Charles M. Reynolds, Prasanta Bhunia, and Brent A. Koenen August 1997

Soil Remediation Demonstration

Project: Biodegradation of

Heavy Fuel Oils

SPECIAL REPORT 97-20
Abstract: Treatment of oil-contaminated soils is necessary to protect water supplies, human health, and environmental quality; but because of limited funds,

cleanup costs are often prohibitive. High costs are exacerbated in cold regions such as Alaska, where spills

are often in areas inaccessible to heavy equipment and

where there is limited infrastructure. Owing to the lack

of infrastructure, widespread fuel distribution systems,

and the need for heating in the cold climate, there are

numerous small-scale oil spills. Low-cost treatments

applicable to small-scale spills are needed. The object of

this CPAR project was to examine using cost-effective,

on-site bioremediation techniques for heavy-oil-contaminated soil in cold regions. Both heavy-oil and dieHow to get copies of CRREL technical publications:

Department of Defense personnel and contractors may order reports through the Defense Technical Information Center:

DTIC-BR SUITE 0944

8725 JOHN J KINGMAN RD

FT BELVOIR VA 22060-6218

Telephone 1 800 225 3842

E-mail help@dtic.mil

msorders@dtic.mil

WWW http://www.dtic.dla.mil/

All others may order reports through the National Technical Information Service:

NTIS

5285 PORT ROYAL RD

SPRINGFIELD VA 22161

Telephone 1 703 487 4650

1 703 487 4639 (TDD for the hearing-impaired)

E-mail orders@ntis.fedworld.gov

WWW http://www.fedworld.gov/ntis/ntishome.html

A complete list of all CRREL technical publications is available from

USACRREL (CECRL-LP)

72 LYME RD

HANOVER NH 03755-1290

Telephone 1 603 646 4338

E-mail techpubs@crrel.usace.army.mil

For information on all aspects of the Cold Regions Research and Engineering Laboratory, visit our World Wide Web site:

http://www.crrel.usace.army.mil

sel-contaminated soils were used to compare

landfarming, a low-intensity treatment, to pile bioventing,

a costlier treatment. For each soil–contaminant combination, we compared nutrient additions to a control

with no nutrient additions. Under the conditions of this study,

landfarming with nutrient additions was as effective for treating diesel-contaminated soil as was bioventing with nutrient additions. For heavy oils, landfarming with nutrients

resulted in lower soil concentrations after one year, but differences among treatments were not statistically significant.

Because landfarming does not require pumps, electricity,

or plumbing, all costs are less than for bioventing. The

minimal requirements for infrastructure also make

landfarming attractive in remote sites typical of cold regions.
Special Report 97-20

Charles M. Reynolds, Prasanta Bhunia, and Brent A. Koenen August 1997

Prepared for

OFFICE OF THE CHIEF OF ENGINEERS

Approved for public release; distribution is unlimited.

Soil Remediation Demonstration

Project: Biodegradation of

Heavy Fuel Oils

US Army Corps

of Engineers®

Cold Regions Research &

Engineering Laboratory
PREFACE

This report was prepared by Dr. Charles M. Reynolds, Research Physical Scientist, Geochemical Sciences Division, Research and Engineering Directorate, U.S.

Army Cold Regions Research and Engineering Laboratory, Dr. Prasanta Bhunia,

Project Manager, Weston and Sampson Engineers, Inc., and Brent A. Koenen, Environmental Protection Specialist, Geochemical Sciences Division, CRREL.

The objective of the Construction Productivity Advancement Research (CPAR)

demonstration project, Soil Remediation Demonstration Project: Biodegradation of Heavy

Fuel Oils, was to demonstrate, evaluate, and increase the knowledge base for using

cost-effective, on-site bioremediation techniques for heavy-oil-contaminated soil

in cold and seasonally cold regions. To achieve these objectives, a Project Team was

developed that included representatives from the private sector, CRREL, the U.S.

Army Engineer District, Alaska, the University of Alaska, and the Alaska Department of Environmental Conservation. The CPAR industry partner, Weston and

Sampson Engineers, Inc., worked closely with their cooperator, AGRA Earth and

Environmental, Inc., who conducted the site implementation and operation activities. The site was accessible to visitors and tours throughout the demonstration.

The authors acknowledge the contributions of others to this project: Dr. I.K.

Iskandar, Chief, Geochemical Sciences Division; D.L. Hardy, U.S. Army Engineer

District, Alaska, who provided user perspective at the initial planning meeting;

and B. Thomas, formerly with the Alaska Department of Environmental Conservation, who assisted with regulatory requirements.

A significant amount of laboratory and field work was required to accomplish

the project goals. The expertise of L.B. Perry and C.S. Pidgeon, who conducted

much of the laboratory analysis, was an essential part of this project. R.N. Bailey,

J.P. Lariviere, E. Cuthbertson, and J. Velazquez also were essential in conducting

the laboratory analyses. B.G. Harrington provided the data-logger support and P.

