Nitrate removal and kinetic model of saline water by sulfur-based autotrophic denitrification

The investigation of nitrate removal in recirculating aquaculture system as a purpose, autotrophic denitrification of nitrate removal and kinetic characteristics for saline synthetic wastewater were carried out in a sulfur packed-bed reactor. The experimental results show that nitrate is effectively removed when the influent NO₃^--N concentration is in the range of 22.5～368 mg/L. The optimal influent loading rate in order to ensure that the removal efficiency of nitrate was higher than 95% and nitrite accumulation occurred in effluent below 1 mg/L was in the range of 0.052～1.088 kg/(m³·d) when the water temperature was (29±1)℃. The maximum nitrate volumetric removal rate of 1.65 kg/(m³·d) was achieved at an influent loading rate of 2.171 kg/(m³·d) with obvious nitrite accumulation in effluent reaching 28.69 mg/L. The kinetic experimental results show that the NO₃^--N removal rate in the reactor can be described by a half-order kinetic model for biofilms. It has been found that the half-order reaction rate constant per unit reactor volume K1/2v is 7.84～8.5 mg1/2/(L1/2·h) and it can be successfully applied in the kinetic model for the prediction of effluent NO₃^--N concentration. The two groups’ predictive values and actual values were analyzed by using SAS 8.0 software for ANOVA analysis. The ANOVA analysis indicates that the corresponding Pr＞F values are 0.9732 and 0.8845, which proved that no significant differences exist between the predictive values and actual values of the model.