DOCTORAL DISSERTATION SERIES t it l e fACTOR.^ AFFECTING THE RATIOS I sm produced m m m DIGESTM OF SLUDGE_______ author M U AM CHARLES ALEGNAfU u n iv e rs ity DEGREE MRHIQAA STATF COLL (Lb. da te _ PUBLICATION NO.. m i|i[i|i i l i p i ’l ' ' I ' l ' M I ' I ' l 1 ' [ ' [ ' I TM UNIVERSITY MICROFILMS -L W ANN AMOR . MICHIGAN i F A C T O R S A F F E C T I N G T H E R A T I O S OF G A S E S P R O D U C E D D U R I N G THE D I G E S T I O N OF SLU DG E by W i l l i a m C. A l e g n a n i A DISSERTATION S u b m i t t e d to the S c h o o l of G r a d u a t e S t u d i e s of M i c h i g a n State C o l l e g e of A g r i c u l t u r e a n d A p p l i e d Science in p a r t i a l f u l f i l l m e n t of the r e q u i r e m e n t s f o r the de gr e e of DOCTOR OF PHILOSOPHY D e p a r t m e n t of B a c t e r i o l o g y a n d P u bl ic H e a l t h 1952 T o m y wire PEGGY w h o h a s inspired, me in m o m e n t s oP d e p r e s s i o n * this t he s i s is affectionately dedicated ACKNOWLEDGMENTS The w r i t e r w i s h e s to e x p r e s s h i s a p p r e c i a t i o n to Dr. W a l t e r L. M a l l m a n n T o r h i s advis e a n d e n c o u r a g e m e n t o f f e r e d d u r i n g the course of this study* A p p r e c i a t i o n is a l s o e x t e n d e d to Dr. H. J. Stafseth. f o r p r o o f - r e a d i n g the f i n a l d r a ft of this work* T h a n k s are a l s o e x t e n d e d to E d w i n E l l i s f o r t a ki n g the p i c t u r e s p r e s e n t e d in this thesis* William G . Alegnani c a n d i d a t e f o r the degree of D o c t o r of P h i l o s o p h y P i n a l e x a m i n a t i o n , S e p t e m b e r 22, Giltner Hall Dissertation: Outline Major Minor 1952, 9 :00 A- M . , R o o m 100 F a c t o r s a f f e c t i n g the r a t i o s of g a s e s p r o d u c e d d u r i n g the d i g e s t i o n of sludge of Studies: subject: subject: Bacteriology Biological Chemistry B i o g r a p h i c a l Items: Born: J a n u a r y 18, 1924, Springfield, I l l in oi s U n d e r g r a d u a t e S tudies: W a y n e Un iv er s it y, 1 943 (1 term) M i c h i g a n State College, 1943 (1 term) U n i v e r s i t y of Mis s ou ri , 1 9 4 3 (2 terms) W a y n e U n i v e r s i t y , 1946 - 1 9 4 8 B. A. June, 1948 Graduate Studies: M i c h i g a n State C o llege, 1948 - 1950 M. S. June, 1 95 0 M i c h i g a n State College, 1950 - 1952 Experiences: G r a d u a t e A s s i s t a n t in B a c t e r i o l o g y , State College, 1 9 4 8 — 1 952 Michigan Organizations: S i g m a Xi, S o c i e t y of A m e r i c a n B a c t e r i o l o g i s N a t i o n a l G e o g r a p h i c Society, U. S. A r m y M e d i c a l Rese rv e Corp. TABLE o f c o n t e n t s Page I N T R O D U C T I O N ............................................ Purpose of 1 study............................... 2 R E VI EW OF L I T E R A T U R E .................................. 3 C o m p o s i t i o n of sewage gas...................... 3 Synthetic detergents in s e w a g e . . . . . . . . . . . . . . . . . 6 Influence of o r g a n i c m a t t e r . • • • • • . . • • . • • • • • • • • • 8 iViaTmr(lAJu>S A N D MBf-iUDS. 11 S l u d g e s ............. 11 Synthetic detergents. .......... 11 C u l t u r e media. Bacterial c •••••• o Fermentation s u y n s M e t h o d of gas anal ys is . ... t t e s m . s ............. . 13 20 s l u d g e ..................... C a t i o n i c d e t e r g e n t s a n d sludge 12 15 AESuJ-.TS A N D D I S C U S S I O N .................... Raw and digested 12 d i g e s t i o n . ..... 20 24 D i r e c t e f f e c t of a c a t i o n i c a n d an a n i o n i c d e t e r g e n t . ........ 26 Gas r a t i o s at d i f f e r e n t Non-Ionic detergents E f f e c t of d e t e r g e n t s 27 a nd sludge d i g e s t i o n . ..••. 35 o n m i c r o f l o r a of 37 F a t t y a c i d s a n d sludge Tolerance i n t e r v a l s of time...... s l u d g e . .• d i g e s t i o n ................. of f a t t y a c i d s . ...... 40 42 TABLE OF CONTENTS (Cont.) Pag© C o n t a c t time and gas r a t i o s ...... 47 S U M M A R Y A N D C O N C L U S I O N S ................................... 53 R E F E R E N C E S ................................................... 54 LIST OF TABLES The r e l a t i o n s h i p b e t w e e n total gas p r o d u c t i o n a n d carbon dio xi de to m e t h a n e r a t i o s w h e n v a r i o u s a m o u n t s of raw sludge are a d d e d to dige sted s l u d g e .......... . . . ........ •••••••••••• 21 C a r b o n dioxide - m e t h a n e r a t i o s o b t a i n e d w h e n r a w sludge was a d d e d to d i g e st ed sludge... 22 The e f fe ct of a synthetic d e t e r g e n t (BTC) on the d i g e s t i o n of s l u d g e . .. .. ................ 25 The r a t i o s of c a r b o n dioxide to m e t h a n e p r o d u c e d w h e n v a r i ou s c o n c e n t r a t i o n s of s y n t he ti c d e t e r g e n t s are a d de d to dig e st ed s l u d g e ............................................ ;... 28 A c o m p a r a t i v e study of gas ratios a n d to tal gas p r o d u c t i o n over v a r i o u s periods of time w h e n d i f f e re nt c o n c e n t r a t i o n s of synthetic d e t e r g e n t are p r e s e n t . ......... ••••••••••••••••• 30 a) 500 m l of d i g e s t e d sludge 30 b) 400 m l of d i g es te d sludge / 50 m l of raw sludge / 50 m l of water. 30 c) 400 m l of d i g e s t e d sludge / 50 m l of raw sludge / 50 m l of BTC (final conc. 50 ppm).. 31 d) 400 m l of d i g e s t e d sludge / 50 m l of raw sludge / 50 m l of BTC (final conc. 100 ppm). 31 e) 4 0 0 ml of d i g e s t e d sludge / 50 m l of r a w sludge / 50 ml of BTC (final conc. 200 ppm). 32 f) 40 0 m l of d i g e s t e d sludge / 50 xul of raw sludge / 50 ml of BTC (final conc. 500 ppm). 32 The e f fe ct of d if ferent c o n c e n t r a t i o n s of s yn thetic d e t e r g e n t (BTC) on the total volume of gas p r o d u c e d by d i g e s t i n g s l u d g e . ........ 33 .LIST O F T A B jLaES (Cont.) Table 7. 8. 9. 10. 11. 12. Pag© The e f f e c t of a n o n - i o n i c sy nthetic d e t e r g e n t (Tr it on X-lOO) on the r a ti o of g a s e s w h e n a d d e d to d i g e s t i n g s l u d g e . ••••• The e f f e c t of d i f f e r e n t c o n c e n t r a t i o n s of s y n t h e t i c d e t e r g e n t s on the t o ta l gas p r o d u c t i o n , the r a t i o s of c a r b o n dioxide to m e t h a n e , a n d the colil'orm a n d g r a m positive miciococcus organisms when added to d i g e s t i n g s l u d g 36 e 39 The e f f e c t of d i f f e r e n t a m o u n t s of f a t t y a c i d s on the to tal gas p r o d u c t i o n , the r a t i o s of c a r b o n dio xi de to m e t h a n e , a n d the b a c t e r i a l c o u n t s w i t h r e s p e c t to the coliform and gram positive micrococcus g r o u p s w h e n a d d e d to d i g e s t i n g s l u d g e ...