Assessment and Remediation of Contaminated Sediments (ARCS) Program

Monitoring Links

Prepared by
Evelyn Meagher-Hartzell and Clyde Dial
Science Applications International Corporation
Cincinnati, Ohio

for the
Assessment and Remediation of Contaminated Sediments (ARCS) Program
Great Lakes National Program Office
U.S. Environmental Protection Agency
Chicago, Illinois

The information in this document has been funded wholly or in part by the U.S. Environmental Protection Agency (EPA) under Contract No. 68-C8-0062, Work Assignment No. 3-52, to Science Applications International Corporation (SAIC). It has been subjected to the Agency's peer and administrative review and it has been approved for publication as an EPA document.

Bench-Scale Evaluation of Sediment Treatment Technologies

US Environmental Protection Agency. 1994. Abstract and Table of Contents to "Bench-Scale Evaluation of Sediment Treatment Technologies Summary Report." EPA 905-R94-011. Chicago, Ill.: Great Lakes National Program Office (GLNPO).

ACKNOWLEDGEMENTS

This report was prepared by the Engineering/Technology Work Group (ETWG) as part of the Assessment and Remediation of Contaminated Sediments (ARCS) program. Dr. Stephen Yaksich, U.S. Army Corps of Engineers (USACE) Buffalo District, was chairman of the Engineering/Technology Work Group.

The ARCS Program was managed by the U.S. Environmental Protection Agency (USEPA), Great Lakes National Program Office (GLNPO). Mr. David Cowgill and Dr. Marc Tuchman of GLNPO were the ARCS program managers. Mr. Dennis Timberlake of the USEPA Risk Reduction Engineering Laboratory was the technical project manager for this project. Mr. Stephen Garbaciak of USACE Chicago District and GLNPO was the project coordinator.

This report was drafted through Contract No. 68-C8-0062, Work Assignment No. 3-52, to Science Applications International Corporation (SAIC). Evelyn Meagher-Hartzell and Clyde Dial of SAIC were the principal authors of the report, with final editing and revisions made by Mr. Garbaciak prior to publication.

This report should be cited as follows:

U.S. Environmental Protection Agency. 1994. "Bench-Scale Evaluation of Sediment Treatment Technologies Summary Report," EPA 905-R94-011, Great Lakes National Program Office, Chicago, IL.

ABSTRACT

The Great Lakes National Program Office (GLNPO) leads efforts to carry out the provisions of Section 118 of the Clean Water Act (CWA) and to fulfill U.S. obligations under the Great Lakes Water Quality Agreement (GLWQA) with Canada. Under Section 118(c)(3) of the CWA, GLNPO was responsible for undertaking a 5-year study and demonstration program for the remediation of contaminated sediments. GLNPO initiated the Assessment and Remediation of Contaminated Sediments (ARCS) Program to carry out this responsibility. In order to develop a knowledge base from which informed decisions may be made, demonstrations of sediment treatment technologies were conducted as part of the ARCS Program. A series of bench-scale studies using SoilTech's Anaerobic Thermal Process Technology, Resources Conservation Company's B.E.S.T.^reg. Solvent Extraction Process, ReTeC's Thermal Desorption Technology, and Zimpro's Wet Air Oxidation Process are the subject of this report. The specific objectives for this effort were to determine process destruction or extraction efficiencies for polychlorinated biphenyls (PCBs) and polynuclear aromatic hydrocarbons (PAHs); to conduct a mass balance for solids, water, oil, PCBs and PAHs; and to examine process effects on metals, oil and grease, and several other parameters.

The SoilTech ATP^reg. technology was tested using sediment samples obtained from the Buffalo and Grand Calumet Rivers. The concentration of the contaminants of concern in the sediments were 0.34 and 10.7 mg/kg PCBs respectively and 8.7 and 235 mg/kg PAHs respectively. The PCB removal from the Grand Calumet River was 72 percent. Because of the very low concentration of PCBs in the Buffalo River sediment it was not possible to make an effective assessment of the PCB removal. The PAH removal from both sediments was 99 percent.

