A color change or the production of gas indicates the presence of coliform bacteria. Chlorine is the most widely used drinking water disinfectant in North America. Chlorine is added to drinking water as a solution. When the level of chlorine is above 0.5 parts per million, most people can smell chlorine in the water. State regulations require at least 0.2 parts per million of chlorine throughout the distribution system.
Chlorine is measured in the field using a portable instrument.
One way to reduce TTHM levels has been to change from chlorine disinfection to chloramine disinfection. Many of the public supplies in Volusia County utilize chloramine disinfection for this reason. Ozonation is also used as an alternative disinfectant to chlorine to minimize TTHM formation. Monitoring levels of TTHM is part of water quality assurance. The federal secondary drinking water standard for TDS is 500 parts per million.