Ozone Production and Costs - Advances in Chemistry (ACS

Ozone Production and Costs E. L. BEAN

Downloaded by NANYANG TECHNOLOGICAL UNIV on May 7, 2016 | http://pubs.acs.org Publication Date: January 1, 1959 | doi: 10.1021/ba-1959-0021.ch057

Treatment Section, Philadelphia

Water Department, Philadelphia,

Pa.

The Philadelphia ozonation plant has some unusual design features. Because it was a pioneering project, some changes later proved necessary; satisfactory modifications were found. Equipment to produce completely dust-free a n d thoroughly dried air proved its value. Guaranteed capacities of ozone generation a n d efficiencies have been exceeded. With long operation there has been no appreciable change in either. Maintenance has been greatly below that forecast, a n d constant attendance has proved unnecessary. Operational costs are not inconsistent with costs for other oxidation processes used in water treatment. O v e r h e a d costs for this plant are not comparable with those for a plant built at present. Reduction of tastes a n d odors a n d removal of manganese have been appreciable, a n d g o o d bacterial and coliform organism kills have resulted.

Philadelphia's o z o n a t i o n p l a n t , p l a c e d i n service i n e a r l y 1949, i s l o c a t e d a t t h e B e l mont W a t e r Treatment P l a n t ; treating water pumped from the Schuylkill R i v e r . O z o n e - g e n e r a t i n g c a p a c i t y of t h e p l a n t i s 1250 p o u n d s p e r d a y . A t t h e t i m e of i n s t a l l a t i o n t h i s w a s t h e l a r g e s t i n t h e w o r l d a n d 16 t i m e s l a r g e r t h a n a n y o t h e r p l a n t t r e a t i n g w a t e r i n A m e r i c a . I t s o z o n e - g e n e r a t i n g u n i t s w e r e of a t y p e p r e v i o u s l y u s e d o n l y i n one v e r y s m a l l p l a n t . T h e p r o j e c t w a s , t h e r e f o r e , s o m e t h i n g of a p i o n e e r i n g d e v e l o p ment. T h e S c h u y l k i l l , o v e r 125 m i l e s l o n g , h a s i n recent y e a r s b e e n c l e a n e d , b y d r e d g i n g f r o m i t s source t o t h e F a i r m o u n t D a m , w h i c h f o r m s t h e p o o l as source of B e l m o n t ' s w a t e r , a n d p o l l u t i o n h a s been m i n i m i z e d . I n t h e f o r t i e s , h o w e v e r , t h e c o n d i t i o n s were v e r y d i f f e r e n t . T h e S c h u y l k i l l , w h i c h h a s i t s sources i n t h e c o a l m i n i n g areas, r e c e i v e d a g r e a t a m o u n t of c o a l c u l m , also açid m i n e d r a i n a g e , t h e n passed t h r o u g h a l i m e s t o n e region where t h e a c i d reacted w i t h limestone. I t t h e n passed t h r o u g h a h i g h l y i n d u s t r i a l i z e d a r e a , w h e r e b o t h i n d u s t r i a l a n d d o m e s t i c wastes w e r e r e c e i v e d , l a r g e l y u n t r e a t e d — t h e f o r m e r f r o m some 40 different i n d u s t r i e s , t h e l a t t e r f r o m s e v e r a l c o m m u n i t i e s of c o n s i d e r a b l e size. F o r a source of p u b l i c s u p p l y , t h e B e l m o n t r a w w a t e r w a s , i n t h e f o r t i e s , u n u s u a l l y p o l l u t e d b a c t e r i o l o g i c a l l y , a n d b y a v a r i e t y of o r g a n i c wastes w h i c h c a u s e d tastes a n d odors. M a n g a n e s e c o n t e n t s o m e t i m e s exceeded 5 p . p . m . T h e w a t e r c o n t a i n e d a g r e a t a m o u n t of c o a l c u l m a n d some c l a y s ; t h e t u r b i d i t i e s r a n g e d , i n y e a r l y averages, u p t o 1200 p . p . m . , w i t h r e a d i n g s s o m e t i m e s r e a c h i n g 3000 p . p . m . A t t h e B e l m o n t p l a n t , a 35,000,000-gallon b a s i n p r o v i d e d a c t u a l d e t e n t i o n s a p p r o x i m a t i n g 16 h o u r s a t t h e r a t e of 36,000,000 gallons p e r d a y . A i d e d b y a l u m a p 430

OZONE CHEMISTRY AND TECHNOLOGY Advances in Chemistry; American Chemical Society: Washington, DC, 1959.

BEAN—PRODUCTION A N D

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COSTS

p l i c a t i o n a t t i m e s of h i g h t u r b i d i t i e s , t h e s e t t l e d t u r b i d i t y w a s u s u a l l y b e t w e e n 10 a n d 30. T h i s w a t e r w a s t h e n t r e a t e d w i t h c h l o r i n e , w i t h a l u m a n d limé t o flocculate, a n d w i t h c a r b o n f o r taste a n d o d o r r e m o v a l . I t w a s p a s s e d t h r o u g h baffled m i x i n g b a s i n s , 2 - h o u r s e t t l i n g b a s i n s , a n d r a p i d s a n d filters, f o l l o w e d b y p o s t c h l o r i n a t i o n .


