Leiv Rieger

• Ph.D., P.Eng.
• Wastewater Technology Fellow at Jacobs Engineering Group Inc

The objective of this paper is to demonstrate the importance of incorporating more realistic energy cost models (based on current energy tariff structures) into existing water resource recovery facilities (WRRFs) process models when evaluating technologies and cost-saving control strategies. In this paper, we first introduce a systematic framework...

Aeration control at wastewater treatment plants based on ammonia as the controlled variable is applied for one of two reasons: (1) to reduce aeration costs, or (2) to reduce peaks in effluent ammonia. Aeration limitation has proven to result in significant energy savings, may reduce external carbon addition, and can improve denitrification and biol...

This work critically reviews modelling concepts for standard activated sludge wastewater treatment processes (e.g. hydrolysis, growth and decay of organisms, etc.) for some of the most commonly used models. Based on a short overview on the theoretical biochemistry knowledge this review should help model users to better understand i) the model conce...

To ensure correctly operating control systems, the measurement and control equipment in WWTPs must be mutually consistent. The dynamic simulation of activated sludge systems could offer a suitable tool for designing and optimising control strategies. Ideal or simplified sensor models represent a limiting factor for comparability with field applicat...

In this paper, we propose a statistical theoretical framework for incorporation of sensor and actuator faults in dynamic simulations of wastewater treatment operation. Sensor and actuator faults and failures are often neglected in simulations for control strategy development and testing, although it is well known that they represent a significant o...

Current practice to enhance resilience in Water Resource Recovery Facilities (WRRFs) is to ensure redundancy or back-up for most critical equipment (e.g. pumps or blowers). Model-based assessment allows evaluation of different strategies for quantitatively and efficiently enhancing resilience and justifying the allocation of resources. The goal of...

Enhanced biological phosphorus removal (ebpr) Full-scale wastewater treatment plant (wwtp) Metabolic modelling Polyphosphate accumulating organisms (PAOs) and process optimisation a b s t r a c t This study evaluates the predictive capacity of the META-ASM model, a new integrated metabolic activated sludge model, in describing the long-term perform...

This study demonstrates that META-ASM, a new integrated metabolic activated sludge model, provides an overall platform to describe the activity of the key organisms and processes relevant to biological nutrient removal (BNR) systems with a robust single-set of default parameters. This model overcomes various shortcomings of existing enhanced biolog...

While enhanced biological phosphorus removal (EBPR) is widely utilized for phosphorus (P) removal from wastewater, understanding of efficient process alternatives that allow combined biological P removal and shortcut nitrogen (N) removal, such as nitritation-denitritation, is limited. Here, we demonstrate efficient and reliable combined total N, P,...

While enhanced biological phosphorus removal (EBPR) is widely utilized for phosphorus (P) removal from wastewater, understanding of efficient process alternatives that allow combined biological P removal and shortcut nitrogen (N) removal, such as nitritation-denitritation, is limited. Here, we demonstrate efficient and reliable combined total N, P,...

Gas-liquid mass transfer in wastewater treatment processes has received considerable attention over the last decades both from academia and industry. Indeed, improvements in modelling gas-liquid-mass transfer can bring huge benefits in terms of reaction rates, plant energy expenditure, acid-base equilibria and greenhouse gas emissions. Despite thes...

Ammonia-based aeration control (ABAC) is a cascade control concept for controlling total ammonia nitrogen (NHx-N) in the activated sludge process. Its main goals are to tailor the aeration intensity to the NHx-N loading and to maintain consistent nitrification, to meet effluent limits but minimize energy consumption. One limitation to ABAC is that...

The wastewater industry is currently facing dramatic changes, shifting away from energy-intensive wastewater treatment towards low-energy, sustainable technologies capable of achieving energy positive operation and resource recovery. The latter will shift the focus of the wastewater industry to how one could manage and extract resources from the wa...

This paper introduces the application of a fully dynamic air distribution model integrated with a biokinetic process model and a detailed process control model. By using a fully dynamic air distribution model, it is possible to understand the relationships between aeration equipment, control algorithms, process performance, and energy consumption,...

Inhalt (Auszüge…) Fertigungsautomation – Plant Lifecycle Management Multidimensionale Datenmodellierung und Analyse zur Qualitätssicherung in der Fertigungsautomatisierung . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 B. Lindemann, N. Jazdi, M. Weyrich, Institut für Automatisierungstechnik und Softwar...

A model-based treatment performance and energy audit of the Girona WRRF in Spain was conducted using advanced and fully dynamic air supply models. The focus of the study was on the aeration system, which represents 63% of the plant's energy consumption. A dynamic model consisting of a process, a realistic controller, and a very detailed air supply...

