Water Research

The EAWAG Bio-P module for activated sludge model No. 3

Authors: H Siegrist, Leiv Rieger, Gabbie Koch, Martin Kühni, W Gujer

An additional module for the prediction of enhanced biological phosphorus removal is presented on the basis of a calibrated version of ASM3. The module uses modified processes from ASM2d but neglects the fermentation of readily degradable substrate. Biomass decay is modeled in the form of endogenous respiration as in ASM3. The glycogen pool and biologically induced P-precipitation is not taken into account. The module was systematically calibrated with experimental data from various batch experiments, a full-scale WWTP and a pilot plant treating Swiss municipal wastewater. A standard parameter set allowed all data to be simulated.

Q: What problem does this paper attempt to solve?

Kimi: This paper introduces an additional module—the EAWAG Bio-P module—to enhance the predictive capabilities of ASM3 (Activated Sludge Model No. 3), particularly in the area of Enhanced Biological Phosphorus Removal (EBPR). ASM3 is a fundamental activated sludge model primarily used for predicting oxygen consumption, sludge production, nitrification, and denitrification in municipal wastewater treatment systems, but it does not include a biological phosphorus removal process. The development of the EAWAG Bio-P module aims to fill this gap by integrating the biological phosphorus removal process into the ASM3 model for modeling and prediction.

Specifically, the paper attempts to address the following issues:

Modeling of Biological Phosphorus Removal Process: By introducing the EAWAG Bio-P module, the biological phosphorus removal process is integrated into the ASM3 model to enable a more comprehensive simulation and prediction of nitrogen and phosphorus removal in wastewater treatment processes.
Parameter Calibration and Validation: The model is systematically calibrated and validated against experimental data from various batch experiments, full-scale wastewater treatment plants, and pilot plants treating Swiss municipal wastewater, ensuring the accuracy and applicability of the model parameters.
Simplification of Model Complexity: The model is simplified as much as possible while maintaining accuracy, such as neglecting the fermentation process of readily degradable substrates and additional glycogen pools, to reduce the complexity and computational demands of the model.
Adaptation to Different Operating Conditions: The model is calibrated to adapt to different operating conditions and wastewater characteristics, such as the "Monday effect" following low COD loads, and the treatment effects under different Sludge Retention Times (SRTs).
Improving Model Predictive Ability: Through calibration and validation, the model is ensured to accurately predict different dynamic effects, such as normal phosphorus release and uptake in the short term, washout and growth of PAO (Polyphosphate-accumulating organisms) in the long term, and peaks of phosphate in the effluent after short periods of low COD loads.

In summary, the goal of this paper is to develop and validate a model that can accurately simulate and predict the biological phosphorus removal process, in order to better understand and optimize the efficiency of phosphorus removal in municipal wastewater treatment systems.

Q: What are the relevant studies?

Kimi: The paper "The EAWAG BIO-P module for activated sludge model no. 3" references several related studies that contribute to the development and validation of the Bio-P module. Here are some of the key related research works mentioned in the paper:

Henze et al. (2000): This is the original work on the Activated Sludge Model No. 3 (ASM3), which provides the foundation for the EAWAG Bio-P module. It is a comprehensive model for simulating municipal wastewater treatment processes.
Koch et al. (2000): This study presents the calibration and validation of ASM3 for Swiss municipal wastewater, which is crucial for the development of the Bio-P module as it builds upon the calibrated version of ASM3.
Maurer et al. (1999): This research investigates the kinetics of biologically induced phosphorus precipitation in wastewater treatment, which is relevant for understanding the biological processes involved in phosphorus removal.
Mino et al. (1995, 1998): These studies focus on the microbiology and biochemistry of the enhanced biological phosphate removal (EBPR) process, providing insights into the microbial mechanisms that the Bio-P module aims to capture.
Carucci et al. (1999): This work examines the microbial competition for organic substrates and its impact on EBPR systems under changing carbon feed conditions, which is important for the Bio-P module's representation of substrate competition.
Brdjanovic et al. (1998): This study discusses the impact of excessive aeration on biological phosphorus removal from wastewater, which is relevant for understanding the operational conditions that affect phosphorus removal efficiency.
Crocetti et al. (2000): This research identifies polyphosphate-accumulating organisms and develops 16S rRNA-directed probes for their detection and quantification, contributing to the understanding of the specific microorganisms involved in EBPR.
Johansson et al. (1996): This paper models the anaerobic reactor in a biological phosphate removal process, providing a basis for the anaerobic processes included in the Bio-P module.
Kunst (1991): This work investigates enhanced biological phosphorus removal with regard to wastewater treatment, offering practical insights into the application of EBPR in full-scale systems.
Satoh et al. (1996): This study examines the anaerobic substrate uptake by the enhanced biological phosphorus removal activated sludge treating real sewage, contributing to the understanding of substrate dynamics in EBPR systems.
Smolders et al. (1994): This research provides information on the stoichiometry of aerobic metabolism, which is essential for the biochemical processes considered in the Bio-P module.
Van Veldhuizen et al. (1999): This paper models biological phosphorus and nitrogen removal in a full-scale activated sludge process, offering a broader context for the application of the Bio-P module in full-scale systems.

