[Factors influencing bacterial cell-surface hydrophobicity and bacterial adhesion ratio to activated sludge flocs]

With four different strains as the model, effects of different culture medium on cell-surface hydrophobicity (CSH) were investigated, and the relationship between CSH, contact time and adhesion of bacteria to activated sludge flocs was correlated. Results showed that culture medium, culture time and the characteristic of strain itself influenced the CSH of bacteria, and initial CSH, contact time was closely related to bacterial adhesion ratio in activated sludge system. When contact time was relatively short (< 14 h), initial CSH was the main factor influencing bacterial adhesion ratio. A critical value existed for CSH, similar bacterial adhesion ratio was obtained below the critical value; beyond the value, bacterial adhesion ratio was greatly enhanced, which indicated that only strains with initial CSH beyond the critical value could adhere to activated sludge flocs rapidly. When contact time was long enough (> or = 38 h), contact time became the main factor influencing adhesion. When the inoculated bacteria thoroughly adhered to sludge flocs by pre-contact, nutrient supplementation and changing oxygen providing mode did not cause the release of adhered bacteria again.