••••• The e f f e c t of v a r i o u s o r g a ni c c o m p o u n d s on the total gas production, the r a t i o s of c a r b o n d i o x i d e to meth an e, a nd the b a c t e r i a l c o u n t s w i t h r e s p e c t to the c o l i f o r m a n d g r a m p o s i t i v e m i c r o c o c c u s g r o u p s w h en a d d e d to dige st ing s l u d g 41 e 43 The e f f e c t of f a t t y a c i d s o n the total gas p ro d u c t i o n , the r a t i o s of c a r b o n d i o x i d e to m e t h a n e , a nd the b a c t e r i a l c o u n t s w i t h r e s p e c t to the c o l i f o r m a n d g r a m p o s i ti ve m i c r o c o c c u s g r o u p s w h e n a d d e d to aige sting s l u d g e ............. 45 The d i f f e r e n c e in c a r b o n dioxide m e t h a n e r a t i o s w h e n the g a s e s are left in c o n t a c t w i t h the d i g e s t i n g l i q u o r o v e r l o n g p e r i o d s of t i m e . .......... .••••••••• 49 a) sodium formate b) ol eic a c i d 50 L I S T OF F I G U R E S Figure I. Page F e r m e n t a t i o n a p p a r a t u s u s e d for the c o l l e c t i o n of g as of II. sludge d u r i n g the d i g e s t i o n ................... • • . • • • • •• •• • •• •• • G a s a n a l y s i s ao p a r a t u s . Burrell Build-up Model # 39-241..................... III. The e f f e c t of v a r i o u s 14 16 concentrations of BTC on the t o t al v o l u m e of gas produced by digesting sludge•••••••••••••••• 34 INTRODUCTION The u t i l i z a t i o n oi sewage gas h a s economical asset to m a n y c i ty gas Is u s e d T o r h e a t i n g m a i n t a i n i n g the and for sewage tlie olants temperature jroved to be an treatment in c o l d weather, of the a n a e r o b i c the o p e r a t i o n of gas e n g i n e s which, d y n a m o s f or the G r e a t Br itian, compressed p r o d u c t i o n of el e c t r i c i t y . reported sludge that, plants. The for digesters, in turn, Hurley run (24), in " d u r i n g the w a r quite a lot of gas w as u s e d as m o t o r f u e l f o r cars a nd p u b l i c l y own e d v e h i cl es . Some of it was u s e d f o r m a k i n g a p a r t i c u l a r l y d e v a s t a t i n g type of f ire bomb". p r o b a b l y the o nl y r e c o r d e d in stance a w e a p o n of war. ;yirts (45), of w aste d i g e s t e r gas, T h is is of sewage b e i n g u s e d as in r e g a r d to c o m m e r c i a l utilizati r e p o r t e d that "the cost of m e e t i n g the c o n d i t i o n i n g and p u r i f i c a t i o n r e q u i r e m e n t s f o r a u g m e n t i n g the gas u t i l i t y s up p l y w i t h w a st e d i g e s t e r gas w o u l d be of n o g a i n u n d e r p r e s e n t e c o n o m i c co nd it io ns ". A l t h o u g h the p r o d u c t i o n of sewage gas is n o t the p r i m a r y f u n c t i o n of a n a e r o b i c d i g e st i on , Its e c o n o m i c a l value and u s e f u l n e s s c a n n o t be overloo ke d. Influence m ore the p r o d u c t i o n of important. combustible of the noticeable shif t or state of the f a c t o r s w h i c h sewage gas are b e c o m i n g m or e In a d d i t i o n to this, to c o m b u s t i b l e pr ogress Thus, components the r a t io and of n on- serves as an inde x the d i g e s t i n g m a t e r i a l . A in the r a t i o s w i ll o f te n Indicate u n d e s i r a b l e c o n d i t i o n s a n d I m p r o p e r digestion. Purpose of study: The p u r p o s e or this of sev er a l f a c t o r s study w a s to d e t e r m i n e on the d i g e s t i o n of sludge. a t t e n t i o n w as p a i d to the t o t a l gas production, carbon dioxide with respect groups. to m e t h a n e p ro duced, Particular r a t i o s of a nd the b a c t e r i a l f l o r a to the c o l i f o r m a n d g r a m pos it iv e m i c r o c o c c u s S p e c i a l a t t e n t i o n was g i v e n to the detergents the ef fe c t (cationics, a t t e m p t w a s m ade anionics, to c o r r e l a t e production and specific sy n t h e t i c a nd n o n - i o n i c s ) . the r e l a t i o n s h i p b e t w e e n gas g r o u p s of m i c r o o r g a n i s m s . on the d e c o m p o s i t i o n of some An org an ic A study c o m p o u n d s a n d th eir e f f e c t on the m i c r o f l o r a of d i g e s t i n g sludge was a ls o c a r r i e d out. R E V I E W OF L I T F R a TUR E The p r i m a r y f u n c t i o n of a n a e r o b i c c o n v e r t the s o l id m a t e r i a l o b t a i n e d f r o m the p r i m a r y s e t t l i n g tanks i nt o an i nn o cuous, c o n v e r s i o n of this m a t e r i a l e a s i l y d r i e d residue. is d e p e n d e n t u p o n the a n d g r o w t h of n u m e r o u s m i c r o o r g a n i s m s . utilize the d i g e s t i o n is to r e s u l t f r o m the v a r i o u s The gases, f o r growth, w h i c h are produced, stag es of m i c r o b i a l m e t a b o l i s m . are p r o d u c e d f r o m the b r e a k d o w n of c a r b o h y d r a t e s , proteins. presence T h ese m i c r o o r g a n i s m s o r g a ni c m a t t e r w h i c h is present, r e p r o d u c t i o n and e nergy. The fats, Gases a nd D i f f e r e n t gases m a y be l i b e r a t e d f r o m the u t i l i z a t i of these v a r i o u s co m p o u n d s . the l i t e r a t u r e ares Some of the g a s e s r e p o r t e d in c a r b o n dioxide, hydrogen sulfide, n i t r o ge n, ammonia, a nd p h o s p h i n e . nitrous met ha n e, oxide, h y d r o ge n , nitric oxygen oxide, C a r b o n dio xi de a n d m e t h a n e are the two g a s e s f o u n d m o s t a b u n d a n t l y in sewage gas. C o m p o s i t i o n of s e wa ge g a s : In a study o n the c o m p o s i t i o n of sludge d i g e s t i o n gas t a k e n f r o m several d i f f e r e n t cities, that the p r i n c i p a l methane ingredients vary - 60 to 80 percent, Haseltine s o m e w ha t as follows: The gas u s u a l l y c o n t a i n e d detectable amounts and often measurable amounts oxygen. reported c a r b o n d i o xi d e - 10 to 30 percent, a n d n i t r o g e n - 1 to 15 percent. sulfide. (15) It m a y a l s o c o n t a i n of h y d r o g e n small a m o u n t s of h y d r o g e n or C a r b o n m o n o x i d e a n d i l l u m i n a n t s are s e l d o m present. He a ls o c o n c l u d e d th a t the d a l l y v a r i a t i o n s in the c o m p o s i t i o n fctie gas are as g r e a t as are Roberts sewage (30) in the q u a n t i t y of gas. a l s o tias p r e s e n t e d da t a on ttie v a r i a t i o n in gas f r o m d ig es te rs . Ttie p r e s e n c e gas. those of ph.osph.ine h a s b e e n r e p o r t e d i n sludge It was c l a i m e d that it o c c u r r e d d u r i n g the b a c t e r i a l r e d u c t i o n of o r g a n i c a nd i n o r g a n i c R u d o l f s a n d S t ah l (34), howe ve r , e x p e r i m e n t s in w h i c h v a r i o u s p h o s p h o r u s compounds. c a r r i e d out a series of org an ic a n d i n o r g a n i c c o m p o u n d s w ere a d d e d to d i g e s t i n g sludge. s t u d i e d gave qualitative the digesti on , t e s t s at v a r i o u s b u t none were phosphorus A l l of the c o m p o u n d stages d u r i n g c o