METHOD FOR BIOLOGICAL PURIFICATION OF WASTE WATER

摘要

In a system for biological purification of waste water, the liquid flow from an oxygen addition stage is fed with a low sludge concentration to a sludge thickening zone within a separation unit, the flow in said zone being divided into a sludge phase with a high dry substance concentration of at least 2% and a liquid phase substantially free from sludge. At least part of the sludge phase is returned to the oxygen addition stage, and the liquid phase is fed to a clarification stage where sludge residue is removed from the liquid phase.