OPERATING PRESSURE: 180 psig
OPERATING TEMPERATURE: 360°F UNIT CAPACITIES: Up to 100 gpm COOKING DETENTION TIME: 30 min
IMPROVEMENT IN DEWATERING BY HEAT TREATMENT: 200%
SOLIDS CONTENT OF THICKENED, HEAT-TREATED SLUDGE: 7 to 11%
CLARIFIED EFFLUENT BOD: 4500 mg/l or more
COD REDUCTION BY HEAT TREATMENT: 22%
VOLATILE SOLIDS REDUCTION BY HEAT TREATMENT: 28%
MATERIALS OF CONSTRUCTION FOR EQUIPMENT: Carbon steel
Heat treatment followed by filtration is economical for dewatering sludge without using chemicals. Heating sludge at elevated temperatures and pressures causes the cells to rupture, releasing bound water from the sludge particle and the water of hydration. The gel system structure is irreversibly destroyed, and the solids lose affinity for water and are readily separated from the liquid by decantation. The technical term for this process is heat syneresis.
The exact nature of mechanisms that release bound water and water of hydration from the sludge is not fully understood. It is known that coalescence of particles occurs, and that the high-velocity particle collisions (as a function of the energy level at high pressure [180 psig] and temperature [360°F]) disturb the molecules and assist in particle structure breakdown.
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