City of O'Fallon issued the following announcement on Oct. 1.
Effective October 2, 2018, Illinois American Water Company will be switching back to their normal disinfectant to treat water, which is chlorine and ammonia combined. Dialysis patients and renal care facilities should be aware of these changes and adjust their health care practices accordingly.
The City of O’Fallon buys treated water wholesale from the private company, Illinois-American, and then pumps it to all water customers. Therefore, Illinois-American treats the water prior to its delivery to the City of O’Fallon’s pumping station in French Village.
Original source can be found here.