settling tanks ppt (2)

8/20/2019 Settling Tanks Ppt (2)

1/33

SETTLING TANKSSETTLING TANKS


2/33

• THEORY

• OPERATION

• DESIGN


3/33

THEORY

• Also referred as ‘SEDIMENTATION TANKS’.

• Settling- process by !"c! par#"c$la#es se##le #o #!e bo##o% ofa l"&$"d a'd for% a sed"%e'#.

• Par#"cles e(per"e'ce a force) e"#!er d$e #o *ra+"#y or d$e #o

ce'#r"f$*al %o#"o', #e'd #o %o+e "' a $'"for% %a''er "' #!ed"rec#"o' e(er#ed by #!a# force.

• Gra+"#y se##l"'*- #!e par#"cles "ll #e'd #o fall #o #!e bo##o% of#!e +essel) for%"'* a sl$rry a# #!e +essel base.

• or d"l$#e par#"cle sol$#"o's) #o %a"' forces e'ac#"'* $po'

par#"cle. Pr"%ary force "s a' appl"ed force) s$c! as *ra+"#y) a'da dra* force #!a# "s d$e #o #!e %o#"o' of #!e par#"cle #!ro$*!#!e fl$"d. T!e appl"ed force "s 'o# affec#ed by #!e par#"cle/s+eloc"#y, #!e dra* force "s a f$'c#"o' of #!e par#"cle +eloc"#y.


4/33

Se##l"'* or Sed"%e'#a#"o'

• Se##l"'*- a $'"# opera#"o' "' !"c! sol"ds are dra' #oard aso$rce of a##rac#"o'. T!e par#"c$lar #ype of se##l"'* #!a# "ll be

d"sc$ssed "' #!"s sec#"o' "s *ra+"#a#"o'al se##l"'*. I# s!o$ld be

'o#ed #!a# se##l"'* "s d"ffere'# fro% sed"%e'#a#"o'.

• Sed"%e'#a#"o'- T!e co'd"#"o' !ereby #!e sol"ds are already a##!e bo##o% a'd "' #!e process of sed"%e'#"'*. Se##l"'* "s 'o# ye#

sed"%e'#"'*) b$# #!e par#"cles are fall"'* do' #!e a#er col$%'

"' respo'se #o *ra+"#y. Of co$rse) as soo' as #!e sol"ds reac! #!e bo##o%) #!ey be*"' sed"%e'#"'*. I' #!e p!ys"cal #rea#%e'# of

a#er a'd as#ea#er) se##l"'* "s 'or%ally carr"ed o$# "' se##l"'* or

sed"%e'#a#"o' bas"'s.


5/33

Recirculating Aquaculture SystemsShort Course

Re%o+al Mec!a'"s%s

Gra+"#y separa#"o' Se##l"'* #a'0s) #$be se##lers a'd !ydro cyclo'es

"l#ra#"o' Scree') Gra'$lar %ed"a) or poro$s %ed"a f"l#er

lo#a#"o' oa% rac#"o'a#"o'


6/33


Se##l"'* 1as"'s

Ad+a'#a*es• S"%ples# #ec!'olo*"es

• 2"##le e'er*y "'p$#

• Rela#"+ely "'e(pe's"+e #o "'s#all a'd opera#e

• No spec"al"3ed opera#"o'al s0"lls• Eas"ly "'corpora#ed "'#o 'e or e("s#"'* fac"l"#"es

µ

ρ ρ

18

D )( g V

2

p p

s

−

=

Disadvantages• 2o !ydra$l"c load"'* ra#es

4 Poor re%o+al of s%all s$spe'ded sol"ds4 2ar*e floor space re&$"re%e'#s4 Re-s$spe's"o' of sol"ds a'd leec!"'*


7/33


Sol"ds P!ys"cal 5!arac#er"s#"cs

• par#"cle spec"f"c *ra+"#y

• par#"cle s"3e d"s#r"b$#"o'

Two most important physicalcharacteristics of suspended

solids:


8/33

DESIGNI' spec"fy"'* a a#er a'd as#ea#er sed"%e'#a#"o' #a'0 s"3e) #!e %a6or fea#$res #o be

co's"dered are7

- #a'0 cross sec#"o'al area)- #a'0 dep#!)a'd #ype of clea'"'* %ec!a'"s% $sed.

I' spec"fy"'* a des"*' bas"s for a#er a'd as#ea#er sed"%e'#a#"o' #a'0s, #!ree

co'd"#"o's are co%%o'ly co's"dered7

- sol"d !a'dl"'* capac"#y 80*9day:)- o+erflo ra#e 8lp%9%;:)- de#e'#"o' #"%e.

