Physical, Chemical, and

Biological Aspects of

Subsurface Organic Waste Injection

near Wilmington, North Carolina

GEOLOGICAL SURVEY PROFESSIONAL PAPER 987
Physical, Chemical, and

Biological Aspects of

Subsurface Organic Waste Injection

near Wilmington, North Carolina

By J. A. LEENHEER, R. L. MALCOLM, and W. R. WHITE

GEOLOGICAL SURVEY PROFESSIONAL PAPER 987

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON: 1976
UNITED STATES DEPARTMENT OF THE INTERIOR 

THOMAS S. KLEPPE, Secretary

GEOLOGICAL SURVEY 

V. E. McKelvey, Director

Library of Congress Cataloging in Publication Data

Leenheer, J. A.

Physical, chemical, and biological aspects of subsurface organic waste injection near Wilmington, North Carolina.

(Geological Survey Professional Paper 987)

Supt.ofDocs.no.: 119.16:987

Bibliography: p.

1. Waste disposal in the ground North Carolina Wilmington region.

I. Malcolm, R. L., joint author. II. White, W. R., joint author. HI. Title: Physical, chemical, and biological aspects of

subsurface organic waste injection. . . IV. Series: United States Geological Survey Professional Paper 987. 

TD761.L43 628'.36 76-608225

For sale by the Superintendent of Documents, U.S. Government Printing Office

Washington, D.C. 20402 

Stock Number 024-001-02915-4
CONTENTS

Page

English-metric equivalents. . ............................................................ IV

Abstract .................................................................................................... 1

Introduction ................................................................................................ 2

Acknowledgments.............................................................................. 4

Hydrogeology, By H. M. Peek and R. C. Heath.................................... 5

Case history of waste injection ................................................................ 6

Installation and operation of initial well system ........................ 6

Construction and operation of expanded injection system........ 9

Field sampling methods............................................................................ 11

Industrial waste analysis.......................................................................... 12

Organic analysis ................................................................................ 12

Inorganic analysis.............................................................................. 15

Physical properties............................................................................ 17

Hydrochemistry of native ground water................................................ 17

Waste-aquifer interactions...................................................................... 18

Site study.............................................................................................. 18

Initial conditions........................................................................ 18

Initial conceptual model of injected-waste reactivity

and movement........................................................................ 19

Reactions observed at wells 1, 2, 3,4, and 5.......................... 19

Reactions observed at well 9 .................................................... 20

Reactions observed at wells 11,14, and 15............................ 20

Page

Waste-aquifer interactions Continued 

Site study Continued

Possible flow systems associated with injection

activities.......................... ..................................................... 23

Microbiological study................................................................ 26

Laboratory waste-aquifer reactivity studies....................................... 27

Introduction ........................................................................................ 27

Methods and materials.............. ..................................................... 27

Aquifer material ........................................................................ 27

Characterization of aquifer material .................................... 27

Waste constituent analyses...................................................... 27

Modified Hassler sleeve core holder ...................................... 28

Pressurization core-testing apparatus .................................. 28

Experimental design.......................................................................... 28

Testing the pressurization core-testing apparatus...................... 29

Leak testing ................................................................................ 29

Packing the Teflon sleeve with aquifer material................ 29

Experiment 1 kinetic study of waste .......................................... 30

Experiment 2 core solubilization study...................................... 34

Experiment 3 waste saturation study ........................................ 37

Final conceptual model of waste movement and reactivity .............. 39

Summary and conclusions........................................................................ 41

Selected references .................................................................................... 42

ILLUSTRATIONS

FIGURE 1. Hercules Inc. DMT Plant, Wilmington, North Carolina.............................................................................................................

2. Location of Hercules Inc., plant site.................................................................................................................................................

3. Diagram showing hydrogeologic conditions and injection-well construction for well I-7A ............................................................

4. Map of waste-injection and observation wells ...............................................................................................................................

5. Monthly average injection rate.........................................................................................................................................................

6. Graph of highest wellhead injection pressures .............................................................................................................................

7. Location of wells in initial system and pressure surface, January 1969 .................................................................................

8. Map of pressure surface, September 1970.......................................................................................................................................

9. Map of pressure surface and approximate limits of waste travel, October 1972 ...................................................................

10. Map of pressure surface with no injection, April 1973...................-......-....................................................................-...--- -

11. Construction features of observation well 14.................................................................................................................................

12. Analytical scheme of organic waste analysis.................................................................................................................................

13. Gas chromatogram of acetic and formic acids ...............................................................................................................................

14. Gas chromatogram and mass spectra of methylated-acid ether extract .................................................................................

15. Gas chromatogram of alkaline ether extract.................................................................................................................................

16. Gas chromatogram of neutral, volatile, waste constituents .......................................................................................................

17. Initial conceptual model of injected-waste reactivity and movement.......................................................................................

18. Variations in pH and residue on evaporation from samples taken during observation of waste front in wells 1 and 5.

19. Variables observed during passage of waste front in well 14.....................................................................................................

20. Constituents measured during passage of waste front in well 11 .............................................................................................

21. Hypothetical areal distribution of waste at the upper and lower boundaries of the injection zone ...................................

22. Probable internal circulation of ground water within well 14...................................................................................................

23. Comparison of number of bacteria per millilitre (as colony-forming units) in waste front (well 14) and in

	uncontaminated aquifer (well 11)...............................................................................................................................................

24. Diagram of modified Hassler sleeve core holder...........................................................................................................................

3

4

5

7

7

8

8

9

10

10

11

13

13

14

14

15

19

20

21

23

24

25

26

28

in
IV CONTENTS

FIGURE 25. Schematic diagram of pressurization core-testing apparatus .................................................................................... ....... ..... 28

26. Specific conductance breakthrough curve during leak-testing of Hassler sleeve core holder................................................ 29

27. Sodium, chloride, and DOC breakthrough curves for experiment 1 (flow rate=2inl/hr)...........^^ 31

28. Sodium, chloride, and DOC breakthrough curves for experiment 2 (flow rate=4 ml/hr)................................................... ... . 31

29. Iron and silica dissolution during experiment 2........................................ . .. . .. 33

30. Iron and silica dissolution during experiment 1.................................................................. .. .... . 33

31. Relative sorption of formaldehyde, acetic arid, and formic arid during experiment 2......- ...-.. ............................................... 34

32. Relative sorption of phthalic, terephthalic, and p-toluic adds during experiment 1......................................... ............................... 35

33. Hypothetical movement of injected waste within injection subzones.... ................................................................................... 39

34. Final conceptual model of injected-waste reactivity and movement ........................................................ .......... ........... ... 39

TABLES

 Page

TABLE 1. Chronology of significant events during injection ...................................................... ................................ ... 6

2. Injection-system well data................................................................. ...... ..... .. .................... ...................... ....... . .. . 7

3. Average organic analysis of waste............................................................................................ ... . ......... . 16

4. Inorganic waste analysis .......................................................................................,............................--...............--......------- 16

5. Inorganic analysis of native ground water found in aquifers at waste-injection site .............................................................. 17

6. Change in water composition with waste contamination .............................................................................................................. 19

7. Well 14 gas analyses ................................................................^^ 21

8. Relative organic composition of injected waste found in wells 11,14, and 15....... .................................................................. 22

9. Observation well flow-test data ......................................................................................................-........ - 24

10. Identification of isolates from well 11............................................................................... . .. .. . ... .. 26

11. Laboratory chemical data for waste-aquifer reactivity experiment 1 (flow rate=2 ml/hr).................................................... 31

12. Laboratory chemical data for waste-aquifer reactivity experiment 2 (flow rate=4 ml/hr)............................................... .. 32

13. Organic chemical data during waste-effluent monitoring of experiment 2................................................................................ 34

14. Organic chemical data during waste-effluent monitoring of experiment 1.................................................................. .... .... 35

15. Sorptive capacities of aromatic organic acids on aquifer material during experiment 2 ........................................................ 36

16. Organic and inorganic carbon analyses of fractionated and unfractionated injection-zone aquifer material.................... 36

17. Particle size analysis of injection-zone aquifer material................................................................... ........ .. . ... . 37

18. Fe, Al, and Mn analyses by graphite furnace technique of selected waste effluent fractions during experiment 2.......... 37

19. Chemical data during waste effluent monitoring of experiment 3 .............................................................................................. 38

20-36. Basic-data tables

20. Organic waste analyses............................................................................................. ........ ........... ...... ......... ... 46

21. Waste inorganic analyses sample collected 11-7-73 ...................................................................................................... 46

22. Inorganic analyses of water from surficial sand aquifer............................ ................................................................... 46

23. Inorganic analyses of water from 300-ft zone .................................................................................................................... 46

24. Inorganic analyses of water from 500-ft zone ...................................................................... .... . .. ... . - . 46

25. Inorganic analyses of water from 700-ft zone ......................................................................... .... ..... .... ..... . 47

26. Inorganic analyses of water from well 1.............................................................. ....-. ..... ... . ..... . . 47

27. Inorganic analyses of water from well 11............................................................................................................................ 48

28. Inorganic analyses of water from well 12.................................................................................................... ............... ... 49

29. Inorganic analyses of water from well 14.... .................................................................................. ....... .. .. 48

30. Inorganic analyses of water from well 15....................................................................... ........... . ... ... . . 50

31. Inorganic analyses of water from well 16............... .. . . . . ... . . . - - - 51

32. Inorganic analyses of water from wells 2,3,4, and 5.................................................................... ....... .. .... .. 51

33. Gas analyses............. ..................... ......................................................................................---..............--....... 50

34. Organic analyses of water from well 11 ............................................................................. 51

35. Organic analyses of water from well 14 .................. .. . .......... ... .... ...... . .... ... . 51

36. Organic analyses of water from well 15 .... . ..... .. .. .............. . ...,.. .................... .. ... 51

ENGLISH-METRIC EQUIVALENTS

foot (ft) = 0.3048 metre (m)

inch (in) = 25.4 millimetres (mm)

mile (mi) = 1.609 kilometres (km)

pound per square inch (psi) = .068947 bar

gallon (gal)___________= 3.785____litres (1)______
PHYSICAL, CHEMICAL, AND BIOLOGICAL ASPECTS OF

SUBSURFACE ORGANIC WASTE INJECTION

NEAR WILMINGTON, NORTH CAROLINA

By J. A. LEENHEER, R. L. MALCOLM, and W. R. WHITE

ABSTRACT

From May 1968 to December 1972, an industrial organic waste 

was injected at rates of 100 to 200 gallons per minute (6.3 to 12.6 

litres per second) into a sand, gravel, and limestone aquifer of Late 

Cretaceous age by Hercules Inc. located near Wilmington, North 

Carolina. This report presents both field and laboratory data pertaining to the physical, chemical, and biological effects of waste 

injection into the subsurface at this particular site, a case history of 

the operation, predictions of the reactions between certain organic 

wastes and the aquifer components, and descriptions of the effects of 

these reactions on the subsurface movement of the wastes.

The case history documents a situation in which subsurface waste 

injection could not be considered a successful means of waste disposal. The first injection well was used only for 1 year due to excessive wellhead pressure build-up above the specified pressure limit of 

150 pounds per square inch (10.3 bars). A second injection well 

drilled as a replacement operated for only 5 months before it too 

began to have problems with plugging. Upward leakage of waste into 

shallower aquifers was also detected at several wells in the 

injection-observation well system. The multiple problems of plugging, high pressures, and waste leakage suggested that the reactive 

nature of the waste with the aquifer into which it was injected was 

the primary reason for the difficulties experienced with waste injection.

A site study was initiated in June 1971 to investigate wasteaquifer interactions. The first stage of the study determined the hydrogeologic conditions at the site, and characterized the industrial 

waste and the native ground water found in the injection zone and 

other aquifers. The injection zone consisted of multiple permeable 

zones ranging in depth from about 850 to 1,000 feet (259 to 305 

metres) below land surface. In addition to the injection zone, aquifers 

were found near depths of 60, 300, 500, and 700 feet (18, 91,152, and 

213 metres) below land surface. The aquifers from 300 feet (91 

metres) down to the injection zone were flowing artesian with the 

natural pressure of the injection zone being 65 feet (20 metres) above 

land surface at the site.

The dissolved solids concentration in the native ground water 

increased with depth to an average value of 20,800 mg/1 (milligram 

per litre) (two-thirds that of seawater) in the water from the injection 

zone. Sodium chloride was the major dissolved solid, and all of the 

ground water below 300-feet (91-metres) depth was slightly alkaline.

Dissolved organic carbon of the industrial waste averaged 7,100 

mg/1 and 95 percent of the organic carbon was identified and quantified. The major organic waste constituents in order of decreasing 

abundance were acetic acid, formic acid,p-toluic acid, formaldehyde, 

methanol, terephthalic acid, phthalic acid, and benzole acid. Prior to

injection, the waste was neutralized with lime to pH 4 so that the 

major inorganic waste constituent was calcium at a concentration of 

1,300 mg/1.

The second stage of the site study involved the observation of 

waste-aquifer interactions at various wells as the waste arrived and 

passed by the wells. Water samples obtained from three observation 

wells located 1,500 to 2,000 feet (457 to 607 metres) from the original 

injection well gave evidence for biochemical waste transformations 

at low waste concentrations. Gas that effervesced from these water 

samples contained up to 54 percent methane by volume. Ferrous iron 

concentrations as high as 35 mg/1, hydrogen sulfide gas, and sulfide 

precipitates were additional indicators of biochemical reductive processes in the subsurface environment. Approximately 3,000 organisms per millilitre were found in uncontaminated ground water 

from the injection zone whereas in waste-contaminated wells, the 

number increased to levels as high as 1,000,000 organisms per millilitre. High concentrations of waste were found to be toxic to microorganisms. Most of the organisms isolated from uncontaminated 

wells were facultative, aerobic genera whereas the population 

changed to anaerobic strains in the contaminated wells. 

Methanogenic bacteria of the genus Methanobacterium and genus 

Methanococcus were isolated in pure culture from ground-water 

samples in which methane was found.

The relative ratios of formic acid, p-toluic acid, and terephthalic 

acid to acetic acid were lower in these ground-water samples than in 

the injected waste indicating degradation or sorption of formic, 

p-toluic, and terephthalic acids relative to acetic acid during the 

period of waste travel to these observation wells. The construction of 

the screened section of the observation wells allowed dilution of the 

waste and internal circulation of ground water so that it was impossible to determine quantitative waste concentrations in the various 

waste-receiving zones within the injection zone.

Highly contaminated ground-water samples obtained from five 

observation wells, located near (50 to 150 feet) (15 to 46 metres) the 

injection wells gave evidence for waste dissolution of aquifer carbonates and iron oxides. These samples contained carbon dioxide gas, 

calcium concentrations to 3,900 mg/1, and iron concentrations to 310 

mg/1. Organic complexation as well as acid dissolution was suspected 

to be the cause for the high iron concentrations. There was no 

microbiological activity apparent in these wells and samples.

Concurrent with and after the site study, a laboratory study was 

conducted in which waste was injected into cores of aquifer material 

obtained from the injection zone. The laboratory injection pressure 

was that of the hydrostatic pressure found in the injection zone. 

When a known volume of waste was injected into a core, the acidic
SUBSURFACE ORGANIC WASTE INJECTION, NORTH CAROLINA

waste initially dissolved the carbonates, and sesquioxide coatings on 

the primary minerals as evidenced by high concentrations of iron, 

aluminum, silica, and manganese. Iron concentrations as high as 

200 mg/1 were obtained, but this dissolved iron was eventually reprecipitated further on in the core when the pH of the waste rose to 5.5 

to 6.0 because of neutralization of the waste by aquifer carbonates 

and oxides. Exhaustive leaching of a core by the acidic waste quantitatively dissolved the aquifer carbonates and removed approximately 12 percent of the extractable iron.

Sorption of the waste organic compounds upon the aquifer mineral 

constituents was found for all the waste organic acids. Formaldehyde 

was not sorbed. Sorption increased as the pH of the waste decreased 

with the exception of phthalic acid. Phthalic acid was complexed 

with dissolved iron, and its concentration decreased as the pH of the 

waste increased because it coprecipitated with the iron hydroxide 

precipitate. The waste solution was supersaturated with respect to 

terephthalic acid, and this constituent was found to be both highly 

adsorbed and precipitated in the core.

At the conclusion of this study, a conceptual model was constructed which by combining the results of the field and laboratory 

studies, detailed the various stages of injected waste reactivity and 

movement in the subsurface from the injection well to the edge of the 

waste front. The excessive pressure build-up in the injection wells 

was thought to be the result of a number of factors: reprecipitation of 

aquifer constituents initially dissolved by the acidic waste, precipitation of terephthalic acid, formation of carbon dioxide and methane 

gases, and the relatively low permeability and porosity of the injection zone. The leak problems were thought to arise from the dissolution of the cement grout around the casing by the waste acids of the 

injection wells and certain observation wells.

INTRODUCTION

Injection of liquid wastes into subsurface strata is a 

concept in waste management which has found widespread use in industry only since 1960. A recent survey 

by Warner and Orcutt (1973) noted that only 22 waste 

injection wells were constructed before 1960, and by 

1964, the number of injection wells had doubled. In 

spite of growing opposition to subsurface waste injection because of its largely unknown long-term environmental effects, the number of waste-injection 

wells has continued to increase until there are presently (1973) about 278 industrial waste-injection wells 

which have been constructed in 24 states. Wells used to 

reinject brines brought to the surface during oil and 

gas production were not included in this survey. In 

1973, chemical, petrochemical, and pharmaceutical 

companies accounted for 57 percent of the industrial 

waste-injection wells.

This study is part of a nationwide effort by the U.S. 

Geological Survey to evaluate the environmental effects of subsurface waste injection. The specific objectives of this study were to: (1) Predict the reactions and 

interactions between certain organic wastes and 

aquifer components when organic wastes are placed in 

the subsurface environment and (2) define the effects 

that physical, chemical, and biological reactions have 

upon the distribution and movement of organic wastes 

in the subsurface.

In January 1971, the subsurface waste-injection system operated by Hercules Inc. near Wilmington, N.C., 

was selected for study. The site had several distinct 

advantages for this study: First, the industrial waste 

being injected into the subsurface contained high concentrations of several water-soluble organic compounds which were liable to react and be transformed 

in the subsurface environment. Prior to this study, 

problems with an injection well pressure build-up after 

a period of waste injection indicated that the reactivity 

of the injected waste with the injection zone was an 

important aspect concerning the operation of this 

waste-injection system. Secondly, a network of 14 observation wells located at various distances from the 

injection wells, and drilled to different depths, enabled 

the monitoring of waste movement and the collection 

of waste samples in both horizontal and vertical directions from the points of waste injection. Third, the 

relatively shallow depth to the waste-injection zone 

(1,000 feet or 300 metres) facilitated chemical and microbiological experimentation under the simulated 

pressures of the injection zone without the use of very 

high pressure equipment. Last but not least, excellent 

cooperation and support was provided by the Company 

and various state and federal agencies.

Disadvantages of this site were that the two injection wells and complex hydrogeologic nature of the 

injection zone made it very difficult to predict the rate 

and direction of waste movement. Therefore, no attempt was made to model the hydrological effects of 

waste injection. Second, because this study was initiated after the waste-injection system was planned, 

constructed, and brought into operation, there was no 

chance to influence the design, construction, placement, coring, and logging of the injection and observation wells which might have increased their utility as a 

research facility.

At the inception of this study, it was recognized that 

an interdisciplinary approach, which included organic 

chemistry, inorganic chemistry, microbiology, and 

hydrogeology, was necessary to understand and describe the several aspects of subsurface organic waste 

injection. Therefore, in this report, the organic and 

inorganic chemistry is the work of the authors; the 

microbiology and the hydrogeology are based on the 

work of others. (See section, "Acknowledgments".)

The Hercules Inc. plant is located on the Atlantic 

Coastal Plain approximately 4 miles northwest of 

Wilmington, N.C. A photograph of the plant is shown 

in figure 1, and its location is shown on the map of 

figure 2. The product of the plant is dimethyl 

terephthalate (DMT), which is used in the production 

of synthetic polyester fibers. The organic byproducts of 

DMT manufacture were injected into the subsurface 

from May 1968 until December 1972.
INTRODUCTION

a 

B0>

K

CJ 

S5

e

o> 

K
SUBSURFACE ORGANIC WASTE INJECTION, NORTH CAROLINA

77° 30'

10 KILOMETRES

 Area of report

FIGURE 2. Location of Hercules Inc., plant site.

When this study was initiated in January 1971, the 

first injection well had been abandoned because of low 

input at maximum permitted pressure, and the drilling of the second injection well was under way. The 

first step of this study was to predict the chemical and 

microbial reactions which were probably occurring in 

the waste after injection. The predictions and some of 

the initial findings were given in a report to the Institute of Environmental Sciences (Leenheer and Malcolm, 1973a). A sampling and analytical program 

based on the hypothesized reactions was instituted, 

and additional findings were presented before the Second International Symposium on Underground Waste 

Management and Artificial Recharge (Leenheer and 

Malcolm, 1973b). Reports on the microbiological aspects (DiTommaso and Elkan, 1973) and a concurrent 

study on hydrogeological aspects (Peek and Heath, 

1973) were also presented before this symposium.

Other reports which cover a period prior to and concurrent with this study are a status report by the 

North Carolina Department of Water and Air Resources (1971), and an engineering report on the injection well system by Black, Crow, and Eidsness, Inc. 

(1971). A discussion of the geology and ground-water

hydrology of the Wilmington area is in a report by 

LeGrand(1960).

ACKNOWLEDGMENTS

The original interest and counsel of Raymond L. 

Nace, and the late Charles L. McGuinness, were beneficial in establishing goals and providing direction during the initial stages of this study. Leonard A. Wood 

provided direction during the middle and latter stages 

of this study.

Dr. Gerald Elkan and Anthony DiTommaso conducted the microbiological studies at the Department 

of Microbiology, North Carolina State University, 

Raleigh. Their work was financed in part by the U.S. 

Geological Survey. Harry M. Peek, Chief, Ground 

Water Division, North Carolina Office of Water and 

Air Resources, and the North Carolina Board of Water 

and Air Resources were very helpful in facilitating the 

conduct of this study, and providing historical and 

background information. The drilling of the observation wells and the hydrogeological studies at the 

waste-injection site resulted from waste-monitoring 

requirements of the Office of Water and Air Resources. 

Ralph C. Heath, U.S. Geological Survey, Raleigh, N.C., 

gave valuable assistance in coordinating the efforts of 

the authors with the company, state, and federal agencies. He also assisted in the interpretation and writing 

of the hydrogeological study. Much of the material 

contained in the hydrogeology, case history, and microbiology sections of this report was previously published (Peek and Heath, 1973; DiTommaso and Elkan, 

1973), and is reproduced in this report with the permission of the authors and the American Association of 

Petroleum Geologists.

Issac J. Winograd, U.S. Geological Survey, Reston, 

Va., assembled and organized data and records which 

predated the beginning of this study.

The cooperation and assistance of officials at Hercules Inc., Frank Parkinson, plant manager, J. Gale 

Wendle, Jr., and Al Lister, technical superintendents, 

and John Humphries, chemical engineer, are greatly 

appreciated. Charles Sever, consulting geologist with 

Black, Crow, and Eidsness, Inc., supplied the well logs 

and served as a consultant to Hercules Inc. on the well 

engineering and geohydrology at the injection site. Dr. 

Louis Adcock, Professor of Chemistry at the University 

of North Carolina at Wilmington, periodically collected samples at the injection site regardless of 

weather conditions and other obstacles.

Donald F. Goerlitz, U.S. Geological Survey, Menlo 

Park, Calif., lent invaluable aid and experience to the 

organic analysis phase of this study. Everett A. Jenne 

and Vance C. Kennedy, U.S. Geological Survey, Menlo 

Park, Calif., provided analytical assistance in trace-
HYDROGEOLOGY

metal analysis. Donald W. Fisher, U.S. Geological 

Survey, Reston, Va., determined dissolved gases in the 

water samples.

HYDROGEOLOGY

By H. M. PEEK and R. C. HEATH

The Wilmington Area is underlain by coastal-plain 

sedimentary units more than 1,000 ft (305 m) thick. 

The sediments are predominantly of Late Cretaceous 

age and include ascending the Cape Fear, Middendorf, 

Black Creek, and Peedee Formations. The Castle 

Hayne Limestone of Eocene age overlies the Peedee in 

much of the area, but does not extend as far west as the 

Hercules site. Undifferentiated sands (probably of 

Pleistocene age), about 75 to 100 ft (23 to 30 m) thick, 

overlie the Cretaceous strata at the Hercules site. As 

shown in figure 3, these units generally consist of interbedded sand, silty sand, clay, and some thin beds of 

limestone. The sediments are fine grained, with clay 

the predominant lithic unit. The beds of sand are thin 

and generally fine grained.

The surficial sand is the only freshwater aquifer 

beneath the site. The sand is very permeable and is a 

productive source of water. The rate of recharge is high 

as most of the precipitation enters the sand. Individual 

wells yield about 300 gal/min (1,136 1/min), and the 

total withdrawal at the site is more than 6 million 

gal/day (23 million I/day).

There are several relatively permeable artesian

aquifers in the Cretaceous sediments, but none are 

very productive and all of them contain brackish water. The principal aquifers occur at depths of 300 to 350 

ft (91 to 107 m), 475 to 500 ft (145 to 152 m), 660 to 700 

ft (201 to 213 m), 850 to 1025 ft (259 to 312 m), as 

indicated in figure 3.

The "300-ft" zone was sampled and the head was 

measured at several well sites during construction. 

Well 13 is the only well completed in this zone. The 

water from this well had a chloride concentration of 

2,600 mg/1. The head is about 29 ft (8.8 m) above sea 

level.

No wells have been constructed in the "500-ft" zone; 

however, samples for water analysis were collected 

during construction of wells 14 and 15, and the 

chloride concentration of water from this zone was 

near 7,000 mg/1. The artesian head was not measured.

Three wells have been constructed in the "700-ft" 

zone and, in addition, water-quality and water-level 

data were obtained during the construction of deeper 

wells. The chloride concentration of the water in this 

zone is about 10,000 mg/1 and the natural head in this 

zone was about 38 ft (12 m) above sea level.

The zone between depths of 850 and 1,025 ft (259 to 

312 m) is the injection zone. The water from this zone

eologic 

log

Chloride Water Injection well 

(mg/1) level I-7A

100 - - 30

200

300

60

90

120 D -T. ^~- V> .r-_j-_ 

Q 

Z

(ref LS)

^^JT_~

:-i-i-i

~ir~-jr_r

"LJ~Ln-T

 -

-Z-iHr

rs ?:

~u~_~^r

_ -

>I-I-I

_ri-~T_~i

 

-Z-I-ir

^"_r"_r^

J~_TT_~

^_~~ ~

-_ _r~.r

^S^"-

J^J^_~

f'^o'%".

