EPA
                           United States
                           Environmental Protection
                           Agency
                         Office of            EPA #540/R-00/501 a
                         Research and Development    May 2000
                         Cincinnati, OH 45268
SITE Technology Capsule
Pintail  Systems  Inc.'s
Aqueous   Biocyanide
Process
Introduction

In 1980 the Congress passed the Comprehensive Environ-
mental Response,  Compensation, and Liability Act
(CERCLA), also known as Superfund, committed to pro-
tecting human health and the environment from uncontrolled
hazardous waste sites.  CERCLA was amended by the
Superfund Amendments and Reauthorization Act (SARA)
in 1986. These amendments emphasize the long term ef-
fectiveness and permanence of remedies at Superfund sites.
SARA mandates implementing permanent solutions and
using alternate treatment technologies or resource recov-
ery technologies, to the maximum extent possible, to clean
up hazardous waste sites.

State and Federal agencies, as well as private parties, are
now exploring a growing number of innovative technolo-
gies fortreating hazardous waste. The sites on the National
Priorities List total more than 1,200 and comprise a broad
spectrum of physical, chemical, and environmental condi-
tions requiring varying types of remediation. The U.S Envi-
ronmental Protection Agency (EPA) has focused on policy,
technical, and informational issues related to exploring and
applying new remediation technologies  applicable to
Superfund sites. One such initiative is EPA's Superfund In-
novative Technology Evaluation (SITE) Program, which was
established to accelerate development, demonstration, and
use of innovative technologies for site cleanups. EPA SITE
Technology Capsules summarize the latest information
available on selected innovative  treatment and site
remediation technologies and  related issues. These cap-
sules are designed to help EPA remedial project managers,
EPA  on-scene coordinators, contractors, and other site
                    cleanup managers understand the type of data and site char-
                    acteristics needed to effectively evaluate a technology's ap-
                    plicability for cleaning up Superfund sites.

                    This capsule provides information on Pintail Systems, Inc.'s
                    Aqueous Biocyanide Process, a bioremediation technology
                    designed to treat aqueous process and waste solutions con-
                    taminated with cyanide and heavy metals.  Applicable ma-
                    trices include mine process solutions, mine drainage, tail-
                    ings effluent, groundwater, and industrial process effluents.
                    The technology consists of a proprietary biological culture
                    of microorganisms, immobilized on a porous ceramic filtra-
                    tion media as an attached growth biofilm for aqueous treat-
                    ment.  Pintail Systems, Inc. has developed a companion
                    technology for the in situ treatment of cyanide and heavy
                    metals in ores, tailings, soils and sediments.

                    A field treatability study was performed on a  cyanide and
                    metal contaminated "pregnant solution" from a gold mine
                    heap leach at the Echo Bay/McCoy Cove Mine Site, in Ne-
                    vada. Information in this capsule emphasizes specific site
                    characteristics and results of the treatability test. The cap-
                    sule presents the following information:

                       Abstract
                       Technology description
                       Technology applicability
                       Technology limitations
                       Process Residuals
                       Site requirements
                       Performance data
                       Technology status
                       Sources of additional information

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Abstract

A two and one-half month field treatability study of an inno-
vative biological treatment technology for the destruction of
cyanide and immobilization of metals from an aqueous mine
process stream was held at the Echo Bay/McCoy Cove mine
site near Battle Mountain, Nevada.

The Aqueous Biocyanide Process, developed and operated
by Pintail  Systems, Inc. of Aurora, Colorado, biologically
detoxifies cyanide and removes heavy metals from contami-
nated waste streams.  The field treatability study was jointly
sponsored by the Mine Waste Technology Program (MWTP),
Activity III, Project 5, Biocyanide, and the Superfund Inno-
vative Technology Evaluation (SITE) Demonstration Pro-
gram.

The primary  objective for the field treatability study was to
determine the effectiveness of the bioremediation process
in degrading  Weak Acid Dissociable (WAD) cyanide from a
metal laden,  high  cyanide "pregnant solution." The preg-
nant solution is the effluent  form the heap leach process
containing the extracted metals.  The secondary objective
of the study was to determine the ability of Pintail's process
to remove and  immobilize heavy metals from the pregnant
solution.

