Directory UMM :Data Elmu:jurnal:E:Environmental Management and Health:Vol08.Issue1.1997:

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Enviro nme ntal Manage me nt

Pro f. Dr-Ing., TU Be rlin, Be rlin, Ge rmany

Werner Hegemann

Christian M aschke

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two-Elke Ge ns c ho w, We rne r He ge mann and Chris tian Mas c hke Anae ro bic tre atme nt o f tanne ry waste wate r: to xic e ffe c ts o f waste wate r c o nstitue nts and do sage o f fe rric c hlo ride

Enviro nme ntal Manage me nt and He alth

8 / 1 [1 9 9 7 ] 2 8 –3 8

ga t h er ed on ce a w eek a s a r a n d om sa m p le fr om t h e efflu en t of t h e eq u a lizin g t a n k a n d u s ed a s feed for t h e exp er im en t a l p la n t . It w a s st or ed for s even t o 14 d ay s in t h e feed in g t a n k . In a ll in vest iga t ion s u n d ilu t ed t a n n er y w a s t e-w a t er e-w a s u s ed .

Analytical methods

T h e a n a ly s es of COD, ch lor id e (Cl–_{), a n d}

ch r om iu m (Cr_{t ot}) w er e ca r r ied ou t a ccor d in g t o DIN -s t a n d a r d s. An a ly ses of su lp h id e (S2–₎

a n d su lp h a t e (SO₄2–_{) w er e p er for m ed p h ot}

o-m et r ica lly, w it h coo-m p os it e s a o-m p les b ein g t a k en ea ch d ay for fi ve d ay s. Sa m p les of COD w er e a cid ifi ed a n d st ir r ed for h a lf a n h ou r t o d ecr ea se s u lp h id e.

Experimental operation

Fe Cl₃– do sage

FeCl₃w a s a d d ed in q u a n t it ies of 1gl–1_{a n d}

2gl–1_{in t h e in fl u en t t a n k . T h e ob ject ive w a s t o}

elim in a t e t h e su lp h id e a s FeS, b ot h in t h e for m exist en t in t h e r aw w a s t ew a t er a n d in t h e for m p r od u ced t h r ou gh t h e a n a er ob ic p r ocess.

PH value s

T h e va lu es of t h e t a n n er y w a s t ew a t er va r ied b et w een 8 a n d 12. For b iologica l t r ea t m en t it w a s n eces sa r y t o r e gu la t e t h e p H . T h e p H w a s a d ju s t ed t o 5, 6 or 7, d e p en d in g on t h e exp er i-m en t .

An a ly sis by m u lt ip le st a t ist ica l m et h od s (gr a d u a l a n a ly sis of cova r ia n ce)

T h ese w er e:

• N om in a l va r ia ble: q u a lit a t ive va r ia ble su ch a s t a n n er y (A, B, C).

• Qu a n t it a t ive va r ia ble m ea su r ed va lu e su ch a s COD va lu es (m gl–1_).

• Con fou n d er : p a r a m et er t h a t ca u s es u n in -t en -t ion a l va r ia n ce of -t h e d e p en d en -t va r i-a ble.

Figure 1

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Elke Ge ns c ho w,

Parameter Number M inimum M aximum SD M ean value

COD (mg l–1₎ _{4 6 7}a _{8 6 1} _{3 0 ,5 0 0} _{4 ,5 1 0} _{5 ,7 1 0}

a_{does not c orrespond to the number of samples taken from tanneries A, B and C}

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Elke Ge ns c ho w, We rne r He ge mann and Chris tian Mas c hke Anae ro bic tre atme nt o f tanne ry waste wate r: to xic e ffe c ts o f waste wate r c o nstitue nts and do sage o f fe rric c hlo ride

8 / 1 [1 9 9 7 ] 2 8 –3 8

t h e r a n ge b et w een 900 a n d 9,000g l–1_{. N ea r ly}

a ll va lu es (95 p er cen t ) a r e in t h e r e gion b et w een 900 a n d 15,000m g l–1_{. Seven t y -fi ve p er}

cen t of t h e va lu es for ch lor id e w er e fou n d t o b e b et w een 0 a n d 8,000m g l–1_{a n d 95 p er cen t of}

t h e va lu es lay b et w een 0 a n d 11,000m g l–1_{. As a}

con s eq u en ce COD va lu es h igh er t h a n

15,000m g l–1_{a n d ch lor id e va lu es > 11,000m g l}–1

n eed n ot be con sider ed for pr a ctica l oper a tion . Wit h t h e a b ove eq u a t ion , t h e est im a t ed ga s p r od u ct ion w it h m ea n feed fl ow (24.2 l) a n d m ea n con cen t r a t ion of COD (X–₁) a n d ch lor id e (X–₂) ca n b e d et er m in ed . E s t im a t es of ga s p r od u ct ion lay b et w een 120 a n d 50 l k g-1

CODo.

