Bioaccumulation in marine organisms effect of contaminants from oil well produced water

The objective of this book is to critically summarize and interpret the scientific literature dealing with the bioaccumulation and ecotoxicology of metals, NORM, and selected organic che

Tai Lieu Chat Luong

BIOACCUMULATION IN MARINE ORGANISMS Effect of Contaminants from Oil Well Produced Water

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Contents

P r e f a c e xi

A c k n o w l e d g e m e n t s xv

C H A P T E R 1: P R O D U C E D W A T E R 1

1.1 C o m p o s i t i o n o f P r o d u c e d Water 1

1.1.1 Sources a n d T r e a t m e n t o f P r o d u c e d Water 1

1.1.2 N a t u r a l l y - O c c u r r i n g C h e m i c a l s in P r o d u c e d Water 2

1.1.3 P r o d u c t i o n C h e m i c a l s in P r o d u c e d Water 16

1.2 Volumes o f P r o d u c e d Water D i s c h a r g e d to the O c e a n 18

1.3 Fate o f C h e m i c a l s from P r o d u c e d Water in the O c e a n 19

1.3.1 M o d e l e d Dilution o f the P r o d u c e d Water P l u m e 19

1.3.2 Fate o f C h e m i c a l s in P r o d u c e d Water P l u m e s 22

1.3.3 D e g r a d a t i o n o f P r o d u c e d Water C h e m i c a l s in the O c e a n 27

1.4 Toxicity o f P r o d u c e d Water 30

1.4.1 Toxicity o f W h o l e P r o d u c e d Water 30

1.4.2 C a u s e s o f P r o d u c e d Water Toxicity 33

1.4.3 Toxicity o f P r o d u c e d Water Additives 34

C H A P T E R 2: B I O A C C U M U L A T I O N M E C H A N I S M S 37

2.1 I n t r o d u c t i o n 37

2.2 Bioavailability 37

2.2.1 Definitions 37

2.2.2 M e t a l s 38

2.2.3 Organic C h e m i c a l s 42

2.3 B i o a c c u m u l a t i o n 43

2.4 B i o c o n c e n t r a t i o n 44

2.4.1 Definitions 44

2.4.2 N o n p o l a r Organic C h e m i c a l s 44

vi Bioaccumulation in Marine Organisms

2.5

2.4.3

2.4.4

Ionizable Organic Chemicals

Metals

Biomagnification

2.5.1 Definitions

2.5.2 Organic Chemicals

2.5.3 Metals

46 47 50 50 51 54 C H A P T E R 3" A R S E N I C IN THE O C E A N

3.1 3.2 3.3 3.4 3.5 3.6 57 Arsenic in Seawater 57

Arsenic in Marine Sediments 60

Bioaccumulation and Biotransformation of Arsenic 62

Concentrations o f Arsenic in Tissues of Marine Organisms 68

Toxicity of Arsenic to Marine Organisms 72

Environmental Effects o f Arsenic in Produced Water 76

C H A P T E R 4: B A R I U M IN THE O C E A N 79

4.1 Barium in Seawater 79

4.2 Barium in Marine Sediments 81

4.3 Bioaccumulation of Barium by Marine Organisms 82

4.4 Concentrations o f Barium in Tissues of Marine Organisms 83

4.5 Toxicity of Barium to Marine Organisms 84

4.6 Environmental Effects o f Barium in Produced Water 86

C H A P T E R 5" C A D M I U M IN THE O C E A N 89

5.1 5.2 5.3 5.4 5.5 5.6 C a d m i u m in Seawater 89

C a d m i u m in Marine Sediments 92

Bioaccumulation of C a d m i u m by Marine Organisms 93

Concentrations of C a d m i u m in Tissues o f Marine Organisms 97

Toxicity of C a d m i u m to Marine Organisms 100

Environmental Effects o f C a d m i u m in Produced Water 102

C H A P T E R 6: M E R C U R Y IN THE O C E A N 103

6.1 6.2 6.3 6.4 6.5 6.6 Mercury in Seawater 103

Mercury in Marine Sediments 108

Bioaccumulation of Mercury by Marine Organisms 112

Concentrations of Mercury in Tissues of Marine Organisms 117

Toxicity of Mercury to Marine Organisms 125

Environmental Effects o f Mercury in Produced Water 129

Contents vii

C H A P T E R 7: C H R O M I U M IN THE O C E A N 131

7.1 7.2 7.3 7.4 7.5 7.6 Chromium in Seawater 131

C h r o m i u m in Marine Sediments 133

Bioaccumulation o f C h r o m i u m by Marine Organisms 135

Concentrations of C h r o m i u m in Tissues of Marine Organisms 137

Toxicity of C h r o m i u m to Marine Organisms 141

Environmental Effects o f C h r o m i u m in Produced Water 142

C H A P T E R 8: C O P P E R IN THE O C E A N 145

8.1 8.2 8.3 8.4 8.5 8.6 Copper in Seawater 145

Copper in Marine Sediments 148

Bioaccumulation of Copper by Marine Organisms 150

Concentrations o f Copper in Tissues o f Marine Organisms 153

Toxicity of Copper to Marine Organisms 157

Environmental Effects o f Copper in Produced Water 159

C H A P T E R 9: L E A D IN THE O C E A N 161

9.1 9.2 9.3 9.4 9.5 9.6 Lead in Seawater 161

Lead in Marine Sediments 164

Bioaccumulation o f Lead by Marine Organisms 166

Concentrations o f Lead in Tissues o f Marine Organisms 167

Toxicity of Lead to Marine Organisms 170

Environmental Effects o f Lead in Produced Water 173

C H A P T E R 10: ZINC IN THE O C E A N 175

10.1 Zinc in Seawater 175

10.2 Zinc in Marine Sediments 177

10.3 Bioaccumulation o f Zinc by Marine Organisms 179

10.4 Concentrations o f Zinc in Tissues o f Marine Organisms 182

10.5 Toxicity o f Zinc to Marine Organisms 186

10.6 Environmental Effects o f Zinc in Produced Water 188

C H A P T E R 11: R A D I U M ISOTOPES IN THE O C E A N 191

11.1 Radium in Seawater 191

11.2 Radium in Marine Sediments 194

11.3 Bioaccumulation of Radium by Marine Organisms 195

11.4 Concentrations o f Radium in Tissues o f Marine Organisms 198

11.5 Toxicity o f Radium to Marine Organisms 199

11.6 Environmental Effects o f Radium in Produced Water 200

viii Bioaccumulation in Marine Organisms

C H A P T E R 12: PHENOLS IN THE OCEAN 203

12.1 Phenols in Seawater 203

12.2 Phenols in Marine Sediments 206

12.3 Bioaccumulation o f Phenols by Marine Organisms 207

12.4 Concentrations o f Phenols in Tissues of Marine Organisms 209

12.5 Toxicity of Phenols to Marine Organisms 210

12.6 Environmental Effects of Phenols in Produced Water 213

C H A P T E R 13: DI(2-ETHYLHEXYL)PHTHALATE IN THE O C E A N 215

13.1 Di(2-ethylhexyl)phthalate in Seawater 215

13.2 Di(2-ethylhexyl)phthalate in Marine Sediments 218

13.3 Bioaccumulation of Di(2-ethylhexyl)phthalate by Marine Organisms 219

13.4 Concentrations of Di(2-ethylhexyl)phthalate in Tissues of Marine Organisms 220

13.5 Toxicity of Di(2-ethylhexyl)phthalate to Marine Organisms 221

13.6 Environmental Effects of Di(2-ethylhexyl)phthalate in Produced W a t e r 223

C H A P T E R 14: M O N O C Y C L I C AROMATIC H Y D R O C A R B O N S IN THE O C E A N 225

14.1 Monocyclic Aromatic Hydrocarbons in Seawater 225

14.1.1 Sources of Monocyclic Aromatic Hydrocarbons in the Ocean 225

14.1.2 Concentrations o f Monocyclic Aromatic Hydrocarbons in Seawater 228

14.2 Monocyclic Aromatic Hydrocarbons in Marine Sediments 231

14.3 Degradation of Monocyclic Aromatic Hydrocarbons in Water and Sediments 232

14.4 Bioaccumulation of Monocyclic Aromatic Hydrocarbons by Marine Organisms 233

14.5 Concentrations of Monocyclic Aromatic Hydrocarbons in Tissues of Marine Organisms 235

14.6 Toxicity of Monocyclic Aromatic Hydrocarbons to Marine Organisms 237

14.7 Environmental Effects o f Monocyclic Aromatic Hydrocarbons in Produced Water 239

C H A P T E R 15: POLYCYCLIC AROMATIC H Y D R O C A R B O N S IN THE O C E A N 241

15.1 Sources of Polycyclic Aromatic Hydrocarbons in the Marine Environment 241 15.1.1 Formation of Polycyclic Aromatic Hydrocarbons 241

