FINAL PRE-DESIGN ENGINEERING REPORT 2--VOLUME 3 OF 4 · FINAL PRE-DESIGN ENGINEERING REPORT H DAVIS LIQUID WASTE SITE SMTTHFIELD, RHODE ISLAND ... conducted a bench-scale treatability

VOLUME 3

FINAL PRE-DESIGN ENGINEERING REPORT H DAVIS LIQUID WASTE SITE SMTTHFIELD, RHODE ISLAND CONTRACT NO. DACW45-90-D-0008

Prepared for:

U.S. Department of the Army Corps of Engineers New England Division Waltham, Massachusetts October 1993

Prepared by:

5120 Butler Pike Plymouth Meeting, Pennsylvania 19462

Project No. 89MC114J-9

WcMMlward-Clyde Consultants

TABLE OF CONTENTS

Section Page No.

Bl.O INTRODUCTION Bl-1

Bl.l BACKGROUND Bl-1

Bl.1.1 Project Overview Bl-1

B 1.1.2 Water Contaminant Characteristics Bl-1

B1.2 REMEDIAL TECHNOLOGY DESCRIPTION Bl-3

B2.0 TREATABILITY STUDY APPROACH B2-1

B2.1 TEST OBJECnVES B2-2

B2.1.1 Chemical Precipitation Test Objectives B2-2

B2.1.2 Activated Carbon Test Objectives B2-3

B2.1.3 Air Stripper Modeling B2-3

B2.2 SAMPLING AND ANALYSIS B2-4

B2.3 EQUIPMENT AND MATERL^LS B2-5

B2.3.1 Chemical Precipitation Test B2-5

B2.3.2 Carbon Adsorption Test B2-6

B2.4 EXPERIMENTAL PROCEDURES AND RESULTS B2-6

B2.4.1 Chemical Precipitation B2-6

B2.4.2 Carbon Adsorption B2-10

B2.5 DATA MANAGEMENT B2-12

B2.6 DEVIATIONS FROM WORK PLAN B2-12

B3.0 DATA ANALYSIS B3-1

B3.1 EXPERIMENTAL DATA ANALYSIS B3-1

B3.1.1 Chemical Precipitation Tests B3-1

B3.1.2 Carbon Adsorption Tests B3-2

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Woodward^lyde Consultants

TABLE OF CONTENTS (continued)

Section Page No.

B3.2 AIR STRIPPER ANALYSIS B3-3

B3.2.1 Design BasisB3.2.2 Air Stripper Performance Modeling

B3-3 B3-4

B3.2.2.1 Analysis of Packing Media B3-7

B3.2.2.2 Analysis of Air-to-Water Ratio B3-8

B3.2.3 Air Emission Control Analysis B3-9

B4.0 REGULATORY ISSUESB4.1 ARAR IDENTIFICATION AND VERIFICATIONB4.2 NPDES REQUIREMENTSB4.3 WASTE CHARACTERIZATION FOR SLUDGE

DISPOSALB4.4 AIR REGULATIONS ASSOCIATED WTTH

AIR STRIPPING

B4-1 B4-1

B4-2

B4-3

B4-3

B5.0 APPLICABILITY TO FULL SCALE DESIGN B5-1

B5.1B5.2B5.3B5.4

DESIGN BASIS CHEMICAL PRECIPITATION CARBON ADSORPTION AIR STRIPPER DESIGN CONCEPT

B5-1 B5-2

B5-3 B5-4

B6.0 CONCLUSIONS AND RECOMMENDATIONS B6-1

B6.1B6.2

CONCLUSIONS RECOMMENDATIONS

B6-1 B6-2

B7.0 REFERENCES B7-1

89MC114J-9/APXB-DAV.V-3/ACOE5 B - i i 10-22-93

LIST OF TABLES

TABLE Bl-1

TABLE B2-1

TABLE B2-2

TABLE B2-3

TABLE B2-4

TABLE B2-5

TABLE B2-6

TABLE B2-7

TABLE B2-8

TABLE B2-9

TABLE B3-1

TABLE B4-1

TABLE B4-2

TABLE B4-3

TABLE B4-4

TABLE B4-5

Woodward-Clyde Consultants


CONCENTRATIONS OF HUMAN HEALTH INDICATOR COMPOUNDS DETECTED IN SURFACE WATERS AND GROUNDWATER AT THE DAVIS LIQUID SITE (ppb)

RESULT FOR MONTTORING WELL OW-51

BULK SAMPLE BASELINE CHARACTERIZATION

pH ADJUSTMENT TEST RESULTS

REAGENT ADDITIONS, FILTERED SOLIDS WEIGHTS, AND Fe AND Mn ASSAYS OF FILTRATES FROM COAGULATION AND FLOCCULATION STUDIES

COAGULANT/FLOCCULANT SCREENING TEST RESULTS

COAGULANT/FLOCCULANT OPTIMIZATION TEST RESULTS

SLUDGE PRODUCTION TEST RESULTS - TCLP METALS

GROUNDWATER TREATED WITH CARBON - CALGON FILTERSORB RESULTS

GROUNDWATER TREATED WITH CARBON - CAMERON YAKIMA RESULTS

SUMMARY OF FRUENDLICH ISOTHERM PARAMETERS

GROUNDWATER DISCHARGE LIMITS

NATIONAL AMBIENT AIR QUALITY STANDARDS

ACCEPTABLE AMBIENT LEVELS

MINIMUM QUANTITIES

ACCEPTABLE AMBIENT LEVELS WITH LAER

89MC114J-9/APXB-DAV.V-3/ACOE5 B-iii 10-22-93



LIST OF TABLES - continued

TABLE B5-1 DESIGN BASIS ANALYSIS

TABLE B5-2 MAXIMUM CONTAMINANTCALCULATION

CONCENTRATION

TABLE B5-3 VOC EMISSIONSDESIGN

FOR CONCEPTUAL AIR STRIPPER

LIST OF FIGURES

FIGURE B3-1 AIR STRIPPER PACKING HEIGHT VS. AIR-TO-WATER RATIO

DAILY QUANTITY OF GAC REQUIRED FOR EMISSION FIGURE B3-2 CONTROL VS. THE AIR/WATER RATIO IN THE AIR

STRIPPER

DAILY QUANTITY OF GAC REQUIRED FOR EMISSION FIGURE B3-3 CONTROL VS. THE AIR/WATER RATIO IN THE AIR

STRIPPER

FIGURE B5-1 CONCEPTUAL DESIGN FOR GROUNDWATER PRETREATMENT

89MC114J-9/APXB-DA V.V-3/ACOE5 B-iv 10-22-93



LIST OF APPENDIXES

FINAL PRE-DESIGN ENGINEERING REPORT - VOLUME 4

APPENDIX B-A RAW ANALYTICAL DATA (BULK AND TREATABILITY

STUDY DATA)

APPENDIX B-B LABORATORY NOTES

APPENDIX B-C FLOCCULANT LITERATURE

APPENDIX B-D CARBON ADSORPTION CALCULATIONS AND

INFORMATION

APPENDIX B E AIR STRIPPER PROGRAM RUNS

APPENDIX B-F COST ESTIMATE

89MC114J-9/AI'XB-DAV. V-3/ACOE5 B-v 10-22-93


Bl.O

INTRODUCTION

Hazen Research, Inc. (Hazen), under contract to Woodward-Clyde Consultants (WCC), conducted a bench-scale treatability study of a groundwater sample collected from the Davis Liquid Waste Site in Smithfield, Rhode Island. Water testing included pH adjustment, coagulation, and flocculation testing to evaluate inorganic removal from the Davis water, as well as carbon adsorption testing to evaluate removal of organic constituents. WCC conducted air stripper modeling to evaluate removal of organic constituents. This document presents the results of the bench-scale treatability study including a regulatory review and information obtained from carbon adsorption system suppliers.

Bl.l BACKGROUND

Bl.1.1 Project Overview

Surface water and groundwater at the Davis Liquid Waste Site (the site) in Smithfield, Rhode Island, are contaminated with both organic and inorganic compounds from previous dumping activities. As indicated in the Record of Decision (ROD) (U.S. EPA 1987) for the site, the selected remedy for these contaminated waters is air stripping followed by carbon adsorption with an optional chemical precipitation pretreatment step. Treated water is to be reinjected into the groundwater at the site.

Bl.1.2 Water Contaminant Characteristics

As described in the ROD, general categories of the wastes disposed of at the site were determined during the Remedial Investigation (RI). The sources of contaminants in surface waters and groundwaters included:

• Sludge containing paint pigments and metals

• Oily wastes

• Solvents

89MC114J-9/APXB-DAV.V-3/ACOE5 B l - 1 10-21-93


• Chemicals such as acids, caustics, pesticides, phenols, halogens, and metals • Solids containing fly ash and metals

• Laboratory pharmaceuticals

During the RI, contaminants were found throughout the site in surface waters and groundwater. The extent of groundwater contamination at the site included both the overburden and bedrock aquifers. Water samples were analyzed for four groups of compounds to determine the type and extent of contamination, including:

Volatile organics

Acid and base/neutral extractable organics

Pesticides/PCBs

Metals

Water quality parameters

After a preliminary risk analysis conducted as part of the RI, thirteen compounds were selected as human health indicator compounds. Table Bl-1 lists these compounds and their mean and maximum concentrations detected in surface water and groundwater at the site. This data is included in this report to provide background information. While the compounds listed in Table Bl-1 probably pose the most risk to human health, 70 compounds from all four analysis groups were detected in water samples from the Site. Detailed analytical results are included in the RI Report (Camp Dresser & McKee, Inc. 1986).

