Water microbiology test methods (ISO Methods)
Description
This laboratory exercise introduces students to the internationally standardized (ISO) methods used to assess the microbiological safety of drinking water. Working with a digital calculation tool built around eleven key ISO standards, students will practice recording sample metadata, entering raw laboratory data such as colony counts, filtered volumes, dilution factors, and MPN tube results, and applying the correct formula for each method to determine microbial concentrations in units such as CFU/100 mL, CFU/250 mL, MPN/100 mL, or CFU/L. The exercise covers detection of key indicator and pathogenic organisms including E. coli, total coliforms, intestinal enterococci, Pseudomonas aeruginosa, Clostridium perfringens, sulfite-reducing clostridia, and Legionella, and requires students to interpret their calculated results against recognized drinking-water quality limits to determine whether a sample passes or fails compliance.
Learning Outcomes
By the end of this lab, students will be able to identify which ISO method applies to a given target microorganism and water type; correctly perform the calculations required to convert raw colony counts, filtration volumes, dilutions, or MPN tube data into standardized microbial concentration units; distinguish between culture-based and molecular (qPCR) detection approaches and understand the practical implications of each; apply recognized regulatory thresholds to determine pass/fail status for a water sample; and accurately document and report laboratory findings in a format suitable for regulatory or quality-assurance review.