n f i r m e d by q u a n t i t a t i v e tests w h e n the gas w a s o x i d i z e d w i t h c h l o r i n e a n d the p h o s p h o r u s d e t e r m i n e d as p h o s p h o m o l y b d a t e . that if p h o s o h i n e less was present It was in a c o n c e n t r a t i o n than the q u a n t i t a t i v e Eliassen, r e v i e w of sulfide Heller, of h y d r o g e n sulfide test c o u l d detect. a nd K i s c h the l i t e r a t u r e p ro d uc ti on . (12) A c c o r d i n g to the authors, the m e c h a n i s m s p r o d u c t i o n c o u l d be d i v i d e d into two the b i o c h e m i c a l rea c ti on s. source The m o s t the p r o d u c t i o n of h y d r o g e n sulfates. presented a comprehensiv on the m e c h a n i s m s of h y d r o g e n c l a s s e s a n d are c a t e g o r i z e d by the was They concluded of sulf ur f o r prevalent reaction sulfide b y the r e d u c t i o n of H y d r o g e n sulfide m a y a l s o be p r o d u c e d by the d e c o m p o s i t i o n of o r g an ic m a t t e r c o n t a i n i n g sulfur, p r o t e i n s a n d their d e r i v a t i v e s . Heukelekian Both Hotchkiss s uch as (23) (16) r e p o r t e d on the n u m b e r s of sulfate- and s p l i t t i n g o r g a n i s m s in sewage. Snell (36) s h ow e d a gas in a n a e r o b i c that organic n i t r o g e n was n o t lost as digestion, but that a b o u t 75 to 90 p e r c e nt was b r o k e n d o w n into a m m o n i a ni tr og en . that no ni tr og e n, n i t r o u s oxide, evolved unless nitrates He a l so r e p o r t e d or n i t r i c or n i t r i t e s were p r e s en t a n d then only in a q u a n t i t y e q u i v a l e n t to the w e i g h t Snell (35) oxide c o u l d be or n i t r i t e s ore sent. p r e s e n c e of n i t r o g e n gas r e p o r t e d in sludge of the n i t r a t e s a l s o s h o w e d t hat the d i g e s t i o n was f a lse a n d is a c c o u n t e d f o r b y i n f i l t r a t i o n of d i s o l v e d n i t r o g e n gas, by leaks, a l s o p o i n t e d out that o nl y a small and b y e r r o r s in gas analysis. since n i t r a t e s and n i t r i t e s c o n s t i tu te p e r c e n ta ge of the t o t al n i t r o g e n p r e s e n t in a c t i v a t e d sludge a n d are e n t i r e l y n e g l i g i b l e in sludge b y p l a i n s e d i m e n t a t i o n of sewage, n e e d n o t be One met ha n e, the a b ov e produced m e n t i o n e d gases c o n s i d e r e d important. of the f i r s t i m p o r t a n t existence He of me th an e, pieces of w o r k c o v e r i n g the the b i o l o g i c a l p r o c e s s e s w h i c h produce a nd the u t i l i z a t i o n or d i s a p p e a r a n c e of m e t h a n e by biological means was c a r r i e d out b y S o h n g e n (37). Since then n u m e r o u s i n v e s t i g a t i o n s on the m e c h a n i s m s of m e t h a n e f e r m e n t a t i o n h ave b e e n m a d e 39, 40, 41, 42). Walker (1, (44) 2, 3, 4, 7, 8, 9, 26, 37, 38, p r e se nt ed an e x c e l l e n t discussior on the p r i n c i p l e s of m e t h a n e p r o d u c t i o n in sludge digestion. He s t at ed t ha t in the e s t a b l i s h i n g of n o r m a l d i g e s t i o n the r a w sewage p a s se s t h r o u g h three stages as follows: p r o d u c t i o n or a c c u m u l a t i n g stage, 2) the 1) the a c i d slow a c i d d i g e s t i o n a n d r e g r e s s i o n stage, a n d 3) the a l k a li ne or m e t h a n e digestion stage. T h i s t h i r d stage m a y be c a l l e d the n o r m a l d i g e s t i o n stage. D u r i n g this third, the m e t h a n e b a c t e r i a m o r e a n d this stage stage or digestion, or less take c o n t r o l of the p r o c e s s c o n t i n u e s u n t i l n e a r l y all of the o r g a n i c m a t t e r is b r o k e n down. to con ti nu e or m e t h a n e T hi s d e s i r a b l e t h i r d stage can be m ad e i n d e f i n i t e l y in n o r m a l d i g e s t e r s p r o v i d i n g c e r t a i n c o n d i t i o n s are m a i n t a i n e d . H e u k ele kia n and H e i n em ann c o n t r i b u t e d to the w or k was (13, 19, a n d 20) have al s o study of m e t n a n e b a c t e r i a in sludge. Their p r i m a r i l y c o n c e r n e d w i t h the e n u m e r a t i o n of m e t h a n e - p r o d u c i n g b a c t e r i a in d i g e s t i n g solids, the e f f e c t of a d d i n g e n r i c h e d c u l t u r e s of me t h a n e - p r o d u c i n g b a c t e r i a in s u p e r n a t a n t liquors. S y n t h e t i c d e t e r g e n t s in s e w a g e : F o r an e x t e n s i v e the be use r e v i e w of the l i t e r a t u r e c o n c e r n i n g synthetic detergents, consulted. Since the work by G l a s s m a n (13) s ho u l d the a d v e n t of s y n t he ti c deterge n ts , the of soaps in h a r d w a t e r r e g i o n s h a s m a r k e d l y decreased. Consequently, syn th e ti c f o r ma n y i n t e r f e r e n c e s d e t e r g e n t s have b e e n h e l d r e s p o n s i b l e o c c u r r i n g in sewage t r e a tm e nt plants. A s y m p o s i u m on n e w p r o b l e m s in sewage t r e a t m e n t w i t h special r e f e r e n c e to synthetic Sewage W o r k s J o u r n a l p r e s e n t e d in five d e t e r g e n t s was p r e s e n t e d in the (14, 17, 21, 22, a n d 28). This w a s p a r t s and s h o w e d some of the d i f f i c u l t i e s e n c o u n t e r e d f r o m the use of these d etergents. In the t r e a t m e n t of sewage w a s te s, soaps h a v e n o t presented a problem because they are r e a d i l y p r e c i p i t a t e d b y the m i n e r a l c o n s t i t u e n t s (calcium, magnesium, a n d iron) n o r m a l l y f o u n d in the water* In this f o r m they are u t i l i z e d for food by the m i c r o o r g a n i s m s p r e s e n t (and gas production) in the d i g e s t i n g tanks. The s y n t h e t i c d e t e r ge nt s , are n o t a f f e c t e d by these m i n e r a l Goldthrope and Nixon (14), "the salts* physical association. a lso an I n h i b i t o r y i n f l u e n c e l o w e r the The As w a s s t a t e d b y surface a c t i v e a g e n t s d o n o t f o r m permanent chemical combinations, held however, but merely a loosely surface a c t iv e a g e n t s h ave on c e r t a i n ba ct e ri a. They surface t e n s i o n a n d may a f f e c t the t r a n s f e r of o x y g e n in a e r o b i c p r o c es se s. t e n s i o n a nd w il l b r i n g m o re the b a c t e r i a l Sperry T he y a f f e c t the i n t e r f a c i a l su b s t a n c e s to the i n t e rf ac e of c el l a n d w a t er ." (43) m e n t i o n e d t hat the pro ce ss of sludge d i g e s t i o n w a s n o t a f f e c t e d by s y n t he ti c detergents, b u t plant operating data that the v o l u m e seeme d to i n d i ca te of gas to be e x p e c t e d was d iminished. Rudolfs (33) d e t e r g e n t s to be 2) foa mi ng , s ho w e d the p r i n c i p a l e f f e c t s of the : 1) d e c r e a s e d e f f i c i e n c y of s e t t l i n g tanks; floe