I live in Indonesia and there are lots of sewage pipes discharging directly from homes/restaurants/etc directly into the river. It's also common to wash clothes and so on, so there is likely detergent in there as well.

Some water courses that people bathe in seem to be more s**t than water, if you see what I mean, in that it starts off in the river, then diverts into various smaller canals which often end up with trash, diapers, and so on.

I'm wondering what I could do to test/measure this in simple & low-cost fashion, so that I could test in different places and on different dates, and possibly to include quantative values such as 'how much dirtier' the river is when there are many people bathing in it, or when it is dry season, or whatever.

I think I don't need to test for every pathogen so it might be sufficient to just test for E coli? [I think S. aureus is also common, as skin boils tend to occur after bathing in dirty water.]

  • $\begingroup$ I don't have a good answer for you, but I'd note that this sort of thing is often a target of international health organizations. $\endgroup$
    – Bryan Krause
    Sep 18, 2020 at 23:38
  • $\begingroup$ You could start by reading about the presumptive coliform count: microbeonline.com/…. I'd also recommend reading a textbook of microbiology/public health for more detail, because this is a standard topic in those fields. An example is: universitiespress.com/details?id=9789389211436. $\endgroup$
    – Adhish
    Sep 19, 2020 at 9:50

1 Answer 1


The best and most common would be the "multiple fermentation tube” or “most probable number” technique. Rather than testing for all pathogenic bacteria, it uses indicator microorganisms to assess the potability of the water. You'll need a lab to do this but if you have access to one, I'm sure that all the needed materials are common there. Here's a copy of the method: https://www.who.int/water_sanitation_health/resourcesquality/wqmchap10.pdf


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