1.
Inhibition kinetics of nitritation and half-nitritation of old landfill leachate in a membrane bioreactor.
Li, Y, Wang, Z, Li, J, Wei, J, Zhang, Y, Zhao, B
Journal of bioscience and bioengineering. 2017;(4):482-488
Abstract
Nitritation can be used as a pretreatment for anaerobic ammonia oxidation (anammox). Various control strategies for nitritation and half-nitritation of old landfill leachate in a membrane bioreactor were investigated in this study and the inhibition kinetics of substrate, product and old landfill leachate on nitritation were analyzed via batch tests. The results demonstrated that old landfill leachate nitritation in the membrane bioreactor can be achieved by adjusting the influent loading and dissolved oxygen (DO). From days 105-126 of the observation period, the average effluent concentration was 871.3 mg/L and the accumulation rate of [Formula: see text] was 97.2%. Half-nitritation was realized quickly by adjusting hydraulic retention time and DO. A low-DO control strategy appeared to best facilitate long-term and stable operation. Nitritation inhibition kinetic experiments showed that the inhibition of old landfill leachate was stronger than that of the substrate [Formula: see text] or product [Formula: see text] . The ammonia oxidation rate dropped by 22.2% when the concentration of old landfill leachate (calculated in chemical oxygen demand) was 1600.2 mg/L; further, when only free ammonia or free nitrous acid were used as a single inhibition factor, the ammonia oxidation rate dropped by 4.7-6.5% or 14.5-15.9%, respectively. Haldane, Aiba, and a revised inhibition kinetic model were adopted to separately fit the experimental data. The R2 correlation coefficient values for these three models were 0.982, 0.996, and 0.992, respectively.
2.
[Effect of nitrite accumulation on enhanced biological phosphorus removal (EBPR) in A2O process treating domestic wastewater].
Zeng, W, Li, L, Yang, YY, Zhang, Y, Peng, YZ
Huan jing ke xue= Huanjing kexue. 2010;(9):2105-12
Abstract
At normal temperature, short-cut nitrification and denitrification was achieved in a lab-scale A2O process treating low C/N ratio domestic wastewater by controlling DO concentration of 0.3-0.5 mg/L and increasing the internal reflux ratio to decrease the actual aerobic HRT. However, the phosphorus removal in A2O process was deteriorated with the increasing of the nitrite concentration in the effluent. The factors causing phosphorus removal deterioration, such as the influent COD concentrations, temperature, pH and free nitrous acid (FNA) were systematically analyzed. Experimental results showed that the nitrite accumulation resulting from short-cut nitrification affected anaerobic P release and aerobic P uptake. Especially, the higher FNA concentration (HNO2-N 0.002-0.003 mg/L) in the aerobic zone significantly inhibited the aerobic P uptake, which was the major reason causing P removal deterioration. Through adding the carbon sources in influent to enhance anaerobic P release and denitrification, the nitrite and FNA concentrations in the aerobic zone were decreased, and the P removal was recovered. More than 96% of PO4(3-) -P could be removed in A2O process.