Nitrite accumulation during wastewater denitrification

Characteristics and mechanisms of nitrite accumulation during wastewater denitrification were reviewed based on our experimental results and literatures reports. Nitrite accumulation may be caused by the rate difference between nitrate reduction and nitrite reduction. It can also is the results of some species of bacteria or enzymes absence in the denitrification sludge. Although literature reports were inconsistency, temperature, dissolved oxygen, pH, types of carbon source and C/N ratios are the main environmental factors that have a big influence on nitrite accumulation. Nitrite is detrimental to aquatic organism if the wastewater containing enough nitrite was discharged to waters or can be a big problem for activated sludge process operation. Nitrite accumulated in denitrification may serve as electron donor for anammox reaction and the demonstration tests are undergoing in our lab.