Scientific and Technical Report Series – serie

Scientific and Technical Report No. 21 Uncertainty in Wastewater Treatment Design and Operation aims to facilitate the transition of the wastewater profession to the probabilistic use of simulators with the associated benefits of being better able to take advantage of opportunities and manage risk. There is a paradigm shift taking place in the design and operation of treatment plants in the water industry. The market is currently in transition to use modelling and simulation while still using conventional heuristic guidelines (safety factors). Key reasons for transition include: wastewater treatment simulation software advancements; stricter effluent requirements that cannot be designed for using traditional approaches, and increased pressure for more efficient designs (including energy efficiency, green house gas emission control). There is increasing consensus among wastewater professionals that the performance of plants and the predictive power of their models (degree of uncertainty) is a critical component of plant design and operation. However, models and simulators used by designers and operators do not incorporate methods for the evaluation of uncertainty associated with each design. Thus, engineers often combine safety factors with simulation results in an arbitrary way based on designer ‘experience’. Furthermore, there is not an accepted methodology (outside modelling) that translates uncertainty to assumed opportunity or risk and how it is distributed among consultants/contractors and owners. Uncertainty in Wastewater Treatment Design and Operation documents how uncertainty, opportunity and risk are currently handled in the wastewater treatment practice by consultants, utilities and regulators. The book provides a useful set of terms and definitions relating to uncertainty and promotes an understanding of the issues and terms involved. It identifies the sources of uncertainty in different project phases and presents a critical review of the available methods. Real-world examples are selected to illustrate where and when sources of uncertainty are introduced and how models are implemented and used in design projects and in operational optimisation. Uncertainty in Wastewater Treatment Design and Operation defines the developments required to provide improved procedures and tools to implement uncertainty and risk evaluations in projects. It is a vital reference for utilities, regulators, consultants, and trained management dealing with certainty, opportunity and risk in wastewater treatment.

Scientific and Technical Report No. 24Performance-Based Contracts (PBC) for Improving Utilities Efficiency: Experiences and Perspectives is a compendium of articles written by members of the PBC taskforce. It focuses on new approaches without delegated management to private operator i.e. service contracts, consulting contracts, Alliance approach, public-public partnership. It also mentions new design and generation of more traditional PPPs, (MC, lease, concession), where a larger proportion of performance-based design is being applied.List of Contents:Performance Based Contracts – Setting the scene; PBC and Results Based Financing: the inverse approach; PBC and Energy Efficiency; Internal Performance Contracts: A Case of the National Water and Sewerage Corporation in Uganda; Performance-Based Service Contracts in Navi Mumbai; Financial Comparison of PBCs and Conventional Approach; Tegucigalpa PBC Case Study; Performance Based Contracts – Key Design Issues; NRW Reduction Optimization Framework; How to improve water services performance? Performance Based Contracts (PBC) and Regulatory issues; Peer-to-Peer Partnerships Operational for sustainable water services; Performance Based Contracts in Malawi: Teamwork Works; Performance based affermage contracts; Performance based Contracts, The Aroona Integrated Alliance Experience; Experience from Eastern Europe; NRW Performance Contract – Kingdom of Bahrain; The way forward and perspectives/trends

This Scientific and Technical Report (STR) provides in-depth fundamentals and guidelines regarding Computational Fluid Dynamics (CFD) simulations of Water Resources Recovery Facilities (WRRFs) unit processes (e.g. headworks, aerobic and anaerobic biological reactors, settling tanks, disinfection).Each unit process is described with respect to:Literature review and process descriptionRelevant CFD concepts and modelling approachCase studiesFuture research needsCFD Modelling for Wastewater Treatment Processes also opens the discussion on two fundamental topics: experimental validation of CFD simulations, and the complementarity between CFD and Chemical Reaction Engineering approaches. This book is intended for undergraduate and graduate students majoring in fields related to wastewater treatment and/or fluid mechanics, as well as researchers and engineers who conduct research and practices in modelling such unit processes. Water resource recovery modelling is not just about lab-scale processes. Now and in the future, it is about improving our understanding of (and designing better) full-scale facilities!

This book describes theory and approach for a comprehensive and applied physicochemical model for wastewater treatment. These are reactions which occur without a biological mediator, and are critical to both the biology of wastewater treatment, and stand-alone chemical treatment units. The book includes description of acid-base theory, solution ion pairing and non-ideality, participation with other phases, and chemical oxidation/reduction. Full implementation details are provided, including in a plant wide modelling context, and with respect to required extensions to biological models to describe more complex aspects of the iron-sulfur-phosphorous system, which requires all components of the model to be properly described.

