This article was downloaded by: [McMaster University]On: 22 October 2014, At: 08:43Publisher: Taylor & FrancisInforma Ltd Registered in England and Wales Registered Number:1072954 Registered office: Mortimer House, 37-41 Mortimer Street,London W1T 3JH, UK

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Pilot‐scale devices forremediation of munitionscontaminated soilsM. Arienzo a , S.D. Comfort b , M. Zerkoune b

, Z. M. Li b & P. J. Shea ba Dipartimento di Scienze Chimico Agrarie ,Università degli Studi di Napoli , Federico II,Portici, Napoli, 80055, Italyb Institute of Agriculture and NaturalResources , Univ. of Nebraska , Lincoln, NE,68583–0915, USAPublished online: 15 Dec 2008.

To cite this article: M. Arienzo , S.D. Comfort , M. Zerkoune , Z. M.Li & P. J. Shea (1998) Pilot‐scale devices for remediation of munitionscontaminated soils, Journal of Environmental Science and Health, Part A:Toxic/Hazardous Substances and Environmental Engineering, 33:8, 1515-1531,DOI: 10.1080/10934529809376803

To link to this article: http://dx.doi.org/10.1080/10934529809376803

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J. ENVIRON. SCI. HEALTH, A33(8), 1515-1531 (1998)

PILOT-SCALE DEVICES FOR REMEDIATION OF MUNITIONSCONTAMINATED SOILS

Key Words: Soil remediation, TNT, biorector, Fenton reagent

M. Arienzo1, S.D. Comfort2, M. Zerkoune2, Z. M. Li2 and P. J. Shea2

1Dipartimento di Scienze Chimico Agrarie, Università degli Studi di NapoliFederico II, 80055 Portici, Napoli, Italy.

2 Institute of Agriculture and Natural Resources, Univ. of Nebraska, Lincoln, NE68583-0915, USA.

ABSTRACT

An equipment is described for the remediation of (TNT) contaminated soil in

pilot scale setting. Devices were developed for the preparation of soil samples and

for the removal of water from soil after treatment of a soil slurry in a 60 L air-lift

reactor, which was a prototype of larger commercial unit. The method was applied to

clean up TNT-polluted soil using Fenton reagent (H2O2+ Fe2+) as remedial

technology. Pilot scale results were compared to those obtained at bench scale level.

Laboratory scale experiments showed that 1% H2O2 + 640 mg Fe2+ L-1 reduced

TNT concentration from 400 mg kg-1 to about 50 mg kg-1, which was above the

Nebraska Ordnance Plant's cleanup goal (17.2 mg TNT kg-1). Adding the reagent

incrementally rather than in a single dose was more effective in reducing TNT

concentration at both bench and pilot scale. Faster removal of TNT was obtained in

1515

Copyright © 1998 by Marcel Dekker, Inc. www.dekker.com

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1516 ARIENZOETAL.

the pilot reactor: TNT concentration fell within 24 h below the clean-up goal and

less cumulative amount of H2O2 (0.625%) was required. The designed sieve size

device provided reliable and rapid screening of contaminated soil to a sieve size (1

mm) optimal for reactor performance. The vacuum filter effectively separated water

and soil from soil slurry, reducing handling and processing of primary residuals.

INTRODUCTION

A serious problem facing the Department of Defense and the EPA is the presence

of TNT-contaminated soils at facilities where munitions were formerly

manufactured, loaded, or demilitarized (Jerkins, 1992). Past disposal practices

conducted at the former Nebraska Ordnance Plant (Mead, NE) have left the state

with approximately 6,400 m3 of contaminated soil. Drainage ditches contain solid-

phase (precipitated) munitions, resulting in soil solution concentrations at near TNT

solubility limits (Comfort et al., 1995). This is a concern for state and local officials

since several munitions compounds and, in some cases, their reduction products

have been found in surface and groundwater in the vicinity of munitions plants

(Periera et al., 1976). Some of these nitroaromatic and nitramines are known to be

mutagenic (Won et al., 1974; Won and Disalvo, 1976), carcinogenic, or otherwise

toxic to aquatic and terrestrial organisms (McCormick et al., 1976; Smock et al.,

