How long must water remain in a natural body of water during indirect potable reuse before it can be used for drinking?

In indirect potable reuse, the water that has been reclaimed for drinking purposes is typically stored in a natural body of water for a certain duration to facilitate natural purification processes. This period allows for biological, chemical, and physical processes to occur, which help to improve water quality and remove contaminants.

A duration of 30 days is generally regarded as sufficient for allowing these natural processes to significantly reduce pathogens and additional pollutants through various mechanisms such as sedimentation, dilution, and microbial activity. During this time, the water can undergo natural filtration and treatment via the ecosystem.

Longer retention times, such as 60 or 90 days, may offer additional treatment and further improve water quality, but the 30-day period is considered adequate in many regulatory frameworks and practices to meet safety standards for indirect potable reuse. This balance between ensuring water quality and managing practical considerations such as availability and system efficiency underlines why 30 days is a widely accepted minimum timeframe.