United States
Environmental Protection
Agency
EPA/540/S5-91/001
Jan. 1992
SUPERFUND INNOVATIVE
TECHNOLOGY EVALUATION
Technology Demonstration
Summary
Biological Treatment of Wood
Preserving SITE Groundwater by
Biotrol, Inc.
BioTrol's pilot-scale, fixed-film bio-
logical treatment system was evaluated
for its effectiveness at removing penta-
chlorophenol from groundwater. The_
system employs indigenous microor-
ganisms amended with a specific pen-
tachlorophenol-degrading bacterium.
The demonstration was performed in
.the summer of 1989 at a wood preserv-
ing site in New Brighton, MM. Ground-
water from a well on the site was fed to
the system at 1, 3, and 5 gpm with no
pretreatment other than pH adjustment,
nutrient addition, and temperature con-
trol. Each flowrate was maintained for
about 2 wk while samples were col-
lected for extensive analyses.
At 5 gpm, the system was capable of
eliminating about 96% of the pentachlo-
rophenol in the groundwater and pro-
ducing effluent pentachlorophenol con-
centrations of about 1 ppm. At the lower
flowrates (1 and 3 gpm), removal was
higher (about 99%) and effluent penta-
chlorophenol concentrations were well
below 0.5 ppm.
Review of other data provided by the
developer indicates that the process is
also effective on other hydrocarbons,
including solvents and fuels. The sys-
tem appears to be a compact and cost-
effective treatment for contaminated
wastewaters; it requires minimal oper-
ating attention once acclimated.
This Summary was developed by
EPA's Risk Reduction Engineering
Laboratory, Cincinnati, OH, to announce
key findings of this SITE Demonstra-
tion. These findings are fully docu-
mented in two separate report(s) (see
ordering information at back).
Introduction
The Superfund Innovative Technology
Evaluation (SITE) Program was estab-
lished in 1986 to promote the develop-
ment and use of innovative technologies
to remediate Superfund sites. Contamina-
tion by chemicals from wood preserving
operations has frequently been found at
Superfund sites on the National Priorities
List. Biological destruction of hazardous
chemicals such as pentachlorophenol
(PCP) and creosote-derived polynuclear
aromatic hydrocarbons (PAHs) at wood
preserving sites was deemed to be a suit-
able topic for investigation under the SITE
Program.
This Summary highlights the results of
an evaluation of BioTrol's Aqueous Treat-
ment System (BATS), a fixed- film aerobic
treatment of such groundwater, using a
consortium of pentachlorophenol-degrad-
ing bacteria. Economics of the process
are also assessed.
A wood preserving facility in New
Brighton, MN, was selected for pilot-scale
evaluation of the technology. The site has
Printed on Recycled Paper
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been used for wood treatment with creo-
sote, pentachlorophenol, and chromated
copper arsenate since the 1920s. Reme-
dial Investigation/Feasibility Study (RI/FS)
testwork at the site indicated that both the
soil and the underlying groundwater were
contaminated with pentachlorophenol and
polynuclear aromatic hydrocarbons even
though these chemicals are no longer used
in wood treatment. The owner and opera-
tor of the site, the MacGillis and Gibbs
Company, agreed to host the testing of
the BioTrol system.
Process Description
Two wells were drilled at locations based
on surface and subsurface testing results
In the RI/FS. One of these provided ad-
equate flow (over 5 gpm) and contained
sufficient pentachlorophenol contamination
(-45 ppm) for the study. Although total
polynuclear aromatic hydrocarbon levels
were well below 1 ppm in these samples,
a decision was made to proceed.
The mobile BATS is contained in an
enclosed trailer (20 ft long and 8 ft wide)
in which all the process equipment is
mounted. The only site requirements are
a level area about 50 ft square, potable
water, and electrical power. The system,
shown in Figure 1, consists of a condition-
ing or temper tank, a heater and heat
exchanger, a three-stage fixed-film
bioreactor, a blower, process pumps, and
a nulrlent feed system. The use of a fixed-
film reactor allows for a long solids reten-
tion time in a relatively small reactor vol-
ume, thus reducing production of excess
biomass.