Add"#"o'al des"*' da#a re&$"red #o ascer#a"' %ec!a'"cal co's#r$c#"o') spec"f"c *ra+"#yof sol"ds) s"3e d"s#r"b$#"o' of sol"ds) $'derflo co's#r$c#"o') opera#"'* #e%pera#$re)

a'd *eo*rap!"cal loca#"o'. Typ"cal d"%e's"o's of sed"%e'#a#"o' #a'0s are *"+e' "'

Table


9/33


Sed"%e'#a#"o'

S#o0es 2a• De'ser a'd lar*e par#"cles !a+e a

!"*!er se##l"'* +eloc"#y

µ

ρ ρ

18

D )( g V

2

p p

s

−

=

µ

ρ ρ


10/33


Se##l"'* 1as"'s

•Des"*' #o %"'"%"3e #$rb$le'ce7

chamfered weirto enhance laminar ow

!"# of water depth$

full%widthweir

inlet outlet

e&ective settling 'one()* m

length:width + ,:( to !:(

sludge 'one


11/33


Se##l"'* 1as"'s

•O+erflo ra#es are $sed for des"*'7 >o

:8

:98;

?

marea surface settling

sm Rate Flow RateOverflow =

settling surface area + length - width

width

length

ow ow


12/33


Se##l"'* 1as"' Des"*'

"Rule of Thumb"Settling .asin Design

• /asin oor area of ,( 0pm per m* of ow1

• *"2 to ,(2 0pm per m width of weir for outow1

• su/merge inlet weir ("# of /asin water depth1

• use *" cm wide weirs and use rounded edges 1

• ma-imi'e length of settling cham/er as much as possi/le1


13/33

Settling Sedimentation$Settling Sedimentation$


14/33

Settling Tan3s4 .asins4 orClari5ers

Ge'erally) #o #ypes of sed"%e'#a#"o' bas"'s 8also called #a'0s) orclar"f"ers: are $sed7

Rec#a'*$lar a'd

5"rc$lar.

Rectangular settling, basins or clarifiers) are bas"'s #!a# arerec#a'*$lar "' pla's a'd cross sec#"o's. I' pla') #!e le'*#! %ay+ary fro% #o #o fo$r #"%es #!e "d#!.

T!e le'*#! %ay also +ary fro% #e' #o ;@ #"%es #!e dep#!. T!edep#! of #!e bas"' %ay +ary fro% ; #o %. T!e "'fl$e'# "s"'#rod$ced a# o'e e'd a'd alloed #o flo #!ro$*! #!e le'*#! of#!e clar"f"er #oard #!e o#!er e'd.


15/33

5"rc$lar 1as"'5"rc$lar 1as"' Rec#a'*$lar 1as"'Rec#a'*$lar 1as"'


16/33

1as"' Model1as"' Model


17/33

Se##l"'* ModelSe##l"'* Model

>s B se##l"'* +eloc"#y of #!e par#"cle

>l B !or"3o'#al +eloc"#y of l"&$"d flo


18/33

A par#"cle #!a# "s 6$s# re%o+ed !as a se##l"'* +eloc"#y +@.

T!"s #ra6ec#ory represe'#s a par#"cle !"c!

!as a se##l"'* +eloc"#y +@

+@ B ! 9 # B C 9 A

!ere7 # B >9C

A B s$rface area of #!e bas"'


19/33

Critical Settling 6elocity and 7veroCritical Settling 6elocity and 7verow

+@ e(pressed "' $'"#s of +eloc"#y 8f#9s: "s #!e cr"#"cal se##l"'*+eloc"#y

5r"#"cal se##l"'* +eloc"#y "s #!e se##l"'* +eloc"#y of par#"cles !"c! are


20/33

As yo$ ca' see #!e o'ly d"ffere'ce be#ee' #!e cr"#"cal se##l"'*

+eloc"#y a'd #!e o+erflo ra#e "s #!e #ype of $'"# $sed #o e(press

#!e '$%ber

T!e cr"#"cal se##l"'* +eloc"#y a'd #!e o+erflo ra#e are #!e sa%e

'$%ber) b$# proper $'"#s s!o$ld be $sed #o e(press eac!

S"'ce s%aller par#"cles !a+e loer se##l"'* +eloc"#"es) "f yo$ a'# #ore%o+e s%aller par#"cles "' #!e se##l"'* bas"' yo$ !a+e #o !a+e a

loer o+erflo ra#e.

