Which of the following is an acceptable level of residual chlorine in the far reaches of a distribution system?

The acceptable levels of residual chlorine in a water distribution system are important for ensuring the safety and quality of drinking water. The presence of chlorine, whether as free chlorine or chloramines, indicates effective disinfection throughout the distribution system.

In small Ground Water Systems (GWS), a residual chlorine level of 0.2 mg/L of free chlorine is considered acceptable. This ensures that there is enough chlorine present to maintain disinfection without exceeding levels that could be potentially harmful for consumers.

For large Surface Water Systems (SWS), a residual level of 0.5 mg/L of chloramine is appropriate. Chloramines are often used in large systems instead of free chlorine due to their longer-lasting disinfection properties, which is essential for maintaining water quality across extended distances in a distribution system.

Additionally, for large Surface Water Systems, maintaining a total chlorine level of 1.0 mg/L is also acceptable. This total includes both free chlorine and combined chlorine (formed when chlorine reacts with ammonia).

The option indicating that all of these levels are acceptable demonstrates a comprehensive understanding of the varying requirements for different types and sizes of water systems. Thus, the answer encompasses a range of acceptable residual chlorine levels suited to varying conditions and requirements within the industry, supporting the overall objective