treatment of edible oil and soap processing wastes

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Agricultural Wastes 8 (1983) 51-63

Treatment o f Edible Oi l and Soap Process ing Wastes

M . F . H a m o d a

Department of Civil Engineering,Kuw ait University, Kuw ait

A . H a n z a & S . S a a d

High Institute of Public H ealth, Alexandria University, Alexandria, Egypt

A B S T R A C T

Labora t ory ba t ch and con t hm ous - f l ow exper i m en t s w ere conduc t ed t o

s tudy the t reatment o f o i ly was tes us ing a sys tem compris ing di spersed

(di ffused) a i r f lo ta t ion and acti~,ated s ludge processes . Re mo val o f o i l

and Su. ipended Sol id s was eJJectirely acco mp lished b) , air f lota t ion ht

conjunct ion wi th chemical coagulat ion. Alu m was super ior to f er r ic

chlor ide and l ime, especial ly a t low doses . Acid( l i cation to p H 4, coupledwith dispersed air f lotat;o n, was alsa ef fect ive in oi l remo val bu t w as les~

ef fect ire in Suspended Sol ids reduct ion. The act ivated sludge protests

success fu l ly removed soluble organics and oi l s remaining af ter a i r

f lo ta t ion t reatment ond was not inhibi ted by the re la t i re ly h igh sal t

content o f the was te . Op; imu m resul ts were obtained at moderateO, low

organic loadings , sugges t ing the u .w oJ an e x tend ed aerat ion process .

I N T R O D U C T I O N

T h e d i s c h a r g e o f w a s te s c o n t a i n i n g o i l s i n t o w a t e r b o d i e s h a s r e c e i ve d

w o r l d w i d e a t te n t i o n i n r e c e n t y e a rs . I n E g y p t , t h e t w o l a r g e st e d i b l e oi l

p l a n ts , p r o d u c i n g n e a rl y o n e - t h i r d o f t h e g r o ss n a t i o n a l p r o d u c t i o n o f

o il s a n d h y d r o g e n a t e d f a t s , a re l o c a t e d i n t h e ci t y o f A l e x a n d r i a . T h e s e

a r e t h e S a l t a n d S o d a a n d t h e E x t r a c t e d O i l P l a n t s . B o t h d i s c h a r g e a b o u t

2 0 0 0 0 m 3 d a i l y o f h e a v il y p o l l u t e d w a s te s i n t o L a k e M a r u i t , l o c a t e d

s o u t h o f t h e c i t y , c a u s i n g i n t o l e r a b l e e n v i r o n m e n t a l a n d p u b l i c h e a l t h

h a z a r d s .

51

Agricultural Wastes 0141-4607/83/$03.00 ~'~ A pplied Science Publishers L td , Eng land,1983. Printed in G rea t Britain



52 M. F . Hamoda, A . Hanza , S . Saad

Thi s s t udy wa s i n i ti a t ed t o eva l ua t e t r ea t m en t o p t i ons o f t he o il y was t e s

and t o e s t ab l i s h t he i r t r ea t ab i l i t y pa ram et e r s . The e f f ec t s o f va r i ous

p r o p o s e d t r e a t m e n t c o n d i t i o n s o n t h e r e m o v a l o f o i l , a s w e ll a s S u s p e n d e dSo l i d s and o rgan i c m a t t e r , were s t ud i ed u s i ng a t r ea t m en t s y s t emcom pr i s i ng t he d i s pe rs ed a i r f l o ta t i on an d ac t i va t ed s ludge p roces ses .

In d i s pe r s ed a i r fl o t a ti on , gas bubb l es a re gen e ra t ed by i n t rod uc i n g t he

a i r t h r o u g h m e c h a n i c a l a g i t a t i o n o r b y s p a r g i n g a i r t h r o u g h p o r o u s

m e d i a . The p roces s p rod uces coa r s e r bobb l es t han d i s so l ved a i r f l o t a t ion

but con sum es cons idera b ly less ene rgy (Ram irez , 1979). Ai r f lo ta l. ion hasbeen u s ed t o a ss is t i n t he r em ova l o f o il and g reas e f rom dom es t i c sewage

(Lip tak , 1974) . Th e a dd ed d i f fused a i r pa r t ly de--emuls if ies the o i l and

grease and ass is ts their f lotat io~' t . I t has also been used as a clar i f icat ionan d/o r thic~ en ing p rocess fo r Su '~pende~:t So l ids rem oval . T he en t ra pm en to f ~ a s b u b b l. 's c a n b e p r o m o t e d b y t h e u s e o f c o a g u l a t i n g c h e m i c a l s w h i c hinc , ease the f loccu len t s t ruc ture of the f loa ted par t i c les and thereb y

fac i l it a te the cap tu re o f r i s ing gas bubb les (Zaj ic , 1971 ; Lu thy e t a l . ,

1978).

Aero b i c b i o l og ica l t r ea t m e n t o f was t ewa t e r s con t a i n i ng ed i b le o il s and

fa ts has been s uccess fu l (G urn ha m & N edve d , 1974 ; Yo ung , 1979) .However , t he i m pac t o f o i l . / m a t e r i a l s on t he ac t i va t ed s l udge p roces s

appea r s t o be dep end en t upo l ; ~he t ype o f o il and t he l oad i ng r a t e (EP A,

1971).

M A T E R IA L S A N D M E T H O D S

Was t ewa t e r s am p l es were co l l ec t ed da i l y f rom t he ed i b l e o i l r e f i ne ry .

