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ULTRAVIOLETLIGHTD lSlNFECTIONOF WATERIN ATEXTILEAIR WASHER

POLLUTION PREVENTION PROGRAMNORTH CAROLINA DEPARTMENT OF ENVIRONMENT, HEALTH, AND NATURAL RESOURCES

James G. Mart inGovernor

Will iam W. Cobey. JrSecretary, EHNR

EVALUATION OF A TEFLON BASED ULTRAVIOLET LIGHT SYSTEM ON THE

DISINFECTION OF WATER IN A TEXTILE AIR WASHER

By:

J . E d w a r d S m i t h , I IHYDRO SYSTEMS, INC.

Ra lph B . Wh isnan tJ. P. STEVENS & CO., INC.

Augus t 1 , 1987

F u n d i n g f o r t h i s r e p o r t w a s p r o v i d e d b y a P o l l u t i o n P r e v e n t i o nCha l l enge Gran t f rom the Nor th Caro l ina Depar tment o f Na tura l Resourcesand Community Development.

C O P Y R I G H T

Pol lu t ion Preven t ion Pays ProgramN.C. Department of Natural Resources and Community Development

January 1988

THE POLLUTION PREVENTION PROGRAM

The Pollution Prevention Program provides free technical assistance toNorth Carolina industries and municipalities on ways to reduce, recycleand prevent wastes before they become pollutants. This non-regulatoryprogram addresses water and air quality, toxic materials, and solid andhazardous waste. Designated as the lead agency in waste reduction, theProgram works in cooperation with the Solid Waste Management Divisionand the Governor's Waste Management Board. The services and assistanceavailable fall into the following categories:

Information Clearinghouse. An information data base provides accessto literature sources, contacts, and case studies on waste reductiontechniques for specific industries or waste streams. Information isalso available through customized computer literature searches. Wastereduction reports published by the Program are also available.

Specific Information Packages. The staff can prepare facility orwaste-stream-specific waste reduction reports for industries andcommunities. Information provided by the facility is used to identifycost-effective waste reduction options. A short report detailing theseoptions is provided along with references, case studies, and contacts.

On-site Technical Assistance. The staff can provide comprehensivetechnical assistance through facility visits. During an on-site visit,detailed process and waste stream information is collected. Theinformation is analyzed, and a series of waste reduction options areidentified. A report is prepared detailing these options and includesliterature, contacts, case studies, and vendor information.

Outreach. The staff can give presentations on pollution preventionto industries, trade associations, professional organizations, andcitizen groups. Depending on the audience, these programs range froman overview of the State's Pollution Prevention Program to in-depthdiscussions of technologies for specific industries.

Challenge Grants. A matching grant program provides finds for thecost of personnel, materials, or consultants needed to undertakepollution prevention projects. Projects eligible for grant funds rangefrom characterizing waste streams in order to identify pollutionreduction techniques to conducting in-plant and pilot-scale studies ofreduction technologies.

For information or technical assistance contact:

Pollution Prevention ProgramOffice of Waste ReductionN.C. Department of Environment, Health, and Natural ResourcesPost Office Box 27687Raleigh, North Carolina 27611-7687

Telephone: (919) 571-4100

U l t r a v i o l e t ( U V ) l i g h t , w h i c h d e s t r o y s a l l m i c r o o r g a n i s m s ( a l g a e ,b a c t e r i a - i n c l u d i n g L e g i o n n a i r e s D i s e a s e B a c t e r i a , f u n g i , m o l d s , v i r u sp a r t i c l e s ) , a d d s n o t h i n g t o t h e w a t e r , d o e s n o t a l t e r t h e p H o r c a u s es c a l i n g o r o t h e r d e p o s i t s , a n d r e q u i r e s n o s p e c i a l h a n d l i n g o rp r o c e s s i n g , w a s e v a l u a t e d o n t h e a i r w a s h e r p o r t i o n o f a t e x t i l e a i rh a n d i n g s y s t e m . T h e U V u n i t e m p l o y e d u t i l i z e d a T e f l o n t u b e t ot r a n s p o r t t h e a q u a t i c p h a s e . P r i o r t o u n i t s t a r t u p , c h e m i c a l t r e a t m e n tw i t h b i o c i d e s h a d y i e l d e d m i c r o b i a l p o p u l a t i o n s w i n g s b e t w e e n 1 0 5 t o10 9T e f l o n

c o l o n y f o r m i n g u n i t s p e r m i l l i l i t e r ( C F U / m l ) . However, the un iqueU V u n i t r e d u c e d t h e s e p o p u l a t i o n s t o 1 0 3 t o 1 0 4 C F U / m l ,

m a i n t a i n e d t h i s d e n s i t y d a y i n a n d d a y o u t w i t h o u t t h e a d d i t i o n s o fb i o c i d e s , a n d , d u r i n g t h e s i x ( 6 ) m o n t h t e s t p e r i o d , r e q u i r e d n oc l e a n i n g o r o t h e r m a i n t e n a n c e o f t h e w e t t e d s u r f a c e s . S l i m e d e p o s i t so b s e r v e d o n w a l l s o f t h e a i r w a s h e r d u r i n g c h e m i c a l t r e a t m e n t w e r e a l s oe l i m i n a t e d . T h e U V u n i t c a n b e u t i l i z e d o n b o t h c o o l i n g t o w e r s a n d a i rw a s h e r s w i t h o u t e x t e n s i v e i n s t a l l a t i o n . F u r t h e r , b e c a u s e t h e r e i s ar e d u c t i o n i n o p e r a t i o n a n d m a i n t e n a n c e c o s t , n o d i s c h a r g e o f t o x i cc h e m i c a l s , a n d n o e x t e n s i v e m a i n t e n a n c e t o k e e p t h e U V u n i t o p e r a t i n ge f f i c i e n t l y , a s h o r t p a y b a c k ( 2 y e a r ) p e r i o d a n d s u b s t a n t i a l s a v i n g s i sp o s s i b l e .

