Decreasing effect and mechanism of moisture content of sludge biomass by granulation process

Disposal of a high volume of sludge significantly raises water treatment costs. A method for cultivating aerobic granules in a sequencing batch airlift bioreactor to significantly produce lower moisture content is described. Results indicate that optimization of settling time and control of the shear stresses acted on the granules. The diameter of the granule was within the range of 1.0-4.0 mm, and its sludge volume index was stabilized at 40-50 mL g^-1. Its specific gravity was increased by a factor of 0.0392, and specific oxygen uptake rate reached 60.126 mg h^-1 g^-1. Moreover, the percentage of its moisture content in the reactor ranged from 96.73% to 97.67%, and sludge volume was reduced to approximately 60%, greatly due to the presence of extracellular polymeric substances in the granules, as well as changes in their hydrophobic protein content. The removal rate of chemical oxygen demand and reaches up to 92.6% and 98%, respectively. The removal rates of total phosphorus is over 85%. Therefore, aerobic granular sludge process illustrates a good biological activity.