Partial denitrification coupled with immobilization of anammox in a continuous upflow reactor

Based on the stable operation of a continuous upflow reactor, immobilized anammox coupling with partial denitrification (DEAMOX), was successfully achieved after 94 days operation with a 63.5% accumulation rate of NO₂ ^--N and a 98.4% removal rate of NO₃ ^--N. Moreover, the findings show that the optimum range of COD/NO₃ ^--N ratio for the coupling reaction was 2.3-2.7. The nitrogen removal performance of the coupling reactor decreased in response to the increase of pH value to 8.0 or 8.5, which was inconsistent with previously published results. Complete denitrification was successfully coupled with DEAMOX by adding polycaprolactone (PCL) as solid carbon source. As a result, the NO₃ ^--N produced via anaerobic ammonium oxidation could be completely removed; the removal rate of total nitrogen increased from 80.3% to 88.5%. In addition, a large number of denitrifying biofilms were attached to the surface of PCL particles.