Electrocoagulation is one of the processes used to treat industrially used water and also drinking water from metal and other soluble contaminants.

1. ELECTROCOAGULATION
Advanced Technique in Water Treatment
Abdelrahman Kamal
eng.abdo.kamaal@gmail.com
Suez University
Faculty of Petroleum and Mining Engineering
Refinery and Petrochemical Engineering Dept.
Prepared Abdelrahman Kamal Mahmoud
Supervisor Dr. Abeer Shoaib
(lecturer of water treatment course)
Introduction to

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Content of Text
Introduction
Electrocoagulation advantage
Mechanism of process
Operating Parameters
Classification of electrocoagulation reactor system
System Calculations
Electrocoagulation disadvantage
Reference

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EC is a complicated process involving many chemicals and physical phenomena that
use consumable electrodes to supply ions into the wastewater stream.
The main classification of Treatment process based on their unit operation are:
▪ Mechanical Processes: separation of material based on physical/mechanical properties like
density, size, wettability, etc.
▪ Chemical Processes: operations include adding chemicals to change or affect properties of
substance like flocculation, PH modification, adsorption, etc.
▪ Biological Processes: operations including adding of micro-organisms to medium to alternate
medium state or property such as sulfide-reducing bacteria.
▪
▪ Electromechanical Processes: applying direct or alternative electrical current to affect medium
Electrocoagulation is classified as an electromechanical process as its name shows.
Q- What does electrocoagulation mean?
- It's an advanced and economical water treatment technology, Electrocoagulation
("electro", meaning to apply an electrical charge to water, and "coagulation", meaning the
process of changing the particle surface charge, allowing suspended matter to form an
agglomeration)
- It effectively removes suspended solids to sub-micrometer levels, breaks emulsions such
as oil and grease or latex, and oxidizes and eradicates heavy metals from water without
the use of filters or the addition of separation chemicals.
Electrocoagulation advantage:
This process can deal with some problems more easily, efficiently and more cheaply than
mechanical and chemical processes in some cases as will be shown:
Mechanical Filtration: work efficiently with suspended solids larger than 30 µm, and free
oil and grease, but can't deal with particles smaller than 30 µm and emulsified oil and
grease cause damage to the media filters, resulting in very high maintenance costs.
Chemical treatment works with suspended solids, oil and grease, and some heavy metals—
but may require up to three polymer and multiple pH adjustments for proper treatment.
This technology requires the addition of chemicals resulting in expensive, messy, and labor-
intensive treatment.
But Electrocoagulation deals with any size of suspended solids (including destructive >30 µm
particles and heavy metals that can wear-and-tear pressure washers and pose an
environmental and employee hazard) and also requires no filters, no daily maintenance, no
additives, and removes any size of suspended solids, oil, grease and heavy metals.

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So, we can say electrocoagulation has the following characteristics:
✓ It requires simple equipment and is easy to operate with sufficient operational options to
handle most problems encountered on running.
✓ The electrolytic processes in the EC cell are controlled electrically and with no moving
parts, which requires less maintenance.
✓ The EC process efficiently removes the smallest colloidal particles, because the applied
electric field neutralizes any residual charge, facilitating the coagulation.
✓ It generally avoids excessive use of chemicals that reduces requirement to neutralize
excess chemicals and possibility of secondary pollution caused by chemicals.
✓ Wastewater treated by EC gives palatable, clear, colorless and odorless water.
✓ Flocs formed by EC are similar to chemical floc, but EC floc tends to be much larger,
contains less bound water, is acid-resistant and more stable so it can be separated faster
by filtration
✓ Sludge formed by EC tends to be readily settable and easy to de-water.
✓ Gas bubbles produced during electrolysis can carry the pollutant components to the top of
the solution where it can be more easily concentrated, collected and removed by a
motorized skimmer.
✓ Destroys and removes bacteria and viruses.
✓ pH control is not necessary, except for extreme values.
Mechanism of Electrocoagulation:
Electrocoagulation Processes:
- Seeding: resulting from the cathode reduction of metal ions that become new centers for
larger, stable, insoluble complexes that precipitate as complex metal ions.
- Emulsion Breaking: resulting from the oxygen and hydrogen ions that bond into the water
receptor sites of emulsified oil molecules creating a water-insoluble complex separating
water from oil, driller's mud, inks or fatty acids, etc.
- Halogen Complexing: as the metal ions bind themselves to chlorines in a chlorinated
hydrocarbon molecule resulting in a large insoluble complex separating water from
pollutant like pesticides, herbicides, chlorinated PCBs, etc.
- Bleaching: by the oxygen ions produced in the reaction chamber oxidizes dyes, cyanides,
bacteria, viruses, biohazards, etc. The current controlled ion transport between the
electrodes creates an osmotic pressure that typically ruptures bacteria, cysts, and viruses.
- Oxidation Reduction Reactions: concentration gradients and Solubility Products (KsP) are
the chief determinants to enable reactions to reach stoichiometric completion.
- Induced pH: swings toward neutral.