The B.E.S.T.^reg. Solvent Extraction Process was tested using sediment samples obtained from the Buffalo River, Saginaw River, and Grand Calumet River. The concentration of the contaminants of concern in the sediments were 0.3 to 22 mg/kg PCBs and 3 to 220 mg/kg PAHs. PCB and PAH concentrations of 0.2 to 0.4 and 0.4 to 37 mg/kg, respectively, were found in the treated solids. This corresponds to PCB and PAH removals of >95 to 99 percent and 65 to 96 percent, respectively.

The ReTeC Holo-Flite^(TM) Screw Processor was tested using a sediment sample obtained from the Ashtabula River. The concentrations of the contaminants of concern in the sediment were 14.6 mg/kg PCBs and 6.1 mg/kg PAHs. PCB and PAH concentrations of <0.6 and <2.4 mg/kg, respectively, were found in the treated solids. This corresponds to PCB and PAH removals of >96 and >60 percent, respectively.

The Zimpro Wet Air Oxidation Process was tested using a sediment obtained from the Grand Calumet River. The concentrations of the contaminants of concern in the sediment were 11.9 mg/kg PCBs and 266 mg/kg PAHs. PCB and PAH concentrations of 8.5 and <2.84 mg/kg, respectively, were found in the treated solids. This corresponds to PCB and PAH removals of 29 percent and >98.9 percent, respectively.

Table Of Content

Foreword
Acknowledgements
Abstract
Figures
Tables

1.0 Introduction
1.1 Background
1.2 Purpose and Scope
1.3 Approach

2.0 Experimental Design
2.1 Description of the Phased Approach
2.2 Characterization of the Various Sediments and Residuals
2.3 Sampling and Analysis

3.0 Results and Discussion
3.1 Summary of Phase I Results
3.2 Summary Phase II Results
3.3 Quality Assurance/Quality Control
3.4 Individual Technology Report References

Appendix - Data Verification Report for the ARCS Program

1.0 INTRODUCTION

1.1 Background

In order to develop a knowledge base from which informed decisions may be made, bench-and pilot-scale demonstrations were conducted as part of the ARCS Program. Information from remedial activities supervised by the U.S. Army Corps of Engineers and the Superfund program was also utilized. The Engineering/Technology (ET) Work Group was charged with overseeing the development and application of the bench-scale and pilot-scale tests.

For purposes of the technology evaluations conducted under the ARCS Program, the term "bench-scale" refers to laboratory-based tests that utilize glassware simulations of the central reactions of a particular process. Bench-scale tests are typically conducted on several kilograms or less of material. The term "pilot-scale" refers to a field-based demonstration utilizing a scaled-down version of a treatment technology that more closely represents the physical and operational characteristics of a full size processor. Under the ARCS Program, bench-scale tests were conducted on different treatment technologies in order to demonstrate if the fundamental chemical or physical reactions could be successfully applied to contaminated sediments from the Great Lakes, and to identify technologies that were feasible for demonstration at the pilot scale.

Science Applications International Corporation (SAIC) was contracted to provide technical support to the ET Work Group. As part of this effort, SAIC performed seven treatability studies on sediments obtained from four locations in and around the Great Lakes to evaluate the ability of the technologies to remove organic contaminants, specifically polychlorinated biphenyls (PCBs) and polynuclear aromatic hydrocarbons (PAHs). PCB and PAH process extraction or destruction efficiencies; mass balance closures for solids, water, oil, PCBs, and PAHs; and changes in the concentration of metals, oil and grease, and several other parameters were evaluated.

1.2 Purpose and Scope

SAIC and its subcontractors conducted seven treatability tests for the ARCS Program on four different sediments using four treatment technologies: Low Temperature Thermal Desorption Process (Remediation Technologies, Inc. (ReTeC)), Anaerobic Thermal Process (ATP^reg.) Technology (SoilTech), Wet Air Oxidation (Zimpro Passavant), and the Basic Extractive Sludge Treatment (B.E.S.T.^reg.) Solvent Extraction Process, (Resource Conservation Company (RCC)). The four sediments used during the treatability studies were obtained from the Ashtabula River, Buffalo River, Grand Calumet River, and Saginaw River. The contaminants found in these four sediment samples are commonly encountered in contaminated sediments throughout the Great Lakes, as well as in other areas of the United States and Canada. These contaminants include oil and grease, heavy metals, pesticides, PCBs and PAHs. The four sediment samples represented a wide range of contaminant concentrations, as shown in Table 1.