L a b o r a t o r y e x p e r im e n t s w e r e c o n d u c t e d a t r o o m t e m p e r a t u r e ( 1 8--2 2 °C )us i ng f l o t a t i on and ac t i va t ed s l udge t r ea t m en t s y s t em s t o eva l ua t e t he

e ff ect e f d i f f e ren t t r ea t m en t c ond i t i ons on t he r em ova l o f o i l s ( f loa t ing ,

em u l s i fi ed , and s apon if i ed ), Sus pen ded So l id s and B O D.T h e e x p e r i m e n t a l p r o g r a m m e c o m p r i s e d p r e l i m i n a r y b a t c h e x p e r i -

m en t s on d i s pe r s ed a i r f l o t a t i on wi t h o r w i t hou t chem i ca l add i t i on .

B as ed on t he r e s u lt s o f the ba t ch s t ud ie s , t h ree phas es o f con t i nuou s f l owexper i m en t s were con duc t ed . Phas e I i nc l uded s ucces si ve s tages o f a i r

f l o t a t i on i n con j unc t i on wi t h ac i d i f i ca t i on a t pH 4 , neu t r a l i za t i on and

t hen ac t i va t ed s l udge t r ea t m en t . Phas es 1I and I I I i nvo lved a ir f l o ta t i on

i n c o n j u n c t i o n w i t h c h e m i c a l c o a g u l a t i o n u s in g 5 0 m g a n d 1 0 0 m g p e rl it e r o f a l um res pect ive l y , fo l lowed by ac t i va t ed s l udge t r ea t m e n t . Each



Treatment o . ]"e d i b l e o i l and s oap pr oc e s s i ng w as t e s 53

p h a s e o f t h e s t u d y i n c l u d e d t h r e e c o n s e c u t i v e s e ri es o f t h e e x p e r i m e n t s ,

c o n d u c t e d a t d i f f e r e n t h y d r a u l i c f l o w r a t e s , t o s t u d y t h e e f f e c t s o f

d e t e n t i o n t i m e o r w a s t e l o a d i n g o n t h e t e st e d p r o c e ss p e r f o r m a n c e .' r h e b a t c h s y s t e m c o n s i s t e d o f si x 2 0 -l it e r r e c t a n g u l a r j a r s f i tt e d w i t h

d i ff u s er s c o n n e c t e d t o a i r p u m p s . T e n l it e rs o f w a s t e w e r e p l a c e d i n e a c h

j a r . B a t c h f l o ta t i o n e x p e r i m e n t s w e r e c o n d u c t e d u s i n g a l u m , f e r ri c

c h l o ri d e a n d l im e a s c o n d i t i o n i n g a g e n t s a n d a c o n t r o l w a s r u n i n e a c h

c a se t o e x a m i n e t h e ef fe ct o f t h e a d d e d c o a g u l a n t s a n d t o d e t e r m i n e t h e

o p t i m u m d o s e o f e a c h c h e m i c a l u s e d . T h e e ff ec t o f p H a d j u s t rn e n t o n

d e s t a b i l iz a t i o n o f t h e o i l e m u l s i o n s w a s a l s o t e s t e d u s i n g H C 1 . T h e c o n t r o l

e x p e r i m e n t s r e p r e s e n t p l a i n f lo t a t i o n w h e r e a s t h o s e u s i n g c h e m i c a l s f o r

c o a g u l a t i o n o r a c i d i f i c a t i o n r e p r e s e n t c h e m i c a l f l o t a t i o n . W a s t e w a t e rs a m p l e s c o n t a i n i n g o i l a t c o n c e n t r a t i o n s r a n g i n g b e t w e e n 1 00 a n d

1000 m g l i te r - ~ we re use d .

T h e c o n t i n u o u s f lo w s y s t e m c o m p r i s e d a f l o ta t i o n -c l a r if i c a ti o n u n i t

fo l l o we d b y a n a c t i v a t e d s l u d g e u n i t ; b o t h w e re m a d e o f P le xig la s:i. T h e

f l o ta t i o n u n i t w a s 5 0 c m × 2 5 c m w i t h a l iq u i d d e p t h o f 6 0 c m . I t h a d t w o

i n t e r c o n n e c t e d c o m p a r t m e n t s o f e q u a l s iz e , o n e f o r c h e m i c a l t re a .'. m e nt

a n d t h e o t h e r f o r f l o t a ti o n . T h e l ev el o f l i q u id w a s a d j u s t e d f r o m t h e i n l et

t o t h e o u t l e t t o a l lo w c o n t i n u o u s w i t h d r a w a l o f f lo t a b l e m a t t e r fro~aa t h e

s u r f a c e t o a s i d e c h a n n e l a t t a c h e d t o t h e u n i t . C o m p r e s s e d a i r w a s

i n t r o d u c e d t o t h e f l ot a ti o, a u n i t a t a c o n s t a n t r a t e o f a b o u t 3 0 c m 3 r a i n -t h r o u g h p o r o u s d if fu s er s m o u n t e d n e a r t h e b o t t o m o f th e u n i t. C h e m i c a l

a d d i t i o n s f o r a c i d i f i c a t i o n ( H C I ) o r c o a g u l a t i o n ( a l u m s o l u t i o n ) w e r e

c o n t r o l le d b y p e r is ta lt ic p u m p s a d j u s t e d t o m a i n t a i n a p r e d e t e r m i n e d p H

o r a l u m d o s a g e . T h e i n f lu e n t f lo w t o t h e f l o t a t i o n u n i t w a s c o n t r o l l e d b y

p e r i s t a l t i c p u m p s a n d t h e c l a r i f i e d e f f l u e n t wa s d i s c h a rg e d b y g ra v i t y t o

t h e a c t i v a t e d s l u d g e u n i t .

