Biological treatment of waste semi-synthetic metalworking fluid using a fluidized-bed bioreactor

fluidized bed bioreactor (FBB) was studied to treat wastewater originating from the aqueous phase of metalworking fluids (MWFs). This wastewater had high levels of chemical oxygen demand (COD) and biochemical oxygen demand (BOD) owing to water soluble organic compounds in semi-synthetic MWFs. The goals of the research were two-fold: first, to establish an operable aerobic FBB to treat semi-synthetic metalworking fluid wastewater, and second, to characterize the bioreactor to better control and predict its performance.;To establish an operable FBB, a recipe for simulated semi-synthetic MWF wastewater was developed that allowed a microbial population to develop in the FBB and degrade the water soluble organic compounds. Once a microbial population was established, controlling biofilm thickness on fluidized sand particles was crucial to stabilizing the FBB bed and producing effluent of relatively consistent quality. Effluent COD and BOD;The FBB was characterized by analyzing substrate uptake rates. Biofilm-coated sand particles were found to stratify in the fluidized bed in such a way that the particles with thicker biofilm coatings segregated toward the top of the bed. Sand particles with thick biofilm (thickness...