Wastewater New York State Practice Exam

In the context of wastewater treatment, what does MPN stand for when measuring fecal contamination?

1. Most Probable Number

2. Maximum Permissible Nitrate

3. Minimum Purification Network

4. Microbial Pollution Nucleotide

The correct answer is: Most Probable Number

In wastewater treatment, MPN stands for Most Probable Number. This statistical method is used to estimate the concentration of viable microorganisms, particularly fecal coliform bacteria, in a water sample. MPN is based on multiple tube fermentation techniques and is commonly employed in assessing water quality. It involves inoculating a series of tubes with the sample and monitoring gas production as an indicator of bacterial activity. The results are then interpreted using statistical tables to provide an estimate of the bacterial concentration. The significance of MPN lies in its effectiveness for detecting and quantifying fecal contamination, which is critical for ensuring water safety and public health. This method is particularly useful in scenarios where other plating techniques are not feasible or when dealing with dilute samples. Understanding MPN is essential for wastewater treatment professionals, as it plays a vital role in monitoring compliance with health standards and regulations concerning water quality.