Which of the following is a common consequence of excessive chlorine in water treatment?

The development of chloramines is indeed a common consequence of excessive chlorine use in water treatment. When chlorine is added to water, especially in amounts higher than necessary, it can react with ammonia present in the water to form chloramines. Chloramines are a group of chemical compounds that can arise from the reaction between chlorine and nitrogen-containing compounds, such as the ammonia that sometimes naturally occurs in water supplies.

These chloramines are often noted for their potential to create odors and affect water quality taste, which is why water treatment facilities must carefully control chlorine levels. While chloramines can be used as a disinfectant, their presence is usually an indication that chlorine levels were not well managed, leading to undesirable water quality outcomes.

The other choices do not reflect the direct implications of excessive chlorine. For example, while excessive chlorine can influence pH, it primarily does not lead directly to significant reductions in pH or increased acidity, as chlorine itself is a strong oxidizing agent but not a direct acid. Additionally, excessive chlorine generally does not result in a reduction in dissolved oxygen levels by itself; rather, it can help maintain adequate levels of disinfectants but in excess can have negative effects on aquatic life, not typically leading to a straightforward reduction in oxygen.