TABLE OF CONTENTS

INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

DESCRIPTION OF THE INSTALLATION SITE . . . . . . . . . . . . . . . . . . . . . . .

RESULTS AND DISCUSSION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

P h a s e I T e s t i n g . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

P h a s e I I T e s t i n g . . . . . . . . . . . . . . . . . . . . . . . . . . . .

P h a s e I I I a n d I V T e s t i n g . . . . . . . . . . . . . . . . . . . . . . . .

V i s u a l O b s e r v a t i o n s . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

U V U n i t M a i n t e n a n c e R e q u i r e m e n t s . . . . . . . . . . . . . . . . . . . . . . . . . .

C a p i t a l a n d O p e r a t i o n C o s t . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

I n h e r e n t A d v a n t a g e s o f U V v s C h e m i c a l T r e a t m e n t . . . . . . . . . . . . . .

CONCLUSIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

APPENDIX

F i g u r e 1 : S c h e m a t i c o f 100-LX U V D i s i n f e c t i o n U n i t . . . . . . . . .

F i g u r e 2 : I n s t a l l a t i o n S c h e m a t i c . . . . . . . . . . . . . . . . . . . . . . . .

F i g u r e 3 : E f f e c t o f U l t r a v i o l e t D i s i n f e c t i o n o n T P C F r o mA i r W a s h e r No.1 D u r i n g F i r s t 2 4 H o u r s o f P h a s e I . . . . .

F i g u r e 4 : E f f e c t o f U l t r a v i o l e t D i s i n f e c t i o n o n T P C F r o mAi r Washer No . 1 Dur ing F i rs t 13 Days o f Phase I .......

F i g u r e 5 : M i c r o b i a l A n a l y s i s t o C o n f i r m P r e s e n c e o f A r e ao f I n c o m p l e t e M i x i n A i r W a s h e r N o . 1 . . . . . . . . . . . . .

F i g u r e 6 : L o n g T e r m E f f e c t o f U l t r a v i o l e t D i s i n f e c t i o n o nTPC From Air Washer No. 1 . . . . . . . . . . . . . . . . . . . . . . . .

T a b l e 1 : H S I M o d e l l00 -LX U n i t S p e c i f i c a t i o n s . . . . . . . . . . . . . .

T a b l e 2 : A i r H a n d l i n g S y s t e m N o . 1 S p e c i f i c a t i o n s a n dU l t r a v i o l e t S y s t e m D e s i g n C r i t e r i a . . . . . . . . . . . . . . . . .

T a b l e 3 : P r e l i m i n a r y M i c r o b i a l A n a l y s i s b y D i p S l i d eTechn ique . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

T a b l e 4 : Summary o f Raw Da ta Co l l ec ted In Phase I . . . . . . . . . . . . 24

Tab

Tab

Tab

Paqe

1

2

4

5

7

10

11

11

12

13

15

16

17

18

19

20

21

22

22

23

e 5: S o l i d s A n a l y s i s . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

e 6: M i c r o b i a l A n a l y s i s b y D i p S l i d e T e c h n i q u e . . . . . . . . . . 26

e 7: P a y b a c k A n a l y s i s - 1 0 0 - L X U V U n i t . . . . . . . . . . . . . . . 27

EVALUATION OF A TEFLON BASED ULTRAVIOLET SYSTEM ON THE

DISINFECTION OF WATER IN A TEXTILE AIR WASHER

FINAL REPORT

INTRODUCTION

--

T h i s r e p o r t p r o v i d e s a n i n - d e p t h e v a l u a t i o n o f a T e f l o n b a s e d

u l t r a v i o l e t ( U V ) d i s i n f e c t i o n u n i t a s a p p l i e d t o t h e t r e a t m e n t o f

c o o l i n g w a t e r i n a t e x t i l e a i r w a s h e r s y s t e m , E v a l u a t i o n o f t h i s

equipment was conducted in s i tu and based on three methods:- -

i . ) A n a l y t i c a l d a t a c o l l e c t e d i n t h e f i e l d b y r e s e a r c h e r s a t t h e

U n i v e r s i t y o f N o r t h C a r o l i n a a t C h a r l o t t e ( U N C - C ) i n a c c o r d a n c e

w i t h p r o c e d u r e s o u t l i n e d i n t h e S t a n d a r d M e t h o d s f o r A n a l y s e s o f

W a t e r ’ a n d W a s t e w a t e r , 1 3 t h E d i t i o n ;

i i . ) B a c t e r i a l d a t a c o l l e c t e d b y t h e a u t h o r s a n d p l a n t p e r s o n n e l a t

t h e J . P . S t e v e n s L i n c o l n t o n P l a n t u s i n g t h e d i p s l i d e t e c h n i q u e ,

S e l e c t i c u l t - T T C , S c o t t L a b o r a t o r i e s , F i s k e v i l l e , R . I . ; a n d

i i i . ) T a c t i l e a n d v i s u a l o b s e r v a t i o n s b y t h e a u t h o r s .