The bulk water sample for the bench-scale treatability study was collected from OW-51

on December 17,1991 and shipped to Hazen. Rocky Mountain Analytical Lab (RMAL)

analyzed a split for halogenated volatile organics, acid and base/neutral extractable

organics, pesticides/PCBs, metals, and water quality parameters. A total of 23

compounds was detected in the bulk water sample. The halogenated volatile organics

detected include vinyl chloride, 1,1-dichloroethane, trans-l,2-dichloroethene, chloroform,

1,1,1-trichloroethane, trichloroethene, and tetrachloroethene. The metals detected

include lead, aluminum, barium, calcium, chromium, cobalt, copper, iron, magnesium,

manganese, nickel, potassium, silver, sodium, vanadium, and zinc. A comparison of

treatability study samples to previous RI data is provided in Section B2.2 of this report.



B1.2 REMEDIAL TECHNOLOGY DESCRIPTION

Three processes were evaluated as part of the bench-scale treatability study. These processes are chemical precipitation, carbon adsorption, and air stripping.

Chemical Precipitation; Chemical precipitation is the process of making dissolved chemical constituents insoluble so that they can be separated from the liquid (U.S. EPA 1985; Wentz 1989). Precipitation is usually accomplished by adding a chemical that forms an insoluble compound with the target contaminant. Hydroxide and sulfide precipitation are cormnonly used for removing heavy metzds. Typical precipitating agents include sodium hydroxide, lime, ferric hydroxide, and sOdium sulfide. The precipitates are often flocculated into larger particles (floes) with the help of coagulants prior to solids removal. Chemical precipitation systems are relatively simple to operate and equipment and chemicals are readily available. However, the method generates a sludge that requires further treatment and/or disposal. If present, organometallic complexes may inhibit precipitation of the metals. There is no upper concentration limit for treatment but the lower concentrations are limited by equilibrium solubilities of the individual precipitates. The removal efficiencies are determined by the solubility products of the salts formed. However, some contaminants may be coprecipitated with the sludge that is formed, and may be removed to concentrations below their solubility limits.

Carbon Adsorption; Granular activated carbon (GAC) adsorption is based on the

attraction of organic molecules in solution to the surface of the activated carbon. The

adsorption process is dependent on the strength of the molecular attraction between the

carbon and the organic contaminant, the type and characteristics of the carbon, and the

pH and temperature of the solution. Nonpolar organic compounds of low water

solubility are most easily adsorbed (U.S. EPA 1986). GAC adsorption is one the most

frequently used techniques for treating aqueous streams contaminated with organics.

The carbon is placed in columns that are operated until the effluent concentration

reaches unacceptable levels. At this point the carbon has become saturated with the

contaminants and must be regenerated for reuse. The carbon is generally regenerated

thermally. Pretreatment is typically required for removal of oil, grease, and suspended

solids.



GAC adsorption is an effective process for removing a variety of organics from water. It has been successful for carbon tetrachloride, chloroform, DDT, benzene, methylene chloride, phenol, trichloroethylene, and xylene among others (U.S. EPA 1985). In general, GAC can reduce these contaminants from mg/l concentrations to low /xg/1 concentrations.

GAC adsorption is a well known and developed technique for removing organic contaminants from water. The absorbability varies among different classes of organics, but most organics can be removed by this method; one exception being vinyl chloride. The major disadvantage of GAC adsorption is that it requires energy-intensive regeneration or disposal of the carbon, and large amounts of carbon are required for poorly adsorbable compounds, such as chlorinated volatile organics. Residuals include spent carbon and/or waste streams from the regeneration process.

Air Stripping; Air stripping is a proven technology for removing volatile and semi-volatile organic contaminants from water. The process involves transferring liquid phase contaminants to the vapor phase (U.S. EPA 1986). This is accomplished by applying liquid to the top of an air stripping column (tower) countercurrent to upflowing air. The tower is filled with packing that provides a large surface area to enable efficient mass transfer between the two phases. Contaminants are stripped from water to air depending on their relative volatility. Stripability is generally evaluated based on the Henry's Law constants of the compounds to be removed. The water concentrations of each compound decrease as they pass through the column. The removal efficiencies can be increased by increasing the height of the packed tower or the number of air stripping units. Process efficiency is also dependent on the air to water ratio; a higher air to water ratio will improve removal efficiencies. Since air stripping involves transfer of contaminants to the gas phase, air emission treatment is generally required. Vapor phase GAC systems are most conunonly used for this purpose, but other alternatives, such as oxidation and incineration, exist. The vapor phase treatment unit may be costly.

The applicability of air stripping can be determined from the Henry's Law constants of

the compounds to be removed. Generally, compounds with Henry's Law constants

higher than that for chloroform (H - 2.9 x 10'̂ atm'/mole) are considered suitable for

air stripping, but less volatile compounds may be removed using a high air to water ratio.



Low molecular weight halogenated organics are easily removed in this process, while it

is somewhat less efficient for removal of volatile aromatics such as benzene. Studies by

Fang and Khor (1989) show that removal efficiencies as high as 99.8 percent can be

achieved by air stripping of volatile organics, such as vinyl chloride, carbon tetrachloride,

TCE, 1,1-dichloroethane, toluene, chloroform, and xylene.

The major advantages of air stripping are ease of operation and high removal efficiencies for volatiles. Disadvantages of this technology are that efficient treatment is limited to volatiles, and transfer of contaminants to the vapor phase generally makes costly air emission treatment necessary. The concentrations of inorganic species in the water can also impact the operation of an air stripper. Water containing elevated concentrations of iron or manganese may result in precipitation of these metals on the tower packing and internals. Treatment of water with high hardness can result in the formation of scale on the tower packing. In such cases a pre-treatment step for removal of inorganics or a frequent maintenance program, to clean the tower packing, may be necessary to prevent loss of treatment efficiency.



B2.0

TREATABILITY STUDY APPROACH

The Water Treatability Study was conducted to aid in the determination of design parameters for the surface water and groundwater treatment system. In conjunction with this study, a review of all pertinent water and air discharge requirements and applicable or relevant and appropriate requirements (ARARs) was performed in order to determine the level of treatment required. Analyses were performed as part of this treatability study to ensure that the treatment system will be designed to remove contaminants to acceptable state and EPA levels. Three processes were evaluated further in order to refine their design: air stripping, chemical precipitation, and carbon adsorption.

A technical evaluation of the air stripping process was conducted. Computer modeling based on data obtained from the samples used for treatability studies and the most recent sampling events were used to evaluate different air-to-water ratios, examine different packing materials based on their mass transfer efficiencies, and determine whether off-gases from the air stripper would require treatment. Critical organic compounds were selected based on their Henry's constants for design of the air stripping unit. The results of this modeling was used to select the optimum design concept for an air stripper tower.

Laboratory bench-scale testing of groundwater samples was performed to evaluate the effectiveness of chemical precipitation on inorganic contaminant removal.^ As part of this treatability study, a discussion is included on design parameters such as feed chemicals and their dosage rates, required settling times, sludge productioif rate, and ultimate effluent quality.

Activated carbon was tested to evaluate its effectiveness in removing contaminants from

the groundwater. Adsorption isotherms were determined for total organic carbon (TOC)

and selected volatile organic compounds. Design parameters such as carbon type,

direction of flow, carbon column contact time and depth, carbon usage, breakthrough

characteristics, and headloss characteristics were determined based on discussions with

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Wdodward-Clyde Consultants

carbon adsorption system suppliers. Regeneration options, pretreatment requirements,

and any potential deleterious effects were also addressed.

B2.1 TEST OBJECTIVES

The primary objective of this testing program was to provide technical support in the form of bench-scale treatability tests, computer modeling, and discussion with vendors in order to determine the effectiveness and to identify engineering parameters for organic and inorganic treatment processes. The data collected during this program were intended to establish an engineering design basis for pilot-scale design, full-scale system design, and to chemically characterize treatment process residuals. The following sections outline the specific objectives for each set of tests.

