Flocculator Design. Overview. Top View. Side View. Design Considerations. More Design Considerations 1/10/2017

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Pauline Hensley
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1/10/017 Flocculator sign Ovrviw Analysis of hydraulic flocculators Ratio of maximum to avrag nrgy dissipation rat

loss, collision potntial, rsidnc tim Gomtry of a baffl spac to obtain dsird nrgy dissipation rat Top Viw id Viw W =

flocculator channl = pac btwn baffls T = Thicknss of th baffls T B B =Prpndicular cntr to cntr distanc btwn baffls

5 L Port from prvious channl sign Considrations Th lngth of th flocculator channls matchs th lngth of th sdimntation

Human width Matrial limitations (polycarbonat or concrt) Vary to optimiz flocculation fficincy (function of gomtry)

AguaClara dsign (to kp chmical dos controllr nar stock tanks), but this may chang if flocculators gt smallr Evn or

1 1/10/017 Flocculator sign Ovrviw Analysis of hydraulic flocculators Ratio of maximum to avrag nrgy dissipation rat Infficincy of nrgy us du to nonuniformity of nrgy dissipation rat Th grat transition at =5 Flocculator sign Had loss, collision potntial, rsidnc tim Gomtry of a baffl spac to obtain dsird nrgy dissipation rat Top Viw id Viw W = Width of th flocculator channl = pac btwn baffls L = Lngth of a flocculator channl H = Watr dpth L = Lngth of th flocculator channl = pac btwn baffls T = Thicknss of th baffls T B B =Prpndicular cntr to cntr distanc btwn baffls Exit to th sdimntation tank ntranc channl Minimum watr lvl W 1.5 Uppr baffl H Lowr baffl L 1.5 L Port from prvious channl sign Considrations Th lngth of th flocculator channls matchs th lngth of th sdimntation tank Width of th flocculation channl? Minimum? Human width Matrial limitations (polycarbonat or concrt) Vary to optimiz flocculation fficincy (function of gomtry) Nd to dtrmin Had loss Rsidnc tim Baffl spacing Numbr of baffls Mor sign Considrations Evn numbr of channls for AguaClara dsign (to kp chmical dos controllr nar stock tanks), but this may chang if flocculators gt smallr Evn or odd numbr of baffls dpnding on channl inlt and outlt conditions Bgin with th nrgy sourc for th turbulnc that crats shar that crats collisions: had loss for a baffl CEE 4540: ustainabl Municipal rinking Watr Tratmnt Monro Wbr-hirk 1

1/10/017 Vna Contracta around a bnd? luic gat (almost closd)* 0.59 mall hol in a tank 0.6 Exit from a pip No Vna Contracta By Lindsay Lally, L Hixon (Own work) [CC BY-A.0 (http://crativcommons.

2 1/10/017 Vna Contracta around a bnd? luic gat (almost closd)* 0.59 mall hol in a tank 0.6 Exit from a pip No Vna Contracta By Lindsay Lally, L Hixon (Own work) [CC BY-A.0 ( or GFL ( via Wikimdia Commons * Robrson, JA; Cassidy, JJ; Chaudhry, MH. Hydraulic Enginring. John Wily. (1995) pag 17. Original rfrnc is Hnry, H.R. iffusion of ubmrgd Jts. iscussion by M.L. Albrston, Y.B. ai, R.A. Jnsn, and Hungr Rous, Trans. ACE, 115, (1950) Vna Contracta ( VC ) Conclusions raw th most xtrm stramlin through th transition and dtrmin th total chang in dirction If th chang in dirction for most of th fluid is 90, thn th VC is approximatly 0.6 If th chang in dirction for most of th fluid is 180, thn th VC is approximatly 0.6 =0.84 Had Loss cofficint for a Baffl Flocculator Efficincy Had loss in an xpansion - xpansion Which spac btwn baffls is bttr, considring th uniformity of th nrgy dissipation rat? th contraction cofficint for a sharp 180º bnd (0.6 ) W nd to masur this in on of th nw AguaClara plants! This spac with vry low nrgy dissipation rat dosn t contribut much = 4 = 10 Why a transition at of 5? Jts xpand in width at th rat of approximatly 1 unit in width pr 10 units forward Expansion lngth is 10(0.6) Expansion rquirs a distanc of approximatly 6 Th transition is rlatd to th distanc rquird for th jt to fully xpand implify flocculator dsign by dsigning for high fficincy Efficincy will b a function of th variability of th nrgy dissipation rat W xpct a rlation of th form such that fficincy is 1 whn =1 and fficincy is lss than 1 for highr valus of W solv this unknown by always dsigning fficint flocculators with <H/<6 CEE 4540: ustainabl Municipal rinking Watr Tratmnt Monro Wbr-hirk

1/10/017 Prior to 015 AguaClara usd dsigns that wr far from th optimum A compact plant layout was possibl for small flows by using a vrtical flow flocculator with a high ratio For small plants th