Pintail Systems, Inc.'s Aqueous Biocyanide Process uti-
lizes a specially selected and augmented consortium of mi-
croorganisms immobilized on a fixed media isolite.  The
isolite is loaded into bioreactors which can be controlled to
provide specific environments for microbial degradation and
immobilization pathways.  For this study, an aerobic
bioreactor was used  in conjunction with an anaerobic
bioreactorto  provide the desired degradation and metal im-
mobilization properties.

The field treatability study was conducted between June 11,
1997 andAugust 26,1997. During this time, the period be-
tween June 11  to July 22 was devoted to customizing and
optimizing the system to the site-specific waste characteris-
tics. Once optimized, continuous testing was performed from
July 23 and August 26.

Results from the study are summarized below:

.   The average % WAD CN reduction attributable to the
    Biocyanide process was 89.3 during the period from
    July 23 to August 26. The mean concentration of the
    feed over this period was 233 ppm, while the treated
    effluent from the bioreactors was 25 ppm.  A  control
    train, used to  detect abiotic loss of cyanide, revealed
    no destruction of cyanide (average control effluent =
    242 ppm).
.   Metals that were monitored as part of this study were
    As, Cd, Co, Cu, Fe, Mn, Hg, Ni, Se, Ag, and Zn.  Sig-
    nificant reductions were noted for all metals except Fe
    and Mn.  Average reduction in metals concentration
    after July 23 for all other metals were 92.7% for As,
    91.6% for Cd, 61.6% for Co, 81.4% for Cu, 95.6% for
    Hg,  65.0% for Ni, 76.3% for Se, 94.6% for Ag, and
    94.6% forZn. Reductions for As, Cd, Co, and Se are
    probably greaterthan calculated due to non-detect lev-
    els in  some effluent samples. A biomineralization
    mechanism is proposed forthe removal of metals from
    solution.  Biomineralization is a process in which mi-
    crobes mediate biochemical reactions forming novel
    mineral assemblages on solid  matrices.

.   The Aqueous Biocyanide  Process was operated for
    two and one-half months. During the first 42 days (June
    11 to July 22) system performance was variable, and
    occasional downtimes  were encountered. This was
    due to greatly higher cyanide and metals concentra-
    tion in the feed than was encountered during bench-
    scale  and design phases  of the  project.  Once  opti-
    mized forthe more concentrated feed, the system per-
    formed well with continuous operation for 35 days  (July
    23 to August 26). The ability to "re-engineer" the sys-
    tem in  the field to accommodate the new waste stream
    is a  positive attribute of the system.

Technology Description

The Pintail Aqueous Biocyanide Process is a bioremediation
technology forthe treatment of cyanide and metals in pro-
cess and waste water streams. The technology utilizes a
proprietary method for identifying, isolating, and growing a
specialized consortium of microorganisms designed to treat
the specific contaminants and characteristics of the aque-
ous stream. Pintail uses microorganisms isolated from the
environment of the aqueous stream and, if necessary, can
augment the culture with microorganisms from their collec-
tion of microorganisms. The microorganisms in Pintail's
collection were recovered from a wide variety of extreme
environments and were isolated and adapted to treat spe-
cific contaminants. The optimized microbial consortium is
then immobilized on a porous ceramic filtration media as an
attached growth biofilm. Dependent on the application, one
or more sets of microbial consortiums can be immobilized
on separate media and used in tandem to achieve the treat-
ment of complex waste streams.

Forthe current application, both aerobic and anaerobic mi-
crobial pathways were designed into a treatment train to
degrade the cyanide and immobilize metals from the pro-
cess stream.  As part of this treatability design, a control
train was used to determine abiotic losses of cyanide and
metals.  The system design is depicted in Figure 1 and de-
scribed below.