T h e s t u d y e m p l o y e d a H S I M o d e l 1 0 0 - L X u l t r a v i o l e t d i s i n f e c t i o n u n i t

s u p p l i e d b y H y d r o S y s t e m s , I n c . , G a s t o n i a , N . C . , c a p a b l e o f d i s i n f e c t i n g

a i r w a s h e r c o o l i n g w a t e r a t a r a t e o f 1 0 0 G P M . S p e c i f i c a t i o n s f o r t h e

100-LX u n i t a r e s h o w n i n T a b l e 1 , b e l o w ; w h i l e F i g u r e 1 p r e s e n t s a

s c h e m a t i c o f t h e 1 0 0 - L X U V d i s i n f e c t i o n u n i t . F igure 2 shows a

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

m o u n t e d U V d i s i n f e c t i o n u n i t i n s t a l l e d a t p o s s i b l e l o c a t i o n s .

I n s t a l l a t i o n c a n b e e f f e c t e d s i m p l y ; a n d , i f t h e U V u n i t i s i n s t a l l e d

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

p i p i n g , a i r w a s h e r s h u t d o w n m a y b e a v o i d e d .

DESCRIPTION OF THE INSTALLATION SITE

Test and evaluat ion was conducted on the Number One (1) a i r

w a s h e r / c h i l l e d w a t e r u n i t a t t h e J . P . S t e v e n s P l a n t i n L i n c o l n t o n , N o r t h

C a r o l i n a . T a b l e 2 d e s c r i b e s t h e p a r t i c u l a r d e s i g n c r i t e r i a o f t h e N o . 1

a i r w a s h e r s y s t e m o n w h i c h t h e U V u n i t w a s i n s t a l l e d . T h i s a i r w a s h e r

s e r v e s s p i n n i n g , c a r d i n g , r o v i n g a n d w i n d i n g o p e r a t i o n s . F i b e r s i n u s e

i n c l u d e r a y o n , f l a x a n d p o l y e s t e r , T w o l a r g e f a n s a r e u s e d t o c i r c u l a t e

a i r f r o m t h e p r o d u c t i o n a r e a a t a r a t e o f 1 6 0 , 0 0 0 c u b i c f e e t p e r m i n u t e .

D u r i n g w a r m w e a t h e r , t e m p e r a t u r e a n d h u m i d i t y c o n t r o l i n p r o d u c t i o n

a r e a s a r e p r o v i d e d b y a 3 5 0 t o n Y o r k r e f r i g e r a t i o n m a c h i n e . D u r i n g

c o o l e r w e a t h e r , h o w e v e r , t h e r e f r i g e r a t i o n m a c h i n e i s s h u t d o w n . T h u s ,

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

a n d / o r b r i n g i n g i n c o o l e r o u t s i d e a i r . The amount o f outs ide a i r used

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

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

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

a i r w a s h e r . ( F l a x u s e d a t t h e S t e v e n ’s L i n c o l n t o n P l a n t i s a n

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

A l l a i r e n t e r i n g t h e a i r w a s h e r i s f i r s t p a s s e d t h r o u g h a i r - m a t a i r

f i l t e r s t o r e m o v e t h e m a j o r i t y o f a i r b o r n e c o n t a m i n a n t s . Y e t i n

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

a r e s c r u b b e d o u t i n t h e s p r a y c h a m b e r o f t h e a i r w a s h e r . T h u s , a

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

o t h e r c o n t a m i n a n t s . M a n y o f t h e s e , i n t u r n , b e c o m e f o o d f o r t h e m i c r o -

o r g a n i s m s w h i c h a r e a d a p t e d t o l i v i n g i n t h e s e c o l d w a t e r ( 4 5 - 5 5 F ° )

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

i n a n a i r w a s h e r , b a c t e r i a l e v e l s c a n r a p i d l y e x c e e d a m i l l i o n

m i c r o o r g a n i s m s p e r m i l l i l i t e r . L e f t u n c o n t r o l l e d , b a c t e r i a l s l i m e

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

e f f i c i e n c y o f h e a t e x c h a n g e s u r f a c e s . I n e x t r e m e c a s e s t h e s e b a c t e r i a l

s l i m e s c a n c o n t r i b u t e f o u l o d o r s t o t h e r e t u r n a i r ; a n d , d e p o s i t s w h i c h

f o r m o n t h e m i s t e l i m i n a t o r b l a d e s c a n d r y , f l a k e o f f a n d a l s o e n t e r t h e

p l a n t a i r s t r e a m .

P r i o r t o t h e b e g i n n i n g o f t h i s s t u d y , t h e a i r w a s h e r w a s b e i n g

t r e a t e d t h r e e t i m e s p e r w e e k w i t h a c h e m i c a l b i o c i d e w h o s e a c t i v e

i n g r e d i e n t w a s 4 5 % g l u t a r a l d e h y d e . I n a d d i t i o n t o t h i s b i o c i d e , t h e

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

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

c o n t i n u o u s b a s i s , a n d a n “a n t i - s t a t ” p r o d u c t f e d i n t e r m i t t e n t l y b y

chemical pump. T h e f e e d r a t e o f t h e a n t i - s t a t w a s c o n t r o l l e d b y a n “i o n

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

p o s i t i v e s t a t i c c h a r g e . T h e a b i l i t y o f t h e a n t i - s t a t c h e m i c a l t o

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

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

t h e w a t e r t r e a t m e n t c h e m i c a l s u s e d , including most commonly used

b i o c i d e s .