15.1.2 Petrogenic Polycyclic Aromatic Hydrocarbons 243

15.1.3 Pyrogenic Polycyclic Aromatic Hydrocarbons 247

Contents ix

15.2 Polycyclic Aromatic Hydrocarbons in Seawater 254 15.3 Polycyclic Aromatic Hydrocarbons in Marine Sediments 262 15.3.1 Sorption of Polycyclic Aromatic Hydrocarbons to Sediments 262 15.3.2 Concentration of Polycyclic Aromatic Hydrocarbons in Sediments 266 15.4 Degradation of Polycyclic Aromatic Hydrocarbons 269 15.4.1 Photooxidation 269 15.4.2 Microbial Degradation 271 15.5 Bioaccumulation of Polycyclic Aromatic Hydrocarbons by

Marine Organisms 277 15.5.1 Uptake of Polycyclic Aromatic Hydrocarbons by

Marine Organisms 277 15.5.2 Metabolism of Polycyclic Aromatic Hydrocarbons

by Marine Organisms 281 15.5.3 Net Bioaccumulation and Trophic Transfer of Polycylic

Aromatic Hydrocarbons by Marine Organisms 288 15.6 Concentrations of Polycyclic Aromatic Hydrocarbons in Tissues

of Marine Organisms 293 15.7 Toxicity of Polycyclic Aromatic Hydrocarbons to Marine O r g a n i s m s 299 15.7.1 Toxicity of Unmodified PAHs 299 15.7.2 Phototoxicity of PAHs 304 15.7.3 Causes of Toxicity of Complex Mixtures Containing PAHs 308 15.7.4 Mutagenicity and Carcinogenicity of PAHs 310 15.7.5 Human Toxicity of PAHs in Seafoods 311 15.8 Environmental Effects of Polycyclic Aromatic Hydrocarbons

in Produced Water 313

REFERENCES 319

INDEX 439

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Preface

Large amounts of organic and inorganic chemicals enter estuarine and coastal marine environments from natural and anthropogenic sources Human activities have increased the flux of many naturally occurring chemicals, such as metals, naturally occurring radioactive materials (NORM), and petroleum hydrocarbons, to the ocean On the other hand, many industrial, domestic, and agricultural activities are the sole sources of an ever-increasing number of synthetic organic chemicals in the ocean

Some of these chemicals enter the marine environment in forms and concentrations that may be harmful to marine organisms and ecosystems, or to consumers, including humans, of foods from the sea A chemical must be in a bioavailable form in order to produce toxic responses in marine organisms or their consumers A chemical is bioavail- able if it is in a form that can move through or bind to the surface coating (e.g., skin, gill epithelium, gut epithelium, cell membrane) of an organism and thereby elicit biological responses Bioavailable chemicals may accumulate to high, potentially toxic concentra- tions in the tissues of marine organisms or their consumers if they have a higher affinity for some tissue compartment (e.g., lipids) than for the ambient water, or if they bind to tissue components

Naturally occurring, bioavailable chemicals are bioaccumulated by marine organ- isms, often to concentrations much higher than those in the ambient seawater Con- centrations of these chemicals in tissues of marine organisms often are in equilibrium with the natural concentrations in seawater Thus, the tissues of marine organisms con- tain natural background concentrations of many naturally-occurring chemicals, such as most metals and metalloids These background body burdens of chemicals probably are not toxic to the marine organisms However, increased inputs to the marine environment

of some of these chemicals from man's activities can result in increases in the concen- trations of the chemicals in seawater and enhanced bioaccumulation in the tissues of marine organisms, possibly to concentrations that are toxic to the organisms themselves

or their consumers, including man

xi

xii Bioaccumulation in Marine Organisms

Several solid and liquid wastes are generated during the exploration, development, and production phases of oil and gas activities in coastal and offshore marine waters Some of these wastes are discharged intentionally to the ocean In U.S territorial waters, discharges to the ocean from offshore oil rigs and platforms are regulated by National Pollution Elimination System (NPDES) permits that are issued by the U.S Environmental Protection Agency (EPA) or a state environmental protection agency des- ignated by EPA NPDES permit limitations and requirements are intended to protect the local receiving water environment and its uses from harm attributable to the permitted discharges

Effluent standards for produced water destined for ocean disposal focus primarily on limiting the concentration of petroleum (usually measured as total oil and grease) in the treated effluent The oil and gas industry treats produced water through a treatment sys- tem designed to remove oil and grease from the wastewater stream to concentrations below the NPDES limits The Final NPDES General Permit for the westem portion of the outer continental shelf of the Gulf of Mexico (GMG290000) states that produced water discharges must contain less than a daily maximum of 42 mg/L and a monthly average of 29 mg/L total oil and grease (57 FR 224:54642, November 19, 1992 and 58

FR 231:63964, December 3, 1993) Modem produced water treatment systems are capa- ble of generating an effluent that meets these requirements

Monitoring requirements in the Gulf of Mexico General Permit include periodic measurements of produced water discharge rates, toxicity of the effluent to marine organisms, level of radioactivity from 226radium and 228radium in the effluent, and bioac- cumulation of selected contaminants in marine animals in the receiving water environ- ment Flow and radium radioactivity are reported to EPA in the periodic Discharge Monitoring Report (DMR) The no observed toxic effects concentration of the effluent,

as determined with a 7-day rapid chronic toxicity test, must be equal to or greater than the critical dilution concentration determined according to a mathematical formula in the permit

The original permit required that a site-specific bioaccumulation monitoring study be performed at all existing facilities that discharge more than 4,600 barrels/day (731,000 liters/day) of treated produced water to the ocean The permit was subsequently modi- fied to enable operators to participate in an EPA-approved, industry-wide bioaccumula- tion monitoring study Twice each year, three species of marine animals, a crustacean, mollusk, and nektonic fish, were collected within 100 m down-current from the pro- duced water discharge (Offshore Operators Committee, 1997a,b) Their edible tissues were analyzed for three metals (arsenic, cadmium, and mercury), three monocyclic aro- matic hydrocarbons (benzene, toluene, and ethylbenzene), two polycyclic aromatic hydrocarbons (fluorene and benzo[a]pyrene), bis(2-ethylhexyl)phthalate, phenol, and the naturally-occurring radium isotopes, 226Ra and 228Ra

A part of the monitoring study was a review of the scientific literature on bioaccu- mulation of the metals and organic chemicals of concern to EPA by marine organisms (Neff, 1997a) That review has been updated and expanded as this book The objective

of this book is to critically summarize and interpret the scientific literature dealing with the bioaccumulation and ecotoxicology of metals, NORM, and selected organic chemi- cals by marine organisms and their consumers, with particular emphasis on chemicals commonly found in treated produced water from oil and gas wells The book also includes a summary of the range of concentrations of selected metals, NORM, and

Preface xiii

organic chemicals in the tissues of marine organisms from estuarine and marine waters

of the world These summaries are based on data tables compiled by Neff (1997a) The summary tables of tissue residues of selected metals and organic compounds in tissues

of marine organisms are not reproduced in this book but are available upon request at nef0m@battelle.org

This book is in three parts The first part deals with the sources, volumes, composi- tion, and fates in the marine environment of produced water Emphasis is placed on a summary of the available information on the chemical composition of produced waters from wells world-wide The second part of the review is a summary of our current under- standing of the process of bioaccumulation of chemicals by freshwater and marine organisms The final section of the book is a discussion of the environmental fates and biological effects of potentially toxic chemicals that have been identified at elevated (significantly higher than concentrations in ambient seawater) concentrations in pro- duced water from different sources

The second part of this book begins with a brief discussion of the mechanisms of bioaccumulation and food chain transfer of metal and organic contaminants in the marine environment The focus of this evaluation is on the bioaccumulation and food chain transfer in the marine environment of the metals and organic chemicals of envi- ronmental concern in produced water The published scientific literature on the concen- trations of several of these chemicals in the tissues of marine organisms from throughout the world is summarized A discussion is included in the third part of the book on the physical/chemical behavior in the ocean and toxicity to marine organisms of each chem- ical evaluated Integration of information about the physical/chemical behavior, bioac- cumulation, and toxicity of each compound of concern allows conclusions to be made about its potential to cause harm (its ecological risk) to marine organisms and ecosys- tems, and human consumers of fishery products, at the concentrations commonly found

in marine environments Finally, an evaluation is made of the importance of produced water as a source of chemical residues in the tissues of marine animals living near off- shore oil and gas platforms

The current scientific literature on the various topics covered in this book was accessed through detailed, computerized literature searches The focus of the literature searches was on the most recent publications on the topics of interest Many chemical analyses of concentrations of metals and organic chemicals in marine environmental matrices (seawater, sediments, tissues of marine organisms) performed before about

1980 were inaccurate or insensitive because of inadequate analytical methods and fre- quent lack of consideration of problems of laboratory contamination and matrix inter- ferences from the salts in produced water and seawater Therefore, the most recent available analytical data were used whenever possible

JERRY M NEFF

Battelle November 2001

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Acknowledgements

Preparation of this literature review was supported through contracts from the Gulf of Mexico Offshore Operators Committee to Continental Shelf Associates, Inc and to Battelle Battelle also provided financial and clerical support for completion of this book

I wish to express my appreciation to the members of the Bioaccumulation Working Group of the Offshore Operators Committee for their helpful review and suggestions during the preparation of this report I would particularly like to thank Working Group members, Dr James P Ray, Dr Robert C Ayers, Dr Stanley Cutrice, Dr Andrew Glickman, Dr Bela M James, Dr Lawrence A Reitsema, Dr Joseph P Smith, and