Water quality standards across the world are being re-written to promote healthier ecosystems, ensure safe potable water sources, increased biodiversity, and enhanced ecological functions. Treatment wetlands are used for treating a variety of pollutant waters, including municipal wastewater, agricultural and urban runoff, industrial effluents, and combined sewer overflows, among others. Treatment wetlands are particularly well-suited for sustainable water management because they can cope with variable influent loads, can be constructed of local materials, have low operations and maintenance requirements compared to other treatment technologies, and they can provide additional ecosystem services. The technology has been successfully implemented in both developed and developing countries.The first IWA Scientific and Technical Report (STR) on Wetland Technology was published in 2000. With the exponential development of the technology since then, the generation of a new STR was facilitated by the IWA Task Group on Mainstreaming Wetland Technology. This STR was conceptualized and written by leading experts in the field. The new report presents the latest technology applications within an innovative planning framework of multi-purpose wetland design. It also includes practical design information collected from over twenty years of experience from practitioners and academics, covering experiments at laboratory and pilot-scale up to full-scale applications.Scientific and Technical Report No.27

With increased commitment from the international community to reduce greenhouse gas (GHG) emissions from all sectors in accordance with the Paris Agreement, the water sector has never felt the pressure it is now under to transition to a low-carbon water management model. This requires reducing GHG emissions from grid-energy consumption (Scope 2 emissions), which is straightforward; however, it also requires reducing Scope 1 emissions, which include nitrous oxide and methane emissions, predominantly from wastewater handling and treatment. The pathways and factors leading to biological nitrous oxide and methane formation and emissions from wastewater are highly complex and site-specific. Good emission factors for estimating the Scope 1 emissions are lacking, water utilities have little experience in directly measuring these emissions, and the mathematical modelling of these emissions is challenging. Therefore, this book aims to help the water sector address the Scope 1 emissions by breaking down their pathways and influencing factors, and providing guidance on both the use of emission factors, and performing direct measurements of nitrous oxide and methane emissions from sewers and wastewater treatment plants. The book also dives into the mathematical modelling for predicting these emissions and provides guidance on the use of different mathematical models based upon your conditions, as well as an introduction to alternative modelling methods, including metabolic, data-driven, and AI methods. Finally, the book includes guidance on using the modelling tools for assessing different operating strategies and identifying promising mitigation actions. A must have book for anyone needing to understand, account for, and reduce water utility Scope 1 emissions.

The influence of landscapes – topography, soil, vegetation, geology - on water quality is an inherent part of the global water cycle. Land use has adverse impacts for example when soils are exposed, significant quantities of pollutants are released (including anthropogenic materials added to those naturally present), or pollutants are added directly to the water environment. Those impacts range from industrial development to farming and urbanisation. Whilst inefficient polluting industrial effluents are still tolerated in some countries, and poorly treated sewage globally remains a huge challenge for sanitation and public health, as well as the water environment, diffuse pollution is relatively poorly recognised or understood. The operator of a sewage or trade effluent treatment plant is consciously discharging effluent to the local river. But a farmer is simply growing crops or farming livestock, a city commuter driving to work is unlikely to be thinking how brake pad wear has released copper to the water (and air) environment and hydrocarbons and particulates too; no one is intending to cause pollution of the water environment. The same applies to industrial chemists creating fire-proofing chemicals, solvents, fertilisers, pesticides, cosmetics and many more substances which contaminate the environment. Understanding and ultimately minimising diffuse pollution is in that sense the science of unintended consequences. And the consequences can be severe, for water resources and ecosystems. It’s a global problem.This book comprises 18 papers from experts around the globe, presenting evidence from tropical as well as temperate regions, and rural as well as urban land use challenges. The book explores the nature of diffuse pollution and exemplifies the issues at various scales, from high-level national overviews to particular catchment and pollutant issues.By contrast, natural or semi-natural forest cover has long been recognised as safeguarding water quality in reservoirs (examples from Australia to Thailand and UK). The final chapter looks at how landscapes generally, can be designed to minimise pollution risks from particular land-uses, arguing for a more widespread catchment approach to water-aware landscape design, allied with flood risk resilience, place-making for people, and biodiversity opportunities too.

