SWEDEN
In this study, the denitrification capacity of a continuous influent feed sequencing batch reactor (SBR) was measured and evaluated trough tests at a pilot plant situated in Nacka, Sweden. The reactor’s capacity for total nitrogen removal was determined for three cycle structures with allocated anoxic treatment time during the react phase of 0, 2 and 4 hours per day. In the study, the batch reactor showed a significant capacity for denitrification even with no anoxic phases added into the react phase. Without anoxic treatment phases, an average of 53 % of the influent nitrogen was denitrified. When adding 2 and 4 hours of anoxic treatment time per day, this number was increased to 65 % and 66 %, respectively. Denitrification was found to occur during the settling phase of the treatment cycle. This was possible thanks to the continuous influent feed, which ensured that sufficient carbon for denitrification was available in the settled sludge, as well as the use of proper DO control, which enabled anoxic conditions during the settling phase. Under these conditions, the denitrification capacity offers the potential to reduce the length of allocated anoxic periods in continuous feed SBRs while still meeting required total nitrogen permits. Standard design procedures indicate that the reduction in required anoxic periods can decrease the total life cycle cost of a continuous feed SBR system with up to 15 % and the required footprint per treatment capacity with 15 %.