Dr James E O'Reilly, for their critical technical reviews of the manuscript and their many helpful suggestions for improving its quality

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C H A P T E R 1 Produced Water

1.1 C O M P O S I T I O N OF PRODUCED WATER

1.1.1 Sources and Treatment of Produced Water

During millions of years of geologic time, petroleum and natural gas may accumulate

in porous sediments (e.g., sands) trapped between layers of impermeable rock deep within the earth (Collins, 1975) Water may be trapped during millions of years with the oil and gas This water may be derived from ancient fresh or seawater (connate water) and often is as old as the fossil fuels in the reservoir When the hydrocarbon reservoir is tapped by a well, the produced fluids may contain water Also, in some oil fields, fresh

or seawater may be injected into the reservoir through injection wells to displace oil into the production wells Sometimes, this injection water channels through to the production well and is produced with the oil and gas The water produced with oil and gas is called produced water, formation water, or oilfield brine (Neff et al., 1987; Black et al., 1994; Patin, 1999)

Before the crude oil can be refined or the gas processed, the water must be removed During offshore operations, separation of the produced water from the oil and gas may take place on the production platform or the oil/gas/water mixture may be sent through

a pipeline to a shore facility where the produced water is separated from the oil and gas

If not re-injected into another well, the produced water is treated to meet local regula- tory limits for oil and grease before it is discharged to the ocean from the platform or from an ocean outfall from a shore-based treatment facility

In most of the world, national or regional regulatory agencies have set limits on the concentration of petroleum hydrocarbons (or total oil and grease) that can remain in pro- duced water destined for ocean disposal The current limit for total oil and grease (dis- persed and dissolved oil, measured by gravimetric or infrared analysis) in treated produced water destined for ocean disposal in U.S Federal waters and state waters of Upper Cook Inlet, AK, is 42 mg/L (ppm) daily maximum and 29 mg/L monthly average (Otto and Arnold, 1996; Veil, 1997) Discharge of produced water to coastal estuarine

2 Bioaccumulation in Marine Organisms

and marine waters is no longer permitted in the United States The permit limits for treated produced water discharges offshore in Australia are 30 mg/L daily average and

50 mg/L instantaneous maximum (Black et al., 1994) The regulatory limit for total oil and grease in produced waters discharged to most offshore waters of the North Sea, the Mediterranean Sea, the Arabian Gulf, and Asia is 40 mg/L (Ray, 1996)

The oil/gas/water mixture may be processed through separation devices to separate the three phases from one another The types of equipment used on platforms in the west- ern Gulf of Mexico to remove oil and grease from produced water include, in order of frequency of use, mechanical and hydraulic gas floatation units, skimmers, coalescers, hydrocyclones, and filters (Otto and Arnold, 1996) Hydrocyclones, because of their operating efficiency and limited space requirements, are being used with increasing fre- quency for oil/water separation on offshore platforms in the Gulf of Mexico, North Sea, Australia, the Middle East, and Southeast Asia (Cornitius, 1988) Chemicals may be added to the process stream to improve the efficiency of oil/gas/water separation Even with the most advanced separation equipment, the oil/water separation is not 100 percent efficient Treated produced water that is discharged to the ocean often contains small amounts of hydrocarbons, other organic chemicals, dissolved salts, and metals

Small amounts of specialty chemicals may be added to the production stream at dif- ferent steps in the production and treatment process to prevent corrosion, foaming, scale formation, hydrogen sulfide formation, and bacterial growth, or to improve the efficiency and completeness of oil/water separation (Hudgins, 1989, 1991, 1992) Most of these chemicals remain in the oil or gas phases; others are water soluble, remain in the produced water, and are discharged with it to the ocean Approximately 19 percent of the offshore production chemicals used on platforms in the North Sea are discharged to the ocean in treated produced water, including more than 50 percent of the emulsifiers, sur- factants, oil removing agents, and scale inhibitors (van Hattum et al., 1992; Ynnesdal and Furuholt, 1994; Hudgins, 1994) Only small amounts (less than 20 percent of the amounts used) of corrosion inhibitors, oxygen scavengers, emulsion breakers, defoamers, and gas treatment agents are discharged with produced water to the ocean

1.1.2 Naturally-Occurring Chemicals in Produced Water

Produced water contains a variety of chemicals that have been dissolved from the geologic formations in which the produced water resided for millions of years (Table 1) These chemicals include inorganic salts (essentially the same salts that are found in sea- water and make the ocean salty), several metals and metalloids, and a wide variety of organic chemicals It should be noted that the concentrations in Table 1 are the extreme ranges for all reported concentrations in produced water Many of the high values, par- ticularly for metals, may be anomalous, caused by matrix interferences from the high concentrations of dissolved salts in most produced waters (Neff, 1987) The highest val- ues are extremely rare and concentrations of most constituents in most produced waters fall in the lower part of the ranges listed in Table 1

Salinity and Inorganic ions The salt concentration (salinity) of produced water may

range from a few parts per thousand (%o) to that of a saturated brine (about 300%o)

they are drinkable However, most produced waters from offshore sources have salinities greater than that of seawater (about 35%o) (Collins, 1975) Most produced waters from

Total benzene, toluene, ethylbenzene, and xylenes (BTEX)

Total polycyclic aromatic hydrocarbons (PAHs)

Total steranes/triterpanes Total phenols Total organic acids Sulfate Arsenic Barium Cadmium Chromium Copper Iron Lead Manganese Mercury Nickel Zinc Total radium (pCi/L)

C o n c e n t r a t i o n R a n g e * _<0.1 - > 1 1 , 0 0 0

1 7 - 3 0 0.068- 578 0.04- 3.0 0.14-0.175

0 6 - 2 3

<0.001 - 1 0 , 0 0 0

<1.0-8,000 0.000004 - 0.32

Stephenson et al (1994), Bakke et al (1996), Trefry et al (1996)

Louisiana coastal waters of the Gulf of Mexico have salinities between 50%0 and 150%0 (Hanor et al., 1986; Louisiana DEQ, 1990) Produced waters from production facilities

in the Central Valley of Califomia, the North Slope of Alaska, coastal Texas, and central Mississippi, U.S.A., have salinities of 18%o to 320%o (Kharaka et al., 1995)

As in seawater, the salinity of produced water is due primarily to dissolved sodium and chloride, with smaller contributions of calcium, magnesium, and potassium (Table 2) However, quite frequently, the ion ratios in produced water are different from those

in modem seawater For example, the ratios of calcium to magnesium in two Indonesian produced waters are 6.3 and 23.5, compared to a Ca/Mg ratio in oceanic seawater of 0.31 (Neff and Foster, 1997) The Ca/Mg ratios in three produced waters from platforms in the southem Caspian Sea range from 8.91 to 9.71 (Samedova et al., 1997)

The concentration of sulfate in produced water is highly variable Most produced waters contain lower concentrations of sulfate than natural seawater does A high sulfate

4 Bioaccumulation in Marine Organisms

is important because it controls the solubility and, thereby, the concentration of several other elements, particularly calcium and barium, in solution in the produced water Produced water in the geologic formation is in the reduced state Therefore, some of the sulfur may be present as elemental sulfur or sulfide Produced water from a crude oil pro- cessing facility in California, U.S.A., contains 48 to 256 mg/L sulfides and 0.6 to 42 mg/L elemental sulfur (WiRer and Jones, 1999)

Sulfides, usually as hydrogen sulfide and polysulfides, may be formed by bacterial reduction of sulfate in anoxic produced water (Large, 1990) They are most abundant in water produced with sour gas or crude oils containing high concentrations of sulfur (WiRer and Jones, 1999) Sulfides are highly corrosive and their generation in the production stream usually is controlled by use of biocides Hydrogen sulfide may also

be formed during storage of produced water samples for later analysis or use in toxicity tests Hydrogen sulfide, because of its high toxicity, may confound the results of toxic- ity tests Hydrogen sulfide concentrations as high as 1,000 mg/L have been detected in produced water (Kochelek and Stone, 1989)

Ammonia is not frequently analyzed in produced water, but when it is, concentrations are highly variable Many produced waters do not contain detectable concentrations of ammonia Among those that do, concentrations may be as high as 650 mg/L (Table 2) Some produced waters from production platforms in the Santa Barbara Channel, California, USA, contain up to 420 mg/L ammonia (Neff, 1997c) Ammonia may be formed by bacterial degradation of organo-nitrogen compounds in the formation or dur- ing storage of produced water Because it is highly toxic to marine organisms, it may, like sulfide, affect the results of produced water toxicity tests performed in the labora- tory It is uncertain, because of their volatility and high aqueous solubility (favoring rapid dilution), if ammonia and sulfide actually contribute to the toxicity to marine organisms

in the receiving water environment of produced water discharged to the ocean By way

of comparison, the four largest municipal wastewater plants in the Los Angeles area dis- charge more than 4 x 1012 liters/day of wastewater containing 23 to 35 mg/L ammonia

to the southern California Bight (Raco-Rands, 1996) The volume of produced water dis- charged to the Santa Barbara Channel is about 1.6 x 107 liters/day (Table 14)

