ISHS Acta Horticulturae 481: International Symposium on Growing Media and Hydroponics
SLOW SAND FILTRATION: A POTENTIAL METHOD FOR THE ELIMINATION OF PATHOGENS AND NEMATODES IN RECIRCULATING NUTRIENT SOLUTIONS FROM GLASSHOUSE-GROWN CROPS |
| Authors: | E.A. van Os, J.J. Amsing, A.J. van Kuik, H. Willers |
| Keywords: | disinfection, soilless cultures, hydroponics, Phytophthora cinnamomi |
| Abstract:
In closed growing systems there is an enormous risk of spreading root pathogens around the nursery. Current disinfection techniques are high-tech and expensive. Slow sand filtration by comparison is a non-chemical, cheap, robust method. The objectives of the present trials with slow sand filtration were to investigate the requirements (filtration rate and grain size) and the working mechanism (elimination on a mechanical, physical or biological basis) for practical application in horticulture. In a glasshouse compartment, three sand types (coarse: 0.5–1.6 mm; middle: 0.2–0.8 mm and fine: 0.15–0.35 mm with an effective size of 0.71, 0.51 and 0.23 mm, respectively) and two filtration rates (0.1 and 0.3 m.h-1) were compared to investigate the performance of slow sand filtration in twelve, independent, systems growing tomatoes in rockwool. The working mechanism was studied by comparing sand with a low and with a high biological load in immature and mature filters by inoculating the filters with Phytophthora cinnamomi and detecting the presence of P. cinnamomi in the influent and effluent. The effectiveness of the filters was also tested by inoculating the nematode Radopholus similis and measuring its concentration in the influent and effluent. P. cinnamomi was eliminated completely at the 0.1 m.h-1 filtration rate using fine and middle sand. R. similis was eliminated partly and low concentrations of it were detected in the effluent for at least 21 days. The results of the mechanistic study showed that the elimination of P. cinnamomi was based mainly on physical factors, while biological factors have an additional effect. | |
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