Aggregation and surface hydrophobicity of selected microorganism due to the effect of substrate, pH and temperature

• Anaerobic-aerobic strategy was used to develop biogranules.
• Consequently, effects of aggregation and surface hydrophobicity were studied.
• Response surface methodology was used to quantitatively determine the effects.
• A statistical model describing the relationship was obtained.

Aggregation and surface hydrophobicity are two important indicators used to evaluate the successful development of biogranules. The effect of substrate concentration, pH, and temperature on these properties of selected bacteria that are isolated from biogranules used in treating textile wastewater was investigated. Statistical response surface methodology was used to quantitatively determine the effects and to determine the relationship between the responses and variables. Thirty experimental runs were performed at substrate concentrations of 500–3000 mg L−1, pH of 5–9, and temperatures of 20–40 °C. The results show that all variables investigated were either positively or negatively correlated with aggregation and surface hydrophobicity and induced significant linear responses in these indicators. Interaction effects were also observed for some of the variables. An acceptable statistical model describing the relationship between aggregation and surface hydrophobicity of the selected bacteria and substrate concentration, pH, and temperature has been developed for the stated experimental conditions.