Metals Produced water may contain several metals in solution The metals present and their concentrations in produced waters from different sources are extremely vari- able, depending on the age and geology of the formations from which the oil and gas are produced (Collins, 1975) There is not a good correlation between concentrations of met- als in crude oil and the water produced with it (Olsen et al., 1995; Samedova et al., 1997) Some metals, such as vanadium and nickel, may be very abundant in crude oils but rare in produced water These metals are present as metal-organic complexes (por- phyrins) in the oil and do not partition into the produced water phase in contact with the oil However, some North Sea produced waters contain high concentrations of nickel (Table 3), possibly derived from biodegradation of nickel porphyrins Several metals, including cadmium, lead, and zinc, dissolve into crude oil and produced water as they migrate through mineral ore deposits containing these metals (Olsen et al., 1995; Samedova et al., 1999) Mercury from cinnabar deposits or complexed with the solid organic phase in the hydrocarbon reservoir may "evaporate" into natural gas in the for- mation and condense out of the gas into the produced water when the gas and water are brought to surface temperature and pressure (Battelle, 1994)

Because produced water is thought to be a concentrate of ancient seawater or fresh water, it is not surprising that the metals present in seawater also are present in produced water However, a few metals may be present in produced waters from different sources

at concentrations substantially higher (1,000-fold or more) than their concentrations in

Table 3

Concentration ranges of several metals in produced water from seven platforms in the north- western Gulf of Mexico and 12 discharges to the Norwegian Sector of the North Sea Typical concentrations in seawater are included for comparison Concentrations are/~g/L (ppb)

Metal Seawater G u l f of Mexico North Sea

Produced W a t e r Produced Water

Barium (Ba) 3 - 34 8 1 , 0 0 0 - 342,000 107,000- 228,000 Cadmium (Cd) 0.001 - 0.1 <0.05 - 1.0 0.45 - 1.0

6 Bioaccumulation in Marine Organisms

clean natural seawater The metals most frequently present in produced water at elevated concentrations include barium, cadmium, chromium, copper, iron, lead, nickel, and zinc (Neff et al., 1987) (Table 1) Usually only a few of these metals are present at elevated concentrations in a particular produced water sample For example, Neff et al (1989c, 1992) reported that only barium, lead, and zinc are present at elevated concentrations in produced water from 2 platforms off Louisiana, U.S.A

If water flooding with seawater is used to enhance hydrocarbon production, the metal concentrations in produced water often change gradually over time to more closely resemble the metal concentrations in modem seawater (Stephenson et al., 1994) For most metals this is a decrease in concentration Some chemicals such as barium and radium may precipitate with sulfate if seawater (high in sulfate) is used for water-flood- ing Therefore, although the volume of produced water usually increases with the age of the well, total mass loadings of metals discharged in produced water may not increase; mass loadings of some metals may actually decrease

The highest concentrations of arsenic and barium have been recorded for Gulf of Mexico produced waters, probably because these elements usually are not analyzed in produced water from other sources Barium may be present at high concentrations in produced waters that contain very low concentrations of sulfate (Neff and Sauer, 1995) Water-flooding with seawater may increase the concentration of sulfate (present in sea- water at a concentration of about 900 mg/L) in the formation water, causing barium pre- cipitation as barite, lowering the concentration of barium in the produced water (Stephenson et al., 1994) In the absence of sulfate, barium is soluble in hot, geo- pressured, high ionic strength connate water in the hydrocarbon-beating formation However, some of the barium may be present as minute particles of barite (Olsen et al., 1995) Arsenic concentrations usually are low, but some produced waters contain ele- vated concentrations Produced water from the Funan platform in the Gulf of Thailand contains more than 3 8 0 / ~ g ~ arsenic, more than 65 percent of which is in solution (Frankiewicz et al., 1998) The concentrations of barium, arsenic, and other elements in produced water probably are in equilibrium with elements in the feldspars, plagioclase, biotite, and sandstones in the formation (Bloch and Key, 1981; Macpherson, 1989) Produced water from seven platforms in the northwest Gulf of Mexico, analyzed by modem analytical methods, contain elevated concentrations of barium, iron, manganese, lead, and zinc, and in a few cases arsenic (Table 3) Several samples of produced water from the Norwegian Sector of the North Sea contain elevated concentrations of mercury and nickel Produced water from natural gas platforms in the Gulf of Thailand often con- tains elevated concentrations of mercury (1.4 to 235 ~g/L) (Battelle, 1994; Frankiewicz

et al., 1998) The mercury is from coal and carbonaceous shales in or near the produc- ing reservoirs and is produced as elemental mercury vapor with the natural gas Most of the mercury in the produced water is in particulate forms Unocal Thailand has devel- oped a produced water cleaning process that cleans the produced water to meet proposed environmental standards of <40 mg/L total petroleum hydrocarbons, <10 ktg/L mercury, and <250/~g/L arsenic Generally, produced water from gas wells contains more mer- cury and probably arsenic than produced water from oil wells

Nearly all the iron in produced water is particulate and probably is metallic iron or precipitated iron oxide Naturally biodegraded crude oils often contain a high concen- tration of iron, which may be derived in part from microbial corrosion of steel in the pro- duction tubing and production tank (Olsen et al., 1995) Formation water is anoxic and

some iron may be present at high concentration in solution However, when the forma- tion water is brought to the surface and is exposed to the atmosphere, the iron precipi- tates as iron oxides Manganese behaves like iron; it is soluble in anoxic water but precipitates as various oxyhydroxides in the presence of oxygen Several other metals

in produced water co-precipitate with iron and manganese oxides Zinc and possibly lead could be derived in part from galvanized steel structures in contact with the produced water or with other waste streams that may be treated in the oil/water separator system The Gulf of Mexico produced waters analyzed recently by advanced methods contain

<0.05 to 1.0/tg/L cadmium, similar to concentrations in North Sea produced water (Table 3) Chromium, copper, molybdenum, nickel, and vanadium concentrations usually are low relative to expected concentrations in the environment Some North Sea produced waters contain copper at a concentration about 200 times higher than the con- centration in seawater

Radioisotopes Several naturally occurring radioactive materials (NORM) occur in produced water The most abundant usually are radium-226 and radium-228 (226Ra and 228Ra) The radium is derived from the radioactive decay of uranium and thorium asso- ciated with certain rocks and clays in the hydrocarbon reservoir (Reid, 1983; Kraemer and Reid, 1984; Michel, 1990) 226Ra (half-life 1,601 years) is an a-emitting daughter of uranium-238 and uranium-234; 228Ra (half-life 5.7 years) is a r-emitting daughter of thorium-232 Although the two radium isotopes are from different sources in the geo- logic formation, their concentrations in produced water tend to covary (Fisher, 1995) Concentrations of both 226Ra and 228Ra increase with salinity in oil and gas well pro- duced waters from coastal and offshore waters of Louisiana, U.S.A However, the cor- relation between the salinity and concentrations of 226Ra, 228Ra, and total radium in produced water from some formations is not good; many produced waters of all salini- ties contain little or no radium and some low-salinity produced waters contain signifi- cant amounts of radium

Produced water from 153 oil and gas wells in Texas, U.S.A., contains 0.1 picocurie/L (pCi/L) to 5,150 pCi/L 226Ra, and possibly a similar activity of 228Ra (Fisher, 1995) (1 pCi = 0.037 bequerels [Bq]; 1 Bq = 1 disintegration/sec) A picocurie of 226Ra is equivalent to 1 picogram (pg) of radium; a pCi of 228Ra is equivalent to 0.0037 pg of radium (Santschi and Honeyman, 1989) Concentrations of 226Ra and 228Ra in produced water from platforms along the Louisiana, U.S.A., coast range from below the detection limit to 1,565 pCi/L and 1,509 pCi/L, respectively (Table 4), equivalent to 1.56 ng/L (parts per trillion) and 0.006 ng/L radium, respectively (Kraemer and Reid, 1984; Neff

et al., 1989c) Total radium activities in these produced waters range from less than 0.2 pCi/L to more than 5,000 pCi/L Average concentrations of radium isotopes in pro- duced water from oil and gas wells elsewhere in the world usually are lower than those for produced water from the U.S Gulf of Mexico region (Table 4) By comparison, the concentration of 226Ra and 228Ra in surface waters of the ocean are 0.027 to 0.040 pCi/L and about 0.005 pCi/L, respectively (Santschi and Honeyman, 1989; Nozaki, 1991) Several other radionuclides have been identified in the NORM of produced water,

Activities of these radionuclides are much lower than those of radium For example, off- shore produced waters from the U.S Gulf of Mexico containing 91 to 1,494 pCi/L of 226Ra also contain 5.2 to 16.7 pCi/L of 21~ (Hart et al., 1995)

8 Bioaccumulation in Marine Organisms

Total Organic Carbon The concentration of total organic carbon (TOC) in produced

water ranges from less than 0.1 to as high as 11,000 mg/L (ppm) (Fisher, 1987) and is highly variable from one location to another (Tables 1 and 5) Concentrations of TOC in produced water from the North Sea usually are in the range of 14 to more than 1,000 ppm (Tibbetts et al., 1992; Stephenson et al., 1994); produced water from the Bass Strait, Australia, contains 15 to 313 ppm TOC (Brand et al., 1989) Produced water from pro- duction wells in the U.S Gulf of Mexico contain 68 to 540 ppm TOC (Neff, 1997) Most of this organic matter in treated produced water is in solution or colloidal sus- pension (Means et al., 1989) Therefore, dissolved organic carbon (DOC) concentration

is almost equivalent to TOC concentration Concentrations of DOC vary widely from less than 17 to more than 11,000 mg/L in produced water from different formations and even in produced water from within a particular basin (Fisher, 1987) Highest DOC con- centrations are in produced waters from Pliocene formations Much of the DOC in the

