found in the aquatic environment, a n d t h a t some species of algae are very efficient in reducing arsenate to arsenite in their environment without building up significant cellular contents of arsenic. Acknowledgments
( 2 ) Andreae, M. O., Deep-sea Res., 25,391-402 (1978). (3) Andreae, M. O., Limnol. Oceanogr., 24,440-52 (1979). (4) Lunde, G., Acta Chem. Scand., 27,1586-94 (1973). ( 5 ) Irgolic, K. J., Woolson, E. A,, Stockton, R. A., Newman, R. D., Bottino, N. R., Zingaro, R. A,, Kearney, P. C., Pyles, R. A,, Maeda, S., McShane, W. J., Cox, E. R., Environ. Health Perspect., 19,61-6
(1977).
T h e authors thank E. D. Goldberg for his support of this study. We are indebted to A. A. Benson for the use of his laboratory and equipment. J. B. Jordan provided the phytoplankton cultures. T. Enns, R. W. Eppley, F. T. Haxo, and E. H. Renger gave permission to use some of their equipment. R. 0. Mumma provided valuable help with the chromatographic procedures.
(6) Eppley, R. W., Holmes, R. W., Strickland,J. D. H., J . E x p . Mar. Riol. Ecol., 1, 191-208 (1967). (7) Andreae, M. O., Anal. Chem., 49,820-3 (1977). (8) Button, D. K., Dunker, S. S., Morse, M. L., J . Racteriol., 113,
Literature Cited
Receiued for revieu: October 20. 1978. Acceoted January 22. 1979. This work was sponsored by the Office of Naval Research, Contract CSN NO00 14-75-C-0152.
(1) Braman, R. S., Foreback, C. C., Science, 182,1247-9 (1973).
599-611 (1973). (9) Edmonds, J. S., Francesconi, K. A., Cannon, J. R., Raston, C. R., Skelton, B. W., White, A. H., Tetrahedron Lett., 18, 1543-6 (1977).
Removal of Organic Acids from Rhine River Water with Weak Base Resins Sheldon Evans" and The0 F. J. Maalman Esmil Research Laboratories, Hoogovens ljmuiden BV, the Netherlands
T h e scavenging process investigated was found to be approximately 65%)effective in removing humic acids from Rhine River water during a 2-year test period. Chemical requirements were 0.6 equiv of hydrochloric acid and 0.6 equiv of lime per mi' of product water. T h e waste, which comprised 1%solids, corresponded to 1m:' per 1000 mlj of product water. T h e solid portion was calcium carbonate into which over 80% of the eluted organics were trapped. Humic substances represent the major soluble organic contaminant of most natural waters. They can be subdivided into groups t h a t include humic acids and fulvic acids; fulvic acids are the most predominant ( I , 2). Humic substances are rather stable compounds that are not easily biodegraded, and structurally contain groupings t h a t include alcoholic OH, phenolic OH, quinonoid, carboxyl, and methoxy ( 3 , 4 ) .Activated carbon, operating under conditions for taste and odor removal, is not particularly effective in removing humic substances; such removal requires long contact times (5-7). Macroporous strong and weak base resins have been found to be particularly effective in removing humic acids from natural waters ( 5 , 8-13). Strong base resins have been successfully applied to the removal of a major portion of the organic precursors to the chloroform formation that results from chlorination of natural waters (14). T h e elution of organics from ion exchange resins can result in a considerable disposal problem. In practice the levels of chemical regenerants used for strong base resins vary between 1.5 and 3 equiv of sodium chloride per L of resin along with approximately 0.5 equiv of caustic per L of resin (4,8, 11-23). Organic elution of weak base resins is accomplished with between l and 2 equiv of caustic per L of resin; rinsing with hydrochloric acid after each regeneration or after several regenerations is also practiced (11-13, 1 5 ) . In the demineralization of Rhine River water by ion exchange, lime slurries have been used as the regenerant for weak base resins; organics were effectively handled (16). A major objective of the process herein under evaluation is the
* Present address, Continental Oil Company, P.O. Box 2197, Room 2710, Houston, Tex. 77001.
