This paper presents the results of an evaluation of a toxicity mitigation control strategy using the IWA simulation benchmark (IWA, 1999a; IWA, 1999b; Copp, 2001). The aim of the proposed strategy is to minimise the impact of a toxic influent shock load on process performance. To do this, the strategy makes use of a respiration rate measurement to detect toxic events and uses an equalisation tank to store toxic influent. A defined control algorithm specific for the benchmark plant was developed and is used to reintroduce the stored influent back into the process stream once the influent is deemed non-toxic. The results of the simulations indicate that the impact of the toxicant can be significantly mitigated through the use of off-line storage and reintroduction of suspected influent.