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

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

p e r m i n u t e . T h r o u g h o u t t h i s s t u d y o f t h e U V l i g h t u n i t , b i o c i d e u s e w a s

suspended. H o w e v e r , t h e u s e o f o t h e r c h e m i c a l s a n d t h e b l e e d o f f w e r e

c o n t r o l l e d t h e s a m e a s b e f o r e .

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

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

a p p r o x i m a t e f i v e ( 5 ) t o s e v e n ( 7 ) w e e k s c h e d u l e . This was necessary

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

c o n t a m i n a n t s s u c h a s d i r t , l i n t a n d s l i m w o u l d b u i l d u p i n t h e a i r

w a s h e r ’s e l i m i n a t o r b l a d e s , o n t h e s u r f a c e o f t h e w a t e r i n t h e a i r

l e a v i n g e n d o f t h e w a s h e r b a s i n , a n d t o a l e s s e r e x t e n t o n t h e w a l l s o f

t h e w a s h e r b o t h a b o v e a n d b e l o w t h e w a t e r l e v e l .

The UV system was ins ta l led on a i r washer No. 1 on January 4, 1987.

I n a n t i c i p a t i o n o f t h e U V u n i t ’s s t a r t u p o n J a n u a r y 2 7 , 1 9 8 7 , t h e a i r

w a s h e r h a d n o t b e e n c l e a n e d f o r a t e n ( 1 0 ) p e r i o d s o t h a t d i s i n f e c t i o n

b y t h e U V u n i t c o u l d b e e v a l u a t e d o n a “w o r s t c a s e ” c o n d i t i o n .

RESULTS AND DISCUSSION

O u r t a s k w a s t o e v a l u a t e t h e w a t e r q u a l i t y i n t h e N o . 1 a i r w a s h e r

d u r i n g t h e t r i a l p e r i o d a f t e r t h e U V t r e a t m e n t s y s t e m w a s i n s t a l l e d .

T h i s w a s t o b e a c c o m p l i s h e d i n t w o s t a g e s . P h a s e I t e s t i n g a n d

e v a l u a t i n g o f t h e U V u n i t b e g a n o n J a n u a r y 2 7 , 1 9 8 7 a n d c o n t i n u e d

through March 15, 1987. P h a s e I i n v e s t i g a t i o n s w e r e t o d e t e r m i n e t h e

e f f e c t i v e n e s s o f U V t r e a t m e n t o n a d i r t y a i r w a s h e r . T h e r e f o r e , a s

s t a t e d a b o v e , a i r w a s h e r c l e a n i n g w a s p o s t p o n e d . F u r t h e r , d a t a w a s

c o l l e c t e d t o i n v e s t i g a t e w h e t h e r U V e x p o s u r e a l t e r e d t h e c h e m i c a l

c h a r a c t e r i s t i c s o f t h e w a t e r u n d e r s t u d y . P h a s e I I i n v e s t i g a t i o n s w e r e

f o r t h e p u r p o s e o f a s s e s s i n g t h e U V u n i t ’s l o n g t e r m o p e r a t i o n a l

c h a r a c t e r i s t i c s , m a i n t e n a n c e r e q u i r e m e n t s , a n d m i c r o o r g a n i s m k i l l i n g

e f f i c i e n c i e s . Phase II testing began on March 17th and ran through May

2 , 1 9 8 7 . P h a s e I I I las ted f r o m M a y 3 r d t h r o u g h June 2 0 , 1 9 9 7 . P h a s e

I I I w a s t o e v a l u a t e t h e U V u n i t w i t h o n e h a l f o f t h e e i g h t g e r m i c i d a l

l a m p s s w i t c h e d o f f a n d s u p p l e m e n t e d w i t h a d d i t i o n s o f t w o ( 2 ) p o u n d s p e r

day of 35% hydrogen perox ide. Hydrogen perox ide in the presence of UV

l i g h t f o r m s a n e x t r e m e l y a g g r e s s i v e o x y g e n f r e e r a d i c a l w h i c h h a s b e e n

s h o w n t o o x i d i z e o r g a n i c m a t t e r a n d k i l l m i c r o o r g a n i s m s . P h a s e I V w i l l

i n c l u d e t h e e v a l u a t i o n o f a P . E . P . s a n d f i l t e r u s e d i n c o n j u n c t i o n w i t h

t h e U V u n i t , a n d a t t h i s w r i t i n g i s s t i l l i n p r o g r e s s .

T a b l e 3 s h o w s d a t a o n b a c t e r i a l c o u n t s c o l l e c t e d b y t h e d i p s l i d e

t e c h n i q u e d u r i n g N o v e m b e r a n d D e c e m b e r , 1 9 8 6 . T h e s e p r e l i m i n a r y d a t a

i n d i c a t e d t h a t b a c t e r i a l p o p u l a t i o n s w e r e f l u c t u a t i n g b e t w e e n 1 0 a n d5

910 colony forming units (CFU) per milliliter (ml). T h a t i s , w i t h i n

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

d e t e r m i n e d t o b e 1 0 5 C F U / m l . F o r t y - e i g h t h o u r s a f t e r a d d i t i o n o f t h e

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

p o p u l a t i o n s w e r e o b s e r v e d t o b e i n t h e r a n g e o f 1 0 8 t o 1 0 9 C F U / m l .