T h e a c t i v a t e d s l u d g e a e r a t i o n - - s e d i m e n t a t i o n u n i t h a d t w o a d j a c e n t

c o m p a r t m e n t s w i t h a t o t a l l e n g th o f 1 2 0 c m ( 1 0 0 c m f o r a e r a t i o n a n d

2 0 c m f o r s e d i m e n t a t i o n ) , a w i d t h o f 2 5 c m a n d a l i q u id d e p t h o~" ~ i0 c m .T h e e f f lu e n t e n d c o m p a r t m e n t , u s e d f o r s e t tl i n g , w a s p a r t i a l ly s e p a r a t e d

f r o m t h e a e r a t i o n c o m p a r t m e n t b y a s l id i n g ba ff le a d j u s t e d t o l ea v e a s l o t

o p e n i n g a t t h e b o t t o m f o r t h e b a c k f lo w o f s e t tl e d ' r e t u r n s l u d g e ' .

C o m p r e s s e d ai r w as s u p p li e d a t t h e b o t t o m o f t h e a e ra t io n c o m p a r t m e n t

t h r o u g h p o r o u s a i r d i f f u s e r s .

O p e r a t i o n o f th e f l o t a ti o n a n d t h e a c t i v a t e d s l u d g e u n i t s w a s c o n t r o l l e d

b y a d j u s t i n g t h e i n fl u e n t f lo w r a t e t o o b t a i n h y d r a u l i c d e t e n t i o n t i m e s o f

3 to 7 . 5 h i n t h e f lo t a t i o n u n i t a n d c o r r e s p o n d i n g d e t e n t i o n t i m e s o f 12 t o



54 M. F. Hamoda, A, Hanza, S. Saad

30 h i n the ae ra t i on c om pa r t m en t o f t he ac t iva t ed s l udge un it . I n each cas e

t he un i t s were run co n t i nuou s l y t o r ea ch s t ab l e ( st eady - s ta t e ) con d i t i ons

be fo re r e s u l t s were r epo r t ed . C hem i ca l and phys i ca l ana l y s es o f t hewas t ewa t e r i n f l uen t and e f f l uen t o f each t r ea t m en t were pe r fo rm ed

a c c o r d i n g t o t h e Standard Methods Jor the Examination o f Water and

Wa.stewater (A PH A, 1975 ), whe reve r f easi b le .

R E S U L T S A N D D I S C U S S I O N

Wastewater character ist ics

The was t ewa t e r u s ed i n t he con t i nuous f l ow exper i m en t s was gene ra t edf rom t he E~ t r ac t ed Oi l C o m pa ny wh i ch s pec i al izes i n oi l hyd roge na t i on ,

s oap m anufac t u re and g l yce r i ne r e f i n i ng . The was t ewa t e r p roduced

contains reh~t ively high levels of saponif ied oi ls .

In t he m anu fac t u r i ng p roces s es , d i r ec t con t ac t o f wa t e r w i t h t he o il is

i nhe ren t s o t ha t , when t he p rodu c t s a r e pu r i fi ed , a d i r ec t tr an s fe r o f t he

i m pur i t ie s is m ade t o t he was t ewa t e r s t r eam t oge t he r w i t h add i t i ona l o i l -wa t e r em u l s i ons . O i l is was t ed t h ro ugh l eaks , sp il ls , c l ean -up , d ra i na ge o f

p i pes t o m ake r epa i r s and o t he r non -con t ro l l ab l e hous eho l d ope ra t i ons .

In add i t i on t o o i l s , l a rge am oun t s o f wa t e r - s o l ub l e com pl ex o rgan i cmater ia l s , o r ig ina l ly presen t in the raw o i l , f ind the i r way to the was te .

Tab l e 1 s um m ar i zes t he ave rage cha rac t e r is t i c s o f com pos i t e s am p l eso f ed i b l e o i l was t ewa t e r du r i ng t he phas es o f t h i s s t udy . Was t ewa t e r

cha rac t e r i s t i c s va r i ed s l i gh t l y du r i ng t he pe r i od o f s t udy bu t da i l y

v a r i a t i o n s w e r e m o d e r a t e c o m p a r e d w i t h o t h e r t y p e s o f i n d u s t r i a l

wa s tewa ters (Eck enfe ld er , 1970) . Ho we ver , d i scre te sz~.mples show ed awi de r r ange o f va l ues fo r p i t , conduc t i v i t y and s a l i n i t y o f 5 .5 -7 .6 ,3500 95 00 1m ah osc m ~ an d 1900---7000 ppm , respect ive ly . Th e ch lor ide

a n d s u l f a te c o n c e n t r a t io n s v a ri e d ; b e t w e e n 87 0 -2 0 0 0 m g l i t e r ~ a n d 1 7 0400 mg l i t e r " t respect ive ly . This ind ica tes th e re la t ive ly h igh sa l in i ty and

s a lt con t en t o f the r aw was t e . H i gh s a l in i ty is a t t r i bu t ed t o du m pi ng o f"sa l t ing ou t" was tes af ter a lka l ine ref in ing of ed ib le o i l and dumping ofconcen t r a t ed s a l t s o l u t i on du r i ng hyd rogena t i on by e l ec t ro l y s i s . TheTo t a l So l i d s and Sus pended So l i d s r anged be t ween 3010 and 7805m g

l it e r ~ and 417 and l l 00m gl i t e r - -~ , r e s pect ive l y . Th e ave rage vo l a ti le

por t ion of the To ta l So l ids wa s ab ou t 25 ', !o , wh ich reflec ts the h ighi no rgan i c s a l t con t en t o f t he was t e .



