Relationship Between Chlorine Residual and Oxidation Reduction Potential in Drinking Water and Cost Analysis

Chlorine is a typical disinfectant that is used in water treatment. There are different forms and types of chlorine that are used as disinfectants, City of Tempe uses free chlorine. Regulations require that a residual is detected to ensure drinking water is “safe.” Large commercial buildings can undergo difficulties with maintaining a chlorine residual on every floor due to issues with underusage or lack of occupancy. Monitoring systems can activate an automatic flow of fresh water throughout the building or in a specific location based on set levels of chlorine within the monitoring system. There are different approaches to monitoring chlorine residual. Chlorine sensors are the typical process, but can be very expensive due to replacement materials required to promote further use of the sensor and acquire accurate measurements. Also, the chlorine system may require continual maintenance due to membrane replacement and management of the pressurized flow, which is required for accurate measurements. Oxidation reduction potential (ORP) is an efficient alternative from a cost perspective and accurate if the relationship between chlorine and ORP is understood.