P o p u l a t i o n d y n a m i c s o f t h i s n a t u r e , t h a t i s t h e “p e a k s a n d v a l l e y s ”,

h a v e b e e n t h e a u t h o r s ’ g e n e r a l o b s e r v a t i o n i n a w i d e v a r i e t y o f

i n d u s t r i a l a i r h a n d l i n g a n d c o n d i t i o n i n g e q u i p m e n t w h e r e c h e m i c a l

t r e a t m e n t i s e m p l o y e d .

P h a s e I T e s t i n g

U n i v e r s i t y b a s e d a n a l y s i s w e r e t a r g e t e d t o d e t e r m i n e o v e r a l l w a t e r

q u a l i t y a s w e l l a s o p e r a t i o n e f f i c i e n c y . T a b l e 4 b e l o w , p r e s e n t s a

s u m m a r y o f r a w d a t a c o l l e c t e d d u r i n g P h a s e I t e s t i n g a s p e r f o r m e d b y

researchers a t UNC-C. A s c a n b e s e e n f r o m T a b l e 4 , U V d i s i n f e c t i o n h a d

n o d i s c e r n i b l e e f f e c t o n t h e c h e m i c a l c h a r a c t e r i s t i c s o f t h e w a t e r i n

a i r w a s h e r N o . 1 . F l u c t u a t i o n s i n p a r a m e t e r s s u c h a s p H , t u r b i d i t y ,

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

w a s h e r s y s t e m t h r o u g h o u t t h e t e s t p e r i o d . T h i s w a s t h e e x p e c t e d r e s u l t

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

a n y t h i n g t o o r t a k e a n y t h i n g f r o m t h e w a t e r .

D a t a f r o m T a b l e 4 r e g a r d i n g t h e r e l a t i o n s h i p b e t w e e n T o t a l S o l i d s

( T S ) a n d T o t a l V o l a t i l e S o l i d s ( T V S ) a r e s h o w n i n T a b l e 5 , b e l o w .

S o l i d s a n a l y s i s w a s c o n s i d e r e d t o b e t t e r d e t e r m i n e t h e e x a c t i m p a c t o f

t h e U V t r e a t m e n t o n t h e o r g a n i c c o n t e n t o f t h e a i r w a s h e r . A h i g h

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

w a s o c c u r r i n g i n t h e s y s t e m , T h e s e d a t a , h o w e v e r , a r e i n c o n c l u s i v e .

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

s e r v i c e d b y a n a i r w a s h e r , I n t h i s c a s e i t i s m o r e l i k e l y t h a t t h e s e

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

to the air washer and the sump water bleed off rate, both of which were

manual ly c o n t r o l l e d .

O f a l l w a t e r q u a l i t y v a r i a b l e s i n f l u e n c i n g t h e e f f e c t i v e n e s s o f U V ,

t h e t r a n s m i s s i o n o f U V l i g h t t h r o u g h t h e f l u i d i s t h e m o s t i m p o r t a n t ,

Compared to other substances, water i s a n e x c e l l e n t t r a n s m i t t e r o f U V

l i g h t . For example, u l t r a p u r e w a t e r h a s a t r a n s m i s s i o n o f U V a t 2 5 4

n a n o m e t e r s ( n m ) o f 0 . 9 9 0 . T h u s , t h e a b s o r b a n c e o f U V i n u l t r a p u r e w a t e r

i s 0 . 0 0 4 4 ( - l o g T r a n s m i s s i o n = A b s o r b a n c e ) , w h i l e t h e a b s o r p t i o n

c o e f f i c i e n t i s 0 . 0 1 c m -1 ( A b s o r p t i o n C o e f f i c i e n t = 2 . 3 0 3 x A b s o r b a n c e ) .

I n g e n e r a l t e r m s , t h i s m e a n s t h a t t h e r e i s a b o u t a 1 0 p e r c e n t d r o p i n U V

i n t e n s i t y t h r o u g h u l t r a p u r e w a t e r . T h e r e f o r e , U V t r a n s m i s s i o n t h r o u g h

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

e i t h e r a b s o r b o r s c a t t e r U V l i g h t . A s t h e m i c r o b i a l p o p u l a t i o n

d e c r e a s e s i n a g i v e n f l u i d , t h e p e n e t r a t i o n o f U V l i g h t w i l l i n c r e a s e .

T h i s , i n t u r n , w i l l a c t t o i n c r e a s e t h e e f f e c t i v e n e s s o f t h e U V u n i t .

As a compar ison, e f f l u e n t w a t e r f r o m a s e c o n d a r y w a s t e w a t e r t r e a t m e n t

p l a n t l a g o o n w i t h 1 0 0 p p m s u s p e n d e d s o l i d s a n d 3 0 p p m B O D w i l l t y p i c a l l y

h a v e a n a b s o r p t i o n c o e f f i c i e n t o f 0 . 5 0 ; w h i l e p o o r q u a l i t y d r i n k i n g

w a t e r w i l l h a v e a n a b s o r p t i o n c o e f f i c i e n t o f 0 . 2 0 .

A t t h e o n s e t o f P h a s e I t e s t i n g , U V t r a n s m i s s i o n ( a b s o r b a n c e ) a t

2 5 4 n m w a s e x p e c t e d t o i m p r o v e w i t h t i m e . T h u s , m a k i n g t h e n e c e s s a r y

c a l c u l a t i o n s t o c o n v e r t U V a b s o r b a n c e f r o m T a b l e 4 t o a b s o r p t i o n

c o e f f i c i e n t , t h e s e d a t a i n d i c a t e t h a t t h e a b s o r p t i o n c o e f f i c i e n t o f a i r

w a s h e r N o . 1 i m p r o v e d f r o m 0 . 5 4 t o 0 . 2 9 o v e r t h e t e s t p e r i o d .