During the design of a water resource recovery facility, it is becoming industry practice to use simulation software to assist with process design. Aeration is one of the key components of the activated sludge process, and is one of the most important aspects of modelling wastewater treatment systems. However, aeration systems are typically not mod...

Aeration is an essential component of aerobic biological wastewater treatment and is the largest energy consumer at most water resource recovery facilities. Most modelling studies neglect the inherent complexity of the aeration systems used. Typically, the blowers, air piping, and diffusers are not modelled in detail, completely mixed reactors in a...

L’analyse du fonctionnement des stations d’épuration, et a fortiori l’utilisation d’outils de modélisation dynamique de ce fonctionnement, s’appuient sur un ensemble de données issues de mesures pouvant être entachées d’erreurs. Ces données, acquises pour l’autosurveillance de l’installation ou pour son exploitation, doivent donc être validées de m...

During the design of a water resource recovery facility (WRRF), it is becoming industry practice for process engineers to use simulation software to assist with the design of the plant and its aeration system. The aeration process is one of the key components of the activated sludge process, and as such, is one of the most important aspects of mode...

A new model-based methanol dosage controller for multi-stage Water Resource Recovery Facilities (WRRF) is presented and compared with classic control approaches. The new controller uses self-tuning observer models to predict the concentration of methanol consuming organisms (methylotrophs) and subsequently the remaining methanol concentration in th...

The paper presents a case study demonstrating the importance of taking energy tariff structures and equipment efficiency curves into account when comparing control solutions in water resource recovery facilities (WRRF). In most energy studies, the energy consumption is multiplied by an average energy price (Aymerich et al., 2015). However, energy c...

The paper demonstrates the impact of equipment efficiencies and energy tariffs on the operating costs of a Water Resource Recovery Facility (WRRF). An example is given using a simulation benchmark environment using models for pumps and blowers with reduced efficiencies in the lower flow ranges. In the example, two ammonia-based aeration controllers...

This paper describes an integrated approach for designing, testing and implementing process control solutions for Water Resource Recovery Facilities (WRRFs) using a novel simulation platform. The user-friendly modeling and simulation environment encapsulates expert knowledge and standardizes typical tasks and goes far beyond classic simulators in t...

During the design of a water resource recovery facility (WRRF), it is becoming industry practice for process engineers to use simulation software to assist with the design of the plant and its aeration system. The aeration process is one of the key components of the activated sludge process, and as such, is one of the most important aspects of mode...

A new model-based methanol dosage controller for multi-stage Water Resource Recovery Facilities (WRRF) is presented and compared with classic control approaches. The new controller uses self-tuning observer models to predict the concentration of methanol consuming organisms (methylotrophs) and subsequently the remaining methanol concentration in th...

Key developments of instrumentation, control and automation (ICA) applications in wastewater systems during the past 40 years are highlighted in this paper. From the first ICA conference in 1973 through to today there has been a tremendous increase in the understanding of the processes, instrumentation, computer systems and control theory. However,...

Increasingly stringent effluent limits and an expanding scope of model system boundaries beyond activated sludge has led to new modelling objectives and consequently to new and often more detailed modelling concepts. Nearly three decades after the publication of Activated Sludge Model No1 (ASM1), the authors believe it is time to re-evaluate wastew...

Increasingly stringent effluent limits and an expanding scope of model system boundaries beyond activated sludge has led to new modelling objectives and consequently to new and often more detailed modelling concepts. Nearly three decades after the publication of Activated Sludge Model No1 (ASM1), the authors believe it is time to re-evaluatewastewa...

The control of one-step partial nitritation/anammox or deammonification reactors is challenging because of the competing reactions of the anammox, ammonia-oxidizing, nitrite-oxidizing, and denitrifying bacteria that reside in this reactor environment. Nitrite, a byproduct of such reactions, under certain environmental conditions may be toxic to ana...

Different aeration control strategies were investigated to promote simultaneous nitrification-denitrification (SND) in laboratory-scale sequencing batch reactors and a continues-flow pilot plant. The aeration strategies evaluated during this study included: 1) Constant low DO control, 2) Ammonia (NH4+)-based aeration control and 3) NH4+ -based aera...

The control of one-step partial nitritation/anammox or deammonification reactors is challenging because of the competing reactions of the anammox, ammonia-oxidizing, nitrite-oxidizing, and denitrifying bacteria that reside in this reactor environment. Nitrite, a byproduct of such reactions, under certain environmental conditions may be toxic to ana...

Different aeration control strategies were investigated to promote simultaneous nitrification-denitrification (SND) in laboratory-scale sequencing batch reactors and a continues-flow pilot plant. The aeration strategies evaluated during this study included: 1) Constant low DO control, 2) Ammonia (NH4⁺)-based aeration control and 3) NH4⁺-based aerat...

