the treatment of contaminated water at remedial wood preserving sites

The Treatment of Contaminated Water at Remedial wood Preserving Sites

Doaglas lic! Grosse Edward R. Bates Endalkachew Sable-Demessie

Douglas M? Grosse has worked as an environmental engineer at the US. Environmental Protection Agency (EPA) in Cincinnati, Ohio, f o r the past 21 years. Current@, he is working in Technology Transfer by serving as a specialist in site remediation and industrial wastewater treatment. Edward R Bates has been with the US. EPA in Cincinnati, Ohio, as aphysical scientist since 1977. Since 1989 his principal duties have been to provide expert technical assistance on all aspects of Superfund site remediation, including characterization, remedy selection, remedy design, and field implementation. Endalkachew Sahle- Demessie is a research engineer at the U S . EPA, National Risk Manage- ment Research Labora- tory, Cincinnati, Ohio. He has been working on the application of emerging treatment technologies for remediating contaminated soils.

Contaminated groundwater and surface water have posed a great chal- lenge in restoring wood presemlirzg sites to beneficial use. Often contaminated grounduuter plumes extend far beyond the legal proper@ limits, adversely impacting drinking water supplies and crop lands. To contain, treat, and/or rmzediate these valuable resources is an impomrzt part of restoring these impacted sites. Various options are amailable for remediating thegroundwater and other affected media at these sites. Frequent@, pump and treat technologies have been used that can provide well-head treatment at installed extmction ulells. This approach has shown to be costly and excessive4y time consuming. Some of the technologies used foi*pump and treat are granular activated carbon (GAC), biotreatment, and chemical oxidation. Other approaches use in-situ treatment applications that in- cl ude enhanced hioremedia tion, mon it0 red natz c rat a tten 2 iation (biotic and abiotic), and chemical reductiori/fixation. Ultimately, it may only be feasible, econoinically or practicably, to use hydraulic containment systems. Depending upon site-specific conditions, these treatment approaches cat? be used in various combinations to offer the best remedial action. A comparison of watertreatmeizts2stem costs extrapolated from the treatability studiespe$ormed on contaminated groundwater from the McCormicW Baxter SupeTjund site in Stockton, California, yielded operation and maintenance costs of $1.19/1,000 gal. for carbon treatment and $7.53/ 1, OOOgal., for ultraviolet (Wlperoxidation, respectivety. 02000 John Wile y & Sons, Inc.

Citation of product, company, or trade names do not constitute endorsement by the US. Environmental Protection Agency and are provided only for the purpose of better describing information in this article. Opinions expressed are those of the authors and should not be construed as representing positions or policy of the US. Environmental Protection Agency.

0 2000 John Wiley & Sons, Inc. 111

DOUGLAS W. GROSSE EDWARD R BATES ENDALKACHEW SAHLE-DEMESSIE

Hydraulic containment can best be described as a control technology that incorporates both physical and hydraulic systems to immobilize, destroy, andlor remove contaminants in the saturated zone of a contaminated site.

INTRODUCTION This article presents several treatment approaches for contaminated

water at wood preserving sites that have been evaluated at the U.S. Environmental Protection Agency (US EPA) National Risk Management Research Laboratory (NRMRL). Both field demonstration projects and vendor treatability studies were conducted in the NRMRL remedial technical assistance program, in order to gain a better understanding of the respective technology applications. This discussion will primarily focus on hydraulic containment, carbon adsorption, photochemical oxidation, and bioremediation.

HYDRAULIC CONTAINMENT Hydraulic containment can best be described as a control technology

that incorporates both physical and hydraulic systems to immobilize, destroy, and/or remove contaminants in the saturated zone of a contanii- nated site. Contaminated groundwater plumes often have a tendency to extend beyond source areds) into the surrounding environment, contami- nating drinking water sources and impairing surface water ecosystems. The goal of using hydraulic containment is to restrict contaminant mobility through physical and hydraulic controls. Physical controls can be achieved by using one or more of the following: slurry walls, cutoff walls, permeable reactive barriers (PRBs), buried drain lines, collection sumps, delivery systems, infiltration galleries, and geomembranes. Hydraulic control involves the use of extraction and injection wells, usually in conjunction with pump and treat systems.

A major advantage of using a hydraulic containment technology is that it can be installed fairly quickly in the event that mobile contaminants pose an imminent threat to drinking water sources. More complex systems, such as vertical barriers and PRBs, require more design and constniction effort. Another key advantage is that the design requirements and construction techniques are well established. Technology limitations include (1 1 periodic monitoring and maintenance, (2) vertical barriers that are susceptible to physical/cheniical attack, and (3) actual performance that is difficult to assess.