agglomeration, sludge units; syntheti a n d c arry o v e r in a c t i v a t e d 3) r e d u c t i o n in gas production. n o t e d that w i t h 100 p p m of N a c c o n o l N.R., He also the p e ak of daily gas p r o d u c t i o n w as r e a c h e d t w o d a y s e a r l i e r than w i t h o u t the de te rgent. Keefer* (25) i n v e s t i g a t e d the c o n t e n t of s y n t he t ic d e t e r g e n t s in r a w sewage a n d f o u n d that the r e m o v a l of d e t e r g e n t by p r i m a r y s e t t l i n g was a b o u t 14 perc en t. c o n c l u d e d that the c o n c e n t r a t i o n of d e t e r g e n t w a s that it w o u l d h a v e no d e t e r i m e n t a l e f f e c t He so small on the t r e a t m e n t proce s s . Eliassen (11) p r e s e n t e d an e x c e l l e n t a r t i c l e in w h i c h s yn thetic sewage d e t e r g e n t s red uc e on the m a n n e r the e f f i c i e n c y of sedimentation. D e g e n s a n d V a n der Zee (10) s h o w e d that me thane production w o u l d n o t be a f f e c t e d p r o v i d e d the c o n c e n t r a t i o n in the raw sludge of the sy n t h e t i c detergent Investigated was below 500 p p m of a c t iv e m a t e r ia l. I n f l u e n c e of orga ni c m a t t e r : An extensive particular l i t e r a t u r e has a p p e a r e d r e g a r d i n g this subject. This r e v i e w will be l i m i t e d to only a f e w a r t i c l e s p e r t a i n i n g to the u n d e r s t a n d i n g of this thesis. Buswell and Boruff (6) sho we d th a t the m e t h a n e content, as w e l l as the t o t a l gas p r o d u c e d in the a n a e r o b i c d e c o m p o s i t i o n of org an i c matter, C : H : 0 d e p e n d s on the ra tio of : N in the m a t e r i a l b e i n g dec om p os ed . Larson, Boruff, study of sludge and B u s w e l l digestion. (27) did a c a r b o n b a la nc e T h e i r d a t a i n d i c a t e d that the g r e a t e r p o r t i o n of the g a s f o r m e d d u r i n g sludge was due digestion to the d e c o m p o s i t i o n of f a t s a n d soaps. a c i d s a n d soaps, due to t h e i r l o w o x yg en content, The f a t t y furnished l a r g e r v o l u m e s a n d w e i g h t s of gas per u n i t w e i g h t of m a t e r i a l 9. digested. glycerol 4 They c i t e d as an exam pl e the f e r m e n t a t i o n of stearate: (Cl7 H 36 C 0 0 ) C 3H 5 / 106 H 2 0 65 C 0 2 / 163 CH4 E a c h g r a m of this f a t u p o n d i g e s t i o n f u r n i s h e d 1433 cc of gas w h i c h w e i g h e d 1 .54 gra ms a nd c o n t a i n e d 72 perc en t methane. The o ther c o n s t i t u e n t s f o u n d in sludge f u r n i s h e d lower v o l u m e s a n d less w e i g h t of gas per unit weig ht digested. Rudolfs (32) studied the eff ec ts of di ff er en t on sludge digestion. He sh ow e d that d i f f er en t solvents s olvents h a d v arious e f f e c t s on v olatile m a t t e r a n d gas proauction, and that the limits of tolerance w ere not the same. R u do lf s (31) showed that large qu an ti ti es of grease a d d e d to d i g e s t i n g m i x t u r e s m a y resul t in a r a p i d a c c u m u l a t i o n of f a t t y a c i ds (lower pH values). r et a r d the m e t h an e COg production. A c i d i c c o n d it i on s in turn p r o d u c i n g organisms, but do not affect He also show ed that soaps de c ompose at a r a p i d rate and are an e x c e l l e n t source q ua n t i t i e s of m i n e r a l oils (gasoline, of gas. Small crank case oil) did not m a t e r i a l l y a f f e c t the d i g e s t i o n process or the gas p r o d u c t i o n of se ed e d solids. Buswell (5) c l a s s i f i e d the s t a b l iz a ti on p ro cesses i n v o l v e d in sewage tr eatment into two simple types of r e a c ti o ns 1) aerobic: Og ----- COg / HgO / X CHX / HgO ----- C02 / CH4 / CHX / 2) Anaerobic: X C r e p r e s e n t e d carbon, H - hydrogen, and X - small a m o u n t s or othe r e l e m e n t s w h i c h m i g h t be present, r e p r e s e n t e d o r g a n i c matter. Thus, CHX 11. MATERIALS A N D METHODS Sludge a : Raw sludge or sewage, w a s o b t a i n e d f r o m tlie p r i m a r y s e t t l i n g tank of tlie E a s t L a n s i n g Sewage D i s p o s a l Plant. The m a t e r i a l was coll ec te d in two l i te r e r l e n m e y e r flasks. D i g e s t e d sludge w a s c o l l e c t e d f r o m the same plant. This m a t e r i a l came f r o m the a n a e r o b i c digester. The sludge was c o l l e c t e d in a 5 g a l l o n m i l k can a n d b r o u g h t to the l a b o r a t o r y f o r imm ed ia t e use. i n v e s t i g a t e d were The sludges collected between 9 : 00 and 1 0 : 0 0 A.M. o n the days w h e n e a c h e x p e r i m e n t w a s c a r r i e d out. Synthetic detergents: T h re e 1) s y n t h e t i c d e t e r g e n t s were u s e d in this study. A n i o n i c - N a c c o n o l N. R. S. F . - a l k y l a ry l sulfonate - N a t i o n a l A n i l i n e Go. It is u s e d principall as a d e t e r g e n t a n d w e t t i n g agent. Many of the c o m m o n h o u s e h o l d d e t e r g e n t s such as Tide, Dreft, Vel, Breeze, etc. belong to this group. 2) C a t i o n i c - BTC - a l k y l d i m e t h y l b e n z y l a m m o n i u m c h l o r i d e — O n y x Oil & Chem. Co. It Is u s e d p r i m a r i l y as a g e r m i c i d a l a g en t f o r s a n i t i z a t i o n purposes. 3) N on -ionic - T r i t o n X-100 - a l k y l at ed aryl poly ether alcohol - R o h m & H a a s Co, It Is us e d as a wetting, and e m u l s i r y i n g agent. detergent, It h a s applic at io ns in in secticides and agricultural industrial cleaners, textiles, sprays, paper processing, and other products. Culture m e d i a : Lactose broth, as re c o m m e n d e d by Standard Methods of W a t e r Analysis, was used for the d et er mi na t io n of the c o l i f o r m group. Dextrose azide b r ot h w a s u s e d for the en u m e r a t i o n of the gram positive micrococci. Bacterial count s: B o t h c o l i f o r m and g r a m positive mic r oc oc ci counts were d e t e r m i n e d by e m p l oy in g the three tube d i l u ti on technique. The counts tnroughout this ex p e r i m e n t are e x p r e s s e d in terms of the "Most Probable Number" lOO ml of sample. 