Wastewater Treatment Process Modeling, Second Edition provides expert guidance to ensure that process models are developed, used, and documented correctly. This authoritative guide helps process engineers understand general modeling concepts and terminology and offers practical details on how to use process models for the design of small, medium, a...

presentation slides from a talk given by Lina Belia at a WEF 100 years of activated sludge conference

Although mathematical modelling of activated sludge systems has become a widely accepted engineering tool, model results are only useful if the model predictions are reliable. The level of detail and quality required for simulation studies varies greatly depending on the project objectives, the resources committed to the project and the available e...

Mathematical modelling of activated sludge systems is used widely for plant design, optimisation, training, controller design and research. The quality of simulation studies varies depending on the project objectives, finances and expertise available. Consideration has to be given to the model accuracy and the amount of time required to carry out a...

Aeration control at wastewater treatment plants based on ammonia as the controlled variable has proven to result in significant energy savings, may reduce external carbon addition, and can improve denitrification and bio-P performance. Ammonia control mainly has been based on feedback control, limiting aeration to prevent complete nitrification, by...

A simulation project was conducted for HRSD's Nansemond WWTP to evaluate the savings potentials for different aeration control strategies based on ammonia and DO measurements. Special emphasis was put on modeling and analyzing plant constraints including blower minimum and maximum capacities, diffuser specifications, and mixing requirements. The re...

When implementing real-time process control systems at wastewater treatment plants (WWTPs), several technical problems may have to be addressed. Sensors have to be reliable. Controllers should be properly designed and tuned. Fault detection should be implemented and safety nets designed. Actuators must have adequate control authority to deal with c...

On-line, real-time collection of measurements remains a key challenge in water quality monitoring and control due to unknown and varying quality of on-line sensor data. Today’s data quality assessment is typically based on a comparison of sensor-based measurements and grab samples of the sampled solution taken next to the on-line analyzer and analy...

Aeration consumes about 60% of the total energy use of a wastewater treatment plant (WWTP) and therefore is a major contributor to its carbon footprint. Introducing advanced process control can help plants to reduce their carbon footprint and at the same time improve effluent quality through making available unused capacity for denitrification, if...

This outline paper aims to provide a critical review of secondary settling tank (SST) modelling approaches used in current wastewater engineering and develop tools not yet applied in practice. We address the development of different tier models and experimental techniques in the field with a particular emphasis on works published since the referenc...

Building an aeration system requires a major investment, with blowers typically being the single most costly piece of equipment at a WWTP. Aeration is also responsible for about 50-60 % of the total energy demand for an activated sludge plant. Moreover the DO concentration controls which processes are active or kinetically limited. The investment a...

Sludge disposal is one of the main cost factors in wastewater treatment. Endogenous processes produce inert materials (endogenous decay products) which contribute a large fraction of the sludge produced in activated sludge treatment. There is evidence that endogenous decay products are degradable under certain conditions. However, a serious knowled...

Le groupe de travail Good Modelling Practice de l’IWA a analysé les pratiques et l’expérience en matière d’utilisation des outils de modélisation du fonctionnement des boues activées, et a élaboré une procédure afin de mener à bien un projet de modélisation, de manière systématique, et en concertation avec l’ensemble des partenaires du projet. Le p...

The IWA Task Group on Good Modelling Practice (GMP) has analysed current practice and experience on the use of activated sludge models. The group developed a framework to make modelling more straightforward and that helps structuring the interaction between modellers and the project stakeholders. The GMP protocol is a synthesis of existing procedur...

This study aims at synthesizing experiences in the practical application of ASM type models. The information is made easily accessible to model users by creating a database of modelling projects. This database includes answers to a questionnaire that was sent out to model users in 2008 to provide inputs for a Scientific and Technical Report of the...

Several methods to detect faults have been developed in various fields, mainly in chemical and process engineering. However, minimal practical guidelines exist for their selection and application. This work presents an index that allows for evaluating monitoring and diagnosis performance of fault detection methods, which takes into account several...

Die Erfassung des Zustandes natürlicher Gewässer ist eine aktuelle Herausforderung an die Wasserwirtschaft. Wassergütemessstationen, mit denen der Gewässerzustand an ausgewählten Punkten kontinuierlich überwacht werden kann, sind hierbei wichtige Werkzeuge. Sie werden eingesetzt, um diverse Eigenschaften des Wassers, z.B. Sauerstoffgehalt, Temperat...