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Dual identical treatment trains are used in an alternating on-
off mode.  The reactors are operated as a plug-flow reactor
system. The system is operated in 24 hour alternating cycles
of treatment or reinoculationforthe two biotreatment trains.
A typical complete 48 hour operation cycle for one of the
biotreatment trains would include a 24 hour treatment pe-
riod, followed by a four to five hour flush of inoculation  bac-
teria discharging to the drain, followed by a 20 hour bio-
inoculation.

Cyanide and metals contaminated solutions from the mine
are fed to the reactor system which contains both an aero-
bic treatment cycle and an anaerobic reactor. Optical level
sensors on each aerobic tank turn a pump on and off to
either transfer process solutions to the anaerobic reactors
or to recycle aerobic bacteria/nutrient solutions back to the
aerobic culture tank.

The treatment bacteria  are maintained as live cultures in a
cess solutions from the anaerobic tanks before recycling
inoculation solutions to the culture tank. After drawing down
during the flush cycle every day, the tank is topped off with
fresh water.

Technology Applicability

The Aqueous Biocyanide Process is applicable to process
and waste streams containing cyanide alone, or in combi-
nation with heavy metals. For the application tested in this
study, the process was used to demonstrate its utility as a
process to treat cyanide and metal contaminated process
and waste streams derived from precious metal recovery.
In these applications, cyanide is used as a lixiviant to ex-
tract and recover precious metals such as gold and silver
from heap and vat leach mining practices. The spent solu-
tions typically contain high levels of cyanide and heavy met-
als which  must be treated prior to  discharge.  Cyanide is
               Pregnant Feed
 Aerobic Culture Tank
                            Effluent
                           Discharge
                                             Anaerobic Tank   Anaerobic Tank
                                             Anaerobic Tank   Anaerobic Tank
                                                                             Anaerobic Culture Tank
                    Aerobic Inoculation
                          Cycle

   Figure 1.  Dual train Aqueous Biocyanide System design depicting on-off mode. Top train is treating while
   bottom train is being re-inoculated.	
continuous culture system.  An aerobic culture and an
anaerobic culture are maintained by scheduled nutrient and
stock culture addition and are circulated through the aero-
bic and anaerobic biomass during the twenty-four hour flush
and inoculation cycle and are returned to the bioculture tanks
in a continuous loop.

Anaerobic cultures are applied to the anaerobic culture train
during flush and  inoculation cycles alternating between the
biotreatment trains on a daily basis.  A flush cycle of 4-5
hours is run between the treatment cycle and  the full re-
cycle inoculation. The flush cycle serves to discharge pro-
typically complexed with a wide variety of metal species and
sulfur causing the cyanide to be environmentally persistent
and difficult to be destroyed by natural processes. In addi-
tion, the effluents may contain high levels of metals and other
constituents which may impact total water quality.

According to Pintail, the process is capable of treating all
forms of cyanide, as well as treating heavy metals in the
effluent. Standard processes fortreating cyanide from heap
and batch leach processes use peroxide to oxidize cyanide.
The advantages of the Aqueous Biocyanide Process, as

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compared to peroxide treatment, are:

.   The biocyanide process is a biological treatment tech-
    nology and  does not utilize any hazardous or reactive
    chemicals.
.   The  process is  inexpensive to operate once  the
    bioreactors  are constructed.  The only consumables
    used are nutrients and bacterial cultures.
.   The process treats heavy metals and may be engineered
    to treat other water quality impacting constituents. This
    eliminates the need to bring other technologies on-site.
.   The Biocyanide Process may be engineered to recover
    precious metals (gold and silver) from waste streams
    during operation.  This feature can offset costs during
    waste treatment.

In addition to mining wastes, the Aqueous Biocyanide Pro-
cess may be used to treat cyanide contaminated wastewa-
ter from other industrial processes as well as contaminated
groundwater containing heavy metals.  Applicable waste-
water streams may include electroplating wastes and efflu-
ents from spent aluminum pot liners. The biotreatment pro-
cess can also be applied to the treatment of groundwater
and surface water containing heavy metals and nitrates.