Robinson assisted in the field work. Both MAJ M. Meeks and LTC S. Wagner provided field support and assistance in Alaska. Technical review of this report was

provided by Dr. C.J. Martel and S. Hardy, both of CRREL.

The contents of this report are not to be used for advertising or promotional

purposes. Citation of brand names does not constitute an official endorsement or

approval of the use of such commercial products.

ii
EXECUTIVE SUMMARY

The objective of the Construction Productivity Advancement Research (CPAR)

project, Soil Remediation Demonstration Project: Biodegradation of Heavy Fuel Oils, was

to demonstrate, evaluate, and increase the knowledge base for using cost-effective,

on-site bioremediation techniques for heavy-oil-contaminated soil in cold and seasonally cold regions. To accomplish this objective, CRREL and Weston and Sampson

Engineers, Inc., conducted a side by side comparison of the commonly used

bioventing treatment and the lower-cost landfarming treatment for both dieseland heavy-oil-contaminated soils.

Treatment of oil-contaminated soils is necessary to protect water supplies, human health, and environmental quality; but, because limited resources are causing

increasingly greater competition for funds, cleanup costs are often prohibitive. High

costs are exacerbated in cold regions, such as Alaska, where the spills are often in

areas inaccessible to heavy equipment and where there is limited infrastructure.

Because of the lack of infrastructure, widespread fuel distribution systems, and the

need for heating in a cold climate, there are numerous small-scale oil spills in cold

regions. Low-cost treatment strategies for these sites are needed.

Our focus was to compare systems applicable to small-scale spills and see if a

relatively low-intensity method (landfarming) could compete with more a frequently

used but costlier treatment (pile bioventing), without the need for heavy equipment or high energy inputs. Two soils were used to evaluate the two treatment

systems: one soil contaminated with heavy oil and the other contaminated with

diesel. Diesel-contaminated soils have been shown to respond to biotreatment, both

in landfarming and bioventing. Biotreatment of soils contaminated with heavier

oils, such as no. 6 heating oil, bunker C fuel oil, and crude oil, have not been evaluated to the same degree as diesel-fuel-contaminated soil. Because a greater proportion of heavy oils is composed of recalcitrant compounds that have limited water

solubility, heavy oils are less readily bioremediated than is diesel fuel.

For each soil–contaminant combination, we compared added nutrients to a control with no nutrients. Under the condition of this study, landfarming with nutrient

additions was as effective for treating diesel-contaminated soil as was bioventing

with nutrient additions. For heavy oils, landfarming with nutrients resulted in lower

average soil concentrations after 1 year, but the differences among treatments was

not statistically significant. The average Total Petroleum Hydrocarbon (TPH) concentrations for each treatment after 362 days are shown in the following table.

Soil TPH concentrations (mg kg–1) for each treatment after 362 days.

Heavy Oil* Diesel†

Landfarming Bioventing Landfarming Bioventing

+Nutrients 4262 4736 1664 1447

–Nutrients 4959 4985 2430 1581

*Initial TPH value, 6157 mg kg–1.

†Initial TPH value, 8348 mg kg–1.

iii
Under the condition of this evaluation, landfarming resulted in significantly

greater initial remediation rates for both the heavy-oil and diesel-contaminated

soils than did bioventing, and this effect was most pronounced with nutrient additions. In general, diesel-contaminated soil was more effectively treated than the

heavy-oil-contaminated soil.

Nutrient additions increased the effects of landfarming for both heavy-oil- and

diesel-contaminated soil, but only influenced the diesel-contaminated soil in the

bioventing treatments.

For soils contaminated by heavy oils, landfarming resulted in greater

bioremediation rates than did the bioventing treatment during the initial treatment

stages. Although bioventing was ineffective in reducing the contaminant levels in

the initial phase of treatment for the heavy-oil-contaminated soil, bioventing appeared to have stimulated microbial activity and possibly microbial biomass during the initial phase. We believe that increased microbial biomass caused artificially high TPH analyses at the first sampling date, resulting in a zero or negative

treatment effect for the first time interval. A similar pattern for crude-oil-contaminated soil was observed during the following warmer season. During the second

summer, soil TPH values in the crude-oil-contaminated soil using the bioventing

treatment were significantly lower than those for landfarming at the spring sampling time, but appeared to increase by the end of the summer. Continued bioventing

may result in lower TPH levels each year of operation, but this cannot be determined by these data.

Because landfarming does not require pumps, electricity, plumbing, or wiring,

all costs (capital, maintenance, and operation) are less than for bioventing. The

minimal requirements for infrastructure also make landfarming attractive in remote sites typical of cold regions. This project demonstrated that landfarming can

compete in both performance and cost for remediation of both heavy-oil- and

diesel-contaminated soils at those remote sites.

iv
INTRODUCTION

Background

There have been numerous petroleum releases

in cold, remote regions. Alternatives for cleanup

are limited by the remote locations, difficulties in

mobilization of heavy equipment, inability to effectively monitor the biotreatment processes, and

the costs of site operation. To remediate petroleumcontaminated sites, we need a low-cost, lowinput treatment alternative to use in conjunction

with existing methods.