M a n g a n e s e p a s s e d t h r o u g h t h e r a p i d s a n d filters; t h e r e f o r e , o z o n a t i o n c o u l d n o t be a p p l i e d t o f i l t e r e d w a t e r w i t h o u t l o a d i n g t h e d i s t r i b u t i o n s y s t e m w i t h m i n e r a l i z e d manganese. P o i n t of o z o n a t i o n w a s c h o s e n as t h e p r e s e t t l e d w a t e r b e f o r e a p p l i c a t i o n of t h e c h e m i c a l s . P i l o t p l a n t tests h a d p r e v i o u s l y b e e n r u n w i t h a 2 - g a l l o n - p e r - m i n u t e a n d a 1,000,0 0 0 - g a l l o n - p e r - d a y u n i t . T h e s e i n d i c a t e d t h e effectiveness of o z o n a t i o n , a n d t h a t t h e m a x i m u m a p p l i c a t i o n r e q u i r e d w o u l d b e less t h a n 4 p . p . m . T h i s w a s a d o p t e d as t h e d e s i g n c a p a c i t y , a n d t h e p l a n t w a s b u i l t t o p r o d u c e t h e 4 p . p . m . dosage o n a flow of 36,000,000 g a l l o n s p e r d a y , w i t h t w o g e n e r a t o r s o u t of s e r v i c e (3).

Description of

Plant

A t m o s p h e r i c a i r is c l e a n e d b y passage t h r o u g h e l e c t r o s t a t i c filters, c o m p r e s s e d t o a b o u t 10 p . s i . g . b y five 4 0 0 - c u . f o o t p e r m i n u t e r o t a r y b l o w e r s , c o o l e d b y w a t e r c o i l s , f o l l o w e d b y r e f r i g e r a t e d coils, t o u n d e r 5 0 ° F . , t h e r e b y d r y i n g t o u n d e r 50 g r a i n s of m o i s t u r e p e r p o u n d of d r y a i r , a n d p a s s e d t h r o u g h one of f o u r c r u s h e d a l u m i n u m d r y e r s t o p r o d u c e d e w p o i n t s b e l o w — 60° F . , e q u a l t o a m o i s t u r e c o n t e n t of less t h a n 1 g r a i n p e r p o u n d of d r y a i r . O z o n e is g e n e r a t e d b y 50 g e n e r a t o r s m a n u f a c t u r e d b y t h e W e l s b a c h C o r p . , e a c h g u a r a n t e e d t o p r o d u c e 25 p o u n d s of ozone p e r 24 h o u r s . T h e g e n e r a t o r shells a r e

OZONE

RESIDUAL,

P.P.M*

76

Figure 1.

Coliform kill by ozone

Points plotted are averages of monthly average kills at various ozone residuals, 1950 to 1955

w a t e r - c o o l e d a n d of a l l stainless s t e e l ; e a c h g e n e r a t o r u t i l i z e s 8 5 b o r o s i l i c a t e glass t u b e electrodes, 3 inches i n d i a m e t e r , c o a t e d o n t h e i n s i d e w i t h g r a p h i t e f o r c u r r e n t d i s t r i b u t i o n , p r o t e c t e d b y B i t u m a s t i c e n a m e l . C u r r e n t is s t e p p e d u p t o 15,000 v o l t s f o r generation.


432

A D V A N C E S IN CHEMISTRY SERIES

OZONE


Ο ΙΟΟι

.10 1

.20 1

RESIDUAL, RP.M* .30 1

.40 1

.50 1

80

Figure 2.

Bacterial kill by ozone

Points plotted are average kill shown by 9 0 % of all individual tests (37° count, 24 hours, on agar) for various ozone residuals, 1950 to 1955 * (?)

Ozonized air is conducted underground to three contact chambers, where it is diffused into the water at a depth of 1 8 % feet. Water enters the top of these 25-foot square chambers on one side, and passes downward and across the chambers. A t

Figure 3.

Schematic layout of ozonation plant


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r"°Φ

3

,0

LIGHTING. METERING AND RECORDING CIRCUITS

Feeder from local utility < 3f, 13200 V, 60 cycle \ Motoring transformer d lSOPO0-kvo, 3P Γ*Ί Oil circuit breaker, solenoid operated

SSSÏ

OZONE-GENERATOR CONTROL CIRCUITS LEGEND Phose Transformer Fuss •φα Disconnect Λ Air circuit breaker mem 1,000 circular mills Ρ Pole τ Contactors Reactors Ψ Ozone generators Grounds

3P, 1.000 amp, 6O0v. Γ

Î

300omp.-*.Τ 460-3(1

?304000 l**"™™ èfcmt mires φ Is^. T^.


e a U t

r

Γ

{ L * 50-contactors \ I^Z*-50-I0*HI reactors

/VU S d* 50-25kva.-l$ w . ^ ' V . v w 460/15000* on roof 50-12km. atone — generators je

νγν Y 2-5 hp. blowers Y I adsorpfive dryers I 2-93k*theators-adsorptivo dryers

Ooor«noty»*»

— M

ΓΦ •f 16 units ir 16 units ψ 181

OZONE-GENERATOR CIRCUITS

AUXILIARY EQUIPMENT CIRCUITS

Figure 4.

Electrical wiring diagram

maximum flow the theoretical contact is 10 minutes, plates, later replaced b y porous tubes.

Capital

Diffusion was originally b y porous

Costs

Cost of construction of this plant (engineering, inspection, and other expenses figured at 2 0 % of the contract costs) totals $1,000,000, divided as follows: equipment, 7 0 % ; electric service, main supply transformers, switch gear, etc., 4 % ; housing struc ture, 1 0 % ; contact or diffuser tanks, 16%.

Figure 5 .

Refrigerative dryers a n d air blowers



434


Figure 6. Difficulties

Refrigerative dryers

Encountered

Refrigerative D r y e r s . I n designing the plant, ample air was provided to operate down to 0.5% ozone concentration, if this proved most efficient. This was not the case, and not long after the plant was placed in operation, the river was cleaned to the extent of reducing ozone requirements. W i t h the resultant low air demand, refrigerative coils froze and the compressor units required frequent service. A s emergency correction the water supply to the water cooling section was shut off, throwing the

Figure 7.

Adsorptive dryers



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Figure 8.