_ _ _

~-I~-^~ 

I-IrC-:

_-^r^r^

~-^^r^_r

5-V:;':|:.:':V?

r^riHf

_-_-_-

6

O

0

to

CN -h

0

0

o

^h

o

o

o

0

±

o

o 

q

CN

-12

+8

o

CN

±

into

|

^

XXXXXXXX

/,

yy

><

%

/.\

y

/,

^

I

y

'y

y

y

y,

^

y

y

y

y

y

^J|

^

^-s-_

~h~l Concrete pad

1^ Cement grout

X 18" Steel pipe

|

\

X

X

>^ Central izers

^

^N* n

 ^ 6 Stainless steel pipe

\

X

^

^ n

^ 12 Steel pipe

I

I

V

X

\ Cement grout

^

|

^

^

V

V

\

 X Stainless steel and

X Teflon packer

^ 

 V Stainless steel screen

*

- Gravel pack

=>

~J

500--150 r -------

LU -_-^_ _-

U) .^ ^ ^

600--180" :-I-£H 

cc(- _ _ _

UJ _ _ _

5 -_~~_r~_r

700--210 «^>:K in m

800 - - 240 -_-_J--Z

900 - ~ 270

1000 - - 300 

1010TD

EXPLANATION

FIGURE 3. Diagram showing hydrogeologic conditions and 

injection-well construction for well I-7A.

has a chloride concentration of nearly 12,000 mg/1. The 

artesian head in this zone is unusually high, about 65 

ft (20 m) above land surface at the site, or about 90 ft 

(27 m) above sea level. This zone was selected for waste 

injection for reasons of its greatest depth below the 

fresh ground-water zone, the high salinity of the 

ground water in this zone, and permeability which 

would permit waste injection at the rate of 200 gal/min 

(7571/min).

The artesian conditions appear to be regional as indicated by the presence of freshwater to only very shallow depths over a large area along the Cape Fear arch, 

as first observed by LeGrand (1955), and more directly 

by recent exploration. The injection zone and the thick 

overlying confining bed are identifiable in a well near
SUBSURFACE ORGANIC WASTE INJECTION, NORTH CAROLINA

Calabash, about 45 mi (72 km) southwest of the Hercules site, which is approximately along the line of 

strike. The elevation of the artesian head is about 100 

ft (30 m) above sea level at Calabash. The water from 

this well has a chloride concentration of about 4,000 

mg/1. The artesian head of a well completed at a depth 

of about 650 ft (198 m) at the Calabash site has an 

elevation of about 35 ft (11 m) above sea level, and the 

water has a chloride concentration of about 650 mg/1.

The aquifer serving as the injection zone at the Hercules site consists of multiple layers of sand, silty sand, 

clay, and some thin beds of limestone. The overall 

permeability of this section, which is about 150 to 175 

ft (45 to 43 m) thick, is very low although the permeability of the salty zones is relatively high. A temperature survey indicated that much of the waste entered a 

thin subzone at a depth of about 1,000 ft (305 m) in the 

initial injection well (1-6).

No long-term pumping test was made on the injection well prior to placing the system in operation. The 

injection rates fluctuated so greatly during the initial 

injection period that the data cannot be used to 

evaluate the hydraulic characteristics of the sub-zones. 

Tests on wells drilled later could not be made properly 

as the system was in operation and injection rates were 

not stable.

The high artesian pressure, particularly in the deeper aquifers, the generally low permeabilities of the 

aquifers, the thick zones of clay and silty sands, and 

the shallow depth to brackish water suggest slow 

natural circulation of water in the Cretaceous beds.

CASE HISTORY OF WASTE INJECTION

A chronology of the significant events which occurred during the four and one-half years of waste 

injection is given in table 1. A map showing locations 

of injection and observation wells is given in figure 4.

INSTALLATION AND OPERATION OF INITIAL 

WELLSYSTEM

The initial well system consisted of one injection 

well (1-6) and four observation wells (numbers 1, 2, 4, 

and 5) completed at a depth of about 855-1025 ft 

(260-312m). Well 3 was completed in the first aquifer 

above the injection zone at about 660-690 ft (201- 

213m) depth. The wells were cased with a special 10-in. 

(250-mm) diameter fiberglass casing and equipped 

with stainless steel screens of 6-in. (150-mm) diameter. 

The screens were set at the depths shown in table 2. 

The deep observation wells were equipped with plastic 

sampling tubes extending from the wellhead to the 

injection zone. Each well was equipped with a pressure 

gage on the wellhead and a manometer located at a 

central station. As shown in figure 4, the observation 

wells were only located at a maximum distance of 150

ft (45 m) from the injection well, which was too close to 

indicate the magnitude and pattern of pressure change 

or to permit a reliable measurement of the travel time 

of the waste.

The injection of waste into the system was begun in

TABLE i. Chronology of significant events during waste injection

Date Event

May 1968 Injection well 1-6, and observation wells 1, 2, 4, 

and 5 completed to 1,025-ft depth. Observation 

well 3 completed to 700-ft depth.

May 1968 Waste injection begun through injection well 1-6. 

September 1968 Waste was detected in wells 1,2,4, and 5.

June 1969 Waste injection shifted from well 1-6 to wells 4 and 

5 because of excessive injection pressures in well 1-6.

November 1969 Injection well 1-6 damaged during an attempt to 

reclaim the well. Waste injection continued 

through well 5.

December 1970 Observation well 8 completed to 700-ft depth. 

January 1971 Observation well 9 completed to 700-ft depth.

February 1971 Leakage of waste into the 700-ft zone was detected 

at well 3.

April 1971 Injection well I-7A was completed to 1,050-ft 

depth.

May 1971 Waste injection shifted from wells 4 and 5 to well 

I-7A.

May 1971 Observation wells 7 and 11 completed to 1,050-ft 

depth.

May 1971 Wells 1 and 1-6 were cemented to stop wasteleakage into the 700-ft zone.

June 1971 Observation well 12 completed to 1,050-ft depth.

October 1971 Waste injection renewed through well 4 because 

well I-7A was not accepting all the waste at the 

specified injection pressure limit.

November 1971 Observation well 13 completed to 300-ft depth.

December 1971 Waste detected in well 9 indicated waste leakage 

into the 700-ft zone in that area.

December 1971 Pressure decrease in well 5 indicated possibility of 

waste leakage into an aquifer above the injection zone.

March 1972 Pressure decrease in well 2 indicated possibility of 

upward leakage of waste.

May 1972 Observation wells 14,15, and 16 were completed to 

1,050-ft depth.

June 1972 Waste was detected in well 14, and a weekly sampling program was instituted to monitor the 

passage of the waste front.

October 1972 Wells 2 and 5 were cemented to stop waste-leakage 

into the 700-ft zone.

November 1972 Waste injection was gradually phased over to surface treatment of the waste.

December 1972 Waste injection terminated.

January 1973 Waste disappeared from well 14 after injection 

termination.
CASE HISTORY OF WASTE INJECTION

TABLE 2. Injection-system well data

Well 

No.

1

2 

3

4

Purpose

Observation 

Observation 

Observation 

Observation

Date drilled 

(mo-day-yr)

6-1-67 

7-27-37 

8-8-67 

3-13-68

Total 

depth (ft)

1,025 

1,025 

690 

1,025

Screened 

interval (ft)

855-1025 

855-1025 

660-690 

854-1025

Water Level1

93 

93 

40 

93

Remarks

Abandoned 5/71 

Abandoned 10/72

Also used as injection

Observation 1-27-68 1,025 854-1025

well 6/68-8/68 and 

10/71-12/72

93 Also used as injection

well 6/68-5/71. Abandoned 

10/72

6

7

7A

8

9

11

12

13

14

15

16

Injection

Observation

Injection

Observation

Observation

Observation

Observation

Observation

Observation

Observation

Observation

2-3-68

5-7-71

4-29-71

12-3-70

1-28-71

5-28-71

6-23-71

11-16-71

5-23-72

5-23-72

5-23-72

1,025

1,040

1,110

709

743

1,043

1,015

300

1,010

1,030

1,010

855-1025

805-1036

830-1008

694-704

727-737

855-1035

838-974

283-293

843-972

843-977

843-983

93

111

195

41

32

127

150

29

Abandoned 5/71

'In feet above mean sea level on date drilled. Water levels need to be considered in light of iiyection history.

the latter part of May 1968 by intermittently injecting batch quantities at a rate of about 200 gal/min 

(757 1/min). As the volume of waste increased and the

\

i-6 0

75 150 FEET

0 20 40 METRES

0 1000 2000 FEET 

I I

0 300 600 METRES 

EXPLANATION

Injection well 

Observation well

Observation well used

as injection well 

Plant location Lat 34° 19* N.; 

Long 77° 58' W.

FIGURE 4. Map of waste-injection and observation wells.

periods of injection lengthened, the pressure rose 

sharply in the injection well and in the aquifer. The 

average monthly injection rate and the highest wellhead injection pressures, measured monthly or more 

frequently, are plotted on the graphs in figures 5 and 

6 and reflect the early history of the system.

By September 1968, the waste was detected in samples collected from all existing observation wells 

(wells 1,2,4, and 5) in the injection zone. Only pH and 

dissolved solids were determined on samples collected 

during the passage of the waste front through the 

observation wells. There were no determinations of 

any gas constituents evolved from subsurface waste 

reactions, and no measurement of organic waste content. By May 1969, pressure in the injection well had 

reached the equivalent of 400 ft (91 m) above sea 

level, and about 165 ft (50 m) in the observation wells.

WELLS USED FOR WASTE INJECTION

220

2OO

MINUTE

CD 0)O 

I

2 

O

< 12O

O

100 

80

I -6 -J-4& 5 5

-

-

-.

",

p

:

-

;

-

, :

 ?u.5<5-^-?< wO2Q

1969

I-7A I-7A+4

-

T

n

T

- ',

seiiltils;

197O

'- r

-j -

"

-

r

r

1

:o-!?"s<STT<wO2c

1971

1 n

-

^ ~

 S:'-"

 i£ 5 < S ? T < w 0 I Q

1972

FIGURE 5. Monthly average injection rate. Injection ceased December

1972.
SUBSURFACE ORGANIC WASTE INJECTION, NORTH CAROLINA

INJECTION PRESSURE IN FEET ABOVE LAND SURFACE 

200 300 400

Shifted injection from well 4 to well 5 

Injection well (6) out of service

FIGURE 6. Graph of highest wellhead injection pressures.

Figure 7 shows the oval pattern of the pressure surface in the injection zone in January 1969 which 

suggested the greatest waste movement to the northwest from well 1-6. The injection pressure continued 

to rise to a high of more than 450 ft (137 m) by June

1969. 

Because of the pressure build-up in the injection

well, it was not possible to continue injection of waste 

at the rate of 300,000 gal/day (1,136,000 I/day), without exceeding the allowable limits of 150 psi (10.3 

bars) specified by the injection permit. As the observation wells were of limited benefit after the waste 

had passed, the North Carolina Board of Water and 

Air Resources granted permission to the company for 

injection of the waste through wells 4 and 5 as an 

emergency measure to allow the plant to continue 

operating.

In November 1969, an attempt was made to reclaim 

the injection well by replacing the screened section, 

but this reclamation attempt was not successful and 

apparently damaged the casing because of subsequent

50 

I

I 

10

\^

20

100 FEET

I 

I 

30 METRES

EXPLANATION

 Injection well

A Observation well injection zone 

A Observation well 700-foot zone 

5 Upper number is well number

153 Lower number is altitude of the pressure surface; in feet above mean 

sea level. Contour interval variable

FIGURE 7. Location of wells in initial system and pressure surface, 

January 1969.

waste leakage at this well. The pressure surface in 

late September 1970, is shown in figure 8. Well 6, the 

injection well, was out of service and well 5 was serving as the injection well. As may be noted, the low 

pressure at well 1-6 indicates leakage from the injection zone through this well. In February 1971, a sudden pressure increase was noted in well 3 which is 

screened in the aquifer at a depth of 660-690 ft (201- 

210 m) and one month later in March, waste was 

detected in this well.

A caliper log taken in May 1971 just prior to the 

cementing, the injection well 6 showed a break in the 

casing of the well near 500 ft (152 m) depth. Apparently leakage of the waste had occurred for a long 

period of time into the aquifer at a depth of 500 ft 

(152 m). This leakage had not been detected previously 

because of the absence of wells in the zone. A sonic log 

taken at this time indicated poor bonding between the
CASE HISTORY OF WASTE INJECTION

cement casing and the formation between the injection 

zone and the 700-ft zone; therefore, the leak into the 

700-ft zone most likely originated from the injection 

zone with the waste rising into the 700-ft zone around 

the outside of the well casing (C. Sever, oral commun., 

1973). Well 1 in addition to injection well 6 was sealed 

with cement in May, 1971 because low pressure in well 

1 indicated possible waste leakage also at this point. 

After cementing, the leakage apparently stopped because the pressure in the 700-ft zone returned to normal within a few weeks, with most of the decline occurring within hours.

A request by the company to double the waste injection rate from 300,000 gal/day to 600,000 gal/day was 

denied by the North Carolina Office of Water and Air 

Resources in March, 1970. After a review of the operao 50 100 FEET

I

I 

10

I 

0 10 2020 30 METRES 

EXPLANATION

 Injection well out of service 

A Observation well injection zone 

A Observation well 700-foot zone 

5 Upper number is well number

153 Lower number is altitude of the 

pressure surface; in feet above 

mean sea level. Contour interval 

10 feet

FIGURE 8. Map of pressure surface, September 1970.

tion of the system, in July 1970 the North Carolina 

Office of Air and Water Resources concluded that the 

operation of the system had not been successful, and 

that continued waste injection would require the installation of at least one new injection well and a 

larger network of observation wells.

CONSTRUCTION AND OPERATION OF 

EXPANDED INJECTION SYSTEM

The second injection well, I-7A, was drilled approximately 2,500 ft (762 m) northeast of injection well 1-6 

(fig. 9). The second injection well was to be located at 

the present site of observation well 7; however, the 

permeability was too low for injection at this site and 

well 7 was completed as an observation well. During 

the development of well I-7A, waste and gas were 

pulled into the well. The gas was accidentally ignited 

by welding equipment, and later analysis by Hercules 

Inc. indicated the gas to be predominantly methane. 

Identification of formic acid in water samples confirmed the presence of waste.

Waste injection through well I-7A began in May 

1971 at an average rate of 120 gal/min (454 1/min), and 

injection of waste through well 5 ceased. By October 

1971, this new well was not accepting all the waste 

within the specified pressure limit, and waste injection 

was resumed in well 4. Waste injection continued 

through both well 4 and injection well I-7A until the 

termination of injection in December, 1972.

The spacing of the second observation-well network 

installed to monitor waste movement from both the old 

and new injection wells was 10-15 times the distance 

used in the original network. Observation wells 11,12, 

14, 15, and 16 were installed during the period from 

May 1971 to May 1972, to monitor pressure and waste 

movement in the injection zone. Observation wells 8 

and 9, which were completed into the 700-ft (213 m) 

aquifer, were operational when the second injection 

well was completed.

In December 1971, waste was detected in well 9 

concurrent with an increase in pressure, indicating the 

leakage of waste into the 700-ft aquifer at the new 

injection site. This leak apparently was through the 

annular space around the casing of well I-7A. Pressure 

decreases in well 5 during December 1971, and in well 

2 during March 1972, indicated that these wells also 

had possibly become channels for leakage of the waste 

into shallower zones. Wells 2 and 5 were later sealed 

with cement to prevent leakage, but well I-7A has not 

yet been sealed (April, 1974).

Figure 9 shows the well system, the reduced pressure surface of the injection aquifer, and the approximate limits of waste travel in October 1972. At this 

time, the areal extent of the waste in the subsurface 

does not coincide with the pressure surface because 

although the major quantity of waste was injected
10 SUBSURFACE ORGANIC WASTE INJECTION, NORTH CAROLINA

through wells 1-6, 4, and 5, the highest injection pressure at this time was at well I-7A thus biasing the 

pressure surface to the northeast of the wastecontaminated area. The waste had apparently passed 

well 14, about 1,500 ft (457 m) north of the initial 

injection site, by the time it was completed, and also 

had passed well 15, about 3,000 ft (914 m) west of the 

initial injection site. During August 1972, the waste 

was detected in Well 11 as indicated by the dissolved 

organic carbon (DOC) content, which has proved to be

1000 2000 FEET 

__I I ^ i r

0 300 600 METRES 

EXPLANATION

 Injection well

A Observation well Injection zone

A Observation well 700-foot zone

O Observation well 300-foot zone

© Observation well used as injection 

well

 Original system

 Approximate limits of waste travel

 160 Pressure-surface contour

 -J40 -- Estimated pressure-surface contour

124 Upper number is altitude of the pressure surface, in feet above mean 

sea level. Contour interval 20 or 

40 feet

7 Lower number is well number

FIGURE 9. Map of pressure surface and approximate limits of waste 

travel, October 1972.

the best index for monitoring waste movement in the 

subsurface at this site.

In July 1971 the North Carolina Office of Air and 

Water Resources stipulated that the waste-injection 

permit would not be extended beyond the July 1,1973 

deadline. Therefore, in November 1972, a conventional 

surface waste-treatment facility was completed by the 

company and the injection of the waste was gradually 

reduced as the new facility was placed in operation. 

During December 1972, injection of waste ceased, although injection of freshwater continued at a rate of 

about 15-20 gal/min (57-76 1/min) in both wells I-7A

o 1000

I

2000 FEET

I ^ 1 I

0 300 600 METRES

EXPLANATION

Injection well

Observation well Injection zone 

Observation well 700-foot zone 

Observation well 300-foot zone

© Observation well used as injection 

well

 Original system

 7 15 Pressure-surface contour

 - 100 - Estimated pressure-surface contour

5 Lower number is well number

116 Upper number is altitude of the 

pressure surface, in feet above 

mean sea level. Contour interval 5 feet

FIGURE 10. Map of pressure surface with no injection, April 1973.
FIELD SAMPLING METHODS 11

and 4 to maintain both wells operable in case they 

would be needed for waste injection before July 1973. 

Injection of freshwater was stopped for a period of 

about 9 days in March and April 1973, and figure 10 

shows the pressure surface of the aquifer at the end of 

the 9-day period. Freshwater injection ceased in May 

1973. At present (April 1974), waste injection through 

wells is prohibited by law in North Carolina.

FIELD SAMPLING METHODS

The collection of ground-water samples can best be 

explained by first considering the construction of observation well 14 as shown in figure 11. The construction of this well is representative of most of the observation wells which are completed in the injection zone. 

Because the natural artesian head of the water in the 

injection zone is about 65 ft (20 m) above land surface, 

water samples were collected by simply opening the 

valve at the top of the plastic sampling tubing. The 

small diameter (64 mm ID) sampling tubing enabled 

collection of a representative water sample after only a 

30-minute flush period with minimal wastage discharge of ground water. Roughly three void volumes of 

water pass through the plastic sampling tube at a flow 

rate of 1,200 ml/min during the 30-minute flush period. The twin sampling tubes were placed for the purpose of water collection from the well in the center of 

the screened injection zone at 935 ft (285 m) depth and 

from above the screened zone at 822 ft (251 m). Water 

samples obtained from above the screened section of 

the observation well were of little value as they did not 

represent water present in the injection zone. A 3-foot 

section of tygon tubing was connected to each outlet of 

the two sampling valves to facilitate sample collection.

Sampling methods were designed to be applicable to 

uncontaminated ground water as well as the concentrated waste for both organic and inorganic parameters. Dissolved organic carbon (DOC) was used to estimate the waste concentration because it is a quantitative organic parameter, and most of the organic waste 

constituents are water soluble. Water samples for DOC 

were pressure filtered on site immediately after collection through a silver membrane filter with 0.45-Aim 

(-micrometre) porosity. The DOC sample was collected 

in a 50 ml glass serum bottle sealed with an 

aluminum-foil-covered rubber septum stopper. An extensive discussion of the merits of the DOC parameter 

and the method of DOC sample collection is given in a 

paper by Malcolm and Leenheer (1973).

Two samples were collected for standard inorganic 

water analysis: one litre of filtered water acidified to 

pH 2 with nitric acid for analysis of the cations, Al, Ca, 

Fe, K, Na, Mg, and Zn; and one litre of filtered nonacidified sample for analysis of the anions, Cl, F, SO.*,

Valve for 

lower sample

4 Gate valve

Valve for 

upper sample

%" OD X % ID 

Impolene tubing

20' of % "stain less 

steel pipe

2 PVC screen

2 PVC pipe

Silica sand

Guide plug, back 

pressure valve and 

wash plug assembly

3%" hole

FIGURE 11. Construction features of observation well 14.

NO2-NO3, and SiO2. The water was pressure-filtered 

on site through a vinyl metricell membrane filter of 

0.45-/mi porosity in a plexiglass filtration assembly 

(Skougstad and Scarbro, 1968). Compressed carbonfree nitrogen was used to pressurize the filter because 

ferrous iron will oxidize and precipitate as ferric hydroxide during filtration if air is used to pressurize the 

filter. Both the acidified and non-acidified samples 

were collected in acid-washed, 1-litre polyethylene bottles.

A filtered 1-gallon (3.8-1) sample for trace elements 

was collected in an identical manner as the sample for 

standard inorganic analysis. After collection in an 

acid-washed, gallon plastic jug, high purity nitric acid
12 SUBSURFACE ORGANIC WASTE INJECTION, NORTH CAROLINA

was added to acidify the sample to pH 2. The amount of 

nitric acid pipetted into the sample was recorded for 

the purpose of acid blank analyses.

The last type of water sample collected was a litre of 

unfiltered sample which was used to characterize the 

organic compounds. This sample was not filtered because filtration may introduce low-level adsorption 

and contamination problems, and filtration will also 

remove organic compounds of low solubility which are 

adsorbed and occluded on sediments. This sample was 

collected in a litre glass bottle previously heated to 

350°C (Celsius) to free it of organic contamination, and 

was sealed with a metal screw cap with a teflon liner. 

After collection, the glass bottle was placed in a molded 

styrofoam packer for shipment, and was chilled in 

crushed ice to minimize sample degradation. Blank 

samples of uncontaminated ground water were collected as well as waste-contaminated samples to test 

for the presence of organic compounds such as phthalate esters originating from the plastic sampling tubing. Organic contamination arising from the sampling 

tubing did not prove to be a problem in comparison 

with the high concentrations of organic waste constituents in the contaminated ground water.

When gas was present in the observation wells, gas 

which effervesced from the ground water because of 

changes in pressure, temperature, and solubility, was 

collected in the following manner. The outflow from 

the tygon outlet tube was directed into an inverted 

100-ml graduate cylinder filled with water, and the 

rate of gas collection was determined over a timed 

period at a measured flow rate. After measurement of 

the rate of gas effervescence, the inlet of a 250-ml 

cylindrical glass gas collector tube was attached to the 

tygon outlet tube, and the well water was allowed to 

flow through and displace the air in the collector tube 

which was held in the vertical position with both the 

inlet and outlet stopcocks open. After all the air was 

displaced, the gas collector tube was placed in the horizontal position, and well water was allowed to flow 

through the tube until 5 to 10 ml of gas had been 

collected in the upper portion of the tube. The gas and 

water were sealed in the tube by simply closing the 

inlet and outlet stopcocks.

After all the samples were collected, measurements 

of pH, alkalinity, and specific conductance were performed on site. Alkalinity was determined by titrating 

the water sample with standard acid to pH 4.5.The 

water samples were shipped air freight to Denver in a 

large ice chest filled with crushed ice. Most of the 

organic analyses were performed by the authors. The 

gas samples were sent by parcel post to the U.S. 

Geological Survey, Washington, B.C. where Donald W. 

Fisher performed the gas analyses. The samples for 

standard inorganic analysis and trace metal analysis

were shipped to the Geological Survey's Central Laboratory, Salt Lake City, Utah. The samples were collected on a periodic basis by trained observers at the 

site.

INDUSTRIAL WASTE ANALYSIS

ORGANIC ANALYSIS

The major emphasis in the industrial waste analysis 

was upon the organic analysis because the chemical 

constituents of the waste were predominantly organic 

in nature. An analysis of the organic waste and 

methodology were used whereby one could test for the 

presence or absence of these organic waste compounds 

in waste-contaminated ground-water samples. Comparisons of the organic analyses of waste-contaminated 

ground water sampled at various points in the subsurface with the organic waste analysis indicated what 

reactions and transformatins were occurring between 

the waste and the injection zone for different periods 

after waste injection and for different distances of 

waste migration in the subsurface. The organic waste 

constituents are thought to be more reactive than the 

inorganic waste constituents because of ease by which 

they are transformed and broken down by microbiological reactions. Certain organic waste acids are thought 

to be active in the formation of organic-metal complexes, and thus injection of these organic complex-forming 

compounds causes the translocation of inorganic 

aquifer constituents.

The parameter used to quantify organic waste concentrations was DOC which is defined as that portion 

of total organic carbon which passes through a silver 

membrane filter of 0.45-/xm porosity. DOC was determined on the total carbon channel of a Beckman 915 

Carbon Analyzer1 after inorganic carbon had been removed from the sample by acidifying with phosphoric 

acid followed by nitrogen gas purge. Losses of volatile 

organic carbon during the nitrogen gas purge were 

found to be minimal for the water-soluble organic 

waste constituents.

A number of analytical methods were used to identify and quantify the organic waste constituents such 

that nearly all of the organic carbon in the waste was 

accounted for. The analytical scheme used to separate 

and identify organic waste constituents is given in 

figure 12. The recovery and efficiency of each step in 

the analytical scheme was measured by determining 

the DOC which was separated or remained in the 

waste solution.

Steam distillation was used to separate acetic and 

formic acids from other dissolved constituents. A 

100-ml sample acidified to pH 1 with sulfuric acid was 

steam distilled until 200 ml of condensate was col1 The use of brand names in this report is for identification purposes only and does not 

imply endorsement by the U.S. Geological Survey.
INDUSTRIAL WASTE ANALYSIS 13

lected. Recovery studies with acetic and formic acid 

standards indicated that 55 percent of the acetic acid 

and 45 percent of the formic acid was steam distilled. 

The pH of the distillates was adjusted to pH 10 with 

sodium hydroxide to render the acetic and formic acids 

non-volatile, and the samples were concentrated by 

evaporation on a hot plate.

The concentrates were acidified with concentrated 

phosphoric acid and injected into a Varian Aerograph 

2700 gas chromatograph equipped with a flame ionization detector. The column was glass (4 ft x 2 mm I.D.) 

and was packed with 100/120 mesh Porapak Q coated 

with 3 percent phosphoric acid. The gas chromatogram 

showing the separation of acetic and formic acids is 

given in figure 13. Formaldehyde, methanol, and 

p-toluic acid in the waste were also found to be steam 

volatile, but these compounds did not interfere in the 

quantification of acetic and formic acid by gas 

chromatography. A more complete discussion of a new 

method for the gas chromatographic analysis of acetic 

and formic acid is given in a report by White and 

Leenheer (1975).