In general, indigenous soil microbiota can degrade petroleum compounds. When soils fail to

bioremediate at optimum rates, it is often a function of the water solubility of the compound and

environmental limitations imposed on the microbes. Major limitations to the microbiota are temperatures that are too high or too low, excess or

deficient water, insufficient or excessive nutrients,

insufficient carbon in a form that microorganisms

can use, poor mixing or distribution of the petroleum in the soil, and, for aerobic microorganisms,

lack of oxygen (O2).

The relative effectiveness of different treatment

systems will vary over time. For example, lack of

oxygen has been believed to be the primary limitation at depth; thus, air-injection technologies are

commonly employed to overcome this. However,

it is now well established that subsurface (relatively deep) microbial activity is common, and

anaerobic biodegradation of water-soluble petroleum takes place without the need to inject air if

alternate electron acceptors, such as oxidized species of iron or nitrogen (such as nitrate), are available. The anaerobic processes are significantly

slower than aerobic processes, but they are less

expensive than adding air. The approximate tradeoff among air-injection technologies, passive biodegradation, and anaerobic biodegradation is time

versus resources (Fig. 1).

Bioremediation treatments are successful when

limitations are overcome. The key problem, however, is identifying and implementing the most

cost-effective means of doing this at isolated, cold

sites. Two important aspects in comparing lowcost to more costlier alternatives are time constraints and monitoring difficulties.

In comparing treatments, it is important to

measure effectiveness over time. In applying a

bioremediation technology to a particular site, it

is also important to consider contaminant transport, leaching, and the location of the problem. The

rate of treatment must be compared to the rate of

leaching and the distance between the contaminated soil and the area where it might cause

harm—the potential receptor. For many sites,

transport rates and distance to receptors are such

that remediation need not be immediate. If a

longer time is acceptable for remediation, more

treatment options and lower costs can be considered.

A final difficulty in comparing the effectiveness

of treatments is that of obtaining accurate measurements in the field. Limitations to effective

bioremediation have been identified primarily

through laboratory studies. Measuring rates in the

field is much more difficult because we cannot

control field conditions effectively. In a field study,

where we tried to measure bioremediation rates

in a 1-acre (0.4-ha) landfarm that we had treated

uniformly, we found that the bioremediation rates

varied up to seven-fold (Reynolds 1993b).

Diesel-contaminated soils have been shown to

Soil Remediation Demonstration Project:

Biodegradation of Heavy Fuel Oils

CHARLES M. REYNOLDS, PRASANTA BHUNIA, AND BRENT A. KOENEN
respond to biotreatment. Landfarming can be a

successful treatment option in cold regions

(Reynolds 1993a,b; Reynolds et al. 1994).

Bioventing of stockpiled, diesel-contaminated soil

has also been used in northern climates, but owing

to low temperatures and the distance of many sites

from readily accessible highways, logistical, construction, and maintenance requirements and costs

are greater than in more temperate climates.

Studies have shown that stimulating soil microbial activity in diesel-contaminated soils in

biopiles may raise soil temperatures by 1–3°C (Brar

et al. 1993). Also, nutrient amendments to dieselcontaminated soil can enhance bioremediation

rates in both landfarming and bioventing

(Reynolds 1993b, Brar et al. 1993, Walworth and

Reynolds 1995).

Biotreatment of soils contaminated with heavier

oils, such as no. 6 heating oil, bunker C fuel oil,

and crude oil, have not been evaluated to the same

degree as diesel-fuel-contaminated soil. And, because a greater proportion of heavy fuels is composed of recalcitrant compounds that have limited water solubility, these contaminants are less

readily bioremediated than diesel fuel.

Objective

The objective of this project was to demonstrate,

evaluate, and increase the knowledge base on using cost-effective, on-site bioremediation techniques for treating heavy-oil-contaminated soil in

seasonally cold regions.

Approach

The research plan was to compare landfarming

and bioventing as treatment technologies for

heavy-fuel- and diesel-contaminated soils in cold

regions. This was done by conducting side by side

comparisons in the field. Because so much less is

known about degradation of heavy-fuel-contaminated soils as compared to diesel-fuel contamination, we expected that a double comparison would

provide a better context for analyzing the different techniques.

Project location and soil history

This CPAR project was conducted at the Farmers Loop Permafrost Research Facility in

Fairbanks, Alaska. For each biotreatment system

(landfarming and ex-situ pile–bioventing), two

soils were used. One soil was from a gravel pad

area near pump station number 10 on the transAlaska pipeline. This soil was contaminated with

heavy oil. The other was a sandy soil contaminated

with diesel. This material had been used as tank

bedding and backfill for a fuel storage tank at Ft.

