ASM1 Model Research Articles

A Comprehensive View of the ASM1 Dynamic Model: Study on a Practical Case

The ASM1 model was elaborated by the IWA Task Group for Mathematical Modelling, with the aim of explaining and predicting the output values of organic matter concentration in activated sludge processes, especially for domestic wastewaters. In recent years, ASM1 has been completed with new components and extended to other biological processes, including biological membrane reactors, activated carbon filters, and microalgae bioreactors. In this article, the essentials of this model are studied by outlining the original topics that were formulated in the model, and by using a practical example of a wastewater treatment plant (WWTP), which can clarify the application of the ASM1. A protocol of approximation between the dynamic model and the experimental data for the COD effluent concentration is presented, based on three steps of tuning and fine tuning, and the corrected values of the kinetic parameters YH and μH,max are calculated in accordance with the minimum error. In the simulation procedure, the baseline and dynamism are controlled, comparing them to the experimental data line, and the values obtained for the kinetic parameters are YH = 0.60 and μH,max = 0.40 d−1. The kinetic parameters reflect the activity of the mixed community of microorganisms in the WWTP.

Impact of soluble organic matter and particulate organic matter on anammox system: Performance, microbial community and N2O production

In this study, the effects of soluble readily biodegradable COD (sCOD) and particulate slowly biodegradable COD (pCOD) on anammox process were investigated. The results of the long-term experiment indicated that a low sCOD/N ratio of 0.5 could accelerate the anammox and denitrification activity, to reach as high as 84.9%±2.8% TN removal efficiency. Partial denitrification-anammox (PDN/anammox) and denitrification were proposed as the major pathways for nitrogen removal, accounting for 91.3% and 8.7% of the TN removal, respectively. Anammox bacteria could remain active with high abundance of anammox genes to maintain its dominance. Candidatus Kuenenia and Thauera were the predominant genera in the presence of organic matter. Compared with sCOD, batch experiments showed that the introduction of pCOD had a negative effect on nitrogen removal. The contribution of denitrification to nitrogen removal decreased from approximately 14% to 3% with increasing percentage of pCOD. In addition, the analysis result of the process data using an optimized ASM1 model indicated that high percentage of pCOD resulted in serious N2O emission (the peak value up to 0.25 mg N/L), which was likely due to limited mass diffusion and insufficient available carbon sources for denitrification. However, a high sCOD/N ratio was beneficial for alleviating N2O accumulation.

A control strategy for an intermittently aerated and fed bioreactor to reduce aeration costs: A simulation study

The aim of this study was to apply the ASM1 model to predict the aeration cost of an intermittently aerated and fed bioreactor (IAFB) treating domestic wastewater at dissolved oxygen (DO) set points of 1–4 mg/L. In this work, the energy efficiency from the use of a classical Proportional-Integral (PI) DO controller installed in the IAFB system was compared to that of a DO cascade controller. In comparison to classical PI DO controller, a DO cascade controller set at 3 mg/L could reduce energy consumption by up to 16 %, decreasing the nitrification rate by only 5%. Moreover, a DO cascade controller at set point of 2.5 mg/L could lead to less energy consumption compared to a set point of 4.0 mg/L (by 41 %), reducing nitrification rate by only 7%. In particular, DO concentration higher than 3 mg/L can result in a higher air flow rate, which, however, does not drastically improve nitrification rate, causing an overaerated mode of operation, thus significantly increasing the aeration cost. These results indicate that the IAFB system can be accurately simulated through the use of ASM1 model within OpenModelica software, evaluating energy saving consumption scenarios during IAFB system operation.

