United States
Environmental Protection
Agency
EPA/540/S5-90/005
August 1990
SUPERFUND INNOVATIVE
TECHNOLOGY EVALUATION
Emerging Technology
Summary
Removal and Recovery of Metal
Ions from Groundwater
A series of bench-scale tests and
an onsite pilot scale demonstration
of Bio-Recovery Systems' AlgaSORB®
technology for the removal and
recovery of mercury-contaminated
groundwaters were conducted under
the SITE program.
The AlgaSORB® process is based
on the natural, very strong affinity of
biological materials, such as the cell
walls of plants and microorganisms,
for heavy metal ions. Biological
materials, primarily algae, have been
immobilized in a polymer to produce
a "biological" ion exchange resin
called AlgaSORB®. The material has a
remarkable affinity for heavy metal
ions and is capable of concentrating
these ions by a factor of many
thousandfold. Additionally, the bound
metals can be stripped and
recovered from the algal material in a
manner similar to conventional
resins.
This new technology has been
demonstrated to be an effective
method for removing toxic metals
from groundwaters. Metal concentra-
tions can be reduced to low parts per
billion (ppb) levels.
Optimum conditions were
determined for binding mercury to
AlgaSORB®. Conditions under which
mercury could be stripped from
AlgaSORB® were also developed.
Onsite, pilot-scale demonstrations
with a portable waste treatment
system incorporating columns
containing two different AlgaSORB®
preparations confirmed laboratory
tests. Over 500 bed volumes of
mercury-contaminated groundwater
could be successfully treated before
regeneration of the system was
required. Mercury was removed to
levels below the discharge limit of 10
ng/L.
This Summary was developed by
EPA's Risk Reduction Engineering
Laboratory, Cincinnati, OH, to
announce key findings of the SUE
Emerging Technology program that is
documented in two separate reports
(see ordering information at back).
Introduction
In response to the Superfund
Amendments and Reauthonzation Act of
1986 (SARA), the U.S. Environmental
Protection Agency's (EPA), Office of
Research and Development (ORD) and
Office of Solid Waste and Emergency
Response (OSWER) have established a
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formal program to accelerate the
development, demonstration, and use of
new or innovative technologies as
alternatives to current containment
systems for hazardous wastes. This
program is called Superfund Innovative
Technology Evaluation, or SITE.
The SITE Program is part of EPA's
research into cleanup methods for
hazardous waste sites throughout the
nation. Through cooperative agreements
with developers, alternative or innovative
technologies are refined at the bench-
scale and pilot-scale level and then
demonstrated at actual sites. EPA
collects and evaluates extensive
performance data on each technology to
use in remediation decisionmakmg for
hazardous waste sites.
This report documents the results of
laboratory and pilot-scale field tests of
dead, immobilized algal cells in a silica
gel polymer to remove heavy metal ions
from mercury-contaminated ground-
waters. It is the first in a series of reports
sponsored by the SITE Emerging
Technologies Program.
Groundwater contamination is found at
over 70% of the sites currently on the
National Priority List. Groundwaters have
been contaminated with either toxic
organic molecules or heavy metal ions, or
both. The most common means of
addressing contaminated groundwater is
extraction and treatment. Although
biological in situ treatment of
groundwaters contaminated with organics
may be possible, there is no effective
method for in situ treatment of
groundwaters contaminated with heavy
metals. AlgaSORB® was developed to
remove dilute concentrations of heavy
metals from groundwaters.
The AlgaSORB® process is based
upon the natural affinity of algae cell
walls for heavy metal ions. The sorption
medium, AlgaSORB®, is composed of a
nonliving algal bio-mass immobilized in a
silica polymer. AlgaSORB® is a hard
material that can be packed into columns
which, when pressurized, exhibit good
flow characteristics. This technology
functions well for removing heavy metal
ions from groundwaters that contain high
levels of dissolved solids, or organic
contaminants, or both.
