Chemical-equilibrium-based model for describing the strength of sludge: Taking hydrogen-producing sludge as an example

A new model, based on chemical equilibrium theory, was established to evaluate the strength of sludges in biological wastewater treatment systems. The effectiveness of this model was demonstrated by the experimental results with an anaerobic hydrogen-producing sludge. The equilibrium dispersed mass concentration of the primary particles in the sludge solution was found to nonlinearly increase with the solid content and shear intensity, and could be well described by the model. The Gibbs free energy of adhesion (Delta G degrees) under shear could also be calculated using this model. The equilibrium constant K degrees and Delta G degrees/RT at a shear intensity of 800 1/s were estimated to be 6.54 +/- 0.12 and 1.88 +/- 0.02, respectively. The two parameters could be used to evaluate the strength of the hydrogen-producing sludge. In addition, the effectiveness of the established model was also confirmed by the results with activated sludge in the literature.