The document summarizes the process of treating water for drinking purposes. It discusses three levels of treatment: primary, secondary, and tertiary. Primary treatment includes coagulation, flocculation, and sedimentation to remove solids. Secondary treatment is filtration to remove additional particles and microorganisms. Tertiary treatment is disinfection through methods like chlorination or ozonation to kill remaining pathogens. The overall water treatment process aims to remove solids, organisms, and chemicals to produce potable water safe for human consumption.

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