3 1/10/017 Prior to 015 AguaClara usd dsigns that wr far from th optimum A compact plant layout was possibl for small flows by using a vrtical flow flocculator with a high ratio For small plants th width of th channl was dtrmind by th nd to construct th channl using humans (45 cm or mor) Th spac btwn baffls was vry narrow and thus was vry high (for low flow plants) mall plants ndd longr rsidnc tim and mor baffls to achiv adquat flocculation bcaus fficincy was rducd. Nw Approach: Always fficint Add obstacls to hav a maximum ratio of btwn and 6. Flocculation fficincy can b considrd constant (and clos to 1) 0 L/s 10 L/s Viscous collisions or inrtial collisions Prior to 016 I had assumd that th appropriat lngth scal comparison was particl sparation distanc and Kolmogorov lngth scal thus concludd inrtia was important Particl sparation distancs ar smallr than innr viscous lngth scal Collisions in turbulnt flocculators ar dominatd by viscosity (fluid shar, not turbulnt ddis)* * Edg of knowldg 016 Collision Potntial Th targt collision potntial usd for th dsign of AguaClara plants sinc about 01 has bn 7,000 Th actual collision potntial in oprating AguaClara plants may b lowr bcaus th had loss pr baffl may b lowr than w assumd Enrgy us (had loss) in flocculation controls vlocity gradint Had loss High had loss rsults in a tallr building for th watr tratmnt plant High had loss mans highr vlocitis and that rducs sttling of flocs in th flocculator om gravity flow watr supplis don t hav much lvation diffrnc btwn sourc and storag tank Vlocity gradint (G) Highr allows lowr rsidnc tim Highr rsults in smallr flocs Th Influnc of or G Max Th valu of or dtrmins th had loss through th flocculator Maximum siz of th flocs is controlld by or (assuming shar limits attachmnt) G Max or Max (assuming floc brak up controls max siz) Not yt known Max = 10 mw/kg (G Max = 100 Hz) was th AguaClara standard ( ) ummr 015 nw dsigns hav had loss of approximatly 40 cm Expct smallr flocs (but still capturd by plat sttlrs) Lss sdimntation of flocs in flocculator mallr flocculator Casy Garland has tstd valus as high as 40 Hz CEE 4540: ustainabl Municipal rinking Watr Tratmnt Monro Wbr-hirk

1/10/017 Th dsign inputs for flocculation W nd collisions and thus G is a logical dsign spcification W nd to spcify nrgy us Vlocity gradint Enrgy dissipation rat Total had loss Or t () Mor tim hlps

had loss Had loss is indpndnt of tmpratur Vlocity gradint is f(tmpratur) Option 1 tart with (, ) and coldst tmpratur Calculat Calculat h Floc Option tart with (h Floc, ) and coldst tmpratur Currnt

4 1/10/017 Th dsign inputs for flocculation W nd collisions and thus G is a logical dsign spcification W nd to spcify nrgy us Vlocity gradint Enrgy dissipation rat Total had loss Or t () Mor tim hlps diffusion of coagulant nanoparticls to clay surfacs Highr G mans smallr flocs and mor lvation drop (had loss) through flocculator Currnt approach Our currnt choic of paramtr that sts nrgy input is had loss Had loss is indpndnt of tmpratur Vlocity gradint is f(tmpratur) Option 1 tart with (, ) and coldst tmpratur Calculat Calculat h Floc Option tart with (h Floc, ) and coldst tmpratur Currnt Calculat approach Calculat (and hnc )will incras whn th flocculator is opratd at warmr tmpraturs du to dcras in viscosity sign th ractor gomtry to gt th targt vlocity gradint Kintic nrgy dissipatd pr rsidnc tim Continuity Rctangular gomtry is hight of on xpansion zon. Could b th dpth of watr if th only xpansion is from th 180 dgr bnd This is our gnral quation rlating vlocity gradint to ractor gomtry W A olv for channl width to st constraints on viabl solutions This is th minimum channl width if w st = and st th xpansion hight to qual watr dpth Elvation viw As channl gts narrowr th spacing btwn baffls gts largr. Channls narrowr than this would hav barly any or ngativ baffl ovrlap! Minimum numbr of xpansions pr dpth of flocculator (givn W) Eliminat olv for maximum distanc btwn xpansions,, using = 6 Round up to gt th minimum numbr of xpansions pr dpth of th flocculator Our sign Approach Givn nrgy ( or ) and G tart big and thn dsign th dtails (AguaClara approach as of summr 015) Calculat volum of flocculator plit it into channls Thn dsign baffls, and obstacls to fill th channls to gt targt W can us this dsign approach bcaus w ar assuming that w will dsign for high fficincy (< <6) and thus w don t hav to add xtra volum to account for infficincis. (on t forgt this rquirmnt!) CEE 4540: ustainabl Municipal rinking Watr Tratmnt Monro Wbr-hirk 4