35 C. (MPN) of organisms per All tubes were incubated at Final counts were made at the end of 48 hours. Fermentation systems: The app ar at us shown in Figure X was c o n s t r u c t e d in order to carry out the v a r i o u s fermentations. r i a s k s were used in the experiments. n e ve r e x c e e d e d 500 ml. The total in oc ul um Wh e n 500 ml f l a s k s were used, a he ad - sp ac e of a p p r o x i m a t e l y lOO ml, was e n c o u n t e r e d due One liter er le nm ey er allowing considerable difficulty to f r o t h i n g and subsequent e r u o t i o n of the d i g e s t i n g material. The 1 liter f l a s k s a l l o w e d f o r a h e a d - s p a c e of a p p r o x i m a t e l y 600 ml and el im inated these diff icultie s . A f t e r inoculation, collect in g columns the flas ks were c o n ne c te d to the gas (B) and f l u s he d w i t h nitrogen. Tank nitroge was u s e d and was p u r i fi ed by passing it through alkaline p yr og al lo l and c o n c e n t r a t e d sulfuric acid. t hrough the s i d e a r m of stopcock N i t r o g e n ente re d (W), passed thr ou gh the f e r m e n t a t i o n f l a s k into the sidearm of stopcock (X), and was expe ll ed into the surrounding atmosphere t h r ou gh stopcock •stThe d is placing l i qu i d in the gas collecting column was level w i th stopcock (Y). (Y). A p p r o x i m a t e l y 10 volumes of n itrogen was a l l o w e d to f lo w through the system in order to eliminate or displace the oxyg en present, conditions. and to e st ablish anaerobic The valve on the n i t r o g e n tank was closed, and ■» A n aqueous s olution contai ni ng 20 percent sodium sulfate by w e i g h t and 5 percent sulfuric a ci d by volume was used. A few drops of m e t h y l orange were added to facilitate reading and to indicate any change f r o m an ac i d to an alkaline condition. The indicator changes f r o m a pink to an orange at pH 5. Figu re 1. F e r m e n t a t i o n a p p a r a t u s used T o r the c o l l e c t i o n or gas d u r i n g the d i g e s t i o n of sludge* A - One l i t e r e r l e n m e y e r f l a sk B - Gas c o l l e c t i n g c o l u m n G - D i s p l a c i n g bottle (300 ml capacity) (500 m l capacity) D - C a l c i u m chloride tube c o n t a i n i n g M a g n e s i u m perchlorate and A s carite* to - T w o - w a y stopcock A a nd Y - T h r e e - w a y s t o p c oc ks rt 61 t I CD O m O X s topcock (W) was closed. Stopcock (Y) was a d j u s t e d so that the gases f o r m e d d u r in g the f e r m e n t a t i o n pro c es s w ould pass dire ct ly into the co l l e c t i n g column. The gas drawn over i mmediately a fter the collecting column was open ed to the f e r m e n t a t i o n flask, the was exp el le d t h r o u g h stopcock stopcock readjusted. The entire (Y), and system was then placed in a 35 C. inc ub at or for the aesired intervals. Samples of gas were stopcocks (A) and taken at various intervals by closing (Y) a n d disco nn ec ti ng tne f e r m e n t a t i o n f l a s k f r o m the co l l e c t i n g column. The gas was transferred to the gas anal ys er as de sc ri b ed in the next section. The c o l l e c t i n g c o l u m n was then r e a t t a c h e d to the f e r m e n t a t i o n systen The gas r e m a i n i n g in the c o l l e ct in g column was e xpelled t h r o ug h stopcock were (X). In this manner, atmospheric gases prevented f r o m e n t e r i n g the f e r m e n t a t i o n system durin g sampling periods. M e t h o d of gas a n a l y s i s : The m i x tu re of gases obtained in the f o l l o w i n g experiments was a n a l y s e d In the B u r r e l l Gas A n a l ys er shown in figure II. The procedure i n v ol ve d was as follows: C a r b o n dioxide was d e t e r m i n e d by ab so r pt io n in potassium hydroxide*. O x y g e n was d e t e r m i n e d by ab so rp ti on in alkaline py ro gallol • ■a- 50 % KOH - 1 m l absorbs 40 m l of carbon dioxide •H-ifr 5 gms pyrogallic a c i d disolved In 100 m l of 50 % KOH — 1 ml abs or b s 2 m l of oxygen figure II. G-as ana ly si s apparatus. B u r r el l B u i l a - u p jtioael # 39-241. Picture illustrates m e t ho d used to transfer gas f rom the co ll ec ti n g column to the burette the gas analyser. of H y d r o g e n was d e t e rm in e d by ox idation over copper oxide*. Methane was d e t e r m i n e d by oxi da ti on in the presence of catalyst**. N i t r o g e n was d e t e r m i n e d as the residual gas r em aining after the removal of all of the above gases. Prior to ea c h analysis the entire apparatus w i t h n i t r o g e n to remove atmospheric gases. was flushed The collecting column c o n t a i n i n g the gas to be a n a l ys ed was a t t a c h e d to the gas burette. stopcocks were a djusted so The that nitr og en passed t h r o u g h the m a n i f o l d system of the gas a n a l ys er and the s i d ea rm of the c ol lecting column into the atmosphere. A f te r flushing, the at mo s oh er e and the entire pressure. surrounding the stopcocks were closed to sys&em brought to atmospheric The gas in the collecting coiumn was then transferrec to the gas burette. e a c h analysis. One h u n d r e d In e ac h instance ml samples were used for the gas in the burette was brought to a tmospheric pressure by allowing the displacing l i q u i d in the l e v e l i n g bottle and the gas burette to come to the same level. M a n i f o l d stopcocks were adjusted to allow the gas to pass Into KOH. the first absorpt io n tube containing The gas was then drawn b ack into the gas burette. S ub sequent passages were made until a constant reading was o bt ai ne d in the gas burette. -* Readings were made by b ringing CuO tube h e a t e d to 300 G. Gas was allo w ed to pass through at a rate of 10 m l per minute. Reaction envolved. Ho / CuO — HgO / CU ** Catalyst tube H e a t e d to 500 C. The gas was all ow ed to pass through at a rate of 30 ml per minute. Reaction envolved. CH4 / 2 02 C 0 2/ 2 H 20 a ll of the gas b a c k I nt o the gas b u r e t t e stopcocks. The l i q u i d in the gas b u r e t t e a nd the b o t t l e w a s a d j u s t e d to the rec or d ed . l e v e l in g level a n d the f i n a l r e a d in g pyrogallol, seco n d a b s o r p t i o n a n d the above procedure The r e m a i n i n g gas w a s p a s s e d t h r o u g h the h e a t e d c o p p e r oxide For same The gas w as n e x t p a s s e d into the tube c o n t a i n i n g a l k a l i n e rep ea te d. and c l o s i n g the tube f o r the d e t e r m i n a t i o n of h y d r o g e n . the d e t e r m i n a t i o n of m e t h a n e a m e a s u r e d q u a n t i t y of the r e m a i n i n g gas w a s st or e d in the K O H or 50 m l d e p e n d i n g on the sample), tube and the r e m a i n d e r was e x p e l l e d i n t o the s u r r o u n d i n g a t mo sp he re . n e c e s s a r y f or the o x i d a t i o n of methane, a d d e d to the gas b u r e t t e (usually 30 Since o x y g e n is a g i v e n q u a n t i t y was to b r i n g the c o m b i n e d v o lu m e s t o r e d gas a n d the a d a e d gas to a t o ta l of 100 ml. m i x i n g of the s t o r e d gas a n d oxygen, heated catalyst tube. measured after each to ox i d a t i o n was passage u n t i l a c o n s t a n t r e a d i n g was The c a r b o n dio xi de p r o du ce d f r o m the o x i d a t i o n of m e t h a n e w a s a b s o r b e d into K OH and The C a r b o n dioxide Percent methane to o x i d a t i o n - — --a b s o r b e d ---------- — --- the f i n al p e r c e n t m e t h a n e was d e t e r m i n e d by f o l l o w i n g formula: C o n t r a c t i o n due After it w as p a s s e d t h r o u g h the The c o n t r a c t i o n due o b t a i n e d on the bu r et te . v o l u m e re corded. of the (r) / 3 (s ) (r ) (s) the The t o t a l a m o u n t of m e t h a n e present In the o r i g i n a l lOO m l sample w a s d e t e r m i n e d b y a simple proport i on . Nitrogen was the d e t e r m i n e d by s u b t r a c t i n g the total of a b o v e d e t e r m i n e d g a s es f r o m lOO. A r e c o r d was k e o t on e a c h r e a g e n t b e f o r e it lost its a b s o r b i n g The displacing liquid reservoirs was the same as so that it was r e p l a c e d qualities. u s e d in the gas b u r e t t e a n d gas that d e s c r i b e d f o r the gas c o l l e c t i n c o l u m n s in the f e r m e n t a t i o n system. 