Case Study Hydraulic containment was implemented in 1986 at the former railroad

tie treating operations near Laramie, Wyoming (lJS EPA, 1997). Creosote was the primary wood treating reagent used at the site and responsible for most of the contamination discovered at the site. Contamination of soil and groundwater occurred as a result of reagent spillage, discharge of wastewater to low-lying areas, and contaminant release from surface impoundments at the site. Characterization data generated from the remedial investigation (RI) revealed widespread contamination of creosote, pentachlorophenol (PCP), and carrier oil, which formed a dense nonaqueous phase liquid (DNAPL) pool at a depth of 10 feet at the base of a highly permeable alluvial deposit. It was estimated that the alluvial deposit was contaminated by approximately 6.5 million gallons of DNAPL

112 REMEDIATION/SUMMER 2000

THE TREATMENT OF CONTAMINATED WATER AT REMEDIAL WOOD PRESERVING SITES

Although costs for implementing these specific abatement measures are not available for the Laramie, Wyoming, project, costs for implementing hydraulic containment can vary greatly depending upon site-specific factors and construction techniques.

at an average depth of 10 feet over an area of 90 acres. Due to potential risks of human exposure and the environment, it was deemed necessary to implement inmediate atmtement measures to prevent the proliferation of contamination. Initially, a dike was built running adjacent to the impacted Laramie River for the purpose of restricting floods. Thereafter, a short section of sheet-pile was installed to cut off the suspected subsurface flow of oil from the site into the nearby Laraniie River (US EPA, 1997).

More permanent solutions to mitigate off-site contamination were evaluated. A contaminant isolation system (CIS) was developed to prevent further migration of contaminants. This system consisted of (1) a 10,000 linear-foot, soil bentonite cutoff wall; (2) 17,000 linear feet of horizontal drain line providing inward groundwater flow to the site; and (3) a pump- and-treat system utilizing oil/water separation followed by filtration and activated carbon. Results have indicated that the CIS successfully stopped the seepage of oil into the Laramie River. Contaminated alluvial groundwater was intercepted and treated before discharge to the river. Contami- nated water fi-om other sources was being extracted and treated in the CIS water treatment plant. Conclusions based upon field-site monitoring data are that the ininiinent risks associated with the contaminant migration and environmental impairment have been greatly reduced.

Although costs for implementing these specific abatement measures are not available for the Laramie, Wyoming, project, costs for iniplement- ing hydraulic containment can vaiy greatly depending upon site-specific factors and construction techniques. For example, depth of confining layers, soil type, contaminant mobility, and groundwater pH are irnpor- tant site-specific factors. Materials of construction, emplacement approaches, and maintenance requirements also impact project costs. Generally, the deeper the emplacement of hydraulic containment sys- tenis into the subsurface (greater than 50 feet) the more expensive the remediation cost. Typically, costs range (in 1992 dollars) from $3 to $75 per square foot o f installation.

WATER TREATMENT The next three technology evaluations were conducted as treatability

studies performed on contaminated groundwater samples collected at the McCorniick/Baxter (MCB) Superfund site in Stockton, California. (USEPA, 199%). Creosote and PCP were the primary wood treating reagents used at the site and responsible for most of the contamination discovered at the site. One of the primary treatment objectives was to meet the criteria for discharge to the publicly owned treatment works (POTW) of the city of Stockton. Criteria for discharge were established as the maximum contaminant levels (MCLs) for drinking water as published in 40 CFR 141(US EPA). Three of the contaminants of concern found in the MCB groundwater were benzo(a)pyrene (BAP), PCP, and 2,3,7,8-tetrachlorodibenzo-p-dioxin (2,3,7,8-TCDD ). The established MCLs for these contaminants are listed in Exhibit 1.

For two of these contaminants, BAP and 2,3,7,8-TCDD, equivalency factors were developed that account for overall toxicity values. For

~ ~~ ~ ~

REMEDIATION/~UMMER 2000 113

DOUGLAS W. GROSSE EDWARD R. BATES. ENDALKACHEW SAHLE-DEMESSIE

Benzo(a)pyrene (BAP) Pentachlorophenol (PCP) TCDD-TEQ

Exhibit 1. Maximum Contaminant Levels (MCLs) for MCB Groundwater Contaminants

0.02pg/L(ppb) 1 .Opg/L(ppb) 30 pg/L(ppq)”

I contaminant 1 MCL”

example, BAP equiualents were established for seven PAH compounds (US EPA, 1993). Similarly, for 2,.?,7,8-TCDD toxicity equiualencLy fuctors (TCDD-TEF) were determined for the relative and additive toxicity of the eleven isomers of polychlorinated dibenzo-p-dioxins and dibenzofurans. Thereby, the concentrations of individual constituents and corresponding toxicity factors are presented together. The three technologies evaluated under the treatability study assistance program for contaminated water were carbon adsorption, ultraviolet (UV) cavitation, and UV peroxidation.