144 samples of produced water analyzed by Fisher (1987) can be accounted for by volatile C 2 through C 5 organic acid anions

Organic Acids As shown in Table 5, much of the TOC in produced water consists of

a mixture of low molecular weight carboxylic acids (fatty acids), such as acetic acid, pro- pionic acid, butyric acid, and valeric acid (Somerville et al., 1987; Means and Hubbard, 1987; Barth, 1991) Volatile organic acids represent 60 to 98 percent of the total extractable organic matter in produced water from three production facilities in the North Sea (Table 6) Most of the remainder of the organic matter in the produced waters is hydrocarbons and phenols Traces of higher molecular weight C 8- through C17-fatty acids also are present

Most of the organic acids in produced water are short-chain aliphatic monocarboxylic acids (Table 7) The most abundant acid usually is acetic acid, and abundance decreases with increasing molecular weight; however, in some coal-associated waters, propionic acid may be most abundant (Fisher, 1987) Dicarboxylic acids may be present at con- centrations usually lower than 100 mg/L; succinic acid and methylsuccinic acid often are most abundant (Lundegard and Kharaka, 1994) Linear and branched C 5- through C 7- fatty acids are present at concentrations of 0.01 to 2 mg/L each in several produced

NA not analyzed ND not detected

Fisher, 1995 Kraemer & Reid, 1984 Hart et al., 1995 Neff, 1997c Neff, 1991a Stephenson et al., 1994 Neff & Foster, 1997 Santschi & Honeyman,

1989

Table 5

Concentrations of total dissolved organic carbon (DOC) and total C2- through C5-organic acids

in produced water from several geologic basins The age of each formation is given

Concentrations of DOC and organic acids are mg/L From Fisher (1987)

Poui Field, Trinidad Pliocene 234 - 3,777 0 - 3,204

S a m a a n Field, Trinidad Pliocene 321 - 4,072 0 - 2,428

T e a k Field, Trinidad Pliocene 425 - 11,314 0 - 2,795

M c A l l e n R a n c h Field, T X O l i g o c e n e 124 - 272 27.4 - 54.6 Las A n i m a s County, CO Tertiary 115 - 378 211 - 595 San Juan County, N M Cretaceous 1,000 - 2,185 1,128 - 1,774

La Plata County, CO Cretaceous 553 - 745 60 - 888

G u n n i s o n County, CO Cretaceous 1 9 0 - 355 2 7 2 - 306

Table 6

Mean concentrations of the main organic fractions in produced water from three offshore production facilities in the Norwegian Sector of the North Sea BTEX (C6-C8 aromatics) are not included Concentrations are mg/L (ppm) From Stremgren et al (1995)

Raton Basin (Coal) 0 - 170 1 9 8 - 425 0 0 211 - 595 San Juan Basin, NM.(Coal) 0 - 30 51 - 1774 0 0 6 0 - 1774 Piciance Basin, CO (Coal) 8 - 75 231 - 297 0 0 272 - 306 Denver Basin, CO 5 - 6 0 0 - 37 0 - 35 0 - 4 2 0 - 72 Red Desert Basin, WY 195 - 434 40 - 208 0 0 403 - 474 Wamsutter Arch, WY 263 - 491 65 - 423 0 0 556 - 686 Washakie Basin, WY 175 - 557 0.2 - 457 0 0 175 - 1014 Western Overthrust, UT & WY 0 - 81 0 - 19 7 - 4 9 0 13 - 110

* C2, Acetate; C3, Propionate; C4, Butyrate; C5, Valerate

10 Bioaccumulation in Marine Organisms

waters from California, U.S.A (Witter and Jones, 1999) Small amounts of aromatic acids (e.g., benzoic acid) also may be present (Means et al., 1989, 1990; Brown et al., 1992) Organic acids are thought to have been produced by hydrous pyrolysis of kero- gen and hydrocarbons in the source rocks and hydrocarbon-bearing formation (Lundegard and Senftle, 1987; Kharaka et al., 1993; Borgund and Barth, 1994)

Phenols Concentrations of total phenols in produced water usually range from 0.6 to

23 mg/L (Table 1) Highest concentrations are in produced water samples from the North Sea (Grahl-Nielsen, 1987; Stephenson et al., 1994) Methylphenols (cresols) and dimethyl-phenols (xylenols) usually are more abundant than phenol in these samples Measured concentrations of total phenols in produced waters from the Louisiana Gulf coast range from 2.16 to 4.51 mg/L (Neff, 1989c; Boesch et al., 1989a,b; Means et al., 1990; Rabalais et al., 1991) The most complete analyses to date of phenols in produced water are those for three Indonesian produced waters (Neff and Foster, 1997) and five North Sea produced waters (Roe Utvik, 1999) These produced waters contain 0.36 to 16.8 m ~ L total phenols (Table 8); phenols with up to five alkyl carbons were detected

sample Polyphenol ethoxylate surfactants, containing octylphenols and nonylphenols, sometimes are used in the production system to facilitate pumping viscous or waxy crude oils If the surfactant degrades, some alkylphenols may get into the produced water Because of the toxicity of the more highly alkylated phenols as estrogen mimics, polyphe- nol ethoxylate surfactants are being replaced in applications where the surfactant or its degradation products may reach the environment in significant amounts (Getliff and James, 1996)

Petroleum Hydrocarbons Petroleum hydrocarbons are the organic components of greatest environmental concern in produced water Hydrocarbons are organic compounds containing only carbon and hydrogen Carbons are linked by single or double covalent bonds to form linear, branched, and cyclic hydrocarbons In aliphatic hydrocarbons, all

Table 8

Concentrations of phenol and different alkylphenol groups in produced water from three production facilities in Indonesia and five production facilities in the Norwegian Sector of the North Sea From Neff and Foster (1997) and Rae Utvik (1999) Concentrations are mg/L (ppm) Chemical Indonesian Produced Water North Sea Produced Water

carbon-carbon covalent bonds are single Aromatic hydrocarbons are composed of six- carbon tings in which the six carbon atoms equally share nine covalent bonds

Petroleum hydrocarbons (measured as oil and grease by infrared spectrometry) account for 25 to 65 percent of the TOC in produced water samples from Cook Inlet (Lysyj, 1982) and 8.5 to 16 percent of the TOC in produced water samples from the Gulf

of Mexico analyzed by Neff et al (1989c) Between 0.6 and 18 percent of the DOC in produced water from a platform on the Northwest Shelf of Australia is petroleum hydro- carbons, measured by GC/FID (Bums and Codi, 1999) C10 through C35 aliphatic and aromatic hydrocarbons account for 0.7 to 40 percent of the total extractable organic mat- ter in three North Sea produced waters (Table 6) It should be pointed out that standard methods required in the U.S for analysis of oil and grease (e.g., EPA gravimetric Methods 413.1 and 1664 and infrared Method 418.1) are not specific for petroleum hydrocarbons and measure several other ingredients in produced water (e.g., some organic acids) in addition to petroleum hydrocarbons (Brown et al., 1992; Otto and Arnold, 1996)

The aqueous solubility of petroleum hydrocarbons decreases as their size (molecular weight) increases (McAuliffe, 1966; Eastcott et al., 1988) Because the oil/water separa- tor equipment is efficient in removing oil droplets but not dissolved oil from the pro- duced water, most of the petroleum hydrocarbons remaining in the produced water after treatment are low molecular weight aromatic and saturated hydrocarbons that are dis- solved in the produced water

Volatile Hydrocarbons The most abundant hydrocarbons in produced water are the one-ring aromatic hydrocarbons, benzene, toluene, ethylbenzene, and xylenes (the BTEX compounds) and low molecular weight saturated hydrocarbons BTEX may be present in produced water from different sources at concentrations ranging from 0.068 mg/L to occasionally as high 600 mg/L (Table 1) In the North Sea, and probably else- where, produced water from gas wells usually contains higher concentrations of BTEX than produced water from oil wells (Stephenson et al., 1994) Benzene often is the most abundant BTEX compound in effectively-treated produced water, followed by toluene (Table 9) Ethylbenzene and the three xylene isomers usually are present at only a small fraction of the concentrations of benzene and toluene A large number of C 3- and C 4- benzene isomers may also be present, usually at low concentrations (Table 9)

Aliphatic Hydrocarbons Saturated (aliphatic) hydrocarbons or alkanes with molec- ular weights in the range of those of BTEX usually are present at much lower concen- trations (usually less than hal0 than those of the monocyclic aromatic hydrocarbons in produced waters (Middleditch, 1981; Sauer, 1981 b; Neff et al., 1989c) For example, two samples of produced water from coastal Louisiana analyzed by Neff et al (1989c) con- tained 1.09 to 2.14 mg/L C 1 through C s alkanes and 2.43 to 9.51 mg/L BTEX This is due in large part to the much greater aqueous solubility of BTEX than of saturated hydrocarbons of similar molecular weight (McAuliffe, 1966)

