All, The answers provided by ...

All, The answers provided by Mr. Meklati are very good for general applications. Maintain process control whatever disinfectant is being used. Practice an aggressive flushing problem, one that will strip biofilms, clean water storage tanks which can serve as storage reservoirs for organism growth, including pathogens and nitrifying bacteria. If you can use free chlorine, stay with that. If not, careful control of chloramination must be practiced or nitrification of the total chlorine concentration will ensue. Pigging of pipelines will work if nothing else does. If using chloramines, and biofilm growth becomes problematic, switch to a period feed of free chlorine. This should be done as a last resort, not routinely.