Abstract
Use of the trickling filter is advantageous in the nitrification process as no mechanical aeration is required. Since all reactions are initiated on the wetted surface, as a consequence of linear velocity (LV), mass transfer through the surface area of the liquid film into the biofilm dictates the process performance. The relationship among LV, dissolved oxygen (DO) and reaction rate was obtained in a 24-L tower of 2.7 m height continuously fed with synthetic wastewater containing ammonia with the bulk pH maintained at 7.0 and air supplied at 20 L/min. By increasing the LV from 4 to 100 m/d the nitrogen oxidation rate (NOR) increased from 1.2 to 3.0 g-O2/L/d and the DO decreased from 8.5 to 4.5 mg-O2/L. When LV exceeded 100 m/d, the NOR was apparently at a maximum value of 3.0 g-O2/L/d and the DO recovered to 6.5 mg-O2/L. This response was used to construct a mathematical model where the kinetics of the biofilm were extracted based on measured parameters. The model can be used as a basis for scaling up the design of trickling filters for actual applications. Additionally, the energy consumption at the maximum NOR was estimated to be 53.1% to 87.3% less than that in the conventional activated sludge process.