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In an EC process the coagulating ions are produced ‘in situ’ and it involves three
successive stages:
• formation of coagulants by electrolytic oxidation of the ‘sacrificial electrode'
• destabilization of the contaminants, particulate suspension, and breaking of
emulsions
• aggregation of the destabilized phases to form flocs
Procedures of Electrocoagulation Process:
Coagulation process will be initiated by neutralizing the charges of the particles by
released ions.
Fe/Al is dissolved from the anode generating corresponding metal ions, which almost
immediately hydrolyze to polymeric iron or aluminium hydroxide. These polymeric
hydroxides are excellent coagulating agents.
Coagulation occurs when these metal cations combine with the negative particles
carried toward the anode by electrophoretic motion.
The released ions remove undesirable contaminants either by chemical reaction and
precipitation, or by causing the colloidal materials to coalesce, which can then be
removed by flotation.
Water containing colloidal particulates, oils, or other contaminants move through the
applied electric field, there may be ionization, electrolysis, hydrolysis, and free-radical
formation which can alter the physical and chemical properties of water and
contaminants.
Water is also electrolyzed in a parallel reaction, producing small bubbles of oxygen at
the anode and hydrogen at the cathode.
These bubbles attract the flocculated particles and, through natural buoyancy, float the
flocculated pollutants to the surface
The reactive and excited state causes contaminants to be released from the water and
destroyed or made less soluble.

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Reactions
at anode:
When the oxygen evolution potential is:
at cathode:
(acid medium)
(neutral or alkaline medium)
Operating Parameters Affecting Process
- Solution pH
- Type of Power Supply
- Current density
- Conduct of solutions
- Electrode arrangement
- Type of electrode material
- Electrode gap
- Electrode shape
- Initial pollutant concentration
- Type of salt
- Mixing speed
- Operating time

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Structure of electrocoagulation system:
 Feed Storage Tank
 Pump
 Control Valve
 DC Power Supply
 Electrocoagulation Reactor
 Treated Product Tank
Types of Electrocoagulation cells

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Classification of electrocoagulation reactor system:
Batch Continuous
Coagulation Only Coagulation and
Floatation
Coagulation Only Coagulation and
Floatation
Centrifuge In Situ Settler Settler
Settler Settler Hydrocy clone Filtration
Clarifier Floatation
Filtration Centrifuge
Electro-floatation In situ
DAF (Dissolved air
floatation)

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Reactor Calculations
a) Current efficiency
The theoretical amount of metal dissolved depends on the quantity of
electricity passed through the electrolytic solution and can be derived from
Faraday’s law:
𝒘 =
𝒋 × 𝒕 × 𝑴
𝒏 × 𝑭
Parameters:
W: mass of electrode material dissolved (gcm2
)
J : current density ( Amperecm2
)
M: relative molar mass of electrode
n: number of electrons in oxidation reaction
F: Faraday constant
b) Power consumption
It is important to specify the energy consumed during the treatment, it is
usually calculated by the power consumption.
𝑾 =
𝒗 × 𝒊 × 𝒕
𝟏𝟎𝟎𝟎 × 𝑽
Parameters:
W: power consumption (kWhm3
)
v : voltage supplied (Volt)
i : electric current (Ampere)
t : residence time (hour)
V : Sample Volume (m3
)

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Electrocoagulation disadvantage:
 The use of electricity may be expensive in many places.
 High conductivity of the wastewater suspension is required.
 High concentrations of iron and aluminum ions in the effluent that have to be
removed.
 Gelatinous hydroxide may tend to solubilize in some cases.
 The hydroxide suspension does not have an appropriate hydraulic grain size,
which makes it difficult to separate
 High conductivity of the wastewater suspension is required.
References:
A. Fundamentals of electrocoagulation, author: Nilson Marriaga-Cabrales and
Fiderman Machuca-Martínez- GAOX Group, Chemical Engineering School,
Universidad del Valle
B. A THESIS of DOCTOR OF PHILOSOPHY degree - title: REACTOR DESIGN
PARAMETERS, IN-SITU SPECIATION IDENTIFICATION, AND POTENTIAL
BALANCE MODELING FOR NATURAL ORGANIC MATTER REMOVAL BY
ELECTROCOAGULATION – author: Kristian Lukas Dubrawski - The Faculty of
Graduate Studies (Chemical and Biological Engineering)
C. Application of Electrocoagulation Process for Continuous Coal Stockpile
Wastewater Treatment System- author: Rusdianasari - Department of
Chemical Engineering, Indonesia
D. https://www.intechopen.com/books/modern-electrochemical-methods-in-
nano-surface-and-corrosion-science/preventing-of-cathode-passivation-
deposition-in-electrochemical-treatment-methods-a-case-study-on-wi