Environmental engineering

1. LAKSHMI NARAIN COLLEGE OF TECHNOLOGY
BHOPAL
(CIVIL ENGNEERING DEPARTMENT)
Environmental Engineering ( CE-602)
Unit : IV
Topic : Collection and Conveyance of
Sewage ( L-2)
Prepare By : Dr. Anil K. Saxena

2. Collection of sewage
The disposal of waste products ,two works are required
1. Collection works
2. Disposal works
disposal works consist of treatment works and dispose it
safely
Depending upon the type of waste two system may be
employed for collection ,conveyance and disposal
1. Conservancy syatem
2. Water Carriage system

3. Conservancy syatem
• This is an old system in which various types of
wastes, such as night soil, garbage etc are
collected separetely in vessels or disposed in pits
and then removed periodically at least once in 24
hours
• This system is also called dry system in which
various types of refuges and storm water are
collected, conveyed and disposed of separately

4. Types of wastes
• Night soil- Night soils or human excreta in
cesspools is collected separately in pans or
pails and carried on heads of sweepers to a
central place from where it is transported
from where it is tranported in bullock carts or
motor vans to a place away from the town for
its final disposal, in trenches, to give excellent
manure in one or two years.

5. Garbage
• Garbage is collected separately , in dust bins
and conveyed on hand carts or motor van
once or twice in a day
• It may consist of waste matter of both non
combustible as well as combustible type.
• Then it is dumped by suitable method
Sullage and storm water are collected and
conveyed separately in closed or open gutters

6. Advantages of conservancy system
• It is cheaper in initial cost
• The quantity of sewage reaching at the treatment
plant is low
• the storm water goes in open drains, the sewer
section will be small and will run full for the
major portion of the year, due to which there will
be no silting
• In floods if the water level of river rises at the
out-fall, it will not be costly to pump the sewage
for disposal.

7. Disadvantages
• This system is highly unhygienic and cause
insanitary conditions since the excreta starts
decomposing within few hours of its prodution
• Transportation of night soil takes place in open
carts through streets and other crowded localities
. This is highly undesirable
• Insanitation may be there due to carriage of
sullage partially separate system through open
drains laid in the streets.
• Due to improper or careless disposal of night soli,
there are more chance of outbreak of epidemic.

8. Disadvantages ( Contd.)
• The lavatories or premises are to be located
outside the house and slightly away from the
main building the compact design is therefore not
possible.
• The liquid wastes from lavatories etc., during
their washing, may soak in the ground, thus
contaminating the soil and it may also be polluted
due to percolation of waste water.
• The system requires considerable land for the
disposal of sewage.

9. Water Carriage System
• In this system , the collection , conveyance
and disposal of various type of wastes are
carried out with the help of water
• Water is used as medium to convey the waste
from its point of production to the point of its
treatment o
• Sufficient quantity of water is required to be
mixed with the wastes so that dilution ratio is
great that the mixture may just like water

10. Contd…
• The sewers lead the sewerage so collected to a
suitable site where suitability and then disposed
off by dilution
• The garbage is collected separately and conveyed
in the same manner as is done in the case of
conservancy system.
• The wastes form kitchens, baths, wash basins etc.
are also led to the sewers. The sewers are the
underground closed pipes which are laid on
suitable longitudinal gradient

11. Advantages
• The system is very hygienic since the night soil and
other waste water is conveyed through closed conduits
which are not directly exposed to the atmosphere.
There is no bad smell because of continuous flow
• The liquid wastes etc. are directly conveyed through
the sewers, and therefore there are no changes of the
waste water being soaked in the ground .
• . The waste water does not percolate down to join the
ground water. There are no chances of pollution of
water of wells in individual houses if any.

12. Advantages
• The labour required for the operation and
maintenance is extremely small. In fact, the
functioning of the system is practically automatic,
problem.
• The system permits the use of modern methods
of treatment of the sewerage collected through
the sewers. The treated waste water and sewage
can be safely disposed off without any risk.
• The land required for the disposal of the treated
wastewater is very much smaller than that
required for the conservancy system.

13. Disadvantages
• This system is very costly in initial cost. one set
of underground sewer is laid
• The maintenance of this system is also costly.
• During monsoon large volume of sewage is to
be treated whereas very small volume is to be
treated in the remaining of the year.