Attenuation of Pollutants in Municipal Landfill Leachate by Passage Through Clay Robert A. Griffin*, Neil F. Shimp, John D. Steele, Rodney R. Ruch, W. Arthur White, and George M. Hughes" Environmental Geology Laboratory, Illinois State Geological Survey, Natural Resources Building, Urbana, 111. 61801
To evaluate the potential of clay minerals for attenuating the various chemical constituents of landfill leachate, leachate was passed through laboratory columns that contained various mixtures of calcium-saturated clays and washed quartz sand. Leachates were run through the columns for periods of up to 10 months, during which time effluents were periodically collected and analyzed for 16 chemical constituents. Chloride, Na, and water-soluble organic compounds (COD) were poorly Mg, attenuated by passage through the clay columns; K, "4, Si, and Fe were moderately attenuated; and heavy metals such as Pb, Cd, Hg, and Zn were strongly attenuated by even small amounts of clay. Concentrations of Ca, B, and Mn in the column effluents increased markedly over the original leachate concentrations. Of the three clays used in the study, montmorillonite had the highest attenuation capability, followed by illite and then kaolinite. Attenuation was a function of the CEC of the clay mineral, the initial exchangeable cations on the clay, the chemical composition of the leachate, and the pH of the leachate.
The sanitary landfill method of municipal and industrial solid waste disposal has been widely used in the United States for the past 30 years. Garland and Mosher ( I ) estimated that 14 000 landfills are located throughout the nation. In 1976 the United States was producing and placing in landfills more than 360 million tons of household, commercial, industrial, and municipal solid waste per day, disposal of which had an annual cost of more than $4.5 billion ( 2 ) . The disposal of such huge volumes of solid waste by landfilling is not without its environmental impact. When refuse buried in a landfill comes in contact with water, leachate, a mineralized liquid high in organic substances, is produced which may move out of the fill and pollute the ground water. Several studies ( I , 3-6) have shown that pollutants such as organic compounds and heavy metals can be detected a t various distances from landfill sites. The clay content of the materials through which the leachate moved was related to the distance that the dissolved solids traveled. The proposal was therefore put forth ( 4 ) that certain clays might make suitable liners for disposal sites that had previously been rejected because they were located in highly permeable materials. However, no sound evidence existed to indicate how thick such a clay liner should be, which clay minerals would be best, or even whether a clay liner provides optimum conditions for pollutant attenuation. This paper reports the results of a study, the purpose of which was to investigate and evaluate the attenuating properties of several clay minerals and to determine whether they could be used as liners for sanitary landfills to prevent or mitigate pollution of ground and surface waters by leachates from municipal solid waste.
Methods and Materials The clays used in this study were the purified clay minerals kaolinite (1:l lattice type), montmorillonite (2:l expanding lattice), and illite (2:l nonexpanding lattice, mica type). The Present address, Ontario Ministry of the Environment, Toronto, Canada. 1262
EnvironmentalScience & Technology
kaolinite was collected from materials of Pennsylvanian age in Pike County, Ill. The site description and location were given by White (7),sample 996N. The montmorillonite used in the study was southern bentonite from the American Colloid Co. The illite was from the Minerva Co. Mine of the Allied Chemical Co. These clay minerals were chosen for study because they are the most common clay minerals in earth materials that would be used for landfill sites individually or in combinations. Earth materials containing one or more of these clay minerals can generally be obtained locally for landfill liners. The clays were brought to the laboratory where they were crushed, ground, and purified by sedimentation techniques to obtain the < 2 - ~ mparticle fraction that contained essentially pure clay minerals. The purified clay was then flocculated with 1 M CaC12, centrifuged, and spray dried. The clay minerals present in the < 2 - ~ mfraction were identified by x-ray diffraction techniques, and the results are given by Griffin and Shimp (8). Chemical analyses of the three clays are given in Table I. Exchangeable cations, and cation exchange capacity (CEC) were determined by standard methods (9) using neutral 1N ammonium acetate, with the exception of NH4+, which was determined by Na+ exchange on a split of the original sample. Total element content was determined by an x-ray fluorescence method (9) for the elements Si, Ti, Al, Fe, Mg, Ca, and K. The elements Na, Pb, Cd, Zn, B, and Mn were determined by acid digestion of the clay and atomic absorption analysis of the solution (IO). The carbon content, total and inorganic, was determined by the method described in Maxwell (11); organic carbon was determined by difference. External surface areas of the clays were measured by Nz gas adsorption (12). The predominantly Ca-saturated, :
4
' ?
" / //'I
montmorillonite
> illite > kaolinite
C
-
~~
Na
- ATN = 8.22 t 1.93 CEC
I
a____-_ pl
Mg-ATN
r = .91
10.4 t 5.1 CEC .95
r
i
i
__
i-
CEC
.