determination of the applicability of lime slurry as regenerant for weak base resins that function as scavengers. In addition to determining the effectiveness for adsorption of humic acids in repeated cycles, the elution process is evaluated with respect to savings in economy and ecology; such savings can be reflected by utilizing less chemicals for elution and by the substitution of lime for sodium hydroxide. Experimental Methods T h e major portion of the test program was carried out in perspex columns (70 mm diameter) with 3.8-L samples of the weak base resins A 20s (Imacti), S 37 (Duolite), and IRA 94s (Rohm and Haas). One bed volume is the volume occupied by the resin, namely, 3.8 L. Rhine River water was passed through each column a t a rate of 50 L/h. Additional tests were carried out in larger perspex columns ( 1 3 cm diameter) with 17-L samples of the weak base resins, MWA-1 (Dow) and 368 P R (Duolite). Here one bed volume is 17 L. T h e flow rate during the scavenging process was 250 L/h. Elution was accomplished by first passing 4% HCl through the resin bed such that the level was 0.6 equiv/L of resin. This was followed by the passage of a 4% lime slurry (16);the level was 0.6 equiv of Ca(OH)e/L of resin. Rhine River water, a t ambient temperature, was used both for chemical dilution and for the rinsing of the resin bed. Duration of the elution process (regeneration and rinse) was about 1.5 h. Industrial grade hydrated lime (Edelwit, 95% pure, HF1 110 per ton) was used. Permanganate numbers and chemical oxygen demand (COD) were based on a 10-min boiling permanganate consumption and a 2-h dichromate consumption, respectively. Humates were evaluated by the determination of ultraviolet absorbance in 100-mm cells a t 275 and 300 nm ( 17). Results a n d Discussion T h e scavenging process was controlled simply by the volume of product delivered. A run was stopped after passage of 1000 f 100 bed volumes. Analyses determined a t various parts of the run are shown in Tables 1-111. Toward the end of the program longer runs were investigated (Table 111).It can be seen t h a t the process was effective for a wide variety of feed
0013-936X/79/0913-0741$01.00/0 @ 1979 American Chemical Society
Volume 13, Number 6, June 1979
741
Table 1. Results of Scavenging Runs; lmacti A 20s run no.
monthlyr
bed vol passed
6 10 12 19 24 29 32 42 46 54 54 57 57 57 61 61 67 73 78 84 92
Octl1975 Nov Dec Jan/1976 Mar April May June July Aug Aug Sept Sept Sept Oct Oct Jan/1977 Mar April May July
488 733 510 950 800 950 1075 1050 1000 250 740 40 550 1000 350 1000 900 910 1000 950 1000
permanganate no. leed product
10 15 14 15 19 16 13 11 14 12 12 15 14 14 17 18 15 9 9 10 13
5 7 6 5 9 6 8 7 8 6 7 8 7 7 9 10 8 5 5 5 6
feed
8 9 10 10 10 14 11 13 7 9
humates, ppm product
2 3 4 3 3 6 6 3 3 4
COD leed
product
10 11 13 19 16 16 16
4 4 4 9 12 10 8
Table II. Results of Scavenging Runs; Amberlite IRA-94s run no.
monthlyr
6 9 19 25 29 29 29 35 35 35 40 40 45 51 56 56 64 68 68 68 74
April11976 May June July Aug Aug Aug Sept Sept Sept Oct Oct Jan11977 Mar April April May June June June July
bed vol passed
1000 1045 1050 760 15 300 800 25 315 950 200 875 855 910 50 860 820 5 220 600 950
permanganate no. feed product
6 6 7 7 6 8 8 7 7 9 8 8 8 5 4 6 4 5 6 6 6
16 13 11 16 13 14 14 15 16 15 17 16 15 9 9 9 8 13 13 13 14
feed
9 10 9 12 12 10 10 10 13 7 9 9 9 9 10 9 10
humates, ppm product
6 2 3 4 3 4 4 4 4 2 3 4 4 2 3 3 4
COD feed
product
12 12 12 13 16 13 16 16
-
characteristics. During the course of the program, the temperature of the Khine River water, used as the feed and for the elution, varied between 3 and 17 "C. T h e salinity varied between 4 and 9 equiv per million. Typical seasonal variations have been reported elsewhere (16). I t is recognized that permanganate numbers and COD values represent, a t best, qualitative secondary measurements. Humates are accurately determined when the various fractions are separated and spectrophotometrically analyzed ( I , 2, 4 ) . T h e method used herein for humate determination is therefore qualitative as opposed to exact. Nevertheless, it can be concluded that approximately 65')0 of the humates present in the feed were removed by the process. T h e removal of 60-70'% of humic acids, as measured by permanganate con742
Environmental Science & Technology
sumption and optimal density measurements, has been found i n other laboratories ( I , 18).T h e variation in organic pickup during the course of this study, in terms of permanganate number, was between 4 g/L of resin (e.g., Table I, run 78, Table 11, run 51) and 13 g/L of resin (Table 111, run 6). T h e associated variation with respect to humic acid adsorption was between 5 and 19 g/L of resin, respectively. On the basis of work performed by Rook ( 2 4 ) ,it can be speculated that this process should be effective for the removal of precursors to haloform formation. Surrogate measurements, such as those utilized herein, are not sufficient to establish the effect on haloform formation; it is necessary to specifically determine haloform concentrations (6). Auxiliary tests wherein haloforms are being determined are
Table 111. Representative Results of Scavenging Runs, 1977 resln
s 37
368 PR
MWA-1
run no.