The majority of the organic waste constituents were 

identified and measured in ethyl ether extracts. A 

100-ml sample was first adjusted to an alkaline pH by 

adding 3-5g of sodium carbonate. Extractable bases 

and neutral compounds were then extracted by two 

successive 100-ml portions and followed by one 50-ml 

portion of ether. All of the extractions were performed 

in a 500 ml separatory funnel. The extracts were collected in a 250-ml Erlenmeyer flask and dried with 40 

g of anhydrous sodium sulfate for four hours. Organic 

acids were extracted in an identical manner using the 

same samples which were previously extracted for 

neutral and basic compounds after acidification to pH 1 

with concentrated sulfuric acid. Recovery studies using

WASTE SOLUTION

-^

mill

with NaOH

°VT°

Acidify with 

H,P04

1

ace ""

ac,d I

D, h : 

H.SO, solution

1 

Colorimetnc

ethvl formate 

1 

Dry with Na,SO,

Jl

p methyl benzyl

S£rzev,'h ¥ ,

ith ethyl ether

 if 

Water layer

AddH,sL,,.c, 

with ether

 if i

te T Ut °n (no",,? 

* organic a 

DrywithNa.SO, morganic

^ compoun

I 

Methylation 

with CH,N,

FIGURE 12. Analytical scheme of organic waste analysis.

A. Air

B. Formic acid (0.7 mg/ml)

C. Acetic acid (0.7 mg/ml)

(Attenuation-32X 10~ 12 ampa/mv)

-16 X 10 amps/mv 5 64 X 10 amps/mv 

1234

I_________I >_____|_________L 

TIME, IN MINUTES

FIGURE 13. Gas chromatogram of acetic and formic acids.

standards indicated that this ether extraction obtained 

86 to 98 percent of the compounds of interest in the 

gas-chromatographic analysis.

The ether extracts were concentrated by 250 ml 

Kuderna-Danish evaporative concentrators equipped 

with 3-ball Snyder columns. The concentrators were 

placed in a fluidized-bed sand bath at 69°C. A time 

period of 30 minutes was required to concentrate 250 

ml of ether to 5 ml. The ether concentrate containing 

the neutral and basic compounds was directly injected 

into the gas chromatograph for analysis. The concentrate containing the organic acids was esterified with 

diazomethane to produce the methyl esters of the organic acids. The methyl esters of the waste organic 

acids possessed sufficient volatility for gas-chromatographic analysis whereas the free organic acids, with 

the exceptions of acetic and formic acids, are nonvolatile. The methylation procedure using 

diazomethane is given in the Methods Manual for 

Analysis of Organic Substances in Water (Goerlitz and 

Brown, 1972, p. 37).

The majority of organic compounds extracted by
14 SUBSURFACE ORGANIC WASTE INJECTION, NORTH CAROLINA

ethyl ether were found in the acid extract. A 10 ft x 

2mm I.D. glass column packed with 10 percent diethyleneglycol succinate on Gas-Chrom Q was used to 

separate the esterified acids in the methylated acid 

extract. The gas chromatogram is shown in figure 14 of 

the esterified acid extract. Mass spectra were obtained 

on each peak of the gas chromatogram by using an 

equivalent column in a Finnigan GC-MS Model 150 

system. The mass spectra of methyl-p-toluate and dimethyl terephthalate shown in figure 14 is correlated 

with the gas chromatogram by the spectrum numbers. 

Spectrum numbers are points in the time of the analysis where complete mass spectra can be obtained in the 

GC-MS system. "Background spectra" were subtracted

80 

60

40

20 

°C

100 

80

60

40

20

0 

2

, , ,

A

- V

, , , I ,

) 20

I ' I 

2 4

\

1

-\

1

40

1 ' 1 't

,?

' '

V, ,

I ' ' '

1.

2. 

3. 

4. 

5. 

6.

I , i i

< ' I . .,.,,,,,.

Dimethyl methylsuccinate 

Methyl benzoate 

Dimethyl succinate 

Methy l-p-tol uate 

Dimethyl terephthalate 

Dimethyl phthalate

, , r".

60 80 100 120

SPECTRUM NUMBER

1 ' 1 

6 8

1 ' 1 ' 1 

10 12 14 

MINUTES

. | i I i , . i

Spectrum Number 68-65 

Methyl-p-to uate

-

-

- I

1

0 40

1.1

1

60 80 1C o 1:!0

' I

I

140

-

5

L I , , 1 1 l"fl

-

140 160 180

I ' I ' I 

16 18 20

-

-

-

-

I

1 ' 1 

160 180 2C 0

ATOMIC MASS/ELECTRONIC CHARGE

uu

80

60

20

0

2

1 1 I ' I ' I ' I I ' I

Spectrum Number 154-151 

 Dimethyl terephthalate

-

.lll.jl .

0 40

!, I ,J i

i

60

ill I,

III .i I il .. i ' i ' i

80 100 120

1 1

-

-

-

i i i

I ' I ' I 

140 160 180 20

ATOMIC MASS/ELECTRONIC CHARGE

FIGURE 14. Gas chromatogram and mass spectra of methylated-acid 

ether extract.

by the computer in the system to give the mass spectra 

of the pure component. Characteristic mass spectra 

fragmentation patterns were used along with appropriate standards to identify the organic compounds 

separated in the gas chromatograph. An electronic digital integrator was used to determine the peak areas 

of each organic component in the gas chromatogram. 

Quantitative analysis was accomplished by comparison of peak areas with standard curves.

The ether extract for neutral and basic compounds 

was injected on the same diethyleneglycol succinate 

column as was used for the methylated acids, and the 

gas chromatogram of this fraction is shown in figure

15. There were no basic organic compounds found in 

the waste, and the neutral compounds identified in the 

ether extract accounted for less than one percent of the 

organic carbon in the waste.

After comparing the quantity of organic carbon identified in the steam distillate and ether extracts with 

the total DOC found in the waste, only about 75 percent of the organic carbon was identified. Identified 

organic carbon was determined by summing the products of the concentration times the percentage carbon 

of the determined organic constituents. Because certain volatile compounds were lost during extraction 

and concentration, direct injection of the waste itself 

into a column packed with 10 percent Ethofat on 

Chromosorb W was used to identify and quantify 

methyl formate, methyl acetate, and methanol. The 

gas chromatogram of this separation is shown in figure

16.

A few organic compounds do not give a sufficient 

response on the flame ionization detector to be measured; therefore another analytical method must be 

employed. Formaldehyde is such a compound and its 

presence was suspected by its characteristic odor in the 

waste residue after the other organic components had

1. Dimethyl succinate

2. Methyl-p-toluate

3. p-Methyl benzyl alcohol

4. Methyl-p-formyl benzoat

5. Dimethyl terephthalate

FIGURE 15. Gas chromatogram of alkaline ether extract.
INDUSTRIAL WASTE ANALYSIS 15

1 I

Standards Waste 

sample

1. Methyl formate

2. Methyl acetate

3. Methanol

1 2

MINUTES

1 2

MINUTES

FIGURE 16. Gas chromatogram of neutral, volatile, waste constituents.

been removed by ether extraction and steam distillation. Formaldehyde was subsequently identified quantified by its color reaction with chromotropic acid 

(Bricker and Vail, 1950). None of the other organic 

waste compounds interfere in the formaldehyde determination. Formaldehyde was the last compound to 

be identified in the waste, and its inclusion with the 

other previously identified compounds accounted for 95 

percent of the DOC in the waste.

This scheme of organic analysis which was applied to 

the industrial waste prior to subsurface injection was 

also applied to ground-water samples which were contaminated by the injected waste. The only changes in 

the analytical scheme were that the initial sample size 

was larger and the degree of concentration was greater.

Three waste samples were collected during 1972-73, 

and the average analysis of these three samples is 

given in table 3. The data of the individual analyses 

are given in basic-data table 20. The DOC of these 

waste samples ranged from 6300 to 7800 mg/1; however, there were only minor variations in the relative 

concentrations of the various organic constituents.

All of the organic waste constituents can be thought 

of as reactants, impurities, byproducts, products, and 

(or) catalysts directly related to the industrial processes. The overall process at the Hercules plant is to 

oxidize p-xylene to terephthalic acid in the presence of 

methanol and acetic acid to give the primary product, 

dimethyl terephthalate (DMT). There is also a small 

formaldehyde plant which produces formaldehyde

from the oxidation of methanol. In the waste analysis, 

methanol is a primary reactant; benzoic acid and 

phthalic acid most likely result from the oxidation of 

toluene and o-xylene impurities in the p-xylene 

feedstock; p-toluic acid, p-methyl benzyl alcohol, and 

methyl-p-formylbenzoate are incomplete oxidation 

products of p-xylene oxidation; succinic acid, methylsuccinic acid, and propionic acid are probably the 

fragments resulting from cleavage of the aromatic ring 

during p-xylene oxidation; formic acid is a byproduct of 

methanol oxidation; formaldehyde, terephthalic acid, 

and dimethyl terephthalate are products; and acetic 

acid is a catalyst. The dimethyl terephthalate product 

is purified after p-xylene oxidation and methylation by 

distillation and recrystallization with the extraneous 

organic constituents going to the waste.

Most of the organic acids found in the waste exist in 

chemical equilibria with the methyl, monomethyl, 

and dimethyl esters. These esters were generally found 

only in trace quantities in the waste because the aqueous waste solution tends to favor hydrolysis of the 

esters to the acids. No distinction was made between 

the monomethyl esters and the free acids for the dicarboxylic acids in the waste because both types of compounds were extracted in the acid fraction, and methylation with diazomethane converted both the monomethyl ester and free acid to the same dimethyl ester. 

For example, what is identified as terephthalic acid 

may actually be monomethyl terephthalate in the 

waste because methylation of both compounds will 

produce dimethyl terephthalate. The fact that monomethyl terephthalate is much more water soluble than 

terephthalic acid strongly suggests that the 

monomethyl ester of terephthalic acid predominates in 

the waste.

The organic waste analysis demonstrated that an 

industrial organic waste can be characterized by using 

a logical analytical scheme, by conducting a materials 

balance with DOC, and screening for organic compounds which are likely to be found in the waste as the 

result of the industrial process.

INORGANIC ANALYSIS

Table 4 summarizes the inorganic constituents 

found in the waste prior to injection. This table gives 

averages of two inorganic waste analyses performed by 

the WRD Central Laboratory, Salt Lake City, Utah, 

with a few miscellaneous analyses performed 

elsewhere. The data of the individual analyses are 

given in Basic Data table 21. The elements determined 

by atomic adsorption were Al, Mn, Ca, Mg, Na, K, Sr, 

Mo, Ni, Cd, Cr, Co, Hg, Zn, and Cu. Automated colorimetric methods were used to determine SiO2, Fe, 

SOi, Cl, NO2-NOs, and POi, and manual colorimetric 

methods were used to determine As, Se, and F.
16 SUBSURFACE ORGANIC WASTE INJECTION, NORTH CAROLINA 

TABLE 3. Average organic analysis of waste

Structural Concentration Concentration Percentage 

Compound formula (mg/1) as DOC (mg/1) of DOC

,0

Acetic acid CH3-C'' -OH 9,350 3,740 52.6

Q

Formic acid H-C* -OH 3,110 812 11.4

p-Toluic acid (T^j 1,140 805 11.3

CH3

Formalidehyde H-C* -H 1,800 720 10.1

Methanol CH 3OH 757 284 4.0

0.^C-OH

459 257 3.6

,C-OH 0' 

C'°-OH

Phthalic acid (j_^I 76 43 .6

0,

Mj-OH

Benzoic acid H^xJ 54 37 .5

Waste DOC-7110 mg/1 Total 6,698 94.1

Trace organic compounds (less than 0.5 mg/1 DOC)

Compound

Dimethyl phthalate

Dimethyl succinate

Dimethyl terephthalate

Methyl acetate

p-Methylbenzyl alcohol

Methyl formate

Methyl-p-formyl benzoate

Methylsuccinic acid

Methyl-p-toluate

Propionic acid

Succinic acid

Structural formula

o*

C-OCH3

Ox

Q*C-OCH3

0 .0

CH30-C-CH2-CH2-C-OCH3

*C-OCH3

0

C-OCH* ft J

0

CH 3-C* -OCH3

a 

OH

CH 3

H-C*°-OCH3

\

^-OCH3

^^

0* " 

CH 3

0 i -0 HO- t-CH2-CH-C' -OH

°*C-OCH3

O

CH3

CH3-CH2-C*°-OH

HO- VC-CH2-CH2-C" -OH

Of the inorganic parameters commonly found in mg/1 

levels in ground water, only Ca, SiOa, andNCte-NOa 

were significantly higher in the waste than in the 

native ground water present in the injection zone.

TABLE 4. Inorganic waste analyses

Dissolved constituent Concentration

Milligrams per litre

Dissolved constituent Concentration

Silica (SiOz) ............................................ 31

Calcium (Ca).................................... 1300

Magnesium (Mg)................................... 31

Sodium(Na)............................................. 1.7

Potassium(K) ......................................... 3.8

Sulfate(SO4) .......................................... 25

Chloride (CD ........................................... 5.4

Fluoride (F)............................................... 2.1

Nitrite-nitrate (NOz-NOs) ............... 3.9

Orthophosphate (PCW .............................. .28

Hardness as CaCOz (Ca, Mg).......... 3400

pH........................ . ..................... 3.8

Specific conductance 4550 

(micromhos at 25°C).

Micrograms per litre

Aluminum (Al), total.............................. 6200

Arsenic (As).................................................... 3

Cadmium (Cd)................................................ 4

Chromium(Cr), total................................ 260

Cobalt (Co).......-...................................... 1600

Copper (Cu)............................................... 100

Iron (Fe), total.......................................... 5500

Lead(Pb)..............-..................--....-.....-.. 7

Manganese (Mn)........................................ 120

Mercury (Hg), total.................................... 1

Molybdenum (Mo).......................................... 2

Nickel (Ni).................................................... 50

Selenium (Se) .............................................. 24

Strontium (Sr).............. ................. 820

Zinc (Zn)...................................................... 590

Prior to injection, the waste moved through a settling 

basin, was passed through a filter to remove particles 

over 20 pm in size, and was treated with lime to adjust 

the pH to 4. The high levels of calcium and silica in the 

waste undoubtedly come from the pre-injection lime 

treatment in which the organic waste acids act to solubilize calcium and silica. The levels of NOa-NOs can 

only be considered high in comparison to the native 

ground water in which there is practically no nitrate or 

nitrite. However, the presence of nitrate or nitrite in 

the waste may be significant because it is an available 

source of nitrogen for microorganisms that may be 

degrading the waste in the subsurface environment.

Aluminum and cobalt were found in mg/1 concentrations in the waste whereas they are usually found in 

fig/I concentrations in ground water. The source of 

aluminum is probably from the pre-injection lime
HYDROCHEMISTRY OF NATIVE GROUND WATER 17

treatment, and its high concentration points out the 

potential of the waste for dissolution of aluminosilicate minerals. The high cobalt concentration is of 

interest because cobalt salts are frequently used as 

catalysts in the oxidation of p-xylene.

None of the major inorganic waste solutes calcium, 

magnesium, silica, iron, aluminum, and sulfate can 

serve as satisfactory tracers of waste movement in the 

subsurface. These solutes are common constituents of 

the minerals in the injection zone, and their source 

cannot be differentiated between the waste and the 

injection zone. Nitrite-nitrate are assimilated by the 

microorganisms in the injection zone because they are 

essential nutrients in limited supply. Lastly, cobalt 

might initially seem to be an ideal inorganic tracer for 

waste movement because it is an element not commonly found in significant concentrations in ground 

water or as a common constituent in aquifer minerals. 

However, cobalt is a divalent cation which participates 

in cation-exchange reactions with the minerals within 

the injection zone, and is more strongly held and retained by exchange complexes on the aquifer minerals 

than is calcium or sodium which are the predominant 

cations in the native ground water. The law of mass 

action in ion-exchange reactions also indicates that 

cobalt will be removed from the waste solution and 

replaced by calcium and sodium from the exchange 

complex because the ratio of calcium to cobalt is 100 

times greater in the ground as compared to the waste, 

and the ratio of sodium to cobalt is 10 million times 

greater in the ground water than in the waste.

In summary, the dissolved ionic solutes of the industrial waste solution consist primarily of calcium and 

hydrogen as cations, and of acetate, formate, p-toluate, 

and terephthalate as anions. All combinations of these 

ionic species appear to be present in concentrations 

below saturation solubilities except for calcium and 

terephthalate which forms a precipitate when the 

waste solution is cooled to 20°C.

PHYSICAL PROPERTIES

The waste prior to injection is a clear straw-colored 

liquid with an acrid odor which is a combination of the 

odors of acetic acid, formic acid, formaldehyde, and 

p-toluic acid. The temperature at which the waste was 

injected was about 45°C, and when the waste was 

cooled to the temperature of the injection zone (22°C), a 

white precipitate very slowly formed which was 

primarily the calcium salt of terephthalic acid. This 

precipitate may not appear until the waste is refrigerated or agitated because the waste is apparently easily 

supersaturated with respect to terephthalic acid and 

its inorganic salts.

The density of the waste at 20°C was determined to 

be 1.006 g/ml, and the density of the ground water at

this temperature was 1.0142 g/ml. The injection temperature was 45°C and the density of the waste at this 

temperature is 0.9951. This density difference may 

indicate that the lighter waste may tend to gravitate to 

the upper part of the injection zone and move outward 

from the injection well at a faster rate in the upper 

portion of the injection zone if the injection zone has a 

constant T (transmissivity) value throughout the 150- 

foot injection interval. Most likely the T value varies 

and the waste preferentially moves out into the zone 

of the highest T value regardless of whether this zone 

is at the top or bottom of the injection interval.

HYDROCHEMISTRY OF NATIVE 

GROUND WATER

The mean chemical analyses of the native ground 

water found in the five water-bearing zones at the 

waste injection site are given in table 5. Most of the 

inorganic water analyses were performed in the 

Geological Survey's Water Resources Division 

Laboratories in Raleigh, N.C., and Salt Lake City, 

Utah. Each individual inorganic water analysis performed on water samples obtained from observation 

wells during the course of this study is found in basicdata tables 22-32.

Water samples from the surficial sand aquifer were 

collected from wells 14, 15, and 16 during well conTABLB 5. Inorganic analysis of native ground water found in 

aquifers at waste-injection site

Dissolved constituent Depth of aquifer below land surface

25-65 ft 

(7.6-20m)

275-330ft 

(84-101m)

500-520 ft 660-740 ft 800-1,025 ft 

(152-158m) (201-226m) (244-312m)

pH.......................................... 

Specific conductance 

(micromhos at 25*C) .........

Density (g/ml at 20°C) .........

Silica (SiOa)...........................

Calcium (Ca) ........................

Sodium (Na) ........................

Bicarbonate (HCOs)............. 

Sulfate (SO*) ........................

Chloride (CD ........................

Fluoride (F) ..........................

Nitrite-nitrate (NOa-NOs) .

Orthophosphate (PCM ......... 

Dissolved organic carbon 

(DOC). 

Residue on evaporation 

at!80°C. 

Hardness as CaCOs (Ca,Mg)

Aluminum (Al), total. ...... ...

Cobalt (Co)...... ....................

Copper (Cu) ..........................

Lead (Pb) ...............................

Strontium (Sr).......................

62

48 

18.5

1.0000

4.9

2.6

1.3

3.6

.8

6.5 

2.9

6.0

.0

1.21 

.006 

2

35 

12

109

40

76

12

82

8,890 

20.1

1.004

8.1

28

40

1,900

73

578 

214

2,610

1.3

.22 

.005 

1

3,980 

231

280

173

1,450

112

1,200

7.8 7.7

19,800 27,200 

20.0 20.9

2 1.0042 1.0089

Milligrams per litre

7.2 9.5

130 260

177 267

4,520 6,000

121 182

354 303 

763 595

6,970 9,990

.8 .5

.05 .30 

.000 .047 

 3

13,100 17300 

1,050 1,740

Microerams per litre

613 343 

 9

 300

60

 10

 2

75

2,640

q

165

14

 2

3 -

2

 16,000

7.4

31,800 

22.7

1.0142

9.3

333

309

6,750

186

230 

273

12,100

.5

.05 

.045 

.5

20,800 

2,110

242 

2

425

69

18

1

71

2,260

285

356

10

1

8

18,600
18 SUBSURFACE ORGANIC WASTE INJECTION, NORTH CAROLINA

struction, and from Company supply well C. Water was 

obtained between depths of 25-65 ft (7.6-20 m) below 

land surface, and data in table 4 for this aquifer were 

averaged from the individual analyses. Data were also 

averaged to characterize water found in the 300-ft, 

500-ft, 700-ft, and injection zones. Water samples from 

the 300-ft zone were obtained from wells 14,15, and 16 

during construction, and from well 13 which is 

screened in the 300-ft zone. The only water samples 

which were available to characterize water found in 

the 500-ft zone were obtained from wells 14 and 15 

during construction. For the 700-ft zone, uncontaminated water samples were obtained from well 8 and 

from well 14 during construction. Well 3 which is completed in this zone was contaminated with waste before 

samples were obtained. Well 9 in this zone produced 

water with the same chemical composition as water 

from the injection zone before it became contaminated 

with waste. Uncontaminated ground water from the 

injection zone was obtained from wells 7, 11, 12, and 

16. Wells 2, 3, 4, and 5 were contaminated before samples could be obtained, and the injection zone was 

found to be contaminated with waste when wells 14 

and 15 were completed.

On the basis of dissolved solids content determined 

by residue on evaporation at 180°C, water from the 

surficial sand aquifer is classified as nonsaline, water 

from the 300-ft zone is moderately saline, and water in 

the 500-ft, 700-ft, and injection zones is very saline 

(Swenson and Baldwin, 1965). Just as dissolved solids 

increase with depth, so do calcium, magnesium, 

sodium, potassium, strontium, manganese, chloride, 

hardness, specific conductance, density, and temperature.

The parameters which do not increase with depth 

are pH, bicarbonate, and sulfate. Bicarbonate and pH 

attain their maximum values in ground water from the 

300-ft zone, whereas sulfate content is the highest in 

the 500-ft zone. Below the 300-ft zone, both bicarbonate and pH decrease with depth, and sulfate content 

decreases with depth below the 500-ft zone. This variation of sulfate content with depth may reflect variations in aquifer mineral constituents, bacterial reduction of sulfate in an anaerobic environment, or formation of barium and strontium sulfates. Water from the 

700-ft zone and the injection zone contains a small 

amount of hydrogen sulflde, as evidenced by its odor 

and the formation of black sulflde precipitates; therefore, sulfate may be reduced in these zones by bacterial 

reductive processes. Hem (1970, p. 168) states that 

water containing 1 mg/1 of barium should contain no 

more than a few milligrams per litre of sulfate, and 

water containing 10 mg/1 of strontium should contain 

no more than a few hundred milligrams per litre of 

sulfate. The water from the injection zone contains

about 10 mg/1 of strontium and about 0.4 mg/1 of 

barium; therefore, the concentrations of these two constituents may well be the solubility controls on the 

concentration of sulfate.

The change in bicarbonate and pH with depth may 

also reflect variations in aquifer mineral constituents; 

however, the decrease observed in the more highly 

mineralized water may well be an artifact caused by 

the precipitation of calcite during the sampling, storage, and shipment of the samples before the analyses 

were performed.

The only significant concentration of nitrite-nitrate 

was found in the surficial sand aquifer where nitritenitrate probably infiltrates from surface sources. 

Phosphate concentrations were very low in all aquifers. These low concentrations of essential nutrients 

for microbial activity may be important in limiting the 

amount of microbial waste degradation in the subsurface.

Lastly, the concentration of dissolved iron and dissolved organic carbon (DOC) is of interest because 

these parameters are most affected by waste injection. 

Above pH 4.8, the solubility of ferric iron is less than 

10 ju,g/l unless there are significant concentrations of 

organic substances capable of forming soluble complexes (sequesterization) with ferric iron (Hem, 1970, 

p. 116). Because the DOC concentrations are quite low 

and the pH is slightly alkaline, it is probable that most 

of the dissolved iron exists in solution in the more 

soluble reduced form, ferrous iron.

WASTE-AQUIFER INTERACTIONS

After postulating a number of probable wasteaquifer interactions at the inception of this study in 

January, 1971, a two-fold study was undertaken to test 

the predicted transformations of the waste after subsurface injection. A site study based on analysis of 

water samples obtained from the observation well system was initiated in June 1971 and terminated in 

November 1973. A laboratory study which simulated 

waste injection into cores of aquifer material was conducted following the site study, and was terminated in 

March 1974.

SITE STUDY

INITIAL CONDITIONS

The water-quality situation at the waste-injection 

site at the beginning of this study in 1971 is shown in 

table 6. Water samples from wells 2, 3, 4, and 5 had 

analyses very similar to the inorganic analysis of the 

waste given previously in table 2, and all of the expected reactions had apparently stopped or slowed to 

rates where they were not observable. At this time, 

native water samples from the injection zone could be 

obtained from the recently constructed wells 7 and 11,
WASTE-AQUIFER INTERACTIONS 19

TABLE 6. Change in water composition with waste contamination

Specific conductance, 

Well in fimhos/cm at 25°C

7 

11 

4 

5

32,500 

32,000 

8,280 

8,080

Concentrations of dissolved constituents, in mg/1

Date

11/3/71 

11/3/71 

6/15/71 

6/15/71

pH Sift

7.3 11 

7.2 8.6 

4.0 23 

4.0 34

Al Fe

0.3 1.8 

.2 1.8 

6.8 8.3 

7.1 8.0

Mn

0.2 

.3 

.3 

.3

Ca

705 

537 

2500 

2400

Mg

107 

195 

34 

49

Na K HCOa

6800 330 230 

6600 330 230 

2.9 2.2 0 

3.2 2.3 0

SO4

280 

210 

8.0 

19

Cl F

12,000 0.9 

12,000 0.6 

230 1.3 

140 1.3

P NOs DOC

0 0 1.2 

0 0 0.7 

1.3 3.9 10,600 

1.1 3.9 11,200

avg. concn wells 4 and 5 

avg. concn wells 7 and 11

2.9 28 5.1 1.0 3.9 0.27 .00046 .0068 0 0.055 0.02 1.7 11,500

which were outside the area of waste contamination 

and water obtained from these wells were completely free of waste. The data in table 6 represents the 

two extremes between wastes and native ground water. An objective of the site study was to observe the 

organic and inorganic changes in the ground-water 

analyses in going from an uncontaminated to a contaminated state and to relate these changes to the 

initial hypothesized waste transformations (fig. 17) so 

that the initial hypotheses could be confirmed or rejected, new hypothesis made and tested, and to formulate final conclusions concerning waste transformations as presented in this report.

