xvEPA
                             United States
                             Environmental Protection
                             Agency
EPA/540/S-93>!504
September 1993
                            SUPERFUND INNOVATIVE
                            TECHNOLOGY EVALUATION
                             Emerging Technology
                             Summary

                             Electro-Pure Alternating Current
                             Electrocoagulation


                             Naomi P. Barkley, Clifton Farrell, and Trade Williams
                               The Superfund Innovative Technol-
                             ogy Evaluation (SITE) Program was au-
                             thorized as part of the 1986 amend-
                             ments to the  Superfund legislation. It
                             represents a  joint effort between the
                             U.S. Environmental Protection Agency's
                             (EPA) Office of Research and Develop-
                             ment and Office  of Solid Waste and
                             Emergency Response. The program is
                             designed to assist and encourage the
                             development of waste treatment tech-
                             nologies that would contribute innova-
                             tive solutions to our hazardous waste
                             problems. Under  the Emerging Tech-
                             nology portion of the SITE Program, a
                             2-yr research  effort was conducted by
                             Electro-Pure Systems, Inc., to evaluate
                             the technical  and economic feasibility
                             of alternating current electrocoagulation
                             (ACE) for remediation of aqueous waste
                             streams at Superfund sites.
                                The ACE Technology introduces low
                             concentrations of nontoxic aluminum
                             hydroxide species into the aqueous
                             media by the electrochemical dissolu-
                             tion of aluminum-containing electrodes
                             or pellets. The aluminum species that
                             are produced  neutralize the electrostatic
                             charges on suspended material and/or
                             prompt  the coprecipitation of certain
                             soluble ionic species, and thereby fa-
                             cilitate their removal.
                               Electrocoagulation has been demon-
                             strated to enhance the filtration and de-
watering rates for solids removed from
an effluent;  such  enhancements are
prompted by growth in the mean par-
ticle size from typically <0.3 p.m in di-
ameter to as much  as 150 |xm, depend-
ing on the degree of electrocoagulation.
Significant reductions in the total sus-
pended solids (TSS) loading of particu-
late slurries and in the concentrations
of metals (lead, copper, zinc, chromium),
fluorides, and phosphates from aque-
ous streams can be achieved under cer-
tain pH conditions. Treatment does not
entail adding  chemicals (polymers,
metal salts, polyelectrolytes) whose ac-
cumulation might inhibit reuse of the
effluent as process water. Rather, the
insoluble aluminum hydroxide result-
ing from electrocoagulation may be re-
moved by standard filtration practices.
  This  Summary  was developed by
EPA's  Risk Reduction  Engineering
Laboratory, Cincinnati, OH, to announce
key findings of the SITE Emerging Tech-
nology Program that is fully docu-
mented in a journal article (see order-
ing information at back).

Introduction
  Chemical coagulation has been used
for decades to destabilize colloidal sus-
pensions and to effect precipitation of
soluble metal species as well as* other
inorganic species from aqueous streams,
                                                                            Printed on Recycled Paper

