Waste liquor treatment to reduce chemical oxygen demand

摘要

Removal of the chemical oxygen demand (COD) of waste liquor by electrolysis and oxidation comprises (a) passing the waste liquor into a vessel where it is adjusted to pH 2-6; (b) passing the discharge from this vessel to an electrolysis/oxidation vessel with a steel or iron anode and an iron, stainless steel, nickel, zinc or lead cathode and adding a suitable amount of hydrogen peroxide; (c) carrying out electrolysis and oxidation for a first residence time; (d) adjusting the discharge from this vessel to pH 6-9 to precipitate iron hydroxide; and (e) separating the precipitate. Also claimed is the apparatus used, comprising the vessels used in these stages and a unit for separating the precipitate.