scholarly journals Twenty-five years of ASM1: past, present and future of wastewater treatment modelling

2015 ◽  
Vol 17 (5) ◽  
pp. 697-718 ◽  
Author(s):  
M. C. M. Van Loosdrecht ◽  
C. M. Lopez-Vazquez ◽  
S. C. F. Meijer ◽  
C. M. Hooijmans ◽  
D. Brdjanovic
Keyword(s):  
Activated Sludge ◽  
Urban System ◽  
System Level ◽  
Nitrogen And Phosphorus ◽  
New Developments ◽  
Theoretical Concepts ◽  
Historical Developments ◽  
Activated Sludge Processes ◽  
Activated Sludge Systems ◽  
The Ideal

Activated sludge systems have been applied for 100 years now. Over the course of the years, researchers have developed various models to describe activated sludge processes. The main aim has been to gain a better understanding of the conditions that favour the conversions of carbon, nitrogen and phosphorus present in wastewater, and associated oxygen consumption and sludge production. The current paper presents a reflection on the historical developments, state-of-the-art of activated sludge modelling and future trends. Over the years, many wastewater research groups have benefitted greatly from the development of activated sludge models (ASMs). On one hand, modelling has been expanded through the development of novel theoretical concepts and their application in new fields. On the other hand, models have been used for practical projects. Although, scientists are still searching for the ideal model, one can say that ASMs are developed to the extent that they can be applied in practice with confidence. New developments are expected to be seen regarding plant-wide modelling, integration with other models at the (urban) system level, organizational and computational infrastructure, and interface and communication with various stakeholders and users.

Boston Harbor Clean-Up: Comparison of Conventional Oxygen Activated Sludge with and without Anaerobic Selectors

1992 ◽  
Vol 25 (4-5) ◽  
pp. 281-287 ◽  
Author(s):  
P. T. Bowen ◽  
V. S. Magar ◽  
R. Otoski ◽  
T. McMonagle
Keyword(s):  
Activated Sludge ◽  
Phosphorus Removal ◽  
Pilot Scale ◽  
Ammonia Nitrogen ◽  
Design Parameters ◽  
Boston Harbor ◽  
Nitrogen And Phosphorus ◽  
Nitrogen And Phosphorus Removal ◽  
Activated Sludge Processes ◽  
Treatment Design

To determine secondary treatment design parameters for the Massachusetts Water Resources Authority Deer Island Treatment Facility, a pilot study was conducted. Due to the constricted site, oxygen activated sludge processes were considered. A pilot-scale conventional oxygen activated sludge (COAS) and COAS preceded by an anaerobic selector process (ASP) were compared. Both processes achieved comparable levels of total and soluble BOD, total and soluble COD, total nitrogen, ammonia nitrogen, and phosphorus removal. Higher percent removals occurred during the spring and summer flow periods. Neither process appeared more stable than the other with respect to changing influent loading and hydraulic stress. Differences in the process were the sludge settleability and sludge yield. The ASP had a slightly higher sludge yield than COAS, but the solids settled faster.

The Selector Effect on Filamentous Bulking in Long Sludge Age Activated Sludge Systems

1991 ◽  
Vol 23 (4-6) ◽  
pp. 867-877 ◽  
Author(s):  
D. M. D. Gabb ◽  
D. A. Still ◽  
G. A. Ekama ◽  
D. Jenkins ◽  
G. v. R. Marais
Keyword(s):  
Activated Sludge ◽  
Phosphorus Removal ◽  
Sufficient Conditions ◽  
Extensive Investigation ◽  
Intermittent Aeration ◽  
Nitrogen And Phosphorus ◽  
Nitrogen And Phosphorus Removal ◽  
Aeration System ◽  
Microthrix Parvicella ◽  
Activated Sludge Systems

A survey of long sludge age activated sludge plants in South Africa showed that bulking was widespread in nitrogen and nitrogen and phosphorus removal plants with the dominant causative filamentous organisms being the low F/M types 0092, 0675, 0041, Microthrix parvicella, 0914 and 1851. The literature suggests that in aerobic systems proliferation of the low F/M filaments can be controlled by aerobic selector reactors. From an extensive investigation into the selector reactors, and the effect these stimulate, it was concluded that in long sludge age systems, irrespective of whether or not a selector effect is present in the sludge, (1) under completely aerobic conditions low F/M filaments do not proliferate, (2) sequential or alternating anoxic-aerobic periods like intermittent aeration are necessary, though not sufficient, conditions for the proliferation of low F/M filaments, and (3) an aerobic selector installed on an intermittent aeration system did not control low F/M filament proliferation.