CARBON ADSORPTION Carbon adsorption has commonly been used to remove organic

contaminants from water via sorption of the contaminants onto active carbon sites. This sorption phenomenon occurs as the result of one of two characteristic properties for any given solvent-solute-solid system (Weber, 1972). The primary driving force for adsorption occurs as a result of the lyophobic (solvent disliking) character of the solute relative to a particular solvent or of the high affinity of the solute for the solid. For most applications in water or groundwater treatment, adsorption results from the combined action of these two forces. There are a number of factors that determine the effectiveness of the adsorption process, including (1) the surface area and pore size of the carbon media, (2) the solubility and molecular size of the organic contaminants, and (3) the contact time. In general, organics of low solubility, low vapor pressure, and high molecular weight are the most readily adsorbed, allowing for optimum adsorption to occur on the carbon surface. Likewise, granular activated carbon (GAC) is used most frequently due to the large number of active sites available per unit weight. The contaminants adsorb to the surfaces of the microporous carbon granules until all the active sites are occupied. Ultimately, the GAC will need to be regenerated and/or replaced.

114 REMEDIATION/SUMMER 2 0 0 0


A treatability study was conducted by a vendor interested in generating performance data on the GAC treatment of a groundwater contaminated with PAHs, PCP, and dioxin compounds. This study utilized a scaled-down version of a conventional GAC system in order to accelerate the adsorption cycle (Exhibit 2). One significant advantage of using this modified system is that only a few days of treatment are required in order to predict convaminaiit breakthrough. Therefore, there is less chance for the sample stream to degrade via biological activity in the column system. This configuration will actually simulate large-scale system performance by providing dynamic data versus equilibrium capacity data generated by an isotherm. Consequently, effects of flow on adsorption capacity can be predicted.

Experimental Design and System Operation A 5 gallon (19 L) sample of groundwater obtained from the MCB site

was shipped to the GAC vendor for treatability testing. After the water was filtered through a 1.0 m glass-fiber filter to remove residual solids, it was fed into the accelerated carbon treatment (ACT) system containing a high- activity pulverized GAC. The amount of carbon used in the ACT study was 25 percent of the design amount. The ACT column system was designed to simulate a groundwater flow rate of 80 gallons per minute (gpm) and was operated for seven days. Two 1-liter samples of treated water were composited each day until the feed groundwater sample was depleted. Samples of the treated groundwater were screened for the presence of

Exhibit 2. Carbon Treatment Accelerated Column Test Schematic

Teflon or Neoprine 1/16 Stainless Steel Tubinq

Liquid resevoir t Treated Water

Effluent

REMEDIATION/SUMMER 2000 115


Constituent

Pentachlorophenol

Phenol

2-Methylphenol

PAHs using field test kits (US EPA, 1998a). After screening the results of the test kits, samples were selected for laboratory analysis for semivolatiles and dioxins/furans.

Influent Day-1 Day-2

7,400 3,900 11,000

38 <10 27

94 4 0 74

Performance Some of the more significant results obtained for the contaminants of

concern, semivolatile organic compounds (SVOCs) and dioxins/furans (TCDD-TEQ), are presented in Exhibit 3. Concentrations for the seven PAH compounds used in calculating BAP potency estimates were not detected and consequently not presented Although the data indicate that PCP increased in concentration throughout the test study, this may be attributed to breakthrough of the compound within the first day. The Day 1 sample analysis showed a decrease in concentration by approximately 47 percent. Vendor extrapolated carbon usage data indicated that the PCP treatment objective would be maintained for the Day 1 ACT simulated conditions of 35.7 operating days with treatment of 4.198 million gallons of water and a carbon use rate of 1.19 pounds per 1,000 gallons. Other results indicated that TCDD-TEQ decreased by 53 percent. The phenol data, overall, showed a slight decrease with the exception of 2,4,5- and 2,4,6-trichlorophenol. However, it can be noted that these values are well within reasonable sample variability. Nevertheless,

4-Methylphenol

2,4,5-Trichlorophenol

Exhibit 3. Results From the ACT Treatability Study McCormick/Baxter (USEPA, 1998a)

30 <lo 29

45 <50 <50

I I 1

I 2,4,6-Trichlorophenol I 1J I <10 I <10 I 1 TCDD-TEQ(pg/L)' 1 51.2 1 21.2 I 25.7 1

1 Day-6 i 8,000

30 I

-1 24.1

I TCDD-TEQ by 1-TEFs/89 @PA, 1989a).

