project final draft sewer

8/16/2019 Project Final Draft Sewer

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A propose sewer network design for KBTC

Yivitesh Sookun

National Diploma in Civil Engineering, Cohort

! "ull#Time

The $auritius %nstitute of Trainingand Development


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&iterature review The management of water resources is control by the Ministry of

Energy and Public Utilities in Mauritius. This power has been delegated

to the Water Resources Unit founded in May 199! which is responsible

for the assessment! management! de"elopment and conser"ation of

water resources. #n the past two subsidiary bodies ha"e been

established in Mauritius! the $entral Water %uthority &$W%' responsible

for portable water distribution and the Wastewater Management

%uthority &WM%'! responsible for managing waste water.

The 'astewater $anagement Authorit(Mauritius had its (ewerage Master Plan prepared in the nineties and

then the Wastewater management %uthority &WM%' was proclaimed on

the )th %ugust *))1 in the aim of being responsible for all matters

relating to the collection! treatment and the disposal of wastewater

throughout Mauritius! under the Wastewater Management %ct *)))

and it operates under the wing of the Ministry of Energy and Public

Utilities. (ince the creation of the Wastewater Management %uthority!

it is now called to manage the public wastewater system which

consists of +91 ,m of sewer networ,! -* pumping stations and 1)treatment plants including main treatment plants which are located

at (t Martin! /rand 0aie! 0aie du Tombeau and Montagne ac2uot.

The duties of the 'astewater $anagement Authorit( )'$A*+ To maintain and mange all e3isting public sewer and wastewater

sewer in Mauritius. Regulate the construction of pri"ate sewers! enforce their

maintenance according to standard as may be prescribed and

pro"ide for their inspection. $ontrol and monitor pollution! pri"ate sewers and use of

e2uipment in relation to wastewater systems. To ma,e sure that no storm drainage is connected or get mi3ed

up with the wastewater system.

Page *


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$ontrol and monitor the pollution discharged to wastewater

system by any person. $onduct and underta,e research and studies for the

implementation and de"elopment of pro4ects relating to

wastewater sector. Promoting the treatment and reuse wastewater.

Ensure the generation of su5cient resources from tari6 to

7nance the operation! maintenance and depreciation cost of

wastewater system! sewerage and sewage treatment

installations.

revious works and pro-e.ts The 8ational (ewerage Master Plan &8(MP' was accomplished in the

year 199. The principal aim of this 8ational (ewerage Master Plan

was to pro"ide public sewerage co"erage mainly in the urban areas

about +) of the population by *)1) and :) by the year *)*). The

8(MP goal is to target 1)) connection to the sewerage system by

*)).

(ince 199 the /o"ernment has started implementing the master plan

&8(MP' and has been 7nancing the following pro4ects;

The laines 'ilhems sewerage network


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increasing >ow! hence the Master Plan suggested in pro"iding a new

sewer trun, in the year *))=. The total cost of the new sewer trun,

was Rs .= billion and directing all the >ow to (t Martin treatment

plant.

Baie du Tom/eau sewerage pro-e.t The 0aie du Tombeau sewerage pro4ect consists of two areas;

1. 8orthern Port ?ouis*. 0aie du Tombeau

The aim of this pro4ect was to rehabilitate the 8orthern wor,! collection

of wastewater from the area also including *1)) house connections

and pumping the sewage >ows into the new wastewater treatment

plant.

$ontagne 0a.1uot sewerage pro-e.t This pro4ect consists of transportation! treatment and disposal of

:!))) m3

per day of wastewater from the area of southern Port

?ouis! lower 0eau 0assin and $oromandel also including the industrial

waste of Plaine ?au@an! la Tour Aoenig and Pailles.

"a.ts and 2gures on pu/li. sewer s(stem in $auritius

The per.entage .onne.tion to pu/li. sewer#n *)1)! about *9 number of people were connected to the sewer

system and the remaining -1 uses on site wastewater disposal

system.

The volume of wastewater treated /( pu/li. treatment stationBrom *))1 to *)1)! there has been an increase in the "olume of

wastewater treated by the treatment stations.


