According to AWWA C651, how much time should pass after the disinfection procedure before sampling for coliform analysis?

According to the AWWA C651 standard, a period of 16 hours should elapse after the disinfection procedure before sampling for coliform analysis. This timeframe allows sufficient time for the chlorine or other disinfectants used during the procedure to dissipate to safe levels, ensuring that the results of the coliform analysis are not influenced by the presence of residual disinfectants. Sampling too soon may yield false results, as any residual disinfectant could inhibit bacterial growth, leading to an underestimation of the presence of coliform bacteria. Therefore, allowing for a full 16 hours ensures a more accurate assessment of water quality, which is critical for maintaining public health and safety standards in water systems.