Single-disc investigations on nitrogen removal of higher loads in sequencing batch and continuously operated RDR systems

Nitrification of ammonium-rich synthetic wastewater was studied in a contin uously operated rotating disc reactor (RDR) with additional aeration. For a wastewater with 500 mg L-1 NH4-N a nearly complete oxidation to nitrate co uld be demonstrated for a hydraulic residence time of 27 h (HRT). The react or was nearly completely mixed. Nevertheless, the biofilm covering the firs t discs was remarkably thicker than that of the last discs. In order to stu dy the bioactivity of selected discs, single-disc reactors were used. The d etermined ammonium oxidation rate was nearly independent of the thickness a nd location of the disc. In contrast, the nitrite oxidation rate increased from the first to the last discs. Some results from experiments on nitrogen removal in sequencing batch single-disc reactors (SBSDR) are discussed. Th e SBSDR was operated with 2 phases, a partially submerged phase for nitrifi cation and a completely submerged anoxic phase in which acetate was added f or denitrification. It was advantageous to operate without additional aerat ion and thus produce more nitrite and saving carbon and energy. First resul ts of the treatment of a synthetic wastewater with a C:N ratio of 1 in a 5- phase SBBR process providing 2 nitrification, 2 anoxic and a final aerobic post-treatment phase showed average specific rates.