F i n a l l y , w e l o o k e d a t b a c t e r i a l l e v e l s i n t h e a i r w a s h e r . F i g u r e 3

s h o w s d i a g r a m m a t i c a l l y t h e e f f e c t o f U V l i g h t o n t h e n u m b e r o f b a c t e r i a l

c o l o n y f o r m i n g u n i t s p e r m i l l i l i t e r ( C F U / m l ) d u r i n g t h e f i r s t 2 4 h o u r s

o f s a m p l i n g . M o s t r e m a r k a b l e i s t h e d r a m a t i c d e c r e a s e d u r i n g t h e f i r s t

h o u r a f t e r a c t i v a t i n g t h e U V system. B a c t e r i a l total plate c o u n t s

d r o p p e d f r o m 1 . 3 1 x 1 0 t o6 2.34 x 10 5 CFU/ml d u r i n g t h i s p e r i o d .

A d d i t i o n a l l y , b a c t e r i a l p l a t e c o u n t s d r o p p e d t o 7 . 2 0 x 1 0 4 CFU/ml by

t h e e n d o f 2 4 h o u r s o f U V i r r a d i a t i o n . T h i s r e p r e s e n t s n e a r l y a t w o l o g

d e c r e a s e o r 9 4 . 5 p e r c e n t r e d u c t i o n o v e r i n i t i a l c e l l c o u n t s p r e s e n t a t

s t a r t u p o f t h e U V u n i t .

D a t a p r e s e n t e d d i a g r a m m a t i c a l l y i n F i g u r e 4 s h o w a c o n t i n u a l

d e c r e a s e i n b a c t e r i a l p o p u l a t i o n s o v e r t h e t h i r t e e n d a y ( 3 1 2 h o u r s )

p e r i o d o f s a m p l i n g . These data show that the 100-LX UV uni t employed in

t h i s s t u d y r e d u c e d i n i t i a l b a c t e r i a l l e v e l s f r o m 1 . 3 1 x 1 0 6 a t s t a r t u p

t o 1 . 9 1 x 1 04

C F U / m l d u r i n g t h e t h i r t e e n d a y p e r i o d , r e p r e s e n t i n g a

9 8 . 5 p e r c e n t r e d u c t i o n .

P h a s e I I T e s t i n g

D i p s l i d e s a r e a c o n v e n i e n t f i e l d t e c h n i q u e f o r d e t e r m i n i n g

bacterial numbers in industrial fluids and have been shown to correlate

w e l l w i t h s t a n d a r d p l a t e c o u n t t e c h n i q u e s . T h e r e f o r e , d i p s l i d e s w e r e

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

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

A s s t a t e d a b o v e , P h a s e I I i n v e s t i g a t i o n s w e r e f o r t h e p u r p o s e o f

a s s e s s i n g t h e U V u n i t ’s l o n g t e r m o p e r a t i o n a l c h a r a c t e r i s t i c s

maintenance requirements, and overall microorganism killing

efficiencies. A question arose concerning the best installat i on

a r r a n g e m e n t o n i n t a k e a n d d i s c h a r g e p i p i n g . T h e U V u n i t p i p i n g w a s

i n s t a l l e d i n t h e a i r w a s h e r s u m p a s p o i n t s o u r c e . H o w e v e r , d i p s l i d e s

t a k e n a t t h e w a t e r s u r f a c e o n t h e a i r l e a v i n g s i d e s h o w e d c o n s i d e r a b l y

h i g h e r b a c t e r i a l c e l l c o u n t s t h a n t h o s e t a k e n n e a r t h e r e c i r c u l a t i o n

pump suct ion. B a s e d o n t h e s e t e s t s , a n d o n v i s u a l o b s e r v a t i o n s o f a

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

t h e r e a r o f t h e a i r w a s h e r w a s s u s p e c t e d . T o b e t t e r e v a l u a t e t h e

b a c t e r i a l g r o w t h r a t e i n t h i s a r e a , the a i r washer was shut down and

c l e a n e d o n M a r c h 1 5 , 1 9 8 7 a n d a s e r i e s o f s a m p l e s w e r e c o l l e c t e d f o r

m i c r o b i o l o g i c a l a n a l y s i s b y r e s e a r c h e r s a t U N C - C . C o n t r o l s a m p l e s w e r e

c o l l e c t e d a s i n P h a s e I a t t h e s i t e l o c a t e d n e a r t h e a i r w a s h e r

r e c i r c u l a t i o n p u m p s u c t i o n - a n d d e s i g n a t e d a i r e n t e r i n g ( A E ) . T h e n , t w o

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

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

d e p t h o f o n e ( 1 ) f o o t a n d d e s i g n a t e d A L S a n d A L S S , r e s p e c t i v e l y .

