Which two constituents should be regularly sampled and tested from the distribution system?

The two constituents that should be regularly sampled and tested from the distribution system are coliform bacteria and chlorine residual. This choice is pivotal as both constituents are essential for assessing water quality and ensuring public health safety.

Coliform bacteria are indicators of microbial contamination in water. Their presence suggests that the water may be contaminated with fecal material, which can harbor pathogens capable of causing illnesses. Regular testing for coliform bacteria allows water utilities to detect potential contamination issues quickly and implement necessary corrective actions to protect consumers.

Chlorine residual is equally critical, as it is indicative of the level of disinfection maintained in the distribution system. Chlorine is commonly used to disinfect water and prevent the growth of harmful microorganisms in the water supply. Regular monitoring of chlorine residual ensures that adequate disinfection is occurring throughout the distribution system and helps to prevent the development of biofilms and regrowth of pathogens in the water.

In contrast, while lead and copper are important to monitor, especially in systems with aging infrastructure, they are typically tested less frequently as part of a targeted regulatory compliance effort rather than regular sampling at various points in the distribution system. Nitrates and phosphates, though monitoring for them is important for understanding nutrient levels and potential eutrophication, are generally less critical for