Determination and evaluation of kinetic parameters of activated sludge biomass from a sludge reduction system treating real sewage by respirometry testing

Oxic-settling-anoxic (OSA) process is one of the promising variants that produces lower amounts of sludge and has been applied to aerobic and nutrient removal systems. The only consequence on this modification is that supplementary research is advisable to fully understand the mechanism, which eventually leads to the development of a more realistic model. This study evaluated the characteristics of an OSA process as a sludge reduction system by calibration of kinetic coefficients of ASM1 model with some modifications. A series of respirometric tests were designed for the assessment of microbial kinetics and for further clarification of sludge reduction mechanism. The calibration results depicted that the decay rate is the most variable kinetic parameter depending on the system configuration. It was determined that this kinetic coefficient increased significantly after the system was modified into OSA configuration while other model parameters were almost kept constant. This may be referred to a change either in the microbial population or in the metabolism of the community. The active biomass ratio in the CAS reactor was found to be around 75%, while it was almost 2 times lower in the side-stream reactor. All results led to a conclusion that OSA process is encouraging endogenous decay and consequently lowers biomass viability in the reactor and achieves excess sludge reduction in the system. All experimental results confirmed that side-stream reactor accelerates decay rate of the community and causes the introduction of sludge with low viability to the main reactor.

Dynamic simulation for wastewater treatment plants management: Case of Souk-Ahras region, north-eastern Algeria

AbstractTreatment performances of two wastewater treatment plants (WWTPs), located in North-Eastern Algeria (Souk-Ahras and Sedrata) were tested using ASM1 model. The model, to be considered as a decision tool for the appropriate management of activated sludge systems, served for the prediction of both WWTP behaviours under different operating conditions. In Sedrata WWTP the first management scenarios is based on an increase of inflow rate, taking into account a new transfer volume from a nearby zone. In a second scenerio, the ultimate flow of 40 000 m3·d-1 is estimated. Regarding Souk-Ahras WWTP, three scenarios were tested. The first tested the impact of an increase of the extraction flow rate and yielded a reduction by 37% of sludge production. The second dealt with the management of the mass budget of substrata and biomass. Finally, the third application was devoted to the estimation of the plant ultimate capacity, estimated to be 60 000 m3·d-1.

Investigation of bio-augmentation of overloaded activated sludge plant operation by computer simulation

Based on the essential role of nitrifiers in nitrification process, bio-augmentation of nitrifiers in activated sludge process via two configurations is proposed to improve nutrient removal under overloaded conditions. In the first configuration a bio-augmentation batch enhanced reactor was applied to activated sludge. To improve nitrogen removal in overloaded plant, side-stream bio-augmented sequential batch reactor was examined as the second configuration. The simulation of overloaded plant without additional aeration tanks as base-case was performed by ASM1 model. The operation of bio-augmentation configurations and overloaded plant with additional aeration tanks were also simulated. The results reveal that nitrification efficiency can be improved up to 88% under 30% overloading condition compared to the base-case by applying the second configuration to the overloaded plant. Second configuration shows a significant potential for nitrification improvement as a result of N-load reduction compared to the main process as well as augmentation of the endogenous nitrifiers.

Nitrification process modeling in intermittent sand filter applied for wastewater treatment

The aim of this study was to propose a nitrification process modeling in an intermittent sand filter (ISF) using the biofilm compartment of Aquatic Systems Simulations (AQUASIM) software and the activated sludge model (ASM1) published by Henze et al. (2000). We verified that the software and the initial modeling of equations were suitable for the nitrification modeling until the hydraulic loading rate of 400Lm−2d−1, organic loading rate of 155.6gCODm−2d−1 and nitrogen loading rate of 20.4gN-NH4+-Nm−2d−1. In order to adapt the modeling for all hydraulic loading rates (HLR) studied, the set of equations was complemented with the inclusion of an F factor. This factor adapts the ASM1 model to the condition of lesser interaction between influent and the biofilm due to hydraulic loading rate increasing. Thus, the AQUASIM software along with the proposed new modeling was able to simulate the process for all HLR ranging from 100 to 800Lm−2day−1.

Modeling of Activated Sludge with ASM1 Model, Case Study on Wastewater Treatment Plant of South of Isfahan

ASM1 model is one of the most widely used models of activated sludge process which is the interest of researchers. This model was first proposed in 1987 by the IAWQ group and it is the first formal model of activated sludge. In this research, to evaluate the consistent of model's result with the reality, the data of wastewater treatment plant of south of Isfahan was used. This treatment plant covers a population about 800000 people, and the activated sludge method is used for treating municipal wastewater. The components of ASM1 mode such as fast biodegradable substrate parameters (Ss) and slow biodegradable (Xs) and the concentration of total COD, total nitrogen, suspended solids, nitrate nitrogen and Kjeldahl nitrogen were measured within 68 days and were included in the model. For modeling, the STOAT software was used where the ASM1 model was implemented. To calibrate the model, four cases from bio-kinetic coefficients of ASM1 model was obtained based on the results and the model was corrected in the default values. These coefficients include maximum specific growth rate (µm), decay coefficient (Kd), yield coefficient(Y), and saturation constant (Ks). The model results were consistent with the reality‎.

