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

Abstract A new modeling concept to evaluate the effects of cadmium and copper on heterotrophic growth rate constant ( μ H ) and lysis rate constant ( b H ) in activated sludge was introduced. The oxygen uptake rate (OUR) was employed to measure the constants. The results indicated that the μ H 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 b H value increased from 0.31 to 0.35 d −1 or by 11%. When adding 0.7 mg L −1 of copper, the μ H value decreased to 2.80 d −1 or by 38%. The b H 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 b H values and heavy metal concentrations agreed with exponential type well. The heavy metal would enhance b H 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 μ H but also that the enhancement effect on b H should be considered when heavy metal presented.