Sewage appurtenances for wastewater

1. Sewer Appurtenances
BY
R M BHADARAKA

2. Sewer Appurtenances
 The Structure which are constructed along a sewer line at
suitable interval, to assist in efficient operation and
maintenance of the sewerage system

3. Inlets
 Inlets is a device meant to admit the storm water or surface
wash flowing along a streets, into a storm sewer or a combine
sewer.
 The Inlets are provided along the road side on straight roads at
interval of 30 m to 60 m.
 They are connected to nearby manholes by pipelines.
Inlets are not necessary in case of separate sewers

4. Layout of Inlets

5. Types Inlets
 Vertical inlet (Curb inlet)

6. Types Inlets
 Horizontal inlet (Gutter inlet)

7. Catch Basins or Catch pits
 It is a structure in form of a chamber which is provided along
the sewer line to admit clear rain water free from silt, grits,
debris, etc into the combine sewer.
 It is nothing but street inlets provided with additional small
settling basins.
 Also hood is provided to prevent the escapes of foul gases.
When Road were not good, catch pits were mostly used

8. Catch Basins or Catch pits

9. Clean outs
 It is a inclined pipe with its one end connected with underground
sewer line and other end brought up to ground level, with proper
cover at the top.
 It is provided at upper end of lateral sewers in place of man holes.
 They are generally used for cleaning the sewers.
 Water is forced into the clean out pipe, for removing large
obstruction, flexible rod may be inserted in the sewer line through
clean out.

10. Clean out

11. Man holes
 Manhole is a masonry or RCC chamber, constructed at
suitable interval along the sewer diameter.
 The purpose of inspection, testing, cleaning and removal of
obstruction from the sewer line.
 It also help in joining sewer lines or in changing the direction
or alignment or both.

12. Location of Manholes
 It may provided at every bends, junctions, change of gradients
or change of sewer diameter.
 The spacing between two sewer depend upon diameter of
sewer.
Size of sewer Recommended Spacing
Dia. up to 0.3 m 45 m
Dia. up to 0.6 m 75 m
Dia. up to 0.9 m 90 m
Dia. up to 1.2 m 120 m
Dia. up to 1.5 m 250 m
Dia. Greater than 1.5 m 300 m

13. Classification of Manholes
 Shallow manhole
 Normal manhole
 Deep manhole

14. Shallow Manhole(Inspection chamber)
 Shallow manhole is about 0.7 to 0.9m in depth.
 It may constructed at a start of Branch sewer or at places
which are not subjected to heavy traffic.
 It is provided with a light cover at its top.

15. Normal Manhole
 Normal manhole is about 1.5m in depth.
 They are constructed either square (1m X 1m) or Rectangular
(0.8m X 1.2m) in cross section.
 The Section of such manhole is not changed with depth.
 It is provided with heavy cover at its top.

16. Deep Manhole
 Deep manhole has depth greater than 1.5m.
 The size of that manholes vary with depth.
 At top reduce the size of manhole cover.
 Steps are provided on one vertical wall of manhole to enable
the worker to go up to the bottom.
 Heavy cover at its top with C.I. Frame.

17. Manhole

18. Dimension of Manhole
 Minimum internal dimension for manhole chambers as
recommended by IS 1742-1960.Sr No. Depth Min. size specifield
1 0.80 m or less 0.75 X 0.75 m
2 0.8 m to 2.1 m 1.20 X 0.9 m
3 Greater than 2.1 m Circular chamber with min. 1.4 m
Rectangular chamber 1.2 X 0.9 m

19. Component of Manholes
 Access shaft
 Working Chamber
 Bottom or Invert
 Side walls
 Steps or ladder
 Top cover and frame

20. Access Shaft
 The Upper portion of deep manhole is called access shaft.
 Minimum dimension of it 0.6 X 0.75 m for Rectangular shaft
 0.6 to 0.75 m dia. For circular shaft.
 Depth of access shaft equal to depth of manhole minus height
required for working chamber.

21. Working Chamber
 The lower portion of a manhole is known as working chamber.
 It provide space for carryout the repair works.
 The min size of working chamber for rectangular manhole is
about 0.9 X 1.2 m
 For circular section manhole is about 1.2m dia.
 The height of working chamber should not less than 1.8

22. Bottom or invert
 The bottom part or invert or benching is constructed in cement
concrete.
 It may be semi circular or u shaped channel is constructed.
 When branch sewer and main sewer meet at the same level at
bottom of sewer it may be constructed.

23. Side wall
 The side wall of manhole are made of brick or stone masonry or
RCC.
 The minimum thickness of brick wall should be 22.5cm.
 The inside and outside of brickwork should be plastered 20mm
thick with 1:2 cement plaster.
Approximate thickness of side walls may be computed from thumb rule
T = 10 * 4d
Where d = depth of manhole in meter

24. Steps or ladder
 It may provided on one vertical wall to enable the workers to go
up to the bottom.
 The steps are made of C.I. and are placed in staggered at a
horizontal distance about 20 cm to 25 cm and vertical distance of
about 30 cm.
 In deep manhole, ladders provided.

