Which method is commonly used to assess the levels of bacteria in water samples?

The method commonly used to assess the levels of bacteria in water samples is membrane filtration. This technique involves passing a water sample through a filter with a pore size that allows water to pass but retains bacteria. After filtering, the bacteria are typically cultured on a growth medium to enumerate colonies, which can then be counted to determine the concentration of bacteria in the water sample. This method is widely recognized for its effectiveness in detecting viable bacteria and is particularly useful for testing drinking water and recreational water.

In contrast, colorimetric analysis measures the concentration of specific substances in water through color change in a reaction, but it is not specifically designed to quantify bacteria. Conductivity measurement assesses the ionic content of water, which does not directly correlate to bacterial concentration. Gas chromatography is primarily used for analyzing volatile compounds and does not serve as a suitable method for bacterial assessment. Membrane filtration is a standard technique in microbiology laboratories when monitoring water quality for bacterial contamination.