Influent groundwater is pumped directly
from the well to the conditioning tank on a
level-controlled cycle. The pH is adjusted
(if necessary) to just above 7.0 with caus-
tic, and inorganic nitrogen and phospho-
rus nutrients (urea and trisodium phos-
phate) are added. After passing through
the in-line heater and heat exchanger to
ensure a process temperature in the vi-
cinity of 70"F (21 °C), the groundwater is
introduced to the base of the first of the
three bioreactor chambers (Figure 2).
Each chamber contains an inert support
for bacterial growth; in the study corru-
gated polyvinyl chloride sheets were the
support medium used (Figure 3). The in-
fluent is passed up through each chamber
while air is injected at the base of each
chamber through a sparger tube system
fed by a single blower motor.
Start-up and acclimation are accom-
plished by introducing an indigenous bac-
terial population, usually taken from the
local soil. After allowing about 1 wk for
acclimation and development of the bio-
mass, the system can be "seeded" (if nec-
essary) with an inoculum of an organism
with a specific capability to degrade the
target contaminant. For this study, the
system was inoculated with a pentachlo-
rophenol-degrading Flavobacterium spe-
cies and acclimated further by recycle with
the contaminated wastewater. When the
system is fully adapted to the wastewater,
once-through processing is ready to be-
gin.
Test Program
Three increasing flowrates, 1, 3, and 5
gpm, corresponding to residence times of
9, 3, and 1.8 hr, respectively, were se-
lected for study to allow the effectiveness
of the process to be determined at vari-
ous contaminant loadings. Each flowrate
was tested for 2 wk.
The plan agreed to by EPA and BioTrol
called for monitoring of the groundwater
from the selected well, the influent to, the
effluent from, and the two intermediate
stages of the bioreactor for pentachloro-
phenol and other semivolatile organics
using EPA Method 3510/8270 (gc/ms).
Chloride and TOC also were monitored to
assess BioTroPs claim that pentachloro-
phenol removal occurred by mineraliza-
tion to water, carbon dioxide, and salt.
BioTrol was responsible for operating the
system and maintaining system conditions
such as nutrient feed, pH, dissolved oxy-
gen, temperature, etc., whereas EPA's
contractor personnel were responsible for
the sampling/analysis program.
Other parameters also monitored to pro-
vide a complete history of the groundwa-
ter as it passed through the system in-
cluded total and volatile suspended sol-
ids, oil and grease, nitrogen and phos-
phorus, volatile organics, and heavy met-
als. Because there is always concern when
treating wastewaters containing chlorinated
aromatics, testing was also done for chlo-
rinated dioxins and furans. Samplings and
analyses also were carried out before and
after the carbon adsorption units on the
air exhaust line and the effluent line to
determine if significant quantities of the
contaminants were lost by any route other
than biodegradation.
Finally, static bioassays using two spe-
cies, Daphnia magna (water flea) and
Pimephales promelas (minnow) were car-
ried out on the incoming groundwater, the
influent to the reactor, and the effluent.
These tests were performed to determine
whether the groundwater was toxic to
aquatic species and whether treatment re-
moved the chemical source of toxicity.
Results
System parameters monitored through-
out the course of the project indicated
reasonably consistent operation with no
deviations from expected results and no
upsets were observed during the study.
Table 1 summarizes the temperature, pH,
and dissolved oxygen data obtained.
Comparison of pentachlorophenol con-
centrations in the well with the effluent
from the bioreactor demonstrated that the
BioTrol system is capable of achieving
about 96% removal of pentachlorophenol
at the highest flowrate, 5 gpm, and, at
that flowrate, can produce effluent con-
centrations - before carbon polishing - of
approximately 1 ppm. At the lower
flowrates, 3 and 1 gpm, removals were
even higher, approaching 100%, and ef-
fluent concentrations were well below 1
ppm. Table 2 summarizes the pentachlo-
rophenol removals at the three different
flowrates.