INITIAL CONCEPTUAL MODEL OF INJECTED-WASTE 

REACTIVITY AND MOVEMENT

The initial conceptual model of the various stages of 

the waste in the subsurface environment is diagrammed in figure 17. This model is diagrammed for a 

certain point in time after the beginning of waste injection when the various components of the model have 

had a chance to form due to various waste-aquifer 

interactions. With increasing time during waste injection, the dimensions of this model will expand and 

move to the right. The leading volume of waste moving 

outwards from the injection well is mixed and dispersed with the native aquifer fluids, and this area of 

dispersion is called the waste front in this conceptual 

model. The waste area which extends between the injection well and the waste front is called the waste

INJECTION

WELL WASTE INTERIOR WASTE FRONT

WASTE I SLOW-REACTION 

POOL ZONE

FAST-REACTION 

ZONE

TRANSITION (MICROBIAL 

ZONE ACTIVITY 

ZONE

WASTE MOVEMENTFIGURE 17. Initial conceptual model of injected-waste reactivity and 

movement.

interior where the native ground water has largely 

been replaced by the injected waste. The waste front 

and waste interior are divided into five zones which are 

labeled to describe the predominant types and 

mechanisms of waste transformations within each 

zone. Microbial waste degradation is thought to occur 

only at the leading edge of the waste front, and this 

zone is called the microbial activity zone.

The area behind the microbial activity zone is called 

the transition zone because it is speculated to be a 

region of transition between predominantly microbiological and chemical reactions which occur in the 

injected waste. Few chemical reactions are thought to 

occur in the transition zone because the reactions between the waste and the injection zone components are 

essentially completed by the time the waste reaches 

the transition zone. However, decreasing microbial activity is expected throughout this zone because of increasing concentrations of certain toxic organic compounds such as formaldehyde, and because of the disappearance of limiting nutrients such as nitrate and 

phosphate.

The zone trailing behind the transition zone is called 

the fast-reaction zone in which neutralization type 

reactions occur between the waste acids and the 

aquifer mineral constituents. Such reactions include 

the acidic dissolution of aquifer carbonates and iron 

oxide coatings. The pH of the waste solution changes 

from four at the trailing edge of the zone to seven at the 

boundary with the transition zone.

Reactions which occur in what is defined as the 

slow-reaction zone are the slow solubilization of silica, 

aluminum, and iron from the aluminosilicate minerals 

in the injection zone. The last zone which is adjacent to 

the injection well is called the waste pool because there 

are no apparent reaction or changes with time going on 

in the waste in this area.

REACTIONS OBSERVED AT WELLS 1, 2, 3, 4, AND 5

At the beginning of this study, limited data were 

available from the Company concerning waste contamination of wells 1, 2, 4, and 5 during the first few 

months of waste injection. Residue on evaporation and 

pH data for water samples obtained from wells 1 and 5 

during waste contamination are shown in figure 18. 

When the first samples were taken in July 1968, lower
20 SUBSURFACE ORGANIC WASTE INJECTION, NORTH CAROLINA

DATE (1968)

FIGURE 18. Variations in pH and residue on evaporation from samples taken during observation of waste front in wells 1 and 5.

residue on evaporation values indicated that waste 

was already present in observation well 1, which was 

only 50 ft (15 m) from injection well 1-6, whereas observation well 5, at a distance of 150 ft (46 m), was 

waste-free.

Observation well 5 remained waste-free until the 

beginning of October, when both the pH and residue on 

evaporation started to decrease. The pH decreased because of the acidity in the waste and the residue on 

evaporation decreased because the native ground 

water was replaced by the waste which had a lower 

dissolved solids content.

The fast-reaction zone in which the waste acids are 

neutralized is shown by the data from observation well 

1. From July 28 to October 15, 1968, the pH remained 

between 5 and 6, during which time carbonates and 

iron oxides within the injection zone were reacting 

with the waste. The mixture of free organic acids and 

organic-acid salts from the neutralization reaction resulted in a pH between 5 and 6. When the fast wasteneutralization reactions stopped, the pH abruptly decreased to the pH of the injected waste (pH 4) on October 18, and has remained near this level to the present. Residue on evaporation in this well also decreased 

at this time to levels found in the injected waste.

Water samples collected while the waste was reacting with carbonate minerals contained large amounts 

of dissolved carbon dioxide, which is a product of the 

acid-carbonate reaction. A sample of gas which effervesced from a water sample collected from well 3 contained 70 percent carbon dioxide by volume as shown 

in basic-data table 33.

REACTIONS OBSERVED AT WELL 9

The first opportunity to observe an aquifer during 

the process of waste contamination occurred at well 9 

in which waste suddenly appeared in high concentrations in December 1971. The first inorganic analysis 

determined on a sample collected on June 15, 1971 

(basic-data table 25), indicated that the composition of 

samples obtained from this well (screened in the 700-ft 

zone) was essentially the same as water obtained from 

the injection zone. This was an indication that ground 

water from the injection zone had somehow leaked into 

the 700-ft zone before waste injection was begun in the 

second injection well I-7A; therefore, it was not very 

surprising when waste appeared in this well after 

waste injection had started in well I-7A.

By June 1972, a sample collected from well 9 contained 5,800 mg/1 DOC, 78 mg/1 iron, 3,900 mg/1 calcium, with a pH of 5.8. These high concentrations of 

calcium and iron were indicators of waste dissolution 

of aquifer carbonates and iron oxides. The analysis of a 

sample collected almost a year later (basic-data table 

25) showed that the DOC concentration had increased 

only slightly to 6,300 mg/1, the pH was 4.5, the calcium 

concentration had decreased to 3,100 mg/1, and the iron 

concentration had increased to 310 mg/1, which is an 

extremely high concentration of iron in natural water. 

These changes observed in two samples collected a 

year apart indicate that the reaction of the waste with 

aquifer carbonates occurs previous to, and at a higher 

pH than, dissolution of iron oxides. Carbon dioxide gas 

was also present in the June 1972 water sample 

(basic-data table 33), whereas no gas at all was present 

in the June 1973 sample. The very high concentration 

of iron in the June 1973 sample indicates that the 

phthalic acids found in the waste were probably forming water-soluble complexes with iron.

The indications of the carbonate and iron oxide dissolution reactions found in the 700-ft zone tend to confirm the hypothesized reactions found in the fastreaction zone; however, these reactions occurred in an 

aquifer overlying the injection zone as the result of a 

leak, and well 9 was not regarded as a completely 

satisfactory sampling point to obtain information concerning reactions in the waste-injection zone.

REACTIONS OBSERVED AT WELLS 11, 14, AND 15

The major share of information concerning wasteaquifer interactions was derived from analysis of water 

samples obtained from wells 11, 14 and 15 during the 

time the waste front could be sampled in these wells. 

Waste was found in wells 14 and 15 at the time (May 

1972) they were completed in the injection zone as
WASTE-AQUIFER INTERACTIONS 21

shown by the high biological oxygen demand (BOD) 

values determined by company analysis not given in 

this report. Waste appeared in well 11 in December 

1972, detected on the basis of DOC concentrations 

being above background levels. Well 11, 14, and 15 

were sampled on a periodic basis from June 1972 to 

October 1973 by trained observers at the site. Data 

obtained on water samples from wells 11, 14, and 15 

during this period are found in basic-data tables 34,35, 

and 36, respectively.

Waste was present in well 15 for only a short time 

after it was completed. The DOC data in basic-data 

table 36 shows that all except a trace of the waste was 

gone from this well by December 1972. The presence of 

acetic acid, p-toluic acid, and terephthalic acid definitely confirmed the presence of waste in this well 

during the period of elevated DOC levels.

Waste was present in well 14 in much higher concentrations than well 15, and it did not disappear until 

January 1973. The significant variable parameters determined during the period when waste was present in 

this well are plotted in figure 19. The waste concentrations never became sufficiently high to cause detectable effects on pH, alkalinity, specific conductance, and 

the inorganic anions and cations with the exception of 

iron. Pressure changes measured at wellhead were 

plotted to establish a possible relation between (1) the

DATE (1972-1973)

FlGUBE 19. Variables observed during passage of waste front in

well 14.

decreases in wellhead pressure difference in the injection zone between the injection well I-7A and well 14 

and (2) the decrease in DOC in well 14. Gas effervescence was defined as the volume of gas which evolved 

from an equivalent volume of water under atmospheric 

pressure at the sampling site.

From June through October 1972, the waste content 

(DOC) in well 14 appeared to be increasing (fig. 19); 

however, the waste content abruptly decreased at the 

beginning of November and there was no sign of waste 

in the well by late January 1973. Although there were 

large pressure variations caused by variations in the 

injection rate during conversion to surface treatment, 

the DOC tended to decrease as the pressure difference 

decreased. This direct relationship between DOC and 

pressure difference indicated some change in the 

ground-water flow system with the cessation of waste 

injection.

The first period (June 20 to August 1) of increasing 

waste concentration showed only an increase in DOC 

as evidence of waste in the well. No gas was found in a 

sample collected on August 1, but gas appeared abruptly in a sample collected only 2 days later. For the 

period August 3 to October 31, the amount of gas continued to increase as DOC increased, and throughout 

November, the amount of gas decreased as DOC decreased until there was no gas present in the well early 

in December. A summary of the gas analyses obtained 

during this period is given in table 7.

TABLE 7. Well 14 gas analyses

___________________[N.d., not detected]___________________

Date of 

sampling

Percent of total gas volume

CH4 CO* IfcS

8-1-72

8-7-72

8-14-72

N.d.

N.d.

0.2

25

21

36

50

54

40

11

11

11

N.d.

N.d.

0.8

10-11-72

11-2-72 

11-22-72

N.d. 

N.d. 

N.d.

68

64

68

6.0

33

12

4.8 

3.8 

1.5

N.d. 

N.d. 

N.d.

The appearance of gas, which contained methane 

concentrations up to 54 percent of the total gas volume, was the first indication of anaerobic microbial 

decomposition of the organic waste. The following 

reactions show how acetic and formic acid are converted to methane by the microorganisms:

a. CH3 COOH+H2 O >>CH4+H2 CO3 

(Lawrence and McCarty, 1969)

b. 4HCOOH+H2 O >CH4 +3H2 CO3 

(Siebert and Hattingh, 1967)

The most probable reason why microbial degradation of the waste did not begin immediately with the 

appearance of the waste is because there is a time lag 

during which the microbes are building up numbers 

large enough to significantly degrade the waste.
22 SUBSURFACE ORGANIC WASTE INJECTION, NORTH CAROLINA

The total iron concentration plotted in figure 19 is 

very closely related to the waste concentration. Oborn 

and Hem (1961) suggest that microbial activity resulting from organic substrates can indirectly increase the iron concentration by a two-stage process: 

(1) Microbial oxidation of waste to carbon dioxide and 

water lowers Eh by oxygen depletion and lowers pH 

by solution of carbon dioxide; (2) lowering of Eh and 

pH converts insoluble ferric iron to more soluble ferrous iron. Iron may also be brought into solution by 

complexation with the aromatic dicarboxylic acids 

found in the waste (Ringbom, 1963). A likely complexation reaction is shown below:

phthalic acid 

anion

phthalic acid-ferrous iron 

complex anion

In samples collected up to September 4, 1972, there 

was considerable evidence of microbial sulfate reduction to sulfide in the form of black sulfide precipitates 

and the hydrogen sulfide gas found during the gas 

analysis. In later samples, sulfide precipitates and 

hydrogen sulfide gas were absent, and the level of 

dissolved iron increased, possibly because insoluble 

ferrous sulfide precipitates were no longer forming. 

Waksman (1952) showed how sulfate can be reduced 

with the microorganisms using acetic acid as a source 

ofenergy: 

CaSO4 +CH3COOH > H2S +CaCO3 +CO2 +H2O.

Methane production, iron reduction, and sulfur reduction are believed to be indicators of anaerobic microbial activity induced by waste concentrations in 

the ground water. These waste degradation reactions 

are a strong confirmation of the microbial activity 

zone in the waste front which was postulated in the 

initial conceptual model.

One of the most important aspects of this study was 

to define changes in the organic composition of the 

waste as it traveled from the injection well to an 

observation well. Acetic acid, formic acid, p-toluic 

acid, and terephthalic acid were determined on water 

samples collected from wells 11, 14, and 15 during 

waste contamination. Formaldehyde and phthalic 

acid were not found in samples obtained from these 

wells, and methanol was not determined because 

there was no way to quantitatively concentrate or 

extract methanol from the ground-water samples for 

its determination. Benzoic acid, succinic acid, and 

methylsuccinic acid were found in trace amounts in 

several samples, but were not quantitatively determined.

TABLE 8. Relative organic composition of injected waste found in

wells 11, 14, and 15 

[N.d., not detected]

Percentage of DOC

Constituent

Acetic Acid ................

p-Toluic Acid ............

Terephthalic Acid....

Waste Before 

injection

52.6

11.4

11.3

3.6

Well 11

73.5 

N.d. 

N.d. 

1.9

Well 14

78.7 

.4 

2.7 

.9

Well 15

72.5 

N.d. 

5.9 

1.5

The concentration curves for acetic acid, p-toluic 

acid, and terephthalic acid closely follow the DOC 

concentration curve in figure 19 for well 14. However, 

the formic acid concentration curve did not peak at 

the October 31 sample as did the other parameters.

To determine the changes in the relative composition of the organic waste constituents, the percentage 

of DOC was computed for acetic acid, formic acid, 

p-toluic acid, and terephthalic acid for each individual 

analysis in wells 11, 14, and 15; then the percentages 

were averaged for each well and compared with the 

averaged waste percentage DOC composition for 

these constituents. The results are shown in table 8.

Of the four organic compounds determined in well 

14, the inorganic salts of acetic and formic acids are 

the most soluble in the ground water, and they should 

not be significantly adsorbed by aquifer constituents 

after waste injection. Acetic acid (sodium acetate) 

comprises the majority of the DOC found in well 14, 

but formic acid (sodium formate) only constitutes 0.4 

percent whereas it constitutes 11.4 percent of the 

DOC in the injected waste. Assuming that the relative composition of the injected waste was fairly constant during the 4% years of waste injection, formic 

acid must have decomposed during the time it 

traveled from the injection well to well 14. The noncharacteristic formic acid concentration curve in figure 19 also indicates formic acid degradation within 

well 14. Siebert and Hattingh (1967) stated that formic acid appears to play a central part in the formation of methane, and is the organic compound most 

readily converted to methane by anaerobic bacteria.

The percentage composition for p-toluic acid and 

terephthalic acid also decreases in samples obtained 

in well 14 as compared to the injected waste (table 8). 

Because aromatic acids are much less biodegradable 

than aliphatic acids, it is likely thatp-toluic acid and 

terephthalic acid are depleted during waste movement in the subsurface by adsorption on the aquifer 

sediments rather than being depleted by microbiological degradation. Terephthalic acid and p-toluic acid 

are much less water soluble than acetic and formic 

acid and therefore are more easily adsorbed.

Indications of waste in well 11 appeared in December 1972 and samples were collected for analysis
WASTE-AQUIFER INTERACTIONS 23

from January through July 1973. The waste concentration as represented by the DOC curve increased 

very slowly in almost a linear manner during this 

period as shown in figure 20. Plots of concentration 

versus time are also given for acetic acid, terephthalic 

acid, and dissolved iron in figure 20. Formic acid, 

formaldehyde, and p-toluic acid were not detected in 

water samples from this well. There was no gas produced or evidence of sulfate reduction. The dissolved 

iron concentration curve does not show any discernable correlation with the waste concentration. Dissolved iron was essentially constant while the waste 

concentration was increasing.

Apparently the waste concentration did not become 

sufficiently high to induce microbial waste degradation as was found in well 14. In well 14, the first 

evidence of microbial waste degradation, methane 

gas, occurred when the DOC concentration was at 

about 25 mg/1. The highest DOC concentration in well 

11 was only 18 mg/1. Therefore, as in well 14, microbiological waste degradation does not seem to 

occur below a threshold level of waste concentration.

Both the acetic acid and terephthalic acid concentration curves increase in the same manner as the 

DOC curve in figure 20. Acetic acid constitutes about 

the same percentage of the DOC in well 11 as in well

DATE (1973)

FIGURE 20. Constituents measured during passage of waste front 

in well 11.

14; however, terephthalic acid was present in greater 

relative amounts, whereas p-toluic acid was not even 

detected (table 8). The relative abundance of 

terephthalic acid to p-toluic acid was reversed for the 

few samples collected from well 15 although the percentage of DOC due to acetic acid was about the same 

as for wells 11 and 14.

The different ratios of terephthalic acid to p-toluic 

acid in each of these three wells leads one to question 

the assumption that the waste composition was essentially constant during the 4l/2 years of waste injection. 

It is most probable that the organic waste collected 

from wells 11, 14, and 15 was injected at three different points in time and contained different ratios of 

terephthalic to p-toluic acid. It is remarkable that the 

acetic acid contribution to DOC is about the same in 

these three wells as is shown in table 8. Regardless of 

the wide variations of the ratio of terephthalic acid to 

p-toluic acid in samples obtained from these three 

wells, both terephthalic and p-toluic acids were below 

concentrations at which they were found in the injected waste. It is likely that these compounds were 

adsorbed by aquifer sediments during their travel 

from the injection well to the observation well.

POSSIBLE FLOW SYSTEMS ASSOCIATED 

WITH INJECTION ACTIVITIES

The history of waste concentrations in wells 11, 14, 

and 15 suggests that the ground-water flow system 

associated with injection activities is very complex 

both vertically and areally in the injection zone. In 

addition, a true measure of waste concentrations 

could not be obtained because the 150-ft (45-m) 

screened section of the observation wells permitted 

cross-circulation and dilution of waste-contaminated 

ground water with uncontaminated ground water, 

and it is very unlikely that the injected waste moved 

in uniform directions and rates in all permeable zones 

within the injection interval.

Examination of the driller's logs (Black, Crow, and 

Eidsness, Inc., 1971) of wells 7,1-7A, 11, and 12 show 

that from two to four permeable zones may exist at 

different points within the injection interval. Insufficient hydraulic data exist at this site to define the 

natural, preinjection flow system, and it is unknown 

whether the multiple permeable zones within the injection interval are interconnected and have the same 

artesian head, or whether they are independent and 

there is a differential, vertical distribution of head 

through the injection interval. The complex hydrogeology, the lack of hydraulic data, sampling limitations imposed by observation well construction, 

and the complexity introduced by waste injection at 

various rates and pressures at multiple sites all prohibit the modeling of injected-waste movement, and
24 SUBSURFACE ORGANIC WASTE INJECTION, NORTH CAROLINA

only various possibilities can be presented in this report.

A realistic hypothetical portrayal of the limits of 

waste movement at the upper and lower boundaries of 

the injection zone is represented in figure 21. The 

amoebic shapes of the areal waste distributions is 

intended to represent waste movement in directions 

of highest permeability. Non-coincidence of the lower 

boundary with the upper boundary shows that waste 

at the bottom of the injection zone may be moving in a 

different lithologic unit in directions independent of 

the waste in the upper part of the injection zone. The 

areal extent of the waste is represented to be much 

greater at the upper boundary of the injection zone 

because the specific gravity of the waste is less than 

the native ground water. However, if the permeability of the injection zone is greater near the lower

1000 2000 FEET

r I I

0 300 600 METRES 

EXPLANATION

Injection well

Observation well Injection zone

Observation well 700-foot zone

Observation well 300-foot zone

Observation well used as injection well

Original system

Limit of waste travel (upper boundary)

Limit of waste travel (lower boundary)

FIGURE 21. Hypothetical areal distribution of waste at the upper 

and lower boundaries of the injection zone.

boundary, the relative sizes of the areas invaded by 

the waste may be opposite from that shown in figure 

21. Because the major quantity of waste was injected 

through wells 1-6, 4, and 5, the areal waste distribution is biased around this cluster of injection wells 

rather than around injection well I-7A, where a lesser 

quantity of waste was injected. Lastly, because waste 

injection occurred at multiple sites, the formation of 

"pools" of uncontaminated ground water surrounded 

by waste is also shown in figure 21.

Changes which occurred in the waste content in 

samples obtained from wells 11,14, and 15 during the 

2 months after the cessation of waste injection indicated either a major change in waste distribution, or a 

change in water being sampled by these wells.

Therefore, the last experiment performed for the 

site study was to allow wells 11, 14, and 15 to flow on 

November 1-2, 1973, to determine if waste could be 

drawn into these wells. It was hypothesized that if 

waste did not reappear after withdrawing a limited 

quantity of ground water, the waste distribution had 

likely changed. However, if waste appeared after a 

short period of well flow, it is likely that the disappearance of waste with termination of injection resulted from changes in internal circulation of ground 

water within and adjacent to the observation well. 

This internal circulation is diagrammed in figure 22. 

Allowing the well to flow should withdraw water from 

all the permeable zones within the injection zone, 

which is screened from 850 to 1,000 ft (259-305 m) in 

the observation wells.

The wells were allowed to flow by disconnecting the 

pressure gages and opening the 1-inch ball valve on 

the wellhead assemblies. The results of this flow test 

are summarized in table 9.

TABLE 9. Observation well flow-test data 

[Nd., not detected]

Sample 

No

Flow 

period 

(min)

Total 

flow 

(gal)

DOC

(mg/1)

Acetic 

acid 

(mg/1)

Formic 

acid

(mg/1)

p-Toluic Terephthalic 

acid acid 

(mg/1) (mg/1)

Well-11 (flow rate = 25 gal/min)

1 

2 

3 

4 

5

0 

235 

400 

1,050 

1,190

0 

5,875 

10,000 

26,250 

29,750

18 

75 

90 

170 

185

38 

107.4 

160.1 

201.3 

348.0

N.d. 

2.16 

2.76 

3.61 

6.63

N.d. 

2.71 

2.16 

4.43 

5.07

0.58 

2.75 

2.61 

3.44 

3.74

Well-14 (flow rate = 10 gal/min)

1 

2 

3 

4 

5

0 

270 

435 

1,075 

1,255

0 

2,700 

4,350 

10,750 

12,550

1.0 

1.0 

1.0 

1.0 

2.0

- -

Well-15 (flow rate = 60 gal/min

1

2 

3

0 

160 

375

0 

9,600 

22,500

1.0 

5.0 

47.0 73.45 1.54 1.24 1.06

The flow from well 15 was stopped after 375 minutes 

because of concern about the withdrawn saltwater infiltrating to the supply wells. Because this well had the 

highest flow rate of about 60 gal/min (227 1/min), 

enough water was withdrawn from this Well in this 

period of time to pull the waste into the well. The last
WASTE-AQUIFER INTERACTIONS 25

sample taken had a DOC of 47 mg/1 and contained 

acetic acid, formic acid, terephthalic acid, and p-toluic 

acid in the amounts shown in table 7.

Well 11 initially contained a small amount of waste 

at the beginning of the flow period, and the amount of

During waste injection

After waste injection

EXPLANATION

Sand and gravel

(J_)<(2)<\3) Pressure gradient

Direction of ground 

water flow

Injected waste

FIGURE 22. Probable internal circulation of ground water within well

14.

waste increased steadily during the flow period to the 

last sample, which had a DOC of 185 mg/1. The relative 

composition of the organic constituents changed in 

each successive sample. Formic acid and p-toluic acid 

appeared in sample two, whereas they were not detected at the beginning of flow. By the end of the flow 

period, the ratio of terephthalic acid to p-toluic acid 

had reversed with p-toluic acid being present in the 

greater concentration. A gas sample obtained during 

the period the well was flowing contained methane at a 

concentration of 18 percent of the gas volume (basicdata table 33). The presence of methane indicated that 

microbiological waste degradation was occurring in 

the injection zone near well 11, although the waste 

concentrations were not high enough in well 11 to 

induce methane formation before flow was started.

Waste was not drawn into well 14 during the period 

of flow. The flow rate of well 14 was only 10 gal/min (38 

1/m) and table 7 shows that only about half as much 

water was withdrawn from well 14 as was withdrawn 

from wells 11 and 15. A gas sample was obtained which 

contained methane at 30 percent by volume (basic-data 

table 33), but this methane only indicated that waste 

had been present at a previous period in the injection 

zone. Methane apparently exists as a gas at the pressure found in the injection zone, and this gas was 

entrapped by the aquifer sediments and did not move 

away from the well with the waste when internal circulation displaced waste from the well. It is quite 

likely that waste would have been drawn into well 14 if 

it had been allowed to flow for another day and a 

volume of ground water equivalent to wells 11 and 15 

had been withdrawn.

The results of the observation well flow experiment 

tended to confirm the hypothesis that waste was in the 

immediate vicinity of wells 11,15, and most likely well 

14. It is still possible that after injection stopped, the 

areal distribution of waste as shown in figure 21 

changed because of the influence of the natural, regional flow system in moving the waste away from the 

observation wells. However, it would be unlikely that 

the waste would move in such a manner that it would 

quickly reappear when the wells were allowed to flow. 

In the opinion of the authors, the disappearance of 

waste was a result of internal circulation changes 

within the screened section of the observation wells, 

thus preventing waste from being drawn into the sampling tube. This experiment shows that in a study of 

this type an observation well which has its screened 

section opened to several water-bearing zones may not 

serve its purpose as an observation well because it may 

not yield injected waste at low-flow rates of the sampling tubes; thus when the dominant proportion of the 

waste is present in one of the zones, the samples obtained may not be representative.
26 SUBSURFACE ORGANIC WASTE INJECTION, NORTH CAROLINA

MICROBIOLOGICAL STUDY

The results of the microbiological study are in a 

report by DiTommaso and Elkan (1973), and only the 

significant findings will be discussed in this report.

The waste, prior to injection, was found to be void of 

any bacterial contamination. Likewise, samples obtained from observation wells containing high levels of 

waste did not support microbial flora. Approximately 

3,000 organisms per millilitre were present in water 

samples obtained from the uncontaminated injection 

zone, and this count remained constant for the duration of the study. This count was somewhat high according to G. G. Ehrlich (oral commun., 1973), who 

cited a range of 10-1,000 microorganisms per millilitre 

as representative for uncontaminated ground waters. 

These native organisms were isolated and identified as 

shown in table 10. Although anaerobic, methanogenic 

bacteria were found in certain waste-contaminated 

wells, most of the organisms isolated from the uncontaminated wells were facultative or aerobic genera 

rather representative of the normal microflora of 

aquatic environments.

The most common genera found included Agrobacterium, Pseudomonas, Proteus, Bacillus, Aerobacter, 

Corynebacter, Arthrobacter, and Micrococcus. In laboratory studies, isolates of these genera, either singly or 

in combination, were inoculated into a medium in 

which various dilutions of the waste served as the sole 

carbon and energy source. None of these well isolates 

were able to grow and decompose waste under these 

conditions. In addition to these microorganisms, a very 

low number of obligate anaerobes were detected. Because there is little or no organic-energy substrate in 

the uncontaminated injection zone, these obligate 

anaerobes can be present only in limited number. 