J = estiinated value.



The development and application of photochemical oxidation technologies have gained a lot of attention in recent years as a result of research and development in both the private sector and regulatory agencies.

carbon dose and breakthrough time need to be calculated before this technology is considered for use in removing specific contaminants at contaminated sites.

cost Based upon an operating system containing 20,000 lhs of 8x30 mesh

virgin activated carbon with a flow rate of 80 gpm, and a capital cost divided evenly over ten years (420,480,000 gallons of treated water), a treatment cost was calculated to be approximately $1.38 per 1,000 gallons of water treated. This is broken down into capital ($0.17/1,000 gal.) and operations and niaintenance (O&M) ($1.19/1,000 gal.) cost. The cost estimate does not include site preparation, utility, permitting, and disposal of residuals for meeting regulatory compliance (US EPA, 1997).

PHOTOCHEMICAL OXIDATION The development and application of photochemical oxidation tech-

nologies have gained a lot of attention in recent years as a result of research and development in both the private sector and regulatory agencies. These technologies are useful in the treatment of a wide range of pollutants found in groundwater, wastewater, and drinking water. Photochemical systems offer some distinct advantages over more conventional technologies such as air stripping and carbon adsorption. One significant advantage is that the target coinpounds are either completely destroyed o r converted to relatively innocuous compounds eliminating the need for further treatment or excessive residuals management (US EPA, 177%). Recent studies have shown that photochemical oxidation can effectively destroy a wide variety of contaminants including dioxins (US EPA, 1778b). Of particular interest is the use of IJV (photooxidation), in conjunction with a catalyst (photocatalysis 1 o r with a chemical reagent (photochemical oxidation) to enhance the degradation of hazardous organic compounds present at low parts per million (ppm) concentrations in contaminated water. Powerful oxidants or hydroxyl radicals are generated in the presence of UV and chemical reagents such as hydrogen peroxide (H,O,), - - Fentons Reagent, and ozone, or catalysts such as titanium dioxide. Photooxida- tion technologies can destroy water contaminants without the addition of chemical re:igents.

Conventional separation technologies separate and transfer the contaminants from one phase to another, however, some photocatalytic processes are known to effectively mineralize certain contaminants such as cyanide, chlorinated aliphatics, and complex aromatic compounds, in reaction times on the order of a few minutes to several hours. This is not to suggest, though, that all constituents are mineralized via photochemical oxidation. Optimization of the process is focused on manipulating process conditions to affect the fastest rate of destruction of the target contaminants. Several key process variables used to optimize photochemical oxidation Iiiay include pH adjustment, pretreatment for the removal of suspended solids, the use of catalysts and W light sources.



Two treatability studies were performed that evaluated two different types of photochemical oxidation systems. These two processes were supplied by vendors. Each vendor treated the same Contaminated groundwater samples obtained from the MCB Superfund site in Stockton, California. The first vendor utilized H,02, hydrodynamic cavitation and W to oxidize the organic compounds present in the contaminated groundwater. The other vendor utilized UV photolysis in conjunction with H,O,, that is referred to as W peroxidation.

Vendor 1: Experimental Design and System Operation The purpose of the first treatability study was to evaluate the

effectiveness of eliminating PCP, PCDDdPCDFs, and PAHs in groundwater by using hydrodynamic cavitation coupled with UV peroxidation (US EPA, 1994). Cavitation occurs when a liquid undergoes dynamic pressure reduction while the temperature is held constant. The desired end products are water, carbon dioxide, and halides. The treatment objective for this study was to meet the criteria for discharge to the City of Stockton, P O W . Approximately 475 gal. of the MCB groundwater was collected for treatment. This sample was a composite taken from two extraction wells, representative of the variation of contamination found at the site. A skid mounted treatment system was transported to the site and set up in the field with utility connections. The system contained two W reactors each housing low-pressure mercury vapor lamps, a low-energy reactor (1.2 kilowatts) and a high-energy reactor (10 kilowatts). During the study, the system was operated as a continuous flow, with the flow rate held constant at 1 gpm for test runs that used W photolysis. Additional runs tested cavitation and reagent dosing without UV photolysis. Process variables included lamp intensity, irradiation time, and H,O, dosage.

