Method of excreta disposal
-Service type latrines
-Non-service type latrines
-Water carriage system & sewage treatment
According to WHO: “Sanitation generally refers to the
provision of facilities and services for the safe disposal
of human urine and faeces. Inadequate sanitation is a
mojor cause of disease world-wide and improving
sanitation is known to have a significant benefecial
impact on health both in households and across
METHOD OF EXCRETA DISPOSAL
I. UNSEWERED AREAS:
1. Service Type Latrines (Conservancy system):
Night soil is collected from pail or bucket type of
latrines by human agency, & later disposed of by
burying or composting.
2. Non-service type (Sanitary latrines):
a. Borehole latrine
b. Dug well or pit latrine
c. Water-seal type of latrines
ii. R.C.A type
iii. Sulabh Shauchalaya
d. Septic tank
e. Aqua privy
3. Latrines suitable for camps & temporary use:
a.Shallow trench latrine
b.Deep trench latrine
-Activated sludge process
c. Other Methods:
Excreta disposal in unsewered
1. Service Type (Conservancy System):
Colletion & removal of night soil by human agency is
called service type or conservancy system & the
latrines are called as service latrines
The night soil is carried by night ‘soil carts’ to the
place of final disposal where it is disposed by:
ii. Burial in shallow trenches
2. Non-service type of latrines (Sanitary
Excreta sould not contaminate the ground or surface
Excreta should not pollute the soil
Excreta should not be accesible to flies, rodents,
animals & other vehicles of transmission
Excreta should create a nuisance due to odour or
TYPES OF SANITARY LATRINES:
1. BORE HOLE LATRINE:
It is the forerunner of the nonservice type of latrines.
First introduced by Rockefeller
foundation during 1930’s.
It consist of a circular 30 to 40
cm in diameter dug vertically
into the ground to a depth of 4-8
cm most commonly 6m.
Auger is required to dig a bore
In loose soils the hole is lined
with bamboo matting or earthen
A suitable foot rests is placed
over the hole
When the contents reach within
50 cm the squatting plate is
removed & the hole is closed.
No need of services of a sweeper
The pit is dark & unsuitable for fly breeding
If the bore hole is located 15 m away from a source of
water supply there should be no danger of water
Bore hole fills up rapidly
Auger is required which may not be readily available
Difficult to dig a hole deeper than 3 m in loose soil
2.DUG WELL OR PIT
First introduced in Singur, West Bengal in 1949-1950
A circular pit about 75 cm in diameter & 3-3.5 m deep
is dug into the ground.
In sandy soil the pit deepness is reduced to 1.5- 2 m.
Pit is lined with pottery rings to prevent caving of the
A concrete squatting plate is placed on top of the pit &
the latrine is enclosed with a superstructure.
Easy to construct & no special equipment is required.
The pit has longer life because of greater cubic capacity.
A pit of 75 cm diameter & 3-3.5 m deep will last for about 5
yrs for a family.
3.WATER SEAL LATRINE:
Improvement in the designing for rural families is the
hand flushed “water seal” type latrine.
Squatting plate is fitted with a water seal.
2 important function:
1. Prevent access of flies by
a small depth of water in
a bent pipe called trap.
2. Prevents escape of odours &
foul gases & thereby eliminate
the nuisance from smell.
Invention of a patna-based firm.
Low cost pour-flush, water seal type of latrine.
It consist of specially designed pan & a water-seal trap.
It is connected to a pit 3 feet square & as deep.
Excreta undergoes bacterial decomposition & is
converted to manure.
Requires very little water.
4. SEPTIC TANK
Key component of the septic system.
A small-scale sewage treatment system common in
areas with no connection to main sewage pipes
provided by local governments on private
It is a satisfacory means of disposing excreta & liquid
wastes but do not have access to a public sewerage
There are various designs: single chambered & double
chambered septic tanks.
Single chambered: for small installations.
Two compartments are expensive.
The main design features:
Capacity: The minimum capacity should be 500
Length: length is usually twice the breadth.
Depth: 1.5-2 m.
Liquid depth: 1.2 m
Air space: Minimum of 30 cm between the level of
liquid & undersurface of the cover.
Inlet & outlet:
Working of Septic Tank:
The solids settle down to form sludge.
Lighter solids form scum.
The first stage of purification called anaerobic
A portion of solid is transferred into liquids & gases
in the form of bubbles.
Effluent contains numerous bacterial, cysts, organic
matters in solution or fine suspension.
The effluent is allowed to percolate into sub-soil by
means of perforated or open-jointed pipes laid in
Millions of aerobic bacteria in the upper layers of soil
attack the organic matter present in the effluent.
Thus the organic matter is oxidised into stable end
Operation & Maintenance:
Use of soap water & disinfectants should be avoided as
they are injurious to bacterial flora.
Desludging: Contents of the tank should be bailed out
atleast once a year.
New built tank is first filled with water & then seeded
with ripe sludge from another septic tank.
5. AQUA PRIVY:
It functions like a septic tank.
It consist of a water-tight chamber.
A short drop pipe dips from latrine floor into the
The shape of the tank may be circular or rectangular.
A capacity for 1 cubic m is recommended for 6 yrs or
Night soil undergoes purification
by anaerobic digestion.
A vent should be provided for
escape of gases.
It should be treated the same
manner as the septic tank.
The digested sludge should be
removed at intervals.
LATRINES SUITABLE FOR TEMPORARY
1. SHALLOW TRENCH LATRINE:
30 cm wide & 90-150 cm deep.
Length depends on number of users: 3-3.5 m for 100
Seperate trenches for men & women should be provided.
Earth from trench should be piled up at the side.
Its an arrangement for a short period (1 week).
It must be covered when the trench is filled 30 cm
below the ground level.
2. DEEP TRENCH LATRINE:
Intended for longer duration( a few week- a few
Its 1.8-2.5 m deep and 75-90 cm wide.
A superstructure is built for privacy & protection.
II. SEWERED AREAS
WATER CARRIAGE SYSTEM:
Its collecting & transporting of human excreta & waste
water by a network of sewers to the place of ultimate
There are 2 types of carriage system:
i.The combined sewer system: (sewage & surface water)
ii.The seperate sewer system: (sewage)
A Water Carriage System consists of the
1. HOUSEHOLD SANITARY FITTINGS:
The usual household sanitary fittings:
2 types: Indian Squatting type & Western Commode
The water closets are provided with a ‘flushing rim’.
The closet is connected to a cistern by a pipe 2.53.75cm in diameter.
The flushing cistern normally holds 15 l of water
For efficient performance of water closet:
-Water seal area should not be more than
-There should not be any sharp corners in
-The volume of water should not exceed
1.75 l to maintain a minimum of 50 mm
deep water seal.
-The interior of the bowl should be
vertical atleast 50-75 mm just above the
surface of water seal.
10 cm in diameter & is laid in the courtyard about 15
cm below the ground level.
The house drain empties the sewage into the main
Not less than 22.5 cm in diameter, bigger ones may be
2-3 m in diameter.
Laid 3 m below ground level with ‘self cleansing’
velocity of 2-3 feet per second.
4. SEWER APPURTANCES:
These are manholes & traps.
Manholes are placed:
i. whenever there is a change in direction of sewer.s
ii. at the meeting point of 2 or more sewers.
iii. at distance of 100 m in long straight runs.
Traps are placed in 3 situation:
i.under the basin of water
ii.where the house drain joins
the public drain
iii.where surface wastes water
enters the drain.