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Investigate population changes and build a history of cause and effect for your plant.
Vorticella provide a valuable service in two ways. Firstly, they help “clean up” any non-flocculated bacteria, preventing them from staying in suspension causing cloudy effluent after clarification. Secondly, their comparative population numbers can give the operator valuable insight into prevailing conditions in their system.
A big increase in Vorticella may indicate that the floc is getting too hungry (not enough EPS (extra cellular polymeric substances) to glue the floc together), or that a toxic shock has hit the plant resulting in deflocculation with an increase in free bacteria, or that the sludge age is getting a little too high and the flocs are pin floccing. A big increase in Vorticella, particularly if accompanied by an increase in Rotifers (also filter feeders) should make you suspicious and investigate.
Vorticella reproduce by growing a new daughter head out of the side of the parent head. It starts off looking like a large pimple and develops into a head nearly the size of the original. Once mature, it detaches and swims off in a form we call a telotroch, until it finds somewhere suitable to establish itself and grow its own new stalk. In the picture below at 1000X magnification (1 scale division = 1 µm) you can see the mature telotroch on the left of the parent head, nearly ready to detach and establish independently.
Check that out in one of Liz’s microscope videos (this one is narrated) below:
Vorticella can be identified by the fact they grow as a single colony (single head), unless they are reproducing. You can see the muscle fibre inside the stalk allowing the Vorticella to move it’s head away from trouble!
You can see these in the 400x magnification side view:
And back view:
I scale division = 2.5 µm.
Aspidisca are a crawling ciliate who use their clusters of hardened cilia, called cirri, to crawl over the surface of flocs, swimming and to brush bacteria (their food) off the surfaces they are travelling over.
You will see they have a little beak-like mouth that they stuff bacteria into! Aspidisca in decent numbers are a very positive sign in an activated sludge sample for two reasons.
Firstly, the presence of Aspidisca indicates that the surfaces of the flocs (aggregated bacterial biomass) are getting a good “hoovering”, exposing healthy, viable bacteria to consume the surrounding nutrients. Secondly, in my experience, when I see lots of healthy Aspidisca, the plant is usually nitrifying really well (excellent biological oxidation of ammonia).
Want to see some “live” action from Aspidisca? You’ll find a video below from Liz’s “Bug Lady” days in New Zealand.
A sudden appearance or increase in of spirochetes or Spirillum in your mixed liquor may be an indication of:
Spirillum are defined as micro-aerophiles, which means they are favoured by low dissolved oxygen but must have some dissolved oxygen present to survive (typically 1 – 9 % DO preferred). They cannot survive without a little free oxygen (and cannot denitrify nitrate).
Spirochetes may be strictly anaerobic (conditions with no oxygen of any kind available) or facultatively anaerobic. They really like septic conditions.
Our experience has been as the population transitions from Spirillum to spirochetes, the DO is getting lower, the spirochetes are liking completely anaerobic conditions which the spirillum cannot handle. This makes it quite good if you are trying to get on top of an aeration issue, because if you can see the spirochete population being replaced by Spirillum, you know things are going back up in the right direction.