1976; Kaplan and Kaplan, 1982). Incineration was recently recommended for 6,400

m3 of contaminated soil at the NOP with an estimated cleanup cost of more than 14

million dollars. Although incineration effectively destroys munitions residues, it

is expensive, produces an unusable ash byproduct and has been met with public

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DEVICES FOR REMEDIATION OF CONTAMINATED SOILS 1517

resistance. Alternative and more publicly acceptable methods of remediation are

needed. Chemical treatments like the use of hydrogen peroxide with iron salts

(Fenton reagent) offer faster and more consistent degradation rates over

bioremediation. Fenton' s reagent has been primarily studied at the laboratory scale

level with limited applications in the field, where the technology is effective in on-

site treatment applications (e.g. slurry reactor) (Venkadatri and Peters, 1995). Our

previous bench research (Li et al., 1997) indicated that Fenton's reagent effectively

destroyed TNT in a pure water system and soil slurry. In order to successfully scale

up to field application the remedial technology it was considered necessary to test

the effectiveness of Fenton oxidation in pilot scale setting. However, the pilot scale

approach in remediation research is not frequent because of the specific

instrumentation and methodologies required. The major difficulty of this approach is

to design convenient equipment simulating larger commercial units capable of

managing large amounts of contaminated soil and water under conditions that would

be encountered in the field.

The intent of this research was to describe a method and the devices, some of

them developed and designed by the authors, for preparation, treatment and

dewatering of TNT-contaminated soil from the NOP site. The design and analysis of

a pilot study will be presented in the following sections describing the proposed

technique. In the assay of the methodology and devices developed, the efficiency of

the classical Fenton reaction to remediate TNT contaminated soil was studied and

compared at both laboratory and pilot scale level.

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1518 ARIENZO ET AL.

MATERIALS AND METHODS

Soil

The soil, a Sharpsburg silty clay loam (20 % sand, 44 % silt, 36 % clay and 1.9 %

OC, pH 7.5) was obtained by mixing the first 120 cm of soil from the NOP.

Continuous cores taken to 330 cm indicated that the bulk of soil contamination still

remains near the soil surface. The recorded decision for this site stipulates removal

and incineration of the top 120 cm. The resulting average concentration of TNT was

400 mg kg"1 (Figure 1).

Bench Scale Experiments

Slurries (1:5 w/v soil:water) of TNT contaminated soil were prepared in 30 ml

Teflon centrifuge tubes, acidified at pH 3.0 with 0.5 N H2SO4 and treated with

Fenton reagent (1-2 % H2O2 + 80-250-500-1000-2000 mg Fe2+ L"1). Reagent was

added at 1, 4, and 8 increments at 4 h intervals. Slurries were agitated on an

oscillating shaker at 36 °C for 48 h. This temperature was controlled by placing

tubes inside an insulated case containing coils of circulating water connected to a

water bath.

The pilot scale plant consisted of three major sub-systems: (i) Soil sample

preparation, (ii) Soil slurry treatment, (iii) Soil dewatering.

Soil Sample Preparation

A soil sieving device manufactured by C.M.D. (Custom Machine Design, Inc.

Lincoln NE) was used to separate impervious and oversize material, such as rocks,

concrete and gravel (Figure 2). The sieving mechanism consisted of steel cylinders

(25 cm long; 20cmdiam.; 0.3 cm thick) where TNT air-dried contaminated soil

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DEVICES FOR REMEDIATION OF CONTAMINATED SOILS 1519

enE,c

cU

0 -U

É

40 80 2000 4000 6000-V/-\ 1 i I i

TNT

(0-120 cm)ï=440 mg TNT kg'1 -

FIGURE 1

Distribution of TNT in contaminated soil at the former Nebraska Ordnance Plant,Mead, NE. Bar widths delineate sampling depths.

