Response analysis of a fluidized bed bio-reactor to substrate impulses

This study investigated the biodegradation feasibility of a fluidized bed bio-reactor responding to shock loadings of monoethylamine. The responses of immobilized cells cultivated in a steady-state continuous-flow, completely-mixed fluidized bed bio-reactor (FBBR) to a range of monoethylamine (C₂H₅HN₂, MEA) impulses are evaluated. Responses due to bacterial activities and physical flows are separately estimated using mass balance calculations. A simple methodology was developed for the analysis of responses of the immobilized cells cultivated in an FBBR. A series of experiments were carried out in anoxic FBBR using MEA as the sole substrate that served as a single carbon and nitrogen source.; Two distinctly different cell groups (i.e., a heterotrophic group responsible for carbon oxidation and an autotrophic group responsible for nitrification) mix-cultured under the long mean cell residence time conditions are able to carry out MEA-carbon oxidation by heterotrophic bacteria and releases ammonium ions that are nitrified to nitrate by autotrophic bacteria. As a result, the impulse responses could be characterized in terms of either substrate (C ₂H₅HN₂) utilization data or product (NO₃ −-N) formation data.; The experimental data show that the impulse response, in terms of combined total organic carbon (TOC) utilization and nitrification, spreads over a time period that includes an initial lag phase without bacterial activities, followed by a biodegradation phase that can be MEA-inhibited. The pattern of TOC utilization responses is similar to that according to Haldane kinetics, and MEA inhibition is evident at the loading >0.12 mg TOC/mg volatile solids (VSs). By comparison, nitrifying bacterial cells are more susceptible to MEA impulses than their heterotrophic counterparts, and nitrification activities are impeded at loadings as low as 0.03 mg TOC/mg VS. The ability of the FBBR to retain high immobilized biomass inventories is pivotal to its recovery from MEA impulses, in spite of the low cell activities resulted from the cultivation conditions adopted.