Evaluation of pH inhibition effect on activated sludge by the pseudo toxic concentration (CPT) concept model

Abstract

It is generally accepted that the inhibition effect of pH on activated sludge follows the non-competitive inhibition kinetics. But the non-competitive inhibition kinetic equation cannot be directly applied to pH inhibition, due to the difficulty in quantification of pH as a term of inhibitor concentration. So, many empirical equations were developed especially for acidic condition to describe pH inhibition effect. In this research, the pseudo toxic concentration (CPT) concept model to quantify pH inhibition effect on activated sludge was proposed and compared with other existed models. Prediction of performance, presented by Prediction Accuracy and Prediction Accuracy Index, showed that the CPT concept model can explain the reduction of the maximum specific growth rate (mu max) more accurately than any other models do at a wide range of pH. The CPT concept model was applicable not only to activated sludge but also to specific microorganism groups, such as nitrifier, less acidophilic species and nitrifying biofilm.

Effect of H2S on N2O Reduction and Accumulation during Denitrification by Methanol Utilizing Denitrifiers

“…Consequently, our results convincingly show that the level of inhibition on N 2 O reduction is strongly correlated with the H 2 S concentration rather than the sulfide. Usually, in the presence of a competitive inhibitor, the maximum enzyme activity can still be reached if sufficient substrate is available. , However, in all Set I batch tests, although the initial N 2 O concentration was substantially in excess, the N 2 O reduction rate measured in Step II (in the presence of H 2 S) was always lower than that in Step I (in the absence of H 2 S), which suggested that inhibition was not competitive inhibition. In contrast, a noncompetitive-type inhibition model , was found to describe the experimental data well, which suggests that H 2 S inhibition on N 2 O reduction was likely due to noncompetitive inhibition.…”

Monitoring of pH inhibition on microbial activity in a continuous flow reactor by pseudo toxic concentration (CPT) concept and time delay model

“…Advantages. The C PT concept model has some virtue, basically as shown below (Ko et al, 2001a(Ko et al, , 2005: † easy to estimate parameters † applicable to acidic and basic wastewater without reformation of the equation † suitable to various kinds of microorganism groups.…”

“…Therefore, many empirical equations were developed to describe pH inhibition on m max (U.S. EPA, 1975;University of Capetown, 1984;Siegrist and Gujer, 1987;Tyagi et al, 1993;Han et al, 2003). Ko et al (2001a) introduced the pseudo toxic concentration (C PT ) concept to describe pH as an inhibitor concentration in the noncompetitive inhibition kinetic equation. The C PT was defined as the squared difference between a threshold pH value and a measured pH value in a reactor.…”

Identification of the adverse effect of nitrate on the phosphate release rate and improvement of EBPR process models

“…The Nelder-Mead simplex method was applied for estimating K I,NO,PAO and other related parameters. The inhibition coefficient was usually estimated with the Lineweaber-Burk method (Ko et al, 2001). However, in this case the value of K I,NO,PAO was too small, so mathematical optimisation was implemented.…”