Electrocoagulation (EC) Wastewater Treatment

Electrocoagulation (EC) applies a DC current through sacrificial electrodes — commonly aluminium or iron — immersed in wastewater. The electrodes dissolve electrolytically, releasing Al³⁺ or Fe²⁺/Fe³⁺ ions directly into the water, which hydrolyse into coagulant species with chemistry similar to dosing alum or ferric chloride, except the coagulant is generated electrically rather than added as a liquid chemical. Simultaneously, hydrogen gas micro-bubbles form at the cathode, helping to float the resulting coagulated flocs to the surface — a flotation effect comparable to dissolved air flotation (DAF).

EC is particularly effective for contaminants that are difficult to treat with biological processes alone: heavy metals removal, emulsified oils, dye and colour removal, fluoride removal, arsenic removal, and general COD/TSS reduction through destabilisation of fine colloidal particles. Because the coagulant is generated in situ, plants avoid the need to store and handle liquid coagulant drums, and process control becomes simpler — operators adjust current and voltage rather than managing chemical dosing pumps and dose rates.

Energy consumption typically runs 0.5–2 kWh/m³ depending on the conductivity of the wastewater and the contaminant load being treated. EC performs best on higher-conductivity streams; low-conductivity wastewater requires a supporting electrolyte, typically sodium chloride (NaCl), to reduce electrical resistance and keep energy consumption practical. Electrode passivation and scaling are known operating issues over time, generally managed through periodic polarity reversal or scheduled mechanical cleaning of the electrode plates.

Electrodes are consumed during operation as sacrificial anodes, representing a recurring replacement cost that should be factored into lifecycle operating budgets alongside power consumption. Electrocoagulation is commonly deployed as a pretreatment stage ahead of biological treatment for textile, electroplating, and tannery effluents carrying high heavy-metal or dye loads, since these contaminants can otherwise inhibit or pass through biological treatment processes untreated. Compared to chemical coagulant dosing, EC often produces lower sludge volumes and is effective across a wider pH range, making it a robust pretreatment option for variable industrial effluent streams.