9

L 1f

- H - x

ol//a)

FIGURE 2

a) Soil sieving device used to screen TNT contaminated soil; b) cylinders weremanufactured to sieve soil at 1 or 2 mm.

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1520 ARIENZO ET AL.

was ground and sieved at 1 mm. This was the optimal particle size dimension

for mixing and homogenizing soil with water inside the reactor, which was rated for

soil particles not exceeding 20 mesh (approx 1 mm). While one endcap of the

cylinder was welded, the other was removable for the introduction of the soil sample.

Soil inside the cylinder was ground by two solid steel bars (one 20.0 cm long, 2.0

cm wide, the other 20.0 cm long, 4.0 cm wide, weighing respectively 0.75 and 2.0

kg). Cylinders were supported by two rubber coated steel bars which, through a

transmission chain moved by a single phase motor of 0.5 HP, produced the rotation

of the bars together with the cylinders; this caused the bars to collide against

impervious and oversize material and the cylinder's walls, allowing sieving of soil

through the mesh. Each cylinder was located in a compartment delimited by a steel

cover in order to reduce dust dispersion and noise diffusion. A stainless steel cone,

height 20 cm, bottom light 7.5 cm, guided the ground soil into polyethylene

containers. The device was configured with three operating cylinders; each cylinder

was fed with 2 kg of air-dried soil which was treated for about 15 m. This

configuration allowed about 36 kg of soil per h to be treated, with soil sieved at 1

mm and a recovery of about 70-90% depending on the percentage of gravel present

in the sample. After screening, the soil was homogenized (cone and quartering) and

the initial TNT concentration was determined on 20 subsamples. Another set of

cylinders with a screen of 2 mm was used to sieve soil after dewatering, of the

treated slurry, before analysis of residual TNT concentration.

Soil Slurry Treatment

TNT contaminated soil (12 kg) was mixed with 60 L of hot tap water (20%

solids) in an EIMCO Biolift reactor (Figure 3) designed to simulate the operation of

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DEVICES FOR REMEDIATION OF CONTAMINATED SOILS 1521

1

a)

FIGURE 3

a) EIMCO air-lift 60 L reactor where TNT contaminated soil (500 mg TNT kg'1)was treated with Fenton Reagent; b) soil dewatering device.

a füll scale Biolift Reactor, the reactor mechanisms consisted of a central raking and

airlift devices to provide mixing and aeration. Oxygen was supplied by dissolving

compressed air in the slurry through bubble diffusere. The speed of the bottom rakes

and central impeller was set at 40 rpm in order to provide the optimum

homogenization of the slurry. The reactor was equipped with a heating device which

allowed the temperature of the slurry to be kept close to 34 °C.

Before the addition of chemical reagent, the soil slurry was equilibrated for 48 h

in the reactor at a temperature of 34 °C. The pH of the slurry was first adjusted to

3.0 with 60 mL of concentrated sulphuric acid. Then Fenton reagent was added in a

single batch addition, in four quarter or in 8 half quarter additions, monitoring pH

and temperature over the course of the experiment. Four samples consisting of 15

ml of slurry were collected after each addition of the reagent, at a 4 h interval, from

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1522 ARIENZO ET AL.

the middle port of the reactor during 48 h in 35 ml Teflon centrifuge tubes.

Experiments were conducted in a climate controlled room at 30 °C.

Soil Dewatering Device

Following chemical treatments, soil slurry was dewatered on a stainless steel

porous filter with a 2 u opening. The filter was assembled on a removable steel

frame and arranged on top of a stainless steel basin collecting the leachate (Figure 3).

A system of four levers, mounted on the top of the longest basin's walls, pressed

the filter frame against four rubber coated supporting bars connecting the two main

walls of the basin. A vacuum pump connected to the bottom end of the basin

provided constant suction of 15 kPa. This overall configuration allowed air tight

conditions and optimum filtration conditions.

