filtration was only used to protect technical components in the water installation against blockages, such as the disinfectant and the drippers, explains Cees de Haan of ECOfilter. "So filtration was actually a bitter necessity to keep the water system functional."
In 2019, water is discharged less and recycled more often. In this process, harmful substances accumulate in the water. This accumulation results in more pollution in the water system with higher risks of disease spread and the build-up of bio-film. Due to all these changes in water management, a better filtration system has taken on a more important role in greenhouse horticulture.
Filtration always the first step
Whether we look at water treatment in greenhouse horticulture, industry, drinking water or waste water treatment, all forms of water treatment start with the most important step: filtration. "This is for the simple reason that everything that we initially filter out of the water, we no longer have to remove from the water with more expensive equipment or dosing chemicals."
What is filtration?
Filtration is always easy to explain on the basis of a tea bag, says Cees. "As soon as a tea bag is immersed in water, the water will discolour due to substances going into solution. We call this dissolved substances. Small particles go through the tea bag and lie on the bottom of the cup. We call this floating substances. The large parts remain in the tea bag and we call these solids."
Solid, floating and dissolved substances
Solids are the substances that clog and contaminate the water system. In the past, filtration was always used for this in greenhouse horticulture.
Floating and dissolved substances circulate in the water system and, among other things, feed the bio-film in pipes and can settle in silos and thus cause a breeding ground for fungi and bacteria. These substances increase the use of disinfectants in the water system, lower the T10 values for UV systems, contaminate the heaters and ensure extra dosing of hydrogen peroxide (H2O2) or other products to keep pipes clean.
The ideal filtration in greenhouse horticulture is a filter that filters solids, suspended matter and dissolved substances, according to Cees. "Unfortunately, this is not financially viable. The best available filtration techniques are capable of filtering the solids, suspended matter and a small part of the dissolved substances. The filters that were previously used in greenhouse horticulture only filter the solids."
Cees: "Investments in better filtration immediately pay off with better water quality, better disinfection and less use of disinfectant, such as H2O2 doses, in the watering system."
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