Eliminatie van stikstof uit afvalwater door denitrificatie

A study was made on the use of denitrification to improve the conventional purification of sewage. Denitrification, the elimination of nitrogen, saves oxygen needed for elimination of organic compounds. The kinetics was studied of the activated sludge with either nitrate or oxygen as electron acceptor. The overall rate of substrate removal was almost the same in both systems. The gross sludge yield with nitrate seems to be somewhat more than with oxygen. A one-sludge system with intermittent denitrification was studied on laboratoryscale and in a pilot plant. A high rate of removal of nitrogen was attainable with that system, if in the unaerated phase of the cycle all the sewage flowed into the reactor. In the study with a two-sludge system with preliminary denitrification, an upflow reactor without carrier material was used for denitrification. A model is presented to calculate the mass concentration of nitrate and of chemical oxygen demand in the effluent of the nitrification and denitrification reactor. In several circumstances, part of the sewage should flow directly into the nitrification reactor. This can be calculated with the model, if certain characteristics of the particular sewage are measured. A study was made of the use of an upflow reactor for purification of sewage with added nitrate in an upflow reactor. A high mass concentration of suspended solids (30/g/l) could be maintained. The removal of chemical oxygen demand was about 70% with a sludge load (Δ mCOD / mB,COD Δ t ) of 0,18 g/g d.