The limits and ultimate possibilities of technology of the activated sludge process

2008 ◽  
Vol 58 (8) ◽  
pp. 1671-1677 ◽  
Author(s):  
A. F. van Nieuwenhuijzen ◽  
A. G. N. van Bentem ◽  
A. Buunnen ◽  
B. A. Reitsma ◽  
C. A. Uijterlinde
Keyword(s):  
Wastewater Treatment ◽  
The Netherlands ◽  
Activated Sludge ◽  
Municipal Wastewater ◽  
Wastewater Treatment Plants ◽  
Treatment Method ◽  
Activated Sludge Process ◽  
Municipal Wastewater Treatment ◽  
Nitrogen And Phosphorus ◽  
Activated Sludge Processes

The (low loaded) biological nutrient removing activated sludge process is the generally accepted and applied municipal wastewater treatment method in the Netherlands. The hydraulical and biological flexibility, robustness and cost efficiency of the process for advanced removal of nutrients like nitrogen and phosphorus without (too much) chemicals results in a wide application of the activated sludge process within Dutch waterboards. Presumably, wastewater treatment plants will have to contribute to the improvement of the quality of the receiving surface waters by producing cleaner effluent. In this perspective, the Dutch research organisation STOWA initiated a research project entitled “The Boundaries of the Activated Sludge Process” to investigate the possibilities and limitations of activated sludge processes to improve the effluent quality. It is concluded that the activated sludge process as applied and operated at WWTP's in the Netherlands has the potential to perform even better than the current effluent discharge standards (10 mg Ntotal/l and 1 mg Ptotal/l). Reaching the B-quality effluent (<5mg Ntotal/l and <0.3 mg Ptotal/l) will be possible at almost all WWTPs without major adjustments under the conditions that:   the sludge load is below 0.06 kg BOD/kg TSS.d   the internal recirculation is above 20   the BOD/N ratio of the influent is above 3. Complying with the A-quality effluent (<2.2 Ntotal/l and <0.15 mg Ptotal/l) seems to be difficult (but not impossible) and requires more attention and insight into the activated sludge process. Optimisation measures to reach the A-quality effluent are more thorough and are mostly only achievable by additional construction works (addition of activated sludge volume, increasing recirculation capacity, etc.). It is furthermore concluded that the static HSA-results are comparable to the dynamic ASM-results. So, for fast determinations of the limits of technology of different activated sludge processes static modelling seems to by sufficient.

scholarly journals Enhanced settling in activated sludge: design and operation considerations

2018 ◽  
Vol 78 (2) ◽  
pp. 247-258 ◽  
Author(s):  
Glen T. Daigger ◽  
Eric Redmond ◽  
Leon Downing
Keyword(s):  
Activated Sludge ◽  
Quality Criteria ◽  
Granular Sludge ◽  
Aerobic Granular Sludge ◽  
Water Quality Criteria ◽  
Subsequent Removal ◽  
Solids Concentration ◽  
Activated Sludge Processes ◽  
Sludge Settleability ◽  
Activated Sludge Systems

