Water Treatment

Front 1

Water Quality Parameters

Back 1

• Organoleptic parameters
  

- colour, taste, odour, turbidity

• Physicochemical
  

- pH, chloride high calcium/magnesium

• Toxic Substances

- Arsenic, lead, synthetic carcinogens

• Microbiological parameters
• - Pathogens

Front 2

Treatment Requirements

Back 2

• Microbiological and particulate removal
• Microbiological inactivation
• Nitrate removal
• Disinfection by-product removal
• Arsenic removal
• Volatile organics removal
• Synthetic organics
• Inorganics

Front 3

Basic Water Treatment Process

Back 3

• Pre-treatment
  

1. Screening
2. Aeration
3. Chemical pre-treatment
4. Sedimentation
5. Coagulation
6. Filtration
7. Disinfection

Front 4

Treatment Process

Back 4

Aeration:

Remove volatile solutes and odorous substances

- H2S, CO2 CH4 - methane thiol, bacterial

Chemical Pre-treatment:

Removes algae/excess colour

Sedimentation:

Solid/liquid separation

- Natural sedimentation; gravity

Coagulation:

Add aluminum or iron salts,changes electric charges of particles, facilitating aggregation

Flocculation; coagulated mix form larger flocs

Flitration:

Commonly sand

Disinfection:

Killing pathogenic microbes, prevent regrowth

- By-products; Halogenated hydorcarbons

Front 5

Advanced Water Treatment

Back 5

Water from standard treatment is taken to a high quality product.

Front 6

Taste and Odour Compounds

Back 6

• 2-Methylisoborneol (MIB)
  
• Geosmin (GSM)

Produced as metabolic by-products by Cyanobacterial blooms

Front 7

Granular Activated Compound (GAC)

Back 7

Produced by heating organic matter in a controlled atmosphere.

- Used in rapid gravity filters

GAC is positively charged therefore able to remove negative ions from the water

- highly porous

Not effective in removing heavy metals.

Front 8

GAC Adsorption

Back 8

Liquid and gas molecules are concentrated on a solid surface.

Physical Adsorption

Attractive forces at the surface of pore walls attract contaminants through pore channels

Chemical Adsorption

Hydrogen and oxygen on surface (as phenols, carbonyls, esters, etc), take chemical reactions

Front 9

GAC Adsorption:

Adv. / Disadv.

Back 9

Advantages:

• Remove many organic pollutants
  
• Produces high quality water
• Reduce chlorin levels

Disadvantages:

• Expensive
• Can be overloaded
• Regular reactivation
• Not effective for microbe/nitrate removal

Front 10

Biological Activated Carbon

Back 10

Removes disinfection by-products and degrades many organic pollutants.

Front 11

Ozone (O3)

Adv. / Disadv.

Back 11

Unstable gas generated by passing an electric discharge through clean, dry air/oxygen.

- Decays quickly in water, used together with Chlorine.

The most powerful disinfectant in water treatment.

Effective against difficult to treat protozoan parasites. e.g. Cryptosporidium and Giardia

Adv.

Effective at killing viruses

Transforms/breaks down many substances

Disadv.

High energy consumption

can form some toxic compounds (eg.bromate)

Front 12

Ultraviolet Radiation (UV)

Adv. / Disadv.

Back 12

UV irradiation produced by mercury lamps kill bacteria and viruses.

- uncertainty; Cryptosporidium and Giardia

Wavelentgh 250-280nm

Adv.

- No chemicals to water

- Equipment relatively simple to operate/maintain

Disadv.

- Impurities that cause colour/turbidity can reduce effectiveness UV cannot penetrate

-

Front 13

Reverse Osmosis

Back 13

Solubilisation diffusion technique uses semi-permeable membrane.

Membrane acts as barrier to dissolved salts and inorganic molecules