Step aeration

FIG. 25-54 Schematic diagrams of various modifications of the activated-sludge process, a) Conventional activated sludge. (h) Step aeration, (c) Contact stabilization, (d) Complete mixing, (e) Pure o gen. (f ) Activated hiofiltration (ABF), (g) Oxidation ditch. 

Tapered and Step Aeration. In New York City, plants scattered throughout the five boroughs are treating more than 3.8 x 10 (10 gal)... 

The first suspended growth process, now called the conventional activated sludge process, was developed to achieve carbonaceous BOD removal. However, since its inception, many modifications to the basic process have taken place. The variations in the activated sludge process are too numerous to be discussed in detail here. However, some of these are step aeration, contact stabilization, aerated lagoon, deep-tank aeration, and pure oxygen aeration. 

Step Aeration In this process, the influent feed is introduced into the plug-flow reactor at two or more... 

Many modifications for the conventional process have been proposed for improving the system or for treating a specific type of wastewater. These modified processes are extended aeration, contact stabilization, step aeration, tapered aeration, high rate, and pure oxygen process. 

Different types of activated sludge systems are used in treating pharmaceutical waste water. Some sludge systems include conventional, complete mix, contact stabilization, extended aeration, and step aeration. 

Step aeration, modified aeration PFTR activated sludge higher strength domestic waste water, 85-95% removal. 

Step aeration, modified aeration PFTR activated sludge mean cell residence time = 5-15 d food/microorganism ratio = 2.3-4.6 mg BOD5/S kg MLVSS volumetric loading = 0.6-1 kg BODj/m MLSS = 2-3.5 g/L residence time = 3-5 h recycle ratio = 0.25-0.75. Air requirements = 100 m /kg of input BOD5. 

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