Wainwright, Alaska, and was excavated during

tank replacement. These two soils are typical of

many contaminated soil sites in northern regions.

FIELD REMEDIATION PROCEDURES

For each contaminated soil, we compared the

effects of landfarming to those of bioventing.

For all soil-contaminant and treatment scenarios,

we also tested the effects of nutrient additions

(Table 1).

To comply with regulatory guidelines that were

in effect at the start of the field work, treatments

were conducted in plots that were lined and

bermed. For the landfarming plots, the cells were

approximately 3 m square and 60 cm deep. The

bioventing plots were approximately 1.5 by 3 m

by 100 cm deep. These configurations are representative of both landfarming and bioventing procedures for small-scale spills. Landfarming usually distributes soil in a relatively thin layer that

requires a greater area than bioventing, which

can use deeper layers of soil.

Figure 1. Relative inputs and treatment times for

remediation technologies.

Table 1. Demonstration factors.

Factor Levels Description

Contaminant 2 Heavy-oil, diesel

Treatments 2 Landfarm, bioventing

Subfactors Levels Description

Landfarm 2 Control, plus nutrients

Bioventing 2 Control, plus nutrients

High Input Low Input

2

Freeze–thaw stimulated activity

Natural attenuation
Bioventing plots had two evenly spaced airextraction lines placed horizontally, approximately

45 cm from the surface. The cells were covered by

liner material. Air flow was created by pumping a

vacuum on the air extraction lines in the

bioventing piles. During operation, the pumps

were cycled on a schedule of five evenly spaced

1-hour intervals during 24 hours.

Spatial variability

We addressed the problem of spatial variability in soil contamination by using well-mixed

contaminated soil in buried nylon “net” bags. To

obtain uniform soils for the bags, we removed

composite samples from each cell of the two contaminated soils. Approximately 350 subsamples

were taken and composited for each soil.

Composited samples were homogenized in a large

rotary mixer. Because the total amount of the

composited sample of each soil was too large to

mix at once, it was divided into thirds and each

third was mixed for 30 minutes, then the three

portions were inter-mixed for 1 hour. The net bags

permitted mass and energy fluxes throughout the

soil both inside and outside of the bags, yet allowed us to recover the soil for time-series sampling. For each treatment, we used enough bags

for triplicate samples at each time-series sampling.

For the landfarm, each bag was cylindrical and

measured approximately 5 cm in diameter and 40

to 50 cm in length. We made the net cylinders by

rolling a portion of netting around a hollow metal

form until two complete layers of netting covered

the form, and then tying a knot in the netting to

secure the bottom. The net-wrapped form was

filled with the well-mixed contaminated soil. After filling, the hollow form was removed from the

netting and the sample was placed back into the

field soil.

This procedure let us obtain relatively uniform

field data for this study. It provided a uniform initial contaminant concentration level in each bag

with a sufficient number of bags in each cell for

replicate, time-series sampling.

Nutrient amendments

Nutrients were uniformly spread on the surface

of appropriate cells. Commercially available agricultural fertilizer, granular 20-20-10, was used. The

nitrogen form was ammonium (NH4

+). We applied fertilizer to the surface because this method,

with a minimum of labor and machinery, is the

most likely to be used in the field. Application rates

were approximately 0.62 kg m–2 (0.13 lb ft–2) on

the landfarm and approximately 1.23 kg m–2 (0.25

lb ft–2) on the bioventing cells. Twice as much fertilizer was applied to the bioventing cells because

they were nearly twice as deep as the landfarming

cells. This resulted in similar amounts of nutrients

added on a mass:mass basis.

Sampling and analysis

After 54 days, triplicate sample bags were randomly removed from each cell and sampled for

Total Petroleum Hydrocarbon (TPH) fractions.

TPH extractions from the soil were done by

sonication with methylene chloride. Anhydrous

sodium sulfate was added to the soil during extraction as a drying agent. Extracts initially were

analyzed by gravimetric analysis and then by

resolu-bilizing in methylene chloride followed by

gas chromatography and flame ionization detection (GC-FID). For TPH, chromatograms were integrated from baseline to baseline.

Costs

Estimates for this project were based on treating 500 yd3 (382 m3) for 1 year and ranged from

$5–$11 yd–3 ($3.82–$8.41 m–3) for landfarming and

$20–$23 yd–3 ($15.30–$17.59 m–3) for bioventing.

Cost breakdowns are provided in Table 2.

In this demonstration, all soil was excavated

from other sites and transported to the demonstration site at Farmers Loop; therefore, soil handling costs were the same for both treatments.

Other costs that were equal for the two treatments

include acquisition and application of nutrients

and, for this demonstration, monitoring.

Costs that were incurred in bioventing, but not

landfarming, included plumbing for air flow,

blowers, wiring, electricity for operation, periodic

monitoring of the blowers, and maintenance of the

blowers. In practice, in-situ landfarming may be

applicable at many sites because heavier oils and

more recalcitrant compounds are typically less

mobile. In-situ treatment would remove both liner

and soil handling costs.

