Elektrokoagulaatio

Elektrokoagulaatio, or electrocoagulation, is an electrochemical water and wastewater treatment process in which sacrificial metal electrodes dissolve to form coagulant hydroxide species in situ. When a direct current is passed between paired electrodes, the anode dissolves (for example as aluminum or iron), releasing metal ions that hydrolyze in water to form Al(OH)3, Fe(OH)3 and related species. These hydroxides destabilize suspended particles and dissolved organics, promoting aggregation into flocs that can be separated by settling, flotation, or filtration.

The mechanism combines charge neutralization, adsorption of contaminants, and co-precipitation with metal hydroxides. As flocs form, turbidity, color, natural organic matter, emulsified oils, and some dissolved metals are removed from the treated stream. Gas evolution at the cathode can aid flotation of the formed flocs. The process is typically operated with aluminum or iron electrodes and a direct current power supply; pH and conductivity influence floc formation, with local pH changes near the electrodes common due to hydrolysis and cathodic alkalinity.

Advantages include reduced need for conventional chemical coagulants, rapid treatment, and effectiveness across a range of waters, including muddy, colored, or saline feeds. It can also improve compatibility with subsequent membrane processes. Limitations involve electrode wear and passivation, energy consumption, production of metal-containing sludge, and the need to manage residual metals and pH locally. Optimal performance depends on electrode material, current density, inter-electrode spacing, flow rate, and water chemistry.

Applications span drinking water pretreatment, industrial wastewater treatment, sludge conditioning, and pretreatment for membrane filtration, making elektrokoagulaatio a versatile option for coagulation-based purification.