United States
Environmental Protection
Agency
EPA/540/F-92/011
October 1992
vvEPA
SUPERFUND INNOVATIVE
TECHNOLOGY EVALUATION
Emerging Technology Bulletin
Alternating Current Electrocoagulation
Electro-Pure Systems, Inc.
Technology Description: Alternating current electrocoagulation
(ACE) technology offers an alternative to primary chemical co-
agulant or organic polymer addition for breaking stable emulsions
and suspensions. The ACE technology is also effective for re-
moving certain metals and other soluble pollutants in the polish-
ing step of effluent treatment. Traditional chemical coagulant
addition generates voluminous, gelatinous sludges which are
difficult to dewater and filter slowly. Another disadvantage of
chemical coagulation is the high susceptibility to particulate filter
shear of the coagulated particulates and emulsion droplets.
ACE is- an electrochemical technology for introducing low concentra-
tions of a non-toxic polymeric aluminum hydroxide species into aque-
ous media. These species neutralize the electrostatic charges on
suspended solids and oil droplets thereby inducing accumulation and
separation from the aqueous phase. For remediation or effluent treat-
ment lower purity aluminum pellets, produced from recycled scrap or
beverage cans, can be used. In industrial situations where product
purity is a concern, high purity aluminum pellets are required. ACE
appreciably enhances the filtration and dewatering rates of solids
removed from an effluent. Liquid/liquid and solid/liquid phase separa-
tions are achieved with production of sludges that can be filtered more
readily than those formed through chemical flocculant addition. The
coagulation is induced without adding any soluble species. The sludge
produced has a lower contained water content and is more easily
dewatered. Separation of the hazardous components from an aque-
ous waste with ACE reduces the volume of potentially toxic pollutants
requiring special handling and minimizes waste disposal. Significant
reductions in total suspended solids of particulate slurries, metal con-
centrations, fluorides, and phosphates can also be achieved. See
Figure 1 for the ACE basic process flow.
The technology can be used to break stable aqueous suspensions
containing subimicron-sized particles of up to 10% total solids and
stable aqueous emulsions up to 5% oil. Fine-grained products can be
recovered using ACE. ACE has been shown to improve the
buffering capacity and settling characteristics of sludges.
Vent or
Treat Gas
Aqueous
Suspension
or Emulsion
Control
Feed Rate
A.C.
Coagulator
Product
Separation
Air for
Turbulence
Figure 1. Alternating current electrocoagulation basic process flow.
Printed on Recycled Paper
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Waste Applicability
The ACE technology can be applied to various aqueous-based sus-
pensions and emufetons typically generated by contaminated ground-
watof, surface runoff, landfill teachate, truck wash, scrubber solutions,
tested effluents and extract solutions. Suspensions Include solids such
as pigments, days, metallic powdeis, metal ores, and natural colloidal
matter, Emulsions Include a variety of solid and liquid contaminants
such as peJrateum-based by-products.
Reductkxis exceeding 90% in the loadings of aqueous day, latex, and
titanium dioxide suspensions have been routinely achieved. Reductions
exceeding 80% En the Chemfcat Oxygen Demand (COD) and Total
Organic Catbon (TOG) content of diesel fuel-spiked slurries have been
aecomplihed
ACS has ateo been used for recovery of reusable fine-grained product
from Industrial process streams that would have been discharged into
the sewer system, and for the extraction of suspended solids from
Waste streams which contribute to high biological oxygen demand
(BOD) and COD loadings. Use of ACE for municipal wastewater
treatment would reduce the quantity of chlorine required to achieve
required disinfection levels.
Test Results
The ACE Technology was tested using two designs of the ACE
Separator, (1) a Parallel Electrode unit in which a series of parallel,
vertically-oriented aluminum electrodes form a series of monopolar
efedrofylic ceils through which the effluent passes, and (2) a Ruidized
Bed unit with noa-conductive cylinders equipped with non-consumable
metal electrodes between which a turbulent fluidized bed of aluminum
altoy peBets Is maintained. The FUdized Bed Unit dissolved aluminum
at least one order of magnitude more efficiently than the Parallel Unit.
Results reported here are from experiments with the Fluidized Bed
ACE Separator.
The Emeiging Tecrmofogy/SlTE program research involved testing
varfous surrogate wastes prepared from EPAs Synthetic Soil Matrix
(SSMJ as stabte aqueous suspensions of si, clay, and topsoil contain-
tng efiaseS fuel, metaJs, and a strong surfactant were tested at bench-
Bench-scafe experiments were conducted on surrogate wastes pre-
pared by mixing 0.2 to 3,0 wt % of the -230 mesh (day and silt) fraction
ofthaSSMwihO.Sto 1,5wt%of Number 2 diesel fuel, 0.5 to 0.10 wt
% of an emufsifler (nton-IQOX or Alconox soap), and from 10 mg/Lto
100 ttgIL of one or more of the following contaminants: copper, nickel,
zinc* Grthophosphafe, or fluoride, The pH of each mixture was adjusted
to 5,7, or 9 and the conductivity raised to approximately 1200 uS/cm to
1500 u&em vrtlh NaC! to simulate natural values. Bench-scale results
indicated: (1) heating of the waste sluiry during electrocoagulation
enhanced phase separation; (2) electrocoagulation produced approxi-
mately 83% Jess sludge volume and a 76% improvement in filtration
rate when compared to alum (Al,2(SO4)3) treatment; (3) aluminum and
stainless steel used as electrode material gave comparable results;
and (4) agglomerated particles tend to disaggregate with both in-
creased AC current frequency and increased retention time.
Pilot-scale experiments of comparative electrocoagulation and alum
treatments of a 3% soil slurry containing approximately 50% clays,
1.5% diesel fuel, 0.1% of a strong surfactant and metals (Cu, Cd, Cr,
Pb) were conducted. Electrocoagulation produced reductions of total
suspended solids (TSS) (222 to 4.5 sng/L), and total organic carbon
(TOG) (130-6,6 mg/L). Copper was reduced by 72%, cadmium by
70%, chromium by 92%, and lead by 88%, No appreciable change in
total solids (TS) loadings in the supemate resulted from
electrocoagulation.
Comparative alum additive experiments were also conducted using
the same surrogate waste. Alum treatments generally required ap-
proximately 30% longer filtration times. ACE Separator treatment
reduced the TS and TSS to an equivalent degree and approximately
one-quarter the level achieved through alum addition. Better reduc-
tions in soluble metal concentrations are achieved with
electrocoagulation treatment.
Particle size analyses show considerable enhancement in the clay
fraction as a resuft of electrocoagulation. The mean sizes of the ACE
Separator-treated particulates both in the supernate and the filtrate
(188 and 230um respectively;! have increased by a factor of about 85
forthe supernate and approximately 105 for the filtrate, over that in the
original slurry (2.2um).
For Further Information:
EPA Project Manager
Naomi Barkley
U,S. EPA Risk Reduction Engineering Laboratory
26 West Martin Luther King Drive
Cincinnati, OH 45268
(513) 569-7854
Technology Developer Contact:
Clifton Farreli
Electro Pure Systems, Inc.
10 Hazelwood Drive
Amherst, NY 14228
(718)691-2610
United States
Environmental Protection Agency
Center for Environmental Research Information
Cincinnati, OH 45268
Official Business
Penalty for Private Use
$300
BULKRATE
POSTAGE & FEES PAID
EPA
PERMIT No. G-35
EPA/S40fF-92/011
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