Since the impurities in the raw water and the allowable impurities in the finished water vary greatly in type and concentration, the water treatment process also varies greatly.
In terms of domestic water (or urban public water supply), raw water from high-quality water sources (well water or well-protected special water supply reservoirs) is only required to be disinfected as finished water;
Raw water from general rivers or lakes, need first to remove turbidity impurities such as sediment, and then disinfect;
Seriously polluted raw water also needs to remove pollutants such as organic matter;
Raw water containing iron and manganese (such as some well water) needs to remove iron and manganese.
Domestic water can meet the water quality requirements of general industrial water, but industrial water sometimes needs further processing, such as softening and desalting.