What is the procedure for quarterly THM sampling?

Collecting four samples on the same day for each treatment plant is the appropriate procedure for quarterly Total Trihalomethanes (THM) sampling. This method is designed to provide a consistent snapshot of the THM levels in the water supply, allowing for accurate evaluation and comparison across different treatment plants within a single quarter. By sampling all at once, the variability introduced by different days and conditions is minimized, making it easier to understand the overall water quality.

The process captures the highest potential THM concentration that might occur throughout the system at the same time, which is crucial for compliance with regulatory requirements and maintaining water safety standards. Conducting the sampling in this manner ensures that the results can be effectively monitored and any necessary adjustments can be made to the treatment processes if elevated THM levels are detected.

Other methods mentioned, such as sampling from all households or only one sample per month, would not effectively gauge the THM levels across the system in a standardized way, potentially leading to misleading results regarding overall water quality. Similarly, taking four samples on different days could introduce variability that complicates the assessment of the treatment plant's performance over the quarter.