Effects of C/N Ratio and DO concentration on Carbon and Nitrogen removals in a Hybrid Biological Reactor

Abstract

The objective of this paper was to evaluate the effects of dissolved oxygen (DO) concentration and C/N ratio on the biological removal of carbon and nitrogen using an Integrated Fixed-film Activated Sludge (IFAS) reactor for nearly half a year. The results showed that the efficiency of organic matter removal was greater than 90% regardless of the value of the C/N ratio. Nitrogen removal was affected by the C/N ratio. Indeed, at a C/N ratio equal to 10, nitrogen removal efficiency was maximum with an average removal of 96.54%, 86.1% for ammonium and total nitrogen, respectively. Conversely, with a C/N ratio of 4, removal rate dropped significantly. Indeed, the average ammonium and total nitrogen removal were of 82% and 53%, respectively. An important nitrogen removal rate was achieved when the operating DO concentration was maintained between 1.0 and 2.0 mg L-1. The impact of the packing material and Mixed Liquor Suspended Solid (MLSS) concentrations on oxygen transfer was determined experimentally. In fact, up to 23% increase in the values of the mass transfer coefficient was observed after the addition of a packing material inside the reactor. However, an increase in the MLSS led to a decrease of the oxygen transfer coefficient.