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Variables limiting efficacy of slow filters integrated into closed hydroponic growing systems

Bergstrand, Karl-Johan (2009). Variables limiting efficacy of slow filters integrated into closed hydroponic growing systems. Alnarp : Sveriges lantbruksuniv.
ISBN 978-91-86197-10-0
[Licentiate thesis]

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For sustainable production of greenhouse vegetables and ornamentals, losses of water and nutrients must be avoided. Closed hydroponic systems are highly efficient in their use of water and nutrients, produce high yields and minimise the needs for soil sterilization. However, they carry a risk of dispersal of root-borne pathogens, mainly zoosporic oomycetes, which can cause major crop losses. To prevent this, nutrient solution is of disinfested before reuse by pasteurisation, UV-light treatment, oxidation with ozone or peroxides, or filtration. Slow filtration is a low-cost technique with high efficacy against oomycetes and bacterial pathogens. However, tools for easy monitoring of slow filter efficacy are currently unavailable. Abiotic and biotic factors are critical for slow filter performance. Enzyme activity in the filter skin is a key factor and is a possible predictor of filter efficacy, explaining 50% of the filter efficacy. A number of state variables, e.g. polysaccharides, total organic carbon and oxygen content, were examined in this study in attempts to explain the remaining 50% of efficacy. Abiotic and biotic state variables affecting filter efficacy were monitored for filters subjected to sub-optimal factors such as high electric conductivity or at massive pathogen bombardment. Supporting studies were performed in commercial greenhouses. The main conclusions were that electric conductivity of the nutrient solution affects the efficacy of slow filters, whereas bombardment of the filter skin with pathogen mycelia had minor importance on filter function. The state variables total polysaccharides, biofilm polysaccharides, total organic carbon and oxygen content did not support prediction of filter efficacy. Interactions were found between enzyme activity and the microbial colonisation of the filter skin.

Authors/Creators:Bergstrand, Karl-Johan
Title:Variables limiting efficacy of slow filters integrated into closed hydroponic growing systems
Year of publishing :2009
Number of Pages:40
ALLI. Furtner, B., Bergstrand, K.-J., Brand, T., Jung, V. & Alsanius, B.W. (2007). Abiotic and Biotic Factors in Slow Filters Integrated to Hydroponic Systems. European Journal of Horticultural Sciences 72 (3), 104-112 II. Alsanius, B.W., Bergstrand, K.-J., Furtner, B., Jung, V., & Brand, T. Electrical conductivity as a limiting factor for efficacy horticultural slow filters. Submitted manuscript. III. Bergstrand, K.-J., Khalil, S., Hultberg, M. & Alsanius, B.W. Cross response to dual pathogen bombardment in closed hydroponic growing systems. Manuscript
Place of Publication:Alnarp
Associated Programs and Other Stakeholders:Z - SLU - Library > Odla mera
ISBN for printed version:978-91-86197-10-0
Publication Type:Licentiate thesis
Full Text Status:Public
Agrovoc terms:hydroponics, electric conductivity, enzyme activity, fusarium oxysporum, pythium aphanidermatum, filters
Keywords:Electric conductivity, enzyme activity, Fusarium oxysporum f.sp. cyclaminis, hydroponics, polysaccharides, Pythium aphanidermatum, slow filter
Permanent URL:
ID Code:1952
Department:(LTJ, LTV) > Horticulture (until 121231)
Deposited By: Karl-Johan Bergstrand
Deposited On:04 Mar 2009 00:00
Metadata Last Modified:22 Mar 2015 15:12

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