F i g u r e 5 p r e s e n t s t h e s e d a t a d i a g r a m m a t i c a l l y . A s c a n b e s e e n f r o m

F i g u r e 5 , t h e c o n t r o l s a m p l e d i d n o t c h a n g e s i g n i f i c a n t l y f r o m d a t a

c o l l e c t e d d u r i n g P h a s e I . B a c t e r i a l p l a t e c o u n t s f o r t h e f i v e c o n t r o l

A E s a m p l e s r a n g e d f r o m a l o w o f 5 . 8 x 1 0 t o a h i g h o f 7 . 4 x 1 04 4

CFU/ml . However, d a t a c o l l e c t e d o n t h e a i r l e a v i n g s i d e c o n f i r m e d a

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

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

a c c u m u l a t i o n a t t h e s u r f a c e o f l i n t a n d o t h e r f l o a t i n g s o l i d s . The

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

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

T h u s , f u t u r e i n s t a l l a t i o n w h e r e a i r w a s h e r s o f t h i s d e s i g n a r e

e n c o u n t e r e d w i l l i n c o r p o r a t e a h e a d e r p i p e o n t h e U V d i s c h a r g e l i n e t o

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

D a t a c o l l e c t e d b y t h e a u t h o r s f r o m J a n u a r y 2 7 - M a y 2 9 , 1 9 8 7 o n

b a c t e r i a l n u m b e r s u s i n g t h e d i p s l i d e t e c h n i q u e a r e s h o w n i n T a b l e 6 a n d

p r e s e n t e d d i a g r a m m a t i c a l l y i n F i g u r e 6 . B Y c o m p a r i s o n w i t h b a c t e r i a l

numbers shown in Table 4, i t c a n b e s e e n t h a t t h e r e w a s g o o d c o r r e l a t i o n

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

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

w a s m a d e t o q u a n t i f y t h e d i p s l i d e s . I t i s i n t e r e s t i n g t o n o t e t h e

r a t h e r c o n s t a n t k i l l r a t e t h r o u g h t h e m o n t h o f F e b r u a r y ( d i p s l i d e

sample nos. 5 - 1 8 ) e v e n w h e n t h e U V u n i t w a s o p e r a t i n g o n a n a i r w a s h e r

system that had not been cleaned since November 16, 1986 ( a 17 week

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

e v a l u a t i o n o n M a r c h 1 5 , 1 9 8 7 , a n d a n a d d i t i o n a l s h u t d o w n f o r c l e a n i n g

o c c u r r e d o n A p r i l 2 6 , 1 9 8 7 . H o w e v e r , t h e r e d o e s n o t a p p e a r t o b e a n y

c o r r e l a t i o n b e t w e e n t h e s e e v e n t s a n d t h e c e l l c o u n t s . W h a t i s c l e a r i s

t h a t t h e s e d a t a s h o w t h a t t h e U V d i s i n f e c t i o n s y s t e m c a n s u c c e s s f u l l y

m a i n t a i n a n a v e r a g e m i c r o b i a l p o p u l a t i o n d e n s i t y o f 1 0 4i n t h i s a i r

w a s h e r o v e r t i m e . F u r t h e r , i f w e c o m p a r e t h e s e d i p - s l i d e r e s u l t s w i t h

d a t a s h o w n i n T a b l e 3 , w e s e e a n o v e r a l l p e r c e n t k i l l o f 9 9 . 9 9 t o

99.999.

P h a s e I I I a n d I V T e s t i n g

A t t h e c o n c l u s i o n o f t h e s e c o n d p h a s e o f t e s t i n g , i t w a s d e c i d e d t o

e v a l u a t e w h e t h e r a s m a l l e r U V u n i t u s e d i n c o n j u n c t i o n w i t h h y d r o g e n

p e r o x i d e w o u l d a c h i e v e s i m i l a r r e s u l t s . H y d r o g e n p e r o x i d e i n t h e

p r e s e n c e o f U V l i g h t f o r m s a f r e e r a d i c a l s i m i l a r t o o z o n e w h i c h i s

h i g h l y a g g r e s s i v e t o w a r d b a c t e r i a a n d o t h e r o r g a n i c c o n s t i t u e n t s . T h e

c o m b i n a t i o n o f U V a n d h y d r o g e n p e r o x i d e i s c o n s i d e r e d s a f e i n t h a t i t i s

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

I n i t i a l s t u d i e s i n v o l v e d t h e s l u g a d d i t i o n o f t w o ( 2 ) p o u n d s o f 3 5 %

h y d r o g e n p e r o x i d e ( a p p r o x i m a t e l y 2 7 p p m ) w i t h t h e U V u n i t o f f a n d t h e n

w i t h t h e U V u n i t o n . Subsequent analyses o f the coo l ing water showed

r a p i d d i s a p p e a r a n c e o f h y d r o g e n p e r o x i d e f r o m t h e s y s t e m . A f t e r s i x t y

( 6 0 ) m i n u t e s t h e h y d r o g e n p e r o x i d e c o n c e n t r a t i o n w a s b e l o w d e t e c t a b l e

l e v e l s .

B e g i n n i n g o n M a y 5 , 1 9 8 7 , f o u r ( 4 ) o f t h e e i g h t ( 8 ) g e r m i c i d a l

l a m p s i n t h e U V u n i t w e r e t u r n e d o f f . C o n c u r r e n t l y , t w o ( 2 ) p o u n d s p e r

day of 35% hydrogen perox ide was in jec ted by chemica l pump in to the

c o o l i n g w a t e r s u p p l y p r i o r t o t h e U V u n i t . A t imer was employed to

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

m i n u t e t i m e i n t e r v a l o n c e p e r d a y . Samples number 39 - 49 of Table 6

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

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

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

b e t t e r c o n t r o l o f b a c t e r i a l c o n t a m i n a t i o n t h a n e i g h t l a m p s a l o n e .