Significance: In activated sludge processes the aeration system can consume over 60% of the total energy demand of the facility and is also a significant process variable to control nutrient removal. It is essential to properly design the aeration system as a whole including equipment (blowers, diffusers, control valves), range of operating conditi...

Mathematical process modeling is used extensively in research, plant design, optimization, training, and model-supported design of process control strategies. The IWA Task Group on Good Modelling Practice (GMP, https://iwa-gmp-tg.cemagref.fr/) has analyzed current practice and experience (Hauduc et al., 2009) and out of this evaluation developed a...

The implementations of water quality monitoring networks have a number of inherent engineering challenges and the automation of the data collection and analysis only adds to that complexity. This paper has been written to discuss the challenges and solutions that have been developed within the framework of an industrial/academic partnership. Water...

Model results are only as good as the data fed as input or used for calibration. Data reconciliation for wastewater treatment modeling is a demanding task, and standardized approaches are lacking. This paper suggests a procedure to obtain high-quality data sets for model-based studies. The proposed approach starts with the collection of existing hi...

The quality of simulation results can be significantly affected by errors in the published model (typing, inconsistencies, gaps or conceptual errors) and/or in the underlying numerical model description. Seven of the most commonly used activated sludge models have been investigated to point out the typing errors, inconsistencies and gaps in the mod...

Many unit process models are available in the field of wastewater treatment. All of these models use their own notation, causing problems for documentation, implementation and connection of different models (using different sets of state variables). The main goal of this paper is to propose a new notational framework which allows unique and systema...

The COD:TKN ratio in the influent wastewater to the J.D Phillips Water Reclamation Facility (WRF) in Colorado Springs is too low to allow sufficient denitrification to meet the discharge limit for pH. To reduce the reliance on adding caustic to the effluent to raise the effluent pH, Colorado Springs Utility (CSU), began a search of local industries...

Observed engineering challenges of developing water quality monitoring networks are presented in this paper and appropriate solution approaches are proposed. Water quality monitoring stations are important tools in the area of environmental water science that are used to collect measurement values. Because of missing plug-and-play support in preval...

Aeration consumes about 60% of the total energy of a WWTP and therefore makes up for a major part of its carbon footprint. Introducing advanced process control can help plants to reduce their carbon footprint and at the same time improve effluent quality through making available unused capacity for denitrification, if the ammonia concentration is b...

Providing safe and sufficient water to the public is a major and also international challenge. To tackle this challenge and to operate our urban water infrastructure in the most efficient way, instrumentation, control and automation (ICA) is a key aspect of process operation and design. In this editorial, the ICA Specialist Group of the Internation...

Proceedings of the Water Environment Federation is an archive of papers published in the proceedings of the annual Water Environment Federation® Technical Exhibition and Conference (WEFTEC® ) and specialty conferences held since the year 2000. These proceedings are not peer reviewed. A subscription to the Proceedings of the Water Environment Feder...

This paper serves as a problem statement of the issues surrounding uncertainty in wastewater treatment modelling. The paper proposes a structure for identifying the sources of uncertainty introduced during each step of an engineering project concerned with model-based design or optimisation of a wastewater treatment system. It briefly references th...

The Good Modelling Practice Task Group (GMP-TG) of the International Water Association (IWA) is developing guidelines for the use of Activated Sludge Models (ASM). As part of this work the group created and sent out a questionnaire to current and potential activated sludge model users in 2007. The objectives of the questionnaire were (i) to better...

Although traditionally not taken into account by most of activated sludge models the production of nitrite as an intermediate of the nitrification-denitrification processes becomes of interest in some specific plant operational situations or in case of high sensitivity of the receiving ecosystems. The Activated Sludge Model No.3 (ASM3) was therefor...

A new process was developed to achieve denitrifying biological phosphorus removal in wastewaters containing high levels of nitrate and phosphate with a low level of organic matter. This could particularly be useful in recirculating systems such as aquariums or fish farms to prevent accumulation of nitrate and phosphates and to avoid regular cost ex...

As mathematical modeling of wastewater treatment plants has become more common in research and consultancy, a mismatch between education and requirements for model-related jobs has developed. There seems to be a shortage of skilled people, both in terms of quantity and in quality. In order to address this problem, this paper provides a framework to...

The application of on-line sensors for monitoring or real-time control of wastewater treatment plants remains a challenging problem. The primary cause for this is the unknown quality of the data obtained by such on-line instruments. In the presented work sensor-internal meta-data is used for self-diagnosis. It is verified whether the complete measu...

The past several years have seen a significant increase in the use of computer models to simulate wastewater treatment processes for plant design and optimization. The quality and level of detail of these models vary widely, depending on their purpose, availability of resources and the skill level of the modeler. Modelers use different approaches a...