As mentioned before, specification of aeration equipment requires the determination of SOR. From Equation (9.13), this involves finding the values of the aeration parameters AOR, ¡3, and a. The parameter a, in turn, requires the determination of the KLa values. Each wastewater is unique in its characteristics, so these parameters should be determined experimentally. The literature reports values of (KLa)w20 in the neighborhood of 2.5 per hour, a in the range of 0.7 to 0.9, and ¡3 in the range of 0.9 to 1.0. AOR in the neighborhood of 1.40 kg/m3 • day has also been obtained. The determination of these parameters will addressed in the succeeding discussions.
Example 9.1 The value of (KLa)w,20 for a certain industrial waste is 2.46 per hour. What is the value of (KLa)w at 25°C?
(KLa )w ,25 = 2.46 (1.024)25-20 = 2.77 per hour Ans
Example 9.2 A chemical engineer proposes to purchase an aerator for an activated sludge reactor. In order to do so, she performs a series of experiments obtaining the following results: AOR = 1.30 kg/m3 • day, a = 0.91, and 3 = 0.94. If the aeration is to be maintained to effect a dissolved oxygen concentration of 1.0 mg/L at 25°C in the reactor, what SOR should be specified to the manufacturer of the aerator?
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