4e3eafac_ell_Water_Treatment_Strategies__What_it_does
[Treatment process] Reverse osmosis (and other membranes) [Contaminants Removed/Altered] Ions: sodium, chloride, lead, nitrates, arsenic, etc. This process can also be used to extract water from maple sap in order to make the syrup processing more efficient. [What it does] 
Untreated, pressurized water is pushed against very fine filter (membrane) under pressure. While clean water is squeezed through, many contaminants are flushed to waste. Often used as a drinking water solution. Typically silt, manganese, iron and hardness are removed prior to reaching the membrane in order to prevent fouling.
Well Water Treatment Strategies
What it does