1313550 Sewage treatment TATABANYAI SZENBANYAK 3 Dec 1970 [15 Dec 1969] 57430/70 Heading C1C The biochemical oxygen demand of sewage containing protein is reduced by the addition thereto of at least 120 g./m.3 of a water-soluble aluminium or iron salt and if required 0??5 to 1 kg./m.3 of bentonite or kaolin in an aqueous solution of 5 to 10 g./m.3 of homopolymers and copolymers of acrylic acid and acrylic amide, the pH of the so-treated sewage being then adjusted to exceed 10 by the addition of a basic calcium compound thereto, the protein-containing precipitate so obtained being separated from the basified aqueous liquor and its pH adjusted by means of carbon dioxide to a value of 7 or below. The precipitate may be dehydrated and then sterilized by heating under pressure at above 130?? C. Suitable water soluble salts are aluminium sulphate, ferrous and ferric sulphate and ferric chloride. The basic calcium compound may be lime milk or calcium hydroxide.
