Novel modeling concept for evaluating the effects of cadmium and copper on heterotrophic growth and lysis rates in activated sludge process

A new modeling concept to evaluate the effects of cadmium and copper on heterotrophic growth rate constant (μH) and lysis rate constant (bH) in activated sludge was introduced. The oxygen uptake rate (OUR) was employed to measure the constants. The results indicated that the μH value decreased from 4.52 to 3.26 d−1 or by 28% when 0.7 mg L−1 of cadmium was added. Contrarily the bH value increased from 0.31 to 0.35 d−1 or by 11%. When adding 0.7 mg L−1 of copper, the μH value decreased to 2.80 d−1 or by 38%. The bH value increased to 0.42 d−1 or by 35%. After regression, the inhibitory effect was in a good agreement with non-competitive inhibition kinetic. The inhibition coefficient values for cadmium and copper were 1.82 and 1.21 mg L−1, respectively. The relation between the bH values and heavy metal concentrations agreed with exponential type well. The heavy metal would enhance bH value. Using these data, a new kinetic model was established and used to simulate the degree of inhibition. It was evident that not only the inhibitory effect on μH but also that the enhancement effect on bH should be considered when heavy metal presented.