| The ability of earthworms to facilitate destruction of pathogens--as indicated by fecal coliforms--was investigated. In particular, their ability to meet 40CFR Part 503 regulations for a Process to Further Reduce Pathogens (PFRP) by reducing the most probable number (MPN) of fecal coliforms to below 1000 MPN/g dry weight, was investigated. Vermicastings derived from waste-activated sludge (WAS) were placed in containers with populations of earthworms. Three earthworm species--Eisenia fetida, Eisenia hortensis, and Pheretima hawayana--were used in all possible combinations in an effort to determine if a certain species or combination of species was superior in terms of coliform reduction. Earthworm densities were quantified at the completion of the experiment by assessing changes in their numbers and gross weight.; There was a noticeable difference among treatment runs, but no difference was observed among species or combinations of species. Regardless of treatment, samples were observed to achieve USEPA requirements for PFRP by reducing coliform populations to less than 1000 MPN/g, dry weight. The overall health of earthworm populations was observed to decline over the course of the experiment. It is believed that this decline in population density was a result oF declining food sources for earthworms within each container. |