When a readily available carbon and energy source 

was added in the form of the injected waste, these 

anaerobes increased in number and constituted the 

waste-decomposing microflora.

On July 7, 1972, a 20-week study was initiated to 

study bacterial decomposition of waste which was occurring at that time in well 14 as was evidenced by

methane gas formation. A rapid increase in the microbial population resulting from the presence of dilute 

concentrations of waste in well 14 occurred during the 

20-week period, and this increase is shown graphically 

in figure 23. The colony-forming units per millilitre in 

the control well (well 11) remained approximately constant at 3,000 organisms per millilitre, whereas in well 

14, the population increased to approximately 

1,000,000 organisms per millilitre.

TIME, IN WEEKS

FIGURE 23. Comparison of number of bacteria per millilitre (as 

colony-forming units) in waste front (well 14) and in uncontaminated aquifer (well 11).

Methanogenic bacteria were isolated in pure culture 

from water samples obtained from well 14 during the 

20-week study. Gram stains were performed in an attempt to classify these bacteria according to genus. 

Two different morphologic types were observed. The 

first was a gram-negative, slightly-curved rod, which 

was tentatively placed in the genus Methanobocte*

TABLE 10. Identification of isolates from uncontaminated deep well 11 

[-.negative reaction; +, positive reaction; A, acid produced; A*, weak positive reaction; AG, acid and gas produced]

Carbohydrate utilization

Organism 

Identified Gram stain Morphology Motility

Sulfide 

production

Reduction Catalase Starch Indole

of nitrate production hydrolysis production Sucrose Mannitol Lactose Glucose Maltose

Agrobacterium

Pseudomonas

Proteus

Bacillus

Aerobacter

Corynebacter

Arthrobacter

Micrococcus

Pseudomonas

fluorescens

group

Rod

Rod

Rod

+ Rod

Rod

+ Rod

Rod

+ Cocci

Rod

+

+ - + -

+ - + -

 + -

- - + -

- - + -

 + -

_ _ + .

+ - + -

1- 

t- - - A

t- - - A

r- + 

t- - - A

L _ _

h + - A

h + - -

AG

AGA*

AG

A

A

_

-

AG

AGA*

AG

A

A

A

A

AG

A

A

AG

A

A

A

A*

AG

AG

A

AG

_

A

A

A*
LABORATORY WASTE-AQUIFER REACTIVITY STUDIES 27

rium. The other was a coccus which was gram positive 

and occurred in masses; it was tentatively placed in the 

genus Methanococcus.

Although the waste was found to be decomposable by 

microorganisms, the system appeared to have low efficiency. Laboratory studies showed the waste to be toxic 

even in moderate concentrations. The major localization 

of waste decomposition was found in wells located at the 

periphery of the waste front where the waste is highly 

dilute.

The site study of waste-aquifer interactions provided 

qualitative evidence for a number of reactions and 

waste-decomposition processes which have occurred in 

the subsurface as the result of waste injection. A laboratory study was conducted which simulated waste injection into cores of aquifer material obtained from the 

injection zone. The objectives of this study were: (1) To 

better define the waste-aquifer interactions in a quantitative manner, (2) to substantiate in the laboratory 

waste-aquifer interactions which were observed on-site, 

and (3) to test for waste-aquifer interactions which could 

not be observed on-site because of the construction and 

placement of the observation wells.

LABORATORY WASTE-AQUIFER

REACTIVITY STUDIES

INTRODUCTION

The disposal site at Wilmington, N.C., offered a desirable and somewhat unique situation to study the 

chemical and microbial aspects of subsurface waste 

injection because of the large number of observation 

wells. The movement and the reactions occurring between the waste and the disposal aquifer could be 

studied at various stages of the passage of the waste 

through or past observation wells. Most injection-well 

systems do not have observation wells which can be 

used for waste monitoring; therefore other means must 

be employed to gain an insight on waste movement and 

reactivity.

A possible means of evaluating waste reactivity is to 

conduct waste-aquifer reactivity studies in the laboratory. Such studies are usually conducted during the 

initial stages of injection-well construction to evaluate 

the "compatibililty" of the waste with the receiving 

zone. These tests are essentially engineering oriented, 

are usually simplistic in nature, and are somewhat 

analogous to comparative permeability testing with 

the native ground water and the waste. A positive 

compatibility is achieved if the permeability of the 

waste saturated core is the same as or greater than 

that of the native ground water. A negative compatibility, or a decrease in permeability of the wastesaturated core could result from precipitation or coagulation of the waste, a reduction in porosity due to dispersion and plugging with aquifer or waste solids, the

swelling of aquifer solids, or other reactions which 

decrease the porosity of the core matrix.

The laboratory waste-aquifer reactivity tests in this 

study were designed to evaluate organic and geochemical reactions instead of the ordinary compatability 

testing such as changes in permeability and hydraulic 

conductivity. The general objectives of the laboratory 

tests were to determine (1) if the passage of the waste 

front through the injection zone could be simulated in 

the laboratory; (2) if the chemical and physical reactions which were predicted to occur between the waste 

and the aquifer materials in the receiving zone at the 

injection site would occur under laboratory conditions; 

and (3) to determine how well laboratory findings correlated with field data and observations.

METHODS AND MATERIALS

AQUIFER MATERIAL

During the drilling of observation well 12, cores 

were taken from various depths. Coring of the poorly 

consolidated, sandy receiving zone at 960 ft (293 m) 

was difficult, but several kilograms of aquifer material 

was obtained by screening. This material was sealed in 

a plastic container and remained moist until laboratory studies were conducted.

CHARACTERIZATION OF AQUIFER MATERIAL

The chemical and physical properties of the aquifer 

material from the receiving zone were characterized by 

several methods. Particle size analysis was accomplished by wet-sieving and sedimentation after 

mechanical dispersion at pH 9.5 with NaOH. Aquifer 

pH was determined on duplicate 10-gram samples in 

deionized water with a solid:liquid ratio of 1:1. The 

suspensions were allowed to stand for 1 hour and 

stirred during reading of pH. Free iron was determined 

by the citratedithionite method of Mehra and Jackson 

(1960), total Kjeldahl nitrogen by the method of 

McKenzie and Wallace (1954), and organic and inorganic carbon by the method of Malcolm and others 

(1973).

Mineralogical analyses were accomplished by X-ray 

diffraction and thin-section techniques. X-ray diffraction analyses were conducted by the authors on sizefractionated, K-saturated and Mg-saturated samples 

placed on ceramic mounts by the method of Kunzie and 

Rich (1959). Thin-section analyses and porosity and 

specific gravity determinations were performed by the 

U.S. Geological Survey Hydrologic Laboratory in Denver, Colo.

WASTE CONSTITUENT ANALYSES

A bulk sample of the industrial organic waste was 

obtained from Wilmington, N.C., on November 7,1973. 

The organic and inorganic analyses of this sample as
28 SUBSURFACE ORGANIC WASTE INJECTION, NORTH CAROLINA

presented in tables 3 and 4 show that the sample is 

representative of the injected waste. All the methods 

for specific organic component identification and DOC 

in the original waste and the reacted effluent waste 

from the laboratory aquifer-waste reactivity tests were 

performed as described in the previous method section. 

The identification of organic components sorbed on the 

aquifer material during testing was accomplished by 

placing 10 grams of aquifer-core material into a 250-ml 

glass Erlenmeyer flask, acidification to pH 1 with 

H2SO4, and triple extraction with 100-ml portions of 

ether after 24-hour equilibration at room temperature. 

Specific conductance and pH were determined on 

standardized laboratory equipment. Total iron, silica, 

and sulphate were determined by the authors by standardized Technicon Autoanalyzer procedures. Sodium, 

calcium, magnesium, and chloride were determined on 

the reacted waste effluent by the U.S. Geological Survey Central Laboratory in Salt Lake City, Utah.

MODIFIED HASSLER SLEEVE CORE HOLDER

The laboratory waste-aquifer reactivity studies were 

conducted in a modified Hassler sleeve core holder as 

shown in figure 24. The core tester was designed according to the general specifications as supplied by 

Charles D. Haynes of Austin, Texas. The advantages of 

this design include the testing of large amounts of core 

material of various sizes and lengths, the use of rubber, 

plastic, or Teflon sleeves, and the implementation of 

confining pressure, which is analogous to overburden 

pressure and (or) hydrostatic pressure, if Teflon sleeves 

are used. This design also enables the maintenance of a 

pressure differential between the confining pressure 

and the internal core pressure.

PRESSURIZATION CORE-TESTING APPARATUS

The schematic of the pressurization core-testing apparatus is shown in figure 25. The apparatus is pressurized with nitrogen gas from a large reservoir tank. 

The conversion of gas pressure to hydrostatic pressure 

in the hydraulic separator and the liquid accumulator

/End cap

Body

O-ring Confining y 

Pressure

FIGURE 24. Diagram of modified Hassler sleeve core holder.

Collection

FIGURE 25. Schematic diagram of pressurization core-testing apparatus.

tank prevents possible problems with entrained gases 

within the core or possible air leaks from the confining 

pressure reservoir into the sleeve core holder. The driving force for the movement of liquid through the 

aquifer material is hydraulic pressure from the hydraulic separator. The maintenance of a constant and 

accurate gas pressure to within 2 psi at 500 psi was 

accomplished by a Grove pressure regulator and a 

United States mirrored scaled gage.

Adequate valving arrangements enabled the refilling of the hydraulic separator from a plastic liquid 

refilling reservoir while maintaining a constant high 

pressure within the core holder. The conductivity and 

temperature of the core effluent were monitored with 

inline sensors at the outlet of the core holder. All components were connected with 0.125 inch (3.17 mm) 

stainless steel tubing except the tygon tubing for collection and monitoring of the reacted waste effluent 

from the core holder.

EXPERIMENTAL DESIGN

In order to accomplish the laboratory waste-aquifer 

reactivity experimental objectives, three experiments 

were conducted. Experiments 1 and 3 emphasized 

chemical changes which were manifested by changes 

in the liquid waste, whereas experiment 2 emphasized 

chemical reactivity which could be manifested by 

chemical and physical changes within the aquifer core 

material.

Experiment 1 was designed to simulate the passage 

of the waste front through an observation well or a 

given static point within a waste-receiving zone. The 

Teflon sleeve of the core holder was packed with 

aquifer material and the waste injected into the pressurized core at a rate of 2 ml/hr which approximated a 

waste movement under field conditions of 0.6 ft/day 

(0.2 m/day).

Experiment 2 was designed to simulate changes 

which would be manifested within the aquifer core
LABORATORY WASTE-AQUIFER REACTIVITY STUDIES 29

material with passage of the waste front extending 

into the slow-reactivity zone. To accomplish this, waste 

was injected into a pressurized aquifer core at a flow 

rate of 4 ml/hr, which approximated a waste movement 

under field conditions of 1.25 ft/day (0.38 m/day). The 

organic and inorganic composition of the reacted waste 

effluent was monitored as in experiment 1. At the end 

of experiment 2, the reacted core was fractionated into 

eight equal sections and analyzed for physical and 

chemical changes.

Experiment 3 was designed to simulate changes 

which a unit of the very front edge of the injected waste 

would undergo as it moved outward through the injection zone from the injection well. To accomplish this 

objective, a given amount of waste was passed or 

injected through successive fresh cores of aquifer 

material.

TESTING THE PRESSURIZATION 

CORE-TESTING APPARATUS

LEAK TESTING

The Hassler sleeve core holder was designed to accept Teflon sleeves. It was assumed that a confining 

pressure, simulating overburden pressure, greater by 

150 to 200 psi (pounds per square inch) than the internal" core pressure, simulating bottom hole injection 

pressure, would facilitate the seal between the end of 

the Teflon sleeve and the core-holder plug. The application of appropriate confining pressure greater than 

internal core pressure may also prevent channeling at 

the interface between the core material and the Teflon 

sleeve.

The core-testing apparatus was first tested with 

sand in the core holder. Internal core pressure and 

confining pressure were adjusted to 450 and 600 psi, 

respectively. Chloride breakthrough curves, conductivity breakthrough curves, and the drop in water level 

within the accumulator tank indicated leakage. With 

confining pressure exceeding the internal core pressure by 150 psi, the 1.5-inch (38.1-mm) Teflon sleeve 

with 0.094-inch (0.38-mm) wall thickness was slightly 

deformed, which probably added to the leakage at the 

plug seal. An increase in the milled thickness of the 

Teflon sleeve, variation in packing and tightening of 

the core holder, and the reduction of confining pressure 

to that of internal core pressure at 450 psi failed to 

solve the initial leakage problem.

The leakage problem was resolved by milling a 2 

degree undersize taper on both ends of a thicker walled 

(0.187 inch or 4.75 mm), more rigid Teflon sleeve with 

confining and internal pressures both at 500 psi. A 

sodium chloride solution conductivity breakthrough 

curve for medium sand in this sleeve at a flow rate of 

100 ml/hr is shown in figure 26.

After the specific conductance of the effluent salt 

solution was essentially the same as the input solution, 

the flow was stopped, and the core allowed to stand 

under pressure for a 15-hour period. After standing, 

the specific conductance of the effluent remained constant at the value of the specific conductance of the 

input salt solution. This test insured a leakproof system for the waste-aquifer core reactivity experiments.

During the initial pressurization of the core holder 

with confining and internal pressure, it is essential to 

increase both pressures at the same rate or possible 

leakage will occur at the junction of the end plug and 

the Teflon sleeve. It is also essential that during the 

refilling of the hydraulic separator with fresh waste 

during experiments 1 and 2 that the confining pressure 

and internal core pressure remain constant at 500 psi. 

Adequate valving isolates the core holder from the 

hydraulic separator. After filling the hydraulic 

separator, that portion of the system is first returned to 

500 psi before simultaneously returning the confining 

and internal core pressure to the entire system.

PACKING THE TEFLON SLEEVE WITH AQUIFER MATERIAL

The aquifer material used in the laboratory studies 

was maintained in a moist condition (approximately 11 

percent moisture by weight) in a sealed plastic container until used for experimentation. The moisture in 

the aquifer sample was diluted native ground water.

In preparation for sleeve packing, the top tightening 

ring was placed on the top end plug. The Teflon sleeve 

was fitted snugly to the end plug and held in place by a 

ring stand clamp. Small portions of representative 

aquifer material were packed into the Teflon sleeve 

with a glass rod until the sleeve was approximately

24,000

EFFLUENT VOLUME, IN MILLILITRES

FIGURE 26. Specific conductance breakthrough curve during leaktesting of Hassler sleeve core holder.
30 SUBSURFACE ORGANIC WASTE INJECTION, NORTH CAROLINA

one-fourth filled. In experiments I and 2, native 

ground water was slowly introduced into the sleeve 

from the bottom through the end plug displacing most 

of the air within the column. Ground water addition 

was stopped when the water level reached the uppermost surface of the aquifer material. This process was 

repeated several times until the Teflon sleeve was 

filled with aquifer material. A stainless steel screen 

was then placed on top of the aquifer material. The 

packed sleeve was inserted into the body of the core 

holder and both ends screwed tight. The core holder 

with packed sleeve in place was inverted and secured 

into place such that the screen was then at the bottom 

of the column.

In experiments 1 and 2, the packed core was equilibrated with over 500 ml of native ground water before 

introduction of the industrial waste.

A minimum dilution of the injected waste by native 

ground water was desired in experiment 3. The four 

cores in this experiment were packed only with firm 

tapping with a glass rod. The reacted waste from each 

successive pass through previous cores was slowly introduced into the bottom of the new core at low pressure. The waste slowly filled the packed core displacing 

the entrained air. After the column was filled, the 

stainless steel screen centered into place, the end plug 

inserted and tightened, the core holder was inverted 

and then pressurized.

All experiments were conducted with confining pressure and internal core pressure remaining constant at 

500 psi. The same Teflon sleeve, which was 13 inches 

(330 mm) in length, 1.25 inches (3.17 mm) inside 

diameter, and 0.187 inches (4.75 mm) in thickness, was 

used in all experiments. The packed core of aquifer 

material in each experiment was approximately 11.75 

inches (295 mm) in length, 410 grams in weight on an 

oven dry basis having a specific gravity of 2.68 g/cm3 , 

and a pore space of 33 percent, which resulted in a 

calculated pore volume of 76 ml. The compressibility at 

500 psi was approximately 2 percent. The dead volume 

in the effluent end of the column was approximately 5 

ml.

All laboratory experiments were conducted at room 

temperature, which fluctuated within ±3°C of 25°C. 

This temperature approximated the temperature 

within the receiving zone at the injection site.

EXPERIMENT 1 KINETIC STUDY OF WASTE

This experiment was designed to simulate the passage of a waste front through an observation well or a 

static point within a waste-receiving zone. Sampling 

during experiment 1 as shown in table 11 was conducted by collecting increment samples at 5-hour 

intervals over a 6-day period at an average flow rate of 

2 ml/hr. The actual flow rate during the 10-ml sample

collection was approximately 15-20 ml/hr. Analyses 

were performed on the waste effluent, but no analyses 

were performed on the core material at the end of the 

experiment.

The inorganic aspects of experiment 1 were essentially duplicated in the waste effluent monitoring portion of experiment 2 with the exception that the flow 

rate was 4 ml/hr with the collection of a 20-ml sample 

every 5 hours. The inorganic waste effluent composition of experiment 2 will be discussed along with experiment 1.

The breakthrough data and breakthrough curves for 

DOC, chloride, and sodium as shown in tables 11 and 

12 and figures 27 and 28, respectively, indicate that 

the pore volume of each experiment is between 70 and 

80 ml, which verifies the calculated value of 76 ml. The 

experimental pore volume is substantiated by the coincidence of the inflection point of the breakthrough 

curves and the 50 percent concentration factor, both of 

which are suggestions of pore volume. The breakthrough curve for chloride should be the same or precede the DOC breakthrough, because some organic 

material is sorbed, whereas chloride is not. This appears to be the case in experiment 2, but both chloride 

and sodium lag DOC in experiment 1. The apparent 

discrepancy may be due to the fact that most parameters such as DOC, chloride, and sodium can be more 

accurately determined at low to moderate concentrations than at high concentrations. DOC concentrations 

are low and chloride concentrations are high at the 

initial portion of the breakthrough curve. The insensitivity of the chloride data is also suggested by large 

changes in pH and DOC while the chloride concentration remains constant.

The DOC breakthrough lags the chloride and sodium 

breakthrough throughout experiment 2 and for the 

greater portion of experiment 1. The lag of the DOC is 

much more pronounced with decreasing pH of the 

effluent waste. Increased sorption of organics on the 

core with decreasing pH is expected as physical sorption and anion exchange is facilitated at lower pH's.

The marked solubilization of Fe and SiO2 is shown in 

tables 11 and 12 and figures 29 and 30. Silica dissolution precedes Fe dissolution and then reaches a steady 

state concentration of near 70 mg/1. Silica solubilization appears to be somewhat independent of Fe solubilization, is independent of pH effects in the pH 

range of 5-7 in the experiments, and appears to be 

initially dependent only on the concentration of the 

waste. Fe dissolution on the other hand appears to be 

more dependent on pH than DOC concentration because no solubilization occurs until the pH of the 

aquifer core material is reduced to approximately pH 

6. Below pH 6, Fe solubilization appears to be pH 

independent, but is dependent upon the kinetics of
DOC CONCENTRATION, IN MILLIGRAMS PER LITRE

SODIUM CONCENTRATION, IN MILLIGRAMS PER LITRE

DOC CONCENTRATION, IN MILLIGRAMS PER LITRE

CHLORIDE CONCENTRATION, IN MILLIGRAMS PER LITRE

I__________I__________I__________I__________I

SODIUM CONCENTRATION, IN MILLIGRAMS PER LITRE tO i 01 bo

i^.^. CO CO tO 

OlOOl OOl

co to to to to

OCOOO -JO1

co to to to to

OCOOO -J Ol 

OOOOO

tOI-i|-iOO COCOOOOO-J -JOlOlOlOl ^.^-CO

OOiOOiO OiOOiOOi OOiOOiO OiOO

^li^COtOI-> OCOOO-JO1 Oi^.cotoi-' ocoo

ji>^cotoi-> ocpoo-joi en ^ co to i-" ocoo

OOOOO OOOOO OOOOO OOO

I-i I-i tO I-i tO tOtOtOtOtO tOCOCOCOt^. t^-OlOlOOCO 1-itOO

Ol -J O CO Ol 0^.01^-3^31 l»tOCl^-alo Ijlljl^OOlo l-i^i O

OOlOOO OOOOO OOOOO OOOOO OOO

OOOOO OOOOO OOOOO OOOOO OOO

01 01 01 01 01 en en en en en 01 01 01 01 01 0101010101 oioio

to to to co co co ^. k. bi bi bi <i <i bo bo coi-'i-'i-'iso bobob

OiOOOOOO OiOOiOOi OOOiOOl OOOOO OOO

-J -J -3 -J -J -J-3-J-J-J -J-JO1O1O1 O1O1O1O1O1 t^. t^. C

-J-JO1O1O1 OlOlt^-l-'tO tOMCOOOOO Oll-iOOOlO t^.l-'tO

OOOOO OOOOO OOOOO OOOOO OOO

OOOOO OOOOO OOOOO OOOOO OOO

000000101 oien^-coto tot->cocoi -^

tOCOO-J-J l-'l-'tOCOCO l-'tO*«-Ol Ct

^ I to

00 | CO OI-iO

00^.^

~J~J~J~J~J ~J~J~J~JO1 O1O1O1O1O1 OlOlOlOlOl t^t^CO

CO CO tO tO h- > tO 1 ' O O CO 00 Ol t^ 1 'CO CO O ~J it*, h- 1 -J CO C

61 5 1

co to

§1 §1 1

ii ii i

l-l 

00 CO 1 I CO CO I I

l-l 

CO -J tO 

I-1 I tO I CO 1 

0 1 0 1 0 1

£» CO CO

to co to

SIM §i i i §

I-1 I-1 l-l 

tO I I I Ol 1 1 00 

00 1 1 1 00 1 I 00

l-l 

CO -q Ol 

Ol 1 1 1 Ol 1 | O 

CO I I I CO 1 1 0

to co co 0

I-i O CO tO 

CO 1 CO Ol O

Ol O Ol O

to to i-

II o o O

II O O O

to to co c

1 CO -q I-i C

1 00 00 O O

Js3 *>. Ol -

"co "to "k 0

I Ol O O O

1 Ol O O O
32 SUBSURFACE ORGANIC WASTE INJECTION, NORTH CAROLINA

TABLE 12. Laboratory chemical data for waste-aquifer reactivity, experiment2 (flow rate=4 mllhr)

Time 

(hr)

0

5

10

15

20

25

30

35

40

45

50

55

60

65

70

75

80

85

90

95

100

105

110

115

120

125

130

135

140

145

150

155

160

165

170

175

180

185

190

195

200

205

210

215

220

225

230

235

240

245

250

255

260

265

270

275

280

285

290

295

300

305

310

315

320

Fraction 

number

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

25

26

27

28

29

30

31

32

33

34

35

36

37

38

39

40

41

42

43

44

45

46

47

48

49

50

51

52

53

54

55

56

57

58

59

60

61

62

63

64

65

Cumulative 

volume

(ml)

20

40

60

80

100

120

140

160

180

200

220

240

260

280

300

320

340

360

380

400

420

440

460

480

500

520

540

560

580

600

620

640

660

680

700

720

740

760

780

800

820

840

860

880

900

920

940

960

980

1000

1020

1040

1060

1080

1100

1120

1140

1160

1180

1200

1220

1240

1260

1280

1300

Specific 

conductance 

(jimhos/cm 

at25°C)

27,800

26,900

22,500

17,500

16,100

15,300

14,900

13,730

12,380

11,000

10,750

10,500

10,150

10,250

9,940

9,850

9,690

9,560

9,170

9,170

9,050

9,050

8,290

7,900

8,040

8,160

7,000

8,160

7,720

7,460

7,720

7,720

7,650

7,710

7,800

8,040

7,780

7,630

7,360

7,600

7,580

7,400

7,420

7,160

7,150

7,120

7,080

6,810

6,840

6,910

6,920

7,000

6,740

5,150

6,740

6,760

6,630

6,370

6,440

6,310

6,120

5,990

5,940

6,190

5,990

Concentration in mg/1

pH

7.50

6.30

5.90

5.60

5.30

5.10

5.00

4.90

4.85

4.75

4.70

4.65

4.60

4.55

4.50

4.48

4.45

4.40

4.35

4.35

4.35

4.35

4.30

4.30

4.30

4.25

4.20

4.15

4.15

4.15

4.20

4.15

4.15

4.10

4.10

4.10

4.10

4.10

4.10

4.08

4.05

4.05

4.00

4.00

4.00

4.00

4.00

4.00

4.00

4.00

4.00

4.00

4.00

3.95

3.95

3.95

3.95

3.90

3.90

3.90

3.90

3.90

3.90

3.90

3.90

DOC

1.5

1270

2820

3510

4320

4700

5050

5050

5750

5850

5800

5800

6000

6200

6300

7000

7000

6600

7150

7100

7050

6950

7150

7250

6900

6900

7450

7200

7200

7300

7400

7400

7200

7550

7200

7500

7600

7600

7500

7550

7350

7400

7400

_

7600

_

7700

_

Fe

0.3

0.3

2.0

9.5

12

16

24

_

37

41

_

48

49

_

58

67

70

79

_

80

_

_

_

90

_

95

93

96~

97

102

96

_

99

_

99

112

113

108

Si

11

20

32

53

56

59

63

64

64

_

65 .