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million cubic metres. The "olume rises up to appro3imately +.))

million cubic metres between *))= and *))-.

llustration of 3re(water and Bla.kwater from a household

Consumption of water dail( /( a person(ince water is essential for a human being! they ma,e use of it for

"arious acti"ities in their daily life. %ccording to WCD &World Cealth

Draganisation'! a person uses appro3imately 1+) to 1=) litres of water

daily. Their daily acti"ity consists drin,ing! coo,ing! personal washing!

washing clothes and cleaning home.

Page +


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4sage of water dail( per person in terms of gallons

A.tivities per

person

3allons used

Page =

5 gallons per 6ush

! gallons per da(

Total 7 58! 7 9: gallons

9 minutes of shower

; gallons per da(

Total 7 98; 7 ; gallons

gallons per da(

: glasses of water

9 gallon per da(


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Conversion of gallons to litres

Total usage of water daily per person = 18 + 20+ 2.5+ 1= 41.5 gallons1 gallon = 3.78541 litres

41.5 gallons= 41.5 x 3.78541= 157 litres

?euse of treated wastewater

The reuse of treated wastewater ha"e been a common practice for

de"eloping countries such as %sia and %frica o"er the past few years

and it is now recei"ing particular attention due to rapid urbani@ation.


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'astewater treatment

#n order to reuse wastewater! it is important to treat raw wastewater to

meet speci7c needs and public safety. The wastewater treatment

processes are classi7ed as such;

1. Primary treatment*. (econdary treatment. Tertiary treatment

rimar( treatment Treatment in"ol"es sedimentation &sometimes preceded by screening

and grit remo"al' to remo"e gross and settleable solids. The remaining

settled solids! referred to as sludge! are remo"ed and treated

separately.

Se.ondar( treatment/enerally! a le"el of treatment that remo"es :+ of 0iological D3ygen

occulation and 7ltration.

'astewater treatment pro.ess

Page :


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'astewater reuse areas of appli.ation

Categor( of reuse E8ample of appli.ation

• 4r/an reuse )unrestri.ted*

• @ther

&ands.ape irrigation of

parks, pla(ground, s.hool

(ards, golf .ourse

"ire prote.tion,

Constru.tion

• Agri.ultural "ood .rops

Non food .rop

%rrigation of food .rop for

human .onsumption

%rrigation of 6owers, 2/ers,

fodders= Seed .rops,

pasture .ommer.ial

nurseries, sod farms

• Environment enhan.ement Arti2.ial wetland .reation

• %ndustrial reuse Cooling water s(stem,pro.ess water, /oiler feed

water, toilets, laundr(,

.onstru.tion wash#down

water, air .onditioning

Agri.ultural wastewater reuse

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&Rice farming with treated wastewater in apan!

Aumamoto'

'astewater produ.tion and reuse of treated wastewater in

$auritius#n Mauritius! the rate of consumption of freshwater is high and the

agricultural sector is one of the largest users of water for irrigation

purpose. %lternati"e sources of water supply ha"e been found and it

consists of using treated wastewater and this concept ha"e been using

worldwide and Mauritius should not be an e3ception. The rate of

wastewater is increasing and it is generated from domestic!

commercial and industrial acti"ities. #n *)1* the "olume treated was

9.1 M m3

and it is e3pected to rise about -9.9 Mm3

in *).

'astewater treated and reuse for irrigation purpose

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The irrigation authority signed an agreement with the Wastewater

Management %uthority for the reuse of treated wastewater to tertiary

le"el using UK light in the year *))=. %n e3pected total "olume of

)!))) m3

Iday tertiary treated eNuent is deli"ered by the (t Martin

Wastewater Treatment Plant to the West $oast canal system to irrigate

=)) hectares of sugarcane plantation. The 73ed price charged to

farmers for treated water was :) centsI m3

! but this price was not

a6ordable by the farmers. %fter the e3piration of the agreement in

*))9! the irrigation authority had no alternati"e not to renew the

contract. ?ater the /o"ernment analyse the situation and drop to aconclusion where the price of treated water charged to farmers was

73ed to -) centsI m3

! but again farmers ha"e disagreed and the

Ministry of Energy and Public Utilities had to re"iew the pricing

structure.