S"'ce +@ B C9A) #o !a+e a s%aller +@ yo$ !a+e #o !a+e a lar*er area

8a b"**er bas"' re%o+es s%aller par#"cles:


21/33

Table 1 T!ical "i#ensions of Se$i#entation

Tan%s

______________________________________________________ "escri!tion "i#ensions

Range T!ical

&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&

Rectangular

"e!t', # ( ) (*)‑

Lengt', # 1) + ) .‑ ‑

/i$t', # ( . 0 1‑ ‑

ircular

"ia#eter, # . 0 1 .)‑ ‑

"e!t', # ( ) .*)‑

2otto# Slo!e, ##3# 0 10 4‑

&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&


22/33

8-ample (8-ample (

A a#er #rea#%e'# pla'# !as a flo ra#e of @. %A a#er #rea#%e'# pla'# !as a flo ra#e of @. % ??9sec. T!e se##l"'* bas"' a# #!e9sec. T!e se##l"'* bas"' a# #!e

pla'# !as a' effec#"+e se##l"'* +ol$%e #!a# "s ;@ % lo'*) ? % #all a'd % "de. pla'# !as a' effec#"+e se##l"'* +ol$%e #!a# "s ;@ % lo'*) ? % #all a'd % "de."ll par#"cles #!a# !a+e a se##l"'* +eloc"#y of @.@@F %9sec be co%ple#ely"ll par#"cles #!a# !a+e a se##l"'* +eloc"#y of @.@@F %9sec be co%ple#ely

re%o+ed If 'o#) !a# perce'# of #!e par#"cles "ll be re%o+edre%o+ed If 'o#) !a# perce'# of #!e par#"cles "ll be re%o+ed

++@@ B C9A B @. %9sec 9 8;@ % ( %: B @.@@ %9sec B C9A B @. %9sec 9 8;@ % ( %: B @.@@ %9sec

S"'ce +S"'ce +@@ "s *rea#er #!a' #!e se##l"'* +eloc"#y of #!e par#"cle of "'#eres#)"s *rea#er #!a' #!e se##l"'* +eloc"#y of #!e par#"cle of "'#eres#)

#!ey "ll#!ey "ll 'o#'o# be co%ple#ely re%o+ed. be co%ple#ely re%o+ed.

T!e perce'# of par#"cles !"c! "ll be re%o+ed %ay be fo$'d $s"'* #!eT!e perce'# of par#"cles !"c! "ll be re%o+ed %ay be fo$'d $s"'* #!e

follo"'* for%$la7follo"'* for%$la7

Perce'# re%o+ed B 8+Perce'# re%o+ed B 8+ p p 9 +9 +@@:


23/33

E(a%ple ;E(a%ple ;

Ho b"* o$ld #!e bas"' 'eed #o be #o re%o+e


24/33

E(a%ple ?


25/33


26/33


27/33


28/33


29/33

Sludge 'one

9 i d t h 4 9

0ength4 0

9ater 0evelarticle tra;ectory

Settling 'one

S l u d g e ' o n e

d e p t h


30/33

D

H

H0

0.5 m

Port 1 to 7

D= 15-20 cm

H= 2-4 m

H0= Design side water depth

E l


31/33

Example• 8-ample .atch Settling test results reduction analysis for sample port no1

(

• lot a grid showing percent TSS removal at each port at di&erent time

intervals

• Draw lines of equal # removal isoremoval$1 These lines are drawnsimilarly to contour lines1

• Draw vertical line at each point an iso removal line intersects the -%a-is>1" m depth$1 0ist the o/servations

Timemin

TSS remo!emg#l

Remo!al e$ciency %

2 *22 2 ?

(2 (>, @@ ?

*2 " (*" ?>2 "( (,B ?

,2 *2 (!2 ?


32/33

• Ob&er!ation&

• For example the R'()%

i&oremo!al cur!e intercept the x*axi& at +, minute&- The ()%&ettling time t i& therefore +, min-

• .)% of the particle& ha!e &ettle)-/0 m or more-

• ,)% of the particle& ha!e &ettle)-12 m or more

• 3i4e5i&e 1) % an ()% of theparticle& ha!e &ettle 0-)0 m an+-/) m or more re&pecti!ely-


33/33

Port6o-

7epthm

Sampling time min

(2 *2 >2 ,2 "2 @2 2 !2 B2

( 21" >> @* , B2

* (12 *( ,( @" ( !2 !B B2

> (1" (@ >@ "B @ , !( !@ B(

, *12 ( >> "@ @, ( ! !* !! B(

" *1" (, >* ", @, 2 ! !* !" !!

@ >12 (, >2 "* @> @B " !( !> !"

>1" (* >2 "( @2 @B , !2 !> !,

settling tanks ppt (2)

Documents