This Scientific Technical Report demonstrates meta-data strategies for water resource recovery facilities (WRRF), including the essential data validation with machine learning and traditional methods. The report is the result of extensive work from many water data experts and a utility focus group, with the dedicated application of WRRF data.Emerging trends in artificial intelligence and machine learning project unforeseen possibilities in managing our WRRF’s. Hope is built upon the large data volumes collected with high frequency from both existing sensors, as well as new uncoordinated data sources outside the fence. The data variety however makes it challenging to reuse data, especially when the purpose changes. Without a proper data description (meta-data), modelling and autonomous digitalization will be difficult, and likely remain a vision. Likewise, quantified data quality are key meta-data to decide when data are fit-for-purpose.The report aims to fill the gap of how meta-data can be used in practice to leverage the value of data in a WRRF context. The report describes existing methods and systematic methodologies to collect and reconcile meta-data describing signal generation, signal quality, and contextual meta-data. The sometimes ambiguous data terminology is clarified with real WRRF examples to endorse adoption in practice. Guidelines for data quality assessment is a central part and cover both standard sensor validation protocols, as well as a separate chapter on data analytical techniques. The latter serves as a smorgasbord with mechanistic and data-driven algorithms for online sensor quality assessment.The report is intended as a reference guide for the practitioner who aims at future proofing, but also maximizing, the current use of today’s recorded WRRF data. The content bridges theory with current practices and provides a base tool for the WRRF data practitioner.

Research into the sampling and measurement of odours has developed in a number of sectors, especially the agriculture, food and process industries, with knowledge from each sector being transferred to the wastewater and solid waste management sectors. Progressive developments in odour research have resulted in researchers re-tracing original research studies to understand the contribution and variability of differing sampling and measurement techniques. There are, however, very few reviews that compile earlier studies across each sector. This study looks at the information used to support current practices in odour sampling and measurement for impact reduction. Sampling for Measurement of Odours reviews European and other internationally available research studies to understand odour sampling and measurement practice in waste applications. The emphasis is placed on appropriate odour sampling and its relationship to differing measurement techniques. As recent developments in standardisation of odour measurement have reduced much of the variation and identified best practice in this area there is, at present, a far greater variation in sampling techniques with serious implications for the quality of samples obtained and their usefulness for assessing odour impact. The review considers the available information on uncontrolled area sources, identifies factors influencing sample losses or transformations and looks at information on the sources of variability identified through standardisation programmes. This need for this report was identified by the Odour Network, an EPSRC-sponsored discussion platform intended to promote multidisciplinary research in the areas of odour measurement, modelling and treatment.    Scientific and Technical Report No.17

The sequencing batch reactor (SBR) is perhaps the most promising and viable of the proposed activated sludge modifications today for the removal of organic carbon and nutrients. In a relatively short period, it has become increasingly popular for the treatment of domestic and industrial wastewaters, as an effective biological treatment system due to its simplicity and flexibility of operation. Mechanism and Design of Sequencing Batch Reactors for Nutrient Removal has been prepared with the main objective to provide a unified design approach for SBR systems, primarily based on relevant process stoichiometry. Specific emphasis has been placed upon the fact that such a unified design approach is also by nature the determining factor for the selection of the most appropriate cyclic operation scheme, the sequence of necessary phases and filling patterns for the particular application. The proposed basis for design is developed and presented in a stepwise approach to cover both organic carbon and nutrient removal, domestic and industrial wastewaters, strong and specific wastes. The merits of model simulation as an integral complement of process design, along with performance evaluation of SBR models are also emphasized.    Scientific and Technical Report No. 19

Over 90% of bacterial biomass exists in the form of biofilms. The ability of bacteria to attach to surfaces and to form biofilms often is an important competitive advantage for them over bacteria growing in suspension. Some biofilms are "good" in natural and engineered systems; they are responsible for nutrient cycling in nature and are used to purify waters in engineering processes. Other biofilms are "bad" when they cause fouling and infections of humans and plants. Whether we want to promote good biofilms or eliminate bad biofilms, we need to understand how they work and what works to control them. Mathematical Modeling of Biofilms provides guidelines for the selection and use of mathematical models of biofilms. The whole range of existing models - from simple analytical expressions to complex numerical models - is covered. The application of the models for the solution of typical problems is demonstrated, and the performance of the models is tested in comparative studies. With the dramatic evolution of the computational capacity still going on, modeling tools for research and practice will become more and more significant in the next few years. This report provides the foundation to understand the models and to select the most appropriate one for a given use. Mathematical Modeling of Biofilms gives a state-of-the-art overview that is especially valuable for educating students, new biofilm researchers, and design engineers. Through a series of three benchmark problems, the report demonstrates how to use the different models and indicates when simple or highly complex models are most appropriate. This is the first report to give a quantitative comparison of existing biofilm models.               The report supports model-based design of biofilm reactors.               The report can be used as basis for teaching biofilm-system modeling.               The report provides the foundation for researchers seeking to use biofilm modeling or to develop new biofilm models.   Scientific and Technical Report No.18

