Coagulation is one of the most important physiochemical operations used in water treatment. This is a process used to cause the destabilization and aggregation of smaller particles into larger particles. Water contaminants such as ions (heavy metals) and colloids (organics and inorganics) are primarily held in solution by electrical charges. Schulze, in 1882, showed that colloidal systems could be destabilized by the addition of ions having a charge opposite to that of the colloid (Benefield et al., 1982). The destabilized colloids can be aggregated and subsequently removed by sedimentation and/or filtration.
Coagulation can be achieved by chemical or electrical means. Chemical coagulation is becoming less acceptable today because of the higher costs associated with chemical treatments (i.e., the large volumes of sludge generated, and the hazardous waste categorization of metal hydroxides, to say nothing of the costs of the chemicals required to effect coagulation).
Electrocoagulation (EC), the passing of electrical current through water, has proven very effective in the removal of various contaminants from water. Electrocoagulation systems have been in existence for many years (Dieterich, patented 1906), using a variety of anode and cathode geometries, including plates, balls, fluidized bed spheres, wire mesh, rods, and tubes. G.R. Enterprises Services offers a quantum leap in refining the EC process to increase removal rates and to lower capital and operating costs.
The electrocoagulation process is based on valid scientific principles involving responses of water contaminants to strong electric fields and electrically induced oxidation and reduction reactions. This process is able to take out over 99 percent of some heavy metal cations and is also able to totally eliminate microorganisms in the water. It is also able to precipitate charged colloids and remove significant amounts of other ions, colloids, and emulsions.
How it works
The electrocoagulation process destabilizes suspended, emulsified or dissolved contaminants in an aqueous medium by introducing an electrical current into the medium. The electrical current provides the electromotive force to drive the chemical reactions. When reactions are driven or forced, the elements or compounds will approach the most stable state. Generally, this state of stability produces a solid that is either less colloidal or less emulsified (or soluble) than the compound at equilibrium values. As this occurs, the contaminants form hydrophobic entities precipitate and can easily be removed by a number of secondary separation techniques. Stated another way:
Electrocoagulation utilizes direct current (DC) to cause sacrificial electrode ions to remove undesirable contaminants either by chemical reaction and precipitation, or by causing colloidal materials to coalesce and then be removed by electrolytic flotation. The electrochemical system has proven to be viable with a wide variety of wastewaters. These waters are paper pulp mill waste, metal plating, tanneries, canning factories, steel mill effluent, slaughterhouses, chromate, lead and mercury-laden effluents, as well as domestic sewage. These wastewaters will be reduced to clear, clean, odorless and reusable water. In most cases, especially domestic sewage, the treated water effluent will be better than the raw water from which it originated.
- Removes heavy metals as oxides that pass TCLP (Toxic Classification Leaching Procedure)
- Removes suspended and colloidal solids
- Breaks oil emulsions in water
- Removes fats, oil, and grease
- Removes complex organics
- Destroys & removes bacteria, viruses & cysts
- Processes multiple contaminants
- Ground water cleanup
- Process rinse and wash water
- Potable water
- Sewage treatment
- Cooling towers
- Radioactive isotope removal
- Pretreatment for reverse osmosis, ultra filtration, nanofiltration, photocatalytics
- Water reuse resulting in zero discharge
- Metal recovery
- Industrial waste water
- Low capital costs
- Low operating costs
- Low power requirements
- Generally no chemical additions
- Metal oxide formation passing TCLP
- Low maintenance
- Minimal operator attention
- Handles wide variations in the waste stream
- Consistent and reliable results
- Sludge minimization
- Treats multiple contaminants