Chromium (VI) inhibition in multi-substrate carbon oxidation and nitrification process in an upflow packed bed biofilm reactor

The performance of an upflow packed bed biofilm reactor has been analyzed mathematically under multi-substrate limitation of carbon oxidation and nitrification reactions while subjected to inhibition of a continuous dose of Cr(VI). For a fixed inlet concentration of 150 mg 1^-1 of NH₄⁺-N and 250 mg 1^-1 of acetate and varying the inlet concentrations of Cr(VI), the results show that the toxicity of Cr(VI) to both organic oxidation and nitrification processes increases rapidly with increase in its inlet concentration. The toxicity of Cr(VI) has been found to be much pronounced when nitrification alone is considered to take place in the reactor. The concentration profiles within the biofilm show that oxygen is a limiting component near the inlet and at the middle of the reactor. This necessitates the need for ample supply of oxygen at these locations within the reactor as major portion of oxidation of both acetate and NH₄⁺-N takes place there. The model predictions show a close agreement with the available experimental data for a variety of operating conditions.