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Stefan Bakker, Revaho

"It is algae time again!"

With this statement Stefan Bakker, product manager Revaho, indicates that in this time of the year the greenhouse horticulture can be confronted with algae growth in water supplies due to increasing light levels and rising water temperatures. Before an algae explosion occurs, a contamination with algae must take place, and pH-levels and low oxygen levels play a part.

Algae growth
"Due to an explosion of algae, it is possible for a crystal clear water basin or silo to turn into a 'green soup' within days. The water is clear if you put a tape measure into the water and it remains visible for 2 meters or more. With less than 2 meters to 50 centimeters visibility, it is dirty water. With even less visibility the water is really dirty." Filtration at the feeding unit is insufficient for this murky water. It requires a different filter with a larger capacity to remove more particles.

Much waste
Bakker: "If a couple gets into trouble with algae, the problem is not solved easily. Covering the basin or silo kills the algae in a couple of days, after which is sinks to the bottom. For a number of days the grower has to deal with lots of waste."

The much waste moreover comes in a period in which the crops need much water. "If the need for water is twice as high, the waste problem could be tenfold or more, because the waste quantity in case of an algae explosion is extremely high."

The algae problem solves itself in most cases when the temperature drops at night, when the sky is overcast during the day, or when there is rain. Rain brings cold water and oxygen in the water, disrupting the algae growth. The product manager: "The pollution of the tube system and the damage to the growth last longer than a few days and maybe even months."

Prevention is the best
'Prevention is the best cure' is the solution to counter algae growth. "Make sure to cover the basin or silo with tarpaulin to make it light proof, because without light, there is no photosynthesis and the algae will not grow."

Another advantage of covering is that the water temperature is lower, and less water vaporizes. And because there are no waves, the basin or silo can be filled higher.


The product manager gets, in the algae season, lots of questions by growers about the quick pollution of filters. "It is absolutely imperative that the filters are not removed. If that does happen, because the filters are quickly polluted, the high degree of pollution can block the drippers." Sand, disc, or screen filters should be cleaned more often to get rid of the pollution."

A faucet filter should not pollute, but they have to be checked regularly, at least twice a month, and if necessary, cleaned. Faucet filters (130 microns for instance) filter more coarse than the main filter (100 microns for instance) at the unit. Bakker: "A faucet filter is not an after filter, but a so-called 'police filter', which should not pollute. A faucet filter is more like an emergency filter in case matters get out of hand. At that point the police filter intervenes."

Source: Glastuinbouw Waterproof
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