Influence of fixed mixer toward characteristics of domestic sludge

Abstract Biogranulation is a promising technology for efficient wastewater treatment. This study introduces a spring-shaped fixed mixer to accelerate the biogranulation process by improving sludge characteristics. The aim is to determine the optimal diameter for the mixer that enhances sludge aggregation, surface hydrophobicity, and biomass profile. Spring-shaped mixers with diameters of 1 cm, 3 cm, and 5 cm were tested in a sequence batch reactor. The 1 cm and 3 cm mixers improved surface hydrophobicity by 5%, reaching 79% and 77%, respectively. Additionally, the 1 cm mixer significantly boosted sludge aggregation from 35% to 55%. Although the 5 cm mixer showed the most substantial change in the biomass profile, increasing the MLVSS/MLSS ratio from 0.81 to 0.95, the 1 cm mixer achieved the highest value at 0.98. Smaller diameters enhanced overall sludge characteristics due to increased turbulence and mixing efficiency.