Normal paraffins from n-C10 to n-C34 are generally much less abundant than BTEX

in produced water (Table 10) Often, the most abundant normal alkane is in the C13 to C16 range and abundance decreases with increasing molecular weight This is due to the volatility of the low molecular weight alkanes and the extremely low aqueous solubility

of alkanes with more than about 16 carbons (Coates et al., 1985) In a typical crude oil,

12 Bioaccumulation in Marine Organisms

Table 9

Concentrations of BTEX and other selected monocyclic aromatic hydrocarbons in produced water from four platforms in the U.S Gulf of Mexico (Offshore Operators Committee, 1997a; Dept of Energy, 1997a) and from three offshore production facilities in Indonesia (Neff and Foster, 1997) Concentrations are pg/L (ppb)

at concentrations higher than their single-phase aqueous solubilities and, therefore, may

be in colloidal form or associated with dispersed oil droplets For example, the solubil- ity of n-alkanes decreases with increasing molecular weight from 52/~g/L for decane (n- C10 ) to less than 6x10 -7/tg/L for tetracosane (n-C24) These solubilities are lower than concentrations of these alkanes in many produced waters (Table 10), indicating that the higher molecular weight alkanes are not in solution in the produced water The particu- late fraction of produced water from a platform on the Northwest Shelf of Australia con- tains 441 to 13,089/tg/L total alkanes, of which 75 to 81 percent is in the unresolved complex mixture (UCM) (Bums and Codi, 1999) The most abundant alkanes contain 12

to 19 carbons The alkane composition of the produced water particles resembles that of the light crude oil produced on the platform, indicating that the particles are oil droplets not removed by the oil/water separator The concentration of dissolved alkanes in the produced water was not measured The oil/water separator system is designed to efficiently remove oil droplets from the produced water; therefore, there is a strong inverse correlation between the efficiency of oil/water separation and the concentration

of n-alkanes in produced water

called polynuclear aromatic hydrocarbons), defined as hydrocarbons containing two or more fused aromatic tings, are the petroleum hydrocarbons of greatest environmental concern in produced water, because of their toxicity and persistence in the marine

Table 10

Concentrations of n-alkanes in produced water from two platforms in coastal Louisiana and two platforms in Thailand Estimated aqueous solubilities of several alkanes are included for comparison Concentrations are/Jg/L (ppb) From Neff et al (1989c) and Battelle (1994) Chemical Aqueous Solubility Louisiana Thailand

Dodecane (n-C12) 3.7 4 4 - 193 3 8 3 - 1,080 Tridecane (n-C13) 1.0 55 - 272 4 5 6 - 1,030

Pentadecane (n-C15) 0.08 5 7 - 266 483 - 830 Hexadecane (I1-C16) 0 0 5 55 177 336 629 Heptadecane (n-C17) 0.006 5 6 - 142 3 6 7 - 705

Nonadecane (!'1-C19) 0.0004 38 - 180 140 - 338 Eicosane (n-C20) 0.0003 3 6 - 171 9 6 - 277

f r o m about 0.04 to 3.0 m g / L (40 to 3 , 0 0 0 / t g / L : ppb) (Table 1) N a p h t h a l e n e (two fused

a r o m a t i c tings) a n d o c c a s i o n a l l y p h e n a n t h r e n e (three fused a r o m a t i c tings) a n d their alkyl

h o m o l o g u e s are the o n l y P A H s that are s o m e t i m e s p r e s e n t at h i g h e r t h a n trace c o n c e n t r a - tions T h e s e l o w m o l e c u l a r w e i g h t P A H s u s u a l l y r e p r e s e n t m o r e t h a n 95 p e r c e n t o f the total P A H s in p r o d u c e d water T h e y often are p r e s e n t at h i g h e r c o n c e n t r a t i o n s in p r o d u c e d

w a t e r f r o m gas w e l l s t h a n in p r o d u c e d w a t e r f r o m oil w e l l s ( S t e p h e n s o n et al., 1994) Individual h i g h e r m o l e c u l a r w e i g h t PAHs, such as the c a r c i n o g e n , b e n z o ( a ) p y r e n e , rarely are p r e s e n t in p r o d u c e d w a t e r at c o n c e n t r a t i o n s greater t h a n a b o u t 0 1 / t g ~ T h e

a q u e o u s solubility o f b e n z o ( a ) p y r e n e is so l o w ( 1 6 / t g / L ) a n d its affinity for the oil p h a s e

so h i g h (log o c t a n o l / w a t e r partition coefficient, log Kow, 6.13) that it w o u l d n o t be e x p e c t e d

to be p r e s e n t in p r o d u c e d w a t e r in a d i s s o l v e d form C r u d e oils r a r e l y c o n t a i n m o r e than about 1 m g / L b e n z o ( a ) p y r e n e (Neff, 1979), so oil droplets w o u l d h a v e to be p r e s e n t at a

c o n c e n t r a t i o n o f m o r e t h a n 1,000 p p m for the p r o d u c e d w a t e r to c o n t a i n 1 ktg/L

14 Bioaccumulation in Marine Organisms

benzo(a)pyrene Mean concentrations of benzo(a)pyrene in produced water from seven offshore platforms in the northwestem Gulf of Mexico are in the range of less than 0.001

to 0.09 ktg/L; North Sea produced water contains 0.009 to 0.4 ktg/L (Table 11) Produced water from four platforms discharging to Bass Strait off the southeast coast of Australia

PAHs (Terrens and Tait, 1993) These concentrations are in the expected range for high molecular weight, poorly soluble PAHs in produced water

Concentrations of individual PAH from naphthalene to chrysene nearly always are in the range of a few tenths to about 300 ktg/L (Table 11), with concentrations decreasing

as molecular weight increases In crude oil, alkyl homologues usually are more abundant than the parent PAHs (Youngblood and Blumer, 1975); however, this often is not so in produced water because of the decreasing aqueous solubility and increasing log Kow with increasing PAH alkylation, favoring retention in the oil phase

Three samples of produced water collected from a platform on the Northwest Shelf

of Australia contained 110 to 1152 ktg/L total PAHs, 6.5 to 11 percent of which was in the dissolved phase (Bums and Codi, 1999) The most abundant PAHs in the dissolved phase are C 1- and C2-naphthalenes The dominant particulate PAHs are C 1- through C 3- naphthalenes and C 2- and C3-phenanthrenes The PAH profile in the oil resembles that

in the particles, indicating that the particles are oil droplets

Other Natural Organic Components of Produced Water There is little informa-

tion about the concentrations of cyclic alkanes (naphthenes) and sulfur-, nitrogen-, and oxygen-substituted hydrocarbons in produced water These chemicals usually are more water-soluble than normal or branched alkanes or unsubstituted hydrocarbons of similar

traces of decalins (decahydro-naphthalenes), dibenzofuran, benzothiophene, and diben- zothiophene (Table 12); several produced waters from the North Sea contain higher con- centrations of decalins (Roe Utvik, 1999) Decalin is a typical cyclic alkane, composed

of two conjugated, saturated six-member carbon rings Benzothiophene and dibenzoth- iophene usually are the most abundant sulfur heterocyclic compounds in produced water Concentrations of dibenzothiophene and total C 1- through C3-dibenzothiophenes in seven samples of produced water from the Gulf of Mexico range from 0.07 to 4.6 ktg/L

centrations in produced water from the North Sea Concentrations of these compounds

in crude oils and the produced waters associated with them usually vary directly with the concentration of sulfur in the oils

A high-sulfur produced water from southern California contains up to 390 ~tg/L 3- thiophenecarboxaldehyde and 2,300 /zg/L benzenemethanethiol (Witter and Jones,

1999) One sample but not six others of the produced water also contains low concen-

trations of a mixture of tetrathianes and pentathiapanes, possibly produced by sulfur- reducing archaea and bacteria in the production system or produced water treatment system

Dibenzofuran is a typical oxygen-substituted heterocyclic compound, and usually is present at low concentrations in produced water (Table 12) Quinoline has been reported (Lundegard and Kharaka, 1994), but there is no information about the presence of other naturally-occurring nitrogen heterocyclics in produced water Some of the lower molec- ular weight N-heterocyclics, such as acridine and carbazole, probably are present in

C h a p t e r 1 - P r o d u c e d Water 15

Table 11

Concentrations of individual PAHs in seven produced waters from the U.S Gulf of Mexico (Dept

of Energy, 1997a; Offshore Operators Committee, 1997), three produced waters from Indonesia (Neff and Foster, 1997), and five produced waters from the North Sea (Ree Utvik, 1999) Concentrations are/Jg/L (ppb)

16 Bioaccumulation in Marine Organisms

Table 12

Concentration ranges of selected cyclic alkanes and heterocyclic compounds in produced water from three production treatment facilities in the Norwegian Sector of the North Sea and in Indonesia Concentrations are pg/L From Neff and Foster (1997) and Ree Utvik (1999)

