This document discusses the treatment of water for drinking purposes. It outlines the microorganisms commonly found in domestic water supplies and describes the multi-step water treatment process. The primary treatment involves coagulation, flocculation and sedimentation to remove solids. Secondary treatment uses filtration to remove remaining particles. Tertiary treatment employs disinfection methods like chlorination and ozonation to kill microbes. The overall process aims to produce potable water that is safe for human consumption.

1. Treatment of water
for drinking purpose
M.SRIDEVI
II M.SC MICROBIOLOGY
18PY15

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. 3.sedimentation
• 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

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 treatment
1. 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
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