After 48 h on the filter, the soil, in the form of a soft sludge-cake, was removed

from the filter, air dried, sieved at 2 mm and subsampled for analysis of TNT

residues. This was to verify whether the clean-up level was below the required

standard (USEPA remediation goal forNOP is 17.2 mg kg"1). The leachate (about 12

L) was removed from the device through an eluant delivery tube and effluent

fractions were analyzed for TNT by high performance liquid chromatography

(HPLC).

TNT Analysis

At each sampling time, TNT was extracted from the soil slurry with 15 ml of

acetonitrile in 30 ml Teflon tubes, which were sonicated for 18 h at 30 °C. TNT

concentration was determined by HPLC with a Keystone Betasil NA column

(Keystone Scientific Inc. Bellefonte, PA) using an isocratic mixture of CH3OH-H2O

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DEVICES FOR REMEDIATION OF CONTAMINATED SOILS 1523

(55:45) at a flow rate of 1.0 mL min'1. TNT was detected spectrophotometrically at

254 nm and quantified by comparison to high purity standards.

RESULTS AND DISCUSSION

Bench Scale Experiments

Figure 4 shows the effect of pH, temperature and pre-equilibration time on the

extent of TNT oxidation by Fenton reagent. Soil slurry pH greatly affected TNT

degradation, TNT destruction being more significant at pH 3.0 than at 6.5 (50 mg

TNT kg'1 vs. 150). Such observations were consistent with previous reports

regarding the effect of pH on Fenton oxidation of organic pollutants (Sedlak and

Andren, 1991). Fenton's reagent has been shown to be most effective at a pH

between 2 to 4 (Watts et al., 1993); this avoids Fe3+ precipitation to hydrous ferric

oxide at pH above 3.5. Raising the temperature of the soil slurry to 36 °C increased

the overall destruction of TNT by Fenton reagent. High temperatures, facilitating

dissolution of solid-phase TNT, promote oxidation of TNT in the aqueous phase

where hydroxyl radicals are produced. Preequilibration time of the contaminated

soil with water did not affect the effectiveness of Fenton's reagent (Figure 4). No

significant TNT destruction was observed on adding the reagent 0.5 or 24 h after

creating the aqueous slurry by combining contaminated soil with tap water, even at

higher peroxide dosage (2 %). This offers a cospicuous reduction of the times of

soil decontamination process. In our experiments, the use of 2 % H2O2 was

motivated by the fact that Fenton treatment in soil is carried out by using a large

excess of H2O2 over Fe2+ (Pignatello and Day, 1996) because of oxidant

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1524 ARIENZO ET AL.

66X

toE

hÜ

X)

0ciu

w

FIGURE 4

Effect of pH, temperature and pre-equilibration time of soil slurry before one stepaddition of Fenton Reagent (1-2 % H2O2 + 640 mg Fe2+ L"1).

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DEVICES FOR REMEDIATION OF CONTAMINATED SOILS 1525

consumption by soil components. Under such conditions, Fe2+ is instantly oxidized

to Fe3+ and a further reaction can take place under Fe3+-catalytic conditions in which

Fe is cycled between the +n and +ÜI oxidation state (Pignatello and Day, 1996).

However, high concentrations of peroxide and complete degradation of the

contaminant may not be economically efficient due to the high cost of hydrogen

peroxide, which represents the primary cost of Fenton reagent ($1.72/gallon for 50%

aqueous solution).

