The role and control of sludge age in biological nutrient removal activated sludge systems

摘要

The sludge age is the most fundamental and important parameter in the design, operation andncontrol of biological nutrient removal (BNR) activated sludge (AS) systems. Generally, the betternthe effluent and waste sludge quality required from the system, the longer the sludge age, thenlarger the biological reactor and the more wastewater characteristics need to be known.nControlling the reactor concentration does not control sludge age, only the mass of sludge in thensystem. When nitrification is a requirement, sludge age control becomes a requirement and thensecondary settling tanks can no longer serve the dual purpose of clarifier and waste activatednsludge thickeners. The easiest and most practical way to control sludge age is with hydraulicncontrol by wasting a defined proportion of the reactor volume daily. In AS plants with reactornconcentration control, nitrification fails first. With hydraulic control of sludge age, nitrification willnnot fail, rather the plant fails by shedding solids over the secondary settling tank effluent weirs.