Water Reuse: An International Survey of current practice, issues and needs examines water reuse practices around the world from different perspectives. The objective is to show how differently wastewater reuse is conceived and practised around the world as well as to present the varied needs and possibilities for reusing wastewater.  In the first section water reuse practices around the world are described for regions having common water availability, reuse needs and social aspects. The second section refers to the “stakeholders” point of view. Each reuse purpose demands different water quality, not only to protect health and the environment but also to fulfil the requirements of the specific reuse. Reuses considered are agricultural, urban agriculture as a special case of the former, municipal and industrial. Alongside these uses, the indirect reuse for human consumption through aquifer recharge is also discussed. The third section deals with emerging and controversial topics. Ethical and economical dilemmas in the field are presented as a subject not frequently addressed in this field. The role of governments in respect of public policy in reuse is discussed as well as the different international criteria and standards for reusing wastewater. The importance of public acceptance and the way to properly handle it is also considered. The fourth section of the book presents contrasting case studies; typical situations in the developed world (Japan and Germany) are compared to those in developing countries (Pakistan and Brazil) for agricultural and industrial reuse. Indirect planned reuse for human consumption (Germany) is compared with an unplanned one (Mexico). The Windhoek, Namibia case study is presented to emphasize why if the direct reuse of wastewater for human consumption has been performed with success for more than 35 years it is still the only example of this type around the world. To illustrate the difficulties of having a common framework for regulating water reuse in several countries, the Mediterranean situation is described. Other case studies presented refer to the reuse situation in Israel, Spain, Cameroon, Nepal and Vietnam, these latter countries being located in water rich areas. This book will be an invaluable information source for all those concerned with water reuse including water utility managers, wastewater policy makers and water resources planners as well as researchers and students in environmental engineering, water resources planning and sanitary engineering.   Scientific and Technical Report No. 20

Wastewater treatment plants are large non-linear systems subject to large perturbations in wastewater flow rate, load and composition. Nevertheless these plants have to be operated continuously, meeting stricter and stricter regulations. Many control strategies have been proposed in the literature for improved and more efficient operation of wastewater treatment plants. Unfortunately, their evaluation and comparison – either practical or based on simulation – is difficult. This is partly due to the variability of the influent, to the complexity of the biological and biochemical phenomena and to the large range of time constants (from a few minutes to several days). The lack of standard evaluation criteria is also a tremendous disadvantage. To really enhance the acceptance of innovative control strategies, such an evaluation needs to be based on a rigorous methodology including a simulation model, plant layout, controllers, sensors, performance criteria and test procedures, i.e. a complete benchmarking protocol. This book is a Scientific and Technical Report produced by the IWA Task Group on Benchmarking of Control Strategies for Wastewater Treatment Plants. The goal of the Task Group includes developing models and simulation tools that encompass the most typical unit processes within a wastewater treatment system (primary treatment, activated sludge, sludge treatment, etc.), as well as tools that will enable the evaluation of long-term control strategies and monitoring tasks (i.e. automatic detection of sensor and process faults). Work on these extensions has been carried out by the Task Group during the past five years, and the main results are summarized in Benchmarking of Control Strategies for Wastewater Treatment Plants. Besides a description of the final version of the already well-known Benchmark Simulation Model no. 1 (BSM1), the book includes the Benchmark Simulation Model no. 1 Long-Term (BSM1_LT) – with focus on benchmarking of process monitoring tasks – and the plant-wide Benchmark Simulation Model no. 2 (BSM2). Authors: Krist V. Gernaey, Technical University of Denmark, Lyngby, Denmark, Ulf Jeppsson, Lund University, Sweden, Peter A. Vanrolleghem, Université Laval,  Quebec, Canada and John B. Copp, Primodal Inc., Hamilton, Ontario, Canada

