Do phosphates affect trihalomethane (THM) formation?
The primary cause of THMs is pre-oxidation, with chlorine, of raw water that contains organic precursors. The presence of biological regrowth (biofilm) inside water pipes is another source of organic precursors. After chlorine reacts with organic material, THMs may form. Alternative disinfectants or treatment adjustments will often reduce THM formation. However, phosphates also contribute to lowering system THMs. Phosphates inhibit corrosion effectively in a lower pH (7-7.5) range. THM formation potential is significantly reduced when water is chlorinated at a lower pH (< 8.0). Phosphate inhibitors/sequestering agents minimize corrosion by-product scale formation inside the pipe, thereby keeping the pipes cleaner and free of the biofilm that may generate additional organic precursors if left uncontrolled.