Remediation costs are site specific and absolute values derived from a particular site can be

transferred to other sites only with caution. Typically, costs are reported per ton or per cubic

yard, but consideration must be given to the

fixed costs, such as mobilization and decontamination of equipment, that are required regardless of the volume treated. With larger volumes

of soil treated, fixed costs are distributed over a

greater volume of soil and result in a lower per

unit cost.

3
RESULTS AND DISCUSSION

Initial samples and contaminant homogeneity

Measuring field bioremediation rates is difficult because of the nonuniformity of contaminant

distribution; it is also costly. Yet, bioremediation

rate comparisons, based on direct field measurements, are the true measure of treatment effects. To

effectively compare landfarming to bioventing, we

must either develop a better system for field monitoring, or wait a longer time before measuring so

that differences would be more pronounced, or

know that the effects of the treatments would be

vastly different. Because the effect of the treatments

is our unknown and a comparison of rates over time

is important, the only acceptable option was to develop a better system for field monitoring.

To determine a bioremediation rate at any given

time, we must be able to compare contaminant

concentrations to the initial concentration of the

contaminant in the soil. To make valid rate comparisons, it is essential either to provide known

contaminant concentrations at the start (to) or take

an extremely large number of samples to quantify

the random error caused by spatial variability.

Because of the “destructive nature” of taking

samples (i.e., you cannot actually resample the

same volume of soil) and the difficulty in determining exactly how many samples would be required to sufficiently reduce the variability, we

chose to use a method that provided uniform

sample concentrations at the start, as described in

the Sampling and Analysis section.

Random samples taken at the beginning of the

field study were analyzed for TPH components

to determine the variability at to. Results (Table 3)

show that distribution of TPH and other petroleum

fractions had a Coefficient of Variation (CV) less

than 5%, were homogeneous, and demonstrated

that using mixed soil in permeable bags provides

uniform to samples. Thus, this technique provided

equal starting concentrations on which to base

remediation rates.

On the basis of previous studies of relative rates

of degradation, the diesel soil was expected to

degrade faster than the heavy oil because of the

smaller percentage of more recalcitrant, heavy-oil

compounds.

Initial incubation period: elapsed time 0 to 54

days, 29 July to 21 September 1995

Diesel

For diesel-contaminated soil, all treatments decreased relative to the to values during the first 54

days of treatment (Fig. 2). Landfarming with nutrients was the most effective and had significantly

(P < 0.05) lower TPH concentrations at t54 than

did the other treatments. TPH concentrations in

the landfarming without nutrient treatment also

decreased relative to the to values and had lower

(P < 0.10) TPH concentrations than the bioventing

treatments, but not to the same degree as TPH

concentrations when nutrients were added.

Bioventing treatments, both with and without

nutrients, were less effective than the landfarmTable 2. Itemized costs ($) of treatment options for 500 yd3 (382 m3) of contaminated soil.

Bioventing Landfarming

(percent time blower on) (percent lined and covered)

Item 100% 50% 20% 100% 0

Earthwork subcontract 3950 3950 3950 1950 1950

Mobilization/decontamination 200 200 200 200 200

Electrical subcontract 2760 2760 2760 N/A N/A

System piping (venting, water) 750 750 750 0 0

Bottom liner 480 480 480 2400 0

Regenerative blower 1000 1000 1000 N/A N/A

Polyethylene cover 250 250 250 250 0

Electrical power ($0.11 per kW) 1445 723 301 0 0

Electrical start-up draw 217 108 45 0 0

(15% of total electrical)

Nutrients 450 450 450 450 450

Total 11,502 10,671 10,186 5250 2600

Total cost per yd3 23 21 20 11 5

Total cost per m3 17.58 16.06 15.29 8.41 3.82

4
ing treatments during the to to t54 interval.

Because diesel has a larger percentage of

volatile and mobile constituents than heavy oil,

the to to t54 data suggested that volatilization and

diffusion accounted for a portion of the initial

losses.

Heavy oil

During the to to t54 interval, decreases in TPH

concentrations were much less in the heavy-oilcontaminated soil than in the diesel-contaminated

soil (Fig. 3). We observed the same ranking for

efficacy of treatments as we did for the dieselcontaminated soil; landfarming with nutrient

amendments again was statistically the best treatment. In contrast to the diesel-contaminated soil,

there was essentially no decrease in heavy oil TPH

levels in the bioventing treatments during the initial treatment phase.

Cold season incubation: elapsed time, 54 to 238

days, 21 September 1995 to 16 May 1996

Diesel

TPH concentrations decreased for all treatments

during t54 to t238 (Fig. 2). During a significant portion of this time, the soil was frozen. However, an

unusual warm period in September 1995 kept the

soil warmer for longer than normal and this

probably contributed to the decrease in TPH levels

during this period. The rates of TPH decrease during this time were not significantly different for the

two landfarming treatments and averaged 13.6 mg

kg–1 day–1. TPH reduction rates for the two bioventing treatments were also similar to each other,

averaging 23.8 mg kg–1 day–1. However, the TPH

reduction rates in bioventing treatments were significantly greater than in landfarming treatments

during this time. From our data, we cannot sepaTable 3. Concentrations (mg kg–1) at to (methylene chloride extraction + sonication).