-------
thereby permitting their removal through
sedimentation or  filtration.  Alum, lime,
and/or polymers have been the chemical
coagulants used. These processes, how-
ever, tend to generate large vplumes of
sludge with a high bound-water content
that can be slow to filter and  difficult to
dewater. These treatment processes also
tend to increase the total dissolved sol-
ids content of the  effluent, making it un-
acceptable for reuse within industrial ap-
plications.
  The  ACE  Technology was  originally
developed  in the  early 1980s to  break
stable aqueous suspensions of clays and
coal lines produced in the mining indus-
try.  Traditionally,  these effluents were
treated with conventional techniques that
made use of organic polymers and inor-
ganic salts to agglomerate and enhance
the removal of the suspended materials.
This ACE Technology  was developed to
simplify  effluent treatment,  realize cost
savings, and facilitate recovery of fine-
grained coal.
  ACE Technology is based upon  colloi-
dal chemistry principles-principles using
alternating electrical power and electro-
phoretfc metal hydroxide coagulation. The
basic mechanism for the technology is
electroflocculation wherein small quanti-
ties  (generally  <30 mg/L) of  aluminum
hydroxide species are introduced into so-
lution to facilitate flocculation. Electrofloc-
culation causes an  effect similar to that
produced by the addition of chemical co-
agulants such as aluminum or ferric sul-
fate. These cationic salts destabilize col-
loidal suspensions by neutralizing nega-
tive  charges  associated  with these par-
ticles at  neutral or alkaline pHs. This
enables  the  particles to come together
closely enough to agglomerate under the
influence of  van der Waals  attractive
forces. See Figure  1  for the ACE basic
process flow.
  Although the  electroflocculation mecha-
nism resembles chemical coagulation in
that  cationic  species are responsible for
the neutralization of surface charges, the
characteristics  of the electrocoagulated
floe differ dramatically from those gener-
ated by chemical  coagulation.  An
electrocoagulated floe tends to contain
less  bound water, is  more shear resis-
tant, and is more readily filterable.
  Application of an AC  electric field to
the electrodes  induces dissolution of the
aluminum and formation of the polymeric
hydroxide species. Charge neutralization
and  particle  growth  are initiated within
the electrocoagulation cells and continue
following discharge of the aqueous me-
dium from the apparatus.  (In this way,
product separation into solids, water, and
oils may be achieved.)
  The ACE Technology was tested  us-
ing two designs of the ACE Separator™:
(1) a parallel electrode unit  in which a
series of vertically  oriented  aluminum
electrodes form a series of  monopolar
electrolytic cells through which the efflu-
ent passes and (2) a fluidized bed unit
with  nonconductive  cylinders equipped
with  nonconsumable metal electrodes be-
tween which  a turbulent fluidized bed of
aluminum alloy pellets is  maintained. In
the fluidized bed unit, introduction of com-
pressed air  into  the electrocoagulation
cells assists  in maintaining the turbulent
fluidized bed and  in enhancing the alu-
minum dissolution efficiency by increas-
ing the anodic surface area. Typically,
the  fluidized  bed  unit dissolves alumi-
num  at  least one order of  magnitude
more  efficiently than does the parallel
electrode unit.
                                                                  Gas Outlet
                Influent Liquid
 Figure 1.  Schematic of an ACE Separator* used in alternating current electrocoagulation.

-------
  Electrocoagulation operating conditions
are highly dependent on the chemistry of
the aqueous medium; especially conduc-
tivity. Other influent characteristics such
as pH, particle size, and chemical con-
stituent concentrations will influence op-
erating conditions. Treatment  generally
requires application of low voltage (<150
VAC) to the electrocoagulation cell elec-
trodes; current usage is typically  1 to 5
amp-min/L. The flow rate of the aqueous
medium  through  an  electrocoagulation
cell depends on the solution  chemistry
(conductivity), the nature of the entrained
suspension or emulsion, and the  extent
of electrocoagulation required to achieve
the treatment objective. Retention times
as short as 5 sec are sometimes sufficient
to break a suspension. Electrocoagulation
may be accomplished  in a single pass or
multiple passes (recycle mode).  In the
fluidized  bed unit, a mechanical  scrub-
bing  action  is  created within  the
electrocoagulation cell—an action that re-
duces buildup of impermeable oxide coat-
ings on  the aluminum  pellets and the
inherent  loss of efficiency that would re-
sult. Depending on system configuration,
maintenance of the apparatus is limited
to periodic replenishment of the  alumi-
num fluidized  bed material and/or elec-
trodes. For most applications, pellets for
the fluidized bed unit can be  produced
from recycled  aluminum scrap or  bever-
age containers. Where sludge reclama-
tion is the objective, however, the use of
higher quality  pellets is  required to  re-
duce the introduction of impurities into
the sludge.
  This summary describes the research
effort associated  with bench-  and pilot-
scale testing of various surrogate waste-
waters for determining the optimum op-
erating  conditions,  treatment  effective-
ness, and cost of treatment.

