WW TREATMENT.pptx

8/18/2019 WW TREATMENT.pptx

1/45

Fundamental of Environmental

Engineering

Primary Treatment of Wastewater


2/45

2

Preliminary “Treatment”

• Equalization – Smooth out fluctuations in flow rate

– Results in more consistent treatment

• Flow Measurement – Flow rate information needed for efficient

oeration! chemical addition! etc


3/45

"

Equalization

• #$%ecti&e – 'ecrease fluctuations in flow rate! to ro&ide more

consistent treatment

•

(ccomlished $y storin) e*cess wastewaterdurin) hi)h flow eriods

• E*cess wastewater is released durin) low floweriods


4/45

+

Pumin)

• Sometimes needed to lift the water to a

hi)her ele&ation than the dischar)e oint

of the main trun, sewer line-

• (fter umin)! the lant is desi)ned to

oerate under )ra&ity flow to the oint of

dischar)e at the recei&in) stream-


5/45

.

( Screw

Pum


6/45

/

Flow Measurement

• #$%ecti&e – Measure flow rate to facilitate lant

oeration

• Se&eral oerations need flow rate datafor )ood oeration – 0hlorination

–

1 ad%ustment – (lso required for P'ES reorts


7/45

3

'esi)n of 4nfluent 0hannel

• #$%ecti&e – 'esi)n a com$ination of circular sewer and

rectan)ular channels to deli&er wastewater to the

head wor,s of the treatment lant

• (ly oen channel flow hydraulics 5

alyin) Mannin)6s equation considerin)7 – Minimum &elocity to reduce solids deosition in

the channel

– 1ydraulic )rade! sloe of channel in&ert to ro&ide

scour of solids

– 0hannel dimensions that match or transition the

influent circular sewer with a rectan)ular channel


8/45

Primary Treatment

8 'esi)ned to remo&e settlea$le solids and

reduce the or)anic load 9:#'; on thesecondary units-

- Primary treatment includes

8 :ar screen

8 0omminutor

8


9/45

Bar ScreenVendor-Provided Equipment

• Purose7 to remo&e lar)e o$%ects 9stic,s!

cans! etc; which may cause flow

o$structions-

• 'eendin) on the size of the lant! $ar

screens are either hand or mechanically

cleaned-

• 1and cleaned7 used rimarily at small

lants-


10/45

Fi)ure 9a; Manually cleaned $ar rac, 9from Pea&y! Rowe! and

Tcho$ano)lous! =>?.! - 2=?;


11/45

Bar Screen

Mechanically 0leaned• More frequently used $ecause la$or and

o&erflowin) are )reatly reduced-

• ( $y8ass channel with a hand cleaned $ar

screen must also $e ro&ided- ( secondmechanically cleaned $ar screen can also $ero&ided-

• The urose of the $y8ass channel is to

ro&ide treatment in case of a mechanicalfailure-• Screens are either front or $ac, cleaned-


12/45

=2

:ar Screen


13/45

Mechanical Bar Screen


14/45 9from Pea&y! Rowe! and Tcho$ano)lous! =>?.! - 2=>;


15/45



16/45



17/45

ComminutorsVendor-Provided Equipment

• Purose7 to cho solids $etween =@+ 8 "@? inchto re&ent ums from $ein) clo))ed-

• 0omminutors are installed directly into the

influent channel-• Since comminutors come in a standard size! it

is not unusual to select the comminutor first!

then size the channel-• 0omminutors should $e ro&ided with a

$y8ass channel and a hand cleaned $arscreen-


18/45

9from Pea&y! Rowe! and Tcho$ano)lous! =>?.! - 22A;


19/45

rit Cham!ers

• Purose7 to remo&e inor)anic material referred

to as )rit-


20/45

rit Cham!er


21/45

rit Cham!er


22/45

rit Cham!ersTyes

•

Square 0larifier 9'etritus Tan,;

• (erated Tan,s


23/45

rit Cham!er Square 0larifier 9'etritus Tan,;

• 'etritus tan,s are desi)ned so that thehorizontal &elocity is =-A fs at ma*imum

flow- This means that at low flow! the&elocity is less than =-A fs! and therefore!or)anic material will accumulate-

•

#r)anics are remo&ed $y counter currentwashin) as the )rit mo&es u an incline fordisosal-


24/45

9from Tcho$ano)lous and :urton! =>>=! - +./;


25/45

rit Cham!er Square 0larifier 9'etritus Tan,;

