Stimulatory Solubilization of Activated Sludge from Refineries by Using High Speed Mixer and Waste Alkaline Solution

Abstract

Solubilization of activated sludge using alkaline waste refinery spent caustic is feasible. Stimulatory solubilization of activated sludge with combinations of a high-speed mixer and alkaline treatment was investigated. A high-speed mixer operated at 12,000 rpm (liquid linear velocity, 15 m/s) containing 0.05 mol/l alkaline solution enabled solubilization of 40% and 50% solubilization after 30 min and 1 h, respectively, or 1.3-1.4 times greater compared with solubilization with only alkaline treatment. Higher temperature (50°C) stimulated solubilization up to 55% after 1 h. A pilot-scale solubilization reactor (1 m³) was constructed. Under the optimum conditions obtained in laboratory scale experiments, about 50% solubilization with "refinery spent caustic" was achieved, similar to that of laboratory experiments, in 1 h, suggesting that such combinations are practically possible.