Pintail Systems, Inc.  has also developed and applied, at
full-scale, a  biocyanide process for the in situ treatment of
cyanide and heavy metals in  spent ore and mine tailings. In
the Spent Ore Biocyanide Process, bacterial solutions and
nutrients are injected  into the subsurface where  entrained
cyanide is destroyed  and heavy metals are immobilized.
Pintail has shown at  other sites that this process greatly
reduces rinsing of heap leach pads, and can minimize the
impact of acid mine drainage from tailings  and spent ore.

Technology Limitations

According to Pintail, proprietary colonies of bacteria or iso-
lated native bacteria can detoxify WAD cyanide as high as
500 ppm and effectively treat aqueous waste streams con-
taining soluble metals as high as 400 ppm.  The bacteria are
able to accommodate fluctuations in contaminant concen-
trations, however large variations in feed concentrations
could be detrimental to the bacteria. A continuously mixed
influent storage tankwould eliminate fluctuations in contami-
nant concentration.

In addition, cool water temperatures (35-45° F) could slow
down biodetoxification and  biomineralization.  Water tem-
peratures above 85° F could also be harmful to the bacteria.

Process Residuals

The primary  residual generated from the Pintail process is
the solid media containing primarily dead  bacteria and im-
mobilized metals.  This waste material can be stored in 55
gallon drums before being shipped off-site for disposal. The
developer believes that the precious metals which are fixed
on the support media can be separated and recovered and
sold as a commodity.

Site Requirements

The Pintail process,  as tested, requires an enclosed level
20 foot by 80 foot area capable of supporting the bioreactor
and all necessary support equipment. Once the piping and
pumps are installed, the system can be operational within
three weeks. According to Pintail, the bacteria can be grown
and be inoculated onto the porous ceramic media and accli-
mated to the waste stream in two weeks.

The technology utility requirements are minimal and consist
of the following:

.   110 volt - single phase power
.   potable water
Potable water should be available for field laboratory ana-
lytical procedures and process make up water as well as
personnel decontamination. Storage tanks should be avail-
able for holding the treated water prior to discharge. A stor-
age shed can be used to store nutrients such as ammonia
and nitrogen.

Performance Data

Pintail Systems,  Inc.'s Aqueous Biocyanide Process was
used to treat a pregnant solution containing cyanide and
heavy metal contaminants.  The two and one-half month
treatability test took place at the Echo Bay/McCoy Cove mine
site near Battle Mountain, Nevada between June 11,1997
to August 26, 1997.

The original system was designed and optimized based on
the plan to treat a "barren solution" containing WAD cyanide
concentrations in the tens of ppms and  relatively devoid of
heavy metal contaminants.  However, upon mobilization of
equipment to the site, the test feed was changed to a "preg-
nant solution" containing WAD cyanide  concentrations be-
tween 250 to 350 ppm, and  significant concentrations of
heavy metals. Since the system was designed for the bar-
ren solution, significant redesign of the system on-site was
necessary to treat the pregnant solution.  Therefore, the
period between June 11 to July 22 was devoted to custom-
izing and optimizing the system to the pregnant solution
characteristics.  Once optimized, continuous testing was
performed between July 23 and August  26. Therefore, the
period between July 23 and August 26 will be used for per-
formance assessment purposes.

The test system consisted of two identical treatment trains

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(T-100 and T-200), and a control train (T-300). The control
train was used to determine if any losses of cyanide or met-
als occurred due to abiotic mechanisms.

Four sample streams were evaluated as part of this treat-
ability study. Streams included; (1) an influent stream des-
ignated as the "process feed" or "pregnant feed," (2) a con-
trol  effluent from the control train, (3) an effluent from the
aerobic treatment cycle, and (4) the effluent from the en-
tire treatment process. Concentrations of cyanide from the
influent stream were compared to the treated effluent to de-
termine system efficiency. Results from the aerobic efflu-
ent, as compared to the system effluent, were used to de-
termine operating efficiencies of the individual aerobic and
anaerobic segments.