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O z o n e generating equipment a n d control panel

w h o l e c o o l i n g l o a d t o t h e r e f r i g e r a t i v e s e c t i o n . P r o p o r t i o n i n g v a l v e s h a v e since b e e n installed to control the refrigeration proportionally to the loading. Adsorptive Dryers. I t q u i c k l y d e v e l o p e d t h a t t h e a d s o r p t i v e d r y e r s w e r e n o t b e i n g p r o p e r l y d r i e d . A f t e r d r y i n g , i n s t e a d of — 6 0 ° F . t h e d e w p o i n t m i g h t r u n o n l y t o — 2 0 ° F . , a n d t h e n o n l y f o r a s h o r t t i m e . R e d d i s h b r o w n deposits s t a r t e d t o f o r m i n the generator tubes. T h e a d s o r p t i v e u n i t s a r e d r i e d b y passage of h o t a i r d o w n w a r d t h r o u g h t h e alumina bed, the moisture picked u p then being dropped out i n a standard commercial

Figure 9.

O z o n e generator header a n d tubes



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u n i t , c o n s i s t i n g of a c h a m b e r c o n t a i n i n g coils t h r o u g h w h i c h c o o l i n g w a t e r is c i r c u l a t e d . T h e c o n d e n s e d m o i s t u r e is l e d off t h r o u g h a t r a p p e d o p e n i n g t o d r a i n . T h e floor of t h e c h a m b e r w a s c o n t i n u a l l y flooded. T h i s w a s c o r r e c t e d c o m p l e t e l y b y r e l o c a t i o n a n d a d j u s t m e n t of t h e d r a i n t r a p . E l e c t r i c a l L e a d s . I n t h e o r i g i n a l i n s t a l l a t i o n N o . 14 n e o n s i g n cable w a s i n s t a l l e d t h r o u g h Và-inch c o n d u i t f r o m t h e t r a n s f o r m e r s t o t h e electrodes of g e n e r a t o r u n i t s . T h e s e cables, f u l l y i n s u l a t e d f o r 15,000 v o l t s t o g r o u n d , b u r n e d off f r e q u e n t l y a t t h e e n d of i n s u l a t i o n nearest t h e g e n e r a t o r electrode. M a n y different t y p e s of i n s u l a t e d cable were t e s t e d w i t h t h e same r e s u l t . T h e cause w a s n e v e r s a t i s f a c t o r i l y d e t e r m i n e d ; h o w e v e r , i t w a s f o u n d t h a t b a r e w i r e of a l a r g e r size g a v e n o s u c h d i f f i c u l t y , a n d t h i s was i n s t a l l e d o n a l l u n i t s , p a s s i n g t h r o u g h a glass t u b e as i n s u l a t o r t h r o u g h t h e roof o n l y . M e t a l g u a r d cages w e r e p r o v i d e d b e l o w t h e r o o f . Reactor H u m . R e a c t o r s , i n s t a l l e d t o c o r r e c t t h e p o w e r f a c t o r , p r o d u c e d a v a r i e t y of tones a n d p i t c h e s w h i c h were v e r y d i s t u r b i n g a n d s o m e t i m e s v e r y l o u d . A l l r e a c t o r s w e r e r e t u r n e d t o t h e m a n u f a c t u r e r , w h o i m p r e g n a t e d t h e m free of c h a r g e , almost completely eliminating sound.

Figure 10.

Transformers

Transformers. T h r e e of t h e 4 6 0 - t o 15,000-volt t r a n s f o r m e r s s h o r t e d a n d b u r n e d o u t i n t h e f i r s t y e a r a n d a h a l f of o p e r a t i o n . T h e m a n u f a c t u r e r s c o n c l u d e d t h a t t h e b u i l t - i n i m p e d a n c e of 2 % w a s n o t e n o u g h . T h e y r e c o m m e n d e d t h e a d d i t i o n of 180 o h m s ' resistance o n t h e h i g h v o l t a g e side, t o e q u a l t o t a l i m p e d a n c e of 4 % . T h i s w a s d o n e a n d o n l y one t r a n s f o r m e r h a s f a i l e d i n t h e p a s t 6 y e a r s . Valves. Considerable difficulty was experienced w i t h leaking valves o n the ozone lines n e a r t h e g e n e r a t o r s . D i f f e r e n t t y p e s of p a c k i n g s w e r e t e s t e d u n t i l a s a t i s f a c t o r y m a t e r i a l a n d s h a p e s o l v e d t h e d i f f i c u l t y . T e f l o n v a l v e seats a n d p a c k i n g s h a v e since been u s e d . Generators. W h e n placed i n service, t w o u n i t s developed leaks at t h e header tube c o n n e c t i o n s w h i c h h a d n o t a p p e a r e d u n d e r test. T h e s e w e r e w e l d e d i n p l a c e . O n e tube developed a pinhole leak. T h i s was cut out a n d replaced b y a new tube. Elevation Control. E l e v a t i o n was controlled i n the diffusion chambers b y a 4 2 i n c h b u t t e r f l y v a l v e , e l e c t r i c a l l y o p e r a t e d . T h e v a l v e design i n c l u d e d a r a i s e d seat f o r t h e b u t t e r f l y . T h i s v a l v e , at t i m e s , o p e n e d t o a c e r t a i n p o i n t , t h e n fluttered w i t h s u c h f o r c e as t o b r e a k t h e d r i v i n g l i n k a g e . E v e n t u a l l y t h e v a l v e w a s r e m o v e d f r o m t h e l i n e , t h e r a i s e d seat m a c h i n e d o u t , a n e w b u t t e r f l y i n s t a l l e d , a n d h e a v i e r d r i v i n g mechanism provided. Ozone Diffusion. I n t h e o r i g i n a l i n s t a l l a t i o n , t h e stainless steel p i p i n g f e d t h e o z o n a t e d a i r i n t o a 5 - i n c h - w i d e d i s t r i b u t i o n c h a n n e l , f o r m e d i n t o t h e c o n c r e t e floor of each t a n k , a n d covered w i t h nonporous concrete slabs. O z o n a t e d a i r was d i s t r i b u t e d


