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Online course

9. Aeration and Mixing

This motivating course covers various aspects of aeration and mixing in activated sludge wastewater treatment. Aeration fundamentals and technology aspects include oxygen transfer in clean and process water, and mysterious alpha factor, fine and coarse bubbles and droplets, bubble and mechanical aeration, centrifugal and high purity oxygen air blowers. You will also learn about factors (sludge retention time, role of selectors, airflow rate, diffuser density, fouling scaling and cleaning, reactor depth, mixed-liquor concentration, temperature and pressure, impact of hydrodynamic, daily dynamic and alpha factor) affecting oxygen transfer. Design algorithms, aeration and energy and sustainable aeration practices are also part of this practical curriculum. Many examples and exercises complement the course as well as case studies and most common experimental methods. By the end of the course you will gain new insights about aeration and mixing.

Welcome by Prof. Diego Rosso

Course information

  • Learning Objectives

    After completion of the course you should be able to:

    • Learn to quantify aeration performance according to standard formulas
    • Understand the dynamics of aeration systems
    • Learn the basics of modeling aeration performance
    • Understand the details of aeration testing protocols
    • Acquire the ability to perform a preliminary design of a diffuser system
    • Acquire the ability to quantify mixing intensity in an aeration tank
  • Syllabus

    This course covers the following topics:

    • Aeration Fundamentals
    • Aeration Dynamics
    • Aeration Energy
    • Aeration Testing
    • Aeration Diagnostics
    • Sustainable Aeration Practice
    • Aeration Modelling
    • Aeration Design
    • Mixing Fundamentals
    • Mixing Design
  • Organization

    Courses in this series consist of video lectures, presentation slides, reading materials, exercises, and assignments with solutions. In principle, each video presentation has its complementary presentation slides. All videos are available for viewing in the section “Video-recorded presentations”. The materials are packaged in three (.zip) files, namely, the “Videos”, the “Presentations”, and the “Documents”. Files may be of considerable size, so you need to ensure that your computer has sufficient bandwidth and capacity for downloading. This course is based on the chapter in the book “Biological Wastewater Treatment: Principles, Modeling, and Design” 2nd edition (Chen et al., 2020). To check and expand your knowledge on the subject, it is recommended to study the corresponding chapter in the complementary book  “Biological Wastewater Treatment: Examples and Exercises” (Lopez-Vazquez et al., 2023). The two chapters are open-access and available in the section “Documents (.zip) on this webpage.

  • Delivery Method

    This course is currently designed for a SELF-STUDY mode. It is FREE and does not include guidance, support, exams, assessment, and certification. It is possible that shortly, the series (or its parts) will be adopted by institutions who may deliver the guided version, including certification. As soon as this is the case, it will be advertised on this website.

  • Open Access

    The content is available for free unlimited access and use, consistent with Global Sanitation Graduate School’s commitment to ensuring open access to information and knowledge. Please note that the video materials fall under the Attribution 4.0 International (CC BY 4.0) license (, presentations under the Attribution 4.0 International (CC BY 4.0) license  (, readers (OA books of IWA Publishing) under the Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0) license (, and other readers under the license specified by the publisher. Although care has been taken to ensure the integrity and quality of these materials and information, no responsibility is assumed by the author(s), Global Sanitation Graduate School, or IHE Delft Institute for Water Education for any damage to property or persons as a result of the use of these materials and/or the information contained herein.

Video-recorded presentations

Here you can watch all video-recorded lectures in this course.

9.1 Aeration Fundamentals

Diego Rosso



1 of 10

9.2 Aeration Dynamics

Diego Rosso


2 of 10

9.3 Aeration Energy

Diego Rosso


3 of 10

9.4 Aeration Testing

Michael K. Stenstrom



4 of 10

9.5 Aeration Diagnostics

Diego Rosso


5 of 10

9.6 Sustainable Aeration Practice

Diego Rosso


6 of 10

9.7 Aeration Modelling

Manel Garrido-Baserba


7 of 10

9.8 Aeration Design

Eveline I.P. Volcke


8 of 10

9.10 Mixing Fundamentals

Diego Rosso ▪ Coenraad Pretorius


9 of 10

9.11 Mixing Design

Coenraad Pretorius


10 of 10

Download course materials

In this section, you can download all video-recorded lectures, presentations, and other documents that make up this course.

  • 9 │ Videos (.zip)
    Diego Rosso ● Michael K. Stenstrom ● Manel Garrido-Baserba ● Coenraad Pretorius
    (0.0 MB)
  • 9 │ Presentations (.zip)
    Diego Rosso ● Michael K. Stenstrom ● Manel Garrido-Baserba ● Coenraad Pretorius
    (0.0 MB)
  • 9 │ Documents (.zip)
    Diego Rosso ● Michael K. Stenstrom
    (0.0 MB)


Prof. Damir Brdjanovic, PhD

Course resource person | IHE Delft Institute for Water Education