The purpose of this study was to evaluate the feasibility, cost, and effectiveness of various technologies for treating and removing organic contaminants (PCBs and PAHs) from the designated sediments. The effects of the technologies on other parameters, including oil and grease, heavy metals and cyanide, were assessed. The specific objectives of the study were as follows:

To record observations and data to predict a technology's full-scale performance
To take samples during the tests and conduct analyses sufficient to allow for calculation of mass balances for oil, water, solids, and other compounds of interest
To calculate the destruction or removal efficiencies of target compounds
To obtain treated solids (300 g dry basis), water, and oil for independent analysis

This report summarizes the approach used and results obtained during bench-scale (laboratory-based) testing of the different technologies. According to the various vendors, the results obtained during testing mirror results achievable during full-scale (field-based) operations and thus an accurate estimate of the performance associated with a full-scale application of each technology is possible. Since none of these technologies have been implemented on a full scale with these sediments, this correlation between laboratory and field operations is unproven. Also, since this study is only one part of a much larger program and is not intended to evaluate the treatment of the sediments completely, data interpretations are limited to comparisons of technology performance between the four technologies studied. Material balances estimating mass distributions were performed when possible. This report presents a summary of the various technology tests conducted by SAIC for the ARCS Program. Detailed reports on each individual technology are available from GLNPO upon request. Section 3.4 provides the detailed references for the technology-specific reports.

1.3 Approach

1.3.1 Site Names and Locations for Each Sediment Sample
GLNPO collected sediments for study from the following areas around the Great Lakes: Ashtabula River, Ohio; Buffalo River, New York; Grand Calumet River/Indiana Harbor Canal, Indiana; Saginaw River, Michigan; and Sheboygan River, Wisconsin. SAIC was contracted to treat sediments from the Grand Calumet River, Buffalo River, Ashtabula River, and Saginaw River using four technologies: RCC's B.E.S.T.^reg. Solvent Extraction Technology, Zimpro's Wet Air Oxidation Process, Soil Tech's ATP^reg. Technology and ReTeC's Low Temperature Thermal Desorption Process. A map provided in Figure 1 shows the ARCS Priority Areas of Concern. Specifics of the sample location for the Buffalo River, Saginaw River, Grand Calumet River and Ashtabula River are shown in Figures 2, 3, 4 and 5, respectively.

1.3.2 Sediment Acquisition and Homogenization
Prior to conducting the treatability study using each technology, the sediment was homogenized and stored under refrigeration by the U.S. EPA Environmental Research Laboratory in Duluth, Minnesota. Samples of the homogenized sediments were sent to SAIC by the Duluth laboratory. Sediments were then transferred by SAIC to the appropriate technology vendor. The technology vendors performed a series of standard tests on these sediments (Phase I) to determine if the sediments they were scheduled to treat were compatible with their processes and to determine optimum testing conditions and procedures for the treatability study (Phase II). Additional sediment was later forwarded to the vendors by SAIC for the Phase II testing.

1.3.3 Sediment Characterization
SAIC was responsible for the physical and chemical characterization of the raw sediments used during the tests. Under SAIC's direction, the sediment and residuals were analyzed by Battelle Marine Sciences Laboratory in Sequim, WA. Table 1 provides characterization data pertaining to the four sediments.

