DISINFECTION OF RECIRCULATING NUTRIENT SOLUTIONS BY SLOW SAND FILTRATION

In two experiments the efficacy of slow sand filtration against Fusarium oxysporum f.sp. cyclaminis was proved on small pilot filter devices.
The filter containers consisted of plastic pipes with a length of 217 cm and an effective filter surface of 279 cm². The filtration rate was 200 1/m²h.
The filter bed was biologically activated by recirculating the nutrient solutions from NFT cultures of geraniums.

The results of this study show that only a very small amount of the microconidia of F. oxysporum f.sp. cyclaminis could pass through the filter bed.
Immediately after inoculation the mean population density of the pathogen in the supernatant water layer was 79100 cfu/ml in experiment 1 and 86290 cfu/ml in experiment 2. The highest average concentration in the filtrate was 75 cfu/ml 4 hours after inoculation in experiment 1 and 88 cfu/ml 3 hours after inoculation in experiment 2. Concentrations of nutrients, pH- and EC-values of the nutrient solutions were not significantly affected by slow sand filtration.
However, the oxygen content decreased to zero in experiment 1 and to 1.6 % saturation in experiment 2.

IV International Symposium on Soil and Substrate Infestation and Disinfestation

W. Wohanka

https://doi.org/10.17660/ActaHortic.1995.382.28