Figure 5 shows the extent of TNT destruction by adding 1 % H2O2 and different

amount of Fe2+ in 1-4-8 increments at 4 h intervals within 48 h. The data indicated

that TNT destruction increased with the order of dilution of Fenton reagent (1-4-8

increments) and with [Fe2+], but levelled off above 1000 mg Fe2+ L"1. One step

addition proved the least effective treatment; adding the reagent in one solution

could have increased the scavenging of OH» by reaction with another Fe2+, unless

Fe2+ is kept low by gradual addition in diluted form. Moreover, an additional

mechanism for OH» scavenging is represented by the reaction: OH» + H2O2 —> H2O

+ HO2», where HÜ2» is the hydroxyl radical. Compared to OH», HO2» is much less

reactive (Bielski et al., 1985) and its conjugate base O2*" (pKa, 4.8) is practically

unreactive as a free radical (Frimer et al., 1988. Diluting 500 mg Fe2+ L'1 and 1 %

H2O2 over 8 doses reduced the CHsCN-extractable TNT concentration from 500 mg

TNT kg'1 to about 50 mg kg"1 within 36 h, respect to 75 mg TNT kg*1 of the single

dose treatment However, the remediation goal, 17.2 mg kg"1, was not achieved in

any of the treatments tested. In order to promote the widespread usage of Fenton

reagent as a soil decontamination technology it was considered important to keep

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1526 ARIENZO ET AL.

250

OX)

200

ion

rat

• • •

Con

«TN

T

150

100

50

0

lj

• One step H 4 step CU 8 step

•180 250 500 1000 2000

FIGURE 5

Destruction of TNT with Fenton's Reagent ( 1 % H J O 2 +80-250-500-1000-2000 mg2+ 1e2+ L"1Fe2+ L"1) added at 1, 4, 8 h increments at 4 h intervals. Initial temperature was 36

low the requirement for ferrous iron. This avoids the production of a sludge

containing excessive amount of iron, which requires proper disposal. The treatment

with 8 additions of 1 % H2O2 + 640 mg Fe2+ L"1 over 36 h was chosen for the pilot

scale approach.

Pilot Scale Reactor

Destruction kinetics, shown in Figure 6, indicated faster overall removal of TNT

in the pilot reactor. TNT concentration, at 24 h, was about 12

mg kg"1 respect to 50 mg kg'1 at bench scale. The oxidation of TNT, after that time,

continued in the reactor, TNT concentration being 8.7 mg kg"1 at 36 h. With respect

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DEVICES FOR REMEDIATION OF CONTAMINATED SOILS 1527

500

450"•"Bench scale

* Pilot scale

12 16

Time

FIGURE

20

(h)

6

24 28 32 36

Destruction kinetics of TNT at bench and pilot scale. Fenton reagent ( 1 % H2O2 +640 mg Fe2+ L"1) was added in 8 diluted doses every 4 h.

to the bench scale only 5 additions of peroxide, corresponding to a cumulative

amount of 0.625 % H2O2, were required to reach the clean-up goal. Temperature and

pH were easily monitored over the course of the experiment in the pilot reactor. No

soil pH adjustment was required during the reaction, pH being constantly close to the

initial set value of 3.0. This indicated that the soil buffering capacity did not affect

the soil slurry reaction. However, studies at the bench scale (Pignatello and Baehr,

1994), showed that the acid neutralizing capacity of soils may be particularly

important in determining the potential efficacy of Fenton's reagent treatment for

immobilized contaminants.

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1528 ARIENZO ET AL.

During the treatment (Figure 7) the temperature reached a maximum of 39 °C at 8

h from the first addition of the reagent, due to the exothermic decomposition of

peroxide, and then decreased to 33 °C at 48 h, that is very close to the maximum

value (34 °C) allowed by the pilot heating device during initial equilibration of the

soil slurry. These data indicated that whereas the temperature of the slurry was

allowed to increase in the reactor producing even more favorable oxidation

conditions, temperature in the bench scale experiments was kept constant (36 °C)

throughout the reaction by the water bath. The higher temperature observed in the

pilot reactor could have also increased the availability of Fe in the soil slurry, thus

making more TNT oxidized.

