Effect of recycling the slime layer extracted sludge on the sludge granulation

Abstract

Recycling of extracellular polymeric substances(EPS) has been extensively explored. However, in-situ reuse of EPS-extracted sludge to the sewage treatment system has been rarely reported. After extracting the slime layer of activated sludge, the modified sludge still had favorable microbiological activity, and substrate degradation potential. Compared with the raw sludge, the mass ratio of protein to polysaccharide increased from 1.37 to 1.84, the absolute value of Zeta potential decreased by 25.97%, and the flocculation capacity was improved. Therefore, the modified sludge could to be used in the sewage treatment system and improved its performance. Furthermore, the effects of continuous reuse of modified sludge to DE oxidation ditch system on its performance and sludge properties were studied. The results suggested that the m(PN)/m(PS) increased with the extension of reuse days and the sludge began granulation, and more than 30% of granular sludge was larger than 200 μm, indicating the continuous granulation. Therefore, continuous reuse of modified sludge stripped of slime layer into DE oxidation ditch system can promote sludge granulation, providing a new approach to cultivate granular sludge in continuous flow systems.

Keywords

• slime layer
• modified sludge
• reuse
• granular sludge
• de oxidation ditch