Investigation Of Inhibition Phenomena In Nitrite Oxidation

Nitrification is an effective technology to control nitrogen pollution from wastewater. How to control the process factors and acquire the accumulation of NO₂^- during the nitrification process is vital for high efficient short-cut nitrification and denitrification over nitrite. These factors include substrate, toxic substance, disinfectant, pH, alkalinity, dissolved oxygen, temperature, sludge retention time and etc. There are two ways to obtain the accumulation of nitrite: One is to wash out the nitrite oxidation bacteria utilizing the difference between ammonia oxidation bacteria and nitrite oxidation bacteria at suitable temperature. The other is inhibit nitrite oxidation process utilizing the inhibition or limitation factors in nitrification. The substrate inhibition is main inhibition phenomenon. This thesis focuses on the substrate (nitrite) inhibition at pure nitrite substrate without ammonia, using a SBR reactor. Main research's result as follows:1. When the DO is controlled in the 5-6 mg/L, temperature at 25±2℃. The reaction rate was linearly related to the concentrations of nitrite or free nitrous acid(FNA) when there is no inhibition to the nitrite oxidation bacteria. The nitrite oxidation bacteria were inhibited, and can be recovered, when concentrations of nitrous acid were larger than about 0.1 mg/L and smaller than 0.33 mg/L. The reaction rates varied with the characteristic of multiple values, multiple status, chaotic oscillation as the consequences of the inhibition, when concentrations of FNA were larger than about 0.38 mg/L.2. When temperature at room-temperature 20℃-29℃, the DO is controlled in the 5-6 mg/L, The reaction rate was linearly related to the concentrations of nitrite or free nitrous acid when there is no inhibition to the nitrite oxidation bacteria. The nitrite oxidation bacteria were inhibited when concentrations of nitrous acid were 0.20mg/L. The reaction rates varied with the characteristic of multiple values, multiple status, chaotic oscillation as the consequences of the inhibition when concentrations of FNA were larger than about 0. 8 mg/L.3. The inhibition kinetics of nitrite oxidation is keeping with Haldane kinetics respectively concerning nitrite-nitrogen and free nitrous acid concentrations.4. The chaotic oscillations have been observed in nitrite oxidation. The nitrite oxidation rate present characteristics of sensitive dependence to the initial value and present aperiodic oscillations.