gautam project

8/2/2019 Gautam Project ...

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SUBMITTED TO : SUMMITTED BY:

MR.DEVENDRA GAUTAM BUDH

ASST.POFESSER HEMANT MEENA

ENVIRONMENTAL ENGG. LAKHMI CHAND



INTRODUCTION

Sewage treatment is the process of removing

contaminants from house hold sewage, both runoff

(effluents) and domestic. It includes physical,

chemical, and biological processes to remove physical,chemical and biological contaminants. Its objective is

to produce a treated effluent and a solid waste or

sludge suitable for discharge or reuse back into the

environment.



DESIGN PERIOD:

A sewerage scheme involves the laying of underground sewer

pipes and construction of costly treatment units, which cannot be

replaced or increased in their capacities easily or conveniently at

a later date. In order to avoid such complications, the futureexpansions of the city and consequent increase in the sewage

quantity should be forecasted to serve the community

satisfactorily for a reasonable year. The future period for which

the provision is made in designing the capacities of variouscomponents of the sewerage is known as design period. This

sewage treatment plant is designed for 30 years.



Population forecast Year populatio

n

Increment per

decade

Incrementa

l increase

% increment per decade

1951 198000

1961 264393 +66393 (66393 /198000)×100=33.5

1971 329830 +65437 -956 (65437 /264393)×100=24.75

1981 441552 +111742 +46285 (111742 /329830)×100=3.56

1991 509510 +97958 -43764 (97958 /441552)×100=22.18

2001 714077 +204597 +136639 (204597 /509510)×100=40.15

2011 873725 +159648 -44949 (159648 /714077)×100=22.35

Net value +675755 +93255 146.49

Average 112625.8333 18651 24.41



Population for the year 2021

= population of 2011+ avg. increment per decade + avg.

incremental increase

= 873725 + 112625.83+18651 = 1005001.83

Population for the year 2031

=1005001.83 +112625.83+18651 =1136278.66

Population for the year 2041=1136278.66+112625.83+18651 = 1267555.5



CALCULATION OF SEWAGE GENERATION

Ultimate design period = 30 years

Forecasted population at 2041 = 1267555.5

Per Capita Water Supply = 135 lpcd

Avg. water supply per day =1267555.5 × 135=171119992.5= 171.1 MLD

Avg. sewage generation per day = 80% of supplied water

= 0.8 × 171.1 = 136.88 MLD



In cumec,

Avg. sewage generation per day

=(136.88 ×1000)/(24 ×60 × 60)=1.58

Avg. discharge = 1.58 cumecMax. discharge = 3 x avg. discharge

= 3 x 1.58

= 4.74 cumec



FLOW DIAGARME OF SEWAGE TREATMENT PLANT



RECEIVING CHAMBER

• Receiving chamber is the structure to receive the rawsewage collected through Under Ground Sewage Systemfrom the city. It is a rectangular shape tank constructed atthe entrance of the sewage treatment plant. The mainsewer pipe is directly connected with this tank



DESIGN OF RECEIVING CHAMBER

• Design flow = 4.74 cumec

• Detention time = 60 sec

• Volume required = flow X detention time

• = 4.74 x 60• Vrqd = 284.4 m3

• Provide, depth = 3m

• Area = 94.8 m2

• Length: Breadth = 2:1

• L x B = 2B x B =2B2 = 94.8

• B =6.88≈ 6.9 m

• L = 13.77≈13.8m



CHECK FOR DESING FOR RECIVING CHAMBER

• Volume designed = 3 x 6.9 x13.8

• Vdes = 285.66 m2

• Vreq = 284.44 m3

• Vdes > Vreq



RECEIVING CHAMBER

Receiving chamber is designed for the size of

13.8m X 6.9m X 3m (SWD) + 0.5 (FB)



SCREENING

Screening is the very first operation carried out at a sewagetreatment plant and consists of passing the raw sewagethrough different types of screens so as to trap and removethe floating matter such as tree leaves, paper, gravel,

timber pieces, rags, fibre, tampons, cans, and kitchenrefuse etc.It is used to

1 To protect the pumps and other equipments from thepossible damages due to floating matter.

2 To remove the major floating matters from the rawsewage in a simple manner before it reaches into thecomplex high energy required process



DESIGN OF COARSE SCREEN

Peak discharge of sewage = 4.74 m3 /s

Assume the velocity at average flow is not allowed toexceed 0.8 m/s

The net area screen opening required = 5.925m2

Clear opening between bars = 30 mm = .03 m

Using rectangular steel bars in the screen, having 1 cmwidth, and placed at 3 cm clear spacing, we have thegross area of screen required = (5.925×4) /3 =7.9 m2



Assuming that screen bars are placed at 60° to thehorizontal, we have the gross area of screen needed=7.9/sin600= 9.122 m2

Hence a coarse screen of 9.122 m2 area is required.

No. of clear opening = 9.122/.03 = 305

Width of channel = (305×30)+(306×10) =12210 mm =12.21m

Provide width of channel =12.3 mCoarse screen channel is designed for the size of 12.3m×.8 m×(swd) + .5 m (fb)



COARSE SCREEN



FINE SCREEN DESIGN

Design flow = 4.74 cumec

At avg. flow design velocity = 0.8 m/s

Area required = 4.74/.8 = 5.925 m2

SWD provided = 0.7 mAt peak design velocity = 1.6 m/s

Assuming the screen bars are placed at 40° to thehorizontal.

