Electro-Coagulation: Electricity + Water = Magic
by Rami Elias Kremesti M.Sc., CSci, CENv, CWEM
© 2025 Kremesti Environmental Consulting Ltd
Introduction:
When i was in High School we learned about the electrolysis of water. Just attach two electrodes to a DC power supply and insert in water. H2 is produced at the negative Cathode where H+ ions are reduced to Hydrogen verified with the pop test when a flame is applied to the gas. O2 gas is produced at the positive Anode where OH- ions are oxidized. Thus water is split to form H2 and O2. Something else interesting happens: if the electrode is iron, Ferrous ions are also released into the solution which turns a beautiful blue due to the formation of Fe(OH)2.
We were crazy enough to the try this experiment with an exposed Copper wire and AC current too !! The reaction is very violent and the water turns into a turquoise blue due to the formation of Cu(OH)2.
CAUTION: Do not perform this experiment at home without a proper Risk Assessment and adult supervision.
DC current and electrodes are also used in the Chlor-Alkali process: a concentrated brine NaCl solution is electrolysed and Na metal is produced this time on the Cathode and Cl2 gas at the anode. The Na metal reactions with water to form NaOH and H2 gas. All three are useful industrial substances.
Figure 1: Chlor Alkali Process
Applications:
A nice schematic of the electro-coagulation process is depicted below:
Figure 2: Electro Coagulation Schematic
The ferrous and aluminum ions produced at the Anode are coagulants and they help to remove suspended solids from water as well as break emulsions. The hydrogen produced in the form of fine bubbles lifts some of the suspended solids in the water to the surface of the water in a process similar to DAF = Dissolved Air Floation.
Treatment of wastewater and wash water by EC has been practiced for most of the 20th century with increasing popularity. In the last decade, this technology has been increasingly used in the United States, South America and Europe for treatment of industrial wastewater containing metals. It has also been noted that in North America EC has been used primarily to treat wastewater from pulp and paper industries, mining and metal-processing industries. A large one-thousand gallon per minute cooling tower application in El Paso, Texas illustrates electrocoagulation’s growing recognition and acceptance to the industrial community. In addition, EC has been applied to treat water containing foodstuff waste, oil wastes, dyes, output from public transit and marinas, wash water, ink, suspended particles, chemical and mechanical polishing waste, organic matter from landfill leachates, defluorination of water, synthetic detergent effluents, and solutions containing heavy metals. Electrocoagulation is not typically used for domestic wastewater treatment.
Advantages
The advantages of electro coagulation are that it is a form of production of a coagulant without using chemicals. It also has another very important advantage: chemical coagulants such as FeCl3 and Al2(SO4)3 add chloride or sulphate ions to the water which increase the TDS and at the same time they make the water more corrosive to steel. This advantage also results in electro-coagulation producing less sludge that traditional coagulation.
Ofcourse the pH also increases since H+ is reduced and this helps to precipitate heavy metals in the water for example in the case of treating Mine Waste water.
Another interesting aspect of electro-coagulation with Iron electrodes is that the ferrous ions produced can be used to catalyse the famous Fenton’s Reacgent where H2O2 hydrogen peroxide is added to the water. This can help oxidise COD in the water.
Other Types of Electrolysis
Using electrodes such as Boron Doped Diamond results in more fascinating chemistry: Since the electrode is inert and does not dissolve, Hydorxyl radicals can form which are excellent at oxidizing organic pollutants.
Companies that Specialize in Electro-Coagulation and Electro-Chemistry
One such company that specializes in this kind of reactor is Arvia in the UK. They focus on pharmaceuticals and pesticides.
Another one is Power and Water. The big water treatment companies such as Veolia and Nijhuis also have electro-coagulation systems.
About the Author:
Rami Elias Kremesti is a chartered water treatment expert residing in the UK. He earned his M.Sc. in Industial Chemistry from the USA. Rami worked 10 years on power stations worldswide as a chemistry and water specialist and he has experience in industrial waste water treatment, sewage treatment, Reverse Osmosis, Cooling Tower chemistry, potable water treatment and is passionate about mitigating climate change using chemistry. He enjoys spending time with this daughters, cooking, playing guitar and spending time in nature.
Rami Elias Kremesti Portrait