Several other soluble organic chemicals have been identified in produced water (Lundegard and Kharaka (1994) These include cyclohexanone, serine, glycine, alanine, aspartic acid, and citric acid Barth (1987) identified lactic acid in two samples o f

N o r w e g i a n produced water

1.1.3 Production Chemicals in Produced Water

Large numbers o f specialty additives are available for use in the production system o f

a well to aid in recovery and pumping o f hydrocarbons, protect the production system from corrosion, and facilitate separation o f oil, gas, and water (Table 13) The difference between the mass o f a chemical used and the amount discharged or injected in Table 13

is approximately equivalent to the mass that remains with the produced oil and gas streams M a n y o f these chemicals are more soluble in the oil than in produced water and remain in the oil phase Others are water-soluble and concentrate in the produced water and are disposed o f with it The point in the production stream where the chemical is

Table 13

Amounts of production chemicals used on production platforms in the North Sea and amounts discharged with produced water to the ocean or injected into a well, Masses are metric tons/year From Hudgins (1994)

added influences the amount that may be discharged in the produced water The number

of additives used in a particular production system usually is low, and depends on the particular production problems encountered in the well

Biocides usually are added to the water treatment system for produced water intended for re-injection Biocides may also be used to control sulfide production by anaerobic archaea and bacteria in the production stream Biocides used for this purpose include hypochlorite and glutaraldehyde (Hudgins, 1991) Hypochlorite is destroyed rapidly by reaction with organic matter Gluteraldehyde usually is destroyed by reaction with organic matter in the produced water

Corrosion inhibitors may be water-soluble or oil-soluble Most corrosion inhibitors used on platforms in the North Sea are oil-soluble Only small amounts remain in the treated produced water Corrosion inhibitors are complex mixtures of medium to high molecular weight nitrogen-containing fatty acids, based on rosin acids (from plants) Scale inhibitors are water-soluble and tend to remain in the produced water fraction

of the production stream Scale inhibitors inhibit formation of barium or calcium scale

on the inside of production pipe and usually are nitrogen-containing phosphate esters, such as phosphatidal ethanolamine, or organic phosphonates (Hudgins, 1991)

Large amounts of gas-treating chemicals are used to treat gas production streams and about one-third of the amount used is discharged in the produced water These chemicals

18 Bioaccumulation in Marine Organisms

include methanol, ethylene glycol, and triethylene glycol Methanol and ethylene glycol are used to prevent gas hydrate formation; they remain associated with the water phase Triethylene glycol is used in a closed loop system to dehydrate the gas It is recycled and little enters the produced water stream Di- or tetra-ethylene glycol may be used instead

of triethylene glycol for gas dehydration at some production facilities If the produced gas is sour (contains high concentrations of H2S and CO2), it may be sweetened in a closed loop system containing polyethylene glycol dimethyl ether, which acts as an absorbent for the sour gases Little of the polyethylene glycol gets into the produced water stream and is discharged with it

Produced water represents the largest volume waste stream in production operations

on most offshore platforms (Stephenson, 1991) The amount of produced water dis- charged from a single platform usually is less than 9,400 barrels/day (bbl/d) (1.5 million L/d), whereas discharges from large facilities that process produced water from several platforms may exceed 25 million liters/day (Menzie, 1982) As a general rule, less produced water is produced from gas than from oil wells Current discharge permits for the U.S Gulf of Mexico prohibit discharge of more than 25,000 bbl/d (4 million L/d) of produced water from a single platform

Elsewhere in the world, produced water discharges to the ocean may be larger than those to the U.S Gulf of Mexico In 1992, the Statfjord oil field, the largest offshore field

in the world, discharged an average of 194,000 bbl/d (30.9 million liters/d) of treated produced water to the Norwegian sector of the North Sea (Ynnesdal and Furuholt, 1994) Three production processing platforms off the coast of Indonesia each process oil, gas, and water from several wells and each discharges 120,000 to 610,000 bbl/d (19.1 to 97 million liters/d) of produced water to the west Java Sea (Smith et al., 1996) The three offshore production facilities discharged a combined total of 192 million L/d of pro- duced water to the West Java Sea in 1996 (Table 14) and the discharges were expected

to increase to about 262 million L/d by 1998

The total volume of produced water discharged to US waters of the Gulf of Mexico

in 1991 was approximately 549 million L/d (Rabalais et al., 1991) (Table 14) Most of the water was from platforms in state waters (less than 4.8 km from shore) (MMS, 1995)

In 1991, an average of 438 million L/d of produced water was discharged to the entire North Sea (Stephenson et al., 1994) The average produced water discharge rate to the

Table 14

Volumes of treated produced water discharged in the early and mid 1990s from oil and gas plat- forms to the ocean in different parts of the world Discharge rates are liters/day From Neff (1997a)

Location

U.S Gulf of Mexico

Santa Barbara Channel, California

entire North Sea increased to 512 million L/d in 1993 (R~e et al., 1996) and was esti- mated at 789 million L/d in 1996 (Garland, 1998) Fourteen offshore platforms discharge 159,000 L/d to 3.2 million L/d each of produced water to offshore waters of southern California The total volume of produced water discharge to California waters is about 16.2 million L/d (Neff, 1997c) About 100 million L/d of treated produced water is dis- charged from production platforms and shore-based treatment facilities to Australian waters, most of it from the Gippsland oil and gas field to the Bass Strait (Black et al., 1994) Treated produced water is discharged to the ocean in many other parts of the world, including the Arabian Gulf, South America, the former Soviet Union, and Africa However, information is not available on the volumes of produced water discharged and its chemical and physical characteristics

In most oil and gas fields, relatively little water is produced in the initial phases of production However, the total fraction of production accounted for by produced water often increases as production continues until, in an old, nearly depleted field, production may be as high as 95 percent water and 5 percent fossil fuels (Read, 1978) Over the eco- nomic life of a producing field, the volume of produced water may exceed the volume

of fossil fuel produced by a factor of as much as ten (Stephenson, 1991) Most of the oil and gas fields in the western Gulf of Mexico, the North Sea, and the Bass Strait of Australia are mature or declining; produced water production is increasing as fossil fuel production decreases (Brendahaug et al., 1993; Black et al., 1994; MMS, 1995)

1.3 FATE OF CHEMICALS FROM PRODUCED WATER IN THE OCEAN

1.3.1 M o d e l e d Dilution of the P r o d u c e d Water P l u m e

Saline produced waters dilute rapidly upon discharge to well-mixed marine waters Dispersion modeling studies of the fate of produced water differ in specific details but all predict a rapid initial dilution of discharges by 30- to 100-fold within the first few tens

of meters of the outfall, followed by a slower rate of dilution at greater distances (Smith, 1993; Terrens and Tait, 1993; Stromgren et al., 1995; Brandsma and Smith, 1996) When discharge volumes of buoyant or neutral-density produced water are very high, dilution may be slower Factors that affect the rate of dilution of produced water following dis- charge to the ocean include discharge rate, ambient current speed, turbulent mixing regime, water column stratification, water depth, and difference in density (as deter- mined by temperature and total dissolved solids concentration) and chemical composi- tion between the produced water and ambient seawater

Terrens and Tait (1993) used the Offshore Operators Committee (OOC) model to pre- dict the fate of produced water discharged from Platform Halibut to Bass Strait off south- eastern Australia At the time of the modeling, the produced water discharge rate from Platform Halibut was 14 million L/d and the median ambient current speed was 26 cm/sec (Table 15) The produced water had a salinity similar to that of ambient seawater and a temperature, at discharge, of 90~ the produced water plume was buoyant Under these conditions, the produced water was diluted nearly 30-fold within 10 m of the dis- charge (at about the point where the buoyant plume reached the sea surface) and by 1,800-fold 1,000 m down-current of the produced water discharge At 100 m down- current from the discharge site, the maximum concentration of produced water in the plume was 0.45 percent (Table 15) The temperature of the plume dropped to within I~

20 Bioaccumulation in Marine Organisms

Table 15

Modeled dilutions of produced waters discharged to different offshore waters under different oceanographic regimes The OOC model was used in all simulations From Terrens and Tait (1993) and Brandsma and Smith (1996)

Brandsma and Smith (1996) also reported results of modeling of a North Sea dis- charge The modeled discharge of 9,992,000 L/d of slightly buoyant produced water

These simulations using the OOC model show the effects of discharge rate and current speed on the rate of dilution of the produced water plume There is an inverse relation- ship between discharge rate and current speed on one hand and dilution rate on the other Modeling studies of high-volume discharges of warm high-salinity produced water to the North Sea yielded predicted dilutions of about 500-fold within about 60 m of the out- fall under well-mixed water column conditions; under conditions of a stratified water column, a predicted 300-fold dilution was reached 60 m from the discharge (Stephenson

et al., 1994) Further dilution was slower; a 1,000-fold dilution was attained after about

1 hour when the produced water plume had drifted about 1,000 m

Pertimina/Maxus operates 63 platforms in the West Java Sea north of the Sunda Strait

in Indonesian waters (Smith et al., 1996a,b; Smith and Tyler, 1997) Produced water is treated to remove dispersed hydrocarbons and discharged to the ocean through six sub- sea outfalls on three offshore production facilities (Widuri, Krisna, and Cinta) Cinta has two produced water discharges, Widuri has three, and Krisna has one The current total

volume of treated produced water discharged from the three offshore facilities is approx- imately 192 million L/d (Smith and Tyler, 1997)

