This study deals with respirometric modeling of biodegradation of complex organic matter generated from a chemical industry. Evaluation with a multi-degradation model indicated that organic matter in raw wastewater has four types of biodegradable components having different biodegradation characteristics. The model evaluation of batch respirogram indicated that the acclimated biomass exhibited a delayed response after the addition of raw wastewater to endogenous biomass. The delayed phase was characterized by Haldane type inhibition kinetics. The inhibitory effect of raw wastewater was also supported by standard toxicity test result yielding EC50 at 1.5% dilution.