Integrating ultrasonic disintegration in activated sludge wastewater treatment plant modeling

This paper presents an integrated mathematical model that is capable of predicting and assessing the impact of ultrasonic (US) treatment on the excess activated sludge production in an activated sludge wastewater treatment system. Biological processes in the reactor are simulated in Matlab®/Simulink by the ASM1 model into which two algebraic equations, which capture the US treatment, are integrated. Calibration and validation data series come from a pilot plant installed at two locations, i.e. at a communal wastewater treatment plant (Mechelen-Noord) and at an industrial food flavor production site Haasrode, both located in the Flanders region of Belgium. The results show that the built-up model is capable of correctly predicting excess sludge reduction in the treatment system (which is a sequencing batch reactor in both cases). A reduction of approximately 42% for the communal case study can be reported, while the result obtained for the industrial case study, characterized by a very high organic loading, is quite comparable, i.e. about 38%. The latter represents a huge amount of excess sludge avoided given the nominally very high sludge production rate. The model can now be exploited to maximize the excess sludge reduction while minimizing the US operational costs.

Optimization de la producción de lodos en un sistema de lodos activados a través de la calibración del modelo ASM1

Recently several protocols have been proposed for the calibration the ASM1 model and each one of them emphasizes obtaining a good adjustment in the production of sludge. Precisely here is where the discrepancies are evaluated and adjustments made to data, through a mass balance. The objective of this work was to conduct first a balance of flows in the wastewater treatment plant “Dulces Nombres” in Monterrey, Nuevo Leon, Mexico, and then adjust them until closing properly the mass balance for the total phosphorus, total suspended solids, and inorganic suspended solids (ISS). On might say that to calibrate the biological model was important to determine reliably the flow of sludge (QWAS) since on it depends the cell retention mean time (θC) in the reactor; this was accomplished successfully through the balance of the ISS and using of GPS-X software for the simulation of scenarios of optimization.

Development of an ASM1 dynamic simulation model for an activated sludge process in United Arab Emirates

The current study develops an ASM1-based dynamic simulation model for the activated sludge process of a major sewage treatment plant located in the United Arab Emirates. As a first step towards the model calibration and validation, two campaigns of field measurements and lab-controlled experiments were conducted to estimate a number of kinetic and stoichiometric parameters required by the ASM1 model. The first campaign was during the winter season with average temperature of 25°C and the second was during the summer season with average temperature of 39°C. Each campaign involved collection of composite samples at every hour for five consecutive days and analyzed for several variables including COD, BOD5, SS, VSS, TOC, TN, TKN, NH4-N, NO3-N, and NO2-N. Parameters for reaction kinetics and stoichiometry were determined based on winter measurements using respirometry techniques recommended by different studies. The paper reports the values of these parameters in addition to results of the dynamic calibration of ASM1 conducted using GPS-X simulation environment. A steady-state simulation was first conducted to fit the modeled sludge production to the sludge production calculated from plant average data collected during the measurement campaign. The model validation was conducted considering summer measurements after modifying a number of temperature-dependent parameters. The results indicated reasonable agreement between the measured and simulated effluent variables of COD, TSS, and NH4-N.

Simplifications of Activated Sludge Model with preservation of its dynamic accuracy

The complexity of ASM1 model is a major obstacle for their effective use in control and monitoring algorithms. In wastewater treatment plants, the effluent is in addition subjected to hydrodynamic phenomena which enhance the model complexity. The aim of model reduction is to circumvent this problem by eliminating parts of a model that are unimportant for dynamic model accuracy. In this study different ways to simplify ASM1 model simulated in BSM1 conditions are presented. The method is based on physical considerations that are analyzed separately. The simplifications finally provide really important loss of accuracy on compounds of interest, highlighting the lack of relevant simplified model.