B2.1.1 Chemical Precipitation Test Objectives

The primary objective of the bench-scale precipitation test was to evaluate the effectiveness of precipitation for the removal of inorganic contaminants in the groundwater. The specific testing objectives were as follows:

• To determine the optimum pH for inorganic contaminant removal

• To evaluate caustic soda and lime as pH adjustment additives

• To evaluate the effectiveness of iron and aluminum salts as coagulant aids

during the precipitation process

• To evaluate the effects of polymer addition (flocculants) on the precipitation process

• To determine the required settling times and sludge production rates for

the concept design and ultimate effluent qualities

• To chemically characterize the process residuals associated with the

precipitation process to determine if the sludge is hazardous



• To identify any and all deleterious sidestreams produced in the process

• To determine quantities of chemicals requiring storage for full-scale operation

B2.1.2 Activated Carbon Test Objectives

The primary objective of the activated carbon tests was to evaluate the effectiveness of activated carbon in removal of organic contamination from the groundwater. The specific testing objectives were as follows:

• To develop carbon adsorption isotherms for two different commercially available GAC types

• To determine carbon usage in terms of amount of carbon necessary to treat 1000 gallons of contaminated groundwater

• To determine carbon column contact time and depth for desired water

quality

• To determine pretreatment requirements

• To evaluate breakthrough characteristics (i.e., identify problem constituents of the contamination)

• To determine potential deleterious effects

• To determine head loss characteristics

B2.1.3 Air Stripper Modeling

The primary objective of the air stripper modeling was to technically evaluate the

stripper process for applicability in treating organic contamination in the groundwater.

The specific objectives of the modeling were:



• To determine the chemical characteristics of off-gases associated with the

stripper process to determine if treatment is required

• To evaluate organic removal efficiency at different air-to-water ratios

• To examine different air stripper packing media based on their mass transfer efficiency

• To optimize the air stripper tower design based on treatability study sample data and results of the most recent sampling event

• To determine the necessity of groundwater pretreatment prior to air stripping and carbon adsorption

• To evaluate and select critical organic compounds (low Henry's constant) for design of air stripping units

• To identify and discuss any potential plugging problems associated with the air stripping units

B2.2 SAMPLING AND ANALYSIS

Samples of groundwater for inclusion in the water treatability study were to be collected

concurrently with the aquifer pump test. Due to logistical considerations associated with

storage of water to be collected during the pump test, and the onset of winter and

freezing conditions, the schedule for completion of the aquifer pump test was delayed

until August 1992. The US ACE initiated change orders so the water treatability

groundwater sample could be collected from a well that was believed to be

representative of the groundwater that would be treated. Based on a review of the 1985

RI groundwater characterization data collected from across the site, WCC and USACE

persormel selected well OW-51 as an alternative groundwater source for the water

treatability study. This well was sampled on November 16, 1991 and the groundwater

was analyzed for volatile and semi-volatile organics, chlorinated pesticides and PCBs,

and metals. The results are presented in Table B2-1.

89MC114J-9/APXB-DAV.V-3/ACOE5 B2-4 10-21-93


Nine five-gallon carboys collected from OW-51 on December 17, 1991 were shipped to Hazen from the site (no head space). Upon receipt, the carboys were randomly given identification numbers (1 to 9). The pH of the water contained in each carboy was measured, and the results ranged from 6.18 to 6.51. Visual observation of the sample showed it to be a yellow-colored water with evidence of free sediment settled at the bottom. There was a slight organic odor from each of the nine carboys.

Each carboy was shaken (to put the sediment into suspension) and sampled. A three-liter homogeneous composite was formed by combining equal volumes from each of the nine carboys. This procedure was duplicated and all samples collected were submitted to Enseco, Inc., Rocky Mountain Analytical Laboratory (RMAL) for analysis. Total suspended solids (TSS), total dissolved solids (TDS), TOC, purgeable halocarbons, and total and dissolved metals analyses were performed in accordance with the project Quality Control and Sampling Plan. The results of the baseline characterization are shown in Table B2-2. Raw analytical data can be found in Appendix A, Volume 4. The BTEX groundwater results for well OW-51 were also used for the baseline characterization (Table B2-1).

The results of the baseline characterization of the bulk treatability samples falls near or below the historic mean concentrations detected in groundwater at the site (Table Bl-1). This baseline characterization data will also be compared to recently collected Pre-Design Activity data for design basis determination (Section B5.1).

B2.3 EQUIPMENT AND MATERIALS

B2.3.1 Chemical Precipitation Test

A Phipps & Bird multiple jar testing apparatus with paddle stirrers operating at 80 rpm

was used for jar testing. Testing was performed using both 1-liter and 2-liter Pyrex

graduated beakers. A reagent rack for adding reagents simultaneously to each of the

beakers was also used. A Biichner vacuum filter fuimel with Whatman's No. 2 filter

paper was used for sludge collection. To aid in determination of the settling rate, the

jars were illuminated from the bottom by fluorescent lighting. Details of the equipment.

89MC114J-9/APXB-DAV.V-3/ACX)E5 B 2 - 5 10-21-93


materials, and experimental procedures used are included in the Water Treatability

Testing Plan (WCC 1991).

B2.3.2 Carbon Adsorption Test

GAC adsorption tests were conducted using one-liter, ground-glass stoppered reagent bottles. Magnetic stirrers were used to mix the carbon/water slurry. Prior to use, the carbon samples were dried in a drying oven. Supernatant was extracted for analysis using 50-ml syringes. Complete details of the equipment and testing procedures are presented in the Water Treatability Testing Plan (WCC 1991).

B2.4 EXPERIMENTAL PROCEDURES AND RESULTS

The design and procedures for the water treatability studies were presented in the Water Treatability Testing Plan (WCC 1991). The following summarizes the implementation of the plan, including intermediate analytical results necessary to proceed with the testing protocol. Laboratory notes taken during implementation of the tests are found in Appendix B. A discussion and analysis of the results are included in Section B3.

B2.4.1 Chemical Precipitation Test

Chemical precipitation for inorganic contaminant removal was evaluated using jar tests.

Iron and manganese were selected as indicator metals to evaluate the effectiveness of

the precipitation process. These contaminants were selected since they are most

commonly found at elevated concentrations and cause problems with organics removal

systems such as air strippers. The first step in the tests was pH adjustment. The water

was pH adjusted with two basic solutions, 5% sodium hydroxide (NaOH) and 5%

calcium hydroxide (Ca(OH)2) to achieve pH 8, 9, and 10 (six samples total). The

adjusted samples were stirred for 15 minutes at 40 rpm and allowed to settle for 30

minutes. Following settling, the samples were vacuum filtered. Filtrate splits were

collected for TSS, TDS, and metals analyses. The results of the pH adjustment are listed

in Table B2-3.



The iron results indicate that increasing the basicity of the sample above pH 8 did not significantly improve iron reductions from the treated water. However, increased Mn removal was clearly a function of increased pH. These results led to the determination that subsequent testing for inorganic removal would be performed using water adjusted to pH 10. Although adjustments to pH 10 showed similar reductions of Fe and Mn using either NaOH or Ca(OH)2, NaOH was chosen as the base for pH adjustments in subsequent tests because of ease of handling and less sludge production during full scale operation.

The next portion of the testing was to determine the effects of coagulants or flocculants on the removal of metals from the Davis water. This testing was performed on water adjusted to pH 10 using 5% NaOH. One-percent solutions of ferric sulfate ([Fe2(S04)3]-XH20) and aluminum sulfate ([Al2(S04)3] • 16-18 H2O) were used as the coagulants for this portion of the testing.

Prior to testing, the coagulants and flocculants were screened as follows. Preliminary tests were performed using 200-milliliter samples of Davis water (mixed continuously and adjusted to pH 10) to determine the volume of each coagulant solution required to produce floe formation. The results of these tests showed that four milliliters of 1% ferric sulfate solution provided floe formation in the 200-milliliter sample (equivalent to 0.02 milliliter coagulation solution per milliliter of water), while two milliliters of 1% aluminum sulfate solution were required per 200 milliliters of water (equivalent to 0.01 milliliter coagulant solution per milliliter of water).

Four different flocculants (Superfloc 212, Superfloc 330, Superfloc 127, and Superfloc

16) were evaluated, using procedures similar to the coagulant screening tests to

determine which provided the most noticeable floe formation and the fastest settling

time. For details on the flocculants, refer to Appendix C. The flocculant solutions

tested had a concentration of one gram per liter. Two drops of each flocculant solution

were added to separate 200-milliliter samples of Davis water which had been adjusted

to pH 10. Two of the flocculants (Superfloc 212 and Superfloc 127) showed immediate

floe formation in the solution; the other two did not and were no longer considered.

Addition of one drop of the two remaining flocculants to their respective water samples

did not show increased floe formation in either sample. The mixing apparatus was



turned off simultaneously for each sample to observe the setfling characteristics. The floe

particles in the sample containing Superfloc 212 settled to the bottom immediately, while

those in the water sample containing Superfloc 127 did not settle as quickly. Therefore,

Superfloc 212 was chosen as the best of the four flocculants screened.

Following screening, the coagulant and flocculant testing began. Each coagulant (1% solution) was added to separate one-liter samples of Davis water (adjusted to pH 10) at dosages of 50,1(X), 150, and 2(X) percent of the respective concentrations determined by the screening process discussed above. Sufficient NaOH solution was added to each sample after coagulant addition to return the sample to pH 10. The samples were mixed rapidly (80 rpm) during coagulant addition and pH adjustment, followed by 15 minutes of slow mixing (40 rpm).