It r ea ch ed a m ea n va lu e of a b ou t 75 l k g-1 CODo

w h ich ca n b e ju d ged a s r a t h er low.

COD (X₁)

T h e d e p en d en ce of ga s volu m e (Y *) on COD con cen t r a t ion in t h e in fl u en t (X₁) w a s d et er -m in ed a s h av in g ver y h igh s t a t is t ica l r elia b il-it y (S > 99.9 p er cen t ). H igh er con cen t r a t ion s of COD cor r es p on d ed t o a n in cr ea se in ga s volu m e. E q u a t ion (5) w a s d et er m in ed w it h in t h e m ea s u r in g r a n ge of t h e con fou n d er a n d is va lid on ly for t h is r a n ge. Wit h m u lt ip le r e gr es sion it w a s p os s ible t o r ea ss u r e t h is w ell-k n ow n fa ct .

Chloride (X₂)

By m ea n s of m u lt ip le r e gr es s ion a con n ect ion w it h h igh st a t is t ica l r elia b ilit y (99.4 p er cen t ) b et w een ch lor id e con cen t r a t ion (X₂) a n d ga s p r od u ct ion w a s fou n d .

A gr a p h ic r e p r esen t a t ion w it h sim u lt a n eou s va r ia t ion of t h e t wo sign ifi ca n t con fou n d er s ca n n ot ser ve a s a cla r ify in g illu st r a t ion . On ly by k ee p in g on e con fou n d er con st a n t , ca n a gr a p h ic est im a t e fu n ct ion for t h e ot h er (0.0 < X₂< 12,800m g l–1_{ch lor id e) p r od u ce in t}

elligi-ble gr a p h ic r esu lt s. It is a dva n t a geou s t o u se t h e m ea n va lu e (X₁= 4,750 m g l–1_{) a s a con}

-s t a n t con fou n d er, b eca u -se it s t h e b e-st e-st i-m a t e. F igu r e 2 r e p r esen t s t h is set -u p.

Ch lor id e s h ow ed a n e ga t ive in fl u en ce on ga s p r od u ct ion (Y *), so t h a t on e ca n sp ea k of a n in h ib it or y effect . N o s u ch in fl u en ce of ch lor id e w a s fou n d on COD r em ova l.T h e in h ib it or y effect of ch lor id e on m et h a n e b a c-t er ia ca u sin g low er ga s p r od u cc-t ion w a s fou n d for con cen t r a t ion s > 10g l–1ch lor id e (t_R= 9 d ) in s y n t h et ic w a s t ew a t er [15]. Bu t a n in h ib -it or y effect h a s a lso b een d et ect ed for low er con cen t r a t ion s[16].

Wh y ga s p r od u ct ion is in h ib it ed w h ile COD r em ova l is n ot a ffect ed in t h is exp er im en t m ay b e exp la in ed a s follow s. On e p ossible exp la n a t ion lies in t h e in h ib it or y effect of ch lor id e on m et h a n e b a ct er ia , w h ich r ed u ce less COD a t h igh er con cen t r a t ion s of ch lor id e a n d t h u s p r od u ce sm a ller a m ou n t s of b io-ga s [16], w h ile t h e con cen t r a t ion of ch lor id e d oes n ot n e ga t ively a ffect t h e a ct iv it y of t h e su lp h a t e-r ed u cin g b a ct er ia . It is k n ow n t h a t som e su lp h a t e-r ed u cin g b a ct er ia r eq u ir e N a Cl con cen t r a t ion s b et w een 4 a n d 20 g l–1_[17]

or b et w een 0.5 a n d 5g l_–1[9]. T h e a m ou n t of con ver t ed or ga n ic m a t t er in su lp h a t e

Figure 2

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8 / 1 [1 9 9 7 ] 2 8 –3 8

Figure 4

Influe nc e o f s ulphate in the influe nt o n COD re mo val (multiple re gre s s io n)