1.3.4 Technology Descriptions

1.3.4.1 ReTeC's Low Temperature Thermal Desorption Technology
The ReTeC Low Temperature Thermal Desorption Technology separates the contaminants present in a solid matrix through volatilization. This technology can be used independently or as part of a multi-stage treatment train. Volatilized contaminants are subsequently condensed to yield an oily liquid which can then be further treated through an incineration or other destructive process.
The Holo-Flite(TM) Screw Processor is the primary component of the ReTeC Thermal Desorption Technology. The Holo-Flite(TM) Screw Processor is an indirect heat exchanger used to heat, cool, or dry bulk solids/slurries. It consists of a jacketed trough housing a double-screw mechanism. Heated fluid continuously circulates through the hollow flights of the screw augers to elevate the temperature of the soils. This fluid travels the length of the screws and returns to the heater through the center of each shaft. The rotation of the screws promotes the movement of the material forward through the processor.
Volatilized organics are removed from the treatment chamber by means of an induced draft fan and routed to an off-gas control system. The atmosphere in the treatment chamber is controlled during treatment to ensure that oxidation of the volatilized materials does not occur. A three-stage approach is used to control these off-gases. Initially, gas-entrained particulate matter is collected using a series of cyclones. The volatilized moisture and organics are then removed using a water-cooled condenser. The remaining non-condensible gas is then passed through a canister containing activated carbon for VOC control.
A process flow diagram of the 1000 pound-per-hour (460 kilogram-per-hour) thermal desorption system which was used for Phase II testing is provided in Figure 6. ReTeC conducted Phase II testing at processing conditions [temperature (525deg.C), screw rotation rate (0.75 rpm), and residence time (75 min.)] determined following Phase I. Approximately 225 kg of Ashtabula River sediment were used during the single Phase II run. Because a significant amount of the feed would have been lost by utilizing the bucket elevator (i.e., relative to the total amount of material being processed), the sediment was hand-fed into the unit.
To prevent liquids present in the sediment from passing though the system with less than optimal retention times, decanted sediment solids were initially fed into the unit to produce a "dam" effect in the screw processor. During actual operation, dry sand may be used to create the dam effect in the screw processor. This will keep more liquid feeds from flowing too quickly through the screw conveyor. After the first three and a half pails of solids were added to the unit, operators began introducing water with each scoop of solids fed into the unit. All the water associated with the original sediment was fed through the unit. Approximately 80 kg of dry treated solids were generated.
1.3.4.2 RCC's B.E.S.T.^reg. Solvent Extraction Process
The B.E.S.T.^reg. Solvent Extraction Process employs triethylamine (a solvent) to extract organic contaminants from contaminated media. Triethylamine is an aliphatic amine produced by the reaction of ethyl alcohol and ammonia. When employed, a single-phase, homogenous extraction solution containing triethylamine, water, and oil is produced. Any organic contaminants present in the feed material are solvated in the water and oil portion of the extraction solution. A flow diagram for the B.E.S.T.^reg. process is shown in Figure 7.
Because triethylamine is inversely miscible (i.e., at temperatures below 18deg.C, triethylamine is completely miscible with water, while at temperatures above 18deg.C, triethylamine is only partially miscible with water) and can simultaneously solvate oil and water, triethylamine can be used to treat wastes containing both contaminated oils and water.
Since triethylamine is soluble in water at temperatures below 18deg.C, the first extraction is conducted near 4deg.C. The extract obtained from this reaction will contain most of the water present in the feed material. Since the solubility of oil in triethylamine increases at temperatures above 54deg.C, subsequent extractions conducted at these temperatures enhance the removal of oil from the contaminated solids. The extracts from these later reactions contain mostly oil and very little water.
The extracts generated undergo additional treatment to separate them into oil, water, and triethylamine. If sufficient water is present in the extract generated during the initial "cold" extraction, the solution can be separated into two phases, a triethylamine/oil phase and a water phase, by heating the liquid to a temperature above the miscibility limit (54deg.C). The triethylamine/oil phase is combined with the extract produced from the subsequent extractions.
In a full-scale unit, the triethylamine is recovered from the triethylamine/oil phase by steam stripping and is recycled directly to the extraction vessels for the solvent recovery portion of the process. Residual triethylamine in the water and oil products is usually low. Triethylamine remaining in the treated solids may be removed by indirect heating with steam. Typically, residual triethylamine within the treated solids biodegrades readily. Since the full-scale unit operates in a closed loop with one small vent for removal of non-condensing gases, air emissions are minimal. However, RCC typically uses a water scrubber and activated carbon on this vent to minimize triethylamine releases.
Phase II procedures and associated equipment used are described in the following paragraphs. With slight variations, the same procedure was used to treat each of the sediments.
During the treatability tests of the different sediments, each sample was placed in a 4-L resin kettle immersed in a temperature-controlled water bath set at 1deg.C. Each sample's pH was adjusted using sodium hydroxide (NaOH) and 2.7 L of chilled triethylamine (2 percent H2O). While immersed in the cooling bath, the sample was mixed with the NaOH and the chilled triethylamine using a air-driven prop mixer. At the end of the first mixing stage, the sample was allowed to separate by gravity. The particulates were then separated from the liquid by centrifuging the extract at 2,100 rpm for 10 minutes. The solvent/oil/water/centrate were set aside for later decantation. The solids from the centrifuge were placed back into the resin kettle for additional wash stages.
For the second extraction, the samples were heated to 53 to 60deg.C. The mixture was kept heated while mixing was in progress. Mixing was conducted with a pneumatic mixer for approximately 20 minutes. The solvent/oil was poured off and held for later combination with the solvent/oil portion from the decantation procedure. For the third wash, the same procedure that was used in the second wash was repeated. Mixing for this wash was for 30 minutes.
