Kinetics of cross-inhibited denitrification of a high load wastewater

Batch denitrification of a synthetic saline medium at 37 °C, pH 7.5 was studied. A kinetic expression and an inhibition function which adequately expresses inhibition and cross-inhibition by nitrate and nitrite in denitratation and denitritation steps occurring in high organic and nitrate load wastewater treatment was determined. Denitratation and denitritation rates were measured independently. Monod- and Haldane-type kinetics were used for denitratation and denitritation, respectively. The maximum specific rate, kNO3=12.7 mg NO3-N/g VSS hkNO3=12.7 mg NO3-N/g VSS h, and the saturation constant, KSNO3=0.47 mg NO3-N/LKSNO3=0.47 mg NO3-N/L were calculated for denitratation. The maximum specific rate, kNO2=13.8 mg NO2-N/g VSS hkNO2=13.8 mg NO2-N/g VSS h, the saturation constant KSNO2=0.36 mg NO2-N/LKSNO2=0.36 mg NO2-N/L and the inhibition constant KI-NO2=906 mg NO2-N/LKI-NO2=906 mg NO2-N/L were calculated for denitritation. Among other functional forms the Levenspiel inhibition model for denitratation and denitritation kinetics was proposed. The Levenspiel constants were SNO2-M=1149.4 mg NO2-N/LSNO2-M=1149.4 mg NO2-N/L, SNO3-M=34.7 mg NO3-N/LSNO3-M=34.7 mg NO3-N/L, β1 = 1.578 and β2 = 1.005, respectively. The fitted experimental values show a good representation of the denitrification of effluents with high nitrogen load containing both nitrate and nitrite. Parametric sensitivity analysis show that inhibition functions (fi) and dimensionless constants (βi) greatly affect predicted nitrite and nitrate consumption rates.