The importance of preliminary clarification

Disinfection treatment by simple addition of a disinfectant can only be applied to natural water that complies in all circumstances with physico-chemical drinking water standards, since in this case only the bacteriological quality is corrected.

Based on what we know about the characteristics of natural waters, it's conceivable that if simple disinfection treatment can be applied to groundwater that's free of iron, manganese, ${\text{NH}}_4^{+}$ , nitrates, H ₂ S, etc., and otherwise unpolluted, very few surface waters will be able to make do with...