Denitrification at low temperatures using a suspended carrier biofilm process

The denitrification process was studied in a stirred lab-scale suspended carrier biofilm reactor at low temperatures (3–20°C). The reactor was filled to 50% with Kaldnes K1 carriers. The denitrification rate showed only a rather weak dependence on the temperature, the rate at 3°C being approximately 55% of that at 15°C. The maximum denitrification rate obtained at 15°C was 2.7 g NOx-N m2 carrier d1. The maximum denitrification rate at 3°C during an 8-day period was found to be constant. During the 8 days, the hydraulic retention time was approximately 1.5 h and the inlet NO3-N concentration was 30 mg l1.