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TYPES OF FLOW Dry Weather Flow
1. Domestic waste water2. Industrial waste water
3. Waste water from u!lic facilities
". #round water infiltration
Storm Water Flow
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Factors Affecting Dry
Weather Flow
$ate of water sul%
Poulation &rowt'
(Desi&n eriod)
T%e of area ser*ed Infiltration of &round water.
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Factors affecting infiltrationof subsoil water into sewer
lines
Det' of sewer !elow &round water le*el
Si+e of sewerLen&t' of sewer t'rou&' infiltration rone +one
,ature and t%e of soil t'rou&' w'ic' t'e sewer is
laidT%e of -oints wor/mans'i etc.
Sewer material
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Storm water flowT'e storm water flow deends uon t'e
followin& factors
0atc'ment area#round sloe
Permea!ilit% of &round
Etent of imer*ious areaEtent of *e&etation &rowt'
$ainfall intensit%
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Method for estimating
storm water flow
$ational met'od
4565I5$
7ere runoff or storm water flow
4 constant
6 catc'ment area in 'ectares $ intensit% of rainfall in mm er 'our
I imermea!ilit% factor.
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Hydraulic Design Of Sewers1) Chezys Formula:
80($S)9:.; w'ere
0 0'e+%
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2. Mannings formula:
81=n5$9(2=3)5S9(1=2).
w'ere
n mannin&
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3)3) HazenWilliams formulaHazenWilliams formulaBB
8:.C;575($9:.A3)5(S9:.;:).8:.C;575($9:.A3)5(S9:.;:).
w'erew'ere 7 is 7a+en William
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Minimum Veloityof flow
@inimum or self cleansin& *elocit% is t'e minimum
*elocit% reuired to re*ent deosition ? clo&&in& of
sediments.
It deends uon t'e s'ae si+e ? secific &ra*it% of
articles.
$euired at least once in a da%.
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Ma!imum "eloity of flow
T'e maimum *elocit%
at w'ic' no scourin&
action or a!rasion ta/es
lace is /nown as non
scourin& *elocit%
Suc' a *elocit% deends
uon t'e material used
for t'e construction of
sewers
@aterial of sewer@aterial of sewer ,on scourin&,on scourin&
*elocit%(cm=sec)*elocit%(cm=sec)
Eart' c'annelsEart' c'annels A:12:A:12:
Ordinar% !ric/linedOrdinar% !ric/lined
sewerssewers1;:2;:1;:2;:
0ement concrete sewers0ement concrete sewers 2;:3::2;:3::
0ast iron sewer ies0ast iron sewer ies 3;:";:3;:";:
8itrified tile and &la+ed8itrified tile and &la+ed
!ric/s!ric/s";:;::";:;::
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#etangular
Horse$shoe
%$sha&e
'ara(oli
1. 0ircular Sewers
2. ,on 0ircular Sewers B
Forms of sewer
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Signifiane of Cirular Sewers
I. 0ircular section 'as least erimeter ? ma $ for
&i*en area so it is most efficient.II. It reuires minimum uantit% of materials ma/in&
it economical too.
III. 7a*in& uniform cur*ature it re*ents t'e
ossi!ilit% of deosition.
I8. T'e% are easil% manufactured
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Crown Corrosion
H2SO4
DropsAir
H2S
Wastewater
Cement
concrete pipes
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Measures to overcome CrownCorrosion
1.8entilatin& t'e sewers
2.Oeratin& sewers to full run
3.Pretreatment to reduce sul'ate
".Pro'i!it entr% of sul'ides
;.Linin& t'e concrete ies !% *itrified cla% !loc/s.
A.,eutrali+ation of sul'ides !% c'emicals.
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