fluidized-bed system. These results indicate that further development of the process is warranted. Regarding future development activity, emphasis should be placed on evaluating factors such as unit capacity, heat requirements, and material losses which would provide data for economic evaluations. Because of its greater flexibility and higher unit capacity, it was concluded that further research be made with fluidized inert bed system. Future Work A pilot-scale study of the fluidized inert bed technique is currently being initiated under contract with the FWPCA. This study will involve operation of a 10-inch-diameter fluidizedbed unit for production of 30 pounds of regenerated carbon in an 8-hour period. The unit has been designed with an integral combustion chamber in which propane will be burned with air to provide the necessary heat input and regeneration atmosphere. Feed to this unit will be partially dried spent
carbon containing up to 50% moisture. The regenerated carbon produced will be recycled to FWPCA's pilot adsorption system for evaluation of the combined system performance. Results from the pilot-scale study are expected to provide the necessary data for economic evaluation and scale-up of the fluidized-bed process. Acknowledgment The advice and assistance of the many individuals at FWPCA who participated directly in the program are greatly appreciated. Received for review December 27, 1968. Accepted October 20, 1969. Presented at the 156th National Meeting, ACS, Atlantic City, N . J . , September 11, 1968. The research upon which this unit publication is based was performed pursuant to Contract No. 14-12-113, with the Federal Water Pollution Control Administration, Department of the Interior.
COM MUN ICAT1O N
Ultrafiltration of Aquatic Humus Egil T. Gjessing Norwegian Institute for Water Research, Blindern, Norway
Filtration of aquatic humus through Diaflo ultrafiltration membranes suggests that approximately 10% of the organic carbon and 1% of the colored matter have molecular weight below 1000. The experiments indicate also that about 50 and 90% of organic carbon and color, respectively, are found in the fraction which is not penetrating the filter which is supposed to retain molecules larger than 20,000 in molecular weight.
T
he brown-yellow color of surface water, originating from soil humus, causes considerable problems for many waterworks. Gel filtration of humus isolated from natural water suggests that it consists of a complex mixture of organic substances ranging in molecular weight between probably less than 1000 to more than 200,000 (Gjessing, 1965, 1966; Gjessing and Lee, 1967; Gassemi and Christman, 1968). In the present work Diaflo ultrafiltration membranes (formerly Diaplex) have been used to separate humus according to molecular size. The Diaflo membranes (Amicon Corp., Lexington, Mass.) are molecular filters manufactured from synthetic polymers. They are maintained to be nonplugging, and may be used over a wide range of pH. The Diaflo membranes were first reported used in 1965, (Blatt, Feinberg, et a[., 1965) and since then have been used by biochemists for concentration and purification of biological fluids (Michaels, 1965; Wake and Posner, 1967; Blatt, Hudson, et al., 1967). At present there are eight variants of the Diaflo membrane filters available. In the work presented below the following three have been used :
Diaflo membrane: Code No. UM-2 UM-20 UM-20E
Retaining molecules larger than (M.W.) 1,000 10,000 20,000
The composition of the water sample used in the experiments is given in Table I. Ten milliliter-samples of concentrates of these waters (evaporated at 30" C. under reduced pressure), were filtered through a UM-2 membrane with compressed nitrogen (pressure of 4.5 kg. per using an Amicon filtration cell (Model 50). The fraction retained by the membrane was washed with portions of distilled water until the filtrate contained 5 mg. carbon per liter (or less) and then passed through a UM-10 membrane in the same manner. Finally, after washing, the Table I. Composition of Natural and Concentrated Sample of Aquatic Humus Soec. CalOre. Color cond. Iron cium carbh mg. 20°C. mg. mg. mg. Sample Pt/l. pS/cm. Fe/l. Ca/l. C/l. Bogerudmyra 15th Nov. 66 (natural sample) 158 60 0.350 0 . 8 6 28.0 Bogerudmyra conc. 40 times 5.700 960 16.40 36.0 950 Hellerudmyra (st. 21) 6th Febr. 69 (natural sample) 79 25 0.600 1.62 19.0 Hellerudmyra conc. 40 times 4.000 555 18.40 56.0 599.0 Volume 4, Number 5, May 1970 437
SAMPLE :
Bogerudmyra
960 p S I c r n
9.5 rngC
5,l
57
mgPt
SI
164 p g Fe 0,,36 rngCa
86 0,12
mgC = 5L8L mgPt -90% pg Fe = 5 2 % mg Ca = 33 'lo
I
10 rnl 135 ,,slcrn
1
J. 1,1 0.9 33 0.13
rng C = 12 m g P t = 1,6 p g Fe - 2 0 rng Ca 36
rng C = 12 "1. rng Pt 1 . 1 '1. 8 p g Fe = 5 Q/. 0,06 m g C a = 17 ' l o
"I. "1. "lo 'I1.