These studies collectively contribute to the development of the EAWAG Bio-P module by providing theoretical foundations, empirical data, and practical insights into the biological and chemical processes involved in enhanced biological phosphorus removal.

Q: How the paper solves this problem?

Kimi: The paper addresses the modeling issue of Enhanced Biological Phosphorus Removal (EBPR) through the following steps:

Model Development: An additional module, the EAWAG Bio-P module, was developed to extend the ASM3 model to include the biological phosphorus removal process. This module is based on a calibrated version of ASM3 and incorporates modified processes from ASM2d, but excludes the fermentation of readily degradable substrates.
Parameter Definition: Four additional state variables were defined in addition to the 13 components already defined in ASM3 to model the biological phosphorus removal process. These variables include inorganic soluble phosphorus (SPO4), phosphorus-accumulating organisms (XPAO), cell-internal storage products (XPHA), and polyphosphate (XPP).
Process Definition: Eleven additional processes related to biological phosphorus removal were described in detail, including the uptake, storage, and release of phosphorus, as well as the aerobic and anoxic growth conditions of phosphorus-accumulating organisms (PAO).
Systematic Calibration: The EAWAG Bio-P module was systematically calibrated using experimental data from various batch experiments, full-scale wastewater treatment plants, and pilot plants treating Swiss municipal wastewater. An iterative approach was used to calibrate highly correlated parameters in groups and validate them with different batch experiments.
Dynamic Effect Simulation: The model is capable of simulating different dynamic effects, such as normal phosphorus release and uptake, washout and growth of PAO, and peaks of phosphate in the effluent after periods of low COD loads (e.g., weekends, rainy days, holidays).
Model Validation: The accuracy of the model was verified through comparisons with experimental data. This includes validation of long-term simulations and short-term dynamic variations (such as diurnal variations).
Simplification and Adaptability: The model design considered simplification of complexity, for example, by neglecting an additional glycogen pool, and adapting the module to typical conditions of Swiss municipal wastewater.

Through these steps, the paper successfully integrates the biological phosphorus removal process into the ASM3 model and enhances the model's capability to predict the efficiency of biological phosphorus removal through calibration and validation with experimental data. This provides wastewater treatment engineers with a powerful tool to optimize design and operation for improved phosphorus removal efficiency.

Q: What experiments were done for the paper?

Kimi: The paper "The EAWAG BIO-P module for activated sludge model no. 3" conducted and utilized a variety of experiments to develop, calibrate, and validate the Bio-P module. Here are the key experiments mentioned in the paper:

Batch Experiments: A series of batch experiments were carried out to study the decay rates of polyphosphate and the endogenous respiration of PAO (Phosphorus-Accumulating Organisms) under aerobic and anaerobic conditions. These experiments helped to estimate the decrease of PAO and were used to calibrate kinetic parameters such as the rate constant for storage of XPHA (qPHA), and the maximum growth rate of XPAO (mPAO).
P-release and P-uptake Experiments: These experiments were performed to determine the maximum P-release as well as the maximum aerobic and anoxic P-uptake. They were conducted during all important phases of the project and were used to fine-tune the stoichiometric parameters, such as the yield of biomass per XPHA (YPAOO2 and YPAO,NO), and the requirement of XPHA per XPP storage (YPHA).
Wash-out and Grow-in Experiments: A series of batch experiments were conducted to examine the maximum decay (bPP, bPAO) and growth rate (mPAO) of PAO, as well as the P-release/P-uptake rates (qPHA, qPP). These experiments were carried out under different flow schemes and influent conditions over a period of 140 days.
Diurnal Variation Experiments: The paper mentions diurnal variation experiments conducted at the Tu¨ﬀenwies pilot plant, which was operated in AAO mode. The initial conditions of the sludge were calculated from previous time periods to simulate the behavior of denitrification and Bio-P over a single diurnal cycle.
Full-scale Experiments: In addition to the batch and pilot plant experiments, the paper also refers to experiments conducted at a full-scale wastewater treatment plant (Neugut WWTP). The plant was modeled as a cascade of CSTRs, and the secondary clarifier was modeled with an inlet zone, a sludge blanket, and a clear water zone. The model was calibrated and validated against data from this plant, particularly focusing on the removal of nitrogen and phosphorus.