The bio-reactor after 48 h was emptied and soil slurry poured on the vacuum

filter. The two main end products resulted in leachate and soil which accumulated

in the form of a sludge cake on top of the filter. After drying, the soil showed a TNT

concentration very close to that found immediately before emptying the reactor. In

fact, when the soil slurry was treated with 4 x (0.250 % H2O2 + 160 mgL'1), TNT

concentration of filtered dry soil was 22.7 vs 32.8 mg kg'1 of unfiltered soil. This

demonstrated a limited loss of soil particles, which could associate TNT, through

the filter screen. Scant presence of TNT (< 2 mg L'1) was found in the leachate. In a

full scale treatment plant, water could be recycled to feed the reactor, whereas soil

could be returned to the site as backfill.

The proposed pilot scale system, could be applied to evaluate the effectiveness of

other innovative technologies that have already been approved in the conceptual

stage or tested at the laboratory level. Our remedial scheme provided proper

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DEVICES FOR REMEDIATION OF CONTAMINATED SOILS 1529

FIGURE 7

Temperature variation of soil slurry in the pilot reactor during the treatment withthe Fenton reagent.

perspectives to maximize clean-up efficiency of Fenton reagent. Intermittent

injections of low concentration of Fenton reagent sustained high oxidation potential

inside the pilot reactor. Transformation and removal of TNT in the pilot system

occurred at a faster rate and required less peroxide than the bench scale approach to

reach the remediation goal of 17.2 mg kg'1. Devices designed to assist the operating

of a soil slurry reactor effectively reduce pre-post processing of waste, providing

easy sizing of materials prior to putting them in the reactor, and proper dewatenng of

soil slurry.

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1530 ARIENZO ET AL.

ACKNOWLEDGMENTS

Appreciation is expressed to the National Water Research Institute (NWRI), the

University of Nebraska Water Center/Environmental Programs (WC/EP) and

NSF/EPSCoR cooperative agreement EPS-9255 225. The first author is grateful for

the postdoctoral fellowship granted by the Organization for Economic Cooperation

and Development (OECD), theme 4, "Surface and Groundwater Quality and

Agricultural Practices", that allowed him to participate to this work.

REFERENCES

Bielski B. H. J., Cabelli D. E, Arudi R. L., Ross A. B., J. Phys. Chem. Ref. Data,14:1041-1100(1985).

Comfort, S. D., Shea P. J., Hundal, L. S., Li Z , Woodburry B. L., Martin J. L.,Powers W., J. Environ. Qual, 24:1174-1182 (1995).

Frimer A. A. "Oxygen radicals in Biology and medicine" Plenum Press, New York(1988), pp 29-38.

Jenkins, T.F. Walsh M. E., Talanta, 39:419-428 (1992).

Kaplan, D. L., and Kaplan A. M., Environ. Sci. Technol., 16:566-571 (1982).

Li, Z. M., Comfort S. D., Shea P. J. J. Environ. Qual., 26:480-487 (1997).

McCormick, N. J., Feeherry F. E., Levinson H. S., Appl. Environ. Microbiol,31:949-958 (1976).

Periera, W. E., Short D. L., Manigold D. B., Roscio P. K. Bull. Contam. Toxicol.,21:554-560(1976).

Pignatello J., Baehr K., J. Environ. Qual., 23:365-370 (1994).

Pignatello J., Day M., Hazardous Waste & Hazardous Material, 13:237-244 (1996).

Sedlak, D. L., Andren A. W., Environ. Sci. Technol, 25:777-782 (1991).

Smock, L. A., Stoneburner D. L., Clark J. R., Water Res., 10:537-543 (1976).

Dow

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] at

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DEVICES FOR REMEDIATION OF CONTAMINATED SOILS 1531

Venkadatri, R., Peters R. W., Hazardous Waste & Hazardous Materials, 10:107-149(1995).

Watts, R. J., Udell M. D., Monsen R. M., Water Environ. Res., 65:839-844 (1993).

Won, W. D., Disalvo L. H., Ng. J., Appl. Environ. Microbiol, 31:576-580 (1974).

Won, W. D., Heckly R. J., Glover D. J., Hoffsommer J. C . , Appl. Microbiol.,27:513-516(1974).

Received: April 5, 1998

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