• :asic 'esi)n 0riteria

– Cs

H A-A3. fs B (&era)e Flow

– td D = min

– #&erflow rate7 +?!+AA )d@ft2

– Ch7 A-3.8=-2. fs 9,ees or)anics in

susension;


26/45

rit Cham!er (erated


27/45

9from Tcho$ano)lous and :urton! =>>=! - +/=;


28/45

"erated rit Cham!er :enefits of Pre8aeration

• :y ro&idin) reaeration! rimary treatment isimro&ed throu)h7 –


29/45

"erated rit Cham!er


30/45

Primary Clarifier

• Purose7 to remo&e settlea$le or)anics andfloatin) scum 9)rease and oils;-

• Efficiencies7 –

Susended solids .A 5 /. – :#' "A 5 ".

• Primary clarifiers are either circular orrectan)ular- They are &ery similar to

sedimentation $asins used in water treatmente*cet that scum remo&al is always ro&ided inaddition to slud)e collection-


31/45

"=

( 0ircular Primary Sedimentation

Tan,


32/45

"2

(n Emty Primary 0larifier


33/45

""

(n #eratin) Primary 0larifier


34/45

"+

#il S,immer in a Primary 0larifier


35/45

Primary Clarifiers'esi)n 0riteria

• Tye 44 Settlin) 0larifier7 durin) settlin) or)anic

solids come in contact with each other and

a))re)ate increasin) the article size and

settlin) rate- ())re)ation increases with time!therefore detention time is imortant-

• Td7 >A 5 =.A min at a&era)e flow 9(&) 2 hr;

• #&erflow rate7 /AA 5 =!2AA )d@ft2

• Weir loadin) rate7 =A!AAA 5 =.!AAA )d@ft-


36/45


37/45


38/45

"?

(erial Ciew 1ousatonic Wastewater Plant! Milford! 0T

9(&)- Flow Rate H ? M


39/45

">

(erial Ciew of :lue Plains Wastewater Treatment Plant!

Washin)ton '-0-

9a&)- flow rate H "A> Million )als@day;


40/45

Sludge #uantities

• uantity of slud)e collected in the rimary clarifier deends

on7 – Secific )ra&ity of the dry solids – moisture – Efficiency of settlin)

•

The followin) relationshi is used to determine the secific)ra&ity of the slud)e 9mi*ture of solids and water;7

S H S-


41/45

Sludge #uantities

•

The &olume of slud)e can $e determinedfrom the followin) relationshi7

S H secific )ra&ity of slud)e

C H slud)e &olume! )als

Ws H dry wei)ht of solids! l$

H secific wei)ht of water 9/2-+ l$ @ ft";

S S

Ws

S Pw

Ws

V

γ γ

=

−=

100

%

48.7

100

100

48.7

γ


42/45

9from Pea&y! Rowe! and Tcho$ano)lous! =>?.! - 22?;

Primar Treatment Efficienc


43/45

Primary Treatment Efficiency

• :#' H "A 5 ". SS H .A 5 /.

• Wastewater enterin) secondary treatment

Stron)7 :#' H 2/A52?A m)@G

SSH =2A5=3. m)@G

Medium7 :#'H =+.5=.. m)@G

SSH ?A5==A m)@G

Wea,7 :#'H 3A5?A m)@G

SSH ".5.A m)@G

Forms of :#'7 9a; 0olloidal

9$; Solu$le@'issol&ed

E* 'etermine the quantity of rimary slud)e er million


44/45

E*- 'etermine the quantity of rimary slud)e er million

)allons for domestic sewa)e with the followin)

characteristics7 SS H 2AA m)@G

Ss H =-+ moisture H >. Susended solids remo&al efficiency H /A

MG

gal

S s

Ws

V

S

Sw Pw

Ss Ps

S

lb M

Lmg MGlb Lmg MG M

EfficiencyQC M

sludge

sludge

sludge

237501.1*4.62*05.0

1000*48.7

)100/(%

48.7

01.1

99.00.195.0

4.105.0100/100/1

1000

6.0/*

34.8*/200*1

*

==+=

=

=+=+=

=

=

=

γ


45/45

References

• Pea&y! 1oward S-! Rowe! 'onald R-! andTcho$ano)lous! ?.;En&ironmental En)ineerin)- Mc=; WastewaterEn)ineerin) Treatment! 'isosal! andReuse- Metcalf and Eddy! 4nc- 4rwinMc

WW TREATMENT.pptx

Documents

Transcript of WW TREATMENT.pptx