The article is not saying chlorine doesn't work... It's saying don't poo in the pool. The shock is not primarily to kill bacteria, but to deal with the amines.

The article is not saying chlorine doesn't work... It's saying don't poo in the pool. The shock is not primarily to kill bacteria, but to deal with the amines. It is designed to disperse, because the concentration of chlorine would be far too high for people -- usually 10x the normal level of free chlorine. If you went into a pool with so much contamination (ammonia products or slime) that pool shock wouldn't work, you'd be getting very sick. UV does not remove chlorine (chlorine ions are elemental), but it does break down amines and kill pathogens. How it works is complicated: 259983997_Effects_of_Combined_UV_and_Chlorine_Treatment_on_the_Formation_of_Trichloronitromethane_from_Amine_Precursors Many areas with water restrictions ban dumping and refilling pools, which would in many cases would incur a cost of thousands of dollars, vs $30 for a bucket of shock.