FIELD: waste disposal. SUBSTANCE: invention relates to treating waste sludges containing considerable amount of water- retaining cell structure resulting from microbiological action using heating at temperature above about 127 C. Preferable treatment temperature is below some 199 C and preferable pressure below about 14.1 kg/sq.cm. Heat treatment is advantageously carried out at direct contact of concentrated waste sludge with steam under pressure. Heat treatment effect may be enhanced by controlling pH to its limiting value, especially to acidic conditions corresponding pH value about 3 or below. It is of use to neutralize concentrated waste sludge before its dehydration and before termination of heat treatment. Essential distinguishing feature of invention is heat treatment of sludge with content of solid substances at least 15 wt %. It is advantageous to use temperature 126-200 C and pressure above atmospheric pressure to maintain sludge in liquid state for at least 15 min, whereupon sludge is neutralized to pH at least 6 and subjected to one more heat treatment. Dehydration is conducted to content of solids higher than 30 wt %. Another embodiment of invention includes two stages instead four: missing are neutralization stage and second steam heat treatment. Neutralization is performed with calcium hydroxide and dehydration via filtration with membrane filter for no longer than 30 min. Minimum treatment time is determined from formula: y = b•m-x where y is treatment time, min, x sludge pH value, b = 9986, and m = 1894. EFFECT: optimized parameters of treatment. 5 cl, 5 tbl
