1. WATER QUALITY (Chapter 22)
Turbidity
pH-value
Hardness
Some additional information on hardness
Carbonate hardness (caused by Ca and Mg salts) results from dissolving of limestone by rainwater.
Carbonate hardness is not stable.
It precipitates when water is boiled.
Hardness can also be non-carbonate that will not be precipitated by boiling.
Total hardness (TH) of water = Carbonate hardness + Noncarbonate hardness. 
TH is expressed in ppm (parts per million) as calcium carbonate equivalent. (Parts per million and milligrams per liter (mg/l) mean the same thing.)
Water with a TH of less than 17.1 ppm (mg/l) is considered as soft.
Biochemical Oxygen Demand (BOD)

2. WATER TREATMENT (Chapter 22)
Oxidation (Aeration)
Sedimentation
Filtration
Some more information on filtration
Types of filters:
Slow sand
Pressure sand
Diatomaceous earth
Porous stone
Activated carbon
Reverse osmosis
a process in which water with a high concentration of dissolved materials is passed through a semi-permeable membrane in order to get water with a low or no concentration of dissolved material.
Disinfecting

3. WATER TREATMENT (Chapter 22)
Softening
Zeolite system: single-phase ion exchange
Deionization (additional iformation)
Removal of all ionized minerals and salts from a solution by a two-phase ion-exchange procedure.
Positively charged ions are removed by a cation exchange resin in exchange for a chemically equivalent amount of hydrogen ions.
Negatively-charged ions are removed by an anion exchange resin for a chemically equivalent amount of hydroxide ions.
The hydrogen and hydroxide ions introduced in this process unite to form molecules of water.