Cavitation occurs when a liquid undergoes dynamic pressure reduction

is held constant. the temperature

Performance The results of the field treatability study are shown in Exhibit 4. The

data indicate that UV alone was marginally effective in degrading PAHs and PCP. For example, the lowest percent removal for PAHs (both total and BAP potency estimate) were at 31 percent and 51 percent, respectively, when no H202 was used in the test run. In fact, none of the treated samples met the treatment objectives for the measured contaminants or the calculated toxicity equivalent factors (US EPA, 1993). The optimum dosage of H,02 needs to be determined where higher additions may result in poorer performance. Higher than optimal concentration of H ,O, may scavenge the hydroxyl radicals compromising the treatment effectiveness of the system. The PCP concentrations present in the raw groundwater samples were reduced by 58 percent and 99 percent following photooxidation and photochemical treatment, respectively. With only one sample result recorded for each of the three test conditions, sample variability may have adversely skewed the results of the test runs. Furthermore, system performance may have been compromised by a noticeable turbidity in the groundwater samples. Filtration of the contaminated water was not included in the vendor treatability study protocol nor used during the test.



Influent

Exhibit 4. Performance Data from Photochemical Oxidation Cavitation Treatment (USEPA, 1998a)

Condition 1” Condition 2h Condition 3

Constituent Conc.

4,300

86

Total PAHs

Conc. 010 Conc. 010 Conc. 010

3,000 -31 8,500 +99 6,500 +51

42 -51 <lo8 NC <90 NC B(a)P Potency

370

11,000

365

2.2 x lo’

Dibenzofuran, yg/L

PCP, yg/L

Phenol, yg/L

300 -19 250 -32 170 -54

4,600 -58 1405 -99 1,200 -89

38 +6 29J -19 19J -47

NR NC 4.8 x 104 +118 2.8 x 10” +27 TCDD-TEQ, pg/L

.I Condition 1 - 0 mg/L (ppm) H20,, 1.2 kW W lamp, flow rate 1 gpm, treatment time 10 min. ” Condition 2 - 80 mg/L (ppm) H,O,, 30 kW W lamp, flow rate 1 gpm, treatment time 8 min.

L Condition 3 - 100 mg/L (ppm) H,O,, 10 kW W lamp, flow rate 1 gpm, treatment time 8 min.

I Percent change is stated as a decrease (-> or increase (+’).

J - estimated value.

NC - not calculated. NR - not reported.

Vendor 2 In the second treatability study, the UV peroxidation vendor supplied

a carbon prefilteration step to remove benzo(a)pyrene from the untreated groundwater. As shown in Exhibit 5, the untreated water was passed through a 5 ym prefilter and mixed with a photocatalyst suspension consisting of ferrous sulfate and H,O, before being fed to the reactor. The UV peroxidation system design was optimized for PCP destruction.

Experimental Design and System Operation A 20 gal. sample of contaminated groundwater was obtained from the

MCB site and shipped to the vendor (2) for treatability study testing. A total of nine different tests were performed on the sample to evaluate the effects of initial pH, catalyst addition (ferrous sulfate), UV lamp type, pretreatment, and H,O, dosage. For each of the test runs, samples were collected at different

- I


DOUGLAS W. GROSSE EDWARD R. BATES ENDALKACHEW SAHLE-DEMESSIE

Exhibit 5. UV Peroxidation Treatment System

- Catalyst Unt raa led n

Water t Influent

T I

1-

5 : m ' Prefilter (optional) Pump

Static Mixer

Circulation

Pump Circulation

Pump

Cooling Water In

Cooling Water Out - ~ q ::::anger , uv Ti Cooling Water In '

u P l t

nger UV Meter

I - 3

Reactor ..I ... I..- I....... -.-.-..-

Drain Power SUP PiY

time intervals to evaluate the effects of treatment time in the process reactor. UV dosage was dependent upon the UV lamp type and treatment time.

Performance Based on results obtained from the analysis of 21 samples collected

from nine individual test runs (Exhibit 6), the recommended treatment scheme for destroying PCP utilizing a prefilter consists of using an SX UV- type lamp (2 kW/gal.) along with a H,O, dosage of 100 mg/l for a retention time of 2 minutes. Without the prefilter, optimum performance was obtained by using an SX UV-type lamp (2 kW/gal.) along with an H,O, dosage of 200 mg/l for a retention time of 2 minutes. Percent reductions for PCP were 77.5 and 78.2, respectively.

