Abstract
The complexity of Activated Sludge Model No. 1 (ASM1) is one of the main obstacles slowing its widespread use, particularly among wastewater treatment plant (WWTP) professionals. In this paper, a simplification procedure based on steady-state mass balances is proposed for the conventional activated sludge process (ASP) configuration, consisting of an aerated bioreactor and a perfect settler (without particular compounds in the outlet). The results do, in fact, show perfect suitability to a membrane bioreactor process (MBR). Both organic carbon and nitrogen removal were investigated. The proposed approach was applied to ASM1, and simple analytical expressions of the state variables were obtained. These analytical expressions were then validated by comparison to simulations given by the original ASM1 (implemented in GPS-X software). A strong match (less than 4% of error overall) was obtained between both results in the steady-state; consequently, these analytical expressions may be useful as tools for quickly estimating the main state variables, feeding the filtration models, or identifying the interaction between operating parameters. Moreover, this enables a sensitivity analysis, covering relevant factors such as kinetics or operating parameters. For instance, the sludge retention time (SRT) effect is lower on XBH and XS at high SRT (˃20 days), while it is more pronounced on XP and XI as their variations with SRT are linear.
Highlights
The importance of modeling activated sludge processes (ASPs) for domestic wastewater treatment has increased in recent decades, with the advent of the widely accepted activated sludge models (ASMs) [1]
Even with the use of the continuously stirred tank reactor (CSTR) assumption, a highly nonlinear system of ordinary differential equations is obtained [3]. This complexity is one of the main obstacles holding up the widespread us of ASMs, among wastewater treatment plant (WWTP) professionals asking for model simplification [2,3]
An approach based on steady-state Activated Sludge Model No. 1 (ASM1) mass balances is presented for ASM1 simplification
Summary
The importance of modeling activated sludge processes (ASPs) for domestic wastewater treatment has increased in recent decades, with the advent of the widely accepted activated sludge models (ASMs) [1]. ASMs have shown promising predictive results, but at the expense of complex process models [2]. Even with the use of the continuously stirred tank reactor (CSTR) assumption, a highly nonlinear system of ordinary differential equations is obtained [3]. This complexity is one of the main obstacles holding up the widespread us of ASMs, among WWTP professionals asking for model simplification [2,3]. Different strategies for ASM1 simplification have been adopted, such as model dimension reduction [5,6,7], linearization of reaction rates [8,9], or whole mass balance equations [10]
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