Os, E.A., van

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van Os, E.A.

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Water quality: Growers should always start with good quality fresh water

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10
WATER
WATER QUALITY
Growers should always start with good quality fresh water
By Erik van Os, Wageningen UR Greenhouse Horticulture
Good quality fresh water is an important starting 
point for every grower. While sodium is often 
the main contaminant, other problems such 
as algae and biofouling also have to be taken 
into account. The availability of good quality 
fresh water makes recirculation easier and 
minimises the discharge of waste water containing 
nitrogen, phosphorous and plant protection 
products into surface water or groundwater.
Stricter regulations require growers to minimise the emission of nutrients 
and plant protection products to surface water and groundwater. Reasons 
for discharge include;
» excessive levels of sodium in the circulation water
» the presence of growth inhibitors such as 
root exudates or micro-organisms 
» concerns about problems at the start of the cropping season
» an accumulation of plant protection products
» an unbalanced composition of the nutrient solution
» technical failures.
Larger rainwater storage capacity (up to 3000 m3/ha) minimises 
the main problem of sodium accumulation. In Mediterranean 
countries that experience limited amounts and periods
of rainfall, rainwater collection can also be useful.
Algae
Open rainwater basins are easily contaminated by sodium (via 
rain in coastal areas), plant protection products (via atmospheric 
deposition and condensation water) and bird faeces(nitrogen and 
phosphorous). This creates the right basic conditions (light, water,
nitrogen) for algae growth, which not only results in a green soup,
but also clogs the irrigation system (pumps, pipelines and drippers). 
In addition, decaying algae may result in insufﬁcient oxygen levels. 
LG Sound is a company that supplies equipment to eliminate algae
via ultrasonic sound at wavelengths of 20kHz to 2 MHz. Especially 
the most frequently occurring algae (single cell and ﬁlamentous) 
are eliminated within two weeks of installation, after which the 
rainwater basin remains clean and free of algae with minimal 
maintenance. Fish, mosquitoes, daphnias and other organisms are 
not sensitive to ultrasonic sound, and humans cannot even hear it.
Clean water
Minimising the discharge of recirculated nutrient solution starts with
the storage of good quality rainwater. Stored water must remain clean 
and ultrasonic sound waves help to keep the water free from algae.
Partners in this seminar: LG Sound     ,
Wageningen UR Greenhouse Horticulture


Water quality: Growers should always start with good quality fresh water

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