GB813179A - Improvements relating to purification of trade effluents and waste liquors - Google Patents

Abstract

Phenolic materials in trade effluents or waste liquors are decomposed by anaerobic fermentation with soil bacteria, the bacteria employed having first been cultured in phenol-containing liquor of gradually increasing phenol concentration so that they are capable of decomposing phenols contained in liquids of 2000-4000 parts per million phenol content. The phenolic material may be phenol itself, cresols or salicylic acid, while the effluent may be one from a gas works or from salicylic acid manufacture. The soil bacteria are present in soil, river or pond mud, sewage or natural manure. If settled sewage, i.e. the liquid left after the removal of solid sludge from sewage, is used as the source of the bacteria, it is preferably mixed with an inorganic support, e.g. asbestos pulp or clay. Since sulphate ions are essential for the growth of the soil bacteria, these ions are added in any suitable form, for example so that the sulphate ion concentration corresponds to about 150 p.p.m. CaSO4. The building up of an undesirably high sulphide concentration, by reduction of sulphate ions is avoided by ensuring the presence of some sulphide-binding agent such as iron turnings or filings, or by continuously or periodically drawing off a portion of the fermentation medium. Periodical drawing off of a portion of the fermentation medium also serves to prevent an undue rise in the concentration of phosphate ions. In an example of the culturing of the bacteria, settled sewage is mixed with powdered asbestos and sufficient concentrated phenol solution to bring the phenol content of the mixture to about 150 p.p.m., and the mixture is incubated at 30-32 DEG C. for 63 days. The phenol content of the mixture is then gradually increased by periodically withdrawing 10 per cent. by volume of the liquor and adding more concentrated phenol solution. The phenol content of the mixture is increased by not more than 200 p.p.m. above its previous value at every step until it reaches 2000 p.p.m. While the phenol concentration is being increased, the pH of the mixture is first maintained at 7-8 by addition of ammonia, but, when the concentration of ammoniacal nitrogen reaches 500 p.p.m., sodium carbonate is used instead. In a further example, river mud is incubated at 30-35 DEG C. with diluted waste liquor from a gasworks until the phenol concentration falls to about 50 p.p.m. Then 10 per cent. by volume of the liquor is withdrawn and replaced by more waste liquor so that the phenol concentration rises to 250-300 p.p.m., and the incubation continued until the phenol concentration again falls to about 50 p.p.m. A further 10 per cent. by volume of the liquor is then withdrawn and replaced by waste liquor to increase the phenol concentration to 400 p.p.m. The steps of removing liquor and replacing it by waste liquor to increase the phenol concentration are continued as before until finally the bacteria are able to ferment the phenols in a concentration from 3000 to 4000 p.p.m. The bacteria are then used to ferment waste liquor containing 3000-4000 p.p.m. phenol, using a batch or continuous procedure.