5 1/10/017 sign Algorithm (as of 016) tart with and G 1. Vlocity gradint and flocculator volum givn had loss and collision potntial. Minimum channl width rquird to achiv > and rquird for constructability. Numbr of channls by taking th total width and dividing by th minimum channl width (floor) 4. Channl width (total width ovr numbr of channls) 5. Maximum distanc btwn xpansions 6. Minimum numbr of xpansions pr baffl spac 7. Actual distanc btwn xpansions 8. Baffl spacing 9. Calculat th obstacl width to obtain th sam jt xpansion conditions as producd by th 180 dgr bnd Viscous Collision Potntial pr Flow Expansion (th dtaild prspctiv) Collision potntial for on flow xpansion Hight of on xpansion zon (in a vrtical flow flocculator) Hydraulic rsidnc tim for on xpansion zon Ths ar th avrag vlocitis through th xpandd flow ara Enrgy dissipation rat is nrgy loss pr tim Collision potntial is a function of vlocity. This suggsts that a flocculator would prform poorly if th flow rat wr dcrass. I don t know if anyon has vr dmonstratd that! Almost Ral signs (Flocculator xit dpth of m) What sts maximum channl width? What sts minimum channl width? Why this cycl of channl widths? Numbr of channls ht width Human hip Channl width (m) Maximum sign Minimum Flow rat (L/s) Why dos V incras with flow rat? Why dos V incras in stps? Why dos V rmain constant abov 70 L/s? Vlocity guidlins? Vlocity (m/s) Max (10 tat) Max (chulz) sign Min (10 tat) Min (chulz) Flow rat (L/s) sign caling (sign Engin vrsion 7099) 10 L/s 0.5 m wid channls 4. m long 0 L/s 0.55 m wid channls 5.90 m long 50 L/s 0.56 m wid channls 6.68 m long 70 L/s 0.7 m wid channls 7.7 m long Mor dtails Th ports btwn channls should hav th sam cross sctional ara as W Th numbr of chambrs pr canal (xcpt in th last canal) is vn th numbr of baffls is odd Th numbr of chambrs in th last canal is odd th numbr of baffls is vn Why? CEE 4540: ustainabl Municipal rinking Watr Tratmnt Monro Wbr-hirk 5

1/10/017 Us a with orifics to mak a flocculator for small flows (=) KV G H K G H 1 7 K HG V Continuity H H Hr w

xtra K orific Estimat th orific diamtr 1 vc Orific Orific vc K 1 orific W nd to stimat K!

orifics that ar clos to th innr diamtr of th pip Insufficint lngth for full xpansion bfor nxt orific xtra

diamtr to dvlop targt G V 16Q G H h K K g g 4gQ 4 Orific vc Rplac rsidnc tim with volum/q G H h 4gQ K orific 1

Hr w xtra An intrsting dsign No this wasn t AguaClara CEPI Horizontal Flow Flocculator CEE 4540: ustainabl

6 1/10/017 Us a with orifics to mak a flocculator for small flows (=) KV G H K G H 1 7 K HG V Continuity H H Hr w assum that is lik Round to narst innr pip diamtr? Or round down to gt highr vlocitis to prvnt sdimntation? xtra K orific Estimat th orific diamtr 1 vc Orific Orific vc K 1 orific W nd to stimat K! Th had loss for ths orifics spacd so closly may b lss than what w calculat Vna contracta may not b as svr for orifics that ar clos to th innr diamtr of th pip Insufficint lngth for full xpansion bfor nxt orific xtra Estimat th orific diamtr using th corrct valu of K H gh G 4ghQ G H H V h K g Nd to find actual K givn pip diamtr to dvlop targt G V 16Q G H h K K g g 4gQ 4 Orific vc Rplac rsidnc tim with volum/q G H h 4gQ K orific 1 7 G K Q HMax xtra Us a with orifics to mak a flocculator for small flows (H=) KV G H K G K G V Continuity H 1 7 Hr w assum that is lik Round to narst innr pip diamtr? Or round down to gt highr vlocitis to prvnt sdimntation? xtra An intrsting dsign No this wasn t AguaClara CEPI Horizontal Flow Flocculator CEE 4540: ustainabl Municipal rinking Watr Tratmnt Monro Wbr-hirk 6

7 1/10/017 A fw Rflctions Floc siz dosn t sm to b a significant constraint for flocculator dsign W may incras nrgy dissipation rat significantly as w xprimnt with maintaining small flocs that primary particls can attach to Our broad goal is to maximiz prformanc at minimum cost. Thus cost minimization may b an important constraint for stting th targt vlocity gradint. Maintaining th flocs in suspnsion is anothr important constraint max Rflction Qustions How dos th collision potntial in a flocculator chang with flow rat? What is th ratio of to for wll dsignd hydraulic flocculators? Why might mchanical flocculators brak mor flocs than hydraulic flocculators? Rflction Qustions Rflction Qustions What ar som altrnat gomtris? How ls could you gnrat had loss to crat collisions? What is th rlationship btwn potntial nrgy loss and th avrag vlocity gradint in a flocculator? How did AguaClara gt around th 45 cm limitation? How dos th non uniformity of (or G) influnc fficincy of nrgy us? Conclusions Enrgy dissipation rat dtrmins th spacing of th baffls. Enrgy is usd most fficintly to crat collisions whn th nrgy dissipation rat is uniform. Thrfor H/ btwn and 6 is bst. Collision potntial is a function of gomtry and a function of flow rat CEE 4540: ustainabl Municipal rinking Watr Tratmnt Monro Wbr-hirk 7

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