Page 887 - Fundamentals of Water Treatment Unit Processes : Physical, Chemical, and Biological

842 Appendix F: Alum Data and Conversions

Equation F.7 was the basis for obtaining the values in Figure set of experimental data such as given in Table CDF.3
F.4b. The terms in the denominator for the conversions were, (adapted from Table 1, General Chemical, 1995) one can
SG(alum solution) ¼ 1.335, r(water) ¼ 998.2 g=L (208C). use SG as a surrogate for concentration. Table CDF.3 has
several sub-tables as follows:
Tables CDF.3(a) through CDF.3(d) are encapsulated in
F.4.6 SPECIFIC GRAVITY–CONCENTRATION RELATION
Figures F.5 and F.6. Table CDF.3(e) expands on Section F.4.7.
The specific gravity (SG) of an alum solution depends on its Figure F.5 shows a plot of the data from Table CDF.3(d).
concentration, i.e., mg Al 2 (SO 4 ) 3 14H 2 O=L solution. From a The polynomial coefficients, also shown in Figure F.5, are a

TABLE CDF.3
Alum Conversions
Table CDF.3(a) Molecular weight of alum forms
Table CDF.3(b) Polynomial coefficients for estimating alum concentrations from SG
Table CDF.3(c) Polynomial coefficients for estimating alum mass percent solids from SG
Table CDF.3(d) Alum concentration as function of ‘‘dry alum’’ added
Table CDF.3(e) Cost calculation for alum as Al 3þ and sensitivity to SG of liquid alum and C(Al )
3þ
[Double click on ‘‘Table CDF.’’ below to bring up Table CDF.3]

TABLE CDF.3
Alum Conversions (Excerpt Showing only Tables CDF.3(a) and (b))

Table CDF.3(a) Molecular Weights of Alum Forms Table CDF.3(b) Polynomial Coefficients a
Element at. wt. Compound MW Compound M0 M1 M2
Al 26.982 Al 2 (SO 4 ) 3 14H 2 O 594.136 Al 2 (SO 4 ) 3 14H 2 O 1011.9 312.25 699.2
S 32.066 Al 2 (SO 4 ) 3 18H 2 O 666.132 Al 2 (SO 4 ) 3 18H 2 O 1134.3 350.01 783.01
O 15.999 Al 2 (SO 4 ) 3 342.15 Al 2 (SO 4 ) 3 577.37 178 399.11
H 1.000 Al 2 O 3 101.961 Al 2 O 3 172.09 53.103 118.91
O 15.999 Al 2 53.964 Al 2 91.909 28.361 63.506

3
Note: r(water) ¼ 998 kg=m .
a
For alum concentrations from SG alum, i.e.,
y ¼ M0 þ M1 x þ M2 x 2

TABLE F.3
Cost of Liquid Alum a
(1) The cost of liquid alum in metric units is
dollars $181 ton 2:205 lb

kg alum solution ¼ ton alum solution 2000 lb kg
$0:20
¼
kg alum solution
(2) In terms of Al, the cost is (using mass percent Al from Table F.3 for SG ¼ 1.34)
dollars $0:20 kg alum solution
kg Al ¼ kg alum solution 0:0445 kg Al
$4:48
¼
kg Al
Sources: Adapted from Letterman, R. D., Overview of Operational Control of Coagulation and Filtration
Processes, Department of Civil Engineering, Syracuse University, Syracuse, NY, 2000, paper
presented at Seminar on Water Treatment, New York Section, American Water Works
Association Seminar, Rochester, NY, November 1985.