Probabilistic parameter estimation of activated sludge processes using Markov Chain Monte Carlo

One of the most important challenges in making activated sludge models (ASMs) applicable to design problems is identifying the values of its many stoichiometric and kinetic parameters. When wastewater characteristics data from full-scale biological treatment systems are used for parameter estimation, several sources of uncertainty, including uncertainty in measured data, external forcing (e.g. influent characteristics), and model structural errors influence the value of the estimated parameters. This paper presents a Bayesian hierarchical modeling framework for the probabilistic estimation of activated sludge process parameters. The method provides the joint probability density functions (JPDFs) of stoichiometric and kinetic parameters by updating prior information regarding the parameters obtained from expert knowledge and literature. The method also provides the posterior correlations between the parameters, as well as a measure of sensitivity of the different constituents with respect to the parameters. This information can be used to design experiments to provide higher information content regarding certain parameters. The method is illustrated using the ASM1 model to describe synthetically generated data from a hypothetical biological treatment system. The results indicate that data from full-scale systems can narrow down the ranges of some parameters substantially whereas the amount of information they provide regarding other parameters is small, due to either large correlations between some of the parameters or a lack of sensitivity with respect to the parameters.

State estimation for large-scale wastewater treatment plants

Many relevant process states in wastewater treatment are not measurable, or their measurements are subject to considerable uncertainty. This poses a serious problem for process monitoring and control. Model-based state estimation can provide estimates of the unknown states and increase the reliability of measurements. In this paper, an integrated approach is presented for the optimization-based sensor network design and the estimation problem. Using the ASM1 model in the reference scenario BSM1, a cost-optimal sensor network is designed and the prominent estimators EKF and MHE are evaluated. Very good estimation results for the system comprising 78 states are found requiring sensor networks of only moderate complexity.

Simulating ultrasonic activated sludge disintegration for excess sludge reduction in SBR systems

This paper presents an integrated mathematical model that is capable of predicting and assessing the impact of ultrasonic (US) treatment on the excess activated sludge production in a sequencing batch reactor (SBR) system. Such a model can be exploited to maximize the excess sludge reduction while minimizing the US operational costs in biological wastewater treatment systems. Biological processes in the reactor are simulated in Matlab®/Simulink by the ASM1 model into which two algebraic equations, which capture the US treatment, are integrated. Validation data series come from a pilot plant installed at two locations, i.e., at a communal wastewater treatment plant and at an industrial production site of a food flavor producing factory in Haasrode both in the Flanders region in Belgium. The results show that the excess sludge reduction from the SBR can be correctly predicted. A reduction of nearly 42% for the communal case study can be reported, while preliminary results for the industrial case study, characterized by a very high organic loading, are even more promising.

Mathematical Modeling of Carbon Removal in the High-Rate Activated Sludge System: Model Presentation and Application

Mathematical Modeling of Carbon Removal in the High-Rate Activated Sludge System: Model Presentation and ApplicationThis paper discusses the development of a modified ASM1 model to better describe the overall removal of organic substrate from the high-rate activated sludge (HRAS) processes. This model will include process mechanisms for flocculation of particulate and colloidal substrate, hydrolysis, and production of extracellular polymeric substances (EPS). Consideration has also been given to the...Author(s)Thomas M. NogajAndrew A. RandallJose A. JimenezImre TakacsCharles B. BottMark W. MillerSudhir MurthyBernhard WettSourceProceedings of the Water Environment FederationDocument typeConference PaperPublisherWater Environment FederationPrint publication date Oct, 2013ISSN1938-6478DOI10.2175/193864713813673730Volume / Issue2013 / 16Content sourceWEFTECCopyright2013Word count137

Activated sludge pilot plant: Comparison between experimental and predicted concentration profiles using three different modelling approaches

This paper presents an experimental and numerical study of an activated sludge channel pilot plant. Concentration profiles of oxygen, COD, NO 3 and NH 4 have been measured for several operating conditions. These profiles have been compared to the simulated ones with three different modelling approaches, namely a systemic approach, CFD and compartmental modelling. For these three approaches, the kinetics model was the ASM-1 model ( Henze et al., 2001). The three approaches allowed a reasonable simulation of all the concentration profiles except for ammonium for which the simulations results were far from the experimental ones. The analysis of the results showed that the role of the kinetics model is of primary importance for the prediction of activated sludge reactors performance. The fact that existing kinetics parameters in the literature have been determined by parametric optimisation using a systemic model limits the reliability of the prediction of local concentrations and of the local design of activated sludge reactors.

