Optimization of operating conditions in the biological enzymes for efficient waste activated sludge dewatering

Abstract

The sludge dewaterability is essential for waste activated sludge (WAS) treatment and disposal in wastewater treatment plants (WWTPs). The biological enzyme conditioning process is a promising method to enhance the dewaterability of WAS. In this study, the optimal conditions in terms of pH, temperature, bio-enzyme dosage, and treatment time for five kinds of biological enzymes (α-amylase, cellulase, acidic protease, neutral protease, and alkaline protease) were investigated. Among them, α-amylase and neutral protease showed good performance in conditional optimization experiments. After biological enzyme conditioning, the sludge supernatant of proteins, polysaccharides, and SCOD contents increased. The sludge water content (Wc) decreased, while the capillary suction time (CST) increased. The optimal conditions for α-amylase were pH 6, 45 ℃ of temperature, 30 mg/g TSS of dosage, and 3 h of treatment time, under which the lowest Wc can reach 68.67%. The optimal conditions for neutral protease were pH 6.5, 40 ℃ of temperature, 30 mg/g TSS of dosage, and 2 h of treatment time, under which the lowest Wc can reach 69.82%. Using biological enzymes is an environmentally friendly conditioning process for efficient WAS dewatering. The optimization of operating conditions in the biological enzymes conditioning process may be beneficial to WAS dewatering and further disposal in actual WWTPs.