Figure 3

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8 / 1 [1 9 9 7 ] 2 8 –3 8

t a n n er ies r e p r es en t n om in a l va r ia bles, m u lt i-p le r e gr es sion r eq u ir ed d u m m y cod in g, i. e., a t r a n s for m a t ion in t o q u a n t it a t ive en t it ies w it h a va lu e of “0” or “1”. Wit h t h is op er a t ion , t a n n er y B b eca m e sign ifi ca n t , so t h a t it w a s a t t r ibu t ed t h e n u m er ica l va lu e “1” in eq u a -t ion (6), w h ile -t a n n er ies A a n d C w er e a ccor d ed a “0”. On t h e b a sis of t h is cod in g a n d t h e m ea n va lu es for COD a n d su lp h a t e con cen t r a t ion s, COD d iffer en ces w er e 4,200m g l–1_{for t a n n er ies A a n d C, bu t on ly}

3,400m g l–1for t a n n er y B.

M a n y d iffer en t su b s t a n ces a r e u sed in lea t h er p r od u ct ion , so t h a t , even t h ou gh ch r om iu m -t a n n in g, lea t h er -p r od u cin g fa ct o-r ies in p o-r in cip le follow t h e Reu t lin geo-r m od el[19], b ot h t h e q u a n t it y a n d q u a lit y of t h e w a s t ew a t er d iffer con s id er a bly b et w een

fa ct or ies[20]. It is t h u s p la u s ible t h a t on e s h ou ld fi n d d iffer en ces in COD r em ova l. T h ese sign ifi ca n t d iffer en ces ca n b e t a k en a s a h in t t h a t fu r t h er s u b st a n ces in t a n n er y w a st ew a t er h ave a n in fl u en ce on t h e a n a er o-b ic p r ocess.

Analysis of variance

Pilo t plants

In t h e in vest iga t ion s, t h r ee s im ila r p ilot p la n t s w er e op er a t ed in p a r a llel w it h d iffer -en t op er a t ion a l p a r a m et er s. An a n a ly sis of va r ia n ce m a d e it p ossible t o t est t h e sim ila r i-t ies in i-t h e volu m e of ga s p r od u ced a n d in COD r em ova l. A sign ifi ca n t d iffer en ce b et w een t h e p ilot p la n t s w a s fou n d for COD r em ova l bu t n ot for ga s volu m e.

In F igu r e 5 t h e COD d iffer en ces (r aw a n d a d ju s t ed va lu es) a r e for ea ch p ilot p la n t . Wit h st a t ist ica l r elia b ilit y given a t S = 98.2 p er cen t for r aw va lu es a n d a t S = 99.6 p er cen t for es t im a t ed va lu es p ilot p la n t s va r ied sign ifi -ca n t ly. By a d ju st in g t h e m ea su r ed va lu es t h e va r ia n ce-a n a ly t ica l effect s r ea ch ed a h igh er d e gr ee of t r a n s fer a b ilit y t o ot h er ca ses. An a ly ses of va r ia n ce w er e ca r r ied ou t w it h t h e or igin a l m ea su r ed va lu es w it h ou t a d ju st -m en t , in or d er t o ch eck if t h e in fl u en ce of a t r ea t m en t h a d b een ob scu r ed by t h e a d ju st -m en t . How ever, n o su ch in fl u en ce w a s fou n d . Table III

Diffe re nc e s o f COD re mo val in the thre e tanne rie s (multiple re gre s s io n)

Tanneries A B C

Statistical reliability (%) 9 5 .3 9 5 .3 9 5 .3

Y* : COD difference (mg l–1₎ _{4 ,2 0 0} _{3 ,4 0 0} _{4 ,2 0 0}

COD removal (%)a 7 2 6 0 7 2

Note:

a_{With COD X}–

1= 5 ,7 1 0 mg/ l, sulphate X –

2= 1 ,1 8 0 mg/ l

Figure 5

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8 / 1 [1 9 9 7 ] 2 8 –3 8

In or d er t o eva lu a t e t h es e d iffer en ces w it h r e ga r d t o r eleva n ce for p r a ct ica l op er a t ion t h e es t im a t ed COD r em ova l of t h e t h r ee p ilot p la n t s is given for t h e m ea n va lu e of

COD = 5,710m g l–1_{. P ilot p la n t 1 r ea ch ed a}

COD r em ova l of 59 p er cen t , p ilot p la n t 2 a ch ieved a COD r em ova l of 65 p er cen t a n d p ilot p la n t 3 ob t a in ed t h e h igh est COD elim i-n a t ioi-n w it h 69 p er cei-n t for a d ju s t ed va lu es.

