Non-filamentous sludge bulking caused by low concentration of dissolved oxygen and phosphorus deficiency and its control

Non-filamentous sludge bulking occurred during sludge acclimation in lab-scale bio-reactors and the characteristics, properties and degrading pollutants capability of non-filamentous sludge were analyzed. Both low DO concentration (0~0.7 mg/L) and low ratio of P/BOD₅ (0.78/100) resulted in excessive proliferation of viscous zoogloea and sludge bulking. SVI was directly proportional to extracellular polysaccharides and was inversely proportional to hydrophobicity of sludge. The sludge bulking could be effectively controlled by increasing DO concentration and P/BOD₅ ratio. Besides, adding some porous padding into viscous bulking sludge was a useful method which might avoid the deterioration of sludge settlement and maintain good performance in the system. The viscous bulking sludge could not be controlled by addition of NaClO.