Combining Electrocoagulation and Electrochemical Oxidation for Petrochemical Wastewater Treatment Petrochemical wastewater is difficult because the contaminant profile is rarely stable. A refinery or petrochemical complex may discharge oily wastewater from tank farms, process drains, desalter effluent, spent caustic handling, cooling blowdown, polymer units, phenolic streams, and cleaning operations. The combined wastewater can contain free oil, emulsified oil, suspended solids, sulfides, phenols, BTEX, PAHs, surfactants, dissolved metals, high COD, color, odor, and variable salinity. A conventional treatment train can handle part of this load. API separators, CPI units, DAF, biological treatment, sand filters, and activated carbon all have their place. The problem usually appears when the effluent still carries refractory COD, residual phenols, stable emulsions, dissolved metals, or toxicity that does not respond well to biological treatment alone. A combined electrocoagulation–electrochemical oxidation system, often written as EC–EO,