The produced water from the three facilities has a low salinity, ranging from 10 to 18 %o, suggesting that the produced water is derived from ancient fresh water Discharge tem-

produced waters from the three production facilities are buoyant in the ambient seawa- ter The outfalls are located at 3 to 15 m below the sea surface However, the buoyant plumes from the three facilities come to the surface within 10 m down-current of the out- falls (Smith et al., 1996b) This usually is under the platforms The multiple produced water discharges from a platform (either Cinta or Widuri) tend to merge before or immediately upon reaching the sea surface Thus, the discharges from a given platform can be modeled as a single discharge

The dilution and potential biological effects of the produced water plumes from the three facilities have been modeled with the BMT PISCES model (Maxus Southeast Sumatra, Inc., 1995; Tyler et al., 1997) Initial dilution (dilution occurring between the time the produced water leaves the outfall and reaches the sea surface) was modeled under different seasonal environmental conditions for each platform using the CORMIX model Two seasonal monsoons, the southeast monsoon and the northwest monsoon, interspersed with short transitional periods, control net surface water current flows These net flows are superimposed on diurnal tidal flows The complex current regime causes the produced water plume to wander in different directions from the platforms on daily and seasonal scales Plume dilution is slowed during periods of slack surface cur- rents and increases during maximum surface flows that may exceed 2 km/h This current regime results in pooling of the produced water plume during periods of slack currents; areas of higher produced water concentration are interspersed with zones of lower produced water concentrations The BMT model predicted that the produced water concentration in a typical pool in the produced water plume from the Widuri facility is 3.3 percent (the pools in the Widuri plume are interspersed by water predicted to contain about 0.17 percent produced water)

The initial dilution of the produced water following discharge to the ocean is differ- ent for each of the three facilities because of differences in produced water discharge rates, temperatures, salinities, and discharge pipe diameter The initial dilution also varies seasonally because of shifts in surface current speed and direction Initial dilutions

of the effluents from the three platforms vary from 12- to 120-fold The initial dilutions are inversely related to produced water discharge rate and directly related to surface water current speed

Because of its great buoyancy, the plume spreads as a thin layer 1 to 2 m thick on the sea surface, with little vertical or lateral dispersion There appears to be limited vertical and lateral mixing of the produced water plume with ambient seawater As a result, the produced water is diluted slowly, particularly in pools A produced water pool more than

6 km down-current from the high-volume discharge from the Widuri facility may still contain 3 percent produced water, representing a 30-fold dilution, according to the model (Smith et al., 1996b)

In most marine environments, current speeds and directions are not constant (Terrens and Tait, 1993; Brandsma and Smith, 1996) Superimposed on a net or residual current direction are tidal currents that form current ellipses that recur according to the local tidal regime Tidal current speeds vary from near zero at the neap tide to maximum values

22 Bioaccumulation in Marine Organisms

during the middle of ebb and flow tides Thus, the produced water is discharged into a sur- face current regime that is continuously varying in speed and direction The diluting plume may follow an elliptical path, returning to near the discharge point, while being advected gradually in the direction of net current flow Superimposed on these flows are wind-driven surface currents that may alter direction and speed of the surface water cur- rents Under these conditions, the concentration of the produced water plume at any loca- tion around the discharge site is highly variable over time and space Modeled dispersion

of produced water plumes in the West Java Sea (Smith et al., 1996), Bass Strait (Terrens and Tait, 1996), and Northwest Shelf of Australia (King and McAllister, 1998), and the North Sea (Rye et al., 1999) shows a complex distribution of concentrations of plume constituents around the discharge due to the continuously changing water current field Attached and mobile marine organisms in the vicinity of the discharge are being exposed

to constantly changing produced water concentrations The daily discharge of 11.6 mil- lion L/d of treated produced water in the vicinity of the Ekofisk facility in the North Sea

is diluted on a regional scale by about 100,000-fold (Rye et al., 1999)

1.3.2 Fate of Chemicals in Produced Water Plumes

Field measurements of produced water dilution are highly variable but confirm the predictions of modeling studies, that dilution usually is rapid Continental Shelf Associates (1993) reported that radium-226 from a 1.07 million L/d produced water dis- charge in a water depth of 18 m in the Gulf of Mexico was diluted by a factor of 426 at

5 m from the discharge, and by a factor of 1,065 at 50 m from the discharge The current

fication of the water column The OOC but not the CORMIX model accurately predicted the dilutions measured in the field Produced waters from the Gulf of Mexico contain high concentrations of dissolved barium It is probable that the radium in the produced water co-precipitated rapidly with barium sulfate in the sulfate-rich receiving waters Smith et al (1994) used a dye tracer to measure dilution of produced water being dis- charged at rates of 460,000 L/d to 1.03 million L/d in a water depth of 82 m The produced water had a salinity of 85 %o and a temperature of 32~ Ambient water sam- ples collected from the dye plume showed that the produced water was diluted 100-fold within 10 m of the discharge and by 1,000-fold within 103 m of the discharge The field observations were in good agreement with predictions of the OOC produced water dis- persion model The rhodamine dye probably acts like a conservative component of the produced water over the time periods of the dye study That is, its concentration is affected by dilution, but the dye is not lost from the plume by evaporation, precipitation,

or degradation

Somerville et al.(1987) also used rhodamine dye to validate modeled dilutions of neu- trally buoyant produced water discharge from the Fulmar A platform in the British North Sea They measured a 100-fold dilution of the dye at 50 m down-current from the dis- charge and a 2,800-fold dilution 1,000 m down-current from the discharge Rabalais et

al (1992) were able to measure elevated (compared to background) concentrations of radium, but not volatile hydrocarbons, to about 1,000 m down-current of a high-volume produced water discharge to shallow coastal waters of Louisiana

The most abundant hydrocarbons of environmental concem in produced water usu- ally are the light, one-ring aromatic hydrocarbons (the BTEX compounds) Because they

C h a p t e r 1 - P r o d u c e d W a t e r 23

are very volatile, they evaporate rapidly from the water following produced water dis- charge Brooks et al (1980) reported that the maximum concentration of benzene meas- ured in seawater immediately below the above-water produced water discharge pipe at a production platform in the Buccaneer Field off Galveston, Texas, U.S.A., was 0.065

~g/L This represents a nearly 150,000-fold dilution of the concentration of benzene in the produced water effluent (9,500/zg/L) Concentrations of total gaseous and volatile hydrocarbons, including BTEX aromatics (75 percent of the total) decreased from 22,000/tg/L in the effluent, to 65/tg/L at the air/water interface below the outfall, to less than 2/tg/L in the surface water about 50 m away, indicating very rapid evaporation and dilution of the volatile components of the produced water

Terrens and Tate (1996) measured concentrations of BTEX and several PAHs in ambient seawater 20 m from an 11 million L/d produced water discharge from a plat- form in the Bass Strait off southeastern Australia There was an inverse relationship between molecular weight (and volatility) and the dilution of individual aromatic hydro- carbons Individual monocyclic aromatic hydrocarbons were diluted by 53,000-fold (benzene) to 12,000-fold (xylenes) PAHs were diluted by 12,000-fold (naphthalene) to 2,000-fold (pyrene) Concentrations of higher molecular weight PAHs were below the detection limit (0.0002/tg/L) in the ambient seawater 20 m from the outfall The inverse relationship between molecular weight of the aromatic hydrocarbons and their rates of

produced water, favoring evaporation of the lighter aromatic hydrocarbons

King and McAllister (1998) modeled and measured concentrations of benzene and toluene in the produced water plume from an oil production platform in approximately

24 m of water on the northwest shelf of Australia The MUDMAP model (Spaulding et al., 1994) was used for the modeling exercise Midwater currents were wind-driven with

a strong diurnal tidal component Maximum current speeds were 90 cm/sec and decreased to near zero during the slack tide

The platform has two treated produced water discharges, a high-volume discharge from the hydrocyclones, averaging 7.155 million L/d, and an overflow discharge via a gas floatation unit that ranges from 0 to 1.279 million L/d The high-volume hydrocy- clone discharge is located 4 rn above mean sea level, so the slightly buoyant produced

surface

Under these conditions, the MUDMAP model predicts that the initial dilution of benzene and toluene in the hyrocyclone discharge, following the jet phase, is about 2,000-fold Actual measured initial dilutions are 100- to 200-fold The free-fall of the produced water to the sea surface allows the plume to spread on the water surface with- out the high-energy jet phase of turbulent mixing Because of the variable speed and direction of tidal currents at the discharge site, benzene and toluene concentrations in the surface plume vary with distance from the discharge Pools of higher concentrations occur in the advecting plume, caused during slack tides when the produced water is being discharged into a static water mass Predicted concentrations of benzene in the pools are as high as 23/tg/L The measured concentrations of benzene in the pools are

as high as 13/tg/L, in reasonable agreement with the modeled concentrations The measured concentration represents a 300- to 550-fold dilution of the benzene and toluene concentrations in the produced water Benzene and toluene concentrations in the undiluted effluent are 4,013 to 7,208/tg/L and 4,036 to 6,154/tg/L, respectively