20. RkiSULiTS A N D D I S C U S S I O N H aw and d i g e s t e d s l u d g e ; A p r e l i m i n a r y e x p e r i m e n t was c a r r i e d out to d e t e rm in e what the c h a n g e s in c a r b o n d i o x i d e to m e t h a n e ratios would be w h e n i n c r e a s i n g a m o u n t s of r aw sludge were a d d e d to d i g e s t e d sludge. d esired, A mixture w h i c h would, in a short gas c o n t a i n i n g more me thane fermentation of r a w a n d d i g e s t e d sludge was systems were o e ri od of time, than c a r b o n dioxide. yield a Hour set up a n d i n o c u l a t e d as follows: Flask I - 500 m l of d i g e s t e d sludge F l a s k II - 4 5 0 m l of d i g e s t e d sludge / 50 m l of r a w sludge F l a s k III - 4 0 0 m l of d i g e s t e d sludge / 100 m l of raw sludge F l a s k IV 3 0 0 m l of d i g e s t e d sludge / 200 m l of raw sludge - F r o m the r e s u l t s ore sented in Table 1, t ha t a m a r k e d i n c r ea se when increasing amounts in the f l a s ks . sludge in the t o t a l gas p r o d u c t i o n o c c u r r e d of raw sludge were A l l the f l a s k s w h i c h were incorporated see de d w i t h raw s h o w e d a f a v o r e d m e t h a n e p r o d u c t i o n a f t e r 24 h o u r s of incubation. The r a t i o s of c a r b o n dioxide s h o w e d only results, Flask it was n o t e d s l ig ht v a r i a t i o n s . In o rder to c o n f i r m these III, a n d IV c o n t a i n e d the same q u a n t i t i e s of raw and digested sludge as in the a bove e x p e r i m e n t Flask V - 200 m l of d i g e s t e d F l a s k VI - 500 m l of r a w sludge obtained obtained, six f l a s k s w e r e a g a i n s e ed ed as follows: I, II, The to m e t h a n e results sludge / 300 m l of raw p r e s e n t e d In Table 2, in the f i r s t e x p e r i m e n t . s u p p o r t e d the sludge e vi de n c e It was noted, however. Table 1. The relationship between gas production and carbon dioxide - methane ra tio s when various amounts of raw sludge are added to digested sludge. X F la si * III II IV 5 23 43 6 29 46 7 27 47 9 30 49 95 ?4o 34o 130 3SO 430 225 545 735 290 690 i 0*K) 10.2 19. s 2.2 13.4 IS .5 SO 17.6 22.0 7.4 24.6 27.8 - 2 .0 0 2 .4 1.0 0 6.4 0 0 l.b 0 0 f: HO - 0.4 0 .4 0 0 0 0 0 0 9.0 0 0.2 0% - 5-7 24.4 1.5 21.7 37.1 7.6 32.9 35.4 S .5 33.6 27.3 - 31.1 44.6 93.9 63.9 44.4 31.0 49.3 42.6 73.5 41.3 44.7 Time In Hrs. TGP ** 7» 002 - CJ 0 i £ N2 1.89 C02 CHi| * Flask I II III IV 1 - 500 - 450 - 4oo - 300 ml ml ml ml of of of of 1 1.46 I .23 digested digested digested digested ** TOP - Total ml of gas produced l 1 1.62 1 2.00 1 1.52 1 1.36 sludge sludge / 50 ml of raw sludge sludge / 100 ml of raw sludge sludge / 200 ml of raw sludge 1 1.60 1 1.15 1 1.36 1.02 1 Table 2. Carbon dioxide - methane ra tio s obtained when raw sludge was added to digested sludge. Flask * IV III II 1 V VI Time In Hrs. 24 46 25 49 26 30 26 52 29 53 30 R4 TOP ** 135 235 590 570 650 1110 610 1160 530 950 230 ^60 ^ C 0o 4.6 11.0 20.2 23. s 21.0 29.4 26.4 34.6 26.2 43.6 17.5 0 U~\ o2 1.6 0.6 0 0 0 0 0 0 0 0 0 .4 0.2 0 0 0 0 0 0 0 0 0 0 0 0 1.3 6.2 0.9 11.2 35.9 49.3 36.6 32.5 26.2 46.7 15.6 32.2 5: n2 92.9 77.0 43.9 26.9 42.4 22.1 43.2 16.3 56.2 24.2 60.5 4 l.4 co2 3.11 1.61 1.35 13.7 9.64 ♦* Flask I II III IV V VI tgf 1 1.01 l * . ‘r h2 0/ - bOO ml 450 ml 400 ml 300 ml 200 ml 300 ml 1 1.77 1 2.07 1 1.74 of digested sludge of digested sludge of digested sludge of digested sludge of digested sludge of raw sludge _ Total mi of gas produced 1 2.06 / / / / 1 1.06 1 1.39 1 50 ^ oi raw sludge 100 ml of raw sludge 200 ml of raw sludge 300 ml of raw sludge 1 1 1 that w h e n the digested q u a n t i t y or r a w sludge e x c e e d e d the a m o u n t of sludge (Flask V), b o t h the total gas a n d the r a t i o or gases w e r e arrected. d e c r e a s e d and c a r b o n d i o x i d e p r o d uc ti o n Total gas production p r o d u c t i o n increased. in F l a s k VI (raw sludge) m o s t or the g a s p r o d u c e d was c a r b o n dioxide, only a small a m o u n t or m e t h a n e was produced. d i r r e r e n c e s n o t e d in the r a ti os or the d i g e s t e d sludge I or b o t h e x o e r i m e n t s ) c a n be r e a d i l y explained. or the d i g e s t e d on any one day, sludge The (Flask The c h a r ac t er d e p e n d s u p o n the amo un t or r a w sludge a d d e d on the o r e c e d i n g day. Since the am ou n t a n d c o m p o s i t i o n or the r a w sludge v a r i e s r r o m day to day, it c a n be e x p e c t e d that the d i g e s t e d sludge w il l be in a dirrerent state or d e c o m p o s i t i o n e a c h day. r o r b o t h the d i r r e r e n c e s ratios or g a s e s sludge alone. most sludge F o r this r e a s o n two cont ro ls w ere sludge. olus r a w or the d i g e s t e d gas p r o d u c t i o n a n d the o b t a i n e d in these e x p e r i m e n t s r r o m d i g e s t e d or the e x p e r i m e n t s . digested in the total T his a c c o u n t s The The r i r s t control s e c on d c o n t ro l sludge. set up w i t h c o n t a i n e d o nl y contained digested These c o n t r o l s i n d i c a t e d the sludge a n d the raw sludge at the condition time the e x p e r i m e n t w a s c a r r i e d out. The p r es e n c e r l u s h i n g or the or o x y g e n in the samples w a s due to insuTrici s y s t e m w i t h ni tr og en . in the p e r c e n t a g e r e a d i l y e x pl ained. The de crease or o x y g e n a n d n i t r o g e n in the samples is Since n e i t h e r o x yg en n o r n i t r o g e n are p r o d u c e d d u r i n g the a n a e r o b i c d i g e s t i o n or sludge, or these observed the volume two g a s e s o r i g i n a l l y p r e s e n t w i l l n o t change. Howevei 24. as the f e r m e n t a t i o n gases are occurs. W h e n sainoles of the produced, gas are c o n c e n t r a t i o n of n i t r o g e n a n d t a ke n f o r analysis, oxygen is reduced. f o r the r e d u c t i o n in the p e r c e n t a g e of in s u b s e q u e n t d i f f u s i o n of the g a s es the This a c c o u n t s these two gases samples. It w a s c o n c l u d e d f r o m this e x p e r i m e n t that the amou nt of raw sludge to be a d u e d to the d i g e s t e d sludge e x p e r i m e n t s w o u l d be that f o u n d in F l a s k II sludge). T h i s q u a n t i t y of r a w sludge in future (50 ml of raw gave a r a p i d methane p r o d u c t i o n a n d a l s o p r e s e n t e d a more f a v o r a b l e a n d a more desirable working mixture t h a n the o t h e r m i x t u r e s C a t i o n i c d e t e r g e n t s and sludge At the same time given c o n c e n t r a t i o n s tested. digestion: the f i r s t e x p e r i m e n t was set up, of a s y n th et i c detergent (BTC) two were i n t r o d u c e d into two f e r m e n t a t i o n f l a s k s c o n t a i n i n g raw a n d d i g e s t e d sludge. of the i m m e d ia te processes. T h i s was done in o r d e r to o b t a i n some idea e f f e c t of this c o m p o u n d on the d i g e s t i o n F l a s k I a n d II in Table for this e x p e r i m e n t . 