EN8592 – WASTE WATER ENGINEERING UNIT – 1 – PLANNING AND DESIGN OF SEWAGE SYSTEMS SESSION -6 – SEWER APPURTENANCES 04-02-2020 MATHANAKEERTHI S / AP / CIVIL ENGINEERING 1
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EN8592 – WASTE WATER
ENGINEERING
UNIT – 1 – PLANNING AND
DESIGN OF SEWAGE SYSTEMS
SESSION -6 – SEWER
APPURTENANCES
04-02-2020 MATHANAKEERTHI S / AP / CIVIL
ENGINEERING
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Sewer appurtenances
Sewer appurtenances are those structures and devices of a
sewerage system which are constructed at suitable intervals
along a sewer line to assist in the efficient operation and
maintenance of the system.
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1. Inlets
2. Catch Basins or Catch Pits
3. Clean-Outs
4. Manholes
5. Drop Manholes
6. Lamp-Holes
7. Flushing Devices
8. Grease and Oil Traps
9. Inverted Siphons
10. Storm Water Regulators.
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1. Inlets Admits storm water (or rain water) and surface wash flowing
along the roads/streets and convey the same to storm water
sewers or combined sewers.
The water from this chamber leaves through an outlet
provided at its bottom and carried by a pipeline to a nearby
manhole.
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(i) Curb Inlets:
Curb inlets (also called vertical inlets) have
vertical openings in the road curbs through which
storm water flows.
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(ii) Gutter Inlets:
Gutter inlets (also called horizontal inlets) have horizontal
openings in the gutter which are covered by gratings through
which storm water flows.
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(iii) Combination Inlets:
Combination inlets are composed of a curb and gutter inlet
acting as a single unit.
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2. Catch Basins or Catch Pits
A catch basin or catch pit is a device meant for the retention
of heavy debris in storm water which otherwise would be
carried into the sewer.
It is an inlet with its outlet being placed well above its
bottom so that heavy debris such as grit, sand, etc., flowing
along with storm water is allowed to settle down and thus
prevented from entering the sewer.
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3. Clean-Outs
Clean-outs are the devices meant for cleaning the sewers.
These are generally provided at the upper ends of lateral sewers in place of manholes.
A clean-out consists of an inclined pipe, one end of which is connected to the underground sewer and the other end brought up to ground level.
A cover is provided at the top end of the clean-out pipe at the ground level.
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Clean-Outs
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4. Manholes Manholes are the masonry or R.C.C. chambers constructed at
suitable intervals along the alignment of sewers to provide
access to the sewers for the purpose of inspection, testing,
cleaning and removal of obstructions from the sewer lines.
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Spacing of manholes
(i) For sewers of diameter 0.9 to 1.5 m, spacing of manholes
above 90 to 150 m may be allowed.
(ii) For sewers of diameter 1.5 to 2.0 m spacing of manholes at
150 to 200 m may be allowed, which may further be increased
up to 300 m for sewers of over 2 m diameter.
(ii) In case of very large sewers a spacing allowance of 100 m
per 1 m diameter of sewer may be considered as a general rule.
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5. Drop Manholes A drop manhole is a type of manhole which is constructed on
a sewer line where a sewer at a high level is to be connected to another sewer at a lower level.
Such situations may arise as indicated below:
(i) Branch sewers are generally situated at lower depths below the ground level whereas main sewers are laid at greater depths below the ground level.
(ii) In case of ground having steep slope
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6. Lamp-Holes Lamp-holes are small openings provided on sewer lines
mainly to permit the insertion of a lamp into the sewer for the
purpose of inspection of sewer lines and detecting the
presence of any obstructions inside the sewers.
A lamp-hole may serve the following purposes:
(i) Inspection
(ii) Flushing
(iii) Ventilation
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7. Flushing Devices
When sewers are to be laid in a flat country, it is
not possible to obtain a self-cleansing velocity
In such a cases, flushing devices are required
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Flushing Devices
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8. Grease and Oil Traps Grease and oil traps are the chambers provided on the sewer
line to exclude grease and oil from sewage before it enters
the sewer line.
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9. Inverted Siphons
An inverted siphon is a section of sewer which is constructed lower
than the adjacent sections to pass beneath a valley, river, stream,
road, railway and such other obstructions.
It runs full at greater than atmospheric pressure because the crown
is depressed below the hydraulic grade line.
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10. Storm Water Overflow Devices
or Storm Water Regulators
It is, therefore, possible to divert a portion of this combined
sewage and discharge it into a watercourse such as stream,
nalla, river, etc., without any trouble.
This is achieved by providing storm water overflow devices
or storm water regulators in an intercepting sewer so that the
outfall sewer will carry only a portion of the combined
sewage to the sewage treatment plant.
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ACTIVITY
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ACTIVITY
Answer : K
Explanation : The numerical values of the letters in opposite
segments of the circle always add up to 17.
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