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 carrying out a simulation study to produce the desired accuracy. Inconsistent approaches and insufficient documentation make quality assessment and comparison of simulation results difficult or almost impossible. A general framework for the application of activated sludge models is needed in order to overcome these obstacles. The genesis of the Good Modelling Practice (GMP) Task Group lies in a workshop held at the 4th IWA World Water Congress in Marrakech, Morocco where members of research groups active in wastewater treatment modelling came together to develop plans to synthesize the best practices of modellers from all over the world. The most cited protocols were included in the work, amongst others from: HSG (Hochschulgruppe), STOWA, BIOMATH and WERF. The goal of the group is to set up an internationally accepted framework to deal with the ASM type models in practice. This framework shall make modelling more straightforward and systematic to use especially for practitioners and consultants. Additionally, it shall help to define quality levels for simulation results, a procedure to assess this quality and to assist in the proper use of the models. The framework will describe a methodology for goal-oriented application of activated sludge models demonstrated by means of a concise guideline about the procedure of a simulation study and some illustrative case studies. The case studies shall give examples for the required data quality and quantity and the effort for calibration/validation with respect to a defined goal. The final report will include an extended appendix with additional information and details of methodologies. Additional features in Guidelines for Using Activated Sludge Models include a chapter on modelling industrial wastewater, an overview on the history, current practice and future of activated sludge modelling and several explanatory case studies. It can be used as an introductory book to learn about Good Modelling Practice (GMP) in activated sludge modelling and will be of special interest for process engineers who have no prior knowledge of modelling or for lecturers who need a textbook for their students. The STR can also be used as a modelling reference book and includes an extended appendix with additional information and details of methodologies.Scientific and Technical Report No. 22

Although developments in wastewater treatment over recent decades have focused on the biological reactor, the secondary settling tank (SST) also plays a major role in achieving increasingly stringent effluent quality standards.  This report collates many of the significant developments that have taken place in SST theory, design, modelling and operation. Earlier SSTs were designed only by empirical hydraulic criteria such as overflow rate, which do not recognize sludge concentration and settleability. Today, there are available not only much improved design procedures but also hydrodynamic models for simulating water and solids distribution and flows in full-scale SSTs.  Nine chapters cover a wide range of subjects including:  Flocculation and settling behaviour of biological sludges             SST performance evaluation protocols           Development and evaluation of the different design procedures such as the flux theory and the ATV design rules            Developments in and application of one- two- and three-dimensional modelling             Experience-based aspects of design and operation of circular, rectangular and vertical SSTs.  Reprinted for 2006   Scientific and Technical Report No.6

The book presents a comprehensive up-to-date survey of wetland design techniques and operational experience from treatment wetlands.  This book is the first and only global synthesis of information related to constructed treatment wetlands. Types of constructed wetlands, major design parameters, role of vegetation, hydraulic patterns, loadings, treatment efficiency, construction, operation and maintenance costs are discussed in depth. History of the use of constructed wetlands and case studies from various parts of the world are included as well.  Constructed Wetlands for Pollution Control will be indispensable for wastewater treatment researchers and designers, decision makers in public authorities, wetland engineers, environmentalists and landscape ecologists.  Contents Biological methods for the treatment of wastewaters                   Types of constructed wetland                   Aplications of the technology                    Framework for interpreting and predicting water quality improvement                    Mechanisms and results for water quality improvement                   Design                    Plants and planting                    System start-up                    Economics                    Case studies   Scientific and Technical Report No.8

This book has been produced to give a total overview of the Activated Sludge Model (ASM) family at the start of 2000 and to give the reader easy access to the different models in their original versions. It thus presents ASM1, ASM2, ASM2d and ASM3 together for the first time. Modelling of activated sludge processes has become a common part of the design and operation of wastewater treatment plants. Today models are being used in design, control, teaching and research. Contents ASM3: Introduction, Comparison of ASM1 and ASM3, ASM3: Definition of compounds in the model, ASM3: Definition of processes in the Model, ASM3: Stoichiometry, ASM3: Kinetics, Limitations of ASM3, Aspects of application of ASM3, ASM3C: A Carbon based model, Conclusion                        ASM 2d: Introduction, Conceptual Approach, ASM 2d, Typical Wastewater Characteristics and Kinetic and Stoichiometric Constants, Limitations, Conclusion                       ASM 2: Introduction, ASM 2, Typical Wastewater Characteristics and Kinetic and Stoichiometric Constants, Wastewater Characterization for Activated Sludge Processes, Calibration of the ASM 2, Model Limitations, Conclusion, Bibliography                       ASM 1: Introduction, Method of Model Presentation, Model Incorporating Carbon Oxidation Nitrification and Denitrification, Characterization of Wastewater and Estimation of Parameter Values, Typical Parameter Ranges, Default Values, and Effects of Environmental Factors, Assumptions, Restrictions and Constraints, Implementation of the Activated Sludge Model   Scientific and Technical Report No.9