1, ser ve d as c o n t r o l s The f l a s k s c o n t a i n i n g the synthetic d e t e r g e n t w ere s e e d e d as follows: Flask V - 400 m l of d i g e s t e d / 50 ml F l a s k VI of BTC results 50 m l of r a w sludge (final conc. 50 ppm*) - 400 m l of d i g e s t e d sludge / / 50 m l of BTC The sludge / 50 m l of ra w sludge (final conc. lOO ppm) p r e s e n t e d in Table 3, i n d i c a t e d that c o n c e n t r a t i o n s of 50 a n d lOO p p m oi BTC h a d no d e t r i m e n t a l * p p m - parts per m i l l i o n T a bl e 3. The efi'ect of a syn th et ic d e t e r g e n t (BTC) on the d i g e s t i o n of sludge. Flasks* V Time In hours 10 32 50 11 33 51 *^ 190 400 510 170 370 490 co2 4.6 13.4 17.6 5.0 1 3.4 17.0 * °2 2.0 0.4 0 2.0 O O % h2 O O 0 O 0.4 0.2 tgp % % CH4 * N2 co2 Flasks V VI 6.9 20.5 35.4 6.1 25.3 53.6 86.5 6 5.7 47.0 86.9 60. 9 29.2 1 ch4 ** VI 1.50 1 1 .5 3 1 1 2.01 1.22 - 400 m l of d i g e s t e d sludge / / 50 m l of BTC (final conc. - 40 0 m l of d i g e s t e d sludge / / 50 m l of BTC (final conc. ■a-iir TGP - T o ta l m l of gas p r o d u c e d 50 50 50 lOO 1 1.89 1 3.15 m l of r aw sludge ppm) m l of raw sludge ppm) effect on the of s y n t h e t i c d e t e r g e n t a p p e a r e d to stimulate m e t h a n e the d i g e s t i o n processes* p r o d uc ti on . Rudolfs, o b s e r v e d that lOO Man ga ne ll i , The ph en om en on , was that possess presence and G e l i m a n however, to u t i l i z e It sludge m i g h t the d e t e r g e n t as a source of d e t e r g e n t s w e re k n o w n to l o w e r the s u b s t a n c e s to tne also, since i n t e r f a c i a l tension, surface thereby of the b a c t e r i a l that this m i g h t be the cause f o r s t i m u l a t e d m e t ha ne produc t io n. a n o t h e r f a c t o r w h i c h was considered, c o m p o s i t i o n of the raw sludge. aaded, a ls o was n o t e x p l a i ne d. f o o d m a t e r i a l w i t h the l i b e r a t i o n of me thane. cells, (33) the m i c r o o r g a n i s m s p r e se nt in the the a b i l i t y bringing more of 100 p p m p p m of N a c c o n o l N.R. h a s t e n e d the d i g e s t i o n processes. thought The there (fats, of r a w was n o w ay of g o v e r n i n g the a m o u n t of m a t e r i a l in the aliquot. m a y h a ve Since 50 m l b e e n due proteins, Thus, increased methane was the sludge was solid production to a l a r g e r aiuount of organic m a t e r i a l etc.) in the sample. D i r e c t e f f e c t of a c a t i o n i c a n d an a n i o n i c d e t e r g e n t : In o r d e r to d e t e r m i n e w h i c h of these f a c t o r s m i g h t be r e s p o n s i b l e f o r the I n c r e a s e d m e t h a n e f o l l o w i n g e x p e r i m e n t w a s c a r r i e d out. f l a s k s were s e ed ed as follows: Flask 1 - 500 m l of d i g e s t e d sludge F l a s k IX - 4 5 0 m l of d i g e s t e d sludge (final conc. F l a s k III - 4 50 m l production, the R i ve f e r m e n t a t i o n / 50 ml of BTC lOO ppm) of d i g e s t e d sludge / 50 m l of BTC (final conc. 500 ppm) F l a s k IV - 450 m l of d i g e s t e d sludge / 50 m l of N a c c o n o l (final conc. Flask V lOO ppm) - 450 m l of d i g e s t e d sludge / 50 m l of N a c c o n o l (final conc. The r e s u l t s 500 ppm) p r e s e n t e d in Table 4, the f l a s k s c o n t a i n i n g syn th et ic was impaired with respect show ed that in all detergents, normal digestion to total gas production. The p r o d u c t i o n of m e t h a n e w a s a g a i n s t i m u l a t e d in the flasks c o n t a i n i n g lO O p p m of b o t h BTC a n d Nacconol. of 500 p p m of BTC h a d a m o r e A concentration i n h i b i t o r y e f f e c t on b o t h the total gas p r o d u c e d a n d m e t h a n e p r o d u c t i o n t ha n the same c o n c e n t r a t i o n of Nacc o no l. It was c o n c l u d e d that raw sludge w a s n ot r e s p o n s i b l e f o r the increased methane in the gas was n o t u s e d in this e xp e ri me nt . gas w a s less in all the f l a s k s was a l s o c o n c l u d e d that w ere n o t able to u t i l i z e The stimulated sample, Sinc e the as raw sludge total volume seede d w i t h detergents, the m i c r o o r g a n i s m s to be due to the l o w e r i n g of the therefore, production. appeared interfacial tension between the b a c t e r i a l ce lls a n d w a t er by the de te rg e nt s. 100 p p m it in d i g e s t e d sludge the d e t e r g e n t s for m e t h a n e p r o d u c t i o n of methane, of Thus, of the d e t e r g e n t c a u s e d m o r e f o o d m a t e r i a l to come in c o n t a c t w i t h the m e t h a n e p r o d u c i n g organisms. G a s r a t i o s at d i f f e r e n t i n t e r v a l s of t i m e : The ne x t e x p e r i m e n t w a s r a t i o s of c a r b o n d i o xi de set up to de termine if the to m e t h a n e w o u l d va r y at d i f f e r e n t T a bl e 4* The r a t i o s of c a r b o n dio xi de to m e t h a n e p r o d u c e d w h e n v a r i o u s c o n c e n t r a t i o n s of s y n t he ti c de t e r g e n t s are a d d e d to d i g e s t e d sludge a n d i n c u b a t e d at 35 C. Flasks** I II III IV V 48 49 50 52 53 TGP**** 380 240 100 270 260 % co2 10.0 9.6 9.0 9.4 12.2 % u2 1.6 0.6 0.4 1.2 0.6 * H2 O O O 0 0 T im e In Hrs. . % gh4 1 2.4 1 3.8 2.1 13.5 11.8 % N2 76.0 76.0 88.5 75.9 75.4 C02 CH4 •M- 1 1.24 1 1 . 45 4 . 28 1 - 500 m l of d i g e s t e d sludge - 450 m l of dige sted sludge conc. lOO ppm) III - 4 5 0 m l of dige s ted sludge conc. 500 ppm) IV - 4 5 0 m l of dige sted sludge (final conc. lOO ppm) V - 4 5 0 ml of dige sted sludge I II TGP - T o t a l m l of gas p r o d u c e d 1.03 1 1.43 1 / 50 m l of BTC /, 50 ml of / 50 ml of / 50 ml of (final intervals or time. an accurate A n i n t e r v a l w as d e s i r e d w h i c h w o u l d give picture or the e f f e c t of on the d i g e s t i o n p r o c e ss es . the of total volume concentrations Samples A series of The e f f e c t syntnetlc the synthetic detergent a n a l y s e d a f t e r 5, 48, six f e r m e n t a t i o n f l a s k s were detergents of the d e t e r g e n t on gas was a l s o d e t e r m i n e d . of gas w e r e of the Various (BTC) 96, w ere tested. a n d 168 hou rs . s e e d e d as foll ow s : Flask I - 500 m l of d i g e s t e d sludge Flask II • 400 m l of d i g e s t e d sludge / 50 m l of raw sludge sludge / 50 ml of r a w sludge / 50 m l Flask of w a t e r III - 400 m l of d i g e s t e d / 50 m l F l a 3k IV of BTC - 4 0 0 m l of d i g e s t e d / 50 m l Flask V - 4 00 m l of BTC - of BTC / 50 m l The r e s u l t s of BTC p r e s e n t e d in Table s h o w e d t ha t c o n c e n t r a t i o n s s t i m u l a t e d b o t h the of m e t h a n e . 