Treatment o f edible oil and soap processing wastes 55

6

o

i ' , 4

i

= ~ ~ , _ _

o 6 ~ 6 6 6 o 6 b

6 d



56 M. F. Hamoda, A. Hanza, S. Saad

T h e o il c o n t e n t o f th e r a w w a s t e w a s i n t h e r a n g e 1 4 5 - 9 6 0 m g li t e r -

T h e B O D v a l u es r e p o r t e d r a n g e d b e t w e e n 3 0 0 a n d 2 6 0 0 m g l it e r - ~. T h e

r a w w a s t e w a te r s h o w e d a n a v er a g e B O D s / C O D r a ti o o f 0 .6 , in d i ca ti n gt h a t t h e w a s t e i s f a i r l y b i o d e g r a d a b l e ( E c k e n f e l d e r , 1 9 7 0 ) .

Pre l i mi nary t e s t s

T h e r e s u lt s o b t a i n e d f r o m b a t c h t e st s o n t h e r e m o v a l o f p o l l u ta n t s f r o m

t h e o i l y w a s t e b y p l a i n d i s p e r s e d ( d i f fu s e d ) a ir f l o t a t i o n a r e s h o w n i n

T a b l e 2 . T h e m e a n o i l r e m o v a l w a s 4 5 ~ , w h i c h is r e l a t iv e l y l o w .

A c i d i f i c a t i o n o f t h e w a s t e i m p r o v e d o i l r e m o v a l b y t h i s p r o c e s s .

M a x i m u m r e m o v a l o f oi l w a s a c h i e v ed a t p H 3 , a s s h o w n i n F i g . I , a n d

a v e r a g e d 9 0'7 ,,, w i t h p a r a ll e l r e d u c t i o n s i n S S , B O D a n d T O C o f 8 4 " // o ,

5 0 ' /; a n d 4 9 '),;, r e s p e c t i v e l y . A c i d i f i c a t i o n t o t h i s p H s e e m s t o e l i m i n a t e

l h e s t r o n g n e g a t i v e c h a r g e o n t h e f r e e a c i d c a r b o x y l g r o u p s , r e s u l t i n g i n

a r e d u c t i o n o f s o l u b i l i ty a n d c o n s e q u e n t l y a b e t t e r c h a n c e f o r o il g l o b u l e

c o a l e s c e n c e a n d f l o t a ti o n . H o w e v e r . ac i d i f ic a t i o n t o p H 2 d i d n o t i m p r o v e

t h e o i l r e m o v a l e f f ic i en c y , a p p a r e n t l y d u e t o t h e r e v e r s e o f c h a r g e a n d

f o r m a t i o n o f a s t ab l e e m u l s i o n r a t h e r t h a n t h e se p a r a b l e o il .

A d d i t i o n o f a c h e m i c a l c o a g u l a n t ( e .g . a l u m , f e rr ic c h l o r i d e , l i m e )

i n c r e a s e d t h e r i s in g r a t e o f t to c c u l a t e d o i l d r o p l e t s d u r i n g d i s p e r s e d

a ir f l o ta t io n . O i l r e m o v a l s o f u p t o 9 7 % w e r e a c hi e v ed b y e a c h o f

TABI.E 2l']ticicncy of Plato D ispersed Air Flotation t No Ch cmical Addition)

lt'ast~,water c h a r a c t e r i s t i c s l i n g l i te r t ) R e m o c a l t f l t c i e m ' y { !,,)O i l .S'S'" ~ B O D ' ~ ~ 7()( ' " ' O i l S S B O D s T O ( "

;10 159 172 83 37 32 30 30150 178 183 98 27 25 32 31210 238 249 249 128 36 35 31

405 515 548 245 50 48 39 47420 618 789 258 36 32 28 30521) 721 683 358 46 42 40 44q~0 1173 1320 684 57 49 43 47960 1235 1320 682 58 43 42 48982 1305 1412 692 55 48 40 52

(a) Suspended Solids.(b) Biocl:emical Oxy den Dem and 15 daysL(c) To tal ,.)rganic carb on.



Treatment of edible oil and soap processing wastes 57

t he coagu l an t s i n con j unc t i on wi t h d i s pe r s ed a i r f l o t a t i on when h i gh

c o a g u l a n t d o s e s w e r e u se d , a s s h o w n i n F i g . 1. T h e c o r r e s p o n d i n g S S ,

B O D a n d T O C r e m o v a l s w e r e u p t o 9 5 % f o r b o t h a l u m a n d f e rr icch l o r i de , bu t were s l i gh t l y l ower i n t he cas e o f l i m e . In gene ra l , t hecoag u l an t s s t ud i ed p ro ved t o be e f f ect ive i n des t ab i li z i ng t he em u l s i f ied

o i ls a s we l l a s coa gu l a t i ng an d p rec i p i t a t i ng t he m a j o r i t y o f t he com pl ex

o rgan i c po l l u t an t s o f t he was t e . H ow ever , t he dos e o f a l um requ i r ed fo rt he e f fec ti ve r em ov a l o f po l l u t an t s w as foun d t o be ap p rec i ab l y l ower t hant ha t o f f e r ri c ch l o r i de o r l i m e . M oreov er , t he e f f luen t co l o ra t i on p rob l em

as s oc i a t ed w i t h t he app l i ca t i on o f h i gh f e r r ic ch l o r i de dos es , t he h and l i ng

and pH i nc reas e p rob l em s as s oc i a t ed w i t h t he u s e o f h igh l im e dos es , a s

we l l a s t he cons i de rab l e i nc reas e in s l udge p ro duc t i on and e f fl uen t s a ltcon t en t i n t hes e cas es , m ay a l s o f avou r t he u s e o f a l um a t l ower dos es .

