Pure oxygen process aeration

The activated sludge process including multiple-stage, extended aeration, the Unox pure oxygen system, aerated ponds, and other variations. 

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. 

Table 11.2 provides a summary of the main features of aerobic and anaerobic wastewater treatment. Aerobic treatment processes are generally restricted to BOD < 1000 mg/liter unless pure oxygen is used for aeration. 

FIG. 22-41 Schematic diagrams of various modifications of the activated-sludge process, (a) Conventional activated sludge. (b) Step aeration, (c) Contact stabilization, (d) Complete mixing, (e) Pure oxygen, (f) Activated biofiltration (ABF), (g) Oxidation ditch. 

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. 

It is a consequence of the action of different pH values in the aeration cell that these cells do not arise in well-buffered media [4] and in fast-flowing waters [5-7]. The enforced uniform corrosion leads to the formation of homogeneous surface films in solutions containing Oj [7-9]. This process is encouraged by film-forming inhibitors (HCOj, phosphate, silicate, Ca and AP ) and disrupted by peptizing anions (CP, SO ") [10]. In pure salt water, no protective films are formed. In this case the corrosion rate is determined by oxygen diffusion [6,7,10]... 

As is the case with pure bubble columns and gas-operated loop reactors, most bioreactors in technical use are aerated with oxygen or air. Reactors with pure surface aeration, such as roller bottles, shake flasks and small stirred reactors or special reactors with membrane aeration, are exceptions. The latter are used for the cultivation of cells and organisms which are particularly sensitive to shearing (see e. g. [28 - 29]). The influence of gas bubbles in increasing stress has been described in many publications (see e.g. [4, 27, 29, 30]). In principle it can be caused by the following processes ... 

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