Unified basis for the respirometric evaluation of inhibition for activated sludge

This paper explores the merit of the oxygen uptake rate (OUR) profile obtained by means of respirometry as the basic mechanistic instrument for evaluating activated sludge inhibition. Experimental OUR data are generated using the synthetic peptone-based substrate and inhibition is tested with 60 mg/L hexavalent chromium and 33 mg/L nickel additions, corresponding to EC 50 levels determined using the standard ISO 8192 procedure. Experimental results are evaluated by model calibration using ASM1 modified for dual hydrolysis and ASM3 modified for simultaneous growth. Model evaluations indicate that inhibition affects not only growth, but also other significant microbial mechanisms such as substrate storage and hydrolysis, leading to conclude that the proposed approach will enable to visualize the overall impact of the inhibitory compound on every stage of substrate biodegradation, through inspection and evaluation of the entire OUR profile.