You can try to spin down your sample, then decant the majority of the supernatant, re-suspend pellet and culture for MPN.

If you can find a way to get a larger volume of sample, you can try tangential flow filtration (might be able to use this for the small volume too).

I am not sure that I understand your comment concerning "preenrich pathogens".

Hello Scott C. Thomas,

Let me explain on the thought about "preenrich pathogens". I think that is not the right term, my apology.

In that context, I mean first increase the pathogen concentration by mix water samples in enrichment media and incubate overnight. Then, I would use that enriched culture to inoculate to MPN. Consequently, the MPN concentration would not be the original concentration in water samples but it is concentration of enriched pathogens. Therefore, I think about constructing the standard curve/relationship between concentration of pathogen in original water samples and concentration after enrichment, which would be useful to do back calculation. However, I am not sure whether this idea is reasonable or reliable. \

Thank you again

Dear Saingam

I think You measurement is appropriate. But, you can thrive the pathogens by subculture in in enrichment broth to increase the quantity and growth mass of microorganisms and eventually increase CFU/ml.

Thank you Mushtak