120 REMEDIATION/SUMMER 2 0 0 0

THE TREATMENT OF CONTAMINATED WATER AT REMEDX WOOD PRESERVING SITES

Test No

1

2

3

4

5'

6'

7'

8

7l

Exhibit 6. PCP Treatment Performance for MCR Water Treated by Vendor 2 (USEPA, 1998a)

Retention Peroxicle Initial pH W (hW/gal) PCP (-g/L) Time (mm 1 (nig/L)

0 200 7 5 2 7500

0 5 2700

2 0 120

0 5 200 . t 5 2 2900

2 0 980

0 200 4 5 2 7600

0 5 760

2 0 570

0 5 200 7 5 4 1300

1 0 51

0 5 200 7 5 2 2900

2 0 40

0 100 7 5 2 8000

0 5 2100

2 0 38

0 5 100 5 0 2 2400

2 0 180

0 5 300 7 5 5 5 300

1 0 39

0 5 200 7 5 5 5 130

1 0 7 ~ ~

I Prefilter 5 p .

REMEDIATION/~UMMER 2000 121


Carbon Treatment

It is important to note that based upon these treatability study results, process parameters need to be closely monitored and optimized for each treatment application. Site-specific matrix effects (e.g., turbidity, pH, interferences, etc.) will vary from one substrate to another.

Dual-vessel system containing 20,000 lb. of 8 x 30 mesh GAC Carbon use rate = 1.19 lb./1,000 gal

cost There was no cost data provided by the vendor for the cavitation

system. Although the carbon treatment study yielded lower capital and 0&M costs, this treatment approach merely transfers contaminants from one phase to another. It also requires close monitoring to avoid breakthrough formation. Exhibit 7 shows a comparison of water treatment system costs extrapolated from the MCB treatability studies, including costs for both carbon treatment and photochemical oxidation.

UV Peroxidation APO"

BIOREMEDIATION Bioremediation is another treatment approach that has gained accep-

tance in treating contaminated soils, sludge, and sediments from wood

(1) UV type SX H,O, = 300 mg/l Catalyst'' 270-kW lamp power

Exhibit 7. Comparison of McCormick/Baxter Water Treatment System Design and Cost

Vendor Optimized Treatment System

(2) UV type SX H 0 = 300 mg/l No catalyst 360-kW lamp power

2 2

cost

Capital($) I O&M $/1,000 gal

312,195 7.53'

385,000 8.08

A Advanced photochemical oxidation (APO) was designed. exclusively, for PCP destruction

'' Ferrous sulfate.

Based on $O.Ob/kWh and 10% of capital expense per year.

122 REMEDIATION/~UMMER 2 0 0 0


treating sites, as well as Contaminated groundwater, surface water, and runoff. Bioremediation can be performed in several different modes: monitored natural attenuation, enhanced in-situ bioremediation of aquifers, and ex-situ biotreatment of extracted and/or collected contaminated water. This article will neither discuss natural attenuation nor in-situ bioremediation due to their special applicability and status. Rather, this discussion will focus on two treatability studies detailing the ex-situ biotreatment of contaminated groundwater collected from two Superfund sites.

Treatability Study on American Creosote Works (ACW) Groundwater For a groundwater sample collected at the ACW Superfund site near

Jackson, Tennessee, chemical oxidation was used to augment bioremediation (US EPA, 1998a). Contaminants of concern included PAHs, PCDDs/PCDFs, PCP, along with other phenolic compounds. These contaminants were apparently spread via drippings, spillage, and leaks from process vessels and holding tanks. A groundwater sample consisting of an oil/water emulsion was prepared by mixing groundwater extracted from 5 foot deep pits.

Experimental Design Fenton’s Reagent (hydrogen peroxide and ferrous sulfate) was selected

as the augment formulation for this treatability study. This reagent will generate hydroxyl radicals in solution which will oxidize organic compounds to carbon dioxide (CO,), water (H,O), and simple organic acids. The experimental design for this study prescribed setting up five discrete test conditions, as shown in Exhibit 8.

For each treatment condition and controls, a slurry was prepared using 50 mL of the ACW water sample, 25 g of sterile soil, and 25 mL of sterile deionized water. The initial total organic carbon (TOC) concentration of the water sample was measured to be 227 mg/L. Nutrient amendment was applied to each treatment by adding 0.04 g of a proprietary blend of

Exhibit 8. Experiniental Design for Bioremediation Treatability Study on ACW Groundwater (USEPA, 1998a)

Treatment Condition Description

Conventional Biological

Fenton’s Reagent

Slurry in nutrient media

Slurry in nutrient media plus 10 niillimolar (mM) conc. of ferrous ions and 0.5 Molar (M) conc. of H,O,

Slurry in nutrient media plus 10mM conc. of chelated ferric iron and 0.5 M conc. of H,O, .’

