What may indicate a high chlorine demand in water treatment?

A high chlorine demand in water treatment can be indicated by several factors, including the presence of bacteria, pH imbalance, and high turbidity. Each of these conditions can significantly affect how much chlorine is required to effectively disinfect the water.

The presence of bacteria is a primary factor since chlorine is used to kill or inactivate microorganisms. If there are high levels of bacteria in the water, this means that more chlorine will be needed to achieve the desired level of disinfection.

A pH imbalance also plays a crucial role in chlorine demand. Chlorine is most effective as a disinfectant in a specific pH range (typically between 6.5 and 7.5). If the pH is outside this range, the effectiveness of chlorine decreases, potentially requiring higher doses to achieve the same disinfection effect.

High turbidity disrupts the disinfection process as well because turbidity can shield microorganisms from chlorine. More chlorine is therefore needed to penetrate the particulate matter and effectively disinfect the water.

Considering these factors, all contribute to an elevated chlorine demand, making the option that includes all of these elements a comprehensive and correct choice.