The treated solids resulting from the third wash were then dried at 104deg.C in a forced-draft oven. To ensure that the triethylamine residual in the dried solids was low, the solids were treated with caustic soda (applied with the de-ionized water) when the pH of these solids was less than 10. Sufficient caustic soda was added to raise the pH to approximately 10.5.
The first stage extracts trap nearly all of the water present in the feed sample. Because of this, only the water from the first stage extracts is recovered. After recording the water's pH, which should have been >10, and its volume, the water was stripped by steam at 110deg.C in a Buchi Rotovapor apparatus to ensure that the triethylamine left the water. The elevated pH is necessary to ensure that the majority of the triethylamine remains in the volatile molecular form. The bulk of triethylamine was removed by boiling the triethylamine/oil mixture at 110deg.C in the Rotovapor (no steam necessary). The triethylamine condensed as it evaporated and was collected separately.
1.3.4.3 Zimpro's Wet Air Oxidation
Zimpro's Wet Air Oxidation Process employs elevated temperatures and pressures to oxidize inorganic and organic contaminants under aqueous conditions. Compressed air or pure oxygen generally serve as the oxidizing agent in the wet air oxidation process. Temperatures ranging from 175 to 320deg.C are usually employed. System pressures of 2.0 MPa or greater are common. A flow diagram for the Zimpro wet air oxidation process is shown in Figure 8.
In processing an aqueous waste, the waste stream containing the oxidizable material is first pumped to the system using a positive displacement, high pressure pump. The pressurized discharge from the high-pressure pump is combined with the air stream from the air compressor, forming a two-phase stream. Next the air/waste stream passes through the feed/effluent heat exchanger, recovering heat from the hot, oxidized effluent. The heated mixture is then routed through an auxiliary heat exchanger, if needed. A vertical bubble-column is commonly used as the reactor to provide the required hydraulic detention time to effect the desired reaction. The reactor contents are mixed by the action of the gas phase rising through the liquid. As the gas phase rises and mixes with the liquid, oxygen is dissolved into the liquid. The reactor is sized to allow the oxidation reactions to proceed to the desired level. The desired reaction may range from a mild oxidation, which requires a few minutes, to total waste destruction, which requires an hour or more of detention time.
The oxidized liquid, oxidation product gases, and spent air leave the reactor and are routed through the shell side of the feed/effluent heat exchanger. A cooler can achieve additional cooling, if necessary. The cooled reactor effluent is throttled through a pressure control value into the process separator where the reactor effluent is separated into a gaseous stream and a liquid stream. The gaseous stream from the process separator is routed through an off-gas cooler. The liquid stream is pumped beyond the treatment system's boundary limits. Further treatment of these oxidized liquids by a biological system may be required prior to discharge into the final receiving system (publicly-owned treatment work, river, lake, etc.).
The Phase II wet air oxidation tests were performed in titanium-stirred laboratory autoclaves, each having a capacity of 3.78 L. The autoclaves were equipped with a magnetic stirring device to help the oxygen diffuse into the liquid and keep the solids in suspension. The stirrer remained on throughout the oxidation.
The as-received feed samples were removed from their jars and placed in a stainless-steel mixing bowl. A continuous mixer was used to stir the samples to obtain homogeneity. The feed material was divided into seven portions for testing and two samples for the analysis of the raw feed. Separate stirred autoclave oxidations were performed using six of the seven samples. The samples were diluted, using HPLC grade water, to produce an autoclave feed sample with a suspended solids concentration of approximately 10 percent. Ten percent suspended solids was used to simulate the 10 to 20 percent concentrations that would be used in a commercial unit to allow the sediment to be pumped at pressure. This does not mean that all the additional water needs to be supplied as feed water; some can be recycled from the filtrate after treatment. Based on the Phase I test, a reactor temperature of 280deg.C and a hydraulic detention time of 90 minutes was selected for the Phase II tests. These conditions were selected to provide a balance between PAH destruction and process economics.
The autoclaves were charged with the sediment slurry and sufficient compressed air to result in excess oxygen remaining following oxidation. The charged autoclaves were then heated to the desired oxidation temperature by electrical heating bands and held at that temperature for the specified reaction time. Immediately following the oxidation, the autoclaves were cooled to room temperature by internal water cooling coils and then depressurized.
1.3.4.4 Soil Tech's ATP^reg. Technology
SoilTech's ATP^reg. Technology employs a modified rotary kiln to thermally separate oil and hazardous organic waste from contaminated soils and sludges. As shown in Figure 9, the full-scale ATP^reg. has four treatment zones: the preheat zone, the retort zone, the combustion zone, and the cooling zone. Organic matter introduced to the ATP^reg. unit undergoes distillation and thermal cracking within the retort zone. Partially treated solid product entering the rotating, cylindrical combustion zone receives further treatment at temperatures near 675deg.C to oxidize the remaining coke present on the inorganic soil fraction. The volatiles released during treatment are vented into a condensing system, where aqueous and liquid hydrocarbon (oily) streams are collected. Gaseous combustion products from the combustion zone of the full-scale ATP^reg. are treated in a flue gas handling system and vented to the atmosphere. A baghouse, wet scrubber, or combination of the two may be used to remove dust, trace particulates, or acid gases from flue gases exiting the cooling zone before venting to the atmosphere. Activated carbon treatment of system off-gases may be required. Tailings exiting the ATP^reg.'s cooling zone are cooled by water addition.
During Phase II testing, up to 3 kg of material was placed into a steel cylindrical rotating retort chamber (Batch Pyrolysis Unit). The chamber was rotated at 4 (rpm) and heated by electrical heat tracing to temperatures up to 700deg.C. During operation, a vacuum of 1 inch of H2O was maintained in order to extract distillate vapors from the chamber continuously.
The cooled solids were placed in the aerobic Batch Combustor where they were showered in an air stream at temperatures of approximately 675deg.C. The rotational speed was maintained at 4 rpm and the offgases were continuously monitored for O2, CO2, NO2, and CO using gas analyzers. The run was terminated when the O2 concentrations achieved levels representative of ambient air, indicating combustion was complete.

