MODELING OF DEGRADATION OF SOLUTIONS CONTAINING NITROGEN AND CARBON-COMPOUNDS IN AERATED SUBMERGED FIXED-FILM (ASFF) BIOREACTORS

The biodegradation reaction rates of waste-water solutions containing nitrogen and carbon compounds were studied in an aerated submerged fix ed film (ASFF) reactor with four compartments. A solution containing s ucrose (carbon source) and ammonium chloride (nitrogen source) was con sidered in this study. The kinetic models considered in the analysis w ere the variable order model and the Monod model. Measurements and ana lysis were performed as a function of organic and hydraulic loading fo r the reactor. Analysis of the kinetic data was carried out in the fir st compartment and in the combined section of the reactor which includ ed the second, third, and fourth compartments. The reaction order for carbon removal in the first compartment was found to vary over a range of 1-2 and drops to a range of 0.7-1.2 in the combined section. Lower reaction orders were obtained for nitrogen removal which varied from 0.6-1 in the first compartment and the combined section. Upon applicat ion of the Monod model for the two reactions, similar trends to those of the variable order model were obtained for carbon and nitrogen remo val in both sections of the reactor. The calculated Monod constants fo r carbon removal were one to two orders of magnitudes larger than thos e for nitrogen removal. Measured removal rates of carbon in the first compartment were two orders of magnitudes higher than the nitrogen rem oval rates in the same compartment. However, the removal rates of both components are comparable in the combined section, especially at high feed flow rates. This behaviour was consistent with literature data o n simultaneous removal of carbon and nitrogen compounds, where high co ncentrations of carbon resulted in severe reduction in the removal rat es of nitrogen compounds.