Tuesday, February 05, 2013

Bacteria in a wastewater treatment plant

Bacteria in activated sludge from a wastewater treatment plant

It is a remarkable fact that we fully depend on microbes to treat or sewage water. In every wastewater treatment plant, from the simplest to the most modern ones, the essential activity is biological and is mainly carried out by bacteria. In modern plants, sewage water is directed to large aerated tanks in which the pollution is consumed by a mixture of microbes and organic matter known as  activated sludge.

The video below shows how an aerated tank looks like. You don’t want to take a swim in there… 

For a microbiologist, a wastewater treatment plant is a delight: I’ve never seen another environment with as much diversity in the size and shapes of cells. It is a true microbial jungle containing countless bacteria and many protozoans that feed on them.

Here's some of the bacterial morphologies that one can encounter in a wastewater treatment plant. Note that the scale is not the same in the different images.

These are from the aerated tank:

These filamentous bacteria come from a special digester for grease and oil:

Now it's interesting to realize that although the total number of bacterial species is tremendous, the number of different morphologies is far less impressive. To put it simply, most of the bacteria are either cocci (spherical), rods (straight or curved), corkscrew-shaped, appendaged, or filamentous. (Most of these are represented in the pictures above.)

For this reason, microbiologists do not generally rely on the cell shape and size to determine the identity of a bacterial species. A bacterium's metabolism can give a lot of clues (is it aerobic or anaerobic?, what carbon source can it use? , etc.), but it requires the isolation of the unknown species in a pure culture. Another tool of choice is to use the nucleic acids content, either through DNA sequencing or through the use of  fluorescent probes that target the ribosomal RNA (fluorescent in situ hybridization).

Here's an example with bacteria from the aerated tank. The first picture is a phase contrast image (normal light). The picture below shows the fluorescence emitted by a probe specific to the group betaproteobacteria. We can see that most cells (but not all!) are labelled with the probe, which gives us an indication about the composition of the bacterial community (in this case many betaproteos).

Here's another example with bacteria from the sludge digester, an anaerobic tank where the excess of activated sludge is pumped in order to be further 'digested'. This time we used a probe for the domain Archaea. Most likely these long rod cells are methanogens that help ferment the sludge into methane!

All micrographs were taken during my PhD at the University of Lausanne. At that time I was assisting in a practical course on bacterial community analysis.


  1. This comment has been removed by a blog administrator.

  2. This comment has been removed by a blog administrator.

  3. This comment has been removed by a blog administrator.

  4. This comment has been removed by a blog administrator.

  5. This comment has been removed by a blog administrator.

  6. In the typical wastewater treatment process, the goal of primary, secondary and tertiary effluent treatment is to reduce or remove organic matter, solids, nutrients, disease-causing organisms and other pollutants from the treated wastewater before it is discharged to a body of water.
    Domestic Biogas Plant in Bangalore

    Biogas Plant in Kerala

  7. This comment has been removed by a blog administrator.

  8. Hi, I love your informative blog. Water quality studies commonly find that between 20% to 40% of wells in any given area are contaminated with E.coli or coliform bacteria! Unfortunately, most people don’t know this so they don’t take precautions. Even then, the typical response is to simply pour chlorine bleach into their well. Good day!~ Pamela Anderson

  9. Well-written post that shares almost everything we need to know about wastewater treatment plant. Today, sewage water treatment and wastewater treatment plants have played integral roles in waste management and water treatment industry. Some water treatment systems like sewage treatment plants (STP), effluent treatment plants (ETP) and Industrial waste water treatment plants are used for treating waste water. Great to read this stuff.

  10. This comment has been removed by a blog administrator.

  11. What a useful blog and great shared to wastewater treatment plant !!!!
    panel tanks Australia

  12. Great share! This is so useful. Thanks for posting this wastewater treatment process. Keep blogging!

  13. Thanks for sharing this useful information. Effluent Treatment Plant is another method for waster water treatment. To know about this click here.

  14. What a great blog, i am searching in google from couple of days” but did not find any great way, but my search came to an end after visiting your blog.!!!Do you have any more related blogs or ideas related to like your this blog, it will help me in my further research work…Will keep following your blogs…

    industrial water purification treatment plant || water purifier for home || home water purifier

  15. Thanks for sharing this nice blog with us; I get very fruitful information here. Get the best industries sewage treatment plants company...

  16. In the picture with shining cocos and other bacteria, do you know what the specie the cocos is? I have a contamination problem in my laboratory with this cocos. thanks.

    1. Hi Sergio,

      Unfortunately with such staining techniques we cannot get information on what species are present, only to which group they belong. We would have to sequence their DNA to get a clearer picture.

  17. thanks for sharing nice information about waste water treatment.. keep writing

    Anne Cole
    Waste Water Services

  18. I think this is one of the most important information for me.
    And i'm glad reading your article. But want to remark on some general things, The website style is perfect, the articles is really nice : D. Good job, cheers

    Waste water treatment plant
    erection & commissioning

  19. Great detailed information, I ll be visiting you more frequently, here is very interesting information.

    Ozone Waste Water Treatment & Ozone Generators

  20. They have every kind of water treatment plants suiting your needs and requirements. The services are very good and related people are very easy to talk to for any further assistance. They provide quality tanks with great customer care services. Very impressed by their services and product quality.

  21. Which often australian writing service or even went through or maybe viewed on the net? When i consult mainly because When i importance ones well informed judgment in addition to learn the item can be purchased in practical as soon as buying a ca article author, as different threads include served everyone uncover trusted internet writers in past times.

  22. This is fabulous.Great post!Thank you for sharing.Keep it up!!!http://goo.gl/cY7cFs

  23. Hi,

    Good Content and information for new Digital India,

    Ion India Limited is also a Public Sector Company, offers conventional to highly technology oriented water treatment solutions for the industrial and municipal markets plant.