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o u t w a r d t h r o u g h c i r c u l a r o p e n i n g s i n t h e w a l l s of t h i s c h a n n e l i n t o a s h a l l o w c h a m b e r , b e n e a t h p o r o u s p l a t e s . I t passed u p w a r d t h r o u g h t h e 1-inch p o r o u s p l a t e s t o diffuse t h r o u g h o u t t h e Ι δ / ^ feet of w a t e r a b o v e . T h e i n s i d e of t h e c h a n n e l a n d t h e e n t i r e t a n k b o t t o m u n d e r t h e p l a t e s w a s c o a t e d w i t h B i t u m a s t i c t o a v o i d a t t a c k b y ozone. J o i n t s b e t w e e n t h e p l a t e s were p o u r e d w i t h h o t B i t u m a s t i c . A l l m e t a l s u p p o r t u n i t s were of stainless steel.


1

Figure Π .

Contact chambers

I t p r o v e d i m p o s s i b l e t o k e e p j o i n t s b e t w e e n t h e p l a t e s sealed, a p p a r e n t l y because of s h r i n k a g e of t h e B i t u m a s t i c s . T e s t s o n one d a y i n d i c a t e d t h a t as m u c h as 2 0 % of t h e ozone a p p l i e d t o one t a n k w a s e s c a p i n g t o t h e a t m o s p h e r e . T h e ozone w a s d e c o m p o s i n g t h e c o n c r e t e of t h e d i s t r i b u t i o n c h a n n e l i n s p i t e of t h e c o a t i n g s a p p l i e d . R e p l a c e m e n t s of these b o t t o m s b y p o r o u s stainless steel diffuser t u b e s w a s p r o posed, b u t t h e m a n u f a c t u r e r s , a f t e r some t r i a l s , s t a t e d t h e y c o u l d n o t f u r n i s h t h e u n i f o r m i t y , b e t w e e n different t u b e s , w h i c h w a s c o n s i d e r e d necessary. F i n a l l y p o r o u s t u b e s of fused a l u m i n a were i n s t a l l e d , 72 p e r t a n k , 3 - i n c h d i a m e t e r , 3 6 - i n c h l e n g t h , % - i n c h t h i c k n e s s , w i t h a i r p e r m e a b i l i t y of 25 c u . feet p e r m i n u t e p e r s q . foot, a t 2 - i n c h h e a d . A l l p i p e s , b o l t s , etc., were of stainless steel. T e s t s f o l l o w i n g i n s t a l l a t i o n of these t u b e s i n d i c a t e d t h a t 90 to 9 5 % of t h e ozone w a s b e i n g u s e d i n t h e reactions. Atmospheric Pollution. B e c a u s e of t h e d i f f i c u l t y of k e e p i n g diffuser p l a t e s sealed, a n d t h e r e s u l t a n t ozone w a s t e t o t h e a t m o s p h e r e , grass a n d s h r u b b e r y n e a r b y were d e s t r o y e d , a n d , o n d a m p d a y s , or w h e n t h e w i n d s h i f t e d t o c a r r y f r o m t h e p l a n t t o w a r d t h e n e i g h b o r i n g houses j u s t across t h e s t r e e t , t h e n e i g h b o r s c o m p l a i n e d , j u s t i f i a b l y . L i g h t - w e i g h t c o v e r s of p r o t e c t e d , c o r r u g a t e d , g a l v a n i z e d steel w e r e p l a c e d o v e r t h e t a n k s , w i t h s u c t i o n lines t o a b l o w e r d i s c h a r g i n g u p w a r d t h r o u g h a s t a c k , t o t h e atmosphere. A l o n g one edge of e a c h c o v e r a n o p e n i n g w a s l e f t , a b o u t 1 i n c h w i d e , w h i l e t h e s u c t i o n w a s f r o m t h e o p p o s i t e side of t h e t a n k . T h e b l o w e r d e l i v e r y w a s 10,000 c u . feet p e r m i n u t e , w h i l e o z o n a t e d a i r v o l u m e is less t h a n 1 0 0 0 ; t h e r e f o r e , d i s c h a r g e f r o m t h e diffuser t a n k s is d i l u t e d m o r e t h a n t e n t i m e s before r e a c h i n g t h e atmosphere. T h e s e c o v e r s a n d b l o w e r were i n s t a l l e d b e f o r e t h e diffusion t a n k b o t t o m s were c h a n g e d , a n d p r o v e d insufficient a t t h a t t i m e , b u t since t h e change t o p o r o u s tubes n o difficulties h a v e been e x p e r i e n c e d . Operation T h e contract for ozonation equipment placed upon the contractor responsibility f o r o p e r a t i n g t h e o z o n e - g e n e r a t i n g p l a n t f o r 90 d a y s , d u r i n g w h i c h t i m e he w a s t o



438

t r a i n p e r s o n n e l , e m p l o y e d b y t h e c i t y , i n b o t h o p e r a t i o n a n d m a i n t e n a n c e of t h e p l a n t . T h e c i t y ' s g r o u p of f o u r s h i f t m e n o p e r a t e d t h e p l a n t e x c l u s i v e l y f o r a b o u t 4 y e a r s , one m a n b e i n g i n t h e b u i l d i n g a t a l l t i m e s . S i n c e t h a t t i m e these o p e r a t o r s , o r i g i n a l l y filter p l a n t o p e r a t o r s , h a v e been assigned t o o p e r a t e t h e s l o w s a n d f i l t e r s a n d p o s t t r e a t m e n t , as w e l l as o z o n a t i o n . R e a d i n g s a r e r e c o r d e d e a c h 3 h o u r s o n a l l o p e r a t i o n s . T h e o p e r a t o r s a r e o u t of t h e ozone p l a n t f r o m 1 t o 2 h o u r s o u t of e a c h 3. T h e r e appears to be n o reason t o change this arrangement.