Slurry in deionized water and 0.1 (0.4g) percent mercuric chloride (HgCl,)

Slurry in deionized water

- - Fenton’s Reagent with Chelated Ferric Iron

Abiotic Control

Biotic Control

“ Chelated ferric iron was added as a ferric iron/EDTA complex in solution.



nutrients which included 5 percent ammonium chloride, 20 percent disodiuni phosphate, 12.5 percent monosodium phosphate, and 12.5 percent sodium tripolyphosphate. Nutrient was not added to either the abiotic or biotic controls. Four test conditions including the biotic control were placed on a shaker set at 120 revolutions per minute (rpms) and incubated at 2 5 "C. The abiotic control was placed in a refrigerator set at 4 "C to retard biological activity. The abiotic sample was used to provide information that would address the issue of matrix and chemically induced treatment effects. Samples were analyzed for PCDDs/PCDFs during an initial characterization of untreated water. Semivolatile organic compound (SVOC) and total petroleum hydrocarbon (TPH) analyses were conducted on the pretreatment sample in order to establish a baseline concentration for these parameters. Four replicates of the first three treatment conditions were collected over four sampling events after 5, 10, 15, and 30 days to allow for TPH analysis. One replicate would be sacrificed at each of the four time points for this purpose. All treatment conditions, including the controls, were analyzed for PAHs, PCP, and PCDDs/PCDFs at the end of the study (day 30). However, abiotic and biotic controls were sampled, exclusively, for TPH at the end of the study.

Performance The results for the treatability study are presented in Exhibit 9.

Biotreatment without Fenton's Reagent reduced total PAH concentrations by 96 percent and BAP potency estimates by 95 percent. However, PCP concentrations were reduced by only 38 percent. The least favorable performance was provided with the Fenton's Reagent. The total PAHs, BAP potency, and PCP were only reduced by 82, >59, and 33 percent, respectively.

Exhibit 9. Biotreatnient of Contaminated Water from ACW witlidwithout Augmentation (USEPA, 1978a)

Influent

Constituent' Conc.

Total PAHs 726,000 B(a)P Potency 10,600

PCP 77,625 Phenol 63 1

Dibenzofuran 58,219

'-Methylphenol 582 +Methylphenol 1,019 2,4-Dimethylphenol 1,455 TCDD-TEQ NR

Biologkd

Conc. 0/02

27,000 -96 560 -95

2,700 -95 48,000 -38

530 -16 58 -90

<330 >67 <330 >77

3,125,600 NC

Fenton's Reagent

Conc. %*

130,000 -82 <4,300 > -59 12,000 -79 52,000 -33 <3,200 NC <330 > -43 440 -57

<3,200 NC 3,883,000 NC

Fenton's + Ferric Iron

Conc. %2

54,000 <690 4,700 12,000 <330 <330 <330 <330

3,508,000

-93 > -93 -92 -85

> -48 > -43 > -67 > -77 NC

I All Vd lUeS are expressed in pg/L (ppbs) with the exception of TCDD-TEQ which is expressed in pg/L (ppq),

NC=Not calculated NR=Not recorcled

Percent change is stated ns a decrease (-) or increase (+).



Fenton's Reagent will be lethal to microbes and reduce microbial degradation. When Fenton's Reagent was amended with ferric chloride the percent removal for total PAH and BAP potency was 93 percent and >93 percent, respectively. Futhermore, PCP was reduced by 85 percent, which offered the most favorable result obtained from the three test conditions. One possible explanation for this improved treatment performance is that the augmented ferric ion concentration can generate more hydroxyl radicals as the Fenton's Reagent is consumed by the oil/water matrix.

Treatability Study at the MacGillis and Gibbs Superfund Site Another treatability study was also conducted at the MacGillis and

Gibbs (MGG) Superfund site in Minneapolis, Minnesota (US EPA, 1991). Both the MacGillis and Gibbs Company facilities had been used for wood preserving activities for several decades. A section of the MGG property, where disposal activities had routinely taken place, collected water and formed a pond. In reviewing the Remedial Investigation/Feasibility Study (RI/FS), it was concluded that the soil and groundwater at this location were contaminated with PCP and lesser amounts of PAHs.

Experimental Design A 30 gal., packed-bed reactor was used during the nine month pilot-plant

study. The system was inoculated with an indigenous microflora followed with additional inoculations of a Flavobactem'zrm acclimated to PCP. The unit operated on a continuous mode for the remainder of the study. Air was continuously injected into the treatment unit to maintain aerobic conditions. In addition, pH was adjusted and nutrients added, as deemed necessary.

