Which parameter is most critical in assessing the effectiveness of chlorination?

Residual chlorine is the most critical parameter in assessing the effectiveness of chlorination because it indicates the amount of chlorine that remains in the water after the disinfection process. This residual is essential for ensuring that the water is protected against microbial contamination. Without sufficient levels of residual chlorine, there may be inadequate disinfection, leading to potential health risks from pathogens.

Measuring residual chlorine is vital, as it helps water treatment operators determine if the chlorine dosage was sufficient and whether the water remains safe for consumption. It also serves as a control measure to ensure that there are effective levels of disinfection throughout the distribution system.

Other parameters, while important, do not directly assess the effectiveness of the chlorination process in the same way. For example, pH can influence chlorine's disinfection capability, as it affects chlorine's forms and their germicidal effectiveness, but it does not indicate how much chlorine is left in the water. Temperature can also impact disinfection efficiency but is not a direct measure of chlorine levels. Conductivity, while useful for assessing water quality in terms of dissolved ions, does not provide direct information regarding chlorine residuals or disinfection effectiveness. Therefore, residual chlorine is the primary focus for evaluating chlorination efficiency.