The document summarizes various steps in water treatment: Screening removes large debris from surface water. Sedimentation allows particles in water to settle out under gravity. Coagulation uses chemicals to induce settling of fine particles. Filtration separates solids from liquids by passing water through filter media. Slow sand filters treat surface water over 1-2 meters of sand. Chlorination adds chlorine to kill microbes and prevent waterborne diseases.

1. WATER TREATMENT

2. SCREENING
 The first step in purifying
surface water is to remove
large debris such as sticks,
leaves, rubbish and other
large particles which may
interfere with subsequent
purification steps.
 Most deep groundwater
does not need screening
before other purification
steps.

3. SEDIMENTATION
 Sedimentation is the
process of allowing
particles in suspension
in water to settle out of
the suspension under
the effect of gravity.
 The particles that settle
out from the suspension
become sediment, and
in water treatment is
known as sludge.

4. SEDIMENTATION WITH COAGULATION
 When chemical or other
substances are added to
induce settling of finely
divided suspended matter
or large molecules
 Cougulants:
 Aluminium sulphate
(Alum)
 Chlorinated Copperas
 Ferrous sulphate and
Lime
 Magnesium Carbonate
 Sodium Aluminate

5.  Flocculation chamber

6. FILTRATION
 Filtration is the process of separating suspended solid
matter from a liquid, by causing the latter to pass through
the pores of some substance, called a filter. The liquid
which has passed through the filter is called the filtrate.
 Filters use sieving, adsorption, ion exchanges, biological
metabolite transfer, and other processes to remove
unwanted substances from a quantity of water. And unlike
a sieve or screen, a filter can potentially remove particles
much smaller than the holes through which its water
passes.

7. SLOW SAND FILTER
 Slow sand filters are used in
water purification for treating raw
water to produce a potable
product. They are typically 1 to 2
metres deep, can be rectangular or
cylindrical in cross section and are
used primarily to treat surface
water. The length and breadth of
the tanks are determined by the
flow rate desired by the filters,
which typically have a loading rate
of 0.1 to 0.2 metres per hour (or
cubic metres per square metre per
hour).

9. CHLORINATION
 Water chlorination is the process of adding chlorine (Cl2) or hypochlorite to
water. This method is used to kill certain bacteria and other microbes in tap
water as chlorine is highly toxic. In particular, chlorination is used to prevent the
spread of waterborne diseases such as cholera, dysentery, typhoid etc.