The m u l t i p l e r eg res s i on t echn i que was app l i ed t o t he da t a ob t a i nedf rom t he va r i ous coagu l an t s t e s t ed i n t he d i s pe r s ed a i r f l o t a t i on ba t ch

P H V A L U E

,o o o , i / " / / , o o o.., ~ SOO

.,.j P"

~ 8 , o o / ~ b , , 4 b ' 6 b ' ~ . , o - -Z ' ° ° i ; o 6 0

°1° O iL RE MO VAL

( a ) A C I I J I F I C A T I O N

AL UM DOS e% -

7 0 R 0 9 0 10 0

°/ . O i L R E M O V A L

( b ) A L U M A D D I T I O N

F E R R IC C H L O R I D E D O b E ( m v I I ) L i M E D O SE ( m g l l )

0 0 0 - - - ,~ ,. , ,e ,n i 0 0 0 [o .

m ~00 $00

Z I 0 0 ~ ~ t - t ~ f O O Lso 6o 70 eo 90 Ioo so eo 70 ~ o ~ o ~6 o

% O I L R E M O V A L % O I L R E M O V A L

( C ) F E R R I C C H L O R | D E O A D D I T I O N ( b ) L I M E A D D I T I O N

Fig. I. Oil removal by chemicalflotation.



58 M. F. Hamoda, A. Hanza, S. Saad

s y s t e m a t d i f f e r e n t l e v e l s o f i n i t i a l o i l c o n t e n t i n t h e w a s t e . P r e d i c t i o n

m o d e l s w e r e d e v e l o p e d w h i c h r e l a t e d t h e o i l r e m o v a l p e r c e n t a g e ( Y ) t o

t h e i n i ti a l o i l c o n t e n t i n m i l l i g r a m s p e r l i te r ( X ~ ) a n d t o t h e d o s e o f a l u m ,f e r r i c c h l o r i d e o r l i m e , w h i c h e v e r w a s a p p l i c a b l e , i n m i l l i g r a m s p e r l i t e r

( X z ). T h e f o l l o w i n g m o d e l s w e r e o b t a i n e d w i t h a g o o d s t at is t ic a l f it t o t h e

d a t a , a s i n d i c a t e d b y t h e h i g h R 2 ( c o e f fi c ie n t o f d e t e r m i n a t i o n ) v a l u e i n

e a c h c a s e :

A l u m A d d i t i o n / A i r F l o t a t i o n :

Y = 7 8 . 6 3 0 - 0 . 0 1 5 X t + 0 , 0 8 3 X 2

F e r r i c C h l o r i d e A d d i t i o n / A i r F l o t a t i o n :

Y = 7 1 "7 2 7 - 0 . 0 1 3 X t + 0 . 0 5 8 X z

L i m e A d d i t i o n / A i r F l o t a t i o n :

Y = 7 1 . 3 18 - -0 . 01 4 X ~ + 0 . 0 7 I X 2

(R 2 = 0 .886)

(R 2 = 0 . 7 8 0 )

(R 2 = 0 .777)

C O N T I N U O U S - F L O W T E S T S

Dispersed air f lotat ion

T h e p e r f o r m a n c e o f c o n t i n u o u s f lo w d i s p e r s e d ( d if fu s e d ) a i r f lo t a ti o n i n

c o n j u n c t i o n w i t h a ci d if i c a ti o n w a s s t u d i e d i n P h a s e I e x p e r i m e n t s . B a s e d

o n t h e r e s u lt s o f p r e l i m i n a r y s t u d i e s , a c i d i f i c a t io n t o a p r a c t ic a l p H v a l u e

o f 4 w a s a d o p t e d in P h a s e I e x p e r i m e n t s . A l s o , d i s p e r s e d a ir f l o ta t i o n i n

c o n j u n c t i o n w i t h c h e m i c a l c o a g u l a t i o n w a s i n v e s t i g a te d u s i n g 50 m g a n d

100rag per l i t e r o f a lum in P hase s 11 an d 111 ex pe r im en t s , r espe c t ive ly .

T h e r e s u l ts o f P h a s e s I , 11 a n d I I I e x p e r i m e n t s a r e s u m m a r i z e d i n

T a b l e s 3 t o 5 . T h e s e r e s u l t s g e n e r a l l y c o n t i r m t h o s e o b t a i n e d i n t h e

p r e l i m i ~ a r y b a t c h e x p e r i m e n t s . A c i d i f i c a t i o n t o p H 4 a n d a i r f l o t a t i o nrem ov ed ab ou t 70" :;ii o f o i l (Ta b le 3 ). Th e overa l l e f l i c ienc i es o f SS an d

B O D r e m o v a l w e r e lo w if c o m p ~ r e d w i th o il r e m o v a l .

C h e m i c a l c o a g u l a t i o n u s i n g 5 0 m g p e r l i te r o f a l u m a n d a i r fl o t a t io n ,

s tud i ed in P has e I1 (Ta b le 4 ) , r esu l t e d i n ab ou t 85 ),~, o i l r emo va l , wh ich i s

h i g h e r t h a n o b t a i n e d i n P h a s e I. T h i s w a s a l so t r u e f o r S S a n d B O D

r e m o v a l s w h i c h w e re i m p r o v e d c o n s i d e r a b l y b e c a u s e o f a l u m c o a g u -

l a t i o n . B e t t e r r e m o v a l e f f i c i e n c i e s f o r o i l , S S a n d B O D w e r e o b t a i n e d

u s in g a h i gh e r a lu m d o s e ( 1 0 0 m g l i t e r ~) a s s h o w n i n T a b le 5. A l u m



T r e a t m e n t o f e d i b le o i l a n d s o a p p r o c e s si n g w a s t e s

