High loading denitrification by biological activated carbon process

High loading denitrification was studied using granular activated carbon (Calgon Filtrasorb 400, size: 0.8–1.4 mm) column with injecting carbon source (sucrose) only once a day. Under the condition of EBCT (empty bed contact time) = 80 min, C:N RATIO = 1.88, once per day injection mode of organic supply was able to sustain an average denitrification efficiency of 84 to 89% even with influent NO3---N concentration of 80 mgl−1. With an influent NO3---N of 20 mgl−1 and C:N ratio of 1.88, however, reduction of EBCT to 20 min resulted in very poor denitrification. In the latter case, 46% of the added carbon was lost in the effluent immediately after the injection. Short EBCT critically affected the process mainly due to insufficient adsorption rate. Microbial denitrification capability and fermentation might also limit the process. Extended organic injection is a possible option to improve the process efficiency. Occurrence of the sulfate reduction was limited in early phase of the cycle.