Page 646 - Fundamentals of Water Treatment Unit Processes : Physical, Chemical, and Biological

Gas Transfer 601

Determine also the K L a coefficient and compare with Given
values given from aeration installations. . Bubble aeration
1
. K L a(measured) ¼ 2.5 h .
Hint: Obtain properties from Appendices and calculate
. h(diffuser) 1 ¼ 5.0 m (16.4 ft)
diffusivities by the Wilke–Chang equation.
18.13 Aerator Test Data Required
Given Estimate the effects of changing one variable at a time
Aerator tests were performed using a basin at the Los in Equation 18.44, for example,
Angeles County Sanitation District’s Joint Treatment (a) Suppose the depth is decreased by one half
Facility (Yunt and Hancuff, 1988, p. 5). Data obtained (b) Suppose the volume is decreased by one half
(c) Suppose the airflow is increased by a factor of two
were as follows:
(d) Suppose the bubble diameter is decreased by a
factor of two
Depth Q (Air)
0
P=V K L a(20) C * (e) As a second part of the equation, consider the
3
1
3
Date (m) (ft) (hp=1000 ft ) (scfm) (m =m) (h ) (mg O 2 =L) E(ST) effects of each variable changed on other vari-
ables, that is, discuss the effects
03=24=78 7.62 25 0.28 73.8 2.08 5.34 11.42 0.495
Hint: The effects of each of the variables indicated,
one at a time, is seen by examining Equation 18.44.
The reactor data are as follows: V(reactor) ¼ 6.1 m The interdependencies are with respect to the effect of
3
6.1 m 6.1 m (20 ft 20 ft 25 ft deep) ¼ 283.17 m . V on z, the effect of h on z, the effect of Q on z. Also,
0
[The foregoing data were obtained using a Nortont v w may be affected directly by Q , and then begin to
0
fine-bubble diffuser.] taper asymptotically up to some limit.
Required
Calculate E(ST) and compare with that obtained in the ACKNOWLEDGMENTS
foregoing table.
18.14 Calculation of E(WTp) and K L a from Survey Data of The author is indebted to Tony Kalinske, director of research,
Houck (1988) and Gerry Shell, research engineer, for involvement in full-
scale turbine aerator testing, c. 1968, while doing summer work
Given
at Eimco Corporation, Salt Lake City, Utah. Similar proced-
Table 18.8 is a compilation of various data, including
ures were used by students in a laboratory course at Colorado
aeration, obtained from some six activated sludge
State University, c. 1970–2000, to generate data for K L a deter-
plants throughout the United States with two from
minations for air, pure oxygen, and oxygen stripping with
Canada (19 of ours given in the original data).
nitrogen gas. Some of these data were used for this chapter.
Required
William F. Clunie, technical manager, Water, AECOM,
(a) Estimate the efficiency of oxygen transfer, that
Wakefield, Massachusetts, gave permission (2010) to use
is, E(W, T, p) for the conditions at hand of the
Figure 18.13, generated at CSU, c. 1996, in conjunction
plants, for example, wastewater, temperature, and
with a lab partner, Y. Wu (who could not be located).
atmospheric pressure at hand (assume sea level).
Dale W. Ihrke, PE, plant manager, San Jose=Santa Clara
(b) Also calculate the K L a values for each plant. Set
Water Pollution Control Plant, San Jose, California, kindly
up a spreadsheet to calculate these parameters for
gave permission (2010) to use photographs of the aeration
each plant for which data are given. Discuss the
basins at the plant, Figure 18.16a and b, taken by the author
results and the variation found.
with permission, c. 1991.
18.15 Chlorine Gas Uptake to Aqueous Phase
Steve Frank, public information officer, Metro Wastewater
Given Reclamation District (Denver), provided photographs of the
Chlorine gas is used commonly at municipal water aeration basins, Figure 18.16c and d, at the Robert W. Hite
treatment plants for disinfection. Treatment Facility, North Plant, and granted permission for
Required their use. The district administers some 370 km (232 mi)
At the gas–water interface, is the gas film or the liquid interceptor sewers as well as the 530 mL=day (140 mgd)
film likely to have the greatest impedance to gas trans- Robert W. Hite Treatment Facility serving 59 local govern-
fer? Sketch what you think should be the gas concen- mental entities, e.g., cities and sanitation districts, and some
tration gradients in the gas phase and aqueous phases, 1.6 million persons. The District and Frank have provided
respectively. Provide the mathematical rationale for hospitality to the author along with many graduate classes
your responses. over a period of three decades.
18.16 Effects of Independent Variables on K L a for Bubble Frank D. Edwards, president, Bisco Environmental, Inc.,
Aeration Taunton, Massachusetts, kindly gave permission (2010) to