T A B L E 3

S u m m a r y o f R e s u l t s ~ - P h a s e I E x p e r i m e n t s*

Tre atm ent Effluent characteristics ~a~ (m g l i t e r ~ l~emoval perc entag e (% )

p H T S S S V S B O D ~ O i l S S B O D s O i l

Ser i es I : A F 4~ 4 .8 5 6 5 5 3 6 0 9 9 0 2 2 2 8 5 5 5 .3 4 4 ,5 7 2 '7

A S ~ 6 .5 5 300 118 776 37 19 - - 83 ,3 77 .6

Ov era l l $ 5 .4 9 0 ,8 9 3 .9

Ser i es 2 : A F 4 ,5 5 1 2 1 4 5 0 9 3 5 1 99 7 5 5 2 .5 4 3 ,9 7 2 '0

AS 6 .4 4 9 8 4 1 42 7 9 2 3 8 19 - 8 0 ,9 7 4 .7

Ov era l l 8 5 .0 8 9 ,3 9 2 .9

Ser ie: ; 3 : A F 4 ,3 3 441 456 732 325 I0 6 48 .3 41 ,2 71 .2

AS 6 .2 3 327 166 575 77 30 - - 76 ,3 71 .7

Ov era l l 8 1 .2 8 6 ,0 9 1 .8

* A cic , i f ic a t i on a t p H 4 a n d d i s p e r s e d a i r f l o t a t io n f o l lo w e d b y a c t i v a t e d s l u d g e t r e a t m e n t ,

( a ) S e e T a b l e I fo r r a w w a s t e w a t e r c h a r a c t e r i s t ic s .

( b ) A F = a i r f l o t a ti o n .

I c) AS = ac t i v a t ed s lu d g e .

T A B I . E 4

S u m m a r y o f R e s u l t s P h a s e I1 E x p c r i n i e n t s *

Treatm ent l ' f fhwnt characteris t ics '" ' (rag l i ter - ' ) Rem ot 'al percentage s '~i,)

1711 "IS SS VS BOD S Oil SS BOD ~ t;i l

Ser ies I: AI : ' ' ' 6 .1 243 1 161 456 130 31 73.4 73.1 87.9

AS ~ 6 .3 I 997 52 375 19 7 85 .4 77 .4

Ov era l l 9 1 .4 9 6 . I 9 7 .3

Ser ies 2 : A F ~ ',.8 297 2 167 567 158 35 72 .6 72 '2 86 .9

AS (~.6 2411) 57 459 25 9 84.1 74'3Ov era l l 9 0 .7 9 5 .6 9 6 '6

Ser ies 3 : A F 6 .9 335 5 175 831 169 46 72 .1 71 .7 85 3

AS 7 .1 3311 61 784 29 12 - 82 .8 73 .9

Ov eral l 90 .2 95 . I 96 .2

* A d d i t i o n o f 5 0 r a g p e r l i t er o f a l u m a n d d i s p e r s e d a i r l l o t a ti o n f o l lo w e d b y a c t i v a t e d s l u d g e

t r e a t m e n t .

( a ) See Tab le I fo r r aw was t ew ate r ch arac t e r i s t i c s .

( b ) A F = a i r f lo t a t io n .

( c) AS .~ ac t i v a t ed s lu d g e .



6 0 M , F . H a m o d a , A . H a n z a , S . S a a d

T A B L E 5

S u m m a r y o f R e s u l t s - P h a s e 111 E x p e r i m e n t s *

Tre a tm e n t E f f lue n t c harac te r i s t i c s c ~ ( rag l i t e r - t ) Re m ora l pe rc e n tag e (% )

p H T S S S V S B O D 5 O i l S S B O D s O i l

Series 1 : A F ~b~ 6 .4 30 16 101 458 120 18 83 ,4 75 .0 92 ,2

AS~'~t 6 .5 241 8 36 292 7 4 - - 94 .2 I 77 ,8

Ov e ra l l 9 4 , I 9 8 .5 9 8 , 3

Y, r ies 2 : A F 7 .1 41 47 160 620 153 24 82 .0 73 .8 91 ,5

AS 7 .1 4 028 60 432 12 6 - 92 . I 75 ,0

Ov era l l 9 3 .3 9 7 .9 9 7 ,9

Ser ies 3 : A F 7 .1 5141 133 736 120 29 8 t .8 72 ,1 90 ,8

AS 7,1 46 07 51 667 11 8 ~- 90,8 72,4

Ov era l l 9 3 .0 9 7 .4 9 7 ,5

* A u d i t i o n o f 1 0 0 m g p e r l i te r o f a l u m a n d d i s p e r s e d a i r f l o ta t i o n f o l l o w e d b y a c t i v a te d s l u d g e

trei l tmel l l .( a ) S e e T a b l e 1 f o r r a w w a s t e w a t e r c h a r a c t e r i s ti c s .

( b ) A F = a i r f l o t a t io n .

( c) A S = a c t i v a t e d s l u d g e .

proved to be ef fec t ive in destab i l iz ing the emuls i f ied o i ls as wel l ascoagu la t ing and p rec ip i t a t ing the ma jo r i ty o f Suspended So l id s and

ccm plex o rgan ic po l lu tan t s o f the was te. How ever , r ecove ry o f reusab leoi ~, is som ew ha t difficult since the sep ara tion of oil f rom the c hem ical

s ludge : equires specia l t rea tm ent , e .g. su l fur ic ac id ad di t ion to re lease theo i l f rom the s ludge .