$ethodolog(


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retrie"e data needed for the design and construction of sewers

but to record pertinent information about the local conditions

before construction begins and these information are;

1. Maps and other drawing of area

*. ?ocations of streets! alleys! stream! drainage ditches andother features that may a6ect the sewer system

. % bench mar, on each bloc, of street

. ?ocal rainfall and runo6 data

+. $ondition of the soil where sewers will be constructed

?eview design .onsideration and sele.t /asi. design dataand .riteria

Design the sewers

repare .ontra.t drawings and spe.i2.ations

"low of pro.edures in planning, designing and .onstru.tion of

sewers

Stages of sewer design pro.edures The design procedures are composed of + stages and they are as such;

Page 1


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Stage 9# reliminar( site investigation, data .olle.tion and

anal(sis

#denti7cation of area to be ser"ed or de"eloped

$ollect topographic map and geographic data

/ather information about local conditions such as;9= Possible contours at suitable inter"als! high and low

changes on surface slope.;= #ndustry or other utilities5= Physical feature &e3ample; ri"er'= Road layout>= ?ocal rainfall and runo6 data

Underta,e site in"estigation and include sur"eys to identify

potential con>ict with other ser"ices.

Stage ;# reliminar( horiontal la(out of sewers

&a(out of sewers


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The minimum diameter of manholes should be 1*)) mm &:

in' largerdiameters are preferable for large diameter sewers. %

minimum accessdiameter of =1) mm &* in' should be pro"ided.

Stage 5# Design sewer siing

ow rates for each section in the system

(elect pipe si@es! slopes! and in"erts. Perform the hydraulicdesign of the system. Re"ise selections until the design criteria

are met.

Stage # Cost estimation $omplete cost estimate for the design and alternate designs.

$arefully re"iew all designs! along with assumptions! alternates!

and costs.

Stage ># ?evision of design $omplete the plan and pro7le construction drawings and prepare

the speci7cations and other bid documents.


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The manning e2uation was de"eloped to estimate the a"erage

"elocities of >ow rate in open channel.

Where!

K O mean "elocity &mIs'

s O hydraulic gradient &energy loss per unit length'

n O Mannings roughness coe5cient

R O hydraulic radius &m'

?7 Area of liquid (m2)

Wetted perimeter (m)

Determining the minimum and ma8imum velo.ities in

sewer#n this particular section # will gi"e procedures of how to determine the

minimum and ma3imum of sewers. /enerally! "arious formulas are

a"ailable to determine the >ow rate in sewers. ow in both open

and closed conduits.

$inimum velo.it(Ma,ing reference to 0( E8 -+*; *)):! it states that to achie"e the self

cleansing of small diameter sewers! the "elocity should be at least ).-

mIs. % minimum "elocity allows the sewage >ow to self cleanse

amount of silt to be carry through sewers! and help to minimi@e sewer

obstruction. Bor larger diameter sewers up to 9))mm! the minimum

"elocity should be of 1.) mIs to achie"e self cleansing$a8imum velo.it(

The occurring of fast >ow is obtained when the sewer is laid at steepgradient and >ow may become supercritical. Bast >ow is not stable and

will gi"e rise to scouring and ca"itation when pipe surface is not

smooth. The ma3imum "elocity at pea, >ow shall be to mIs.

Page 1=

71n = R

2 /3

= S1/2


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(ometimes due to the topography of the land! sewers with steep

gradient are una"oidable. Cence! to reduce the ma3imum "elocity!

?aying of sewers with >atten gradient with the installation of bac,drop

manhole is re2uired.

The manning e2uation was de"eloped to estimate the a"erage

"elocities of >ow rate in open channel.

"low @pen .hannelDpen channel >ow must ha"e a free surface! where normally free

water surface is sub4ected to atmospheric pressure! which remains

relati"ely constant throughout the entire length of the channel. Types

of >ow in open channel are as follows;

Stead( 6ow 'hen dis.harge )* does not

.hange with time

4niform 6ow 'hen depth of 6uid does not.hange for a sele.ted length or

se.tion of .hannel4niform stead( 6ow 'hen dis.harge does not .hange

with time and depth remains

.onstant for sele.ted se.tionaried stead( 6ow Depth .hanges /ut dis.harge

remains .onstantaried unstead( 6ow Both depth and dis.harge .hange

along a .hannel se.tion

?apid var(ing 6ow Depth .hange is rapid

3raduall( var(ing 6ow Depth .harge is gradual

$anning roughness .oe.ient, )n*When using the manning e2uation in the design of sanitary sewer! the

manning roughness coe5cient "aries due to the following factors;