A m e c h a n i c a l engineer w a s assigned r e s p o n s i b i l i t y f o r o p e r a t i o n a n d m a i n t e n a n c e of t h i s p l a n t , as h i s first r e s p o n s i b i l i t y . A m a j o r p a r t of h i s t i m e w a s d e v o t e d t o i n s p e c t i o n s , o r m e c h a n i c a l w o r k a t o t h e r l o c a t i o n s , a n d f o r t h e p a s t 3 y e a r s he h a s devoted very little time to this plant. D a t a o n o p e r a t i o n o f t h e p l a n t a r e g i v e n i n T a b l e I , f o r t h e y e a r s 1950 t o 1955. T a b l e I.

Belmont Ozonation Plant O p e r a t i o n D a t a , 1 9 5 0 to 1 9 5 5

Os produced, lb./day % capacity Max. monthly av. % capacity M i n . monthly av. % capacity Max. day production % capacity M i n . day production % capacity Total production Days operated Total water treated, mg. Os, lb./mg. Os applied, p.p.m. Os, lb./gen. unit/ 24 hours Total kw.-hr. (all uses) Av. cost per kw.-hr, $ Os, kw.-hr./lb. Kw.-hr./mg. treated Cooling water, mg./d operated Total mg. Gal./lb. Os Cost at $9.00 / m g . Air use, million cu. ft. C.f .m. per gen. unit, av.

Av. 1950-55 427 34

1950 541 43 687 55 344 27 902 72 120 10 193,085

1951 476 38 637 51 346 24 822 66 81 6 172,892

1952 301 24 354 28 219 18 436 34 65 5 34,601

1953 398 32 707 57 234 19 800 64 77 6 140,696

1954 469 37 788 63 273 22 869 69 130 10 171,877

1955 377 30 524 42 255 20 618 49 91 7 123,606

357

363

115

354

363

328

313

12,264 15.7 1.89

11,882 14.7 1.76

2,856 12.1 1.45

12,097 11.6 1.39

12,436 13.8 1.65

11,886 10.4 1.25

10,570 13.2 1.58

139,459

27.1

23.5

25.9

24.6

25.6

24.8

25.3

2,430,813 0.01021

2,309,043 0.01016

411,700 0.0126

1,570,900 ?

1,738,500 ?

1,296,500 0.0133

1,626,243 ?

12.6 198

13.4 194

11.9 144

11.1 130

10.1 140

10.5 109

11.6 154

0.985 342.00 1774 $3038

0.923 335.51 1933 $3019

0.633 72.95 2093 $657

0.806 285.24 2027 $2567

0.923 335.28 1950 $3017

0.837 274.82 2223 $2475

0.851 274.30 1965 $2469

? ?

336.900 31.8

31.2

192.926 23.2

275.418 28.6

223.611 31.1

? ?

T h e p l a n t w a s o p e r a t e d o n l y 8 5 % of t h e t i m e , t r e a t i n g a n a v e r a g e of 10,570,000,000 gallons p e r y e a r . R a t e o f g e n e r a t i o n a v e r a g e d o n l y 3 4 % of c a p a c i t y . C o o l i n g w a t e r use a v e r a g e d 851,000 gallons p e r d a y , o r 1956 g a l l o n s f o r e a c h p o u n d o f ozone p r o l u c e d . E l e c t r i c c u r r e n t use a v e r a g e d 154 k w . - h r . f o r e a c h m i l l i o n g a l l o n s o f w a t e r treated. Maintenance M a i n t e n a n c e h a s been b y r e g u l a r m e c h a n i c s e m p l o y e d o n t h e f i l t e r p l a n t , o r b y mechanics a n d electricians e m p l o y e d i n t h e p u m p i n g station d i v i s i o n . T h r e e exceptions h a v e b e e n a c o n t i n u i n g c o n t r a c t f o r s e r v i c i n g of t h e r e f r i g e r a t i o n e q u i p m e n t b y m a n u f a c t u r e r s ' r e p r e s e n t a t i v e s , t h e w o r k of t h e m e c h a n i c a l engineer m e n t i o n e d u n d e r operation, a n d m a n u f a c t u r e r s ' servicing of t h e d e w p o i n t recorder, w h i c h has been r e q u i r e d o n s e v e r a l occasions. N e a r l y a l l of t h e difficulties e n c o u n t e r e d w e r e t a k e n c a r e of b y t h e c o n t r a c t o r f o r the equipment, under the contract. A p p r o x i m a t e l y t w o dozen leaks have developed i n t h e generator tube connections


BEAN-PRODUCTION AND

439

COSTS


t o headers, w h i c h h a v e b e e n w e l d e d i n p l a c e . O n l y one hole t h r o u g h a t u b e h a s b e e n r e c o r d e d , a b o u t 2 inches f r o m one e n d . I t w a s w e l d e d a n d t h e n g r o u n d s m o o t h . G l a s s electrode t u b e f a i l u r e s h a v e been f e w , e v e n i n c l u d i n g t h e l e a k s , w h i c h a l l o w t h e g e n e r a t o r t o f i l l p a r t i a l l y w i t h w a t e r , a n d d e s t r o y one o r m o r e t u b e s . U n d e r t h e o r i g i n a l c o n t r a c t , t h e c o n t r a c t o r s u p p l i e d 5 % e x t r a electrode t u b e s . N o m o r e t h a n one h a l f of these h a v e b e e n a c t u a l l y r e q u i r e d t h u s f a r . A t t h e t i m e of i n s t a l l a t i o n , o n t h e basis of i n f o r m a t i o n f r o m o t h e r ozone p l a n t s , i t was e s t i m a t e d t h a t t h e stainless steel t u b e surfaces w o u l d h a v e t o be c l e a n e d e v e r y 6 m o n t h s . O n l y 20 of t h e 50 u n i t s h a v e e v e r been c l e a n e d . T h o s e u n c l e a n e d a r e n o t i n b a d c o n d i t i o n . T h i s is t h e finest evidence of t h e efficacy of t h e c o m p l e t e a i r c l e a n i n g and drying.