Analyses for weak and dissociable (WAD) cyanide were
performed by two different methods. On-site field analyses
were performed on a daily basis using a Perstorp analyzer:
a ligand exchange/flow injection amperometric method of
analysis.  Several  samples, but not all field samples, were
also analyzed by a laboratory distillation procedure; Stan-
dard Method 4500 CN.I. Total cyanide was also performed
on samples submitted to the laboratory.  Metals analysis of
the  process feed, treated effluent, and control effluent were
performed on three composited samples taken each week.
The samples were analyzed for the following metals: As,
Cd, Co, Cu, Fe, Mn, Hg, Ni, Se, Ag, and Zn.
Cyanide Destruction

Table 1 summarizes WAD cyanide results from the study,
and Figure 2 graphically depicts process efficiency during
the performance assessment period as measured by WAD
cyanide (field).
Table 1.  Average WAD CN (mg/L) from 7/23 to 8/26.

Field
Analysis
Lab
Analysis
Influent
233 + 8
n=27
213 + 44
n=16
Control
Effluent
242 + 22
n=27
231 + 24
n=16
Aerobic
Effluent
160 + 30
n=27
Not
Measured
Effluent
25 + 18
n=27
23 + 17
n=16
Average
%
Red.
89.3 %
89.2 %
Note: the value after+ is the standard deviation; n is the number of samples
analyzed
Results from the study demonstrate that, once optimized,
the Aqueous Biocyanide Process was able to consistently
reduce WAD cyanide by approximately 90%, based on an
average influent value of 233 ppm and an average effluent
350 -
300 -
250 -
200 -
S
Q_
Q_
150 -
100 -
50 -
0 -
7/1 £
Fi
WAD Cyanide
(Performance Assessment Period - 7/23 to 8/26)

Control A
Ğ-— -v A AV- *
^\\'f\ / \ \ ^
Fee^ >? Y X'^^^^^^
ff • ^
iET7\7^^3 .A
V * V" "V
Effluent .^X
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•- • • *• • *
197 7/24/97 7/29/97 8/3/97 8/8/97 8/13/97 8/18/97 8/23/97 8/28/97
gure 2. WAD CN concentrations overtime.

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value of 25 ppm. Furthermore, the WAD cyanide levels in
the control effluent are statistically indistinguishable from
influent concentrations, indicating that the biological system
was responsible for the cyanide destruction.

Analyses for WAD cyanide were also performed on samples
taken after the Aerobic Treatment Cycle. The average WAD
cyanide concentration during the period between July 23
and August 26 was 160 ppm. This represents an average
reduction in WAD cyanide of approximately 31% attribut-
able to aerobic respiration processes.

Pintail offers the following explanation concerning the mecha-
nisms of WAD Cyanide degradation in their treatment sys-
tem:

.   In the Aerobic Treatment Cycle, the  microorganisms
    directly metabolize cyanide.  The aerobic microorgan-
    isms can metabolize the more easily degradable metal-
    cyanide complexes such as  Zn-cyanide. Degradation
    rates are relatively rapid. This phase reduces the toxic-
    ity load to the anaerobic system.

.   In the Anaerobic Treatment Cycle, the  microorganisms
    utilize cyanide as a co-metabolite. Degradation  rates
    are relatively slow.  Reduction of the more strongly
    complexed fraction of the WAD cyanide occurs.

.   The combination of the aerobic/anaerobic system al-
    lows forthe rapid destruction of easily degradable WAD
    cyanide in the aerobic phase as a pretreatment or con-
    ditioning step, in order to increase the efficiency of the
    slower anaerobic phase of the treatment.

Metals Removal

In addition to testing the cyanide destruction capabilities of
the Aqueous Biocyanide Process, the system was sec-
ondarily evaluated for its ability to remove metal species
from the pregnant feed solution.  Table 2 presents a re-
view of the metals  data during the performance assess-
ment period of the project.  Figures 3 to 6 illustrate the
effectiveness of the removal process for several select
metals.   The results from  the analyses indicate that the
process was  able to immobilize and remove significant
quantities of heavy metals from the process feed. Specifi-
cally, the metals arsenic, cadmium, mercury, and zinc ex-
hibited reductions over 90%. Furthermore, the removal ef-
ficiency of these metals were consistent overtime as de-
picted in Figures 3 to 6.  The metals iron and manganese
exhibited apparent  increases in the effluent as compared
to the feed. The apparent  increase is probably due to in-
puts from process amendments in the form of humates.
These metals are generally considered to be environmen-
tally benign and do not add to the overall level of contami-
nation.