Abstract Settling of activated sludge particles has long been the key to successfully achieving secondary treatment. While soluble products can be converted to particulate components via microbial reactions in the activated sludge process, it is the subsequent removal of these particulate components that is the key to achieving ultimate water quality criteria. An understanding of the operating parameters for selecting good settling activated sludge particles was first documented in the 1970s and 1980s. An understanding of the growth pressures that can be imposed on filamentous organisms, and the impacts of selector zones in general, allowed the design and operation of activated sludge processes to routinely achieve good sludge settleability. More recently, research has identified what could be the next evolution in flocculant growth, with the growing interest in aerobic granular sludge. Aerobic granular sludge is purported to provide superior settling properties, and many of the growth pressures identified for aerobic granular sludge are also present in activated sludge systems. These enhanced settling sludge systems are gaining significant interest, but the factors leading to enhanced sludge settleability could be present in historical and existing systems. Three facilities were evaluated that exhibited enhanced settleability (i.e. sludge volume indices of less than 70 mL/g the majority of the time) to determine how these enhanced settling sludges compare to typical settling curves from the literature. The enhanced settling sludge facilities exhibit key differences related to surface overflow rate, return activated sludge (RAS) pumping requirements, and sensitivity to solids concentration that are critical for developing effective settling designs for enhanced settling sludge facilities. As more facilities aim to achieve enhanced settling sludge for intensification of infrastructure, it will be important to carefully consider historic settling curves and to develop site-specific settling criteria when possible.

Nitrate versus Oxygen Utilization Rates in Wastewater and Activated Sludge Systems

1986 ◽  
Vol 18 (6) ◽  
pp. 115-122 ◽  
Author(s):  
Mogens Henze
Keyword(s):  
Activated Sludge ◽  
Oxygen Activity ◽  
Oxygen Utilization ◽  
Active Biomass ◽  
Respiration Rates ◽  
Activated Sludge Processes ◽  
Activated Sludge Systems ◽  
Raw Wastewater

Respiration rates for nitrate and oxygen are compared. Raw wastewaters vary much in these rates and the same holds for activated sludge systems. The denitrifying activity may range from 0-80 per cent of the oxygen activity. It is important to take these variations into consideration, when modelling complex activated sludge processes. Of similar importance are the amounts of active biomass in raw wastewater, as these amounts can exceed those produced in the activated sludge plant itself, and thus significantly can influence the overall composition of the active biomass.

Parameter estimation for activated sludge models with the help of mass balances

1999 ◽  
Vol 39 (4) ◽  
pp. 113-120 ◽  
Author(s):  
O. Nowak ◽  
A. Franz ◽  
K. Svardal ◽  
V. Müller ◽  
V. Kühn
Keyword(s):  
Activated Sludge ◽  
Model Calibration ◽  
Model Parameters ◽  
Mass Balances ◽  
Nitrogen And Phosphorus ◽  
General Validity ◽  
Estimation Of Model Parameters ◽  
Operational Data ◽  
Activated Sludge Systems

Mass balances for carbon (as COD), nitrogen, and phosphorus are excellent tools for the evaluation of WWTPs in order to estimate fluxes of these substances, to compare operational data of different WWTPs with one another and, finally, to draw conclusions of general validity. In the case of activated sludge systems, mass balances can also be very helpful for model calibration, in particular for the ‘Activated Sludge Model No. 1’ (ASM1), because this model is consequently based on balances for COD and nitrogen. Hence, the results of mass balances can be utilised directly for the estimation of model parameters. Accordingly, it is recommended to evaluate the fluxes of COD and nitrogen, before the model calibration is started. By means of mass balances only the state of equilibrium can be described. Therefore, as regards model calibration, only parameters responsible for long-term behaviour can be estimated, i.e. the heterotrophic yield YH, the fraction of biomass yielding particulate organics fP, the heterotrophic decay rate bH and the concentration of particulate inert organics XI in the influent. A correct estimate of these parameters is a prerequisite for the validity of the simulation results, not only in regard to excess sludge production and SRT, but also with respect to the oxygen consumption for carbon removal and, therefore, to denitrification capacity.

Evolution of an ASM2d-like model structure due to operational changes of an SBR process

2006 ◽  
Vol 53 (12) ◽  
pp. 237-245 ◽  
Author(s):  
G. Sin ◽  
P.A. Vanrolleghem
Keyword(s):  
Activated Sludge ◽  
Pilot Scale ◽  
Model Structure ◽  
Nitrogen And Phosphorus ◽  
Nitrogen And Phosphorus Removal ◽  
Biological Behaviour ◽  
System A ◽  
Biological Nitrogen ◽  
Hydrolysis Of ◽  
Activated Sludge Systems