Modeling nitrogen removal for a denitrification biofilter

Nitrous oxide (N2O) is a major greenhouse gas, heavily contributing to global warming. N2O is emitted from various sources such as wastewater treatment plants, during the nitrification and denitrification steps. ASM models, which are commonly used in wastewater treatment, usually consider denitrification as a one-step process (NO3- directly reduced to N2) and are as such unable to provide values for intermediate products of the reaction like N2O. In this study, a slightly modified ASM1 model was implemented in the GPS-X software to simulate the concentration of such intermediate products (NO2-, NO and N2O) and to estimate the amounts of gaseous N2O emitted by the denitrification stage (12 biofilters) of the Seine-Centre WWTP (SIAAP, Paris). Simulations running on a 1-year period have shown good agreements with measured effluent data for nitrate and nitrite. The calculated mean value for emitted N2O is 4.95 kgN-N2O/day, which stands in the typical range of estimated experimental values of 4-31 kgN-N2O/day. Nitrous oxide emissions are usually not measured on WWTPs and so, as obtained results show, there is a certain potential for using models that quantify those emissions using traditionally measured influent data.

Modelling a full scale membrane bioreactor using Activated Sludge Model No.1: challenges and solutions

A full-scale membrane bioreactor (1,600 m(3) d(-1)) was monitored for modelling purposes during the summer of 2006. A complete calibration of the ASM1 model is presented, in which the key points were the wastewater characterisation, the oxygen transfer and the biomass kinetics. Total BOD tests were not able to correctly estimate the biodegradable fraction of the wastewater. Therefore the wastewater fractionation was identified by adjusting the simulated sludge production rate to the measured value. MLVSS and MLSS were accurately predicted during both calibration and validation periods (20 and 30 days). Because the membranes were immerged in the aeration tank, the coarse bubble and fine bubble diffusion systems coexisted in the same tank. This allowed five different aeration combinations, depending whether the 2 systems were operating separately or simultaneously, and at low speed or high speed. The aeration control maintained low DO concentrations, allowing simultaneous nitrification and denitrification. This made it difficult to calibrate the oxygen transfer. The nitrogen removal kinetics were determined using maximum nitrification rate tests and an 8-hour intensive sampling campaign. Despite the challenges encountered, a calibrated set of parameters was identified for ASM1 that gave very satisfactory results for the calibration period. Matching simulated and measured data became more difficult during the validation period, mainly because the dominant aeration configuration had changed. However, the merit of this study is to be the first effort to simulate a full-scale MBR plant.

Reaction rate constants and mean population percentage for nitrifiers in an alternating oxidation ditch system

This paper presents a methodology for the determination of reaction rate constants for nitrifying bacteria and their mean population percentage in biomass in an alternating oxidation ditch system. The method used is based on the growth rate equations of the ASM1 model (IWA) (Henze et al. in Activated sludge models ASM1, ASM2, ASM2d, and ASM3. IWA Scientific and Technical Report no. 9, IWA Publishing, London, UK, 2000) and the application of mass balance equations for nitrifiers and ammonium nitrogen in an operational cycle of the ditch system. The system consists of two ditches operating in four phases. Data from a large-scale oxidation ditch pilot plant with a total volume of 120 m(3) within an experimental period of 8 months was used. Maximum specific growth rate for autotrophs (μ(A)) and the half-saturation constant for ammonium nitrogen (K(NH)) were found to be 0.36 day(-1) and 0.65 mgNH(4)-N/l, respectively. Additionally, the average population percentage of the nitrifiers in the biomass was estimated to be around 3%.