The immobilized algal process was
tested at bench-scale and pilot-scale on a
groundwater contaminated with mercury
at levels near 1 ppm and with a total
dissolved solid content of over 11,000
ppm. The objective was to treat the
waters with AlgaSORB® so that discharge
limits of 10 ppb could be achieved.
Procedure
In the initial bench-scale tests,
mercury-contaminated groundwaters
passed through small glass columns (1.5
cm i.d. x 20 cm) containing 25.0 mL of
sorbent. An automatic fraction collector
collected effluents from the column, and
EPA Method 245.1, cold vapor atomic
absorption, determined the mercury
concentration. Once the sorbents became
saturated or leaked mercury at levels
above 10 ppb, the column was stripped
of mercury with 5 to 10 bed volumes of
1.0 M sodium thiosulfate. After water
rinsing, the column was ready for reuse.
Groundwaters collected October 4,
1989, containing 1550 ug/L mercury,
were passed through two columns (1 0
cm i d. x 37 cm) coupled in series, at a
rate of six bed-volumes per minute. Ten
bed volume fractions were collected and
analyzed for mercury. Data shown in
Table 1 are mercury concentrations in
effluents from the second column
Table 1. Test of AlgaSORB®-624
and AlgaSORB®-640 on
Mercury-Contaminated
Groundwaters
Bed Volumes
of Effluent
0-12
12-24
24-36
48-60
60-72
84-96
108-112
132-144
168-180
192-204
252-264
288-300
312-324
324-336
Effluent Hg (ug/L)
0.3
0.2
0.2
0.3
0.5
0.7
0.8
0.9
0.8
0.9
0.6
06
2.0
1.9
Onsite, pilot-scale demonstrations were
conducted with the use of a small
portable water treatment system
manufactured by Bio-Recovery Systems
for these studies. This portable unit is
designed so that columns ranging in size
from 1 to 4 in. in diameter can be placed
on the unit. For the pilot testing, 1-
diameter columns were used. Frc
laboratory experiments, it was predict
that 1 in. diameter columns woi
become saturated with mercury in 3 tc
weeks at flow rates of 10 bed volum
per hour.
One column was filled wi
AlgaSORB®-624 and another was fill
with AlgaSORB®-640. Each column hac
volume of 0.4 L. The two columns we
run in series so that groundwater. with
pH adjustment, was directed first throu'
the AlgaSORB«-624 column, and th>
through the AlgaSORB®-640 column, al
flow rate of 6 bed volumes per hoi
Effluent samples were collected from
sample port between the two columns
well as from effluent emanating from tl
second column. Effluent samples we
split into three portions. One portion w
sent to Woodward-Clyde Consultants f
immediate mercury analysis (within 12
24 hrs. of collection) Another portion w,
acid-preserved and sent to EE
Technology for mercury analysis; tt
third portion was preserved and sent
Bio-Recovery Systems for analysi
Results are reported in Table 2.
Onsite pilot-scale testing WE
conducted from November 6 1
December 1, 1989. The site was availab
for testing only from 7:00 AM-3:30 P
each day. At the end of a treatment da
the system was simply shut down ar
then restarted the next day. Flow rate
through the system was 10 bed volume
per hour.
Results and Discussion
Groundwater samples, collected ;
various times during 1989, were acidifie
to pH 2 with nitric acid in the field befoi
being sent to the laboratory. Once fr
samples were received at Bio-Recover
Systems, the solutions were neutralize
to the original pH with dilute sodiur
hydroxide. Laboratory and field studie
were complicated by the fact that, over
10-mo. period, mercury concentration
changed by an order of magnitude.
Different species of algae can b
immobilized to produce differer
AlgaSORB® resins. Since differer
bioploymers comprise the cell walls c
different algae, some species of alga
behave differently from others wit
respect to metal ion binding. Thus
different AlgaSORB®s containing differer
algal species were tested for mercur
removal from the groundwaters. Becaus
both mercury concentration and chemic;
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speciation appeared to change over the
sampling period (January through
October 1989), removal performance was
inconsistent when a single immobilized
alga was used on these waters collected
at different times.