The IWA Task Group for Mathematical Modelling of Anaerobic Digestion Processes was created with the aim to produce a generic model and common platform for dynamic simulations of a variety of anaerobic processes.  This book presents the outcome of this undertaking and is the result of four years collaborative work by a number of international experts from various fields of anaerobic process technology. The purpose of this approach is to provide a unified basis for anaerobic digestion modelling. It is hoped this will promote increased application of modelling and simulation as a tool for research, design, operation and optimisation of anaerobic processes worldwide. This model was developed on the basis of the extensive but often disparate work in modelling and simulation of anaerobic digestion systems over the last twenty years. In developing ADM1, the Task Group have tried to establish common nomenclature, units and model structure, consistent with existing anaerobic modelling literature and the popular activated sludge models (See Activated Sludge Models ASM1, ASM2, ASM2d and ASM3, IWA Publishing, 2000, ISBN: 1900222248). As such, it is intended to promote widespread application of simulation from domestic (wastewater and sludge) treatment systems to specialised industrial applications. Outputs from the model include common process variables such gas flow and composition, pH, separate organic acids, and ammonium. The structure has been devised to encourage specific extensions or modifications where required, but still maintain a common platform. During development the model has been successfully tested on a range of systems from full-scale waste sludge digestion to laboratory-scale thermophilic high-rate UASB reactors. The model structure is presented in a readily applicable matrix format for implementation in many available differential equation solvers. It is expected that the model will be available as part of commercial wastewater simulation packages. ADM1 will be a valuable information source for practising engineers working in water treatment (both domestic and industrial) as well as academic researchers and students in Environmental Engineering and Science, Civil and Sanitary Engineering, Biotechnology, and Chemical and Process Engineering departments. Contents Introduction             Nomenclature, State Variables and Expressions             Biochemical Processes             Physicochemical Processes             Model Implementation in a Single Stage CSTR             Suggested Biochemical Parameter Values, Sensitivity and Estimation             Conclusions             References             Appendix A: Review of Parameters             Appendix B: Supplementary Matrix Information             Appendix C: Integration with the ASM              Appendix D: Estimating Stoichiometric Coefficients for Fermentation   Scientific & Technical Report No.13

Instrumentation, control and automation (ICA) in wastewater treatment systems is now an established and recognised area of technology in the profession. There are obvious incentives for ICA, not the least from an economic point of view. Plants are also becoming increasingly complex which necessitates automation and control. Instrumentation, Control and Automation in Wastewater Systems summarizes the state-of-the-art of ICA and its application in wastewater treatment systems and focuses on how leading-edge technology is used for better operation. The book is written for: The practising process engineer and the operator, who wishes to get an updated picture of what is possible to implement in terms of ICA;      The process designer, who needs to consider the couplings between design and operation;      The researcher or the student, who wishes to get the latest technological overview of an increasingly complex field. There is a clear aim to present a practical ICA approach, based on a technical and economic platform. The economic benefit of different control and operation possibilities is quantified. The more qualitative benefits, such as better process understanding and more challenging work for the operator are also described. Several full-scale experiences of how ICA has improved economy, ease of operation and robustness of plant operation are presented. The book emphasizes both unit process control and plant wide operation.   Scientific & Technical Report No. 15

The Activated Sludge (AS) Process is old technology but is still widely adopted worldwide for its convenience and simplicity: an impressive number (many hundred of thousands) of this kind of system are in operation. Occasionally, problems such as bulking and foaming occur, causing regulation violations and large investment is often required immediately to control them. For this reason, an intense research effort has been made during the last few decades to face these problems, and this report details the work undertaken by the IWA Specialist Group on Activated Sludge Population Dynamics. This Scientific and Technical Report  describes the main reasons fslyuor the growth of the different filamentous microorganisms in activated sludge, and the biological molecular tools available today for the identification of the main biomass components. The wide range of experiences around the world is documented and the methods to avoid the proliferation of these organisms are presented and critically reviewed. Activated Sludge Separation Problems consists of seven chapters, presenting up-to-date technical and scientific aspects of these processes.   Scientific and Technical Report No. 16