To model biological nitrogen and phosphorus removal systems with an affordable complexity, the ASM2d model structure is based on many assumptions. In this study, some of these assumptions, however, were observed to become invalid when the biological behaviour in the system altered in response to changes in the operation of the system, a pilot-scale N and P removing SBR. Particularly, the three applied operational scenarios resulted in three distinctive responses in the SBR, namely pronounced limitation of the hydrolysis of the organic nitrogen, nitrite build-up during aerobic conditions and also nitrite build-up during anoxic conditions. This shows that even for the same system with the same influent wastewater composition, the model structure of the ASM2d does not remain constant but adapts parallel to dynamic changes in the activated sludge community. On the other hand, the three calibrated ASM2d models still lacked the ability to entirely describe the observed dynamics particularly those dealing with the phosphorus dynamics and hydrolysis. Understanding the underlying reasons of this discrepancy is a challenging task, which is expected to improve the modelling of bio-P removing activated sludge systems.

Fixed film phosphorus removal – flexible enough?

2006 ◽  
Vol 53 (12) ◽  
pp. 75-81 ◽  
Author(s):  
F. Rogalla ◽  
T.L. Johnson ◽  
J. McQuarrie
Keyword(s):  
Activated Sludge ◽  
Phosphorus Removal ◽  
Process Conditions ◽  
Full Potential ◽  
Biological Phosphorus Removal ◽  
Nitrogen And Phosphorus ◽  
Attached Growth ◽  
Fixed Film ◽  
Activated Sludge Processes ◽  
Biological Phosphorus

While biological phosphorus removal (BPR) has been practised for 30 years, up to recently it has been restricted mainly to activated sludge processes, with the corresponding need for large basin volumes. Yet, research with biofilm reactors showed that the principle of alternate anaerobic and aerated conditions was applicable to fixed bacteria by changing the conditions in time rather than in space. Attached growth enhanced biological phosphorus removal (EBPR) systems are attractive because of their compactness and capability to retain high biomass levels. However, the phosphorus extraction depends on backwashes to enhance the phosphorus-rich attached biomass, and correct control of unsteady effluent quality created by frequently modified process conditions. Accordingly, EBPR remains a challenging task in terms of combining nitrogen and phosphorus removal using attached growth systems. Nevertheless, a combination of activated sludge and biofilm carriers, in the integrated fixed-film activated sludge system, provides treatment opportunities not readily available using suspended growth systems. Current practice is only at the beginning of exploiting the full potential of this combination, but the first full-scale results show that compact tankage and low nutrient results based on biological principles are possible.

Activated Sludge Process Models for Treatment of Toxic and Nontoxic Wastes

1986 ◽  
Vol 18 (6) ◽  
pp. 123-137 ◽  
Author(s):  
Anthony F. Gaudy ◽  
Alan F. Rozich ◽  
Elizabeth T. Gaudy
Keyword(s):  
Growth Rate ◽  
Activated Sludge ◽  
Carbon Sources ◽  
Operating Conditions ◽  
Process Models ◽  
Flow Units ◽  
Exogenous Substrate ◽  
Activated Sludge Processes ◽  
Activated Sludge Systems ◽  
Operational Aspects

Design and operational aspects regarding the utilization of activated sludge processes for the treatment of both toxic and nontoxic organic wastes are presented; a key component of the technology concerns the application of a kinetic model which has been shown to be effective for predicting process performance for activated sludge systems treating such carbon sources. After developing an acclimated biomass which is capable of degrading a particular waste, it is prudent to determine the nature, inhibitory or noninhibitory, of the microbial growth rate equation as a function of exogenous substrate concentration. For noninhibitory wastes, one can employ the Monod function for relating µ to S; however, inhibitory wastes require the use of an inhibition function such as the Haldane equation; methods and analytical considerations regarding the evaluation of the biokinetic constants are discussed. The design and operational equations for activated sludge systems treating toxic compounds are developed. Analysis of these equations underscores the significance of the critical, or peak, growth rate, µ*, which is characteristic of systems treating inhibitory wastes. If this growth rate is exceeded in continuous flow units treating toxicants, rapid effluent deterioration and reactor failure can occur; this can be demonstrated analytically and has been verified in pilot plant studies. The predictive power of the model for establishing the critical operating conditions in activated sludge systems is also discussed.

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