The pseudo toxic concentration (CPT) concept was introduced as a quantification method to describe pH as an inhibitor concentration. In this research, the applicability of the CPT concept model for the detection of pH inhibitions was expanded for a continuous flow activated sludge reactor. A pilot equipped with an inhibition detection system was installed. Inhibitory wastewater was injected for 1 h and the relative activity was calculated by the maximum respiration rate. At the same time, the coefficients for the CPT concept model were estimated. At the dynamic conditions, the estimated relative activity by the CPT concept model showed time lag compared to the measured one. However, the time lag problem was successfully resolved by introducing a transfer function into the CPT concept model. The CPT concept model combined with a transfer function (CPT + TF model) successfully tracked the variation of the relative activity under dynamic conditions. The CPT + TF model could detect 50% inhibition faster than the respirometry based method by approximately 10 min. Moreover, it had additional advantages such as being inexpensive, easy to install and simple to operate. In conclusion, the CPT + TF model was an effective and convenient detection method of pH inhibition.

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