68

68

70

68

_

66

65

67

_

72

69

_

72

72

69

71

_

60

_

69

56

56

54

56

_

57

Na

6100

5000

3900

3000

2500

_

1600

_

1100

780

670

400

340

_

230

_

170

_

140

_

120

_

100

88

78

_

75

Ca

490

1100

1800

2100

2500

_

2800

_

2800

2800

2800

2600

2600

_

2400

_

2400

_

2400

_

2300

_

2300

2200

2100

_

2000

Mg SO4

250 420

240 400

210 350

180 330

170 300

 290

140 280

_ _

120 220

 

110 160

 

110 90

 

 20

95 

 

 

92 

 

_ _

80 <1

 

 

78 

_ _

 

 

74 <1

 

_ _

 

70 

 

 

66 

 

 

 

66 

 

 

 

62 

 

 

 

 

59 <1

 

 

 

Cl

10,200

8,200

6,600

3,800

_

2,200

_

1,460

_

880

600

_

360

_

180

_

160

_

_

120

100

Sample sacrificed for gas analysis

7800

_

7850

_

7850

109

108

110

_

114

115

56

_

58

54

56

54

55

38

_

1900

 

 

 

 

56 <1

 

 

 

 

 

 
LABORATORY WASTE-AQUIFER REACTIVITY STUDIES 33

TABLE 12. Laboratory chemical data for waste-aquifer reactivity, experiment 2 (flow rate =4 mllhr) Continued

Time

(hr)

325

330

335

340

345

350

355

360

365

370

375

380

385

390

395

400

405

410

415

Fraction 

number

66

67

68

69

70

71

72

73

74

75

76

77

78

79

80

81

82

83

84

Cumulative 

volume 

(ml)

1320

1340

1360

1380

1400

1420

1440

1460

1480

1500

1520

1540

1560

1580

1600

1620

1640

1660

1680

Specific 

conductance 

(umhos/cm 

at25°C)

5,990

5,940

5,940

5,810

5,680

5,860

5,860

5,630

5,660

5,800

5,800

5,740

5,660

5,660

5,610

5,550

5,590

5,525

5,525

pH

3.85

3.85

3.85

3.80

3.80

3.80

3.80

3.80

3.80

3.80

3.80

3.80

3.80

3.80

3.75

3.75

3.75

3.75

DOC Fe

 108

 

7850 110

 

 108

_ _

 112

 

7900 110

 

 109

 

 109

 

 112

_ _

 

 

7900 110

Si

54

 

52

54

58

_

53

56

56

57

Concentration in mg/1

Na Ca Mg SO4 Cl

_ _ _ _ _

 

 

 

23 1700 49 <1 

_ _ _ _ _

 

 

 

 

_ _ _ _ _

 

 

20 1700 50 <1 

 

_ _ _ _ _

 

 

 

mg/l/day in three independent measurements during 

experiments 1 and 2. The reported values of Fe are 

corrected for background and solubilization within the 

apparatus. This small concentration of background Fe 

concentration should have no effect upon the rate of Fe 

solubilization from aquifer material. The high 

background concentration of Si in the injected waste 

probably had an effect upon Si dissolution of aquifer 

material. The high initial Si concentration probably 

decreased the rate of Si dissolution and probably decreased the total amount of Si dissolution because the 

high background enabled pseudo-equilibrium concentrations of Si to be attained more quickly than if no Si 

were present in the initial waste.

Specific conductance and pH are gross chemical indicators which are affected by a number of interdepeno: so i-

***

A 

~~1~

300

PORE VOLUMES 

10 15

I ____L

600

~T~

900

I 

1200

 Iron 

A Silica

20

u_

90 1

1C

o

I

60 Z

z"

o

Icc

30 Z

1800

EFFLUENT VOLUMES, IN MILLILITRES

FIGURE 29. Iron and silica dissolution during experiment 2.

dent chemical parameters. Therefore, pH and specific 

conductance are of limited usefulness except as general 

continuous monitoring indicators.

The initial appearance of gas at the outlet of the core 

holder at fraction 11 during experiment 1 was accompanied with a large drop in pH from 6.80 to 6.20 and an 

abrupt appearance of dissolved Fe. The initial appearance of gas during experiment 2 occurred in fraction 3 

accompanied by incipient Fe dissolution. The pH was 

lower at pH 5.9 due to the rapid flush of unreacted 

waste acids. Although all the CCte gas produced during 

carbonate dissolution within the core was believed to 

have remained in solution while within the core, outgassing of CO2 during sampling was an immediate

OIS

Ul

cc

h;

_l

CC

Ul

0. 

W 60 

<

CC

O

_l

_l

i

? 40

Z 

O

1-

<

CC1-

g 20

O

o

<

o

_i 

w 

0

1 1 1

A A

A^A "A '

A 

A* *

* 

A

A 

A

A

A

A Iron

_ * A Silica

A

* 

PORE VOLUMES

 ! 

1234

1 1 1

1 I 1

£.\l\l CC

t

1C 

Ul

u.

5 

150 < 

0

.

_l

1

Z

100 Z

o

1-

cc1-

z

Ul

o

50 o

O

Z

o

1C

0 0

100 200

EFFLUENT VOLUME, IN MILLILITRES

FIGURE 30. Iron and silica dissolution during experiment 1.
34 SUBSURFACE ORGANIC WASTE INJECTION, NORTH CAROLINA

manifestation of carbonate dissolution. The marked 

increase in Ca content of the waste effluent as high as 

4,300 mg/1 during experiment 1 was an accurate indicator of carbonate dissolution. Gas effervescence during sample collection at the end of experiment 1 and at 

fraction 20 of experiment 2, occupied over 50 percent 

by volume of the collection tube.

During experiment 2, gas effervescence declined 

with Ca concentration. Only small amounts of gas remained at fraction 50, and gas was essentially absent 

after fraction 75. Ca concentrations did not approach 

zero during experiment 2 becaue the concentration of 

the injected waste was 1,400 mg/1.

The carbonate in the injection zone was probably low 

in dolomite because the Mg concentration constantly 

decreased at the expense of Ca. Magnesium and 

sodium, which were competitive with Ca for the exchange sites on the native aquifer material, were 

gradually leached from the core with Ca and hydrogen 

becoming the dominant exchange ions.

EXPERIMENT 2 CORE SOLUBILIZATION STUDY

Experiment 2 was designed to simulate changes 

which would be manifested within the aquifer material 

with the passage of the waste front extending into the 

slow-reaction zone. Sampling of the waste effluent during this experiment as shown in tables 13 and 14 was 

conducted at 5-hour intervals over an 18-day period at 

an average flow rate of 4 ml/hr. At the termination of 

experiment 2, the waste in the pore space within the 

core was displaced by passing 180 ml of native ground 

water through the core. At this volume, the specific

conductance of the effluent was constant at the specific 

conductance of the native ground water. The core holder was then disassembled, the aquifer core material 

extruded from the Teflon sleeve, and the core fractionated into eight equal sections of 1.5 inches (38 mm). 

Sections 1 through 8 were numbered from the top 

(waste entry end) of the column.

The lag in the DOC breakthrough curve behind 

chloride during experiments 1 and 2 as shown in figures 26 and 27 indicates that organic components are 

being sorbed onto the aquifer material throughout the 

entire duration of both experiments. In addition to 

DOC, six specific organic compounds (formaldehyde, 

acetic acid, formic acid, phthalic acid, terephthalic 

acid, and p-toluic acid) were monitored. These compounds collectively comprised over 80 percent of the 

DOC in the waste. All of these compounds except formaldehyde were sorbed onto the aquifer core material.

The breakthrough curve and breakthrough data for 

formaldehyde during experiment 2 as shown in figure

-Tf^""-

PORE VOLUMES

FIGURE 31. Relative sorption of formaldehyde, acetic acid, and formic acid during experiment 2.

TABLE 13. Organic chemical data during waste effluent monitoring of laboratory experiment 2

Concentration (mg/1)

Time 

(hr)

0

5

10

15

20

30

40

50

60

75

90

105

120

140

160

180

200

220

245

270

295

320

Waste

analysis

Fraction 

number

1

2

3

4

5

7

9

11

13

16

19

22

25

29

33

37

41

45

50

55

60

65

Cumulative 

volume

20

40

60

80

100

140

180

220

260

320

380

440

500

580

660

740

820

900

1000

1100

1200

1300

DOC

1.5

1270

2820

3510

4320

5050

5750

5800

6000

7000

7150

6950

6900

7200

7200

7600

7350

7600

7675

7750

7850

7850

7900

Formaldehyde

0

370

745

925

1200

1520

1840

1840

2080

2120

2100

2150

2100

2050

2120

2100

2020

2080

_

_

2100

Formic 

acid

_

340

780

735

863

1050

1210

1710

1660

1700

1890

2170

2030

2110

2410

2110

2470

2280

2320

2280

2800

2640

2780

Acetic 

acid

_

1980

3620

4410

5840

6510

6870

7620

8140

8610

8440

8290

8660

8190

8890

9480

10,500

9130

10,700

9690

9160

10,200

10,200

Acetic/formic 

acid 

ratio

_

5.8

4.6

5.9

6.7

6.2

5.6

4.4

4.9

5.1

4.8

3.8

4.2

3.9

3.7

4.5

4.2

4.0

4.6

4.2

3.2

3.8

3.6

Concentration (mg/1)

Phthalic 

acid

_

36

45

95

119

179

191

160

180

177

152

153

157

184

190

157

171

140

134

225

226

168

169

Terephthalic 

acid

_

56

75

145

162

209

295

280

302

364

357

343

348

303

453

334

315

356

355

289

352

330

358

p-Toluic 

acid

58

103

188

204

226

399

407

435

606

563

571

557

524

803

551

539

639

618

392

512

517

596

Phthalic: 

terephthalic: 

p-toluic ratio

1:1.5:1.6

1:1.6:2.3

1:1.5:1.8

1:1.4:1.7

1:1.2:1.3

1:1.5:2.1

1:1.8:2.6

1:1.7:2.4

1:2.0:3.4

1:2.3:3.7

1:2.2:3.7

1:2.2:3.5

1:1.6:2.8

1:2.4:4.2

1:2.2:3.5

1:1.9:3.1

1:2.5:4.5

1:2.7:4.6

1:1.3:1.8

1:1.5:2.3

1:1.9:3.1

1:2.1:3.5
LABORATORY WASTE-AQUIFER REACTIVITY STUDIES 35

31 and table 13, respectively, indicate that formaldehyde is not sorbed because its breakthrough curve is 

essentially the same as for chloride. After fraction 16, 

the formaldehyde concentration is constant at 2,100 

mg/1, which is the formaldehyde concentration of the 

injected waste. This finding suggests that formaldehyde may be used as an organic tracer under similar 

chemical conditions as existed in this experiment and 

that the degree of sorption of all other organic constituents can be measured as a difference between 

their concentration in the reacted effluent waste and 

that of the original injected waste.

Formic acid was the most strongly sorbed organic 

compound on a percent by weight basis as shown in 

figure 31 and table 13. Formic acid was sorbed during 

most of the experiment with the exception of the very 

latter stages. At fraction 16, the formic acid concentration was only 60 percent of its concentration in the 

injected waste. Formic acid sorption was marked not 

only at the initial portion of the experiment, but was 

also considerable during the middle to latter portion of 

the experiment after considerable Fe and SiQz dissolution when the pH was between 4.10 and 4.00.

The formic acid molecule is quite liable or subject to 

chemical and (or) catalytic decomposition. It is possible that the apparent sorption of formic acid was not 

sorption, but decomposition of a portion of the formic 

acid. This possible chemical or catalytic decomposition 

could have occurred with the diverse components of the 

core material until the incompatible chemical core 

constituents were consumed or possible catalytic sites 

were exhausted or hindered by sorption of other organic constituents. A possible data interpretation is 

that formic acid concentration in the waste effluent 

gradually approached its concentration within the initial waste only after the possible chemical or catalytic 

activity ceased within the core.

Acetic acid was the second most strongly sorbed organic compound on a percent by weight basis. At fraction 16, the acetic acid concentration was 84 percent of 

its concentration in the injected waste. Acetic acid is 

not initially strongly sorbed as its breakthrough curve 

parallels the non-sorbed formaldehyde component.

From fraction 8 through fraction 30, acetic acid is 

strongly sorbed coincident with marked Fe and SiCte 

solubilization. After fraction 30, acetic acid is less 

strongly sorbed and gradually attains the same concentration as in the injected waste.

The sorption of phthalic and terephthalic acids are 

only vaguely suggested during the initial waste 

monitoring portion of experiment 2 as shown in table 

13. The sorption of p-toluic acid is indicated by the 

phthalic:terephthalic:p-toluic acid ratio inclusive of 

fraction 16. The relative sorption of these three aromatic acids by waste effluent monitoring is dramatically 

manifested during the slow flow rate of experiment 1. 

As shown in figure 32 and table 14, there is initial 

sorption of all three aromatic acids. The flow rate of 

experiment 2 was too rapid to obtain the necessary 

detail for aromatic acid sorption.

Phthalic acid is strongly sorbed only during the first 

150-ml of waste input. This sorption is suggested by

PH

100 200 300 

EFFLUENT VOLUME, IN Ml LLI LITRES

FIGURE 32. Relative sorption of phthalic, terephthalic, andp-toluic 

acids during experiment 1.

TABLE 14. Organic chemical data during waste effluent monitoring of laboratory experiment 1

Concentration in mg/1

Time

(hr)

30

40

55

70

90

105

125

140

Waste

analysis.

Fraction

number

7

9

12

15

19

22

26

29

Cumulative

volume

70

90

120

150

190

220

260

290

DOC

2500

4100

5600

6500

7100

7100

7600

7700

7900

Phthalic

acid

24

42

65

150

160

217

142

164

169

Terephthalic

acid

81

113

186

273

390

324

350

338

358

p-Toluic

acid

124

193

304

428

450

481

600

591

596

Phthalic:

terephthalic:

p-toluic ratio

1:3.2:5.0

1:2.7:4.6

1:2.8:4.6

1:1.8:2.9

1:1.8:2.8

1:1.5:2.2

1:2.4:4.2

1:2.1:3.6

1:2.1:3.5

Percent of fraction DOC accounted 

for by compound

Phthalic

acid

0.010

.010

.012

.023

.021

.030

.018

.021

.021

Terephthalic

acid

0.032

.028

.033

.042

.030

.045

.046

.044

.045

p-Toluic

acid

0.050

.047

.054

.065

.048

.068

.078

.076

.075
36 SUBSURFACE ORGANIC WASTE INJECTION, NORTH CAROLINA

the aromatic acid ratio in table 14 and confirmed by 

the percentage of fraction DOC accounted by phthalic 

acid. Aproximately 50 percent of the phthalic acid in 

the waste effluent had been sorbed.

Terephthalic acid is sorbed during the first 220-ml of 

waste input. The most marked sorption occurs after 

phthalic acid sorption as indicated by the plateau in 

the breakthrough curve between 150 and 250 ml in 

figure 31, by the low aromatic acid ratio in this region 

of the breakthrough curve, and by the percentage of 

fraction DOC accounted by terephthalic acid in table 4. 

Approximately 30 percent of the terephthalic acid in 

the effluent waste through fraction 22 was sorbed onto 

the aquifer material.

The sorption of p-toluic acid during the initial portion of experiment 2 is strongly supported by the 

p-toluic acid breakthrough curve during experiment 1 

as shown in figure 32 and table 14. p-Toluic acid is 

sorbed in the same region of the breakthrough curve as 

terephthalic acid with continued sorption in the 220- to 

260-ml region. Strong sorption of p-toluic acid is indicated by the plateau in the 150- to 250-ml region of the 

breakthrough curve, by the low aromatic acid ratios in 

this region, and by the percentage of fraction DOC 

accounted by p-toluic acid. Approximately 30 percent 

of the p-toluic acid in the effluent waste was sorbed 

onto the aquifer material up through fraction 26.

The sorption of phthalic, terephthalic, and p-toluic 

acids were also confirmed by sediment extraction at 

the termination of experiment 2. The sorptive 

capacities as determined on four sections of the reacted 

core are listed in table 15. Exclusive of section 1, the 

sorptive capacities are in a ratio of 1.0:5.5:4.7. This 

ratio as compared to the ratio of these compounds in 

the injected waste (1.0:2.1:3.5), indicate a sorptive preference for terephthalic and phthalic acids with the 

greatest preference for terephthalic acid.

TABLE 15. Sorptive capacities of aromatic organic acids on aquifer 

material during experiment 2

Core section 

number

1 

3

6

8

Milligrams of acid sorbed per gram of sediment

Phthalic

0.011

.025 

.020 

.019

Terephthalic

0.090 

.117 

.106 

.127

p-Toluic

0.0059 

.116 

.106 

.081

Phthalic: 

terephthalic: 

p-toluic ratio

1:9:0.6 

1:4.7:4.6 

1:5.3:5.3 

1:6.6:4.3

The sorptive capacities as shown in table 15 should 

be considered as minimal sorptive capacities because 

some portion of the organic acids were desorbed during 

the saturation of the aquifer core material with native 

saline water at the end of the experiment. This exchange or desorption of organic compounds is assured 

by mass action theory and supported by the extremely 

low sorptive capacities in section 1 at the input end of 

the column which was in contact with the saline water

for the longest time period. The conclusion is limited 

by the fact that the clay fraction which would be expected to sorb most of the organic substances was 

somewhat depleted from section 1.

The overwhelming concentration of these compounds in the waste saturating the interstitial pore 

liquid would have precluded the analysis of sorbed 

material without flushing with native ground water. 

The ratio of the sorptive capacities suggests some limited validity of the sorptive capacities as determined 

because the ratio of the sorbed acids is markedly different from that of the injected waste. The relative 

meaning of the sorptive capacities will be discussed in 

detail after the presentation of supporting data obtained during experiment 3.

Carbonate dissolution was evident during experiment 2 by the high levels of Ca in the waste effluent 

(table 12) and by CO2 gas effervescence during waste 

effluent collection. Gas first appeared at fraction 3 and 

was present until fraction 75. Carbon dioxide gas persisted in the waste effluent much longer than expected 

for the low carbonate percentage of the aquifer material (table 16, 0.98 percent CaCO3=0.12 percent inorganic carbon) and the high organic acid concentration 

of the injected waste.

TABLE 16. Organic and inorganic carbon analyses of fractionated 

and unfractionated injection-zone aquifer material

OC ICJiCaCOs1 

________________________________(percent) (percent) (percent)

Whole aquifer material, ground.................... 0.15 (U2 6~98

Clay fraction (<2microns).............................. 1.40 .14 1.18

Silt fraction (2-64 microns)............................ .52 .22 1.82

Fine sand (0.064-0.4 mm), unground.......... .10 .84

Medium sand (0.4-1.0 mm), unground ...... ..

Combined sand (0.064-2 mm), unground....

Combined sand (0.064-2 mm), ground ........

.05

.08

.03 .09

.40

.65

.71

1 Analysis by modified Van Slyke method.

Temperature, pressure, the concentration of weak 

acid solutions, and the distribution of carbonate within 

the aquifer material are obviously important considerations for carbonate dissolution. The addition of the 

injected waste solution, acid concentration of approximately 2 percent by weight, to a sample of finely 

ground (less than 60 mesh) aquifer material at room 

temperature produced no observable gas effervescence. 

Upon standing at room temperature for 24 hours, only 

% of the carbonate was dissolved from the sample. The 

remainder of the carbonate in the sample was converted to CO2 gas upon boiling for a period of 10 minutes. On the other hand, addition of 3 percent HC1, a 

strong acid, at room temperature produced strong gas 

effervescence. Upon standing for 3 hours over 90 percent of the carbonate was converted to CO2 gas.

A large portion of the carbonate in the aquifer material is secondary cementation carbonate because no 

detrital carbonates and few carbonaceous shells are
LABORATORY WASTE-AQUIFER REACTIVITY STUDIES 37

observed with either the binocular microscope or thinsection analysis. Approximately 15-20 percent of the 

carbonate in the aquifer material is contained within 

the primary mineral sand grains which comprise over 

75 percent of the aquifer material (table 17). As shown 

in table 16, the carbonate percentage for the unground 

combined sand fraction is approximately 10 percent 

less than the ground combined sand fraction. This carbonate would only be available to react with the acid 

waste by slow diffusion processes and with breakdown 

of the mineral grains.

TABLE 17. Particle size analysis of injection-zone 

aquifer material

Percentage by weight

Gravel (> 2 mm) ....................

Coarse Sand (1-2 mm)..........

Medium Sand (0.4-1.0 mm) 

Fine Sand (0.064-0.4 mm)... 

Silt (2-64 microns)................

Clay (< 2 microns) ................

1

4

28

43

20

4

With the previously discussed supporting experimental evidence, it is readily understood why carbonate dissolution was slow during experiment 2. The 

experiment was conducted at room temperature, not 

elevated temperatures, carbonate dissolution was slow 

in the presence of the weak acid composition of the 

waste, and a portion of the carbonates were contained 

as primary mineral grains within sand grains. The 500 

psi experimental pressure may have a positive effect 

upon carbonate dissolution because the COz gas produced would remain in solution at that pressure which 

would increase the carbonic acid or hydrogen ion concentration of aquifer fluids.

Carbonate analyses of the core sections at the termination of experiment 2 indicated that only a trace 

amount of carbonate was present in the aquifer core 

material. This trace carbonate level (less than 2 percent of the total carbonate percentage) represented the 

carbonate within the center portion of undecomposed 

sand grains.

With passage of the waste through the aquifer material, the pH of the core decreased from 8.2 to 3.73, the 

pH of the injected waste. The cation exchange complex 

was changed from a mixed population of Ca, Mg, and 

Na to a predominantly Ca-H system at the end of the 

experiment.

It was hoped that the marked dissolution of SiCte and 

Fe during experiment 2 would be manifested in the 

analyses of the core material at the end of the experiment. The core material was the same reddish-brown 

color both at the beginning and the end of the experiment. Waste effluent analysis indicated that only 12 

percent of the total extractable iron (0.4 percent of the 

sample weight) was removed during the experiment. 

The redistribution of the clay fraction within the core 

and the low amount of Fe solubilized during the experiment precluded Fe analyses of the core material. The 

iron which was dissolved from the core material was 

believed to have been amorphous sesquioxide coatings. 

This conclusion is supported by the associated Mn 

analyses in table 18, because Mn, Fe, and Al sesquioxides are common coatings of aquifer grains.

TABLE \&. Fe, Al, and Mn analyses by graphite furnace technique of 

selected waste effluent fractions during experiment 2

Sample 

Designation

Tirioptivl TO7£IQt'A

P1Tnr*'Hi'Yn 4.0

50 ................................

60 ................................

90 ................................

Concentration in mg/1

Fe

.............. <.2

.............. 6.3

.............. 116

.............. 77

.............. 116

.............. 182

Al

<.7 

6.2

8.7 

5.0 

8.7 

9.7

Mn

0.17

.5

6.7 

3.6 

4.7 

4.5

The small amount of SiO2 dissolved during the experiment as compared to the overwhelming amount 

comprising primary and secondary minerals certainly 

precluded computation of SiCfe losses by core analysis. 

The high values for dissolved silica could result from 

dissolution of amorphous and crystalline clay minerals. The solubilization of Al-containing clay minerals 

is supported by the high Al values for fractions 40, 50, 

60, and 90 as shown in table 18.

The clay mineralogy of the original aquifer sample 

was approximately 25-40 percent 2:1-2:2 intergrade 

and mixed layered montmorillonite-intergrade, 25-35 

percent montmorillonite, 5-10 percent illite, 5-10 percent amorphous clay minerals, and 2-4 percent quartz. 

X-ray diffraction data at the termination of experiment 2 showed only a slight change in the stability of 

the 2:1-2:2 intergrade clay mineral. This suggested 

some removal of hydroxy Al and Fe polymers from 

interlayer space. A detailed discussion of the mineralogy of the waste-injection zone and mineralogical 

changes associated with waste injection is given by 

Malcolm, Leenheer, and Weed (1976).

EXPERIMENT 3 WASTE-SATURATION STUDY

Experiment 3 was designed to simulate a unit of 

injected waste at the very edge of the waste front as it 

moved outward from the injection well. A 300-ml sample of waste was repeatedly reacted with fresh aquifer 

material until the waste was neutralized and "saturated" with dissolved aquifer constituents. The flow 

rate for the entire experiment was approximately 20 

ml/hr. The waste was passed twice through each of the 

four consecutive cores. A 2-ml sample of the waste 

effluent was taken for specific conductance, pH, DOC, 

SiCte, and Fe analyses after each pass through the 

aquifer material. At the end of the experiment the 

waste effluent was analyzed for phthalic, terephthalic, 

andp-toluic acids.

The moisture content of the aquifer material was 11 

percent by weight. This resulted in a 15 percent dilu-
38 SUBSURFACE ORGANIC WASTE INJECTION, NORTH CAROLINA

tion of the waste when introduced into each fresh core, 

and a total dilution of 60 percent for the entire experiment. This calculated dilution factor agrees well with 

the DOC experimental data (table 19), which indicates 

an actual dilution factor of 57 percent. Specific conductance cannot be used to calculate the dilution factor 

because conductance is increased with carbonate dissolution.

TABLE 19. Chemical data during waste effluent monitoring of Laboratory experiments

Contact time Specific 

Sample Laboratory per pore conductance

Concentration (mg/1)

number

1

2

3

4

5

6

7

8

identification

Core 1-Run 1

Core 1-Run 2

Core 2-Run 1

Core 2-Run 2

Core3-Runl

Core 3-Run 2

Core 4-Run 1

Core 4-Run 2

I*" f*--~

volume (hr)

4

4

4

4

4

4

4

8

(fj. mho)

6600

8400

9000

9200

9600

9700

10,000

9900

PH

4.30

4.65

5.10

5.30

5.95

6.30

7.15

7.20

DOC

6400

6400

5600

5600

4400

4350

3500

3400

Fe

9.3

18.6

7.0

6.7

.5

.4

.2

.2

Si

49

55

49

51

44

42

28

30

The monitoring data for experiment 3 is shown in 

table 19. The pH data suggested that carbonate dissolution was initially rapid during the first pass of the 

waste through the core. Only small incremental 

changes in waste pH were observed with the second 

pass through the same core. The Fe data again showed 

the dramatic effect of pH on Fe solubilization. At pH 

values below 5, Fe dissolution was rapid, was moderate 

between pH 5 and 6, and was essentially zero above pH 

6. Silica solubilization by the waste showed the typical 

U-shaped curve for silica solubility (Jones and Handreck, 1967). Silica solubility was high at low pH and 

decreased gradually with increasing pH. Silica solubility would be expected to again increase with pH above 

pHlO.

The concentration of phthalic, terephthalic, and 

p-toluic acids at the end of the experiments were 27, 

87, and 151 mg/1, respectively. The resultant ratio of 

these three compounds were 1.0:3.2:5.6, which is very 

different from the 1.0:2.1:3.1 ratio that they appear in 

the injected waste. The low concentrations of all acids 

indicate sorption on the aquifer material and the ratio 

indicated preferential sorption of phthalic acid.

An additional experiment was designed to test the 

hypothesis that Fe complexed with phthalic acid precipitated above pH 6.5. Solutions of phthalic acid 

(0.001 M (molar)=164 mg/1) and FeCls (0.01 M=590 

mg/1) were mixed at pH 2.8. These concentrations are 

similar to phthalic acid concentrations in the waste 

and the experimental concentration range of Fe with 

waste passage within the aquifer as determined in the 

previously discussed laboratory experiments. The pH 

was increased to 6.5 by small additions of dilute 

NaOH. Iron and Fe-phthalic acid complex precipitated 

from solution. Gas chromatographic analysis on the 

supernatant solution indicated that over 50 percent of 

the phthalic acid was removed from solution into the 

precipitated phase.

