treatment of water for drinking purpose

1. Treatment of water for
drinking purpose
Subhananthini Jeyamurugan,
18py17, M.Sc., microbiology.
Ayyanadar Janaki ammal college Sivakasi.

2. Introduction
• Water is the elixir of life & Major area of earth surface covered by
water
• Water free from harmful chemicals & disease causing
microorganism is known as potable water
• Water is polluted by industrial, municipal & commercial activities
that release toxic and recalcitrant compound in water effluents

3. Microorganism in domestic water
Bacteria
• serratia
• Streptococcus faecalis
• shigella
• Streptococcus bovis
• klebsiella
• proteus
• E.coli
• Salmonella
• pseudomonas

4. Virus
• Polio virus
Protozoan
• Entamoeba histolytica
• Giardia
Fungi
• Achlya Americana
• Pythium
• Saprolegnia
Algae
• Nostoc & anabaena
• spirulina

5. Water treatment
Primary treatment
Coagulation
Flocculation
Sedimentation
Secondary treatment
Filtration
Tertiary treatment
Disinfection

6. Primary treatment
1. Coagulation
• Coagulant make the small physical particles in the water clump
together (coagulation).
• It is used for removal of solids in suspension
• Coagulants: aluminium sulphate, polyaluminum chloride
• Negative charge on the particles are neutralized by inorganic
coagulants.

7. 2. Flocculation
• The precipitates in the water combine into large particles under natural
processes such as Brownian motion & induced mixing is referred as
flocculation.
• Thicker, denser ‘floc’ floats down and settles out of the water in large tanks
(sedimentation) or is removed during the next stage, filtration

8. • Sedimentation is done when water consists of large sized organic
materials .
• Suspended particles settle down depending on their size & weight
and condition of the stored water
• Rate of sedimentation is enhanced by adding coagulants
• The suspended materials & microorganism entrapped by
coagulants and settle down rapidly
3.sedimentation

9. Fig: sedimentation tank
• Water exiting the
flocculation basin may
enter the sedimentation
tank
• It is a large tank with low
water velocities, allowing
floc to settle to the bottom.

10. Fig: coagulation

11. Secondary treatment
• In the secondary treatment , the soluble waste are removed from
the water coming out from the primary treatment
• It helps to
•Stabilize organic matter
•Remove odor
•Reduce BOD& COD
•Remove non-sedimentable colloidal particle

12. Secondary treatment1. Filtration
• It is the second step of purification
• After sedimentation the water is further purified by passing to filtration
unit
• It is the effective means of removing the microorganism & the other
suspended material
• There are two type of sand filter, such as
Slow sand filter
Rapid sand filter

13. Slow sand filter
• Rate of filtration is slow
• Water passes solely through the filter & collected by tile drain pipes at the
bottom
• In the surface of layer of fine sand a colloidal material, consisting of
bacteria, algae, & protozoa, is attached
• Sand grains have positive charges and bacterial cell walls have negative
charge
• Therefore, bacteria are adsorbed on the surface of sand
• Protozoa ingest bacteria

14. Rapid sand filter
• This method depend on the physical trapping of fine particles and
coagulants.
• The top layer removes organic compound
• About 99% bacteria are removed by this method
• But does not remove giardia lamblia cysts, cryptosporidium
oocysts, cyclospora & viruses
• It is 50 time faster than sloe sand filter

15. Fig: sand filter

16. Tertiary treatment
• It is the final treatment of water
• It remove inorganic nutrients, virus & trace elements from the
effluent
• Tertiary treatment removes
The fine suspended solids
Bacteria
Dissolved inorganic solids

17. Chemical treatment
1.Chlorination
• Most common disinfection method involves some form of chlorine or its
compounds such as chloramine or chlorine dioxide
• Chlorine is a strong oxidant that rapidly kills many harmful micro
organism
• The amount of chlorine required depends on organic matter & number
of microorganism present in the water
• Chlorine fail to kill microbial spores.

18. Fig: chlorination

19. 2.ozone disinfection
• Powerful oxidizing agent which is toxic to most waterborne organisms
• It is an effective method for inactive harmful protozoa that form cysts

20. 3. Neutralization
• Mainly used in industrial water treatment
• Addition of acid or base to adjust pH level
• Calcium hydroxide is used in neutralization of acid wastes

21. Thank you