1 .I 0.6
1.3 1.6 1L 0.05
mg C rngPt pg F e mgCa
=IL % =2.5"10 = 9 "1. = 1L "I.
S A M P L E : Hellerudrnyra 6.0 rngC
2,8
rng C rngPt 96 p g Fe 0,20 rng Ca
3L 184 pg Fe 0.56 mgCa
\ '\
"UM
mg C = 7 rng P t = 0,8 '10 7 p g Fe = L '1. 0,13 rng Ca = 23 '1.
L7V. 85V0
= 52010 = 36%
P
El,--, I /
/-
L 7 5 pS1crn
0,L 0,3
-
=
-IO"---+-
0,7 0.6
rng C rngPt 15 p g F e 0.18 rngCa
L:
=
12 '10 1,s0/o 8 "lo
= = 32 'I1.
1,3 2,8 19 0.08
rng C = 2 2 'I. rng P t = 7 "1. p g F e = 10 'I1. rngCa 1L ' l o
Figure 1. Filtration of concentrated aquatic humus from Bogerudmyra and Hellerudmyra through Diaflo ultrafiltration membranes, UM-2, UM-10, and UM-20E
fraction retained by this filter was filtered through a UM-2OE membrane and washed in the same way. The composition of the retained fraction from the latter filtration and the different filtrates combined with the washing waters is illustrated in Figure 1. Iron was determined colorimetrically with 2,4,6-tripyridyl-s-triazine (Henriksen, 1966), calcium with a PerkinElmer atomic absorption spectrophotometer (Model 303), and organic carbon on Beckman Carbonanalyzer (Model 915). Except for iron, the recovery of the different components is fairly good. Moreover it is seen that the major part of the organic matter and the iron do not penetrate the membrane UM-20E, which suggests a molecular weight higher than 20,000. This is in agreement with earlier results (Gjessing and Lee, 1967). An increasing trend towards higher molecular weights seems to exist for carbon and color, whereas calcium is seen to be present both in the low and high molecular weight fractions. Regarding iron, the sample from Bogerudmyra follows the same trend as calcium. For Hellerudmyra, however, the iron distribution is similar to that of organic carbon and color. Finally, the results show that most of the color (more than 8 5 z ) of the concentrated water sample is present in the high molecular weight fraction (larger than 20,000).
Dialysis of calcium chloride and a glucose solution through the same membranes have shown that less than 0.5% of 438 Environmental Science & Technology
calcium and organic carbon is retained by the filters used after a few successive washings. Although the two samples do show similar distributions, some small differences are noticeable. This disagreement is probably due to an actual difference in the chemical composition in the two samples. The use of Diaflo ultrafiltration membranes is believed to be useful in the studies of aquatic humic substances. Further work on this is in progress. Literature Cited Blatt, W. F., Feinberg, H. P., Hopfenberg, C. A., Science 150, 224 (1965). Blatt, W. F., Hudson, G. B., Robinson, S. M., Zipilivan, E. M., Nature 216, 511 (1967). Gassemi. M.. Christman, R. F., Limnol. Oceanog. - 13 (4), 583 (1968).' Gjessing, E. T., Nature 208,1091 (1965). Gjessing, E. T., Proceedings of an IBP-Symposium, p. 191, Koninklijke Nederlandse Akademie van Wetenschappen, Amsterdam, 1966. Gjessing, E. T., Lee, G. F., ENVIRON. S a . TECHNOL. 1, 631 (1967). Henriksen, A., Vattenhygien 1 , 2 (1966). Michaels, A. S., Znd. Chemistry 57,32 (1965). Wake, J. R. H., Posner, A. M., Nature 213,692 (1967). Received for reciew August 18, 1969. Accepted Nocember 20, 1969.