Efficiencies Production. T e s t s o n t h e e q u i p m e n t , w h e n first i n s t a l l e d , s h o w e d t h a t g e n e r a t i o n of ozone w o u l d exceed t h e 25 p o u n d s p e r u n i t p e r 24 h o u r s , necessary t o m e e t t h e s p e c i fications, w h e n a i r flow w a s s u c h as t o p r o d u c e c o n c e n t r a t i o n s i n t h e r a n g e of 0.33 t o 1 . 1 1 % . T e s t s a b o v e t h i s range were n o t m a d e . T h e best p r o d u c t i o n (28.0 t o 28.4 p o u n d s ) w a s s h o w n a t a r o u n d 0 . 9 % a n d t h e r e were evidences of some r e d u c t i o n a t h i g h e r c o n c e n t r a t i o n s . A t 0 . 6 5 % o r less, p r o d u c t i o n b a r e l y m e t t h e s p e c i f i c a t i o n . P r o d u c t i o n t h r o u g h o u t t h e t o t a l p e r i o d of o p e r a t i o n h a s a v e r a g e d 25.3 p o u n d s p e r u n i t p e r 24 h o u r s . I n t h e o r i g i n a l tests p r o d u c t i o n a t 0 . 6 7 % c o n c e n t r a t i o n w a s 26.3 p o u n d s p e r u n i t . I n 1954, a 4 - d a y c h e c k test, u n d e r s i m i l a r c o n d i t i o n s , o p e r a t i n g 12 g e n e r a t o r s , h a v i n g a n a v e r a g e of 11,160 h o u r s of o p e r a t i o n , p r o d u c e d 26.1 p o u n d s p e r u n i t p e r d a y . T h i s was less t h a n 1 % change, w i t h generators w h i c h h a d o p e r a t e d , w i t h o u t c l e a n i n g , e q u a l t o 16 m o n t h s ' c o n t i n u o u s s e r v i c e . Current Use. A v e r a g e use of e l e c t r i c c u r r e n t f o r a l l p u r p o s e s h a s b e e n 11.6 k w . - h r . p e r p o u n d of ozone g e n e r a t e d . F r o m t h e s t a n d p o i n t of p r a c t i c a l o p e r a t i o n s t h i s is t h e o n l y figure w h i c h is of v a l u e ; t h e r e f o r e , c i r c u i t s were n o t m e t e r e d t o b r e a k d o w n t h e use. H o w e v e r , a n e s t i m a t e d b r e a k d o w n i n d i c a t e s t h e f o l l o w i n g a p p r o x i m a t e c u r r e n t uses ( k i l o w a t t - h o u r s p e r p o u n d of ozone) : Air blowers Refrigerative and absorptive dryers Lights, fans and heaters, recording equipment, miscellaneous Blower at diffusion tanks for waste dilution and discharge Generator units (remainder) Total use

2.0 1.0 0.25 0.25 8.1 11.6

Costs C o m p l e t e o p e r a t i o n a l costs a r e a v a i l a b l e o n l y f o r t h e y e a r s 1950, 1951, a n d 1955 ( T a b l e I I ) . O p e r a t i o n a l l a b o r a n d expense a r e i n d i c a t e d as 2 1 . 2 % , m a i n t e n a n c e 8 . 9 % , e l e c t r i c c u r r e n t 5 9 . 3 % , h e a t i n g 2 . 8 % , c o o l i n g w a t e r 7 . 8 % . T o t a l o p e r a t i o n a l costs a v e r a g e d $3.03 p e r m i l l i o n gallons of w a t e r t r e a t e d , a n d $0.23 p e r p o u n d of ozone p r o d u c e d . T h i s p l a n t w a s o p e r a t e d o n l y 9 8 , 9 9 , a n d 9 0 % of t h e t i m e i n t h e t h r e e y e a r s , a n d a t o n l y 4 3 , 3 8 , a n d 3 0 % of c a p a c i t y ; t h e r e f o r e fixed i t e m s of expense g r e a t l y affect costs p e r u n i t p r o d u c e d o r t r e a t e d . I n e a c h of t h e t h r e e y e a r s o v e r h e a d costs o n t h e p l a n t a m o u n t e d t o a b o u t $5.00 p e r m i l l i o n g a l l o n s . H o w e v e r , i n 1950, o v e r h e a d costs p e r p o u n d of ozone g e n e r a t e d were 31 cents, a n d i n 1955 t h e y were 4 8 cents d u e t o r e d u c t i o n i n a p p l i c a t i o n f r o m 1.89 t o 1.25 p . p . m . , w i t h consequent r e d u c e d p r o d u c t i o n . C o m b i n e d o p e r a t i o n a l a n d o v e r h e a d costs h a v e a m o u n t e d t o $8.03 p e r m i l l i o n g a l lons. T h e $3.03 p e r m i l l i o n gallons o p e r a t i o n a l cost t o t a l is n o t i n c o n s i s t e n t w i t h t h e cost of o t h e r m e t h o d s u s e d f o r o x i d a t i o n i n w a t e r t r e a t m e n t . O v e r h e a d s u c h as w i t h


440


Table II.