The plan to follow the course of the
biodegradation by analyses at the inter-
mediate stages in the bioreactor could not
be 'accomplished due to an unexpected
sampling artifact. The composite sampler
inlet strainers were placed too deep in
each downcomer chamber, thus allowing
backmixed water from the subsequent
chamber to enter the collected samples.
The effect was detected as significant
lower values for the "influent" concentra-
tions for pentachlorophenol {and other pa-
rameters) at sampling point #2 in Figure 2
when compared to the groundwater
samples (sampling point #1) or grab
samples just before the water entered the
bioreactor (sampling point #B). Presum-
ably, the values at the two intermediate
sampling points (#3 and #4) were similarly
affected.
The changes in chloride and TOC re-
sults (obtained once/week) parallel the
decrease in pentachlorophenol at all flows
(Table 3); however, the results are not
sufficiently precise to provide more than
supportive evidence for mineralization of
pentachlorophenol to sodium chloride, wa-
ter, and carbon dioxide. The mineraliza-
tion of PCP by Flavobacterium has been
studied extensively by Crawford and co-
workers; tracer studies have shown that
the degradation proceeds completely to
CO2 and that no intermediate byproducts
are formed.
As part of the effort to confirm that
pentachlorophenol was being removed by
biochemical mineralization and not by ad-
sorption on the biosolids or by stripping
because of the aeration in the bioreactors,
both biomass solids and air emissions
were also analyzed for pentachlorophe-
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Influent
Pump
Heat Exchanger
Table
Control
Panels
Temper Tank
Figure 1. Biotrol, Inc. Mobile Aqueous Treatment System (ATS).
nol. Although the sludge trapped in the
bag filter was found to contain pentachlo-
rophenol (34 and 170 ppm found in two
samples), the amount of sludge was so
small that adsorption of pentachlorophe-
nol on the biosolids and removal with the
suspended solids (Table 4) does not rep-
resent a significant removal mechanism.
Similarly, pentachlorophenol was not
present above the detection limit (0.2 ppb)
in any of the air samples collected from
the exhaust from the reactor chamber with
a modified Method 5 collection system
with an XAD resin trap. Therefore, it does
appear that biological degradation is, by
far, the primary means.of eliminating the
pentachlorophenol from the groundwater.
Concentrations of the various poly-
nuclear aromatic hydrocarbons measured
as part of the semivolatile fraction were
consistently below detection limits in the
incoming groundwater. Whereas the de-
tection limits were usually high (2 ppm) in
these analyses because of the high pen-
tachlorophenol concentrations in the influ-
ent, two analyses of well water during the
predemonstration testing indicated total
PAHs of 145 and 295 ppb, which would
confirm that the PAHs are not major con-
taminants in this water. Several PAHs,
including naphthalene and methyl naph-
thalene at maximum levels of 34.6 ppb
and 47.9 ppb, respectively, and others at
considerably lower levels, were found dur-
ing the modified Method 5 testing of the
air emissions from the reactor, suggesting
that some air stripping of these constitu-
ents may be occurring. The carbon ad-
sorption unit on the exhaust from the
bioreactor was successful in collecting
most of these emissions.
Small amounts of various chlorinated
dioxins were found in the effluent (<340
ng/L, using method SW8280) and, par-
ticularly, the sloughed biomass sludge,
where one sample did exhibit 1900 ng/g
of the OCDD isomer. With the exception
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Vent
Influent
Overflow
Weir
Effluent
Air Diffuser Pipe
Figure 2. BATS Reactor
of one effluent sample found to contain 62
ng/L, the 2,3,7,8-tetrachlorodioxin of pri-
mary concern was not detected in any of
the influent, effluent, or sludge samples
using high resolution GC coupled with low
resolution MS.
The incoming groundwater contained
low concentrations of several of the heavy
metals, including nickel (<91 ng/L), zinc
(<32 ng/L), copper (<25 ng/L), lead (<11
i-tg/L), and arsenic (<6.5 |ig/L). With the
exception of one sample which is believed
to be an anomaly, the concentrations of
the metals in the effluent were similar.
