JPS6339320B

PURPOSE:To improve COD removal effect by adding H2O2 and a material which dissociates metal ions in an aqueous soln. to sewage, allowing reaction to take place, neutralizing the sewage, and adding H2O2 and the above-mentioned metal ions to the supernatant having been subjected to solid-liquid separation. CONSTITUTION:Raw water 1 is added with iron ion contg. liquid 3 such as aqueous FeCl3 soln. and hydrogen peroxide 4 in the 1st stirring tank 2, and is stirred under conditions of about 2-4 pH, after which it is added with an alkali agent 6 such as Mg(OH)2 and is neutralized in the 2nd stirring tank 5. The formed precipitate is separated in the 1st sedimentation basin 7-2. Thence, the overflow water 9 from the basin 7-2 flows into the 3rd stirring tank 3, where it is added with iron ion contg. liquid 10 such as an aqueous ferrous sulfate and H2O2 11, to about 2-4 pH, and the water is stirred. Further, in the 4th stirring tank 14, it is added with an alkali system 13 of magnesium type such as Mg(OH)2, whereby it is neutralized to about 5-8 pH.