Superfloc 212 (one gram per liter solution) was added at concentrations of 0.5, 1.0, 5.0, and 10 milligrams per liter to separate one-liter samples of the Davis water adjusted to pH 10. These samples were mixed rapidly when adding the flocculant dosages, followed by a five-minute mixing period. In accordance with the procedures outlined in the treatability test plan, pH adjustments were not made following flocculant addition.

Following the mixing period, all samples were transferred to one-liter graduated

cylinders and allowed to settle for two hours and settling characteristics were monitored.

In all cases, a predominant volume of the floe particles had settled to the bottom of the

cylinders within ten minutes. However, minute traces of solids remained in suspension

in all samples throughout the two-hour settling period. By visual observation, it is

estimated that well over 99% of the total floe particles were settled in each sample. The

settled solutions were filtered, and the filtrates saved for required analysis. Wet filtered

solids were weighed, dried overnight, and reweighed. Data collected during the

coagulation and flocculation tests are provided in Table B2-4. Table B2-5 presents the

analytical test results for metals, TDS, and TSS.

After reviewing the results from Table B2-4, representatives of WCC and Hazen agreed

that the ferric sulfate 200% dosage (equivalent to 40 milliliters of 1% ferric sulfate

solution per one liter of water) provided the best results in terms of Mn removal from

the water. The Fe concentrations were comparable for both 1% Ferric Sulfate and



Superfloc 212, so the decision was based on Mn results. The Fe concentration in this

sample measured 0.063 ppm, while the Mn measured 0.03 ppm.

The final step in the chemical precipitation testing was a settling rate determination test on optimum pretreatment conditions. The purpose of this test was to repeat the test procedure from the coagulation/flocculation tests that demonstrated the best Fe and Mn removal (to confirm the metal removal results) and to determine the mass of floe (sludge) which would be produced from the selected coagulant or flocculent addition. As previously mentioned, results from Table B2-4 confirmed that the ferric sulfate 200 percent dosage proved best for removal of Fe and Mn under the coagulation/ flocculation testing. Therefore, this coagulant dosage was selected for the settling rate study.

In this test, two liters of Davis water were adjusted to pH 10 with 5% NaOH while mixing rapidly (80 rpm). After pH adjustment, 80 milliliters of 1% ferric sulfate solution was added. Approximately 7.4 milliliters of 5% NaOH was added immediately thereafter to adjust the water to pH 10. The solution was mixed slowly (40 rpm) for 15 minutes, then transferred to a two-liter graduated cylinder and allowed to settle for one hour. The settling characteristics were very similar to those observed during the original coagulation test. Virtually all of the sludge settled to the bottom of the graduated cylinder within ten minutes, but a small volume of the floe remained in suspension throughout the one-hour period. The sludge level in the graduated cylinder measured 80 cubic centimeter (cc) after one hour of settling.

After the second settling period, the sample was filtered. The sludge collected from

filtration weighed 3.68 grams wet; the dry weight measured 1.15 grams. Filtrate was

saved and submitted to RMAL for TSS, TDS, and metals analyses. For quality control,

a duplicate sample of the filtrate was collected and submitted to RMAL for the same

analysis suite. The results from RMAL are presented in Table B2-6. The Fe

concentrations for the optimized condition are 0.099 and 0.10 mg/l. The Mn

concentrations are 0.035 and 0.037 mg/l.

The balance of Davis water remaining at Hazen was treated using 1% ferric sulfate

solution to produce as much sludge as possible for a Toxicity Characteristic Leaching

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Vlfoodward-Clyde Consultants

Procedure (TCLP) test. A total of 113.5 liters (30 gallons) of water was treated under this final phase of the program.

Some pebble-sized gravel (1/8 to 1/4 inch) was found in the bottom of all carboys when the water was collected for the sludge production test. Because this material was not included in the test solutions previously used in this program, representatives of WCC and Hazen agreed not to include it in the sludge production test. However, sediment that could be suspended in solution was used as test solution. This material had been part of the test solutions used throughout the other portions of this program.

The 113.5 liters of Davis water was treated in a 55-gallon poly drum, equipped with a large mixer and poly-lined impeller. The water (pH 6.56) was adjusted to pH 10 with 90 milliliters of 5% NaOH solution. Following pH adjustment, 4540 milliUters of 1% ferric sulfate solution (40 milliliters ferric sulfate solution per liter of water) was added, plus 498 milliliters of 5% NaOH to bring the sample back up to pH 9.98. The solution was mixed for 15 minutes at which time the pH measured 9.94. It was then allowed to settle for two hours.

Following settling, supernatant was decanted from the barrel and collected in buckets. A representative slip stream of the supernatant (five gallons) was collected during the decanting process. This sample was filtered and saved for metals, TSS, and TDS analyses to be conducted by RMAL. The results are presented in Table B2-6.

The sludge was transferred from the barrel to a five-gallon bucket and allowed to settle over night in a refrigerated cooler. Additional supernatant was extracted from above the sludge, and the final residue was placed on a filter to drain additional moisture from the sample. Sludge was collected from the filter paper, and the paper rinsed to remove all solid matter. The semi-wet sludge (600.6 grams) was double sealed in Ziploc®-style bags and delivered to RMAL for TCLP analysis. The results are presented in Table B2-7.

B2.4.2 Carbon Adsorption Test

Carbon adsorption for organic contaminant removal was evaluated on the laboratory "bench-top" using small stoppered beakers containing samples of contaminated



groundwater and GAC. A standard adsorption isotherm procedure was used to determine the adsorptive capacity of two types of GAC. Various carbon dosages were added to groundwater samples in stoppered reagent bottles and mixed for approximately six hours to ensure that equilibrium was reached. The supernatant was analyzed for both TOC and volatile organic compounds (VOCs). The VOC analysis allowed for a complete screening of all volatiles and was compared with drinking water standards. The procedure is described below.

Carbon adsorption tests were conducted using Cameron-Yakima and Calgon Filtersorb 300 GAC. The purpose of these tests was to evaluate the activated carbon samples for removal of organic species from the Davis water. The test work for this portion of the program was conducted simultaneously with the optimum pH and coagulation/ flocculation studies.

Initial testing utilized 0.5-gram, 1-gram, 2-gram, 5-gram, 10-gram, 25-gram, 50-gram, and 100-gram additions of each GAC to separate one-liter samples of as-received Davis water. A sample of the Davis water without carbon was used as a control. Each sample was mixed with a magnetic mixer for a period of 20 hours in a glass bottle with a ground-glass stopper. Following the mixing period, the solutions were allowed to settle (five minutes) and sampled using syringes. Noticeable carbon was found to have remained in suspension of test samples with the higher carbon dosages. Results of rush TOC analysis by a Hazen subcontractor lab (Huffman Laboratories) confirmed the presence of organic carbon in nearly all test solutions, at significantly higher concentrations than in the control. Apparently, the suspended carbon was contributing to the level of organic carbon measured in the test samples. This was considered undesirable. Therefore, the work was repeated using smaller GAC additions and less rigorous mixing.

Carbon adsorption tests were conducted a second time using a modified test procedure.

For these tests, activated carbon dosages were 10,50,100, 250,500,1000,2000, and 3000

milligrams per liter of Davis water. Smaller carbon dosages were selected in the

modified test procedure to minimize carbon breakup during mixing and to account for

the lower than anticipated concentration of volatiles (low TOC values.) The test

samples (including a control) were mixed for a period of four hours and allowed to settle

89MC114J-9/APXB-DAV.V-3/ACX)E5 B 2 - 1 1 10-21-93


for 45 hours. This procedure was conducted to allow any suspended carbon to settle before sampling. Visual observation of the solutions during sampling found them to be clear. Samples were collected in the same marmer as in the first series of carbon tests, and delivered to RMAL for TOC and purgeable halocarbon analysis. Results of the carbon adsorption tests for Calgon and Cameron-Yakima GAC are presented in Tables B2-8 and B2-9, respectively.

The water quality analyses for the control samples for both the original and modified carbon tests were compared. The organic constituent concentrations did not significantly vary between the tests.

B2.5 DATA MANAGEMENT

The results of the treatability studies will be used to evaluate effectiveness, establish an engineering design basis, and characterize residual materials associated with the water treatment process. This study utilized "bench-scale" testing levels as defined by the USEPA (USEPA 1989). The term "bench-scale" testing refers to bench-top separation, reaction, or other treatment steps done in the laboratory with equipment designed to simulate the basic operation of a treatment process. Bench-scale testing is intended to determine the technology's applicability and to establish the effect of critical engineering parameters on system performance. This level of testing yields quantitative performance data and is accompanied by moderate levels of QA/QC. Standard non-CLP reporting was provided for all analytical data. WCC reviewed data packages for completeness, holding times, matrix spike/matrix spike duplicate recoveries, surrogate recoveries, method blanks, and instrument performance criteria and found the data quality to be within acceptable Umits for the bench-scale study.

B2.6 DEVIATIONS FROM WORK PLAN

The following adjustments were made to the work plan as the treatability tests were

being conducted:

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As discussed in Section B2.2, the bulk treatability sample was not collected

concurtently with the aquifer pump testing program. The sample was

collected from existing well OW-51.

