Sewage treatment process

Claim 1

A CYCLIC PROCESS FOR TREATING SEWAGE SLUDGE TO REDUCE ITS SPECIFIC RESISTANCE TO FILTRATION AND THE MOISTUREHOLDING CAPACITY OF THE INSOLUBLE SOLIDS THEREOF WHICH COMPRISES THE SUCCESSIVE STEPS OF (A) HEATING A PORTION OF SLUDGE PRE-HEATED AS IN STEP (E) UNDER PRESSURE IN A HEATING ZONE INSULATED AGAINST HEAT LOS AND ADAPTED TO PRESSURIZED OPERATION TO A SELECTED TEMPERATURE BETWEEN 100-225*C. BY DIRECT CONTACT WITH A STREAM OF A HOT GAS; (B) DISCONTINUING HEATING OF THE SLUDGE; (C) MAINTAINING THE HEATED SLUDGE UNDER PRESSURE IN THE HEATED ZONE FOR AT LEAST ONE HOUR AT A TEMPERATURE ABOVE 100*C. WHILE PASSING GASEOUS OXYGEN THROUGH THE HEATED SLUDGE DURING AT LEAST THE TERMINAL PORTION OF THE TIME DURING WHICH THE SLUDGE IS MAINTAINED UNDR PRESSURE IN THE HEATED ZONE UNTIL THE SPECIFIC RESISTANCE TO FILTRATION OF THE SLUDGE IN SEC.2/G.X107 IS REDUCED TO LESS THAN 250; (D) REDUCING AT LEAST PARTIALLY THE PRESSURE IN THE HEATING ZONE, (E) VENTING AT LEAST A PORTION OF THE HOT GASES THUS RELEASED THROUGH A SECOND PORTION OF SWEAGE SLUDGE, THEREBY DIRECTLY HEATING THE SECOND PORTION OF SLUDGE; (F) DISCHARGING THE PORTION OF SLUDGE FROM THE PRESSURIZED HEATING ZONE; (G) REPEATING STEPS (B) THROUGH (F) WITH THE SECOND PORTION OF PRE-HEATED SLUDGE.