Operation Labor Expense Maintenance Labor Expense Elec. current cost Heating Cooling water

Costs of Belmont Ozonation Plant in 1 9 5 0 , 1 9 5 1 , and 1 9 5 5

1950


Av.

% of Operation Costs

$ 5,939.05) 2,010.27 J

1,800.00» 301.95 24,741.25 1,039.80 3,038.00

3,154.00) 1,274.68} 23,447.55 1,100.00» 3,019.00

3,346,46

3,292.36

8.9

17,307.45 893.28 2,475.00

21,832.08 1,011.03 2,844.00

59.3 2.8 7.8

38,914.39 3.17 0.20

39,944.55 3.30 0.23

31,530.73 2.56 0.26

36,796.55 3.03 0.23

100.0

Overhead Interest on $1 million at 2% $20,000 Depreciation on $1 million at 4% 40,000 Total 60,000 Per mg. treated 4.90 Per lb. Os produced 0.31

a

1955

$ 6,366.93 1,626.46

Total absolute costs Per mg. treated Per lb. O3 produced

Grand totals Per mg. treated Per lb. Os produced

1951

$

8.07 0.51

$20,000

$ 7,508.54

$ 7,817.08

21.2

$20,000

40,000 60,000 5.05 0.35

40,000 60,000 5.05 0.48

5.00 0.38

8.41 0.58

7.61 0.74

8.03 0.61

Estimated.

t h i s p l a n t i s n o t c o m m o n l y i n v o l v e d w i t h o t h e r m e t h o d s i n g e n e r a l use, t h o u g h s u c h need m a y be r e a d i l y conceived where large contact basins are n o t already available. T h i s c o m p l e t e p l a n t , o p e r a t e d a t 8 0 % of c a p a c i t y , p r o d u c i n g 1000 p o u n d s of ozone p e r d a y , d e p r e c i a t e d o v e r 25 y e a r s , w o u l d c a r r y o v e r h e a d e q u a l t o 16 cents p e r p o u n d p r o d u c e d , a n d o p e r a t i o n a l costs w o u l d b e s o m e w h a t m o r e t h a n t h i s a m o u n t , o r a t o t a l of a b o u t 3 5 cents p e r p o u n d . H o w e v e r , m o d e r n t e c h n o l o g y , less t h a n 10 y e a r s a f t e r d e s i g n o f t h i s p l a n t , a l r e a d y assures n e w p l a n t s i n w h i c h costs w i l l b e , p e r h a p s , n o more t h a n half. Dosage

Control

A m o u n t o f ozone a p p l i c a t i o n is c o n t r o l l e d b y t h e n u m b e r of g e n e r a t o r s p l a c e d i n o p e r a t i o n . T h e a m o u n t of ozone b e i n g g e n e r a t e d is d e t e r m i n e d f r o m t h e c u b i c feet p e r m i n u t e p a s s i n g t h r o u g h t h e p l a n t a n d a n i o d o m e t r i c t i t r a t i o n of 1 c u . f o o t of t h e ozonated air passing to the contact t a n k s . T h e a m o u n t of dosage specified i s o r d i n a r i l y d e t e r m i n e d f r o m t h e r e s i d u a l i n t h e ozonated water leaving the contact tanks. Residuals are determined b y the standard o - t o l i d i n e a r s e n i t e test {1), as specified f o r free r e s i d u a l c h l o r i n e . T e s t s a r e m a d e o n t h e site, i m m e d i a t e l y o n s a m p l i n g , n o t a f t e r d e l a y d u e t o r e t u r n t o t h e l a b o r a t o r y . T h i s i s v e r y i m p o r t a n t because of t h e r a p i d change i n r e s i d u a l . T h e m e t h o d of c o n t r o l c o u l d b e b a s e d o n m a n g a n e s e r e m o v a l , as r e s i d u a l of 0.1 p . p . m . r e m o v e s 8 0 % a n d p r o d u c e s b a c t e r i a l a n d c o l i f o r m k i l l of 9 5 t o 9 7 % . I f m a n ganese r e m o v a l i s o v e r 8 0 % , t h e r e f o r e , g o o d k i l l of o r g a n i s m is a s s u r e d . O n e f a u l t of t h i s m e t h o d i s t h a t i t f a i l s t o s h o w i f t h e dosage i s m o r e t h a n n e e d e d , as m a n g a n e s e r e m o v a l does n o t a p p r e c i a b l y increase w i t h h i g h e r r e s i d u a l s . Effects o f O z o n a t i o n Tastes a n d O d o r s . D u r i n g t h e e a r l y y e a r s of o p e r a t i o n , c o n s i d e r a b l e t r a d e wastes were r e c e i v e d ; m o r e r e c e n t l y t h i s h a s n o t been t r u e . O z o n a t i o n p r o v e d effective o n r e m o v a l of m a t e r i a l s c a u s i n g taste a n d o d o r , p a r t i c u l a r l y t h e p h e n o l i c s . I n t h e first y e a r of o p e r a t i o n i t p r o d u c e d a 7 0 % r e d u c t i o n i n t h e c o l d odors. I n 1951 t h e


BEAN-PRODUCTION AND

441

COSTS

average reduction was 5 5 % ; the odor intensities were measured b y the s t a n d a r d t h r e s h o l d m e t h o d (2). W i t h r e d u c i n g i n t e n s i t y of o d o r s i n t h e r i v e r w a t e r , t h e p e r c e n t ages w e r e r e c o r d e d as 4 7 % i n 1952 a n d 4 5 % i n 1953. S i n c e 1953 t h r e s h o l d s of o d o r s i n t h e r a w w a t e r h a v e b e e n too l o w t o w a r r a n t p e r c e n t a g e c o m p a r i s o n s . O n m u s t y o r g a n i c o d o r s a n d tastes of n a t u r a l o r i g i n , as f r o m leaves a n d weeds, o z o n a t i o n h a s n o t p r o v e d e n t i r e l y effective, t h o u g h i t has definite effects. I n 8 months of 1951 a n d 1952 r a w w a t e r c h a r a c t e r i s t i c s were v e r y s i m i l a r . W i t h o z o n a t i o n f u n c t i o n i n g i n 1951 o n l y 2 0 % of t h e p l a n t effluent s a m p l e s w e r e d e t e r m i n e d as h a v i n g m u s t y o d o r s , w h i l e i n 1952 w i t h o u t o z o n a t i o n , i n s p i t e of o t h e r t r e a t m e n t s u s e d , m u s t y o d o r s were p r e s e n t i n 2 8 % of t h e s a m p l e s .


