Process for biological purification of waste water

摘要

In a method of biological purification of waste water by aerobic, anaerobic or anoxic processes, the waste water is treated biologically in a reactor vessel (10) and then passes to an external membrane stage (20) which retains the suspended biological material for concn. and return to the vessel. The waste water flows through the membrane stage in a vertical direction, impelled by gas from a source (28), and is withdrawn in a plane below the waste water level in the reactor vessel by means of reduced pressure. The concentrate is returned to the reactor vessel by pressure of the gas. Also claimed is an appts. for carrying out the process with membrane stage having membranes through which flow takes place vertically.