In a n a er ob ic t r ea t m en t p la n t s d iffer en t b iocen os es of b a ct er ia m ay est a blis h t h em -selves d e p en d in g on feed fl ow, d et en t ion t im e of w a s t ew a t er, t em p er a t u r e, a n d p H va lu e[21].

On ly a sign ifi ca n t d iffer en ce in COD r em ova l w a s fou n d , w h er ea s n on e cou ld b e d et er m in ed in ga s p r od u ct ion a n d d esu lp h u r iza -t ion . COD r em ova l is m a in ly ca u sed by -t h r ee p r ocess es: a cid ifi ca t ion , d esu lp h u r iza t ion a n d p r od u ct ion of m et h a n e. Su lp h a t e-r ed u c-in g b a ct er ia a n d m et h a n e b a ct er ia c-in t h e t h r ee p ilot p la n t s p r ob a bly d id n ot r ed u ce sign ifi ca n t ly d iffer en t a m ou n t s of COD, bu t t h e su m of COD r em ova l in a ll p r ocesses t oget h er w a s s ign ifi ca n t in t h e p ilot p la n t s.

Fe Cl₃

T h e d os a ge of fer r ic ch lor id e w a s in t en d ed t o elim in a t e s u lp h id e a n d t h u s t o p r even t it s in h ib it or y effect . Wh ile t h e d osa ge of FeCl₃ sh ow ed a sign ifi ca n t in fl u en ce on ga s p r od u c-t ion , n o s u ch in fl u en ce w a s n oc-t ed on COD.

In or d er t o eva lu a t e t h e r es u lt s of t h e a n a ly -sis, st a t ist ica l r elia b ilit y a s w ell a s t h e over a ll r eleva n ce of t h e r esu lt s w a s con sid er ed (Ta ble IV). For r aw va lu es a n d for a d ju st ed va lu es t h e sa m e st a t ist ica l r elia b ilit y w a s fou n d (S = 99.9 p er cen t ).

A d osa ge of 2g l–1_{fer r ic ch lor id e r esu lt ed in}

a 40 p er cen t r ed u ct ion of ga s p r od u ct ion . E ven h a lf t h e a m ou n t of fer r ic ch lor id e effect ed a 34 p er cen t r ed u ct ion , a r esu lt w h ich m u st b e con s id er ed r eleva n t (F igu r e 6). Table IV

Influe nc e o f fe rric c hlo ride o n gas vo lume (analys is o f varianc e )

Ferric chloride dosage (g l–1₎ ₀ ₁ ₂ ₀ ₁ ₂

Volume of the gas Adjusted values Raw values

Statistical reliability (%) 9 9 .9 9 9 .9 9 9 .9 9 9 .9 9 9 .9 9 9 .9

Gas volume (1 week–1₎ _{1 4 .6} _{9 .7} _{8 .7} _{1 4 .3} _{6 .3} _{8 .8}

Gas production (1 kg–1 COD_o)a _{1 2 7} _{8 4 .3} _{7 5 .7} _{1 2 4} _{5 4 .8} _{7 6 .5}

Gas volume (%)b _{1 0 0} _{6 6} _{6 0} _{1 0 0} _{4 4} _{6 2}

Notes:

a_{with mean value of COD}

o= 4 ,7 5 0 mg l–1, feed flow = 2 4 .2 1 week–1 b_{related to 0 g l}–1_{= 1 0 0 per c ent}

Figure 6

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8 / 1 [1 9 9 7 ] 2 8 –3 8

14 Gen sch ow, E ., “An a er ob e Rein igu n g von Ger b er eia bw ä sser n – Au sw er t u n g m it k om p lexen st a t ist isch en M et h od en ” (An a er ob ic t r ea t m en t of t a n n er y w a s t ew a t er – u t iliza t ion w it h com plex statistica l m eth ods), Disser -ta tion , Ber ich te zu r Sied lu n gsw a s s er w ir t s ch a ft 2, Ber lin .

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B ergey’s M a n u a l, Sect ion 7, 1981, p p. 663-79.

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