D i s i n f e c t i o n . K i l l of c o l i f o r m o r g a n i s m s , a n d of b a c t e r i a w h i c h g r o w a t 37° C , o n a g a r is s h o w n i n T a b l e I I I , b y y e a r l y averages. These indicate practically identical

Table 111.

A v e r a g e Yearly Kill of Bacteria ( 9 0 %

of Tests)

Percentage Kill

1950 1951 1952

Ozone Residual, P.P.M.» 0.20 0.16 0.20

1953 1954

0.08 0.08

96.5) 92.1 J

1955 1956 (Jan.-Sept.)

0.06 0.033

90.5 78.7

a

b

Coliform organisms 97.7) 97.8} 97.5)

97.7

Q

,

y 4

Q

'

d

Bacteria 97.6) 98.9} 98.0} 95.5) 93.8} 90.7 78.5

b

98.2 94.6 90.7

Determined by standard o-tolidine-arsenite method for free residual chlorine (/). Determined by counts on agar, at 37° C. for 24 hours.

percentages f o r t h e t w o classes, a n d k i l l s d e f i n i t e l y p r o p o r t i o n e d t o t h e ozone r e s i d u a l s . T h e k i l l s were a p p r o x i m a t e l y 9 0 . 5 % f o r a v e r a g e ozone r e s i d u a l of 0.06 p . p . m . , 9 4 . 5 % f o r 0.08 p . p . m . , a n d 9 8 % f o r 0.16 a n d 0.20 p . p . m . I n F i g u r e 1 is s h o w n the p e r c e n t a g e k i l l of c o l i f o r m o r g a n i s m s a g a i n s t v a r i o u s r e s i d u a l s . E a c h p o i n t p l o t t e d r e p r e s e n t s t h e a v e r a g e of a l l m o n t h l y k i l l s w h e n t h e ozone r e s i d u a l a v e r a g e d as i n d i c a t e d . K i l l s are 9 5 % w i t h less t h a n 0.1 p . p . m . r e s i d u a l a n d 9 9 % w i t h 0.2 p . p . m . a n d o v e r . F i g u r e 2 shows t h e k i l l of 37° b a c t e r i a a t t h e v a r i o u s ozone r e s i d u a l s . T h e p o i n t s p l o t t e d w e r e d e t e r m i n e d b y a v e r a g i n g t h e k i l l s h o w n b y 9 0 % of a l l b a c t e r i a tests, c o r r e l a t e d w i t h t h e v a r i o u s r e s i d u a l s , t h r o u g h o u t t h e 6 y e a r s 1950 t o 1955. K i l l s of b e t t e r t h a n 9 5 % a r e i n d i c a t e d f o r r e s i d u a l s of 0.1 p . p . m . a n d u p w a r d . M a n g a n e s e R e m o v a l . I n 1950, 1951, a n d 4 m o n t h s of 1952, w i t h 0.32, 0.46, a n d 0.30 p . p . m . of m a n g a n e s e i n t h e w a t e r b e f o r e o z o n a t i o n , a n d w i t h ozone r e s i d u a l s of 0.20, 0.16, a n d 0.20 p . p . m . , t h e r e m o v a l of m a n g a n e s e w a s , r e s p e c t i v e l y , 78.2, 82.5, a n d 80.0%. T h e r e m o v a l w i t h o u t o z o n a t i o n i n 8 m o n t h s of 1952 w a s 4 2 . 8 % . T h e s e figures r e p r e s e n t t h e r e s u l t of o z o n a t i o n o r n o o z o n a t i o n , l i m e a n d a l u m a p p l i c a t i o n , m i x i n g , s e t t l i n g , a n d passage t h r o u g h r a p i d s a n d f i l t e r s . 0

B a s e d o n m o n t h l y averages, i t a p p e a r s t h a t i n t h i s p e r i o d , r e m o v a l s w i t h 0.10 p . p . m . of ozone r e s i d u a l were j u s t as g r e a t as w i t h r e s i d u a l s u p t o 0.25 p . p . m . S i n c e 1952, a p p l i c a t i o n of c h l o r i n e before f i l t r a t i o n , t o r e d u c e t h e p o s t d o s a g e r e q u i r e d t o p r o d u c e free r e s i d u a l i n d i s t r i b u t i o n , has m a d e r e m o v a l figures n o n c o m p a r able. A i r b u b b l e s , a t t a c h i n g t o o x i d i z e d m a n g a n e s e p a r t i c l e s , h a v e c a u s e d flotation flumes a n d s e t t l i n g b a s i n s , r e q u i r i n g i n s t a l l a t i o n of w a t e r s p r a y s t o s t o p s u r f a c e cumulations.


on ac


442

Literature

Cited

(1) American Public Health Association and American Water Works Association, New York, "Standard Methods for the Examination of Water Sewage and Industrial Wastes," 10th ed., p. 72. (2) Ibid., pp. 202-6. (3) Taylor, E. J., Bean, E. L., Eng. News Record (July 28, 1949). for review June 19, 1957.

Accepted June 19, 1957.


RECEIVED


Ozone Production and Costs - Advances in Chemistry (ACS

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