These experiments were crucial for the development of the Bio-P module as they provided the empirical data necessary to refine the model's parameters and validate its predictive capabilities for biological phosphorus removal in different operational conditions and scenarios.

Q: What are the points that can be explored further?

Kimi: Although the paper "The EAWAG BIO-P module for activated sludge model no. 3" has made significant advancements in the modeling and prediction of Enhanced Biological Phosphorus Removal (EBPR), there are potential research directions that can be further explored:

Sensitivity Analysis of Model Parameters: While the model has been calibrated, conducting a more in-depth sensitivity analysis of the parameters could reveal which parameters have the greatest impact on the model output, providing guidance for future model adjustments and optimization.
Applicability of the Model Under Different Conditions: The applicability and accuracy of the model may vary under different geographical, climatic, and operational conditions. Testing and validating the model under a broader range of conditions can improve its universality and reliability.
Application of Microbial Ecology and Molecular Biology: Incorporating the latest advances in microbial ecology and molecular biology can provide a deeper understanding of the microbial community structure and functions involved in EBPR, thereby improving the microbiological basis of the model.
Integration of Model with Experimental Data: Utilizing modern sensor technologies and big data analytics to collect and integrate experimental data into the model in real-time can enhance the model's dynamic adaptability and predictive accuracy.
Expansion and Improvement of the Model: Considering the integration of other important biological or chemical processes into the model, such as metabolic pathways of microorganisms, the impact of different pollutants, etc., can improve the complexity and comprehensiveness of the model.
Application of the Model in Practical Engineering: Applying the model to practical engineering design and operational optimization, evaluating its effectiveness in solving real engineering problems, and adjusting it based on feedback from practical applications.
Comparison and Integration with Other Models: Comparing the model with other existing wastewater treatment models, exploring the differences and complementarities between different models, and even considering the combination of the strengths of multiple models to create a more comprehensive wastewater treatment model.
Educational and Training Applications of the Model: Using the model as an educational and training tool to help students and engineers better understand the EBPR process and wastewater treatment technologies.

By pursuing these further explorations, the performance of the model can be continually improved, its application range expanded, and more insights and tools provided for research and practice in the field of wastewater treatment.

Q: Summarize the main points of the paper.

Kimi: The main content of the paper "The EAWAG BIO-P module for activated sludge model no. 3" can be summarized as follows:

Introduction of the EAWAG Bio-P Module: The paper presents an additional module for the Activated Sludge Model No. 3 (ASM3) that predicts Enhanced Biological Phosphorus Removal (EBPR). This module is based on a calibrated version of ASM3 and incorporates modified processes from ASM2d, with the omission of readily degradable substrate fermentation.
Model Definition: The Bio-P module introduces four additional state variables to ASM3's existing 13 components to model biological phosphorus removal. It simplifies the model by neglecting certain processes such as fermentation and additional glycogen pool, focusing on phosphorus-accumulating organisms (PAO) and their role in EBPR.
Calibration and Validation: The module was systematically calibrated using experimental data from batch experiments, a full-scale wastewater treatment plant (WWTP), and a pilot plant. A standard parameter set was developed to simulate all data sets, demonstrating the module's capability to predict nitrogen and phosphorus removal accurately.
Stoichiometry and Kinetics: Detailed stoichiometric and kinetic rate expressions for the soluble and particulate components of ASM3 and the Bio-P module are provided. These expressions are essential for understanding the interactions between different components and processes within the model.
Parameter Calibration: An iterative approach was used to calibrate the model parameters, grouping highly correlated parameters and validating them against WWTP data. The calibration process focused on reducing the number of unidentifiable parameters by evaluating multiple experiments simultaneously.
Experimental Data: The paper discusses various experiments conducted, including batch experiments for PAO decay, P-release and P-uptake, and diurnal variations. These experiments were critical for the development and validation of the Bio-P module.
Model Application: The Bio-P module was applied to simulate different dynamic effects, such as the "Monday effect" and long-term simulations of phosphate concentration changes. The module was successful in modeling these effects with one set of default parameters, with only minor adjustments needed for specific conditions.
Conclusions: The paper concludes that the EAWAG Bio-P module, when extended to ASM3, can accurately predict the removal of nitrogen and phosphorus. The module can simulate various dynamic effects and is expected to reduce calibration efforts in future applications.

Overall, the paper provides a comprehensive approach to enhancing the ASM3 model for predicting EBPR, offering a valuable tool for wastewater treatment plant design and operation.

The EAWAG Bio-P module for activated sludge model No. 3​

The EAWAG Bio-P module for activated sludge model No. 3