After examining several different
AlgaSORB® preparations, two different
AlgaSORB® resins were used for final
testing. Although these two resins could
have been blended into a single column,
they were placed in two columns,
connected in series, from which effluents
samples could be taken from each
column for mercury analysis. Table 1
shows results of these experiments.
Data in Table 1 show that the two
columns arranged in series effectively
removed mercury to below 1 ppb through
passage of 250 bed volumes of mercury-
contaminated waters that contained 1550
ppb mercury.
Two columns (2.54 cm i.d. x 81 cm)
were separately filled with AlgaSORB®-
624 and AlgaSORB®-640. The columns
each had a bed volume of 400 mL and
were connected in series. Mercury-
contaminated waters were pumped
through the two columns and two bed-
volume fractions (800 mL) were collected,
split, and sent to EER Technologies,
Woodward-Clyde and Bio-Recovery
Systems for analysis. Results of onsite
pilot testing are shown in Table 2. With
the exception of the first fraction
collected, the data in Table 2 show that
over 500 bed volumes of mercury-
contaminated waters were treated before
mercury in effluents approached the 10
ppb discharge limit
Conclusions and
Recommendation
Onsite, pilot scale testing on
AlgaSORB® showed effective mercury
recovery from contaminated ground-
waters. Initial laboratory experiments
however, illustrated the dangers in
making conclusions from a single
groundwater sample. These studies
showed that not only did mercury
concentration vary over the sampling
period, but the chemical species of
mercury varied as well. Combining two
different AlgaSORB* preparations
effected mercury removal to levels below
10 ng/L.
Work done at the site indicates that a
full treatment system for mercury
recovery can be installed. Because the
chemistry of other groundwater sites will
undoubtedly differ from the one tested
here, laboratory treatability testing is
needed before the technology can be
applied at other mercury-contaminated
groundwater sites.
Table 2. Onsite Pilot Testing for Mercury Removal from Groundwaters
Mercury Concentration (ng/L)
Bed Volumes of
Effluent
7-8
85-86
163-64
229-230
289-290
313-314
343-344
379-380
415-416
449-450
467-468
503-504
533-534
587-588
Bio-Recovery
Analysis
9.5
5.3
2.1
1.4
1.8
1.9
5.5
2.0
1.8
4.9
4.0
5.8
7.7
10.5
Woodward-Clyde
Analysis
14.2
8.0
3.6
1.4
2.6
2.4
9.3
3.1
3.2
78
7.2
9.6
10.0
13.0
EER Technologies
Analysis
11
<10
<10
<10
<10
<10
10.0
<10
<10
10.0
<10
<10
<10
15
U.S. GOVERNMENT PRINTING OFFICE: 1990/748-012/20078
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The EPA Project Officer, Naomi P. Barkley, is with the Risk Reduction
Engineering Laboratory, Cincinnati, OH 45268 (see below).
The complete SITE Emerging Technologies report consists of two volumes:
Volume I "Removal and Recovery of Metal Ions from Groundwater," (Order No.
PS 90-252 594; Cost: $17.00 , subject change)
Volume II "Removal and Recovery of Metal Ions from Groundwater:
Appendices," (Order No. PB 90-252 602; Cost: $23.00, subject to change).
Both volumes of this report will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, V'A 221'61
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Risk Reduction Engineering Laboratory
U.S. Environmental Protection Agency
Cincinnati, OH 45268
United States Risk Reduction Engineering
Environmental Protection Laboratory
Agency Cincinnati OH 45268
Official Business
Penalty for Private Use $300
EPA/540/S5-90/005
000085833 PS ctIOM *GE«Ct
5sH:
CHICAGO
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