Nitrification in the Activated Sludge Process

Received in revised form The removal of total nitrogen (TN), i.e., ammonium, nitrate, and nitrite, is an increasingly important goal for municipal and industrial wastewater treatment plants. Practical and cost-effective technologies are needed, especially for older plants with limited space for expansion. TN removal typically be retained. Retention typically is achieved by operating at high solid retention times (SRTs), which may not be feasible for older activated sludge plants. Another approach is to add fixed or suspended biofilm attachment surfaces, which is the basis for the integrated fixed-film activated sludge (IFAS