If sludge is not wasted, the secondary clarifier eventually fills up with solids. Wasting removes solids buildup in the activated-sludge system, formed when solids amounts in the aeration-tank influent are greater than the solids amounts in the secondary-clarifier effluent. Sludge wasting rates affect the following: Sludge wasting is also important to activated-sludge process control. As BOD concentration entering the aeration basin rises, the amount of oxygen required to maintain dissolved oxygen levels rises also.Īnother factor is how much aeration you need to maintain a given dissolved-oxygen level that is directly proportional to the aeration-basin bacteria amounts. In controlling aeration, consider that the aerated oxygen required is based on the direct relationship between the influent bio-chemical oxygen demand (BOD) concentration and the aeration basin dissolved oxygen.
By balancing aeration rates, dissolved-oxygen levels can be maintained throughout treatment.Ī properly maintained diffuser can also improve aeration efficiency. In a mechanically aerated system, consider the number and location of mechanical aerators. In a diffused air system, aeration balance simply means looking at the basin’s dissolved-oxygen profile and adjusting the air-flow rates. Factors must be considered, for example, as the influence of dissolved-oxygen levels in the aeration basin. It involves, however, more than measuring aeration-basin dissolved oxygen (DO) concentration once each day. To control activated sludge, you need to "have a handle" either on aeration, sludge-wasting or return-sludge flow.Īeration-rate adjustment is probably the simplest way to go. The idea in controlling activated sludge is to keep the wastewater biomass-to-food ratio in balance. As a sewage and industrial wastewater treatment, it makes use of air and a biological floc composed of bacteria and protozoa.
Activated sludge isn’t a thing, it’s a process.
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