Experimental
  EPA's SITE  Program research entailed
testing the ACE Technology (in both the
parallel electrode and fluidized bed sys-
tem configurations) on various surrogate
wastes containing emulsified diesel fuel,
metals, and clays. The wastes were pre-
pared to resemble those of leaking, un-
derground storage tanks and soil wash-
ing operations. The  primary testing ob-
jective of such testing was to establish
optimum operating conditions for the ACE
Separator™ to  break the oil/water emul-
sion and achieve reductions in clay sus-
pended solids  and soluble metal pollut-
ant  loadings.  Experiments were con-
ducted on'surrogate wastes prepared by
mixing 0.2 to 3.0 wt. % of the -230 mesh
(clay and silt) fraction of the EPA's Syn-
thetic Soil Matrix (SSM) with 0.5 to 1.5
wt. % Number 2 diesel fuel, with 0.05 to
0.10 wt. % of an emulsifier (Titon-100X*
or Alconox soap), and with from 10 mg/L
to 100 mg/L of one or more of the follow-
ing contaminants: copper, nickel, zinc,
orthophosphate, or fluoride. The pH of
each surrogate mixture was adjusted with
either sodium  hydroxide or calcium ox-
ide to the desired value (5, 7, or 9) and
the conductivity raised to  roughly 1200
microSiemens per centimeter (u.S/cm) to
1500 p,S/cm with sodium chloride to simu-
late values expected in nature.
   Initially,  bench-scale  electroco-
agulation experiments using the  parallel
electrode  unit were conducted  on five
aqueous-based systems that included a
metals mixture, a clay suspension, a die-
sel fuel emulsion, a soluble organic solu-
tion, and  a diesel  fuel/soluble  organic
emulsion. The  operating conditions de-
termined during the Year One SITE work
effort were used as the  conditions for
these tests. Optimum treatment time was
established by examining  the trend in
contaminant loadings as  a function of
treatment time. To  compare the results
with  conventional treatment processes,
aliquots of each surrogate  stock solution
were treated  with alum. Sufficient alum
was added to give the aluminum equivalent
to that introduced in the electrocoagulation
experiments.
   During the  Year Two investigations,
operating difficulties, persistent electrode
coating and fouling, and low efficiencies
of aluminum generation prompted includ-
ing  the  alternative,  fluidized-bed,
electrocoagulation cell design in the re-
maining bench- and  pilot-scale testing
program. Three phases of  laboratory ex-
periments were undertaken to evaluate
both electrocoagulation units: (1) prelimi-
nary screening experiments  to  demon-
strate the feasibility of reducing the con-
centration of  each metal,  (2) matrix ex-
periments to define the most opportune
retention time and current (or current den-
sity), and (3) optimization experiments to
define other ACE Separator™ operating
parameters to  achieve the most cost-
effective removaj conditions. The pH was
adjusted to 5, 7, or 9 and the conductiv-
ity raised to approximately 1200 |j,S/cm
with  sodium chloride. The conductivity of
some surrogate wastes was increased to
approximately 3000 u.S/cm and subjected
* Mention of trade names or commercial products does
 not constitute endorsement or recommendation for
to electrocoagulation. Surrogate wastes
subjected to these experiments included
the five aqueous  systems  described
above as well as surrogate wastes con-
taining  individual constituents  such  as
nickel, zinc, copper, fluoride,  and phos-
phate.
  Pilot-scale tests were performed by us-
ing both the parallel and fluidized bed
configurations of the ACE Separator™. A
12-hr experiment using the ACE Fluid-
ized Bed Separator™ was conducted on
208-L batches of surrogate waste solu-
tion containing 0.2 wt % SSM fines, 0.5
wt % diesel fuel,  0.05 wt % Alconox
surfactant,  and  10  mg/L  each of Cu2+,
Zn2+, PO43~, F", and Ni2*, and whose con-
ductivity and pH  had been  raised to 1200
|j.S/cm and  7, respectively. This surro-
gate was recycled through a 4-in.- diam-
eter, Schedule 80, PVC pipe,  24-in.-high
pilot-scale ACE  Separator™,  which was
equipped with two  Type 316 stainless-
steel electrodes (24 in. high, 2.5 in. wide)
and whose  interior was filled with 8 to
+16  mesh  aluminum pellets. The  unit
was powered at  a constant 20 amp, and
the voltage was allowed to vary  as the
electrocoagulation treatment progressed
over the 12-hr period. In this experiment,
the flow of the surrogate solution through
the ACE Separator™ was varied from 1
to 6 gpm and the quantity of compressed
air introduced into the solution feed line
ranged  up  to a maximum of  10 psig.
Samples of  the  surrogate solution were
collected at various times throughout the
experiment to document the rate  of alu-
minum ion generation and  the reductions
in /concentration of the metal  contami-
nants, chemical  oxygen demand (COD),
and TSS.
  In a similar pilot-scale test using the
parallel  plate  unit,  the surrogate waste
was composed  of essentially the same
constituents as that for the fluidized bed
experiment.  The notable changes were
that the conductivity of the solution was
increased to approximately 3,000 |xS/cm
and no fluoride salt was added. The other
operating parameters were based on re-
sults obtained from the bench-scale tests.
The aluminum generation  and consump-
tion  rates and the electrical  power  re-
quired to effect acceptable phase sepa-
ration as well  as contaminant reductions
were  monitored.
  Throughout the various  phases of the
experimental  program,  samples  of the
treated  effluent  were collected  and  al-
lowed to settle for 30 min. The supernate
was removed and analyzed. The subnate,
containing the settled  floe, was filtered
and the filtrate and  filter cake analyzed.