Fraction Heavy-oil mean Diesel mean

TPHgravimetric 11389 ±309 8480 ±267

TPHgas chromatography 6072 ±266 8348 ±291

Figure 2. TPH reduction, diesel (LF = landfarming; BV = bioventing).

5
rate TPH reductions that may have been caused

by biodegradation during the early portion of this

time, or transport processes that may have been

influenced by freezing and freeze–thaw cycles

during the winter and early spring. Some samples

taken on 16 May 1996 were still partially frozen,

suggesting that temperatures sufficiently high for

significant biodegradation to occur following soil

thawing had not yet been attained. The TPH concentrations for the diesel-contaminated soil on 16

May were not significantly different (P < 0.05) for

any of the treatments.

Heavy oil

TPH concentrations decreased more rapidly for

both of the bioventing treatments than for either

of the landfarming treatments during the coldseason phase of the operation (Fig. 2). Similar to

the diesel-contaminated soil, the nutrientamended and no-nutrient bioventing treatments

decreased TPH concentrations in the heavy-oilcontaminated soil at similar rates, averaging

16.2 mg kg–1 day–1. TPH reduction rates in

the landfarming treatments were only 5.5 mg

kg–1 day–1 during this time. In contrast to the

diesel-contaminated soil, the samples taken on

16 May from the bioventing treatments in the

heavy-oil-contaminated soil had significantly

lower TPH concentrations than did the

landfarming treatments. Because these samples

were from a greater depth than the landfarming samples, the lag-time preceding soil freezing may have allowed longer treatment time

in the bioventing cells vs. the landfarming

cells.

Summer incubation: elapsed time, 238 to 362

days, 16 May to 17 September 1996

Diesel

Nutrient amendments appeared to have a

greater effect than either landfarming or

bioventing on the TPH concentrations by t362 (Fig.

2). TPH concentrations in the nutrient-amended

bioventing treatment continued to decrease during the summer and at t362 were less than those in

the nutrient-amended landfarming treatment.

There was little change from t238 to t362 in the treatments where no nutrients had been applied.

Heavy oil

Changes in the TPH concentrations in the heavy

oil concentrations from t238 to t362 are noticeable;

the TPH concentrations appear to actually increase

in both bioventing treatments and remain constant

in the landfarming treatments (Fig. 3). Landfarming with nutrients tended towards greater

TPH reduction than the other three treatments, but

this effect was not significant. The variability in

TPH concentrations at t362 for both landfarming

treatments was greater than for either bioventing

treatments, suggesting that the processes causing

Figure 3. TPH reduction, heavy oil (LF = landfarming; BV = bioventing).

6
TPH reduction were more responsive to a variable that was not well controlled.

DISCUSSION

After 362 days of treatment, landfarming was

as effective in reducing TPH concentrations in

diesel-contaminated soil as was bioventing. Nutrient additions had a significant effect on reducing diesel concentrations for both landfarming and

bioventing.

For heavy-oil-contaminated soil, the effect of

nutrient additions was less evident and there were

no significant differences among any treatments

at t362. For both bioventing treatments, measured

TPH concentrations increased from t238 to t362.

Several factors may account for this. When using

TPH as an indicator of treatment effects, many

have observed an apparent increase in TPH concentrations at the onset of biotreatment. We hypothesize that initial increases in measured TPH

are caused by an increase in microbial biomass that

accompanies a growing microbial population and

precedes measurable decreases in TPH concentrations. During the initial phases of degradation, the

microorganisms use bioavailable forms of native

soil carbon rather than contaminant carbon. Native soil carbon forms are less likely to be included

in TPH extractions or measurements. However, the

metabolites produced by the rapidly expanding

population do appear as part of the TPH measurement. As the microbial population increases, measured TPH concentrations increase as bioavailable

native soil carbon becomes depleted with no decrease in contaminant carbon in the soil. TPH concentrations would not decrease until after

bioavailable carbon has been consumed and contaminant carbon is used. Subsequent mineralization of the contaminant carbon would then eventually result in a decrease in soil contaminant TPH

concentrations.

CONCLUSIONS

This demonstration showed that landfarming

can be a reasonable alternative to bioventing for

both heavy-oil- and diesel-contaminated soils at

remote sites typical of cold regions. In dieselcontaminated soil, reduction in TPH concentrations was greatest using landfarming with nutrient amendments. Landfarming with nutrient

additions should be considered as a treatment option at sites where it can be easily used.

Annual reductions in TPH concentrations for

the heavy oil after approximately 1 year were not

significantly different for any of the treatments.