month
5 13 18 18 23 23 35 35 35 5 5 12 20 6 6 6 6 6 10 20
Jan Mar April April May May July July July Sept Sept Nov Dec Aug Aug Aug Aug Aug Sept Oct
bed VOI passed
feed
500 910 50 860 10 875 5 180 790 55 1030 1340 1000 325 685 950 1300 1635 1500 1690
12 9 9 9 9 10 13 13 13 14 15 13 10 10 13 16 16 15 11 10
presently in progress a t a potable water production plant and will be the subject of a subsequent publication. Chemical Requirements T h e major operational costs are those associated with the chemical regenerants and the scavenger resin. Based on a 1000 bed volume process, the chemical requirements for lime and HC1 are each 0.6 equiv/mi3of product water (2.3 equiv/1000 gal of product). These values correspond to Netherland costs of 0.3 and 1.2 cents/m:j of product, respectively. T h e cost of scavenger, based on a 10-year life, is 0.9 cent/m:j of product. This lifetime is based on a 100 mi3/hplant in the Hoogovens demineralization facility t h a t uses IRA 94s as part of an ion exchange train. T o date it has undergone 800 regenerations with no fall off in capacity or efficiency. T h e basis for this plant has been previously reported (16).T h e long throughput scavenging process requires about 90 regenerations per year. Waste T h e total waste volume of 10 bed volumes corresponds to 0.1 m '/m of product. Approximately 1% of this was solid calcium carbonate into which a t least 80%of the organics were trapped. T h e supernatant comprised 1600 ppm of C1-, 450 p p m of S 0 4 L - , 1200 ppm of Ca2+, a p H of 11.5, and a permanganate number of 100. In several runs the HC1 that was passed through the resin bed was displaced with water a n d collected. T h e resulting solution had a permanganate number and a humate concentration of the order of 2000 ppm. It is likely t h a t this effluent was rich in fulvic acids; fulvic acids are soluble in mineral acids ( 3 , 4 ) .T h e addition of the effluent from lime regeneration and rinse results in the precipitation of calcium carbonate, whereupon most of the organics are removed from the solution.
Conclusions T h e use of scavenger resins for the removal of humates from natural waters has been previously established (1, 18).Based
permanganate no. product
humates, ppm product
feed
7 5 6 5 5 5 4 6 6
4
10 7 9 9 9 9 10 10 9 12 11 16 7 8 12 21 21 16 7
5
8
4 4 6
5 4 6 6
8 7
2 3 4 4 4 3 4 4 4 2 3 8 2 2 3 4 7 3 2 2
on the process tested herein, it can be concluded that 60-70% of the humates present in Rhine River water are effectively -emoved in a cyclical process. This process is unique, however, with respect to other scavenging processes (5, 10-13, 15) in that: there is a significantly lower chemical requirement, waste volumes are lower, heating of regenerants and rinse water is not necessary, there is no need for softened or den-ineralized water (which would require additional chemicals), and lime is used instead of caustic. The portion of the waste in the solid form results in significantly reducing the organic content of the supernatant water. Literature Cited (1) Wilson. A. I,.. J Aaol Chem . 9.501 11959). ( 2 ) Black, .4.P., Chris'tman, R. F., Am. Water Works A s ~ o c .55, , F j .
897 (196:j). ( 3 ) Oden, S., Koiloidchern. Reih., 11, 75 (1919). (4)Packhain. H. F.. J . Water Treat. Exam., 13,316 (1964). (%5)Gauntlett. K. B., Packham. R. F., C h r m . f n d . (London)(Sept 1, 197i3). (6)Symons. .J. M., Carswell, .J. K., Clark, R. M., Love, 0. T., Jr.. Miltner, R. -I., Stevens, A. A., "Interim Treatment Guide for the
Control ot' Chloroform and Other Trihalomethanes", Municipal Environmental Research Lahoratory, Cincinnati, Ohio, June 1976. ( 7 ) Coogan. G . -1..Hell, G . R., ,Jayes. D. A,, Ahrams, I. M., J . N . Engl. Watrr Works Arsoc., 82, 1 (1968). (8)LViIson. A . L., J . Appl. Chrm.. 9,352 (1959). (9)Frisch, N. W., Kunin, R.. J . Am. Water Works AMJC., .52, 875 (1960). (10) Arden, T. V., Proc. soc. Water Treat. t'xam., 12, 146 (1963). (11) Abrams, I. M., C'hrm. Eng Symp. Srr., 65, 106 (1969). (12J Seidl. ,I., .%c. ('hem. f n d . , 491 (1969). (13) Oehme. C . . blartinola, F., C'hrm. f n d . ( L o n d o n ) (Sept 1, 1973).
Hook, d. .J.. J . Am. Water Works Assoc., 68, 168 (1976). (15) Rebhun, M., Kaufman, W. J., SERI, Report No. 67-9, Sanitary Engineering Research Laboratory. University of' California, 1967. (16) Evans, S., Gomes, R. M., L)f,salinnlion, 19, 493 (1976). (17) Electricite de France, Direction de la production et du Transport Service de la Production Thermique Division Laboratoire, St. Denis, LAG-7663 K 915. (18) LVilson, A. L., J . Appl. Chem., 9,510 (1959). (14)
Recrii~ed/or recieic April 17, 1978. Accvptrd Februar), I d , 1979.
Volume 13, Number 6, June 1979
743