-------
Results and Discussion

Optimum Operating Conditions
  Optimum operating conditions for the
parallel electrode unit were developed
from these  studies (Table 1). These con-
ditions served as the basis for the sub-
sequent pilot-scale tests.
  Optimum operating conditions for par-
allel electrode unit as a result of bench-
scale tests were electrode spacing 0.5
in.; current, 4 amps; retention time, 3 to
5 m!n; frequency, 10 hertz; and fully sub-
merged.
  Similarly, based  on the bench-scale
testing of the fluidized  bed design, the
optimum operating conditions established
were electrode spacing, 1-in.; aluminum
pellets size, 8 to +16 mesh; and, current,
20 amps.

Treatment Effectiveness
  Based upon bench-scale experiments
conducted on the EPA surrogate wastes,
the following summarizes the findings:
  • When compared with alum treatment,
     etedrocoagulation provided approximately
     83% less sludge volume arid a 76%
     improvement in filtration rate
  • For the fluidized bed configuration,
     aluminum or stainless  steel may be
     used as electrode material  in the
     system, with comparable results
  •  With both increased  frequency  for
     the AC and increased retention time,
     the  agglomerated particles  tend  to
     disaggregate.
   Pilot-scale tests were conducted with
the use of  both the parallel and fluidized
bed   configurations  of  the  ACE
Separator™ on a 3% soil slurry contain-
ing roughly 50% clays,  1.5% diesel fuel,
and  0.1%  of a  strong  surfactant.
Electrocoagulation reduced the TSS (222
mg/L to 4.5 mg/L) and total organic car-
bon (TOO) (130 mg/L to 6.6 mg/L). Cop-
per was reduced by 72%, cadmium  by
70%, chromium by 92%, and  lead  by
88%. No appreciable change in total sol-
ids  (TS) loadings  in the supernate re-
sulted from electrocoagulation.
 Table 1. OptimumOperatingCondltionsforPar-
         a/fe/ Electrode Unit Based on Bench-
         Scale Tests
 Parameter
                             Value
 Current
 Electrode Spacing
 Retention Time
 Frequency
 Submergence
4 Ampere
0.5 Inches
3 to 5 Minutes
10 Hertz
Fully Submerged
  Particle size was enhanced by the clay
fraction as a result of electrocoagulation.
The mean particle diameters of the ACE
Separator™ treated particulates,  both  in
the supernate and  the filtrate (188 u,m
and 230  u.m,  respectively), increased by
a factor  of approximately 85  and 105,
respectively,  over  that in  the original
slurry (2.2 u.m).
  Data obtained  from the  12-hr,  pilot-
scale, fluidized bed test showed that af-
ter 30  min of treatment, more than 90%
of the  metals and phosphates were  re-
moved. Aluminum generation rates were
highest when the throughput  flow  rate
was <4 gpm.  This  upper flow limit may
reflect compaction  of the fluidized bed
aluminum pellets  against the  upper
screen of the  electrocoagulation cell, thus
placing them  out of the  range of the
electrodes. As the  emulsion is destabi-
lized, the surrogate solution most likely
becomes less resistive to ion mobility
and, thereby, improves the operational
efficiency of the ACE Separator™.
  Filtration time  for solids coagulated
from  particulate  suspensions and oily
emulsions by electrocoagulation is much
less than for solids formed by chemical
coagulant addition. Slurries tested were
treated with  alum addition and with an
ACE Separator™. Electrocoagulation im-
proved the filtration rate of titanium  ox-
ide by 63%. Other  examples  (for an oily
emulsion and for biological sludge) indi-
cate highly enhanced filtration rates for
ACE Separator™ treated waste streams
when compared with those of either un-
treated or alum-treated waste streams.
   Shear strength of an electroco-
 agulation floe is generally much greater
than the shear strength of an alum floe.
 Both sonic treatments (used to evaluate
the  structural integrity of the floe) and
 actual filtration tests demonstrated higher
 shear strength of the electrocoagulation
 floes.
   Electrocoagulation of metal and phos-
 phate-bearing industrial solutions indi-
 cates  excellent nickel, copper, and phos-
 phate concentration reductions. More
 than 90% (concentration basis) of phos-
 phate and copper can be removed from
 such solutions at low aluminum and elec-
 trical  power requirements. Reduction  in
 the nickel concentration varies between
 75% and 85% (concentration basis).
   Electrocoagulation of synthetic labora-
 tory solutions and industrial  wastewater
 also confirmed the feasibility  of utilizing
 electrocoagulation for phosphate removal.
 Treatment of effluent from a commercial
 laundry reduced the phosphate concen-
tration from 45 mg/L to 5.4 mg/L after
low-intensity electrocoagulation (0.36 kW,
0.75-min retention time). Electrocoagulation
of process  water from a phosphate min-
ing operation reduced the phosphate level
by 91%, from 160 mg/L to 14 mg/L (3.3
kW,  0.17 min). Finally, treatment of di-
lute  phosphoric  acid solutions  with a
nominal 100 mg/L total  phosphate con-
centration and a conductivity of approxi-
mately 2000 u.S/cm resulted in  >95% re-
ductions in soluble phosphate  over a
range of acidities.