Clear area = 4.74/ (1.6sin40) = 4.6 m2



Clear opening = 8 mm = 0.008 m

Net clear width of channel = 1.41 m

No. of clear openings = 4.6/.008 =575

No. of bars = 576Size of the bars = 50mm x 10 mm

Width of channel = (575 x 8) + (576 x 10) = 10360 mm=10.36 m

Fine screen is designed for the size of 10.36 m X 0.8 m(SWD) + 0.5 m (FB)



FINE SCREEN



GRIT CHAMBER

Grit removal basins are the sedimentation basins placed infront of the fine screen to remove the inorganic particleshaving specific gravity of 2.65 such as sand, gravel, grit,egg shells and other non-putrescible materials that may

clog channels or damage pumps due to abrasion and toprevent their accumulation in sludge digesters. The gritchamber is designed to scour the lighter organic particleswhile the heavier grit particles remain settled. Here the

horizontal flow type grit chamber is designed to give ahorizontal straight line flow velocity, which is kept constantover varying discharge.



DESIGN OF GRIT CHAMBER

Peak flow of sewage = 4.74 m3

/sAssume average liquid detention period = 3min. =180 s

So Aerated volume = 4.74 x 180

= 853.2 m3

In order to drain the channel periodically for routine cleaningand maintenance two chambers are used. Therefore volume ofone aerated chamber = 853.2 / 2=426.6 m3

Assume depth of 3m and Width to depth ratio 2:1

Width of the channel = 2 x 3 = 6 m

So Length of the channel = 426.6 / (3 x 6) = 23.7 m

Increase the length by about 20% to account for inlet and outlet

Provide length = 23.7 x 1.2 m = 28.44

Grit chamber is designed for the size of 28.44m X6m X 3m



GRIT CHAMBER



SKIMMING TANK

Skimming tanks are the tanks removing oils and greasefrom the sewage constructed before the sedimentationtanks. Municipal raw sewage contains oils, fats, waxes,soaps, fatty acids etc. The greasy and oily matter may form

unsightly and odorous scum on the surface of settling tanksor may interfere with the activated sludge process. Inskimming tank air is blown along with chlorine gas by airdiffuser placed at the bottom of the tank. The rising airtends to coagulate and solidify the grease and cause it to

rise to the top of the tank whereas chlorine destroys theprotective colloidal effect of protein, which holds the greasein emulsified form. The greasy materials are collected fromthe top of the tank and the collected are skimmed ofspecially designed mechanical equipments.



DESIGN OF SKIMMING TANK

The surface area required for the tank A=( 0.00622 × q) / Vr m2

Where

q = rate of flow sewage in m3 /day

Vr = minimum rising velocity of the oily material to be

removed in m/min

= .25 m /minute in most cases

q = 4.74 x 60 x 60 x24

= 410400 m3 /day

Vr = 0.25 m/min

= 0.25 x 60 x 24 = 360 m/day



A = (6.22 X 10-3 X 410400) / 360

A =7.09 m2

Provide the depth of the skimming tank is 3m.

The length breadth ratio is 1.5: 1Therefore L = 1.5 B

L x B = 1.5B2

Therefore B= 2.17m

L = 3.26 mSkimming tank is designed for the size of

3.26m X 2.17m X 3m + 0.5m (FB)



SKIMMING TANK



PRIMARY SEDIMENTATION TANK

Primary sedimentation tank is the settling tank constructednext to skimming tank to remove the organic solids whichare too heavy to be removed i.e. the particles having lessersize of 0.2 mm and specific gravity of 2.65. The designed

tank is circular type which makes settling by allowing radialflow. These are fabricated using carbon steel with epoxylining on the inside and epoxy coating on the outside. Builton the concept of inclined plate clarification, these clarifiers

use gravity in conjunction with the projected settling areaso as to effect a fairly high percentage of removal ofsuspended solids as 60 to 65% of the suspended solidsand 30 to 35% of the BOD from the sewage.



DESIGN OF SEDIMENTATION TANK

Max. quantity sewage = 136.88 MLD. It is intended toremove 60% to 70% of the organic particles of size largerthen .06mm. The settling velocity for such particals isabout 0.3 mm/sec. or 1.2 m/hr For affecting settlement

we haveQ / (BL) = (100/70)×1.2 m/hr ( for affecting 70% removel )

Or Q / (BL) = 1.7 m/hrOr Q / (BL) = 1.7 M3 /M2 plan area /hr

= 1700 liter /m2 of plan area / hr .= 1700×24 liters/m2 /day= 40800 liters /m2 /day



Similarly, for affecting 60 % removel, it can be calculatedthat Q / (BL) = 48,000 L/m 2 /day

Hence , surface loading adopted is about 40,000 L/m2 /dayto 50,000 L/m2 /day. Assuming the normal detention period

for such cases as 2 hr , and surface loading as 40,000liters /sq.m/day ; we have

The quantity of sewage to be treated per 2 hours

= 136.88 m.liters × (2/24 )

= 11.40 m.liters

= 11400 m3

So capacity of tank = 11400 m3



Now . surface loading =(Q/surface area of tank ) = (Q×4) / (d2× π)

40,000 = ( 136.88×106×4)/( π×d2 )Where d is dia . of pipe

d = 66.07 m Say d =67 mNow effective depth of tank= (capacity/ area of X-section )= (11400×4) / ( π×67×67)= 3.23 mSay 3.3 mHence , use a settling tank with 67 m dia. And 3.3 m waterdepth (with free board of 0.5 m extra depth.)

Primary sedimentation tank is designed for the dimensionof 67 m (dia.) X 3.3 m (depth) + 0.5 (FB)•

gautam project

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