Simultaneous biodegradation of a two-phase fluid: Discolored biofilm issues

Three replicate aerobic-heterotrophic biotrickling filters were designed to promote the simultaneous biodegradation of graywater and a waste gas containing NH₃, H₂S and CO₂. Upon visual observation of discolored solids, it was originally hypothesized that gas-phase CO₂ concentrations were excessive, causing regions of anoxic zones to form within the biotrickling filters. Observed discolored (black) biofilm of this nature is typically assumed to be either lysed bacterial cells or anaerobic regions, implying alteration of operational conditions. Solid (biofilm) samples were collected in the presence and absence of gas-phase wastestream(s) to determine if the gas-phase contaminants were contributing to the solid-phase discoloration. Two sets of experiments (shaker flask and solids characterization) were conduced to determine the nature of the discolored solids. Results indicated that the discolored solids were neither anaerobic bacteria nor lysed cells. The solids were organic in nature and contain active aerobic-heterotrophic bacteria. Future work will attempt to characterize the discolored solid-phase more accurately.