As discussed in Section B2.4.2, the carbon adsorption testing protocol was modified to prevent the granular activated carbon from entering the solution and impacting the TOC results.

Previous RI data was not used for air stripper modeling. Weighted average contaminant concentrations were developed based on recent characterization data as a design basis for air stripper modeling and conceptual design considerations.



B3.0

DATA ANALYSIS

In this section, a discussion of the water treatability studies conducted using groundwater samples from the Davis-Liquid Waste Site and air stripper modeling analysis is presented.

B3.1 EXPERIMENTAL DATA ANALYSIS

B3.1.1 Chemical Precipitation Tests

As discussed in Section B2.2.1, the chemical precipitation tests involved multiple steps. The first step was pH adjustment. Table B2-2 shows the results of adjusting the raw water to pH 8, 9, and 10 with both sodium hydroxide solution and calcium hydroxide solution. These results indicate that pH 10 yields the lowest concentrations of iron and manganese. A pH of 10 was selected and sodium hydroxide was chosen as the base for pH adjustments, as discussed in Section B2.4.1.

The second step was coagulant and flocculent testing. Two coagulants, ferric sulfate

([Fe2(S04)3]-X H2O) and aluminum sulfate ([Al2(S04)3]-16-18 H2O), and four

flocculants, American Cyanamid Superfloc 212, Superfloc 330, Superfloc 127, and

Superfloc 16 were tested. Coagulants and flocculants were added to raw water adjusted

to pH 10. An initial screening was carried out on each coagulant and flocculent to

determine the volume of each necessary to produce floe formation. Table B2-3 provides

the results of the initial screening.

Testing continued on both coagulants and the best performing flocculent, Superfloc 212,

at various concentrations. Table B2-4 shows results these tests for metals, total dissolved

solids, and total suspended solids. As discussed in Section B2.4.1, ferric sulfate 200%

dosage was selected as the most effective coagulant dose.

The final step in the chemical precipitation testing was a sludge production rate

determination test at the selected conditions. This test was carried out to confirm the



metal removal results and to determine the mass of floe (sludge) which would be produced from the selected coagulant addition. A groundwater sample volume of 2 liters was used for the test. The results are presented in Table B2-5. The iron and manganese concentrations listed are similar to the results seen in the original coagulation test using the ferric sulfate 2(X)% dosage.

The sludge collected from this test weighed 3.68 grams wet (1.84 g/1); the dry weight measured 1.15 grams (0.58 g/1). The balance of the Davis water was processed to produce sludge for TCLP analysis. Table B2-6 shows the results for TCLP metals and the regulatory limits. The produced sludge passes TCLP for all parameters listed. However, this may be due to the fact that the concentrations of TCLP metals in the original test water were very low.

B3.1.2 Carbon Adsorption Tests

Two commercially available granular activated carbons (Cameron-Yakima CC and Calgon Filtersorb 300) were evaluated. Eight carbon doses were used to provide data for the development of carbon adsorption isotherms for Total Organic Carbon (TOC), 1,1-dichloroethane, tetrachloroethene, trichloroethene, and vinyl chloride for each type of carbon. Each carbon dose was added to a 1-liter sample of groundwater collected at the site and the slurry was agitated for approximately 4 hours and then were allowed to settle for approximately 45 hours. Samples of supernatant were extracted using a syringe and analyzed for the remaining organic contaminants. Details of the testing procedure are provided in the Water Treatability Testing Plan. Analytical results for the treatability tests are given in Tables B2-7 and B2-8.

These data for the five compounds listed above were used to develop adsorption isotherms according to the Fruendlich equation. The data were fitted to the logarithmic form of the equation which is written as follows:

log x/m = log K + 1/n log Cf

x = mass adsorbed, mg

Cf = final water concentration, mg/l



m = mass of GAC, g K = intercept (Cf = 1) 1/n = slope

Isotherms for the five parameters which had detectable concentrations for all carbon doses and the data used to construct them are included in Appendix D, Volume 4 (Figures D-1 through D-10). Parameters derived from the isotherms are useful for evaluating whether a compound is amenable to adsorption by activated carbon and also can provide preliminary estimates of carbon usage. The Fruendlich constants are K equal to the value of x/m when Cf = 1, and 1/n equal to the slope of the isotherm best-fit line. A surmnary of these isotherm parameters for the ten isotherms developed is presented in Table B3-1. Inspection of Table B3-1 shows that, for each compound evaluated, the Calgon Filtersorb 300 activated carbon performed better than the Cameron Yakima CC activated carbon. However, the data collected for the treatability studies has considerable scatter. R squared values for the regression analyses of the isotherm data range from 0.596 to 0.912.

B3.2 AIR STRIPPER ANALYSIS

The use of an air stripper in treating the groundwater at this site is analyzed in this

section. The conceptual design basis developed in Section B5-1 serves as input to

computer programs used to model the performance of various air stripper designs and

vapor phase granular activated carbon (GAC) for control of air emissions.

B3.2.1 Design Basis

A design basis is developed for the groundwater treatment in Table B5-1 of Section B5.1. This table includes the groundwater extraction rate and concentrations of organic compounds in the extracted groundwater. Anticipated treatment criteria which the groundwater treatment system effluent must satisfy are also included in Table B5-1.



B322 Air Stripper Performance Modeling

Treatment by air stripping is achieved by pumping the contaminated water to the top of a tower filled with a high surface area packing media. The water flows down through the tower wetting the surface of the packing media. A blower is used to force air up through the tower countercurrent to the water flow. Volatile organic compounds (VOCs) vaporize (are stripped) from the water into the air. The treated water is withdrawn from the bottom of the tower. The air is discharged to the atmosphere or further treated to control the emission of VOCs. The effectiveness of air stripping in removing any particular contaminant from water is dependent on the contaminant volatility. The volatility is expressed as the Henry's constant which is the ratio of the vapor partial pressure to concentration in water at equilibrium at low concentrations. The performance of an air stripper tower design is dependent on the packing media used, the tower diameter and height of packing media, and the ratio of air to water flow rates.

The theory of mass transfer from liquid to gas in a countercurrent flow packed tower is

well developed. The basic design equation which relates compound properties and tower

design parameters to the reductions in water concentrations is:

Z = HTU X NTU

Z = Height of Packing Media in the Tower

HTU = Height of One Mass Transfer Unit

NTU = Number of Transfer Units

The NTU group in this equation expresses the reduction in concentration and is a function of the water concentrations before and after treatment, the Hemy's constant, and the ratio of air to water flow in the tower:

NTU = [S/(S-l)]xln([(CjC^)(S-l)+l]/S)

The factor S is the stripping factor and is equal to the ratio of air to water volume flow

rate in the tower multiplied by the Henry's constant.



The HTU group expresses the rate of mass transfer and is a function of compound properties, air and water flow rates, and packing media properties.

HTU = L/(KLa)

L = Water Flow Rate per Unit Cross-Sectional Area of the Tower KL = Overall Liquid Phase Mass Transfer Coefficient a = Water-Air Interfacial Area for Mass Transfer per Unit Volume of

Packing Media

There are a number of model equations which have been developed to relate the factor Kĵ a to measurable properties. The equations developed by Onda have been found to be the most useful for predicting the performance of an air stripper in treatment of low concentrations of VOCs (Roberts 1985; Wallman 1986; Reucroft 1971). The Onda equations account for the resistance to mass transfer in the water and air phases and have been found to provide a conservative estimate for air stripper performance.

Typically when an air stripper is applied for treatment of groundwater, the untreated water contains low concentrations of a number of different VOCs. The equations discussed above must be applied to each individual VOC present to estimate the height of packing that will result in the reduction in concentration required to meet the treatment criteria for that compound. In general, there will be a single VOC for which the estimated packing height is the largest. That VOC is the critical compound for the design and the air stripper must be designed on the basis of the results for that compound.

The performance analysis for an air stripper was conducted using a computer program

(JASP) developed by WCC. This program uses the model equations discussed above

including the Onda equations to predict the performance of air stripper designs. The

computer program includes a data base of physical properties for VOCs including

molecular weights, values of Henry's constants, and diffusion coefficients in air and water

that are required for the model equations. These data were obtained from technical

publications and/or using established correlations for estimation of physical properties.

The program also includes a data base of packing media properties for a number of


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commercial products. The data includes surface area per unit volume and the packing factor for use in pressure loss estimation. These data were obtained from technical publications or vendors of packing media. The computer program operates to provide a design for an air stripper tower based on the following input data: water flow rate, water temperature, air-to-water ratio, packing type and size, concentrations of VOCs in the inlet water, treatment criteria for the VOCs present, and specified pressure loss for air flow per unit height of packing. The program will conduct simultaneous calculations for up to 15 VOCs, identify the critical VOC, and provide the estimated tower design parameters based on this critical VOC. The program specifies the tower packed height, tower diameter, air flow rate, and predicts the concentrations of all VOCs in the effluent water and the air discharge from the tower.

