OPTIMIZATION OF SLOW FILTRATION AS A MEANS FOR DISINFECTING NUTRIENT SOLUTIONS

Trials were conducted to optimize slow sand filtration by varying filter material, depth of the filter bed and flow rate.
Recirculated nutrient solutions from Dracaena marginata and Aglaonema commutatum pot plants grown hydroponically in expanded clay on ebb/flow benches were inoculated with Xanthomonas campestris pv. pelargonii as the test organism.
Four completely separated systems were used each consisting of one hydroculture bench (approx. 3 m²) and one filter unit (approx. 0.2 m² filter surface).

Granulated rockwool in comparison to sand, pumice or anthracite has been shown to be the most efficient filter material.
The efficiency of a rockwool filter with a depth of 90 cm was only slightly and not significantly higher than that of a 60 cm filter.
However, both efficiency rates were significantly higher than that of a 30 cm filter.
The differences of the mean efficiency rates at flow rates of 100, 200 and 300 L/m²h were not as high as expected (99.76, 99.41 and 98.85 % respectively). A regression analysis revealed a significant correlation of -0.5 between flow rate and efficiency rate.

International Symposium on Growing Media and Hydroponics

W. Wohanka, H. Luedtke, H. Ahlers, M. Luebke

https://doi.org/10.17660/ActaHortic.1999.481.63