Page 1-


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1. The types of material use for the design*. The material being transported

The carrying capacity of sewers are mainly reduced by house

connection! 4oints which do not line up properly! deposits in sewers and

coating inside the pipe. Bor such reason when designing sanitary

sewers! assumption ha"e been made where manning roughness

coe5cient are considered to be greater than that which would occur if

clear water carried in a straight and well aligned sewer.

$anning roughness .oe.ient .ommonl( used in sewer design

Page 1:


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Determining the .apa.it( of sewer pipe

Brom them Manning E2uation

71

n = R2 /3

= S1/2

K O Mean "elocity &mIs'

Where!nO Manning coe5cient( O (lope of energy line

When the "alue of K &mean "elocity' is obtained! using the continuity

e2uation to 7nd the discharge in pipe.

Where!Q O ow rate in pipeK O Mean "elocity% O $ross sectional area of >ow

Page 19


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Determining minimum and ma8imum grade#n this section # will be gi"ing procedures of how # will proceed to

calculate gradient of sewer pipe.

#n the design of drainage or sanitary sewer pipe! it should be laid to an

ade2uate gradient where the design will wor, accurately and

functional. #f the gradient of the selected pipe is too steep! the li2uid

may run faster than the solids and thus lea"ing the solids stranded and

could bloc, the pipe. Dn the other hand! if gradient is not too steep

enough! it may also bloc, the pipe as solids may slow down and

become stranded.

/radient may be de7ned as fall di"ided by distance.

&(ection of a pipe'

Basi. formula to .al.ulate gradient for sewer pipe

Where!

1. Ball in a pipe may be de7ned as the "ertical amount by which the

pipe drops o"er a distance*. The distance can be between sections of pipe or between to

manholes.

Page *)

3radient 7 Fall


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Determining grades for sewer pipe

Cal.ulating falls and gradient for pipe To determine the gradient of pipe!

Where!MC 1; Manhole 1MC *; Manhole *

The abo"e formula can be rearranged to 7nd fall if the gradient is

already a"ailable

Cal.ulating invert levels

Consider the se.tion of a pre.ast manhole

Page *1

3radient 7

"all 7 3radient 8


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To 2nd the invert level of sewer pipe the /elow .al.ulation is

use to determine it,

'here,3round elevation in

)m*

Cover in )mm*

Diameter of pipe in

)mm*

Page **

%nvert level of pipe 7 3round elevation F Cover F


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Data Colle.tion%t this stage of my pro4ect # will gi"e an o"er"iew of my data collection.

The 7rst part of my data collection consists of the collection a hard

copy of the location plan of the Anowledge 0ased Training $entre from

the administration department itself.

Dnce # obtain the location plan from the administration o5ce! the

second part of my data collection are as follows;1. To carry out a site in"estigation! to collect data about the local

conditions of the location! whether any structure &manmade or

natural' and ser"ices will a6ect the propose sewer design.*. #dentify potential con>icts with other ser"ices &$W% and $E0' on

location.. To carry out sur"ey to gather information about the topography

of the location.. $ollect speci7cations about di6erent types of sewer pipe

a"ailable on mar,et.

Brom the sur"ey # conducted on the site! the data obtain are as such;

&o.ation plan

Page *


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Data o/tained after .ondu.tion surve( on site The pin, line on the location plan shows the propose sewer line for my

design! and after # conducted my sur"ey on site the data obtain are

shown in the table below.

Page *

oi

nt

Ba.k#sight "ore#sight : 99=:: 9=; A to B

9=9:

C 9=>5> 9=!G 99=GH 9=;9 B to C

>=;

D 9=GH5 9=!9 99=H5; 9=95H C to D

>H=

E 9=!H 9=!> 99=H59 9=;:; D to E

9G=G>

" 9=!H 9=;5G E to "

9;=!


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Where!