There are a number of different factors to consider in design of an air stripper including selection of the type and size of packing media, the selection of the air-to-water ratio for operation, and selection of the air flow pressure loss per unit height of packing and water loading rate (volume flow rate of water per tower cross-sectional area). The last two factors will establish the tower diameter. The selection of packing media is considered first in the analysis in this report. The selection of the air-to-water ratio is considered next. The selection of pressure loss and water loading rates is based on typical air stripper designs.

The design basis in Table B5-1 is used for the air stripper performance analysis.

Table B5-1 includes volatile and semi-volatile organic compounds. Semi-volatile

compounds are not included in the analysis since, with few exceptions, the magnitude of

the Henry's constant for these compounds is such that treatment by air stripping is not

effective. The concentrations in the untreated water for all of the semi-volatile

compounds are below the respective treatment criteria and inclusion in the analysis

would not impact the results. The volatile compounds acetone and 2-butanone are not

included in the analysis since these compounds are also not effectively treated in an air

stripper due to their solubility in water. Those compounds having both concentrations

before treatment less than 10 ug/l and no treatment criteria and those compounds

having concentrations before treatment both less than 10 ug/l and less than their

treatment criteria are not included since this also does not impact the results. The

following compounds are included: benzene, chloroform, chloroethane, 1,1



dichloroethane, 1,2-dichloroethene, ethylbenzene, methylene chloride, tetrachloroethene, toluene, 1,1,1-trichloroethane, trichloroethene, vinyl chloride, and xylenes. The treated effluent concentrations were set equal to 1/4 of the treatment criteria in Table B5-1 for the computer model runs. This reflects a safety factor in the design to be sure the effluent criteria will not be exceeded.

B3.2.2.1 Analysis of Packing Media

Three different packing media are analyzed: Jaeger Tri-Packs, Intalox saddles, and Raschig rings. A pressure loss for air flow of 1/4-inch per foot of packing height is selected as typical for air stripper tower design. Excessive pressure loss can lead to poor liquid distribution or tower flooding and a high pressure loss greatly increases the air blower power requirements. A maximum liquid loading rate of 22 gpm/ft^ (15 kg/m^-s) is specified in the computer program to avoid problems with poor air distribution and to stay with in the range of liquid loading rates for which the model equations apply. A "rule-of-thumb" for packed tower design is that the diameter of the packing media should be less than 1/10 of the tower diameter. The range of tower diameters in this analysis is within 30 to 40 inches and so 2-inch packing size is used. An air-to-water volume ratio of 100 to 1 is used as typical of design for an air stripper for removal of VOCs from groundwater. The results of the computer calculations (included in Appendix E) are:

Tower Diameter Packing Height Packing Media (feet) (feet)

2" Jaeger Tri-Packs 2.75 25.4

2" Intalox saddles 2.85 31.1

2" Raschig rings 3.78 26.1

The critical compound identified for all three runs is trichloroethene based on the required reduction in concentration from 950 ug/l to 1.25 ug/l (1/4 x the treatment criteria of 5 ug/l). The Jaeger Tri-Packs required the smallest tower diameter and the shortest height of packing. The Intalox saddles tower diameter was close to that for the Tri-Packs but required an additional 5.7 feet of packing height. The Raschig rings have


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less void space than the other two packing materials and so required a significantly

larger diameter to avoid excessive pressure loss. The height of packing was still more

than that required for the Tri-Packs. All subsequent performance analysis is conducted

using 2-inch Jaeger Tri-Packs.

B3.2.2.2 Analysis of Air-to-Water Ratio

The effect of the ratio of air to water flow in the tower on the air stripper design were analyzed. Air-to-water volume ratios of 25,50,1(X), and 150 to one were evaluated. The packing media selected is 2" Jaeger Tri-Packs and an air flow pressure loss of 1/4-inch water per foot of packing is selected. The results of the computer model runs (Appendix E) are:

Air/Water Tower Diameter (feet) Packing Height (feet)

150 3.02 23.6 100 2.74 25.4 50 2.74 27.6 25 2J4 322

The results for height of packing are also presented in Figure B3-1. Trichloroethene was

again identified as the critical compound for all of these runs.

The trend observed in Figure B3-1 is typical with the tower packing height increasing as

the air-to-water ratio is decreased. At some point the height begins to increase rapidly

with decreasing air-to-water ratio. The exact nature of the curve is dependent on the

critical compound identified. The optimum design will balance the capital and operating

costs to give the lowest present worth for the project. A larger tower increases the initial

capital cost while higher air-to-water ratios result in increased power use for the air

blower resulting in increased operating costs. The optimum for any project will depend

on a number of assumptions including the unit cost for power, project duration, and the

discount rate for future operation costs. In general, the total present worth is not a

sensitive function of the air-to-water ratio over a broad range and an air-to-water ratio

between 25 to 200 will be cost effective depending on project specific conditions



(Wallman 1986; Hand 1986; Morton 1984). This analysis wiU be dramatically different when the emissions from the air stripper must be controlled as will be shown.

B3.2.3 Air Emission Control Analysis

The ROD for this site specifies that the groundwater treatment system will consist of an air stripper system followed by a polishing treatment for water using GAC and that the emissions from the air stripper will be controlled using GAC. The design criteria for the use of GAC to control air emissions are analyzed in this section.

The control of emissions from an air stripper uses fuced beds of GAC on the air exhaust from the air stripper tower. The GAC adsorbs the VOCs as the air passes through the bed. The capacity of the GAC to adsorb the VOCs eventually becomes exhausted at which point the GAC must be regenerated or replaced. The spent GAC can be removed and sent to the vendor off-site for regeneration in a furnace. The GAC can also be regenerated in place using steam or hot gas. There is data to suggest that in place regeneration is not effective for GAC beds used to control emissions from air stripper towers used in groundwater remediation (Crittenden 1988). The selection for off-site regeneration or on-site regeneration should be based on an economic analysis, generally the high capital costs for on-site regeneration equipment is only justified for large systems (Blaney 1988).

The adsorption of VOCs onto GAC from an air stream containing a mixture of VOCs

is a complex phenomena. Each VOC will have a different affinity for adsorption and

the theoretical adsorption capacity will increase as the concentration of the VOC in the

air increases. The various VOCs compete for adsorption sites and the VOC with the

lowest affinity for adsorption will generally be the first to break through the GAC bed

and be detected in the effluent air stream. The VOC adsorption is also impacted by the

relative humidity of the air stream. The capacity for adsorption is significantly reduced

when the humidity exceeds 50 percent (Reucroft 1971). The air exhaust from an air

stripper tower will be at approximately 100 percent humidity. Heaters have been used

to increase the air temperature and in this reduce the relative humidity prior to the

GAC beds (Crittenden 1988; Blaney 1988). A theoretical model has been developed to

predict the equilibrium adsorption capacity for adsorption of individual VOCs from dry



air (Reucroft 1971). This model relates the equilibrium loading (mg VOC/g GAC) to

the concentration of VOC in the air. This model was used to prepare a computer

program for estimating the equilibrium adsorption capacity of vapor GAC in the

presence of dilute concentrations of WOCs in air. The form of the model used in the

computer program is:

bi(q) = ln(pW„)-B(e/a)^

Where:

q = grams VOC adsorbed per gram of GAC

p = density of liquid VOC, g/cm' e = RT In(PVP) a = [(n'-l)M]/[(n' + 2)p] R = ideal gas constant, 1.987 cal/gmole-K T = adsorption temperature (absolute), K P' = saturation vapor pressure for VOC at temperature of adsorption, psia P = partial pressure of VOC in air, psia n = index of refraction for liquid VOC M = molecular weight for VOC, g/gmole

The factors W^ and B are constants related to the physical properties of the GAC

adsorbent and must be measured experimentally. The values reported for Calgon

Carbon Corporation type BPL GAC used in this program are (Reucroft 1971):

W„ = 0.46 cmVg

B = 3.22x10' cmVcal^

The model is only theoretical and the agreement between model predictions and the

actual equilibrium adsorption capacities will depend on the exact nature of the GAC

used. However, the model has been demonstrated to yield results of the correct order

of-magnitude and to correctly predict the qualitative variation of adsorption with

temperature and VOC concentration in air. The computer program includes a data base



of the necessary physical properties of VOCIs and provides an estimate of equilibrium loading when the compound concentration in air and air temperature are input.

The model discussed above was developed for the adsorption of a single VOC from air. The use of GAC to control emissions from an air stripper involves the simultaneous adsorption of a number of VOC present in the air stripper exhaust. The various VOCs present will compete for adsorption sites and so the actual equiUbrium loading for any VOC will be reduced. The computer program allows for up to 15 VOCs in the air stream and calculates the daily estimated total GAC requirement based on equilibrium loading by two methods. In the first method the one compound having the lowest equilibrium loading is established and the daily GAC requirement is estimated based on this equilibrium loading and the daily quantity of this one compound to be adsorbed. The quantity to be adsorbed is calculated from the air flow rate and the compound concentration in the air. This method provides lower limit for daily GAC use since it assumes that the presence of other VOCs will not increase the daily GAC requirement (total co-adsorption case). The second method uses the same procedure to separately predict the daily GAC requirement for each of the VOCs present and sums these numbers to give a upper limit estimate (no co-adsorption case).