Acute biomonitoring with fresh water
minnows (96-hr static test) and Daphnia
magna (48-hr static test) demonstrated
that the toxic'rty observed with the incom-
ing groundwater and the influent was es-
sentially totally removed by the treatment.
LC^'s increased from an estimated low of
0.2% (groundwater/control water) for the
groundwater to more than 100% (as
calculated from results) in the treated ef-
fluent; in other words no toxicity was ob-
served with 100% treated effluent.
Costs
Estimates were provided by the vendor
for the cost of operating the pilot plant at
MacGillis and Gibbs including cost for nu-
trients, electricity, heat, labor, and caustic.
Ancillary costs incurred as part of the SITE
Demonstration program such as the bag
filter, the carbon adsorption units, and the
extensive analytical program were not in-
cluded. BioTrol also extrapolated costs to
a large scale system capable of treating
30 gpm of a similarly contaminated (-40
ppm pentachlorophenol) groundwater
based on the' demonstration study and
other information at their disposal (Table
5). As shown in the table, certain costs do
not increase at an expected linear rate.
For example, unit nutrient cost would de-
crease because of bulk purchase; opera-
tor labor cost also does not increase in
direct proportion to the size of the unit.
These costs do not include leasing or
amortization of the capital equipment,
which are approximately $2,400/mo (5 gpm
mobile), $30,000 (5 gpm skid mounted)
and $80,000 (30 gpm skid mounted), re-
spectively.
The labor cost is clearly a major com-
ponent of the total cost. In many instances,
heat input is not required; however, if heat-
ing is necessary it also is a major cost
component. Any site-specific pre- or post-
treatment requirements, such as oil/water
separation, solids removal, polishing, air
emissions control, etc., would have to be
factored into the cost calculation for that
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Blocks
Cross-Stacked
Figure 3. Corrugated Polyvinyl Chloride Media
site. Regulatory needs before or during a
remediation such as permits for wells, dis-
charge of effluent, sludge disposal, etc.
are also not included.
Applicability to other
Wastewaters
BioTrol, Inc. has carried out several
other studies as part of its development
and commercial activities related to the
BATS. Results from those studies have
also been evaluated as a means of evalu-
ating the applicability1 of the process to
other pentachforophenol-contaminated:
wastewaters as well as to other contami-
nants.
BioTrol has successfully demonstrated
- at 15 gpm - the ability of the BATS to
eliminate the benzene, toluene, xylene,
and ethylbenzene components from gaso-
line-contaminated groundwater. Benzene
was reduced from approximately 4000 ppb
to about 10 ppb. Similarly, in another
bench scale study, toluene, methyl ethyl
ketone, and tetrahydrofuran were reduced
by over 99%. In various other laboratory,
pilot scale, and commercial scale studies
summarized in the report, removals of pen-
tachlorophenol consistently averaged over
90% and the removal of other oxygenated
and chlorinated organics have been dem-
onstrated.
Conclusions
The following conclusions can be drawn
from the available information, relying pri-
marily on the SITE demonstration study
but supported by other information pro-
vided by the developer.
1. The fixed-film system effectively re-
moves pentachlorophenol from con-
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Table 1. System Parameters During Test Program
Flow
gpm
1
3
5
Avg. Temperature
CC)
gdwter toft. offl.
21
11
13
23.4
14.2
14.6
24.5
20.9
20.9
pH Avg. Dissolved O2
(s.u.) (mg/L)
infl. effl. infl. effl.
6.9-7.9
7.1-8.7
6.8-8.0
8.0-8.4
7.6-8.1
7.2-8.0
5.3
5.0
5.6
5.8
5.6
5.8
Table Z Average Pentachlorophenol Removal by the Biotrol Aqueous Treatment System
Flow
Rats
(gpm)
1
3
5
Ground-
water*
(ppm)
42.0±7.1
34.5±7.8
27.5±0.7
Effluent
(ppm)
0.13±.25
0.34±.15
0.99±.49
Removal
(%)
Average! Range
99.8
98.5
96.4
87.4-99.9+
95.8-99.8
79.3-99.4
* decrease with t'me may reflect drawdown of aquifer
| based on average of daily effluents
Table 3. Comparison of Chloride. TOC, and PCP Results.
