So I have this Large Water Jug that I fill only water with. And this is the 2nd time there has been a layer of green film that builds up at the bottom of the bottle. I don't have any way of getting to the bottom to clean this.

I wanted to know.

  1. What does this green film consist of?
  2. What Chemicals or methods can I use to remove the film without having to manually scrub the bottle?

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ps. not sure if this was the correct place to ask this question.

  • 1
    $\begingroup$ a) algae b) if it has formed a scummy biofilm, it might have to be harsh treatment to get it off. kerosene? $\endgroup$
    – shigeta
    Commented Apr 15, 2015 at 2:14
  • $\begingroup$ @shigeta What about more common household items? $\endgroup$ Commented Apr 15, 2015 at 2:18
  • $\begingroup$ please, remove part on cleaning, as it might be considered as requesting advice concerning personal health. We don't want to be responsible for your/your dog's/your child's chemical poisoning $\endgroup$ Commented Apr 15, 2015 at 4:02
  • 1
    $\begingroup$ try diluted bleach - or if you go to the grocery/hardware store you should be able to buy a bottle brush for cheap. $\endgroup$
    – shigeta
    Commented Apr 15, 2015 at 4:07
  • 1
    $\begingroup$ Another way to "scrub" things you can't reach is with a handful or more of sand or tiny pebbles. Bleach and sand swirled around vigorously for a few minutes will remove the majority of it, if not all. $\endgroup$ Commented Apr 15, 2015 at 5:48

1 Answer 1


What seems to be forming in reusable water bottles and water coolers is a biofilm. Since it is a complicated system, after maturation biofilm might be very hard to remove without scrubbing. There is a nice article about cleaning water coolers, which might give you some information.

If you look closer on the Google Scholar search results, you'll find that quite a bit of research has been conducted in the area of sanitation of water coolers and study of their flora. For example, consider the following paper from 1996: Analysis of the Virulence Characteristics of Bacteria Isolated from Bottled, Water Cooler, and Tap Water.

There is a very nice list (Table 1) of different bacteria isolated from water. But I would like to point your attention to following table from the paper:

Table 3. Antibiotic resistance of water bacteria

Quote from methods section listing tested antibiotics:

The natural and first generation antibiotics included: penicillin, ampicillin, erythromycin, kanamycin, streptomycin, tetracycline, chloramphenicol, and sulphonamide. The synthetic and later generation antibiotics included: gentamicin, cefoxitin, cefoperazone, oxacillin, piperacillin, imipenem, ciprofloxacin, and sulphonamideftrimethoprim

The green slime you observe, I think, is a combination of all those bacteria, plus some that were brought after the water was poured into the container. And it seems that all commercial sources that you didn't purify yourself, will have a variety of microorganisms growing. And around 5% of the total bacterial cell mass is resistant to common antibiotics.


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