2012 Annual Report
This year, the project has completed two experiments and progress is being made on completing a third. First, an experiment was conducted to determine the ability of slow sand filters (SSFs) to remove a plant pathogen after being established to remove a different plant pathogen; second, an experiment was conducted to investigate the effect of a pump failure on SSFs’ removal efficacy; third, analysis of the biofilm inside the sand filters from the previous two experiments will be analyzed by DNA sequencing.
In the adaptation experiment, SSFs were first challenged with one pathogen (Phytopthora capsici or Fusarium oxysporum f. sp. Lycopersici) added to the leachate from containerized plants daily for six weeks; removal efficacy was measured weekly during this time. After this period, the pathogen inoculum was switched; SSFs that had been fed P. capsici-inoculated leachate was challenged with F. oxysporum f. sp. lycoperisici and SSFs that had been fed F. oxysporum f. sp. lycopersici were challenged with P. capsici. The removal efficacy after the switch was monitored weekly. The F. oxysporum CFU data are still being scored and collected.
The pump failure experiment used the established SSFs from the adaptation experiment. After the adaptation experiment was completed, the pumps supplying the SSFs with water were switched off, simulating a pump failure. The pumps were switched on one week later and the SSFs were inoculated with pathogens daily for an additional six weeks. The removal efficacy was recorded weekly.
DNA has been extracted from samples of the sand inside the SSFs. The DNA samples will be submitted to the Genome Center at the University of California, Davis for DNA sequencing.