C:N Ratio Effect on Trichoderma Growth and its Ability to Suppress Fecal Coliform in Biosolids

Production of high quality biosolids can promote the acceptance of biosolids land application. Trichoderma spp. are a group of soil fungi that are known to attack several soil plant pathogens as well as inducing host plants' defense system and growth promotion. The goal of this research was to determine an optimum C:N ratio in biosolids to promote growth of Trichoderma. A secondary goal was to also observe any effects that an increased C:N ratio and the presence of Trichoderma may have on fecal coliforms in biosolids. The results showed that carbon addition to biosolids lengthens the regrowth period for fecal coliforms. Yet at a high enough carbon concentration, fecal coliform density is reduced. Carbon addition also encourages fungal growth; although, the dominant fungal colonies were not Trichoderma. However, bioassay results showed that biosolids alone, without the addition of a carbon source were capable of suppressing Pythium attack on creeping bengrass.