The estimated air stripper emissions calculated for the use of 2-inch Jaeger Tri-Packs

at various air-to-water ratios are used to estimate daily GAC use for emission control.

Air exhaust from the air stripper tower would be at 55 F and it is assumed that the air

would be heated to 75 F (297 K) to reduce the relative humidity to less than 50 percent

prior to the vapor GAC. The estimated GAC use for the complete co-adsorption and

no co-adsorption calculations (Appendix E) are averaged to give the results presented

in Figure B3-2. The high estimated rate of GAC use is principally due to significant

concentrations in the air of two compounds, vinyl chloride and chloroethane, which have

high vapor pressures and hence very low equilibrium adsorption capacity. This is

illustrated in Figure B3-3 which presents results where these two compounds are

excluded from the calculations. The trend illustrated is the same in each case, however.

The daily GAC requirement declines rapidly as the air-to-water ratio is reduced. This

is due to the increase in air stripper exhaust concentrations with decreasing air-to-water

ratio. This results from removal of the same mass of VOCs at lower air flow rate. The

cost for installation and operation of the air heater will also be less at lower air-to-water

89MC114J-9/APXB-DAV.V-3/ACX)E5 B3-11 10-21-93


ratios as a reduced mass of air must be heated. The cost for installation of GAC beds for emission control will be a significant factor in the total capital cost and the cost for GAC replacement and regeneration is likely to be the largest non-labor operating cost. These factors suggest that an air stripper design which uses a low air-to-water ratio will be the most economical.



B4.0 REGULATORY ISSUES

A discussion of the regulatory issues associated with the operation of a groundwater treatment facility is included in this section.

B4.1 ARAR IDENTIFICATION AND VERIFICATION

As presented in the FS (CDM 1986), a granular activated carbon system will be used to adsorb the organic compounds and metals remaining after air stripping. The spent activated carbon would be considered a sludge as it is a solid or semi-solid waste generated as a pollution control residue (40 CFR 260.10). The spent-activated carbon could be regenerated, which is considered a reclamation process. Non-listed sludges that are reclaimed are not hazardous wastes even if they exhibit a characteristic of a hazardous waste, provided they are not being accumulated speculatively or the product of reclamation is not used in a maimer constituting disposal or burned as a fuel (40 CFR 261.2(c)(3)). As these exceptions do not apply, the non-listed spent-activated carbon is not a hazardous waste and is not subject to regulation under RCRA as long as it can be (and is) reclaimed. However, once the spent carbon becomes more waste-like than product-like, it will be considered a solid waste and subject to RCRA Subtitle C management and disposal regulations if it is hazardous.

If the spent carbon is derived from a listed waste, it would be considered a listed hazardous waste and must be managed in accordance with the hazardous waste generator, transporter, and storage provisions under RCRA from its point of generation throughout the recycling process and subsequent disposal. If the groundwater to be treated does not contain any listed wastes, as defined by RCRA, the residuals from treatment, including spent GAC, should not be listed wastes.



B4.2 NPDES REQUIREMENTS

The Clean Water Act (CWA) requires all direct discharges from a point source to meet technology-based requirements. The National Pollutant Discharge Elimination (NPDES) program is the national program for issuing, monitoring, and enforcing permits for direct discharges (40 CFR Parts 122-125). NPDES permits contain applicable effluent standards (i.e., technology-based and/or water-quality-based), monitoring requirements, and standard and special conditions for discharge. The NPDES program is administered by EPA and by state agencies authorized by EPA to administer a state program equivalent to the federal program. Rhode Island is authorized to administer the NPDES program.

On-site discharges from CERCLA sites are required to meet the substantive CWA NPDES requirements, including discharge limitations, monitoring requirements, and best management practices. These substantive requirements must be identified and complied with even though an NPDES permit will not be obtained.

CERCLA site wastewater treatment technologies are required to meet best control technology (BCr)/best available technology (BAT) requirements. BAT is the major national method of controlling the direct discharge of toxic and non-conventional pollutants into waters of the United States. Effluent limitations achieved through application of BAT represent the best economically achievable performance within an industrial category or subcategory. BCT is the level of technology control developed for conventional pollutants. Due to a lack of national effluent limitations guidelines for CERCLA site wastewater discharges, technology-based effluent limitations have to be imposed on a case-by-case basis. As described in the Record of Decision (ROD) for the site treated groundwater will be used to further flush contaminants from the soil. Effluent concentrations in the treated groundwater will have to comply with the Safe Drinking Water Act (SDWA) requirements or the Rhode Island Pollutant Discharge Elimination System (RIPDES) requirements dependent on whether the treated groundwater is discharged to the groundwater or to the surface water. A list of the limits established by the SDWA for discharging to the groundwater can be found in Table B4-1. Note that secondary drinking water standards are "To-Be-Considered," rather than ARARs, since the secondary standards are non-enforceable.

89MC114J-9/APXB-DAV.V-3/ACOES B 4 - 2 10-21-93


The aquifer underlying the Davis site has been classified as a Class IIB aquifer following the Ground-Water Protection Strategy and Guidelines, and therefore will be cleaned up to potable quality. The target clean-up levels set by the EPA in the ROD were based on drinking water stzmdards and criteria, and require that remediation continue until the aquifer meets the MCLs of 5 ppb for benzene, trichloroethylene (TCE), and tetrachloroethylene (PCE) set by EPA under the Safe Drinking Water Act (SDWA).

B4.3 WASTE CHARACTERIZATION FOR SLUDGE DISPOSAL

The coagulation/precipitation process will generate a metal hydroxide sludge that will need to undergo the TCLP test to determine if it is a RCRA-characteristic hazardous waste. If it fails the TCLP test, it will be classified as a characteristic hazardous waste with the specific "D" codes for the hazardous constituents exceeding the TCLP limits. This waste would then need to meet the treatment standards dictated by the Land Disposal Restrictions (LDR) for the respective "D" wastes prior to being land disposed.

Sludge production test results for the TCLP metals test showed no exceedances of the TCLP metals limits. The sludges are, therefore, not considered characteristically hazardous due to their metal content. However, the concentrations of metals in the test water were very low. Additional tests during full scale operation will be required to demonstrate that the sludge is non-hazardous.

B4.4 AIR REGULATIONS ASSOCIATED WITH AIR STRIPPING

The groundwater treatment system calls for air stripping with carbon adsorption as an

effluent polishing process and will use activated carbon to treat the vapor phase effluent

from the air stripping towers. The Record of Decision (ROD) relates that emissions

from the air stripping towers will contain volatile organic compounds and must,

therefore, be in compliance with National Ambient Air Quality Standards (NAAQS) and

emission standards. The State of Rhode Island has developed Acceptable Ambient

Levels for approximately 40 pollutants that must be met. The emissions must also

comply with the State's Air Pollution Control Regulations ("RI Air Rules"). The ROD

did not list 40 CFR Part 52, the Prevention of Significant Deterioration program, nor the



New Source Performance Standards listed in 40 CFR Part 60 as ARARs, therefore these standards are assumed not applicable and will not be discussed.

According to the RI Air Rules, any stationary source which has an air pollution control system or appurtenances must comply with Rule No. 9 (Approval to Construct, Install, Modify, or Operate). "Stationary source" is defined in the RI Air Rules as "any building, structure, facility, or installation which emits or may emit any regulated air pollutant." "Facility" is defined as "all pollutant-emitting activities which belong to the same industrial grouping, are located on one or more contiguous or adjacent properties, and are under the control of the same person." Personnel at Rhode Island's Air and Hazardous Materials Division of the Department of Environmental Management (DEM) related that all operations at a Superfund site could be considered either a single source of emissions or as individual emissions sources (McVay 1992).

EPA has established NAAQS's which are applicable to all air emission sources (Table B4-2). States designate whether certain regions are attaiiunent or nonattaimnent areas for each of the parameters encompassed by the NAAQS. The Davis Waste Site is in an air quality nonattainment area for ozone (the entire state of Rhode Island does not meet the NAAQS standard for ozone). Facilities with the potential to emit 100 tons or more of volatile organic compounds per year and for which the State has determined its Growth Allowance will not be exceeded by the source's emissions are required by Rule No. 9 of the RI Air Rules to meet an emissions limitation that is considered the lowest achievable emission rate (LAER) for this source. This LAER would be based on technological factors and can be in the form of a numerical emissions standard or a design, operational, or equipment standard. If the State determines that the new source would cause the State's Growth Allowance to be exceeded, emission offsets may be required (described under Section B9.11 of the RI Air Rules).

The Davis Waste Site is in an attaiimient area for all NAAQS's except ozone.