25. Top cover and frame
 The manhole is provided heavy C I cover set in suitable C I Frame.
 The depth of the frame is kept 20 to 25 cm and its width is kept 30 cm.
 It is firmly embedded in the pavement and the cover rests in the
groove which is kept inside.
 Cover may be rectangular or circular.
 The size of cover for rectangular shape 0.6 X 0.45 m and for circular
its being 0.5 to 0.6m dia.
 The top surface carry out mark which placed so that it show the
direction of flow of sewage.

26. Deep Manhole
 Special type of manhole which is constructed to provide a
connection between high level branch sewer to a low level main
sewer.
 When the branch sewer enters a manhole by more than 0.5 to 0.6
m, above the main sewer, the sewage is not allowed to fall directly
into a manhole.
 It may brought through a down pipe taken from the branch sewer
to bottom of the manhole.
 If the drop may be few meter, the down pipe should be laid at 45
angle

27. Deep Manhole

28. Lamp Holes
 Small opening constructed on sewer to permits the insertion of
a lamp into a sewer.
 The lamp light is viewed from the upstream as well as
downstream manholes.
 It consist of vertical CI or stoneware pipe, 20 to 30 cm in dia.
Extending from the ground and connected to sewer line
through a T junction.

29. Lamp hole

30. Flushing Tanks
 Sewer laid on flat gradient may not produce non cleaning
velocity and may get blocked frequently.
 If the non cleaning velocity is not available, flushing tanks
provided near the dead end point.
 Flushing tank store water temporarily, and throw it into the
sewer for purpose of flushing and cleaning the sewer.
 Capacity of flushing tanks about 1/10th of cubical contents of
sewer line served by it.

31. Types of Flushing Tank
 Automatic flushing tank
 Hand operated flushing tank

32. Flushing Tanks

33. Sand Grease
 Waste water from hotels, restaurants, kitchen and industrial
contains grease, oil and fats required to be removed before
wastewater enters in to sewer.
 If it not removed it will stick to the surface of sewer and
became hard and obstruct the flow.

34. Sand Grease

35. Necessity Ventilation
 Continuous flow
 Disposal of sewer gases
 Prevention of unpleasant odours
 It provide fresh air to workers engaged in the repairs and
cleaning of sewer.

36. Methods of Ventilation
 Ventilating columns or shaft
 Proper design and construction of sewer
 Proper house drainage system
 Use of mechanical devices

37. Methods of Ventilation

38. Laying of sewer
 Sewer lying in the ground at design slope.
 The entire process is to be carried out maintaining all safety measures at
all levels of works.
 Marking centre line of sewer pipes of a sewer line on plan of the area and
show the appurtenances on the centre line.
 Excavation of trenches, sheeting bracing, and dewatering is necessary.
 Laying the sewer pipe and joining it.
 Testing of sewer line.
 Backfilling of trenches.

39. Precautions
 Speed limit, work progress boards must be displayed at proper
places.
 Proper protection work is carried out for those structure whose
foundation are very near to excavated trenches.
 Temporary railing should be provided along the periphery of
trenches.
 The work of laying the sewer in trenches should be completed
as soon as possible, delay in it cause inconvenience to traffic.

40. Excavation of Trenches
 The alignment of sewer line either along the centre line or road or
along the periphery.
 Remove the pavements or cut along the edges of trenches.
 Excavation of trenches can be done manually or with the trenching
machines.
 Trench width depends upon sewer diameter and depth of sewer
line below ground level.
 Large size sewers trench width should be 15 cm more than dia. of
sewer so that lowering and adjusting of sewer can be easily done.

41. Excavation of Trenches
 The minimum trench width from 60 to 100 cm is required for
conveniently lowering, lying and joining the sewer.
 Smaller size sewers the trench of width 15 cm greater than
dia. is excavated but at the end of the sewer the trench width
has to be kept 60 to 80 cm.

42. Testing of Sewer
 It determine the quantity of leakage and identify the leakage
points in the joints.
Water test
Air test

43. Water test
 Water from the downward end is filled to sewer.
 Upper end of sewer air release pipe along with stopcock is fitted.
 Upper and lower end is plugged but funnel is fitted to it to pur
water in sewer.
 All air expelled from upper end.
 Water level in the upper end pipe is noted 30 minutes and total loss
in water computed.
 Total loss not greater than 15ml for small dia. And 30ml for larger
pipe dia. pipe of 100m

44. Air test
 When the pipe is very large air test is used for identify the
leaking joints.
 Air is filled with pressure by hand pump and pressure of 200
mm of water is developed.
 If the water drop below 75mm, there are necessary to find out
leaking joints.
Detect of leakage points is to sprinkle soap water which shall show foam formation if
leakage is more.