C.#; Ceight of #nstrument

R.?; Reduced ?e"el

&o.ation of point A to B )Surve(*

&o.ation of point B to C )Surve(*

Page *+


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&o.ation of point C to D )Surve(*

&o.ation of point D to E )Surve(*

Page *=


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&o.ation of point E to " )surve(*

Page *-


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T(pes of sewer pipes availa/le

The table below shows the di6erent types of sewer types a"ailable on

mar,et.

• As/estos .ement

pipe These t(pse of pipes are

manufa.tured using mi8ed of as/estos

2/ers, sili.a and .ement=

Sies availa/le 9#9 .m internal

diameter and length up to m=

%t .an /e easil( assem/le with the

help of .ouplingsknown as ring tie .oupling=

• itri2ed .la( pipe Kitri7ed clay pipes are made of clay and

are sub4ected to high temperature toachie"e "itri7cation.

Kitri7cation is a process which gi"es the

results of hard and inert ceramic.

Mainly used for gra"ity sewer collection

due to it long life span and resistance

Page *:


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against corrosion.

%d"antages

1. Resistant to corrosion! it can carry

polluted water &such as sewage'.*. #nterior surface is smooth and it is

hydraulically e5cient. Pipe is imper"ious and strong in

compression.


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• lasti. sewers#

C pipe Plastic sewer pipe are recent material used

for sewer pipe. They are a"ailable in si@es

-+ to 1+ mm e3ternal diameter and used

for drainage wor,s

They are resistant to corrosion! lightweight!

economical in laying &4ointing and

maintenance'! pipe is tough rigid and ease

for transportation.

• 3lass 2/er

reinfor.ed plasti.

pipes

These pipes ha"e a better strength! high

tensile strength! durability! high resistance

corrosion and it is lightweight. #t can bemanufactured up to *. m diameter and

1:m in length.

/lass reinforced plastic pipes represent the

ideal solution for transport of any ,ind of

water! chemicals! eNuent and sewage!

because they combine the ad"antages of

corrosion resistance with a mechanical

strength which can be compared with the

steel pipes.re.ast sanitar( sewer manholes sies availa/le on market This table below shows the di6erent si@es of rings a"ailable for precast

manhole. The minimum manhole diameter si@e is -+)mm and the

ma3imum manhole diameter a"ailable is *))mm. &referencing'

Page )


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$oncrete chamber manhole ring

(i@es a"ailable

9))mm 3 *+)mm

9))mm 3 +))mm

9))mm 3 1)))m

1)+)mm 3 *+)mm

1)+)mm 3 +))mm

1)+)mm 3 -+)mm

1)+)mm 3 1)))mm

1*))mm 3 *+)mm

1*))mm 3 -+)mm

1*))mm 3 1)))mm

1+)mm 3 +))mm

1+)mm 3 -+)mm

1+))mm 3 +))mm

1+))mm 3 -+)mm

1:))mm 3 +))mm

1:))mm 3 +))mm

1:))mm3 -+)mm

*))mm 3 +))mm

Con.rete ring .over sla/

Sies availa/le

Hmm 8 !mm

9>mm 8 !mm

9;mm 8 !mm

95>mm 8 !mm

9>mm 8 !mm

9:mm 8 !mm

;mm 8 !mm

Cast iron manhole .over

!& 8 !' 8 9<

!G>& 8 !w 8 9G><

0ase ring(i@es a"ailable

9))mm 3 =))mm

1)+)mm 3 ))mm

Page 1


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1)+)mm 3 =))mm

1*))mm 3 1+)mm

1*))mm 3 ))mm

1*))mm 3 =))mm

1*))mm 3 9))mm

1+))mm 3 =))mm

1:))mm 3 =))mm

*))mm 3 =))mm

4C Sewer pipeSies availa/le

Sewer ipe Dou/le So.ket

Bran.h > Degree

Sies availa/le

;mm 8 99mm

;mm 8 9>mm

;>mm 8 ;>mm

59>mm 8 9>mm

Sewer ipe Coupler

99mm to mm

Sewer pipe Bend So.ket >

Degree

99mm to mm

Page *

Diam

eter)

mm*

'all

Thi.k

ness

)mm*

&engt

h)m*

99 5=; !9> =9 !

; =; !;> !=; !59> G=G !