5 sludge of r aw sludge 200• ppm) sludge / 50 m l (final conc. of r a w 100i ppm) sludge / 50 m l (final conc. 400 m l of d i g e s t e d 50 ppm) sludge / 50 m l (final conc. of d i g e s t e d / 50 m l F l a s k VI (final conc. of raw sludge 500i ppm) (a, b, c, d, e, a n d f) of 50 a n d lOO p p m of BTC total gas p r o d u c t i o n a n d the p r o d u c t i o n A l t h o u g h the f e r m e n t a t i o n s were over a l o n g o e r i o d of time, no c a r r i e d out s i g n i f i c a n t c h a n g e s were o b s e r v e d in the g as r a t i o s a f t e r 48 h o u r s of i n c u ba ti on . The t o t a l v o l u m e of gas p r o d u c e d d u r i n g the 168 h o u r p e r i o d w a s r e c o r d e d in T a b l e 6, a n d g r a p h in F i g u r e F r o m t hi s g r a p h it c a n r e a d i l y be III. p r e s e n t e d in the f o r m of a seen 30. T a b l e 5. A c o m p a r a t i v e study of gas r a t i o s a nd t o ta l gas p r o d u c t i o n over v a r i o u s p e r i o d s of time w h e n different c o n c e n t r a t i o n s of s y n t he ti c d e t e r g e n t are present. a) T ime 500 m l of d i g e s t e d sludge In Hrs. 8 48 98 168 TGP* 120 300 440 550 % co2 6.4 14.6 17.6 19.4 % o2 O 0.4 O O * h 2 O 0 O 0 1.0 13 .6 27.4 36 . 6 * n2 92.6 71.4 55.0 43.9 co2 6.4 1.07 % CH4 ch 1 1 4 1 1.55 1 1.89 ■» T O P - T o t a l m l of ga s p r o d u c e d b) 4 0 0 m l of d i g e s t e d / 50 m l of w a t e r sludge / 50 ml of r a w sludge 6 49 97 169 TOP 240 l llO 1420 1655 % % % % CO g 7. 8 22.6 24.4 25.4 Og 0. 6 O O O Hg O O O O T ime In Hrs. 6.6 35 . 0 50.4 48.0 % N2 85.0 42.4 25.2 26.6 C0g 1.18 ch4 ch 4 1 1 1. 5 4 1 2.05 1 1.89 400 m l of d i g e s t e d sludge / 50 m l of raw sludge / 50 m l of BTC (final conc. 50 ppm) T i me In Hrs. 5 50 96 170 TGP 190 1 1 80 1500 1750 % % co2 6.0 27 .0 27.8 28.4 o2 1.6 O 0 O 0 O 0 o % h2 % 5.5 56.9 60.9 63.0 % n2 8 6 .9 16.1 11.3 8.6 C02 1.09 ch 4 1 1 1 2.19 1 to • to H ch4 to • H O c) d) 400 m l of d i g e s t e d sludge / 50 m l of r a w sludge / 50 m l of BTC (final conc. 100 ppm) 9 51 100 172 TGP 280 1 190 1580 1830 % 8.2 2 6. 8 26.4 26.4 % 02 1.8 0.2 0 O % h2 0 O O 0 Time In Hrs. co2 8.0 5 2. 8 60.4 60.8 % n2 8 2.0 20.2 13.2 12.8 co2 1.02 % ch4 ch 4 1 1 1.89 1 2 .2 5 1 2.30 32. e) 400 m l or d i g e s t e d sludge / 50 m l of r a w sludge / 50 m l of BTC (final conc. 200 ppm) T ime I n Hrs. io 52 101 173 T GP 190 680 1060 1400 % 7 .8 2 5 .6 2 9 .0 2 6 .0 co2 % Og 1 .4 0 0 0 % H2 0 .4 0 O O % ch4 5 .4 3 4 .0 4 5 .2 44.4 * N2 8 5 .0 40.4 2 5 .8 2 9 .6 co2 1 .4 4 1 ch4 1 .3 2 1 1 .5 6 1 .7 0 sludge / 11 53 102 174 TGP 110 220 320 390 % co2 5.6 17.2 24.0 % 02 1.6 0.2 0 — % H2 0.2 O 0 - % ch4 1.2 6.0 9.4 - H • 400 m l of d i g e s t e d sludge / 50 m l of r a w 5 0 m l of BTC (final conc. 500 ppm) 1 <0 f) 1 76.6 66 • 6 - 4.66 2.86 2.55 - T i me In H rs. % N2 cc2 ill o 1 1 1 — Table 6. The effect of different concentrations of synthetic detergent (BTC) on the total volume of gas produced by digesting sludge. F I pe Is * Time In Hours I II III IV V VI 3 120 350 320 270 120 95 24- 205 720 690 520 320 160 4-S 300 1100 1140 1170 650 220 7^ 400 1310 13S0 1440 220 270 96 430 1410 1500 1570 1020 295 120 495 1530 1620 1690 1120 375 142 520 1600 1700 1750 1290 390 162 550 1655 17*45 1220 1370 395 * Flasks I II III IV V VI - JjQO ml of digested sludge - 400 ml of digested sludge / - 400 ml of digested sludge / (fin a l conc. 50 ppm) - 400 ml of digested sludge / (fin a l conc. 100 ppm) - 400 ml of digested sludge / (fin a l conc. 200 ppm) - 400 ml of digested sludge / ( fin a l conc. 500 ppm) 50 ml of raw sludge / 50 ml of water 50 ml of raw sludge / 50 ml of BTC 50 “d. of raw sludge / 50 ml of BTC 50 ml of raw sludge / 50 ml of BTC 50 ml of raw sludge / 50 ml of BTC Figure III. The effect of various concentrations of BTC on the total volume of gas produced by digesting sludge. 2000 ri 0 o 3 rb 0 n 1500 CL. CQ ci PJ C O N C L U S I O N S The a d d i t i o n of large q u a n t i t i e s of raw sludge to d i g e s t e d sludge d e c r e a s e d tiie total gas p r o d u c t i o n a nd tiie p r o d u c t i o n of mettiane. Tiie pr e s e n c e of 10O p p m of cationic, non-ionic detergents in d i g e s t i n g sludge, anionic, a nd s h o w e d no iiarmfull e f f e c t s on the d i g e s t i o n processes. T o t a l gas p r o d u c t i o n a n d m e t h a n e p r o d u c t i o n were s t i m u l a t e d by the pre s e n c e of lOO ppm of d e t e r g e n t s in the d i g e s t i n g mat e r i a l . the synthetic C o n c e n t r a t i o n s of 500 p p m of the d e t e r g e n t s r e t a r d e d the d i g e s t i o n processes. The p r e s e n c e anionic detergent of lOO a n d 500 p p m of a c a t i o n i c a n d an in d i g e s t i n g sludge h a d no g e r m i c i d a l e f f e c t on the c o l i f o r m or g r a m positive m i c r o c o c c u s groups of organisms. Small a m o u n t s of to fatty acids c a r b o n dioxide a n d methane, were r e a d i l y d e c o m p o s e d and h a d n o effect on the c o l i f o r m or g r a m p o s i t i v e m i c r o c o c c u s g r o u p s of organisms. Large a m o u n t s of retarded gasification fatty acids w ere decomposed, b ut processes. A g e r m i c i d a l e f f e ct was o b s e r v e d a g a i n s t the g r a m positive m i c r o c o c c i . Oa.ses left in c o n t a c t w i t h the d i g e s t i n g l i q u o r were shown to c o n t a i n m o r e m e t h a n e than those w h i c h were drawn off and a n a l y s e d at e a r l i e r intervals. 54. .REFERENCES Barker, H.A. On the b i o c h e m i s t r y of* m e t h a n e f ermentation. A r c h i v f u r M i k r o b i o l o g i e , 7, 404, (1936) 2. Barker, H.A. S t u d i e s on m e t h a n e p r o d u c i n g ba c t eria. A r c h i v f u r M i k r o b i o l o g i e , 7, 420, (1936) 3. Barker, H.A. S t u d i e s on m e t h a n e f e r m e n t a t i o n . VI. The i n f l u e n c e of C O o c o n c e n t r a t i o n on the rate of GO^ reduction by molecular hydrogen. Proc. Natl. Acad. Sci., 29, 184, (1943) 4. Barker, H . A . , Ruben, S., a n d Kamen, M.D. The r e d u c t i o n of r a d i o a c t i v e c a r b o n dioxide by m e t h a n e p r o d u c i n g bacteria. Proc. Natl. Acad. Sci., 26, 426, (1940) 5. Buswell , A.M. I m p o r t a n t c o n s i d e r a t i o n s in sludge di g e s t i o n . P a r t II. M i c r o b i o l o g y a n d the ory of a n a e r o b i c digestion. Sew. Wks. J., 19, 28, (1947) 6. Buswell, A.M. a n d B o r u f f , C.S. 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