Like o ther c lar i f ica t ion processes , the d ispersed a i r f lo ta t ion processpe r fo rm ance i s af fec ted by the hyd rau l i c de ten t ion t ime . How ever , on lys l igh t improvem en ts were found a t longe r de ten t io n t imes , sugges t ing no

p rac ti ca l advan tage in inc reas ing the de ten t io n t ime beyon d 3 h . I t shou ld

be po in ted ou t , however , tha t the ado p t ion o f longe r de ten t ion t imes waspar t icu lar ly benef ic ia l in the case o f ac id i f ica t ion in conju nct io n wi th a i rf lo ta t ion , due to par t ia l neu tra l iza t ion of the t rea ted ef f luen t in the

f lo ta t ion tank .Tables 3 to 5 c lear ly show tha t d ispersed a i r f lo ta t ion was h igh ly

e f fec tive in o i l r emova l , e spec ia l ly when a lum coagu la t ion was u sed incon junc t ion w i th a i r f lo ta t ion . Th .e la t te r p roces s was a lso effec tive , bu t to

~ lesser ex ten t , in remo ving BO D . T his ca l ls fo r a subs eque nt b io log ica lt r e a t m e n t f o r t h e r e m o v a l o f t h e re m a i n i n g B O D . P e r h ap s a c o m b i n a t i o n

o f ac id i f i ca t ion to pH 3 , pH ad jus tmen t and a lum coagu la t ion in con -

junc t ion wi th d i spe r sed a i r f lo ta t ion cou ld be , a l though no t t e s t ed , abette~ ~ystem for co m ple te t re a tm ent of o i ly w~ts tes. Ho wev er , excess ive



Treatn en t o f ed ib le o i l and soap process ing wastes 61

chemica l t rea tme nt o f the was te could c ons ide rably increase it s inhere nt ly

high inorganic sa l t content .

Act ivated s ludge treatment

Th e resul ts obta ined f ro m the ac tiva ted s ludge uni t in P hases I , I I and I I Ia re presented in Tables 3 to 5 . These resul t s indica te tha t b io logica l

t rea tment would be an e ffec t ive method for removal of BOI ' ) and oi l

r e ma in ing a f t e r d i spe rse d a i r f l o t a t i on t r e a tme n t . The h igh BO Dremovals obta ined demonst ra te tha t the was te i s fa i r ly b iodegradable .

Th i s sup por t s r e c en t f i nd ings (G roe ne w old e t a l . , 1982) which sho w tha t

the b iod egradab i l i ty of edible o i ls is a lm ost twice tha t o f typica l mu nic ipa l

w a s t e w a te r a nd c ons ide ra b ly h ighe r t ha n tha t o f pe t ro l e um o i l s . N oa ppa r e n t t ox ic ity w a s de mon s t ra t e d by the re l a ti ve ly h igh sa l in i ty a ndinorganic sa l t content of the was te over the s tudy per iod. This i s in

agreem ent wi th the resul t s of Tok uz (1979) who repor ted tha t h igh sa l in i ty

wastes d id not a f fec t the performance of the ac t iva ted s ludge process .The hydraul ic de tent ion t imes employed in these exper iments (12 to

30 h) and M LSS conc ent ra t ion s ( 1530-2250 mg l i te r - 1) corresp ond ed toorga n ic l oa d ings (F :M ra t io ) be tw e e n 0 .12 a nd 0 . 6k g B O D 5 pe r kg

MLSS pe r da y , The pe r fo rma nc e o f t he a c t iva t e d s ludge p roc e ss w a s

affec ted by the org anic lo ading, as i l lus t ra ted in F~g. 2 . H igher loadingsresul ted in lower BOD and oi l removal efl ic iencies. Figure 2 defines anop t imu m loa d ing ra nge sugge s ting the use o f a n e x t e nde d a e ra t ion sys te mope ra t e d a t mo de ra t e ly l ow loa d ing (a bou t 0 .2 kg B O D 5 pe r M LSS pe rday) for the t ina l des ign of the ac t iva ted s ludge sys tem.

| o o

we r

m 8 O

o~

oJ 0 .1 0 ,1 or , 0 ,5 0 ,6 0 .7

K g B O D s / K g M L S S _ D A Y

Fig. 2. Effect of organ ic loadin g on B O D remo val by act ivated s ludge.



62 M. F. Hamoda, A. l tanza, S. Saad

A t t h e r a n g e o f l o a d i n g s s t u d i e d , t h e s lu d g e v o l u m e i n de x (S V I ) r a n g e d

b e t w e e n 6 0 a n d 8 7 m i l li li te r s p e r g r a m o f M L S S , w i t h t h e l o w e r v a l u e s

b e i n g f o u n d a t t h e l o w e r o r g a n i c l o a d i n g s . T h e s l u d g e s e t t l e a b i l i t ye v a l u a t e d b y 3 V I w a s g o o d , e s p e c i al ly i n P h a s e I I I i n w h i c h 1 0 0 m g p e r

i lt e r o f a l u m w a s u s e d i n t h e p r e c e d i n g a ir f l o t a t i o n t r e a t m e n t . I t is

a p p a r e n t t h a t a l u m c o a g u l a t i o n i n t h e f l o ta t io n t r e a t m e n t h a s a f a v o u r -

a b l e e f f e c t o n s l u d g e s e t t l e a b i l i t y i n t h e a c t i v a t e d s l u d g e s y s t e m . On

t h e o t h e r h a n d , t h e d i s s o l v e d o x y g e n c o n t e n t i n t h e a e r a t i o n t a n k w a s

c o n s i s t e n t l y h ig h e r t h a n 4 m g l it e r - 1. T h e c o n t a c t o f t h e w a s t e w i t h a i r i n

t h e f lo t a t i o n u n i t p r i o r t o a c t i v a t e d s l u d g e t r e a t m e n t c o n t r i b u t e d t o t h is

h i g h d i ss o l v e d o x y g e n c o n t e n t o f t h e w a s t e .