Sand
A
Illite
CEC
Kaolinite Montmorillonite
Ciay mixtures
'
Figure 4. Attenuation number related to cation exchange capacity (A) K, (B) NH4, (C)Na, and (D) Mg
2
2w J '
CEC
'
15
Io
-600
C Mn-ATN
.=
-50.6-16.6 ( % Kaolinite)
-400
z
Mn-ATN = -0.1 -5.93 ( % Montmorillonite) r = -95
-300.
I
20
A
30
40
50
Sand
Clay content ( % 1 3 Kaolinite 3 Ciay mixtures
Illite
d Montmorillonite
60
Figure 5. A) Ca attenuation number related to cation exchange capacity. B) Mn attenuation number related to clay percentage
The Ca-montmorillonite used produces rocks (e.g., Porter's Creek Clay) that have much higher permeabilities than Nadominated Wyoming-type montmorillonite. Such high permeability should make this montmorillonite more useful in making landfill liners in humid climates than some other types of montmorillonite. With its high cation exchange capacity, it would adsorb more of the cations in the leachate than either illite or kaolinite. With its greater permeability, it allows more water to pass through the liner than many other types of montmorillonite. The low permeabilities of other montmorillonite types would probably increase the hazard of lateral seepage from the sides of the landfill in humid climates. Some sodium montmorillonites tend to shrink when sodium is exchanged for divalent and trivalent cations or when salt concentrations are high. This shrinkage sets up tension, which in turn produces cracks called syneresis cracks. Syneresis cracks were common in irrigation ditches in Colorado that were lined with sodium montmorillonite (22).Shrinkage could be reduced considerably by using calcium montmorillonites and mixing them with other earth materials (e.g., 16-32% montmorillonite and 68-84% sand). The kaolinite used in this study is a fine-grained rock in which the crystallinity of the kaolinite crystals is poor. It has a high cation exchange capacity compared with other kaolinites. Well-crystallized kaolinites with large crystals have a cation exchange capacity of 1-5 meq/100 g. The kaolinite used in this study would be better suited for landfill liners than most kaolinites. The permeability of this kaolinite is lower than that of well-crystallized kaolinite with large crystals. The kaolinite in most sediments has a cation exchange capacity and permeability between those of the kaolinite used and the well-crystallized kaolinites. The illite used is similar in cation exchange capacity and permeability to the illite found in most sediments. The sediment from which the experimental illite was taken contained only one clay mineral-the illite-whereas most sediments that contain illite also contain other clay minerals. It was concluded that the attenuation order was due principally to the cation exchange capacity of each of the three clays. Attenuation will be a function of the CEC of the earth material, the cations present initially on the exchange complex, the chemical composition of the leachate, and the pH of the leachate. Acknowledgment
The authors are indebted to the American Colloid Co., Skokie, Ill., for supplying the montmorillonite clay; to the Minerva Co., Elizabethtown, Ill., for supplying the illite clay; and to the Ottawa Silica Co., Ottawa, Ill., for supplying the quartz sand used in this study. The authors thank Keros Cartwright, D. R. Dickerson, R. H. Shiley, W. J. Armon, J. K. Kuhn, J. A. Schleicher,L. R. Camp, G. B. Dreher, J. K. Frost, R. R. Frost, L. R. Henderson, R. M. Trandel, and D. B. Heck for assistance with portions of this research. Special thanks to R. J. Helfinstine and W. E. Cooper for special equipment. Volume 10, Number 13, December 1976
1267
Literature Cited (1) Garland, G. A., Mosher, D. C., Waste Age (March 1975).
(2) Black, R. J., Muhich, A.. J., Klee, A. J., Hickman, H. L., Jr., Vaughan, R. D., The National Solid Wastes Survey; An Interim Report, 53 pp, USHEW, Cincinnati, Ohio, 1968. (3) Cartwright, K., McComas, M. R., Ground Water, 6 (5), 23-30 (1968). (4) Hughes, G. M., Landon, R. A., Farvolden, R. N., E P A Report SW-12d, 1971. (5) Apgar, M. A,, Langmuir, D., Ground Water, 9,6 (1971). (6) Emrich, G. H., Compost Sci., 13,3 (1972). (7) White, W. A., Illinois Geological Survey Circular 282, Urbana, Ill., 1959. (8) Griffin, R. A., Shimp, N. F., Attenuation of Pollutants in Municipal Landfill Leachate by Clay Minerals, Final Report for EPA Contract No. 68-03-0211, Cincinnati, Ohio, 1976. (9) Shimp, N. F., Leland, H. V., White, W. A., Illinois Geological Survey Environmental Geology Note 32, Urbana, Ill., 1970. (10) French, W. J., Adams, S. J., Anal. Chim. Acta, 62, 324-28 (1973). (11) Maxwell, J. A., “Rock and Mineral Analysis”, pp 430-33,438-40, Wiley, New York, N.Y., 1968. (12) Thomas, J., Jr., Frost, R. R., Ill. Acad. Sci. Trans., 64, 248-53 (1971). (13) Chian, E.S.K., DeWalle, F. B., Compilation of Methodology Used for Measuring Pollution Parameters of Sanitary Landfill Leachate,
Ecological Research Series, EPA 600/3-75-011, p 158, Cincinnati, Ohio, 1975. (14) Grim, R. E., Cuthbert, F. L., Illinois Geological Survey Report of Investigations 102, Urbana, Ill., 1945. (15) Manger, G. E., US.Geological Survey Bulletin 1144-E, 1963. (16) Todd, D. L., “Ground-Water Hydrology”, p 53, Wiley, New York, N.Y., 1959. (17) Farquhar, G. J., Rovers, F. A., Proceedings of the Research Symposium, “Gas and Leachate from Landfills: Formation, Collection, and Treatment”, New Brunswick, N.J., March 1975, EPA, Cincinnati, Ohio. (18) Grim, R. E., “Clay Mineralogy”, pp 213,221, McGraw-Hill, New York, N.Y., 1968. (19) Griffin, R. A., Shimp, N. F., Environ. Sci. Technol., 10, 1256 (1976). (20) Cartwrieht. Keros. Griffin. R. A.. Gilkeson. R. H.. Ground Water. submitted-for publication. (21) Urioste, J. A., MS thesis, Universitv of Wisconsin, Madison. Wis.. 1971. (22) Dirmeyer, R. D., Jr., private communication, 1961.