The sorptive capacities for phthalic, terephthalic, 

and p-toluic acids during experiment 3 are 0.01, 0.02, 

and 0.03 mg/g of aquifer material. These sorptive 

capacities are relative and not absolute sorptive 

capacities because they were computed on the basis of 

1,600 g of aquifer core material (four cores) used during the experiment. A more correct sorptive capacity is 

believed to be 0.02, 0.02, and 0.03 because phthalic 

acid was only sorbed on the last two cores of the experiment (800 g of sediment) when the pH was above pH 

6; whereas terephthalic and p-toluic acids were sorbed 

by all the cores. This conclusion is also supported by 

the sorptive data and curves as shown in table 12 and 

Figure 32, respectively, where phthalic acid is only 

sorbed between pH 6-7, but terephthalic and p-toluic 

acids are sorbed over the entire pH range of experiment 1.

The sorptive capacities of phthalic, terephthalic, and 

p-toluic acids as determined during experiment 3 (0.02, 

0.02, and 0.03 mg/g) by waste monitoring, during experiment 2 (0.02, 0.10, and 0.10) by sediment extraction, and the sorptive curves in figure 31 during experiment 1 may mistakenly be interpreted to be in conflict. The differences really reflect the dependence of 

sorptive capacity on pH, the nature of the sorptive site, 

and the charge on the organic molecule. The composition of the reactive surface, its charge, and charge 

density, change with dissolution of Fe, SiO2, and Al. 

The reactive surfaces are primarily amorphous coatings of Fe, Al, Mn, and SiOa at the beginning of the 

experiments when pH is high. With dissolution of 

these coatings and carbonates, the reactive surface 

gradually becomes a more crystalline alumino-silicate 

clay mineral and crystalline sesquioxide surface. The 

pH within the core also gradually becomes more acidic.

The solubility of the aromatic acids, their hydrophilic character, and negative charge (acid dissociation) decreases with decreasing pH. The relative rate of 

magnitude of these changes are dependent on the configuration of the molecule and the relative changes in 

the reactive surface. All data indicate that phthalic 

acid is preferably sorbed at high pH whereas p-toluic 

and terephthalic acids are preferably sorbed at lower 

pH with less Fe on the reactive surfaces.

The 0.15 percent organic carbon component of the 

native aquifer material is also an important factor in 

organic waste acid sorption by the core. Many organic 

compounds have a profound affinity or attraction for 

like or similar compounds. The amphoteric nature of 

natural organic substances would facilitate organic 

acid sorption through the entire pH range of the experiments (pH 3.7-8.2) by hydrogen bonding, Van der 

Waals forces, or direct exchange processes.

The bridge bonding of Fe, Al, and Mn on the core 

colloids to organic acids in the interstitial waste liquid
FINAL CONCEPTUAL MODEL OF WASTE MOVEMENT AND REACTIVITY 39

was also an important possibility of organic acid sorption. The acidic functional group on the organic acid 

could actively participate in initial Fe solubilization by 

surface complexation with Fe. With time, decreasing 

pH (increased protonation potential), and increasing 

organic acid concentration, the Fe would leave the 

surface of the colloid and become sequestered by the 

organic acid. The active solubilization period or time 

which the organic acid was in contact with the Fe on 

the surface site would be manifested as organic acid 

sorption.

FINAL CONCEPTUAL MODEL OF WASTE 

MOVEMENT AND REACTIVITY

The final conceptual model of waste movement and 

reactivity was more complex and detailed than the 

initial hypothetical model. The initial model assumed 

waste movement within a single permeable injection 

zone; however, the logs and the observation well flowtest indicated that the injection zone consists of multiple subzones. Assuming independent subzones within 

the injection zone as shown in figure 33, the waste 

possibly moved preferentially into the upper subzones 

because of favorable permeability and because the density of the waste is less than that of the ground water. 

This density effect is shown in figure 33 by having the 

lighter waste solution overriding the heavier ground 

water in the lower two receiving subzones within the 

injection zone. The flow system diagrammed in figure 

33 is but one of many possibilities discussed in connection with figure 21. Therefore, waste obtained from 

observation wells may be diluted by the ground water 

within the waste-contaminated subzone because of the 

density separation. Most of the variance in the waste 

concentrations in samples obtained from wells 11, 14, 

and 15 is believed to have been due to changing dilution factors caused by changing circulation patterns 

between the waste-receiving subzones within the observation wells.

Injection well Observation 

well

Sand 

I-V . 1 Gravel 

k^-~-l Clay

Waste

FIGURE 33. Hypothetical movement of injected waste within 

injection subzones.

Evidence that all the receiving subzones within the 

injection zone were accepting waste was obtained from 

wells 1, 2, 4, and 5. Samples obtained from these wells 

which were located only 150 ft (46m) from injection 

well 1-6 were essentially free of ground water. The 

large distance gap between the observation wells of the 

initial injection network and the observation wells of 

the expanded system did not allow observation of the 

injection zone in regions where the injected .waste interfaced with the native ground water in the lower 

receiving subzones. Therefore, the distance of 

injected-waste travel in these lower subzones is purely 

speculative in figure 33.

Many of the postulations in the initial conceptual 

model (fig. 17) are valid for the final conceptual model 

shown in figure 34. This model, based on the findings 

of this study, shows features of waste movement and 

reactivity within an individual waste-receiving subzone in the injection zone. Figure 34 does not show 

vertical distribution of waste in an aquifer, but the 

percentage of waste at a particular distance from the 

injected well. Therefore, this model probably has different quantitative dimensions for each receiving subzone depending on the distance and rate of waste travel 

within each subzone. However, the relative dimensions 

and order of reactivity should have validity for each 

subzone. As with the initial model, the dimensions of 

this model expand to the right with increasing time 

during waste injection.

This final model is divided into a "waste front" and 

"waste interior" at the point where the pH of the injected waste begins to rise through neutralization reactions. Most, but not all of the ground water has been 

displaced from the receiving subzone at this point. The 

curve, relative percentage of waste to percentage of 

groundwater, was drawn with the ground water extending the waste-contaminated region because the 

density difference between the injected waste and the

INJECTION

WELL 

100

WASTE INTERIOR

pH pH pH

556 7 WASTE FRONT

WASTE 

POOL

SLOW REACTION 

ZONE

FAST TRANSITION I MICRO I Dl LUTI ON

REACTION ZONE BIAL ZONE

ZONE ZONE

WASTE MOVEMENT

FIGURE 34. Final conceptual model of injected-waste reactivity and 

movement.
40 SUBSURFACE ORGANIC WASTE INJECTION, NORTH CAROLINA

native ground water would cause stratification and 

prevent rapid mixing.

The leading zone of the waste front prior to the 

appearance of methane gas indicative of microbial activity is called the "dilution zone" because the neutralized (pH 7) waste appears as a very dilute solution 

in ground water. Data from samples obtained from 

wells 11 and 14 indicated that waste concentrations 

had to attain a certain threshold value before there 

was microbial waste decomposition. This zone may also 

represent a lag time during which the microorganisms 

are multiplying to numbers where they become significant in waste decomposition. The waste showed no 

detectable reactions within this zone, and had little 

effect on the chemical quality of the ground water.

The zone which follows the dilution zone is called the 

"microbial activity zone" because of indications of 

anaerobic waste transformations within this zone. 

Methane gas, sulfur reduction, and iron reduction were 

observed either singly or in combination at various 

periods in wells 11, 14, and 15. Two strains of 

methane-producing organisms were isolated in samples obtained from well 14 during methane production. 

However, the microbiological study revealed that the 

waste was toxic to microorganisms in moderate concentrations, and waste decomposition occurred only at 

the periphery of the waste front where waste concentrations were low.

The zone called the "transition zone" follows the 

microbial activity zone. When the waste attains toxic 

concentrations and when limiting nutrients such as 

nitrogen are gone, there will be a die-off of microorganisms in the injection zone and microbial activity 

will cease. This zone is transitional between the zone of 

microbial waste transformations and the zone in which 

chemical reactions predominate.

Most of the chemical waste-aquifer interactions were 

found to occur within the zone defined as the "fastreaction zone". The boundaries of this zone are defined 

by pH. The pH changes from pH 4 at the trailing 

boundary to pH 7 at the leading boundary. One of the 

main features of this zone is the neturalization of the 

acidic, injected waste at pH 4 by the aquifer carbonates 

and sesquioxide minerals. Observations on site at well 

9 and in experiments 1 and 2 of the laboratory wasteaquifer reactivity studies indicate that at a given point 

in receiving zone, the maximum rate of dissolution of 

carbonate coatings occurs first followed by dissolution 

of sesquioxide coatings of which the iron oxides predominate. Dissolution of both carbonates and Al, SiO2, 

Fe, and Mn contained within the grains of primary 

minerals occurs at a much slower rate than the dissolution of the coatings. High concentrations of dissolved 

calcium and carbon dioxide are features of carbonate 

dissolution, and sesquioxide dissolution is indicated by

elevated concentrations of aluminum, iron, and manganese.

Iron solubilization data from experiments 1 and 2, 

and iron precipitation data from experiment 3, suggest 

a region of iron hydroxide precipitation within the 

fast-reaction zone. As the pH of a unit of waste moving 

outwards from the injection well changes from pH 5.5 

to 6.0, hydroxide concentration increases to the point 

where precipitation of iron hydroxide occurs. This region of iron hydroxide precipitation may be a significant factor in the chemical plugging of the wastereceiving subzones because very high concentrations of 

organically complexed iron were observed in the fastreaction zone below pH 5.5, and this dissolved iron was 

essentially quantitatively reprecipitated as the pH of 

the injected waste rose during its outward movement 

and neutralization. Phthalic acid complexed with the 

dissolved iron was found to be coprecipitated with the 

iron hydroxide, and this is most likely the reason why 

phthalic acid was not found in the neutralized waste 

samples obtained from wells 11,14, and 15. The correlation of iron concentration with waste concentration 

in well 14 most likely resulted from bacterial waste 

decomposition processes; not from organic acid dissolution of iron oxide coatings because acid-solubilized iron 

should have reprecipitated before the waste reached 

well 14.

The laboratory waste-aquifer study substantiated 

the "slow-reaction zone" of the initial conceptual model 

which follows the fast-reaction zone. Reactions which 

occur in this zone are the slow solubilization of silica, 

aluminum, and iron from the crystalline primary minerals found in the waste-receiving subzones. Prior passage of acidic waste has dissolved most of the secondary coatings found on the aquifer minerals, and the 

only significant reactions which remain are the slowdissolution reactions of the primary minerals themselves. The pH in this zone is essentially the same as 

the pH of the injected waste, pH 4, because the flow 

rates and types of reactions do not significantly neutralize the waste and affect the pH.

The reaction rates in the slow-reaction zone were 

found to decrease as the quantity of injected waste 

increased until no further reactions could be observed 

between the waste and the aquifer constituents. The 

area in the subsurface in the immediate environs of the 

waste-injection well where there were no observable 

reactions was called the "waste pool." Samples obtained from wells 1, 2, 4, and 5 at the beginning of this 

study were taken from the waste pool because their 

elemental composition was essentially the same as the 

injected waste. Only after the cessation of all observable reactions can the subsurface environment be regarded as a waste storage area because it is only in this 

waste pool that the waste could be reclaimed in unal-
SUMMARY AND CONCLUSIONS 41

tered form after subsurface injection.

The various zones and interactions presented in this 

final conceptual model of waste movement and reactivity cannot be considered to be well defined at all times 

during waste injection. At the beginning of injection of 

waste similar to that from the Hercules plant, it is not 

likely that there is a microbial activity zone because 

conditions change too suddenly within the waste front 

for an establishment of a viable waste-degrading microbial population. It is only after the waste front has 

moved a significant distance from the injection well 

that its rate of movement will decrease to the point 

which allows the formation of a microbial activity 

zone. At the opposite extreme of the model, a waste 

pool cannot form until a sufficient volume of waste has 

been injected and enough time has passed so that all 

the reactive aquifer constituents have been dissolved 

and removed from the vicinity of the injection well. In 

summary, this model is a static representation of a 

dynamic situation. Specifically, this model was drawn 

to represent the various stages of reaction of the injected waste thought to exist in the subsurface after 4 

years of waste injection at which time most of the 

findings of this study were obtained.

SUMMARY AND CONCLUSIONS

The Hercules waste injection site near Wilmington, 

N.C., has provided an opportunity for studying the 

physical, chemical, and biological aspects of subsurface 

organic waste injection. Most of the waste-aquifer interactions which were predicted to occur at the inception of this study were verified by the site and laboratory studies. Differences between the initial and final 

conceptual models of waste movement and reactivity 

show however that the initial predictive model had to 

be tested with data and modified to fit the findings of 

this study.

Evidence was obtained at the site and in laboratory 

studies to substantiate the following waste-aquifer interactions:

1. Dissolution of the carbonate minerals in the injection zone by the waste organic acids.

2. Dissolution of the sesquioxide coatings on the primary minerals in the injection zone by waste organic 

acids.

3. Dissolution of the primary aluminosilicate minerals 

in the injection zone by the waste organic acids.

4. Dissolution and complexation of iron and manganese oxides by the waste organic acids.

5. Reprecipitation of complexed dissolved iron during 

waste neutralization.

6. Coprecipitation of phthalic acid complexed with 

iron during iron hydroxide precipitation.

7. Methane gas production resulting from anaerobic 

microbial waste degradation.

8. Microbial reduction of sulfates to sulfides.

9. Reduction of ferric to ferrous iron resulting from 

decreases in Eh and pH due to microbial waste degradation.

10. Retention of organic waste acids by adsorption and

anion exchange on the mineral constituents in the

injection zone at low pH values.

These waste-aquifer interactions prove that this industrial organic waste cannot be regarded as an inert 

fluid which does not react after injection into the subsurface environment. The history of the plugging of 

both injection wells after a period of waste injection 

strongly indicates that serious consideration should be 

given to the chemical compatibility of the waste with 

the fluid and minerals of the zone into which injection 

is planned. Problems of injection zone plugging may be 

due in part to the reprecipitation of aquifer constituents initially dissolved by the waste acids, and due 

to the formation of gaseous reaction products such as 

carbon dioxide and methane. Dissolution of aquifer 

solids by the complexing organic acids in the waste 

may be significant in the leakage problems at the injection and observation wells. These organic acids may 

dissolve the bond between the cement grout surrounding the well casing and the aquiclude confining beds to 

allow upward leakage of waste into shallower zones. If 

the waste leakage was due to dissolution reactions, 

this problem would be accentuated at the injection 

wells where the waste is the most acid (pH 4), the 

wannest (45°C), the density difference with the native 

ground water the greatest, and where the highest 

pressure head occurs in the injection zone.

This study has shown the importance of conducting 

compatibility tests of the injected waste with the 

aquifer material before the initiation of waste injection. The data obtained by conducting three experiments with the pressurization core-testing apparatus 

demonstrated that field hydraulic conditions of waste 

injection can be simulated within the laboratory. Most 

of the chemical interactions which occurred on-site 

were observed in the laboratory simulation of waste 

injection into cores of material from the injection zone. 

The laboratory study demonstrated precipitation and 

dissolution reactions which pointed to problems of 

aquifer plugging and leakage at the waste-injection 

site. It also better defined waste-aquifer interaction in 

a quantitative manner than did the site study. Such 

laboratory tests should also be of considerable interpretive value in waste-injection systems where 

monitor wells are absent or are determined to be a 

financially impractical part of the total injection system.

A major limitation of the site study was imposed by 

the construction features of the observation wells because they were open to various subzones within the
42 SUBSURFACE ORGANIC WASTE INJECTION, NORTH CAROLINA

injection zone. In any future study it would be desirable to install packers in the observation wells to isolate 

each subzone, so that undiluted samples could be obtained from each.

The case history of the Hercules waste-injection system is a documentation of a system which is no longer 

used for several reasons. The major problem with the 

waste appears to be its reactivity. Because the overall 

permeability of the waste-injection zone was low, the 

formation of coatings, precipitates, and (or) gases, even 

in small quantities, decreased the permeability of the 

injection zone to the point where plugging of the injection well occurred. If wastes of this type were neutralized prior to injection, the injected neutralized 

waste would not dissolve aquifer constituents such as 

iron which is later reprecipitated. Carbon dioxide gas 

would, therefore, not be formed which may constitute 

part of the plugging problem other than the small 

quantity produced by microbioal waste degradation. 

The neutralized salts of organic acids are not nearly 

adsorbed on aquifer sediments to the extent of free 

acids which may form coatings and precipitates on 

aquifer sediments. Cooling the neturalized waste prior 

to its filtration and injection would allow precipitate 

formation of any insoluble waste constitutents which 

could be filtered from the waste before injection. These 

actions would have made the waste more inert in the 

subsurface environment, thus minimizing problems 

with aquifer plugging and well leakage.

The microbiological study has shown that this injected waste is very slowly biodegradable in the subsurface environment. Although the addition of nitrogen to the injected waste may greatly increase the 

amount of microbial waste degradation and subsequent methane formation, a large amount of 

methane gas would undoubtedly be formed and would 

plug the injection zone under site conditions similar to 

that studied.

SELECTED REFERENCES

Black, Crow, and Eidsness, Inc., 1971, Engineering report on drilling 

and testing of additions to the disposal well system for Hercules 

Incorporated, Hanover Plant, Wilmington, N.C.: 103 p.

Bricker, C. E., and Vail, W. A., 1950, Microdetermination of formaldehyde with chromotropic acid: Anal. Chemistry, v. 22, no. 5, p. 

720-722.

DiTommaso, Anthony, and Elkan, G. H., 1973, Role of bacteria in 

decomposition of injected liquid waste at Wilmington, North 

Carolina, in J. Braunstein, ed., Sept. 1973, Underground Waste 

Management and Artificial Recharge: New Orelans, v. 1, p. 

585-599.

Goerlitz, D. F., and Brown, Eugene, 1972, Methods for analysis of 

organic substances in water: U.S. Geol. Survey Techniques 

Water-Resources Inv., book 5, chap. A3,40 p.

Hall, C. W., and Ballentine, R. K., 1973, U.S. Environmental Protection Agency policy on subsurface emplacement of fluids by well 

injection, in J. Braunstein, ed., Sept. 1973, Underground Waste 

Management and Artificial Recharge: New Orleans, v. 2, p. 

783-789.

Hem, J. D., 1970, Study and interpretation of the chemical characteristics of natural water [2d ed.]: U.S. Geol. Survey WaterSupply Paper 1473,363 p.

JoneSj L. H. P., and Handreck, K. A., 1967, Silica in soils, plants and 

animals: Advances in Agronomy, v. 19, p. 107-147.

Kunzie, G. W., and Rich, C. I., 1959, Certain properties of some 

Southeastern United States soils and mineralogical procedures 

for their study: Blackburg, Va., Virginia Agr. Exp. Sta., Southern Cooperative Series Bull. 61.

Lawrence, A. W., and McCarthy, P. L., 1969, Kinetics of methane 

fermentation in anaerobic treatment: Water Pollution Control 

Federation Jour., v. 1, part 2, p. 1-17.

Leenheer, J. A., and Malcolm, R. L., 1973a, Chemical and microbial 

transformations of an industrial organic waste during subsurface injection: Anaheim, Calif., Inst. Environmental Sci. Proc., 

April 1973, p. 351-360.

 1973b, Case history of subsurface waste injection of an industrial organic waste, in J. Braunstein, ed., Sept. 1973, Underground Waste Management and Artificial Recharge: New Orleans, v. 1, p. 565-584.

Le Grand, H. E ., 1955, Brackish water and its structural implications in Great Carolina Ridge, North Carolina: Am. Assoc. Petroleum Geologists Bull., v. 39, no. 10, p. 2020-2037.

 1960, Geology and ground-water resources of WilmingtonNew Bern area: North Carolina Dept. Water Resources 

Ground-Water Bull. 1, 80 p.

Malcolm, R. L., Leenheer, J. A., 1973, The usefulness of organic 

carbon parameters in water quality investigations: Anaheim, 

Calif., Inst. Environmental Sci. Proc., April 1973, p. 336-340.

Malcolm, R. L., Leenheer, J. A., McKinley, P. W., and Eccles, L. A., 

1973, Supplement II Dissolved organic carbon, in D. F. Goerlitz and Eugene Brown, eds., Methods for analysis of organic 

substances in water: U.S. Geol. Survey Techniques WaterResources Inv., book 5, chap. A3,34 p.

Malcolm, R. L., Leenheer, J. A., and Weed, S. B., 1976, Dissolution of 

aquifer clay minerals during deep-waste disposal of industrial 

organic wastes: Mexico City, Internat. Clay Conf. Proc., 1975, p. 

477-493.

McKeague, J. A., and Cline, M. G., 1963, Silica in soil solutions, 

Parts I and II: Canadian Jour. Soil Sci., v. 43, p. 70-96.

McKenzie, H. A., and Wallace, H., 1954, The Kjeldahl of nitrogen: A 

critical study of digestion conditions: Australian Jour. Chem., v. 

7, p. 55-60.

Mehra, O. P., and Jackson, M. L., 1960, Iron-oxide removal from soils 

and clays by a dithionite-citrate system buffered with sodium 

bicarbonate: Clays and Clay Minerals, 7th Natl. Conf. on Clays 

and Clay Min. Proc., 1960, p. 317-327.

North Carolina Department of Water and Air Resources, 1971, Satus 

report on the feasibility of the injection of liquid waste into 

saline ground water at Wilmington, North Carolina: Raleigh, 

North Carolina, 26 p.

Oborn, E. T., and Hem, J. D., 1961, Microbiologic factors in the 

solution and transport of iron: U.S. Geol. Survey Water-Supply 

Paper 1459-H, p. 213-235.

Peek, H. M., and Heath, R. C., 1973, Feasibility study of liquid-waste 

injection into aquifers containing salt water, Wilmington, North 

Carolina, in J. Braunstein, ed., Sept. 1973, Underground Waste 

Management and Artificial Recharge: New Orleans, v. 2, p. 

851-875.

Ringbom, A., 1963, Complexation in analytical chemistry: New 

York, Interscience Publishers, 395 p.

Siebert, M. L., and Hattingh, W. H. J., 1967, Estimation of 

methane-producing bacterial numbers by the most probable 

number (MPN) technique: Pergammon Press, Water Research, 

v.l, p. 13-19.
SELECTED REFERENCES 43

Skougstad, M. W., and Scarbro, G. F., Jr., 1968, Water sample filtration unit: Environmental Sci. and Technology, v. 2, p. 298-301.

Swenson, H. A., and Baldwin, A. L., 1965, A primer on water quality: 

Washington, U.S. Govt. Printing Office, 27 p.

Waksman, S. A., 1952, Soil microbiology: New York, John Wiley & 

Sons, 356 p.

Warner, D. L., and Orcutt, D. H., 1973, Industrial waste-water wells 

in United States Status of use and regulation, 1973, in J. 

Braunstein, ed., Sept. 1973, Underground Waste Management 

and Artificial Recharge: New Orleans, v. 2, p. 687-697.

White, W. R., and Leenheer, J. A., 1975, Determination of free formic 

and acetic acids by gas chromatography using the flame ionization detector: Jour. Chromatographic Sci., v. 13, p. 386-389.

BASIC-DATA TABLES 20-36
46 SUBSURFACE ORGANIC WASTE INJECTION, NORTH CAROLINA

TABLE 20. Organic waste analyses

Collection date (mo-day-yr)

9-14-72 7-6-73 11-7-73

Milligrams per litre

DOC ............................................

Methanol .................. . ..................

Benzole acid .................................

................ 6,700

............... 9,500

3,100

................ 1,600

................ 260

............... 1,200

............... 430

.............. 36

................ 35

6,400 

8,500 

3,300 

1,700 

0

1,100 

400 

22 

32

7,900 

10,000 

2,900 

2,100 

2,000

1,000 

360 

170 

95

[Analyzed by WRD Central Laboratory, Salt Lake City, Utan, except where noted by (a), 

Huffman Laboratory, Wheatridge, Colo., or by (b), V. C. Kennedy, U.S.G.S., Menlo Park, 

Calif. 1

pH................ ...... ...........................................

Specific conductance

(/nmhos at 25°C).

Silica (SiOz) ........... ...

Calcium (Ca) ... .....

Sodium (Na) ...................................

Sulfate(SO4)............ ...... .... .... .

Chloride(Cl)...................................

Fluoride(F)...................................................

Nitrite-nitrate (NOz-NOz)....... .................

Orthophospate (PCU) .................................

Hardness as CaCOs (Ca, Mg) ...................

Aluminum (Al), total .................

Cobalt (Co) ..................................... . . ....

Iron (Fe), total .............................................

Lead (Pb). ........... .....................................

Nickel (Ni) ...................................................

Selenium (Se)

Zinc(Zn) .............. ........................................

Analysis date

12-18-73 3-27-74

q ft q Q

4,560 4,530

Milligrams per litre

31 31

i ^ftfl i ^f\{\

qrt qo

1 Q IK

q Q

11 41

5.2 5.5

14 9 ft

0.28

3,400 3,400

3.9(a)

Micrograms per litre

3

0

5 2

260 

1,600

100

20 80

160 80

1.0

2

100 2

24

 590

6,200(b) 

5,500(b)

TABLE 22. Inorganic analyses of ground water from surficial sand

aquifer

Well

Hercules 

Supply well C 14

Zone (feet below 

land surface).

pH.... ....................................................

Specific conductance

(Mmhosat25°C).

30-60 

6-15-71

6.0

29

28-48

2-25-72 

6.6 

46

15

33-53

2-26-72 

6.1 

85

16

33-53

5-19-72 

6.0 

31

Milligrams per litre

Silica (SiOz) ......................................

Sodium (Na) ......................................

Bicarbonate (HCOs) ........................

Chloride (CD ......................................

Nitrite-nitrate (NOz-NOs)

5.0

1.8

.4

3.0

.5

4

4.0

5.2

0

.2

4.8 

2.0 

1.0 

4.9 

.6

10 

2.4 

6.4 

.0 

.3

5.7 

5.0 

3.0 

4.5 

1.4

5 

2.6 

9.0 

.0 

4.3

4.1 

1.5 

.9 

2.1

.5

7 

4.4 

3.4 

.0 

.02

Orthophosphate (POt) ... 

Residue on evaporation

at 180°C. 

Hardness as CaCOs (Ca, Mg)

22

.00

33

.000

56

25

.013

29

.010

Micrograms per litre

Iron (Fe), total ..................................

Zinc (Zn) ............................................

53

57

12

40

10

107 

115

37 

0

239 

131

TABLE 23. Inorganic analyses of ground water from 300-ft zone

Zone (feet below 

land surface).

pH....................... .......... .. ................

Specific conductance

(/nmhosat25°C).

Chloride(Cl)......................-.-.............

Nitrite-nitrate (NOz-NOs)

Residue on evaporation 

at 180°C. 

Hardness as CaCOz (Ca, Mg)

Zinc (Zn) ..............................................

13

283-293 

11-3-71

8.3

9550

2.3

32

34

1850

120

611

45

2820

1.3

.2 

.02

5220 

200

81

173

5253

77

112

1200

10

Well No.