T h e r e s u l t s o b t a i n e d d e m o n s t r a t e d t h a t t h e a c t i v a t e d s l u d g e p r o c e s s

p e r f o r m a n c e w a s g o o d w h e n c o m p a r e d w i t h l i t e r a t u r e r e p o r t s ( E c k e n -

f e ld e r , 1 9 70 ) e v e n t h o u g h t h e w a s t e c o n t a i n s c o m p l e x o r g a n i c c o n s t i t u e n ts .

i t i s t h o u g h t t h a t o il s a p p l i e d t o t h e a c t i v a te d s l u d g e s y s t e m a r e s o r b e d

o n t o t h e b i o l o gi c a l f lo c s a n d t h e n d e g r a d e d . H o w e v e r , a t h i g h o i l l o a d i n g s

o i l m a y a c c u m u l a t e o n t h e s l u d g e , c a u s i n g a l o s s o f s l u d g e d e n s i t y al~..d

d e t e r i o r a t i o n o f s l u d g e s e t t li n g c h a r a c t e r is t ic s . W h e n w a s t e a c i d i fi c a t io n

is u s e d in c o n j u n c t i o n w i t h a i r f l o t a t i o n , wa s t e e f f l u e n t n e u t r a l i z a t i o n m a y

b~: r e q u i r e d p r i o r t o a c t i v a t e d s l u d g e t r e a t m e n t i n o rd e r t,~ p re s e rv e t h e

b ~Mferin g c a p a c i t y o f t h e a c t i v a t e d - s l u d g e s y s t e m .

T h e o v e r a ll p e r f o r m a n c e o f t h e d i s p e r s e d a i r f l ot a t io n - - ac t iv a t e d s lu d g es y s t e m , a s s h o w n i n Ta b l e s 3 , 4 a n d 5 , in d i c a t e s t h a t r e m o v a l s u p t o 9 8 '}i,,

96 '!,,; an d 94"~,; we re ach ieve d fo r o i l , B O D an d SS , resp ec t ive ly , whe n the

a lu m do sag e us ed w as ! 001T~g i t e r - ~(Ta b l e 5 ). Go o d e f f lu e n t q u a l i t y wa s

a l s o a t t a i n e d .

A C K N O W L E D G E M E N T S

T h i s in v e s t i g a ti o n w a s s u p p o r t e d b y U S E P A G r a n t N o . 3 -5 42 -4 . T h e

a u t h o r s g r a t e f u ll y a c k n o w l e d g e t h e a s s i s ta n c e o f t h e t e c h n i c a l s t a t t 'o f t h e

I n d u s t r i a l W a s t e R e s e a r c h L a b o r a t o r y a t t h e t t ig h I n s t i tu t e o f P u b l i cH e a h h . A l e x a n d r i a U n i v e r s i t y , A l e x a n d r i a .

R E F E R E N C E S

APHA (1975) . S t a n d a r d m e t h o d s ./ br c x a m i m t t i o n o f w a t e r a m l w a s te w a t e r.

AWWA, WPCF. (14 th edn . )t!ckcnfclder, W. W.. Jr. (1970). l l ' a t er q ual i t y e t tg im 'erotg . /or pra ct i s ing

eng i m ' e r s , Barnes & Noble, Inc. , New York.



Treatm ent o]" edible oil an d soa p processing wastes 63

EPA (1971) . The impact o f o i ly mater ia l s on act ivated s ludge sys tems , U SEnvi ronmen ta l P ro t ec t ion Agency , Water Po l lu t i on Con t ro l Research ,

Series 12050 DSH 03/71.Groe new old , J . C . , Pico , R. F , & W atson, K. S . (1982). Co m par ison o f BODrclat ionships for typical ed ib le and pet ro leu m oil s, Jour . W a;er Pol lu t ionControl Federat ion, 54, 398-405.

Gu rnha m , G , F . & Nedved , T . K . (1974). Trea t ab i l it y s tud i es o f t h ree foodprocess ing p lant wastewaters , Proe . 2 O t h Purdue Indus t r i a l Was t e

Conference , 283--93.Liptak , B. G. (1974) . Env i ronm en t a l Eng i neer s t t andbook , Vol. 1, Chil ton

Book Co . , Randor , Pennsy lvan ia .Lu thy, R. G., Sel leck, R. E. & Ga llow ay, T. R . (1978). Re m ova l o f emulsif ied oi l

wi th organic coagulan ts and d issolved ai r f lo tat ion , Jour . Wazer Pol lu t ion

Control Federat ion, 50, 331-46.Ram irez, E. R. (1979). Co m para t ive physicochem ical s tudy o f indust r ia l waste-

wa ter t reatm ent by e lect ro ly t ic , d i spersed ai r an d d issolved ai r f lo tat iontechnologies , Proc. 34th Purdue Indus ' tr ial Waste Conference, A n n A r b o rScience Publishers, 699--709.

Tokuz, R. Y. (1979) . The response of act ivated s ludge to h igh sal in i ty , Proc .3rd Turki sh G erman Ent ' i ronmental l~, )zgineer ing Sym pos ium , Vol . I ,Bogazici Universi ty , Civil E ngineer ing Dep ar tm ent , I s tanbul , T urkey .

You ng, J . C . (1979) . Rem o~,al of grease an d o il by b io logical t reatm entprocesses, . lout ' . Water Pol lut ion C~mtrol Fk,derat ion, 51, 2071-87.

Zajic, J . E. (1971). Water nol lutJon d~.sposal and reuse, Vol. 2, Marccl lDekker , Inc. , New York .

treatment of edible oil and soap processing wastes

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