Degradation of Harmful Bacteria in Simulated Wastewater and Stormwater Runoff by the White Rot Fungus Pleurotus Ostreatus

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Microbial pollutants from non-point sources are a common problem in many watersheds all over the world. Current methods for dealing with these pollutants are limited and recent literature suggests that one of the most common solutions, vegetative or riparian buffers, while initially effective in removing harmful bacteria from runoff, have been found to accumulate coliform bacteria over time. Due to the fact that within those systems there is no intentional mode of bacterial degradation, over time these bacteria subsequently get released back into the environment. However, research in an unrelated field has shown that certain fungi such as Pleurotus ostreatus will actively seek out and degrade bacteria in situ. Capitalizing on that fact, the white rot fungus Pleurotus ostreatus was analyzed as a potential biocontrol agent used to reduce the amount of coliform bacteria in simulated wastewater and storm water runoff. On water agar plates, Pleurotus ostreatus was seen to actively search out bacterial colonies, invade them and consume them within 72 hours. Based on this principle, biocell reactors (BCR) were used to determine the effectiveness of spent mushroom compost (SMC) containing Pleurotus ostreatus to reduce the concentration of Escherichia coli in simulated wastewater and stormwater runoff. Loading was based on a 2” rainfall event over 24 hours at a fixed contamination level (bacterial concentration of 1 x 104 cells/mL). Overall E.coli concentrations in the effluent of the reactors containing live compost showed higher E.coli concentrations compared to the dead controls during the first 24 hours. After the first 12 hours however, the overall concentrations in the live reactors began to decrease while the concentration in the dead control began to increase. After allowing the reactors to rest for 24 hours and simulating a subsequent uncontaminated rain event, the E.coli concentration in the dead controls increased exponentially while the overall concentrations in the live reactors continued to decrease. The simulated wastewater effluent treatments, while having the lowest total concentration of E.coli, did not decrease over time. This suggests that the presence of the live fungus kills the adsorbed E.coli and that nutrient concentrations may play a significant role in the level of predation observed.
white rot fungus, Pleurotus ostreatus, coliform bacteria, simulated wastewater and storm water runoff, biocontrol agent