Requirements concerning attaiimient areas under Rule No. 9 are considered applicable

only for major stationary sources (facilities which emit or have the potential to emit 250

tons per year or more of any regulated air pollutant) and require the application of best

available control technology (BACT) for each pollutant it has the potential to emit. Air

quality modeling (as part of its Air Quality Impact Analysis described under Section



B9.14 of the RI Air Rules) is required to demonstrate that emission increases from the proposed source would not cause or contribute to violation of any NAAQS or an increase in ambient concentrations exceeding the remaining available increment for the specified air contaminant.

Regulation No. 22 of the RI Air Rules regulates air toxics. If a source has the potential to increase emissions of listed air toxics by greater than the minimum quantity for any contaminant, the source must obtain an approved construction permit. The minimum quantities are Usted in Table B4-4. Chloroform, tetrachloroethene, and trichloroethene are expected to exceed these quantities based on the conceptual design for the air stripper (Table B5-2). Therefore, RI Regulation No. 22 will apply and the substantive requirements must be complied with. These requirements include demonstrating (in accordance with Rhode Island air modeUng guideline procedures) that emissions from the facility will not cause an increase in ground level concentration of a listed toxic air contaminant at or beyond the property line in exceedance of the Acceptable Ambient Air Levels (Table B4-3). If the facility is designed to achieve LAER, but the technology cannot meet the levels in Table B4-3, then the emissions from the facility must not cause an increase in ground level concentration at or beyond the property line in exceedance of the State's Acceptable Ambient Air Levels with LAER (Table B4-5). With adequate controls, this project will be in compliance with RI Air Rules.

Emissions from the air stripping towers must also comply with Rules No. 1, No. 7, and

No. 17 of the RI Air Rules. Visible emissions are limited under Rule No. 1 of the RI

Air Rules. No air contaminants from any source may be emitted into the atmosphere

for a period or periods aggregating more than three minutes in any one hour which is

greater than or equal to 20 percent opacity, unless such opacity is caused strictly by the

presence of uncombined water. Opacity is defined as the degree to which air

contaminants reduce the transmission of light and obscure a contrasting background.

Rule No. 7 prohibits the emission of any contaminant which, either alone or in

connection with other emissions, may be injurious to human, plant, or animal life, cause

damage to property, or unreasonably interfere with the enjoyment of life and property.

Emissions creating an objectionable odor beyond the property line are prohibited under

Regulation No. 17.



B5.0

APPLICABILITY TO FULL SCALE DESIGN

B5.1 DESIGN BASIS

The design was developed using the proposed extraction well locations and anticipated well yields described in Section B4.1 of the Pre-Design Engineering Report 11. The extraction wells are located in three clusters in this conceptual extraction system design: (1) five wells are located in the bedrock of the Northern and Southern Disposal Areas and the Western Access Road with an average maximum estimated extraction rate of 11 gpm per well; (2) four wells are located in the bedrock of the Pump Test Area with an average estimated maximum extraction rate of 11 gpm per well; (3) four wells are located in the overburden in and around the Northern and Southern Disposal Areas with an average estimated maximum extraction rate of 7.5 gpm per well. Therefore, the conservative total flow rate for the treatment system would be 130 gpm. Concentrations of contaminants obtained in previous sampling of groundwater monitoring wells located in the vicinity of each cluster of wells were used to prepare the estimate for maximum expected concentrations in the influent water. These are presented in Table B5-1. The maximum concentrations of organics and inorganics reported as part of the RI data and Pre-Design Activity data were used, and a weighted average was calculated based on the fraction of total flow arising from each location. The concentrations which were used to calculate the weighted average concentration are presented in Table B5-2.

The treatment criteria are drinking water standards. MCLs were used if available and

MCLGs were used when MCLs were not available. No treatment criteria are included

for constituents that do not have MCLs or MCLGs.

Data from the most recent investigation allows a conservative design basis to be

prepared. The data collected from the chemical analysis of groundwater from OW-51

(Table B2-1), appear to be considerably less than what may actually be treated during

full scale operation. Therefore, the contaminant concentrations of groundwater from

OW-51 were not used to develop the design basis.



B5.2 CHEMICAL PRECIPITATION DESIGN CONCEPT

The concentrations of inorganics, in particular iron and manganese, in Table B5-1 indicate that chemical precipitation will be necessary as a pretreatment to the organics removal system to prevent fouling of the air stripper and to achieve the clean up goals for the contaminants of concern. Although the water used in the treatability test did not contain inorganic concentrations as high as those estimated in the design basis, the treatability tests suggest that the metals can be reduced to acceptable levels using caustic precipitation. The initial step will be neutralization and pH adjustment of the water to approximately pH 10 with sodium hydroxide or lime. Sodium hydroxide would be preferred due to handling considerations and to minimize quantity of sludge produced. This step should adjust the Ph to a range where most of the metals will precipitate. FeS04 or a polymer flocculent could be added to coagulate solids and enhance suspended solids removal in the clarification step. With the conceptual design presented in Figure B5-1 to treat approximately 187,000 gpd, it is estimated that the full scale treatment system will require approximately 80 pounds of ferric sulfate and 160 pounds of caustic soda per day. Assuming that the sludge can be filter pressed to 30% solids, approximately 640 pounds per day will be produced. These quantities are approximate, and could vary widely based on the actual influent water analysis.

A polymer such as Superfloc 212, which was used in the treatability tests, could also be

added to aid in the suspended solids removal step. The Superfloc will increase the

particle size to promote quicker and better settling. However, it will also increase the

volume of sludge generated.

The clarified water will require further treatment and will be pumped to a Greensand

filter for further removal of manganese and suspended solids. Greensand filters are

commonly applied for removal of manganese from water and are capable of producing

lower concentrations of manganese than a conventual mixed media sand filter. A Ph

adjustment step will follow to neutralize the water prior to being pumped to the air

stripping system. This Ph adjustment will reduce the possibility for formation of

carbonate scale in the air stripper. Neutralization is also required prior to discharge of

the treated water. No precipitates or additional waste streams will be produced by

neutralization.



The sludge generated from the solids removal process will be pumped to a thickener tank where polymers will be added to aid in settling. Thickened sludge will be pumped to a filter press for dewatering and then disposal. The filtercake will require TCLP analysis to properly dispose of the material. The treatability tests provided data on the characteristics of the sludge that could typically be generated during pretreatment. These results indicate that the material should pass TCLP for metals. Additional analysis of the filter cake will be required at the full scale level to confirm characterization prior to landfill disposal. Filtrate from the thickening tank and filter press will be recycled back to the equalization tank. Greensand filter backwash water will also be recycled to this tank.

The pretreatment step is required in order to prevent plugging and decreased removal efficiency in the air stripper. Additionally, it is hkely that some of the precipitated iron would pass through the air stripper and plug the carbon filters. This would result in premature replacement of the carbon. Therefore, there is a definite need for pretreatment to significantly reduce the concentrations of these metals. Simple settling without chemical addition would not provide adequate removal efficiencies. The use of an inclined plate clarifier with addition of polymer flocculent is required to achieve reasonable operation of the subsequent filters. The Ph adjustment of the feed is required to produce adequate removal of manganese which does not precipitate at neutral Ph. Costs associated with pretreatment are presented in Appendix F.

B5J DIRECT CARBON ADSORPTION DESIGN CONCEPT

The design basis for direct treatment of organics removal is presented in Table B5-1.

Calgon provided an estimate of 68 pounds per thousand gallons treated (Appendix D).

Based on the carbon usage rate and groundwater flow of 130 gpm, WCC recommends

the Calgon Model 7.5 system (or equal) if carbon is selected. The Model 7.5 is a skid-

mounted assembly with two A.S.M.E. Code Absorbers which can be operated in series

or parallel. Each absorber holds 10,000 pounds of activated carbon. At 130 gpm, the

Model 7.5 will provide 20.2 minutes of contact time in each absorber at a pressure drop

of approximately 4 pounds per square inch (psi) when operated in series. At 130 gpm,

carbon usage will be approximately 13,000 pounds per day. At this rate, saturation of

the lead absorber is estimated to occur in less than 24 hours. GAC replacement at this



frequency would be impractical, and direct GAC treatment is not recommended as a viable option. However, under a service contract Calgon can provide change-out of the carbon at saturation. A specially equipped truck deUvers fresh carbon and removes the spent carbon in one on-site operation estimated to take 1 1/2 hours. Spent carbon is sent either to the Neville Island plant near Pittsburgh, Pennsylvania or the Big Sandy Plant near Ashland, Kentucky. There is a one-time spent carbon acceptance fee of $4,500.00 if the spent carbon is classified as a RCRA waste or $500.00 if non-RCRA. The adsorbate profile document is included in Appendix D, and is submitted along with a Carbon Acceptance Request and a sample of spent carbon to begin the carbon acceptance process. Details of the Model 7.5 absorber system, including specifications for the unit, are provided in Appendix D. The capital cost of the Model 7.5 including the first batch of carbon is $96,(X)0.(M). The cost of

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FINAL PRE-DESIGN ENGINEERING REPORT 2--VOLUME 3 OF 4 · FINAL PRE-DESIGN ENGINEERING REPORT H DAVIS LIQUID WASTE SITE SMTTHFIELD, RHODE ISLAND ... conducted a bench-scale treatability