Exhibit 10. Selected Results from the MacGillis and Gibhs Packed-Bed Reactor Treatability Study (USEPA, 1991) Parameter" Influent Effluent 010 Change

Anthracene Benzo( alpyrene" Fluoranthene Naphthalene Phenanthrene Pyrene Total PAHs R(a)P Potency Pentachloropheno

252 211 466

1,932 264 232

12,200 603

I 1 93,000

20 5

153 81 38 15 520 40 ND

-92 -98 -67 -96 -86 -94 -96 -93

- -100'

I' Expressed in pg/L (ppbs). I' Used with other constituents in the calculation of B(a)l' potency estimate.

ND = Not detected. Detection limit not presented for this compound. Yi change is considered to approach 100.



Exhibit 11. Estimated Costs for MacGillis and Gibbs Site Case Study (USEPA, 1991)

Unit Type and Category 5 gpm Mobile

Cost Category $/ 1,000 gal % Capital Equipment 11.11 76 Labor 1.49 10

Consumables: caustic 0.24 2 Electricity 0.216 1 Heat 1.46 10 Total ($/1,000 gal) 14.56 100

Consumables: nutrient 0.042 0.31

5 gpm Stationary 30 gpm Stationary

$/ 1,000 gal % 1.16 25 1.49 32 0.042 1 0.24 5 0.216 5 1.46 32 4.61 100

$/ 1,000 gal 0.51 0.50 0.017 0.24

1.46 2.94

0.216

YO 17 17 1 8 7

50 100

Performance The results of this study are presented in Exhibit 10. The packed-bed

reactor was reported to have effectively removed PCP, PAHs, and other targeted constituents. The specific rate of PCP degradation was as high as 70 mg of PCP/L of reactor volume/hr. All PCP analyses were carried out using an HPLC method. Extensive removal of PAHs (96 percent) was also achieved. While substantial reductions in chemical oxygen demand (COD) occurred, the levels in the effluent indicated the presence of refractory material.

cost Estimated costs for the MGG site are presented in Exhibit 11 ( US EPA,

1991). These cost estimates do not include costs associated with site preparation, permitting and regulatory activities, start-up, effluent treatment and disposal, residuals management, analytical services, maintenance/modification, and demobilization.

CONCLUSION We have shown through various treatability studies that there are

many technologies for treating contaminated groundwater at wood preserving sites. Biological treatment is relatively inexpensive and has shown to be effective in reducing higher molecular PAHs. Furthermore, photochemical oxidation has shown to be effective in transforming most of the organic compounds over a wide range of concentration. Research- ers and users of these technologies are finding that no single technology application can be effective for all sites or contaminants.

REFERENCES Weber, W.J. (1972). Physicochemical processes for water quality control. New York: John Wiley & Sons, Inc.

US Environmental Protection Agency. (1989, March). Interim procedures for estimating risks associated with exposures to mixtures of chlorinated dibenzo-p-dioxins and dibenzofurans (CDDs and CDFs) and 1989 update (EPA/625/3-89/016).

126 REMEDIATION/SUMMER 20 0 0


US Environniental Protection Agency. (1991, September). Superfund record of decision, MacGillis and Gibbs/Bell Lumber and Pole Co. (EPA/ROD/R05-91/170).

US Environmental Protection Agency. (1993, July). Provisional guidance for quantitative risk assessment of polycyclic aromatic hydrocarbons (EPA/bOO/R-93/089).

US Environmental Protection Agency. (1994, May). CAV-OX Cavitation Oxidation Process Magnum Water Technology, Inc. EPA applications analysis report (EPA/540/AR-93/520).

US Environmental Protection Agency. (1997, October). Treatment technology performance and cost data for rrinediation of wood preserving sites (EPA/625/R-97/009). Cincinnati, Ohio: Center for Environmental Research Information, National Risk Management Research Laboratory, USEPA.

US Environmental Protection Agency. (1998a, February). Treatability studies for wood preserving sites. ;I compilation of treatability studies performed under contract by IT Corporation (CN 68-CL-0108) and SAIC (CN 68-C5-0001) (EPA 600/R-98/0260). NTIS PB98- 132400.

US Environmental Protection Agency. (199813, December). Advanced photochemical oxidation processes (EPA/625/R-98/004). Cincinnati, Ohio: Center for Environmental Research Information, National Risk Management Research Laboratory, USEPA.


the treatment of contaminated water at remedial wood preserving sites

Documents