How to quantitatively determine the microbe content in liquids and enumerate them?

Answer 1

You could use a turbidometric method that could detect the diffraction of light through the liquid and correlate it with the amount of microbial growth in it.

You could also use a calibrated loop to plate the liquid and then count colonies. I know they do this with urine cultures in hospital labs at times. The loop picks up a certain amount of liquid like 10 microliters or so and then you can correlate the growth with this 10 microliter figure.