The Influence of COD Fraction Forms and Molecules Size on Hydrolysis Process Developed by Comparative OUR Studies in Activated Sludge Modelling

Abstract

The activated sludge models (ASMs) commonly used by the International Water Association (IWA) task group are based on chemical oxygen demand (COD) fractionations. However, the proper evaluation of COD fractions, which is crucial for modelling and especially oxygen uptake rate (OUR) predictions, is still under debate. The biodegradation of particulate COD is initiated by the hydrolysis process, which is an integral part of an ASM. This concept has remained in use for over 30 years. The aim of this study was to verify an alternative, more complex, modified (Activated Sludge Model No 2d) ASM2d for modelling the OUR variations and novel procedure for the estimation of a particulate COD fraction through the implementation of the GPS-X software (Hydromantis Environmental Software Solutions, Inc., Hamilton, ON, Canada) in advanced computer simulations. In comparison to the original ASM2d, the modified model more accurately predicted the OUR behavior of real settled wastewater (SWW) samples and SWW after coagulation–flocculation (C–F). The mean absolute relative deviations (MARDs) in OUR were 11.3–29.5% and 18.9–45.8% (original ASM2d) vs. 9.7–15.8% and 11.8–30.3% (modified ASM2d) for the SWW and the C–F samples, respectively. Moreover, the impact of the COD fraction forms and molecules size on the hydrolysis process rate was developed by integrated OUR batch tests in activated sludge modelling.

Systematic Modeling of Municipal Wastewater Activated Sludge Process and Treatment Plant Capacity Analysis Using GPS-X

“…For both the nitrogenous and carbonous quality parameters, the obtained simulated values of the Snh for the plant data follow the GPS-X default value of 0.9. The ASM1 model adopted in this study considers both XND and XS as transformed into SS and SND, respectively, via hydrolysis [5,45], which is evident from the presented results. The ASPs are common, operational under carbon-limited conditions with COD/BOD5 ratio as an acceptable index for evaluating the biological treatability efficacy of municipal wastewater [38,44,47].…”

“…The tCOD in wastewater organic matter is divided into biodegradable and non-biodegradable components, Equation (4), with a relative proportion of these components known to influence the efficacy of biological treatment processes [11,12,38,44,45]. However, in biological processes such as ASP, further subdivisions do exist, including active biomass (X BH and X BA discussed under Section 3.3.8) that forms part of the tCOD [12,24,44,45].…”

“…Even though the influence of S s on the efficacy of ASP has been reported intensively, in the literature, investigation on other components of the COD received lesser attention [45,46]. For instance, the X S fraction and/or substrates can be a significant source of the S s in the form of organic colloidal and/or particulate that can significantly influence the processes of COD, nitrogenous compounds removal as well as other wastewater treatment processes [46].…”

“…The biomass is left on its own, and the substrate is generated via a decay and hydrolysis process. The process results in the release of both non-degradable matter X i and nutrients, X ND [5,7,38,45]. Thus, under this phase, the ASM1 mass balance considers only S s , X s , X i , and X BH [45].…”

On the Use of Mathematical Models for Wastewater Treatment: A Review and Analysis of Activated Sludge Models ASM1 and ASM3

“…In order to deal with phosphorus removal, biological (processes of phosphorus-accumulating organisms) and chemical (chemical precipitation of phosphates) processes were included in the model. However, after the publication of ASM2, it has been shown that a fraction of phosphorus-accumulating organisms (PAOs) can denitrify (Gernaey et al, 2004;Drewnowski et al, 2020). Therefore, in 1999, ASM2 International Journal of Environment andGeoinformatics 8(1):001-018 (2021) was expanded into the ASM2d which considers the denitrification caused by PAOs (Makinia et al, 2020).…”