The process of metals removal during cyanide detoxifica-
tion has been observed from other studies performed  by
Pintail. The mechanism involves the formation of biologi-
cally   mediated   neo-mineral   phases,   termed
biomineralization.    Biomineralization is the  process  by
which microorganisms catalyze and mediate inorganic re-
actions. A biomineral is defined to include both biologi-
cally formed authigenic minerals (pyrite, etc.) and com-
plex bio-stabilized materials that are often clay- or gel-like
(Fe,AI) silicates, sulfides and oxides of variable composi-
tion that are presumed to be thermodynamically metastable
phases. Formation of biominerals on the solid media within
the reactors removes the soluble metal contaminants from
the aqueous phase and immobilizes them into a more stable
mineral phase.  This is preferable  to ion exchange reac-
tions in which metals are not covalently bonded to the sub-
strate and can desorb.
 Table 2. Average metals Gug/L) after 7/23.
Analyte
Arsenic
Cadmium
Cobalt
Copper
Iron
Manganese
Mercury
Nickel
Selenium
Silver
Zinc
Influent
361 .3+
5.8
23.3+
4.4
121.2+
49.0
133,016.7+
30,286.7
1 ,409.7+
848.59
12.2+
9.0
164.0+
13.3
1596.7+
102.7
227.3+
56.6
940.8+
774.5
8,597.7+
1,604.3
Control
339.2+
12.9
21.5+
2.5
139.2+
75.6
136,250.0+
30,626.4
803.7+
319.8
3.7+
2.2
139.2+
24.6
1646.7+
26.6
228.5+
18.5
534.5+
367.1
8,573.3+
926.2
Effluent
26.3+
13.7
<1.95
46.5+
12.9
24,733.3+
14,027.6
1 ,473.5+
614.58
69.8+
30.2
7.2+
4.1
559.3+
221.3
53.9+
45.2
51.3+
87.7
465.0+
194.4
%
Reduction
92.7
>91.6
61.6
81.4
-4.5
-470.9
95.6
65.0
76.3
94.6
94.6

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450 -,

400

350

300

250

200

150

100

 50
                  Arsenic
Effluent
  8/3/97
          8/8/97
                  8/13/97    8/18/97

                     Figure 3
                                  8/23/97   8/28/97
30 -,
nc
on
a iĞs-
S 1b
m -


Cadmium
tnz^T^^^^
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Effluent

8/3/97 8/8/97 8/13/97 8/18/97 8/23/97 8/2&
Figure 4
200 -,
180 -

•\AT\
-ion
.Q
Q. mn -

fin -

on

Mercury
Feed __^
*,^— — * XT 	 * 	 *^^_
A^ Control ^^^ ^^-4^^^
— 	 ^~~~--—
A



Effluent
•- 	 " 	 " 	 * • • ~"
8/3/97 8/8/97 8/13/97 8/18/97 8/23/97 8/281'.
Figure 5
                                                              Zinc
12000 n

10000

 8000
                                       g- 6000
 4000

 2000

   0
                                                      Feed
                                                  Control
                                                                  Effluent
                                            8/3/97    8/8/97   8/13/97   8/18/97

                                                                 Figure 6
                                                                             8/23/97    8/28
                                                   System Operability

                                                   The Aqueous Biocyanide Process was operated  for two
                                                   and one-half months. During the first 42 days (June 11 to
                                                   July 22) system performance was variable, and occasional
                                                   down-times were encountered.  This was due to greatly
                                                   higher cyanide and metals concentration  in the feed than
                                                   was encountered during bench-scale and design  phases
                                                   of the project.