Received for review October 6,1975. Accepted June 25,1976. Partial support for this work received from the U.S. Environmental Protection Agency, Cincinnati, Ohio, under Contract No. 68-03-0211.
Use of Adenosine Triphosphate Assay in Disinfection Control Edwin C. Tifft, Jr.*, and Stuart J. Spiegel O’Brien & Gere Engineers, Inc., 1304 Buckley Road, Syracuse, N.Y. 13210
A need exists for a rapid method of measuring the efficiency of disinfection of wastewater for purposes of regulating the addition of disinfectants. The determination of adenosine triphosphate (ATP)by the firefly bioluminescence assay may serve this purpose. Decreases in ATP concentration in combined sewer overflows treated with chlorine and chlorine dioxide parallel decreases in the traditional indicators of disinfection, total and fecal coliform bacteria. The disinfection procedure also inactivates a representative pathogen, poliovirus Sabin Type 1. Upon disinfection, the linear correlation coefficient of ATP with fecal coliform bacteria increases from 0.035 to 0.759, an indication that fecal coliforms may exhibit greater resistance to disinfection than those organisms which contribute the greater fraction of the total ATP pool in untreated samples. Any decisions regarding sanitary water quality based on ATP observations may therefore be a t least as safe as decisions made utilizing present criteria.
The present methods of determining the efficiency of wastewater disinfection processes and controlling the addition of disinfectants may not be adequate to meet recently enacted standards of 200 fecal coliforms per 100 ml of sampled water ( I ) without the risks involved in the presence of excess disinfectants (2).The traditional approach to the assessment of disinfection efficiency has been the enumeration of the coliform bacteria, especially fecal coliforms, which are generally accepted as an indication of contamination from human or animal sources and, consequently, the presence of pathogenic bacteria and viruses ( 3 ) .The principal objection to this approach is that one of the most common and rapid methods of bacterial enumeration, the membrane filter technique, requires a 24-h incubation period, during which incomplete disinfection or the addition of excess disinfectants may occur in the system. A second objection is that coliforms may not be 1268
Environmental Science & Technology
as resistant to disinfection as some pathogenic microorganisms, therefore an inadequate measure of disinfection efficiency ( 4 ) . The most common method of controlling disinfectant dosages is the monitoring of residual disinfectant to maintain a fixed level in the treated effluent ( 5 ) ,a method that admittedly has its limitations (6).Other methods may include addition of disinfectant based on historical flow patterns and periodic bacterial counts. These methods may be acceptable for domestic wastes in which the microbial variations are somewhat predictable, but totally unacceptable for wastes such as storm and combined sewer overflows in which these variations are large and unpredictable. The objection is that simply maintaining a fixed volumetric residual does not guarantee that bacterial and viral populations have been re; duced to a safe level. A more direct reflection of microbial activity than residual disinfectants is needed. The quantitative determination of adenosine triphosphate (ATP), using the bioluminescent reaction characteristic of fireflies, offers a potentially rapid alternative to bacterial measurements as an indicator of microbial content of a water sample ( 7 ) . McElroy (8) initially reported that an unreactive preparation of two extracts from firefly lanterns, one presumably containing luciferin, the other containing the enzyme luciferase, could be made to luminesce in the presence of ATP. This finding laid the foundation for the development of an ATP assay which cgn be performed with relative ease and accuracy, and may be utilized for the enumeration of microbial populations (9) or as a measure of biomass (IO). ATP is present as the driving force of bioenergetic reactions in all living cells ( 1I). I t is the primary phosphorylating agent for most biochemical enzymatic reactions and, therefore, the primary energy source in cellular metabolism. Only under rare conditions is ATP found in nonbiological systems (12, 13). ATP that is released by dying microorganisms is rapidly acted
