Abstract

Nowadays, appropriate determination of chemical oxygen demand (COD) fractionation together with degradation kinetics of organic compounds have a prime importance on the design and operation of activated sludge systems. Batch respirometric tests based on the oxygen uptake rates (OUR) and corresponding COD is accepted method to reflect the consumption of biodegradable substrates. The influence of the readily biodegradable (Ss) fraction in biological wastewater treatment systems has been extensively investigated, but still isn't known enough about the effects of slowly biodegradable substrate (Xs) on OUR. However, due to high costs of commercial compounds, the effective use of internal biodegradable substrates should be preferred. According to literature data, municipal wastewater after primary treatment contain readily & slowly biodegradable substrates in the amount of approx. 10-30% & 40-60% total COD, respectively. The biodegradation of X S is initiated by hydrolysis which is an integral part of activated sludge models, such as the Activated Sludge Model no. 2d (ASM2d) (Henze et al., 1999). This process is slower than heterotrophic growth and becomes the rate-limiting step for the biodegradation of organic compounds. The aim of this study was to estimate adequate parameters for modeling hydrolysis process of XS based on the OUR tests using the original and modified version of ASM2d. Results of batch respirometric tests obtained at a large biological nutrient removal (BNR) wastewater treatment plant (WWTP) in northern Poland, presented earlier by Drewnowski (2013), provided the experimental database for comparative study of the model predictions. The experimental investigations were supported by both lab-scale and full-scale simulations using a newly developed model as modification of ASM2d.

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