For heavy-oil-contaminated soil, landfarming was

more effective than bioventing during the initial

phase of treatment, and this effect was more pronounced when nutrients were added. The lag period that occurs prior to rapid microbial growth

and increased activity appeared to have a greater

effect in the heavy-oil-contaminated soil compared

to the diesel-contaminated soil. We hypothesize

that the measured increase in TPH concentrations

is an analytical artifact of microbial fatty acids and

related microbial biomass that are produced during adaptation of the soil microbiota to new conditions and carbon sources. If this is the cause, it

is reasonable to predict that, given favorable incubation conditions that are sufficiently long, there

may be a period of rapid heavy-oil bioremediation

following the temporary increase in measured

TPH values. However, if the favorable incubation

time is too short owing to a brief summer season,

the same cycle may occur in subsequent years.

Low-cost strategies that further stimulate the microbial population may be needed to effectively

treat these soils. Recent studies suggest that plantbased systems may be useful (Nichols et al. 1997).

These data demonstrate that, depending on the

nature of the contaminant and nutrient status of

the soil, the brevity of the summer season—when

temperatures are favorable for microbial activity—

may prevent either unamended or nutrientamended biotreatment from attaining sufficient

microbial numbers and activity to substantially

reduce TPH concentrations during that season.

This may result from microbial population cycling,

from low populations at early summer to high

populations at late summer, with little TPH metabolized. The persistence of the heavier fraction

of older oil spills in cold regions suggests that this

may be happening (Collins et al. 1993). For diesel

spills, the effect is not as pronounced and many of

the compounds are more readily degraded; hence,

nutrient amendments appeared to provide sufficient stimulation to significantly reduce TPH concentrations.

Despite both treatments being done ex situ (requiring excavation and transportation of soil),

costs for the landfarming treatment were less than

for bioventing. The reduced requirements for infrastructure also make landfarming attractive in

remote sites typical of cold regions. Landfarm installation and operation in a remote area is less

7
costly than bioventing. Similarly, the remoteness

of many contaminated sites may allow more time

for the biomediation process, which would favor

a low-input, low-maintenance landfarming system.

Substantial cost savings may be realized in using landfarming at many remote sites, but absolute dollar savings can not be predicted without

knowing the specifics for each site. The costs for

application of any soil treatment technology are

site dependent, and the cost savings derived from

using landfarming vary with both site specifics

and the alternative cleanup strategies that may be

available.

RECOMMENDATIONS

Because of lower costs and treatment that was

as effective as bioventing, landfarming should be

given consideration for treating heavy-oilcontaminated soils in cold regions. Land-farming

has lower capital, operation, and maintenance

costs than bioventing and may be used in situ on

some surface-contained spills. Surface applied nutrients can be used and mixing by tilling is not

essential. Additionally, landfarming is a robust

system that can recover from harsh environmental changes, such as freezing and drying. This demonstration has shown that it is effective for both

diesel and heavy-oil contamination.

COMMERCIALIZATION PLAN

The products of this project include data

that demonstrate landfarming and bioventing to

be equally successful in treating heavy-oilcontaminated soil. Additionally, there have been

visitors at the site to see the landfarming and

bioventing processes. Weston and Sampson Engineering and Consulting and AGRA Earth and

Environmental now have experience plus data and

cost figures to present to potential clients. Regional, national, and international conferences

where presentations covering this demonstration

has been made or submitted are listed below.

• Cold Regions Remediation Conference, BP Exploration (Alaska), 26–27 March 1997, Anchorage,

Alaska.

• Second Tri-Service Environmental Technology

Workshop, 10–12 June 1997, St. Louis, Missouri.

• U.S. Army Corps of Engineers, Innovative Technologies HTRW Workshop, 17–21 March 1997, Las

Vegas, Nevada.

• Fifth International Symposium on Cold Region

Development, American Society of Civil Engineers—Technical Council of Cold Regions Engineering, 4–10 May 1997, Anchorage, Alaska.

• Fourth International Symposium, In-Situ and

Onsite Bioreclamation, 28 April–1 May 1997, New

Orleans, Louisiana.

• European Union Workshop on Soil Remediation,

16–19 November 1996, Rothamsted, UK.

 • Third Annual International Petroleum Environmental Conference, 24–27 September 1996, Albuquerque, New Mexico.

• Soil Science Society of America, 3–8 November

1996, Indianapolis, Indiana.

LITERATURE CITED

Brar, G.S., P.M. Currier, and C.M. Reynolds (1993)

Remediation of petroleum contaminated soils with

bioventing in cold regions. Superfluid XIV Conference, 29 November–1 December, Washington, D.C.

Collins, C.M., C.H. Racine, and M.E. Walsh (1993)

Fate and effects of crude oil spilled on subarctic

permafrost terrain in interior Alaska: Fifteen years

later. USA Cold Regions Research and Engineering Laboratory, CRREL Report 93-13.