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3ull( trap outlet

Sies availa/le

>mm 8 G>mm 89>mm

5G>mm 8 Hmm 8

5>mm

4C 3ull( Trap

Sies availa/le

@utlet 99mm

@utlet 9>mm

Design stage

Cal.ulation to determine velo.it( and dis.harge in sewer pipeConsider point A to B

/round slope O100.244−100.000

14.018 O1

57.5

Page


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The actual ground slope is &1I+-.+'! but for the design # will choose a

slope of &1I=)'.

%ssume a sewer pipe of 1+)mm diameter connect to the gully trap

o"er a distance of -m until the stand pipe.

Brom manning e2uation! # will determine the "elocity in the sewer pipe

%pply manning formula; K O1

n. R

2

3 . S1

2

RO Cydraulic radius O

π D

2

4

πD

2

= D

4 O0.15

4=0.0375

(O (lope O &1I=)'nO Manning roughness coe5cientO ).)1

Replacing all "alue appropriately! the "alue obtain for "elocity is 1.1

mIs.

Bor the discharge in the pipe! # will apply the continuity e2uation.

Dis.harge, 7A

%O π D

2

4

%O ).)1-= m2

KO 1.1mIs

QO ).)1-= 3 1.1 O ).)19=

m3

Is

Brom con"ersion1cubic metre O 1))) litresQO ).)19= 3 1))) O 19. ?Is"rom stand pipe to point B# will use the manning e2uation to determine the "elocity.

Page


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R O Cydraulic radiusO

π D

2

4

πD

2

= D

4 O0.2

4=0.05

( O (lope O 160

n O Manning roughness coe5cientO ).)1When replacing all "alues appropriately in the manning e2uation! the

"elocity obtain is 1.mIs.Bor the discharge in the pipe! # will apply the continuity e2uation.

Dis.harge, 7A

%O π D

2

4

%O ).)1 m2

KO 1.mIs

QO ).)1 3 1. O ).)):* m3

Is

Brom con"ersion1cubic metre O 1))) litres

QO ).)):* 3 1))) O ).: ?Is

Consider point B to C The data obtained after # carried out sur"ey are as follows;

/round le"el at point A7 9=;m and at point C7 9=;9m

The distance between % and 0 is >=;m

9= Determine the a.tual ground slope /etween A and B

/round slope O100.244−100.214

50.200 O1

1633.3

Page +


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(ince the actual ground slope is not enough steep! # will choose an

appropriate slope of &1I:)' for the design.;= Assume a sewer pipe 4C of ;mm )=;m* for the design

and using the $anningIs E1uation to 2nd the velo.it( in the

pipe= )


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Consider points C to D# will apply the same method to determine the "elocity and capacity of

sewer pipe UPK$ *))mm.

/round slope O100139−100.214

59.400=

1

792

The actual slope of ground is not enough steep to be use for the

design. # will choose a slope of &1I:)' to proceed with the design.

Brom manning e2uation! # will determine the "alue of K mIs &"elocity'.


π D

2

4

πD

2

= D

4 O0.2

4=0.05

( O (lope O

1

80 O ).)1*+


"elocity obtained is 1.*mIs.

Page -


38/48


%gain # will be using the continuity e2uation to determine discharge in

sewer pipe.Dis.harge, 7A

QO ).)1 3 1.* O ).)-* m3/s

Brom con"ersion1cubic metre O 1))) litresQO ).)-* 3 1))) O -.* ?IsCence! the pipe 0 to $ has a capacity of -.* ?Is.

Consider points C to D#

will apply the same method to determine the "elocity and capacity of sewer

pipe UPK$ *))mm.

/round slope O100139−100.214

59.400=

1

792


design. # will choose a slope of &1I:)' to proceed with the design.


R O Cydraulic radiusOπ

D2

4

πD

2

= D

4 O0.2

4=0.05

( O (lope O 1

80 O ).)1*+


"elocity obtained is 1.*mIs.

%gain # will be using the continuity e2uation to determine discharge in

sewer pipe.Dis.harge, 7A

QO ).)1 3 1.* O ).)-* m3/s

Brom con"ersion

Page :

oint ipe diameter

)mm*

elo.it( )ms* Capa.it( )&s*

B to C ; 9=; 5G=;


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1cubic metre O 1))) litresQO ).)-* 3 1))) O -.* ?Is

Cence! the pipe 0 to $ has a capacity of -.* ?Is.

