Modelling activated sludge using probabilistic approach

Abstract

In the design and planning of wastewater treatment plant, evaluations of the systems are vital before decisions are made. In order to carry out the assessment without cost-intensive laboratory and pilot tests, numerical models can be used. Extensive studies have been conducted to apply deterministic model in wastewater treatment systems. In this study, the main purpose was to demonstrate the modelling of activated sludge system using probabilistic approach. A sequencing batch reactor (SBR) was simulated using Activated Sludge Model No.1 (ASM1). By adopting the engineering scenario from the study done by Jeppsson (1996), uncertainty analysis was conducted. This study only considered the stoichiometric, kinetic and influent characteristics in the activated sludge process. The following steps were carried out in this study using Matlab by MathWorks: (1) sensitivity analysis of the parameters in ASM1, (2) uncertainty analysis using Monte Carlo tests and (3) representing results using mean, percentiles and cumulative distribution functions. Sensitivity analysis was observed to be very useful in order to eliminate the model parameters which are less influencing in the modelled process. The results from Monte Carlo tests suggested the feasibility of applying probabilistic approach in facilitating decision making process under uncertain conditions. However, the reliability of output predictions should be investigated through further researches.