How is total chlorine calculated?

Total chlorine is defined as the sum of the free available chlorine and combined chlorine present in the water. Free chlorine refers to the chlorine that is available to disinfect and is not chemically combined with any other substances. Combined chlorine, on the other hand, consists of chlorine that has reacted with ammonia and other nitrogenous compounds in the water, forming chloramines.

When calculating total chlorine, it is essential to consider both these forms because they represent the overall disinfecting power of the chlorine in the water system. The formula that accurately represents this calculation is free residual plus combined residual, effectively capturing both active and inactive forms of chlorine in the water sample.

Understanding this distinction is crucial for water operators because it allows them to assess the overall effectiveness of chlorine as a disinfectant in the treatment process. Monitoring total chlorine levels helps ensure safe drinking water and compliance with health regulations.