Consider point D to E

/round slope O100.282−100.237

12.600=

1

280


design. # will choose a slope of &1I1))' to proceed with the design.



π D

2

4

πD

2

= D

4 O0.2

4=0.05

( O (lope O 1

100 O ).)1


"elocity obtain is 1.)mIs.%gain # will be using the continuity e2uation to determine discharge in

sewer pipe.

Dis.harge, 7A

QO ).)1 3 1.) O ).)1 m3/s


QO ).)1 3 1))) O 1 ?Is

Cence! the pipe 0 to $ has a capacity of 1 ?Is.

Page 9

oint ipe diameter

)mm*


C to D ; 9=; 5G=;

oint ipe diameter

)mm*


D to E ; 9= 59


40/48


oint E to "

/round slope O100.282−100.237

12.600 O1

280

The actual ground slope is &1I*:)'! but for the design # will choose a

slope of &1I1))'.

%ssume a sewer pipe of 1+)mm diameter connect to the gully trap

o"er a distance of =m until the stand pipe.

Brom manning e2uation! # will determine the "elocity in the sewer pipe

%pply manning formula; K O1

n. R

2

3 . S1

2

RO Cydraulic radius O

π D

2

4

πD

2

= D

4 O0.15

4=0.0375

(O (lope O &1I1))'

nO Manning roughness coe5cientO ).)1

Replacing all "alue appropriately! the "alue obtain for "elocity is

).:=mIs.

Bor the discharge in the pipe! # will apply the continuity e2uation.

Dis.harge, 7A

%O π D

2

4

%O ).)1-= m2

KO ).:=mIs

QO ).)1-= 3 ).:= O ).)1+1 m3

Is

Page )


41/48


Brom con"ersion1cubic metre O 1))) litresQO ).)1+1 3 1))) O 1+.1 ?Is

"rom stand pipe to point E

# will use the manning e2uation to determine the "elocity.


π D

2

4

πD

2

= D

4 O0.2

4=0.05

( O (lope O 1

100


"elocity obtain is 1.)mIs.Bor the discharge in the pipe! # will apply the continuity e2uation.

Dis.harge, 7A

%O π D

2

4

%O ).)1 m2

KO 1.)mIs

QO ).)1 3 1.) O ).)*=+ m3

Is


QO ).)*=+ 3 1))) O *.- ?Is

Summaried ta/le for velo.it( and .apa.it(oint ipe diameter

)mm*


A to B 9> 9=9 9H=

A to B ; 9=5 =:

Page 1


42/48


B to C ; 9=; 5G=;

C to D ; 9=; 5G=;

D to E ; 9= 59=

E to " ; 9= 5;=G

E to " 9> =:> 9>=9

Cal.ulation to determine invert level

Consider point A to B%t point % /ully trapO =))mm and /round le"elO 1)).)))m

#n"ert le"elO 1)).)))).=O 99.))m


43/48


1

60 Oertical

7.018 O ).11-)m

KerticalO ).11-)m

The fall from point 0 to foot of stand pipe is ).11-)m

#n"ert le"el at foot of stand pipeO 9:.)).11-)O 9-.9*-mConsider point B to C

/round le"elO 1)).*m! /radientO &1I:)'! Pipe diameterO *))mm

%ssume a co"er of *m

#n"ert le"el at point 0O /round le"el $o"er Pipe diameter

#n"ert le"el at point 0O 1)).* * ).* O 9:.)m


44/48


Consider point C to D

#n"ert le"el at point $O 9-.1-m!


45/48


Consider point E to "

%t point B /ully trapO =))mm and /round le"elO 1)).*-m

#n"ert le"elO 1)).*-).=O 99.=-m


46/48


The ta/le /elow shows the invert level and .hainage of the

following points+

Point #n"ert le"el &m' $hainage &m'

% HH= =

0 H:= 9=9:

$ HG=9G !=;9:

< H!=!G 9;5=!9:

E H!=H! 99=5!:

B HH=!5G 9>5=H!:

Page =


47/48


Dis.ussion

Page -


48/48


project final draft sewer

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