Biofiltration

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Biofiltration aims to treat drain water against pathogens, allowing recirculation into the crop. The filter is filled with an inert and porous support (in general pozzolana) and drainage water to treat (=‘static biofiltration’). The biofilm which develops naturally on the pozzolana should consist of Pseudomonas and Bacillus bacteria. To accelerate the germicidal efficacy of the filter, the tank can be seeded with a selected biofilm. The aim of the process is to create a balance between beneficial microorganisms and pathogens. To enhance the efficacy of the biofiltration, an air circulation is set up in the tank (=‘dynamic biofiltration’). To reach an optimal efficiency, the flow should be slow: 100 to 350 L m-2 of filtering surface/hour, depending on whether the biofilter is oxygenated or not (e.g. for a flow of 4.5 m³ h-1, the biofilters could have a diameter of 4 m). In all, there is little influence on the treated solution in terms of pH, temperature and nutrient composition. Efficacy of biofiltration has been proven on pathogens fungi but the efficacy is lower on bacteria and viruses.
The dimensioning of a dynamic biofilter and a cost estimation of biofiltration technology can be found below.
Additional costs include buying appropriate UV-resistant tanks.
Proper maintenance guidelines:
• The biofilter must be installed in a temperate and protected area (optimal temperature = 15-25 °C) and covered with a black tarpaulin cover to avoid algae development.
• Pesticide residues or chemical disinfection of drain water must be absent to protect the activity of the biofilter.
• The level of water must be kept above the pozzolana.
• Air circulation must be regular, as should be the flow of the injection pump of non-disinfected drain water.
• In static filtration, regular cleaning by back flush is needed.
• Between seasons, the biofilter must function a couple of hours per day to maintain biological activity.

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Biofiltration (summary) 195.05 KB 15 downloads

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Biofiltratie 195.64 KB 7 downloads

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Extended article

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Biofiltration disinfection 512.83 KB 15 downloads

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Elise Vandewoestijne

Provinciaal Proefcentrum voor de Groenteteelt (PCG), Belgium
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