1. Filtration A “polishing” solid/liquid separation step Intended to remove particles Other impacts –biodegradation –organics adsorption (especially to GAC) –Mn and Fe adsorption

2. Water Treatment Processes Sedimentation Coagulation/Flocculation Filtration Disinfection Softening Aeration

3. Filter Operation

4. Deposition in a Filter

5. Disinfection Kill or inactivate pathogens –Bacteria, viruses protozoa Disinfectants –Chlorine (Cl 2, HOCl or OCl - ) –Chloramines (NH 2 Cl or NHCl 2 ) –Ozone (O 3 ) –Chlorine Dioxide (ClO 2 ) –Others: Bromine, UV light Primary purpose for drinking water treatment

6. Chick’s Law cont. where, N o =initial concentration of microorganisms, no./mL N=concentration of microorganisms at time t, no./mL t=time of disinfection, [hr] k=an empirical constant descriptive of the particular microorganisms and disinfectant in use, [hr -1 ] Or:

7. Softening Addition of: –Lime (Ca(OH) 2 ) –Soda Ash (Na 2 CO 3 ) Removes calcium and magnesium Removes particles Can also remove some DOC (Dissolved organic carbon), but not as much as coagulation Uses high pH

8. Hardness Classification

9. Softening Chemistry Ca(OH) 2 + HCO 3 - + Ca +2  2CaCO 3  + 2H 2 O Mg +2 + Ca(OH) 2  Mg(OH) 2  + Ca +2