Capital and  Operating Costs
  As part  of this research  effort,  pro-
jected treatment cost estimates were de-
veloped.  Overall treatment operating
costs (electricity, aluminum  pellets, op-
eration, and maintenance) will vary  up-
wards from $0.50/1000 gal, depending
on emulsion strength, unwanted  compo-
nent concentration(s) (for example, emul-
sifiers)  in the effluent, and  its TSS.  (It
should  be  noted  that, at the outset, we
established that operating conditions ex-
ceeding $3.00/1000  gal would  not be
competitive with  conventional  treatment
processes,  and thus, they  were  elimi-
nated from future testing consideration.)
Estimates  are based on bench-  and pi-
lot-scale testing, additional considerations
may be involved  in full scale operation.
   Operator supervision and maintenance
would be  limited  to  periodic  replenish-
ment of the aluminum pellets, chemical
pretreatment systems (for example,  salt
addition for conductivity enhancement),
and  electrode replacement.  Estimated
operating costs are based on  laboratory
and  limited pilot-scale  testing of efflu-
ents, and  currently these costs exceed
those for comparable traditional chemi-
cal treatment (alum or polyelectrolytes).
The lower maintenance and operator su-
pervision required for ACE  Separator™
operation and the capability to use ACE
 Separator™ treated water in closed-loop,
zero-discharge applications adds to its
 attractiveness.  Successful commercializa-
tion  of the technology requires further
 research to significantly improve alumi-
 num dissolution  efficiency. If the  ACE
 Separator™ can  be engineered  to regu-
 larly generate  sufficiently high aluminum
 dissolution concentrations,  the  technol-
 ogy may be applicable to industrial efflu-
 ent treatment trains,  as well as for some
 Superfund site remediation activities.
   Incorporation of an automated process
 control system based on influent conduc-
 tivity and  solids  loading,  or on  the dis-
 charge solution's supernate turbidity, needs

-------
to be engineered. An automated  system
for addition of replacement aluminum pel-
lets may be justified, a'tthough the frequency
of pellet addition  should  be predictable
after an  initial period of operation. The
capital cost for a standard ACE Separa-
tor™ with nominal throughput capacity of
50 gpm is estimated at $80,000 and for a
250-gpm unit, $300,000.

