Slow sand filters: a biological treatment method to remove plant pathogens from nursery runoff^©

Slow sand filters (SSF) are an effective technology, capable of developing high-quality water from untreated sources including irrigation runoff. The sand serves as a substrate on which a microorganism community grows. This microbial community can breakdown a wide range of pollutants including plant pathogens. This report reviews results on the removal of Phytophthora spp., Fusarium oxysporum, and tobacco mosaic virus. We were interested in the capacity of these filters to remove different kinds of plant pathogens from captured irrigation run off. Our experiments removed P. capsici after the microbial community was established (2 weeks) and after a simulated 7-day pump failure in previously established SSFs. However, SSFs did not remove F. oxysporum after 7 weeks. In our tests, the SSFs were also able to remove tobacco mosaic virus from inoculated runoff water after 6 to 9 weeks of exposure.