Electric Coagulation

Wastewater treatment by electrical coagulation

Electrocoagulation is treated by direct current (DC) and metallic plates of aluminum and iron as chemical electrodes, which is referred to as the EC method in the process of electrochemical decomposition. Electrocoagulation or EC used in order to remove heavy metals, TSS and turbidity factors, COD and BOD, petrochemicals, colors, fluorine, arsenic and soil and water pollution in the treatment of wastewater and wastewater industries such as textile, slaughter, dyeing, dairy, Carwash, starch, carpet and petrochemicals.

In electrocoagulation or electrical coagulation, electrodes, which include iron and aluminum, form metal hydroxide molecules such as Al (OH) 3 or Fe (OH) 2, which due to their high absorption properties, can form a complex. It is finally settled in the EC drainage tank and the sewage treatment process is completed. Design, construction and installation of various types of sewage treatment systems are carried out by the method of electrocoagulation, electrical coagulation (EC) according to the sewage analysis and the nature of wastewater in the TARHOKAR Engineering company.

Description of the process of wastewater treatment by electrocoagulation (EC)

In the treatment of wastewater and industrial wastewater, there are various types of paint, detergent, high turbidity factors and TSS as well as heavy metals, which cause problems in the process of treatment of wastewater by biological methods (aerobic and anaerobic units). Therefore, engineers and designers of the sewage system purification units try to eliminate the concentration of toxic pollutants that may interfere with the biological treatment processes (biological) before entering of the wastewater into aerobic and anaerobic units.

For this purpose, one of the methods used in industrial wastewater treatment is the coagulation and flaking of particles and contaminants. Suspended particles and pollutants that consist mainly of colloidal substances, because of the electric charge, repel each other and only then we can separate and refine them from the sewage, when their charge is neutral and they will cling to each other, therefore becoming heavy and will be precipitated so it will be separated from the wastewater.

In the treatment of sewage, metals such as aluminum and iron are used in electrical coagulation. These metals, hydrolyzed during contact with water, generate positive-charge ions, thus neutralizing the negative charge colloidal particles, and form the core of leachate flocculation in the process of sewage treatment. This flocculation is formed in the form of a complex of metal and metal hydroxide, and since metal hydroxide has high absorption properties, the EC coagulation package is one of the most successful methods of physical and chemical treatment of sewage.
In a coagulation package, electrocoagulation (EC) is used to create a chemical electrolyte in the sewage using direct current(DC). The direct current during electrical coagulation treatment processes leads to the formation of iron or aluminum hydroxide, which absorbs the precipitated particles in the wastewater due to the absorption properties and forms a precipitated complex.

Chemical reactions in the process of wastewater treatment by electrocoagulation (EC):

In the treatment of sewage by coagulation, several chemical reactions occur simultaneously on the cathode and anode plates. These reactions are the result of the transfer of electrons from the EC plates during the sewage treatment process.
Some of the major reactions that occur during the sewage treatment process include

As you can see, two separate reactions occur in the purification of wastewater by the method of electrocoagulation. On one hand, a heavy metal complex formed on the basis of aluminum hydroxide forms the primarily core of the floc and forms sediment that will be precipitated during the process of waste-water treatment by means of electrocoagulation. On the other hand, gas quantities are released during the wastewater treatment process by electrocoagulation, which causes the lighter particles to float on the surface of the coagulation package.

Effective factors in the treatment of sewage by electrocoagulation (EC):

The most important factors in the design and construction of a wastewater treatment package are electrical components such as TSS, COD, oil, grease, heavy metals, detergents, temperature and pH. Accordingly, the amount of current and voltage required, the number and type of electrodes, and the volume of the primary reactor and the sedimentation tank required for the treatment of waste water by electrocoagulation (EC) are calculated. The construction and assembly of the electrocoagulation package (EC) after the preparation and setup of the production plans and according to the common standards at the workshop of the TARHOKAR Engineering Company (Department of Wastewater Treatment) will be done.

Application of electrocoagulation package

The use of electrocoagulation due to its high ability to remove the following contaminants in sewage treatment is effective:

•    The factors related to TSS and opacity
•    Oil & Grease
•    Foam and detergent
•    Heavy metals
•    Color
•    Fluorine, arsenic
•    Pollution of water and soil

Accordingly, the Electric Coagulation Package (EC) can be used to treat wastewater from many industries, some of which include:

• In the treatment of sewage, in order to remove polymers and long carbon chains.

• In the treatment of dairy industry wastewater to remove soluble fats and reduce TSS

• In the treatment of stool and glucose sewage to reduce fat and eliminate insoluble carbohydrates

• In carwash wastewater treatment to eliminate foam and detergent and reduce TSS of wastewater and ATPEs.

• In sewage treatment of slaughterhouse centers in order to eliminate and reduce TSS, fats in sewage

• In wastewater treatment of the metal plating industry to remove heavy metals such as chromium

Electrocoagulation (EC) in sewage treatment

In a coagulation package (Electrocoagulation or EC), heavy metals will be removed at 99% efficiency. Removed detergent, suspended solids and grease, and eventually eliminated COD with a high efficiency of 50%. Also, the TSS will be eliminated 50% to 80% depending on its nature. All of these factors have led to the use of electrical coagulation in the treatment of wastewater and industrial effluents.

Advantages of using a coagulation package

The use of an electric coagulation package in sewage treatment industry is economically more beneficial compared to chemical coagulation, due to the use of direct current instead of chemical injection. Electrocoagulation(EC) is used only for the plates (electrodes) of iron or aluminum, and they need to be replaced after several years. While in the daily chemistry method, high amounts of additives to adjust the pH, coagulants and polymer coagulants should be injected into the wastewater, which greatly increases the cost of operating the sewage treatment system.
Generally, the benefits of electric coagulation of sewage treatment include:
•    Less desired coagulation ions
•    Improved removal efficiency
•    No need for chemicals
•    Less productive sludge
•    Low reaction time
•    The need for a lower volume wastewater treatment reactor
•    Cost Effective

Sewage Treatment Executive Project, ElectroCoagulation Package

One of the projects of the engineering and design company, designed and operated by the company’s wastewater treatment engineering group, was the treatment of textile wastewater, one of the processes of which is the electrical coagulation method (EC). The general characteristics of this sewage treatment project are as follows