TWO-STEP BIOLOGICAL TREATING METHOD OF SEWAGE, PARTICULARLY,URBAN SEWAGE

摘要

Process for the two-stage biological treatment of effluent, in particular municipal effluent, in a treatment plant having an activation tank for the first biological stage which is operated at a sludge load of greater than 2 kg of BOD5 per kilogram of dry matter and day, a secondary clarification tank connected downstream of the activation tank, from which secondary clarification tank excess sludge is withdrawn at a rate such that the sludge in the activation tank is kept in the initial phase in which substrate respiration is initiated and having a second aerobic biological stage to which the water flowing from the secondary clarification is fed. The activation tank is operated with a through-flow time of less than or equal to 45 minutes. 0.5 to 1.5 % by weight of the activated sludge being processed per cubic metre are fed from the activation tank via the secondary clarification into the second biological stage. A filter bed having an upper biologically active porous filter layer and a lower sand layer is used for the second biological stage, that is with the conditions that some of the water discharging from the filter bed is recycled, that an actual filter rate, including the returned portion, in the range 5 m/h to 20 m/h is employed, that a space load of 6 to 18 kg of BOD5 per cubic metre and day in the filter bed is employed and that the biologically active, porous filter layer [lacuna] a layer thickness of 100 cm, which ... Original abstract incomplete. IMAGE