Effects of the Physical Structure of Activated Sludge on Respiration Processes

Abstract

Physical properties and bioactivity are two important aspects of the activated sludge process. To solve the contradiction between these two aspects in the operation control process, the physical structure and respiration processes of sludge in different activated sludge systems were analyzed. Sludge from seven different activated sludge systems was used for the experiments, and the particle size, microscopic morphology, fractal dimension, compression settling performance, adsorption performance, and respirogram were studied and analyzed. The results showed that the correlations between physical performance indicators and respiration rate were very good. Sludge particle size (d) was negatively correlated with the endogenous specific respiration rate (SOURe) and maximum specific respiration rate (SOURt) (R2>0.9); fractal dimension (Df) was linearly and negatively correlated with SOURe and SOURt (R2>0.8); sludge compression index (SCI) and sludge volume index (SVI) were positively correlated with SOURe (R2>0.9); equilibrium adsorption (Qmax) was linearly and negatively correlated with the quasi-endogenous specific respiration rate (SOURq) and SOURe (R2>0.9). In addition, the optimal physical properties and bioactivity range of activated sludge under normal operating conditions were obtained as follows:SVI of 50-120 mL·g-1, SOURe of 6.27-7.55 mg·(g·h)-1, d of 205.80-228.12 μm, Df of 1.56-1.60, Rn/t of 0.02-0.03, and Qmax of 508-636 mg·g-1.