What ratio of chlorine to ammonia indicates stage 2 of the Chlorine Demand Curve?

Stage 2 of the Chlorine Demand Curve refers to the point at which chlorine is primarily reacting with ammonia, leading to the formation of chloramines. The key ratio of chlorine to ammonia that indicates this stage is typically known to be around 5:1. This ratio suggests that for every part of ammonia present, five parts of chlorine are necessary to effectively manage and disinfect water while forming chloramines instead of using up all the chlorine to achieve oxidation of ammonia. This approach helps in the development of stable chloramines, which provide a longer-lasting disinfection residual compared to free chlorine alone.

Understanding this concept is crucial for guaranteeing effective treatment processes while balancing the need for disinfection with the presence of ammonia in surface water sources. The other ratios do not accurately correspond to the typical point at which chloramines start to dominate the chlorine demand curve, making them less relevant for defining stage 2.