JPH025478B

This invention relates to a process for the biological purification of wastewater in at least two immediately successive treatment stages, followed by a post clarification stage wherein the process is adapted so that a wastewater-activated sludge mixture in one of the treatment zones exhibits only a minor biological load and a nitrification process is conducted therein. In accordance with the invention, an intermediate clarification tank is not required due to substantially all biological degradation having occurred in the stage immediately before the nitrification stage. To enhance nitrification a macroporous carrier material for supporting nitrifying bacteria, for example, activated carbon or polyurethane foam, is added into this nitrification treatment stage. The material can be readily retained in the nitrification zone by providing appropriate retaining means. This process offers the advantage that the concentration of nitrifying agents, i.e., bacteria necessary for nitrification is maintained at the required level at all times. In another aspect, the invention relates to the apparatus for carrying out the process.