Nichols, T.D., D.C. Wolf, H.B. Rogers, C.A.

Beyrouty, and C.M. Reynolds (1997) Rhizosphere

microbial populations in contaminated soils. Water, Air, and Soil Pollution, 95: 165–178.

Reynolds, C.M. (1993a) Contaminated soil treatment in cold regions. American Public Works Association Reporter, July, p. 26.

Reynolds, C.M. (1993b) Field measured

bioremediation rates in a cold region landfarm:

Spatial variability relationships. In Proceedings of

the Seventh Annual East Coast Conference on Hydrocarbon Contaminated Soils (P.T. Kostecki and E.J.

Calabrese, Eds.) Chelsea, Michigan: Lewis Publishers, p. 487–499.

Reynolds, C.M., M. Travis, W.A. Braley, and R.J.

Scholze (1994) Applying field expedient

bioreactors and landfarming in cold climates. In

Second International Symposium, In-Situ and Onsite

Bioreclamation. Chelsea, Michigan: Lewis Publishers, p. 100–106.

Walworth, J.L., and C.M. Reynolds (1995)

Bioremediation of a petroleum contaminated soil:

Effects of phosphorus, nitrogen, and temperature.

Journal of Soil Contamination, 4(3): 299–310.

8
1. AGENCY USE ONLY (Leave blank) 2. REPORT DATE 3. REPORT TYPE AND DATES COVERED

4. TITLE AND SUBTITLE 5. FUNDING NUMBERS

6. AUTHORS

7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) 8. PERFORMING ORGANIZATION

 REPORT NUMBER

9. SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES) 10. SPONSORING/MONITORING

 AGENCY REPORT NUMBER

11. SUPPLEMENTARY NOTES

12a. DISTRIBUTION/AVAILABILITY STATEMENT 12b. DISTRIBUTION CODE

13. ABSTRACT (Maximum 200 words)

14. SUBJECT TERMS 15. NUMBER OF PAGES

16. PRICE CODE

17. SECURITY CLASSIFICATION 18. SECURITY CLASSIFICATION 19. SECURITY CLASSIFICATION 20. LIMITATION OF ABSTRACT

 OF REPORT OF THIS PAGE OF ABSTRACT

NSN 7540-01-280-5500 Standard Form 298 (Rev. 2-89)

Prescribed by ANSI Std. Z39-18

298-102

REPORT DOCUMENTATION PAGE Form Approved

OMB No. 0704-0188

Public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and

maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information,

including suggestion for reducing this burden, to Washington Headquarters Services, Directorate for Information Operations and Reports, 1215 Jefferson Davis Highway, Suite 1204, Arlington,

VA 22202-4302, and to the Office of Management and Budget, Paperwork Reduction Project (0704-0188), Washington, DC 20503.

August 1997

Soil Remediation Demonstration Project: Biodegradation of Heavy Fuel Oils

Charles M. Reynolds, Prasanta Bhunia, and Brent A. Koenen

U.S. Army Cold Regions Research and Engineering Laboratory

72 Lyme Road

Hanover, New Hampshire 03755-1290

Special Report 97-20

Approved for public release; distribution is unlimited.

Available from NTIS, Springfield, Virginia 22161

Office of the Chief of Engineers

Washington, D.C. 20314-1000

For conversion of SI units to non-SI units of measurement consult ASTM Standard E380-93, Standard Practice for Use of the

International System of Units, published by the American Society for Testing and Materials, 1916 Race St., Philadelphia, Pa. 19103.

16

UNCLASSIFIED UNCLASSIFIED UNCLASSIFIED UL

Biotreatment Diesel

Bioventing Land farming

Crude oil Petroleum

Treatment of oil-contaminated soils is necessary to protect water supplies, human health, and environmental

quality; but because of limited funds, cleanup costs are often prohibitive. High costs are exacerbated in cold regions such as Alaska, where spills are often in areas inaccessible to heavy equipment and where there is limited

infrastructure. Owing to the lack of infrastructure, widespread fuel distribution systems, and the need for heating

in the cold climate, there are numerous small-scale oil spills. Low-cost treatments applicable to small-scale spills

are needed. The object of this CPAR project was to examine using cost-effective, on-site bioremediation techniques

for heavy-oil-contaminated soil in cold regions. Both heavy-oil and diesel-contaminated soils were used to compare landfarming, a low-intensity treatment, to pile bioventing, a costlier treatment. For each soil–contaminant

combination, we compared nutrient additions to a control with no nutrient additions. Under the conditions of this

study, landfarming with nutrient additions was as effective for treating diesel-contaminated soil as was bioventing

with nutrient additions. For heavy oils, landfarming with nutrients resulted in lower soil concentrations after one

year, but differences among treatments were not statistically significant. Because landfarming does not require

pumps, electricity, or plumbing, all costs are less than for bioventing. The minimal requirements for infrastructure

also make landfarming attractive in remote sites typical of cold regions.