Conclusions
   ACE offers a promising alternative for treat-
ing waste streams containing  clays, certain
metal constituents, and other soluble pollut-
ants. As an alternative to chemical condition-
ing, ACE Technology agglomerates the par-
ticles without adding any extraneous soluble
species (i.e., SO42'); the sludge  it produces
has a lower bound-water content that will filter
more rapidly and has a lower susceptibility to
filter shear of the coagulated particulates and
emulsion droplets.
   As a result  of the pilot-scale efforts, we
compared the effectiveness of  ACE
Separator™ treatment, alum  addition, and
polymer  coagulation. Conclusions drawn
from this comparison for various contami-
nant parameters were:
   • TSS: ACE Separator™ treatment and
    the  polymer  treatment  yielded
    equivalent results for the reduction of
    TSS in the treated supernates. TSS
    values for alum treatment were four to
    five times greater than those for ACE
    Separator™ treatment or polymer
    treatment.
   • COD:  ACE Separator™ treatment
    resulted in the highest COD reductions
    of  the three  methods.  Removal
    efficiency for  COD was from two to
    four  times  higher than removal
    efficiency for either alum treatment or
    polymer treatment.
  Lead: ACE  Separator™ treatment
  achieved approximately 6(3% removal
  of  lead  in  the  high metals  runs,
  whereas polymer treatment showed a
  slightly higher removal (71%). Because
  some difficulties were experienced with
  the alum treatment, these test results
  were  invalidated.  Further  ACE
  Separator™ treatments of slurries with
  low concentrations of metals yielded
  the highest lead removal (96%).
•  Copper: Copper in  the supernate
  achieved  dramatic removal  by
  electrocoagulation  in both  the  high
  (90% reduction) and  low (99%
  reduction)  metals  concentration
  experiments. In the former,  however,
  polymer and alum addition  achieved
  greater removal (approximately 100%
  reduction).
• Chromium: ACE Separator™ treat-ment
  resulted  in  good  removal  for  total
  chromium (87% and  94% reductions
  for the high and low  concentrations).
  Alum  and   polymer   addition
  accomplished similar  removal.
•  Cadmium: Cadmium levels in  the
  supernates dropped as a result of ACE
  Separator™ treatment: 14% in the high
  metals runs and 99% in the low metals
  tests. The  inconsistency  between
  these two sets of experiments, as well
  as the high concentrations remaining
  in the supernates and filtrates, raises
  questions about the  accuracy of
  experimental  results involving  high
  concentrations of metals. For the low
  metals tests, the cadmium concentrations
  in both ACE Separator™  filtrates were
  much lower than were the concentrations
  for either alum or polymer treatment.
  The following generalization on the ef-
fectiveness of the ACE treatment can be
made:
  • ACE  Separator™ treatment  con-
    sistently reduced the TS and TSS
    loadings to an equivalent degree and
    to  approximately one-quarter the
    level achieved through alum addition;
    and

  • Better reductions in  soluble metal
    concentrations are  achieved with
    electrocoagulation treatment  than
    with alum treatment.

  In summary,  ACE offers a promising
technically simple method for achieving
solids-liquid separations in aqueous-
based  waste streams. The majority of
the nontoxic, aluminum ionic species in-
troduced will be removed in the coagu-
lated solids phase. The ACE Technology
may be particularly suitable for zero-dis-
charge applications in which the addition
of chemicals and the buildup of residual
concentrations  (dissolved solids) would
adversely affect effluent quality or inhibit
effluent reuse.  Other potential  applica-
tions of the ACE Separator™ include: (1)
remediation  of groundwater   and
leachates (metals, COD/BOD removal),
(2) enhancement of clay separation from
aqueous suspensions/emulsions result-
ing from  soil-washing  operations, (3)
breakage of oil/water emulsions produced
in the pumping of hydrocarbon contami-
nated groundwater, and  (4) removal of
TSS from stormwater runoff. Possible in-
dustrial  applications are fine-grained
product recovery  (pigments, PVC) and
extraction of TSS from  waste  streams
that contribute  to high  BOD and  COD
loadings.
                                                                     l.S. GOVERNMENT PRINTING OFFICE: 1993 - 750-071/80064

-------

-------

-------
Naomi P. Barkleyfalso the EPA Project Officer, see below) is with the Risk
  Reduction Engineering Laboratory, Cincinnati, OH 45268; Clifton Farrell is
  with Electro-Pure Systems, Inc., Amherst, NY 14228; and Trade Williams, a
  U.S. Environmental Protection Agency research apprentice, is with the
  University of Cincinnati, Cincinnati, OH 45221.
Details of the completed SITE Emerging Technology project are given in a
    journal article published in Air and Waste, Vol. 43, No. 5, p. 784-789, May
    1993. The journal article entitled "Alternating Current Electrocoagulation for
    Superfund Site Remediation," (Order No. PB93-20S  144; Cost: $12.50,
    subject to change) is also available from:
        National Technical Information Service
        5285 Port Royal Road
        Springfield,  VA 22161
        Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
      Risk Reduction Engineering Laboratory
      U.S. Environmental Protection Agency
      Cincinnati, Ohio 45268
 United States
 Environmental Protection Agency
 Center for Environmental Research Information
 Cincinnati, OH 45268

 Official Business
 Penalty for Private Use
 $300

 EPA/540/S-93/504
     BULK RATE
POSTAGE & FEES PAID
         EPA
   PERMIT No. G-35


-------