14 15

320-330 279-299

2-25-72 2-26-72

8.1 8.2

9000 7500

Milligrams per litre

9.7 9.5

19 13

46 32

2000 1650

58 50

587 634

350 130

2780 2350

1.3 1.4

.02 .6 

.000 .000

5560 4560 

236 164

Micrograms per litre

269 225

15 0

 

16

305-325 

4-15-72

8.2

9500

11

47

45

2100

63

480

330

2480

1.3

.05 

.000

5970 

303

543

522

_

TABLE 24. Inorganic analyses of ground water from 500-ft zone

Well No.

14 15

Zone (feet below land surface) 

Collection date............................

Specific conductance 

Qu.mhosat25"C)._______

500-520 

3-4-72

7.9 

20,000

500-520 

3-5-72

7.6 

19,500

Milligrams per litre

Silica (SiOz) .........

Calcium (Ca) .......

Magnesium (Mg). 

Sodium (Na).........

Potassium (K) .....

Bicarbonate (HCOs)

Chloride (CD........................

Fluoride (F)...........................

Nitrite-nitrate (NOz-NOz)..

Orthophosphate (PO4) ...........

Residue on evaporation at.....

180°C. 

Hardness as CaCOs (Ca, Mg)

6.2

148

169

4,600

123

337

765

6,990

8.1

111

185

4,430

118

371

760

6,950

13,300

1,060

.00 

.000

.7 

.09

. 

12,800

1,040

.000

Micrograms per litre

Aluminum (Al), total. 

Iron (Fe), total .............

613

0

613

0
BASIC-DATA TABLES 47

TABLE 25 Inorganic analyses of ground waterfront 700-ftzone 

[Values in parentheses are from analysis by E. A. Jenne, U.S.G.S., Menlo Park, Calif.]

Well No.

14

Zone (feet below 694-704

land surface).

Collection date .................................................... 6-15-71

pH.................. ....................................................... 7.5

Specific conductance 27,100

Combos at 25°C).

Silica (SiOO ........................................................ 83

Calcium (Ca) ...................................................... 265

Magnesium (Mg) ................................................ 321

Sodium (Na) .................... ................................... 5,900

Potassium (K) .................................................... 212

Bicarbonate (HCO3) .................................... 358

Sulfate(S04)........................................................ 610

Chloride (CD........................................................ 9,650

Fluoride (F)................ ..................... ...... .5

Nitrite-nitrate (NOa-NOs)................................ .8

Orthophosphate (PCW ...................................... .02

Residue on evaporation 17,800

at 180°C. 

Hardness as CaCOa (Ca, Mg) _____________ 1,980

Aluminum (Al), total ........................................ 495

Arsenic (As) ....................................................... 

Barium (Ba) .................................. ..................... 

Cadmium (Cd) ................................................... 

Chromium (Cr), total ........................................ 

Cobalt (Co) .................................................. ... _

Copper (Cu)........................................................ . 120

Iron (Fe), total ................................................... 2,150

Lead(Pb)........ ......................... ........................... 

Manganese (Mn) ............................................... 180

Mercury (Hg), total ........................................... 

Molybdenum (Mo) ............................................. 

Nickel (Ni) ......................................................... 

Selenium (Se) ....................... .............................. 

Strontium (Sr) .................................................... 

Zinc(Zn) ............................................................. 35

694-704 694-704

6-13-73 10-31-73

 

28,300 28,241

727-737

6-15-71

7.4 

31,100

727-737

6-20-72

5.8 

17,900

727-737

6-14-73

4.5 

17,900

637-693

3-8-72

7.8 

25,000

Milligrams per litre 12~ 

270 

280 

5,900 

170

540

10,000

1,800

11

280

280

6,300

200

550

11,000

.4 

.08

.12

8.0

321

438

6,750

230

244

740

11,400

.4

.6

60

3,870

219

1,700

120

6,910

145

2,550

3.6

1.8

1,900

21,000

2,600

.02

22,100

10,600

.12

27

3,100

190

140

150

3,000

3.2

8,500

6.2

223

186

5,900

145

247

680

9,300

16,700

1,270

.3 

.000

Micrograms per litre

20

9

300

60

10

200

30

3,400

4

150

14

2

230

2

16,000

130

0

5,000

1

110

305

269

12,000

179

40

1,260

77,800

0 (<1)

0

2,300

170 «.2) 

150

930 (20)

90 (1.0)

310,000 (205,000)

15 «3.5)

5,200 (3300)

.1

2

880

250

19,000

200

858

(67)

(160)

TABLE 26. Inorganic analyses of ground water from well 7, 

805-1036 feet below land surface

Collection date

pH..................................

Specific conductance.. 

(jLtmhosat25"C).

6-15-71

7.5 

31,800

11-3-71

7.3 

32,500

6-13-73 

31,500

10-31-73 

32,635

Milligrams per litre

Silica (SiOa) .........

Calcium (Ca) .......

Magnesium (Mg). 

Sodium (Na).........

Potassium (K) .....

Bicarbonate (HCOs) .

......................_......

Chloride (Cl)..............................

Fluoride (F)................................

Nitrite-nitrate (NOz-NOa)

Orthophosphate (POO .............

Residue on evaporation ..........

Hardness as CaCOs (Ca, Mg)

9.4

353

370

6,900

224

233

385

12,000

.5

.3

11

346

315

6,750

155

231

280

12,000

.09

21,100

2,400

.02

20,700

2,200

.03

11

330

300

6,700

190

270

12,000

2,100

11

340

300

7,000

210

270

12,000

.3 

.11

.08

2,100

Micrograms per litre

Aluminum (Al), total. 

Arsenic (As)...............

Barium (Ba)................

Cadmium (Cd)............

Chromium (Cr), total.

Cobalt (Co) ...................

Copper (Cu)..................

Iron (Fe), total............

Lead (Pb).......................

Lithium (Li).............

Manganese (Mn).....

Mercury (Hg), total. 

Molybdenum (Mo)...

Nickel (Ni) .......

Selenium (Se)... 

Strontium (Sr). 

Zinc(Zn) ...........

502

314

222

335

211

1,792

292

190

17,300

20

0

6

400

80

20

250

40

1,400

3

250

8.2

3

250

10

2,500

60

10

1,300

0

100
48 SUBSURFACE ORGANIC WASTE INJECTION, NORTH CAROLINA

TABLE 27. Inorganic analyses of ground waterfront well 11,855-1035 feet below 

[Values in parentheses are from analysis by E. A. Jenne]

Collection date

pH ............................................................

Specific conductance 

(/irnhos at 25°C).

11-3-71

......... 7.2

32,000

1-15-73

31,800

1-26-73

7.7 

32,100

2-9-73

32,200

2-23-73

7.3 

32,100

3-16-73

7.4 

32,100

3-30-73

7.6 

31,200

4-13-73

20,600

5-10-73

31,100

6-16-73

30,100

Milligrams per litre

Silica (SiOa) ........... ..... ..... ..... ..... . ...

Calcium (Ca) ...................................... .

Sodium (Na) .............. .... ........ . .

Bicarbonate (HCOs) .............................

Sulfate (SOi).........-........... ...................

Chloride (CD...........................................

Fluoride(F)....................... .......... ..........

Nitrite-nitrate (NOa-NOs)

Residue on evaporation 

at 180°C. 

Hardness as CaCOs (Ca, Mg)

Chromium (Cr), total ... ..... ...... .... .....

Cobalt (Co) ........ ....................................

Iron (Fe), total ... ............. ............. .... ..

Lead (Pb) ............... .......................... .....

Nickel (Ni) ...... .. ....... .. ... ............ .....

Selenium (Se)

Zinc(Zn) ............ ................... ... . ..... ....

........ 8.6

......... 345

......... 308

......... 6,600

......... 155

........ 232

......... 210

... .... 12,000

.......... .6

.0 

......... .00

20,400 

2,140

......... 186

......... 251

......... 1,730

......... 284

......... 325

......... 16,600

......... 110

10 

330 

290 

6,600 

200

210 

12,000

.7 

0

.06 

2,016

30

1,700 

1

270

11 

320 

290 

6,700 

170

220 

12,000 

.5 

.01

.03 

2,000

10 

330 

290 

7,400 

170

220 

12,000 

.8 

.03

2,000

14 

320 

290 

6,600 

180

200 

12,000 

.6

920

10 

330 

300 

6,600 

200

180 

12,000 

.5 

.10

.04 

2,100

10 

320 

280 

6,800 

160

230 

12,000 

.4

2,000

10 

340 

290 

6,900 

180

210 

11,000 

.3

2,000

11 

330 

290 

6,700 

190

210 

12,000 

.5

2,000

11 

330 

300 

6,600 

180

190 

12,000 

.5

2,100

Microgrants per litre

10

1,300 

2.0

30

20

1,400 

1

30

10

1,200 

0

30

0

1,100 

1

20

10

1,200 

0

30

0

1,300 

2

150

0

1,100 

1.0

20

0 

0 

500 

80 

20

280 

40 

590 

4

420 

7.4 

0

330 

9 

25,000 

40

(9.5) 

«.2)

(.4) 

(1.2) 

(1900) 

«3.5)

(350) 

(1.4) 

«.5)

(4.2)

TABLE 29. Inorganic analyses of ground water

pH

Specific conductance 

Otimhos at 25°).

Silica (SiOa) ..............................

Calcium (Ca) ...................... .....

Sodium (Na) .................... .... ....

Sulfate (SQO. ............................

Chloride (CD........ .............. ....

Nitrite-nitrate (NOa-NOs)...... 

Orthophosphate(PO4) ............

Residue on evaporation 

at 180°C. 

Hardness at CaCOs

(Ca, Mg)

Cobalt (Co) ................................

Iron (Fe), total ............... ..........

Lead (Pb) ...................................

Nickel (Ni) .......... ............. .......

Selenium (Se) ............................

Vanadium (V) ..........................

5-8-72

7.2

25,300

6.9

663

252

.. 5,550

170

.. 2,120

980

.. 8,720

.8

.2 

.047

19,400 

2,690

.. 2,200

327

6-20-72

7.0

30,500

11

465

209

6,800

160

307

215

11,500

.8

.000

20,800 

2,020

631

2,090

8-1-72

31,600

10

330

270

6,600

150

180

12,000

.6

.01

1,900

10

0

1,200

10

1

20

5,100

1

610

0

1

2

0

18,000

40

8-3-72

31,900

10

330

280

6,400

180

190

11,000

.6

0

1,975

20 (3.4)>

 (15)1

3,600

2

 (8.9)1

10

- (96)'

8-7-72

32,000

10

330

280

6,500

170

180

11,000

0

1,975

0

0

500

20

0

20

4,200

1

660

0

0

4

3

18,000

20

Collection date

8-14-72 8-28-72

_ _

31,600 32,100

Milligrams per litre

10 10

340 320

270 280

6,600 6,700

180 170

170 180

12,000 12,000

.6 .5 .6

0 .02 

 .05

1,959 2,000

Microgrants per litre

10 10

1 1

500 0

10 10

2 1

20 20

5,300 5,400

1 4

(1.7)1 950 2,300

0 0

1 0

2 2

0 0

18,000 18,000

50 40

(83)1 

(.4)' - 

9-4-72 !

_

31,900

10

330

270

6,500

180

190

12,000

.6

0

1,934

0

0

1,200

10

1

20

8,100

2

610

0

1

2

0

18,000

30

9-11-72

_

32,100

10

330

270

6,600

160

190

12,000

.6

.01

1,900

0

1

500

10

2

20 (30)1

13,000

2

950

0

_

2

0

18,000

10

- (95)1

9-19-72 1

_

32,000

10

330

280

6,400

160

170

12,000

.6

0

1,975

0

0

700

20

1

30

7,500

2

860

0

2

12

0

8,000

90

LO-11-72 ]

_

31,400

9.5

340

280

6,500

170

170

11,000

.6

0

2,000

0

0

0

20

1

40

35,000

2

2,300

0

0

15

0

18,000

30

10-31-72

32,600

9.5

380

280

6,200

200

140

11,000'.5

0

2,100

0

0

0

20

0

30

34,000

0

2,500

0

0

0

3

17,000

70

_

'Analyst: L. Thatcher, U.S.G.S., Denver, Colo. 

2Analyst: E. A. Jenne, U.S.G.S., Menlo Park, Calif.
BASIC-DATA TABLES 49

land surface

7-3-73 7-20-73 9-14-73 10-31-73

31,600 31,300 30,500 33,300

11 11

320 330

290 290

6,300 6,800

170 170

200 210

12,000 12,000

.7 .7

2,000 2,000

11 11

320 330

290 300

7,000 6,800

190 210

160

12,000

.4 

.04

170

14,000

.3 

.10

.90

2,000 2,100

480

1

20

510

2

10

350

3

10

290

2

20 90 60 40

TABLE 28. Inorganic analyses of ground water from well 12, 838- 

974 feet below land surface

[Values in parentheses are from analysis by E. A. Jenne] 

Collection date

11-3-71 6-16-73 10-31-73

pH............................................. ........... 7.2 

Specific conductance 32,000 31,400 32,100 

(/tmhosat25°C).________________________________________

_____________________________Milligrams per litre_________

Silica (SiOz) ........................................ 9.0 7.7 3.6

Calcium (Ca) ...................................... 338 310 180

Magnesium (Mg)................................ 310 300 300

Sodium (Na)....................................... 6,650 6,600 7,000

Potassium (K) .................................... 150 190 210

Bicarbonate (HCOs) 233 

Sulfate(SO4)......................-..-..-.......... 250 240 220

Chloride (CD...................................... 11,900 12,000 12,000

Fluoride(F)......................................... .6 0.4 .2

Nitrite-nitrate(NOs-NOs) ............. .0 .0

Orthophosphate (POi)...................... .03 .1:

Residue on evaporation at 20,600 

180°C.

Hardness as CaCO3(Ca,Mg).......... 2,150_____2,000___________1.900

_____________________________Micrograms per litre_________

Aluminum (Al), total...............--.. 445 0 «1.0) 0

Arsenic (As) ........................................ 0 

Barium (Ba)........................................ 500 

Cadmium (Ca).................................... 80 (.2) 

Chromium (Cr), total....................... 20 

Cobalt (Co) ......................................... - 250 «.2) 

Copper (Cu)........................-..---...... 256 50 (.9) 

Iron (Fe), total.................................... 5,253 31,100 (31,000) 37,000

Lead (Pb).............................................. 5 «3.5) 0

Lithium (Li)........................................ 278 

Manganese (Mn)................................ 265 610 (320) 

Mercury (Hg), total............................ 10 

Molybdenum (Mo)............................. 0 «1.2) 

Nickel (Ni) .......................................... 0 

Selenium (Se)...................................... 0 

Strontium (Sr).................................... 16,600 23,000 

Zinc(Zn) ............................................. 49 30______(2.8)____40

from well 14,843-972 feet below land surface.

Collection date

11-7-72 11-13-72 11-22-72 11-30-72 12-5-72 12-13-72 12-19-72 12-29-72 1-15-73 1-26-73 2-9-73 2-23-73 6-16-73 10-31-73

32,700 32,000 31,900 31,700 32,300 30,700 31,968 31,458 20,300

7.5

21,500 31,000

7.3 

31,400 29,400 31,395

Milligrams per litre

10 10 10 10 10 10 9.7 9.0 11 11 11 12 11

330 330 330 330 310 330 330 330 310 330 320 320 320

280 280 280 280 280 270 280 280 280 290 270 280 280

6,400 6,400 6,900 6,000 6,800 6,100 6,900 6,900 6,800 6,200 6,500 6,500 6,500

170 170 190 170 200 180 170 170 180 160 170 180 180

9.9

320

280

6,600

200

170 170

12,000 11,000

.6 A

.02 0

240

12,000

.7 

.01

240

11,000

220

12,000

.03

.7 

.03

230

12,000

210

12,000

.6 

.02

250

12,000

.6 

.01

190

11,000

.5 

.02

.08

180 210

12,000 12,000

.5 .8

.04 .11

210 190

11,000 11,000

.6 .5

230

12,000

.4 

.03

.07

42,000 1,975 2,000 2,000 1,900 1,934 2,000 2,000 1,900 2,000 1,900 910 2,000 2,000

Micrograms per litre

10

0

1,000

20

1

30

18,000

1

650

0

1

5

0

18,000

60

10

11,000 8,300

0 0

30 40

20

3,900

0

100

0

0

700

10

0

30

3,400

0

280

0

1

0

4

1,900

90

4,200

0

20

1,400

2

70

3,600

2

20

10

10

1,300

1

10

1

300

10

0

30

880

0

300

0

1

0

0

 18,600 

30 20

910

3

30

0

0

400

10

0

30

1,200

0

250

0

1

1

4

19,000

40

10

2,800

3

60

(2.5)* 10

(.6)* -

(.2)* -

(6.500)2 5,400

(l.O)2 0

(620)2 

(5.7)2 80
TABLE 30. Inorganic analyses of ground water from well 15,843-977 feet below land surface

Collection date

4-26-72 6-20-72 8-1-72 8-3-72 8-7-72 8-14-72 8-28-72 9-4-72 9-11-72 9-19-72 10-11-72 6

30,800

9.9

300

260

6,400

160

1,818

pH.............................................................. 7.6 7.3 

Specific conductance 26,000 30,000 30,800 31,300 31,300 30,900 

(jianho8at25°C)._________________________________________________________ 

________________________________________________Milligrams per litre_______ 

Silica (SiOO ............................................ 7.4 11 10 10 10 10

Calcium (Ca) .......................................... 233 329 310 310 310 310

Magnesium (Mg).................................... 290 277 263 260 270 260

Sodium (Na)...?...................................... 6,550 6,650 6,000 6,200 6,200 6,300

Potassium (K) ........................................ 143 160 170 170 170 170

Bicarbonate (HCOs).............................. 2,080 245 

Sulfate(SO4)............................................ 0 225 160 170 170 180 190

Chloride (CD ....... ................. 610 11,500 11,000 11,000 11,000 11,000 11,000

Fluoride(F).............................................. 9,540 .7 .6 .6 .6 .5 .6

Nitrite-nitrate (NCfe-NOs) .9 .00 .01 0 0 .05 0

Orthophosphate (PO4) .2 .000 

Residue on evaporation at 18,400 20,1000 

180°C.

Hardness as CaCOa (Ca, Mg)________1,770 1,960_____1,900_____1,843_____1,884 1,800 

________________________________________________Micrograms per litre_______

Aluminum (Al), total............................ 1,130 907 10 10 0 (T

Arsenic (As)............................................ 

Barium (Ba)............................................ 

Cadmium (Cd)........................................ 

Chromium (Cr), total............................ 

Cobalt (Co).............................................. 

Copper (Cu).............................................. 

Iron (Fe), total........................................ 0 0 1,400 1,500 1,200 1,300

Lead(Pb)............-r.................................. 4 000

Manganese (Mn).................................... 

Mercury (Hg), total................................ 

Molybdenum (Mo).................................. 

Nickel (Ni).............................................. 

Selenium (Se).......................................... 

Strontium (Sr)....................................._. 

Zinc(Zn) .................................................. 20 10 10 30

Bromine (Br) .......................................... 

Vanadium (V) ........................................_____ _____ _______=_______=______ ______ 

^Analyst: E. A. Jenne, U.S.G.S., Menlo Park, Calif.

2Analyst: L. Thatcher, U.S.G.S., Denver, Colo.

30,900 31,900 31,500 31,400 

10 11 11

300 320 310

260 270 270

6,300 6,500 6,400

160 150 170

210

11,000

1,818

200

12,000

.7 

.07

170

11,000

.7 

.04

11 

320 

360 

6,600 

160 

190 

11,000 

.7 

1,900 1,900 2,300 

10

1,900

4

30

_ (25)* _ 

1,800 1,300

2(13)' 2

20 40

_ (60)2 _

_ (.44) 2 _

1,300

3

30

1,300

3

_ 2

30 

TABLE 33. Gas analyses 

[T, trace detected!

Well No

11 11 11 11 14 14 14 14 14 14 14 14 

Date...................................................... 6-15-71 6-21-72 7-3-73 7-20-73 9-14-73 11-73 8-1-72 8-7-72 8-14-72 10-11-72 10-31-72 11-2-72 11-22-72 11-73 

Gas phase composition, in percent by volume

Nitrogen (Nz)...............

Argon (Ar).....................

MeThane(CH4).............

Carbon dioxide (CDs). 

Water (HzO...................

Hydrogen sulfide (HzS) 

Hydrogen (Hs)................

Helium (He)....................

Oxygen (Os)....................

Carbon monoxide (CO)..

Total amount gas (ml)

9.5

.20 

70.6

2.2

1.0 

.01

10

1.1

.9

75.6

6.8

4.4 

T

94.3 

1.0 

.11 

9.7

93.4

1.24

1.18

4.84

59.7

1.2

.27

4.5

34

74.7

.99

17.5

2.46

1.0

25.2

.65

50.1

10.5

5.0

20.5

.55

53.6

11.2

5.3

35.9

7.1

40.2

10.6

5.3

68

18.4

6

4.8

68

1.03

6.8

7.3

13.6

64.1

32.8 

3.8

<1

68.0 64

 

11.6 29

1.5 1

 

T 

20 18 42 111 118 104 49 44 148 

'Analyst: J. B. Rapp, U.S.G.S., Menlo Park, Calif.
BASIC-DATA TABLES 51

TABLE 31. Inorganic analyses of ground water from well 16,843-983

feet below land surface 

[Values in parentheses are from analysis by E. A. Jenne]

TABLE 32. Inorganic analyses of ground water from wells 2,3,4, 

and 5

pH.................................................

Specific conductance 

Ou,mhosat25°C)

Silica (SiCn) ................ ..............

Sodium (Na) ...............................

Potassium (K) ...........................

Bicarbonate (HCOs) .................

Chloride (Cl)...............................

Fluoride (F)................. ...............

Nitrite-nitrate (NCn-NOs).......

Orthophosphate (PO4) .............

Residue on evaporation 

at 180°C. 

Hardness as CaCOs

(Ca,Mg)

Barium (Ba) ..... .............. .........

Chromium (Cr), total

Cobalt (Co) .................................

Iron (Fe), total ...........................

Lead (Pb) .....................................

Molybdenum (Mo) . ...................

Nickel (Ni) .................................

Selenium (Se). ......................... .

Zinc (Zn) .....................................

5-18-72 

7.7

31,000

9.8

330

323

..... 7,350

175

228

615

..... 12,200

.6

.07

.000

21,300 

2,150

..... 1,000

0

Collection date

6-20-72 6-14-73

7.2 

31,800 31,600

Milligrams per litre

10 9.7

369 340

311 300

6,750 6,600

175 190

220 

255 240

12,200 12,000

.6 .6

.00

.000 

21,000 

2,200 2,100

Micrograms per litre

1,120 10

 3

 300

 70

- 10

 280

 30

0 2,400

 2

 480

 13

 4

onn

 11

 24,000

 0

10-31-73

32,118

9.8

350

310

7,000

220

280

13,000

.3

.01

.11

2,200

0

("" 1)

(.6) -

(14) 

(5800) 2,600

«3.5) 0

(390) 

(<1 2) _

( " 5)

(80) 40

Well No.

Zone (feet below land surface) ......

pH....................................................

Specific conductance 

(ftmhos at 25°C).

Sodium (Na) ................................... ..

Chloride (Cl)..........-..-~.~............~.

Residue on evaporation at 

180°C. 

Hardness as CaCOs (Ca, Mg).-.....

2

.. 855-1025 

6-15-71 

3.9

6,560

3

660-690 

6-15-71 

4.3 

11,000

4

854-1025 

6-16-71 

4.0 

8,280

5

854-1025 

6-15-71 

4.0 

8,080

Milligrams per litre

41

1,760

24

12

4.1

0

9.6

64

3.2 

3.9

1.5

6,800 

4,500

34 

3,186 

85 

198 

56

0 

35

1.1 

5.6

4.2 

1,330

8,300

23 

2,525 

34 

2.9 

2.2

8.0 

230 

1.3 

3.9

1.3 

9,590

6,440

34 

2,364 

49 

3.2 

2.3

19 

144 

1.3 

3.9

1.1 

9,160

6,100

Micrograms per litre

Zinc (Zn) ............................................

6,900

50

8,780

450

167

3,250 

900 

31,000 

3,600 

5,900

6,800 

167 

8,280 

280 

136

7,100 

110 

8,000 

285 

125

TABLE 34. Organic analyses of ground water from well 11 

[ND, not detected]

Date

1-15-73 1-26-73 2-9-73 2-23-73 3-16-73 3-30-73 4-13-73 5-10-73 6-16-73 7-3-73 7-20-73

Milligrams per litre

Acetic acid ..

Terephthalic acid .....................

........... 13.85

........... ND

.......... ND

........... .283

4.37 

ND 

ND 

.301

9.65 

ND 

ND 

.306

18.52 

ND 

ND 

.19

20.97 

ND 

ND 

.269

22.45 

ND 

ND 

.49

24.07 

ND 

ND 

.422

26.32 

ND 

ND 

.538

29.42 

ND 

ND 

.578

41.52 

ND

ND 

.488

24.24 

ND 

ND 

.573

TABLE 35. Organic analyses of ground water from well 14 

[ND, not detected]

Date

8-1-72 8-7-72 8-14-72 8-28-72 9-4-72 9-11-72 9-19-72 10-11-72 10-31-72 11-2-72

Milligrams per litre

Terephthalic acid .....................

......... 19.67

......... ND

......... .462

......... .227

55.38 

ND 

1.78 

.856

71.98 

ND 

1.528 

.754

101.35 

.16 

1.688 

.930

85.94 

.60 

1.508 

.790

138.6 

1.42 

1.449 

.332

59.61 

1.38 

.949 

.182

474.70 

1.10 

6.648 

3.327

758.85 

1.27 

16.69 

7.45

60.23 

ND 

.856 

.398

Date

11-7-72 11-13-72 11-22-72 11-30-72 12-5-72 12-13-72 12-19-72 12-29-72 1-15-73 2-9-73

Milligrams per litre

p-Toluic acid

Terephthalic acid .....................

......... 63.81

......... 3.08

......... 1.258

......... .617

84.07 

.657 

1.386 

.723

20.00 

ND 

.468 

.200

4.90 

ND 

.131 

.062

11.66 

.95 

.301

.187

21.07 

ND 

.493 

.157

~161 

.051

5.71 

ND 

.151 

.042

.1 

.044

ND 

ND

TABLE 36. Organic analyses of ground water from well 15 

[ND, not detected!

8-3-72 8-7-72

Date

8-14-72 10-31-72 12-5-72

Milligrams per litre

DOC..................... ..

9.20

ND

.25

.15

5.5

4.13 

ND 

.242 

.064 

5.0

5.09 

ND 

.245 

.059 

5.5

ND 

ND 

ND 

ND 

3.0

ND 

ND 

ND 

ND 

1.5

f: U.S. GOVERNMENT PRINTING OFFICE 1976-777434/20