                                                   Once optimized for the more concentrated feed, the sys-
                                                   tem performed well with continuous operation for 35 days
                                                   (July 23 to August 26).  Specific process modifications in-
                                                   cluded: (1) Periodic flushing of the anaerobic culture tank
                                                   with clean waterto remove built up levels of WAD cyanide;
                                                   and (2) Adding additional tankage volume on the anaero-
                                                   bic system to increase residence time. These processes
                                                   significantly improved the levels and consistency of WAD
                                                   cyanide degradation. The ability to "re-engineer" the sys-
                                                   tem in the field to accommodate the new waste stream is a
                                                   positive attribute of the  system.

                                                   One potential area of improvement would be to design a
                                                   system that would minimize the channeling of fluids through
                                                   the media. A common  problem  in many fixed media sys-
                                                   tems is the  development of channels through  preferred
                                                   pathways in the media.  This greatly reduces the available
                                                   surface reaction area and  reduces the efficiency of the
                                                   system.  There is some evidence that channeling did oc-
                                                   cur during the field tests.

                                                   Technology Status

                                                   Biotreatment processes for heap, tailings and process so-
                                                   lution detox have been  proven at other mine  sites  in a va-
                                                   riety of environments. Biological processes are both site-
                                                   specific and waste-specific and must be individually engi-
                                                   neered and tested for each mine waste. Successfully adapt-
                                                   ing treatment bacteria to the spent ore environment is a
                                                   key to developing successful bioremediation  potential.
                                                   Working with a biotreatment population that has been spe-

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specifically adapted to the ore and augmented to improve
cyanide metabolism insures that biotreatment will be ef-
fective.

Pintail  has developed biological detoxification processes
for the decomposition of cyanide and has applied them at
several gold mines. The following case studies have been
provided by Pintail Systems, Inc. The information and data
contained within these case studies are not associated or
validated by the USEPA SITE program.

Hecla Yellow Pine Mine

The first full-scale demonstration of in situ biotreatment
processes  took place at the Yellow Pine Mine near Yellow
Pine, Idaho. Approximately 1.3  million tons of agglomer-
ated oxide  ore were treated. The goals of the project were
to reduce WAD cyanide to 0.2 mg/L in leachate solutions,
treat the source of the cyanide in the ore, and enhance
gold production during detoxification operations. Further-
more, the site was a challenge to biotreatment processes
due to low solution temperatures and extreme cold weather
conditions  throughout the operating season.

Results demonstrated complete cyanide detoxification (<
0.1 mg/L WAD cyanide) after a 5-month treatment period.
In comparison, treatment time estimates for conventional
chemical treatments (peroxide and sulfur dioxide/air) sug-
gested two to four operating seasons for complete detoxi-
fication.
Disclaimer

While the technology conclusions presented in this report
may not change, the data have not been reviewed by the
EPA Quality Assurance/Quality Control office.
Sources of Further Information:
EPA Project Manager
Patrick J. Clark
U.S EPA
National Risk Management Research Laboratory (NRMRL)
26 W Martin Luther King Jr. Dr.
Cincinnati, OH 45268
(513)569-7561

Pintail Project Manager
Leslie Thompson
Pintail Systems, Inc.
11801 East 33rd Avenue, Suite C
Aurora, Colorado 80010-1454
(303) 367-8443
A secondary benefit of the biotreatment process was an
enhanced gold production above predicted recoveries for
water rinse operations. Biological solutions catalyze sev-
eral biooxidation and biomineralization reactions that con-
tribute to enhanced gold recovery.

Cyprus Copperstone Mine

An in situ cyanide detoxification was completed at the
Cyprus Copperstone Mine located  near Parker, Arizona.
At this mine, 1.2 million tons of ore were biologically treated
over a 70 day period. The goal was to  reduce WAD and
total cyanide from 30 to less than 0.2 mg/L in heap leachate
solutions.
The rapid treatment (0.3 tons of solution per ton of ore)
was attributable to high temperatures (80 to 90 degrees F)
in the process solutions.  Both  WAD and total cyanides
were reduced to less than 0.2 mg/L.

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