Filtration

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 (Cl2, HOCl or OCl-)
• Chloramines (NH2Cl or NHCl2)
• Ozone (O3)
• Chlorine Dioxide (ClO2)
• Others Bromine, UV light
• Primary purpose for drinking water treatment

6
Chicks Law cont.
where, No 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 (Na2CO3)
• 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 HCO3- Ca2 ? 2CaCO3 ? 2H2O
Mg2 Ca(OH)2 ? Mg(OH)2 ? Ca2