Flow
Rale
(gpm)
1
3
5
PCP
-41.9
-34.1
-26.5
Change (delta) (ppm)
Cl, CI0 TOC,
+44.2 +27.9 -24
+40.5 +22.7 -32
+22.0 +17.6 -21
TOCC
-11.3
-9.2
-7.0
(0 - found; (c) calculated
Table 4. Average TSS Results
Flow Rate
(gpm)
1
3
5
Groundwater
(ppm)
2.5± 0.07
13 ±12.7
1.5±0.7
Effluent
(ppm)
53.6± 6.6
26.3±11.1
22.5± 9.5
TableS. Operating Costs
($/1000gal)
Cost Item
nutrients
electricity
heat
tabor
caustic
TOTAL
at 5 gpm
0.042
0.216
1.46
1.49
0.24
3.45
at 30 gpm
0.017
0.216
1.46
0.50
0.24
2.43
laminated groundwaters. Other phe-
nolics also appear to be extensively
degraded.
2. Pentachlorophenol removals of 95%
and higher are achievable with final
Pentachlorophenol concentrations
well below 1 ppm, making the efflu-
ents potentially suitable for direct dis-
charge, discharge to a POTW, or
reuse.
3. Biodegradation appears to be the
predominant mechanism for penta-
chlorophenol removal. Adsorption on
the biomass or air stripping are not
significant contributors to removal.
4. Complete mineralization of penta-
chlorophenol and other partially chlo-
rinated phenols is consistent with the
loss of TOG and the Increase in
chloride ion observed in the study.
5. Toxicity (acute) of groundwater such
as that found at MacGillis and Gibbs
is totally eliminated by the BioTrol
treatment process. !
6. The system is convenient to operate
and requires a minimum of operator
attention once acclimation has been
achieved. Use of the BioTrol fixed-
film reactor minimizes sludge pro-
duction.
7. Operating costs range from $3.45 in
a 5 gpm unit to $2.43 in a 30 gpm
unit, making the process economi-
cally attractive.
8. The process does not appear to be
adversely affected by the presence
of oil in the 50 ppm range, sus-
pended solids, metals, o& other
sources of organic carbon.
9. Based primarily on review of
BioTrol's data from other studies, it
appears that the process would be
well suited to the removal of other
organic contaminants including hy-
drocarbons, oxygenated hydrocar-
bons and even chlorocarbons from
various ground and process waters.
10. While it appears from other studies
that polynuclear aromatic hydrocar-
bons are also removed by the BioTrol
process, such a conclusion cannot
be stated from the results of this
SITE demonstration.
&U.S. GOVERNMENT PMNTING OFFICE: 19»3 • 7SWI71/80IU
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The EPA Project Manager, MaryK. Stinson, is with the Risk Reduction Enginsering
Laboratory, Edison, NJ 08837.
The complete report, entitled "Technical Evaluation Report: Biological Treatment of
Wood Preserving Site GroundwaterbyBiotrol, lnc.,"(OrderNo. PB92-110 048/AS;
Cost: $26.00, subject to change) will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
Telephone: 703-487-4650
A related report, entitled "Application Analysis Report: Biological Treatment of Wood
Preserving Site Groundwater by Biotrol, Inc. (EPA/540/A5-91/001) Is available.
The EPA Project Manager can be contacted at:
Risk Reduction Engineering Laboratory
U.S. Environmental Protection Agency
Edison, NJ 08837
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati, OH 45268
BULK RATE
POSTAGE & FEES PAID
EPA PERMIT NO. G-35
Official Business
Penalty for Private Use $300
EPA/540/S5-91/001
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