1.3.5 Technologies Applied to Each Sediment

Of the seven treatability tests conducted, four different technologies were tested and four types of sediments were treated. Table 2 differentiates the seven tests according to the technology tested and sediment treated.

1.3.6 Analytical Laboratory

In order to limit interlaboratory variation, the different sediments and their residuals were analyzed by a single subcontractor to SAIC, Battelle Marine Sciences Laboratory (Battelle) in Sequim, Washington.

3.4 Individual Technology Report References

The reports detailing each individual technology evaluation are available from GLNPO under the following titles:

FIGURES

ARCS Priority Areas of Concern
Buffalo River Sample Location
Saginaw River Sample Location
Grand Calumet River Sample Location
Ashtabula River Sample Location
ReTeC Process Flow Diagram
Flow Diagram for the B.E.S.T.^reg. Process
Flow Diagram for the Zimpro Wet Air Oxidation Process
Simplified Anaerobic Thermal Process Flow Diagram

TABLES

Sediment Characterization Data
Sediment Treated by Each Treatment Technology
Parameters for Analysis of ARCS Program Technologies
Analytical Matrix and Sample Identification
Removal Efficiencies for Total PCBs
Removal Efficiencies for Total PAHs
Battelle Data - Removal Efficiencies for Other Parameters
PAH and PCB Concentrations in Treated Waters and Produced Oils
Mass Balances

Assessment and Remediation of Contaminated Sediments (ARCS) Program

Monitoring Links

Bench-Scale Evaluation of Sediment Treatment Technologies

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