A M o d e l S M F - 2 4 P . E . P . s a n d f i l t e r w a s i n s t a l l e d j u s t a h e a d o f t h e

U V u n i t o n June 3 r d a n d s t a r t e d u p o n J u n e 9 t h . M e c h a n i c a l p r o b l e m s

w i t h t h e f i l t e r ’s e l e c t r i c a l m o t o r d u r i n g t h e f o l l o w i n g w e e k s p r e c l u d e d

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

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

s u p p l e m e n t a l r e p o r t w i l l b e s u p p l i e d a t a l a t e r d a t e .

V i s u a l O b s e r v a t i o n s

A n i m p o r t a n t a s p e c t o f t h e s e e v a l u a t i o n s a r e t h e e f f e c t s o f U V

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

w a t e r . O b s e r v a t i o n h a s s h o w n t h a t w a t e r q u a l i t y h a s i m p r o v e d o v e r t h e

t e s t p e r i o d . A t t h e o n s e t , a n o t i c e a b l e o d o r w a s e v i d e n t u p o n e n t e r i n g

t h e a i r w a s h e r r o o m . T h i s o d o r w a s e l i m i n a t e d w i t h i n t h e f i r s t w e e k

a f t e r s t a r t u p o f U V d i s i n f e c t i o n . F o a m i n g w a s a l s o s i g n i f i c a n t l y

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

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

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

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

c l e a r e d t o t r a n s p a r e n c y t h r e e t o f o u r w e e k s a f t e r U V d i s i n f e c t i o n b e g a n .

F u r t h e r , slime accumulation on the sump walls a n d a l s o o n t h e f i l t e r

s c r e e n s p r i o r t o t h e a i r w a s h e r s r e c i r c u l a t i o n p u m p i n t a k e w a s

s i g n i f i c a n t l y r e d u c e d . I n ‘g e n e r a l , t h e w a t e r q u a l i t y o f a i r w a s h e r N o .

1 w a s e x t r e m e l y g o o d d u r i n g p h a s e I , w i t h a v e r y c l e a r , c o l o r l e s s w a t e r

i n c i r c u l a t i o n a t a l l t i m e s .

UV Unit Maintenance Requirements

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

r e c i r c u l a t i o n w a t e r i n a w o r s t c a s e s c e n a r i o , c o n c e r n w a s e x p r e s s e d f o r

t h e m a i n t e n a n c e r e q u i r e d t o k e e p t h e U V s y s t e m o p e r a t i o n a l . However,

a f t e r n e a r l y s i x ( 6 ) m o n t h s o f c o n t i n u o u s o p e r a t i o n , t h e T e f l o n b a s e d U V

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

( s e e F i g u r e 1 ) . I n f a c t t h e o n l y m a i n t e n a n c e t h e s y s t e m h a s r e q u i r e d

t h r o u g h o u t t h e p r o j e c t h a s b e e n w e e k l y p u r g i n g o f t h e L a k o s S e p a r a t o r

( w h i c h w i l l n o t b e u s e d i n f u t u r e i n s t a l l a t i o n s o n a i r w a s h e r s b e c a u s e

p a r t i c l e w e i g h t t y p i c a l i n t h i s a p p l i c a t i o n a r e t o o l i g h t ) , r e p l a c e m e n t

o f a f a i l e d p u m p s t a r t e r s w i t c h ( M a r c h 1 6 , 1 9 8 7 ) , a n d r e m o v a l o f

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

t u b e ( F e b r u a r y 1 8 , A p r i l 1 4 , a n d J u n e 3 , 1 9 8 7 ) . T h i s l a t t e r r e q u i r e d

a p p r o x i m a t e l y t e n ( 1 0 ) m i n u t e s e a c h t i m e t o a c c o m p l i s h a n d d i d n o t

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

d u s t f i l t e r s o n t h e U V r e a c t o r ’s c o o l i n g a i r i n t a k e

ports. There no other maintenance required during the test period.

However, the unit should be included in the plant’s routine i n s p e c t i o n

program. F o r i n s t a n c e , i n s p e c t i o n s h o u l d b e made of the

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

L E D l a m p s i n s i d e t h e c o n t r o l p a n e l ) a n d t h e i n s i d e o f t h e T e f l o n t u b e

s h o u l d b e s w a b b e d w i t h s o a p y w a t e r a t l e a s t o n c e p e r y e a r .

i n s t a l l a t i o n o f

and maintenance

C a p i t a l a n d O p e r a t i o n C o s t - - P a y B a c k

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

a c h i e v e l o n g t e r m e f f e c t i v e a n d e c o n o m i c a l c o n t r o l o f w a t e r b o r n e

m i c r o b i a l c o n t a m i n a t i o n w i t h o u t c h e m i c a l t r e a t m e n t . T h i s c a n b e

a c c o m p l i s h e d b y u s i n g a p r o p e r l y s i z e d T e f l o n b a s e d U V u n i t . S i z i n g o f

the UV uni t to a par t icu lar sys tem is based on the to ta l water vo lume in

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

t h e U V a b s o r p t i o n c o e f f i c i e n t p a r t i c u l a r t o e a c h s y s t e m . Once these

t w o f a c t s a r e k n o w n , i t i s n o t d i f f i c u l t t o p r o p e r l y s i z e t h e U V u n i t .

A s s u m i n g a " t y p i c a l " a b s o r p t i o n c o e f f i c i e n t , a w a t e r v o l u m e t u r n o v e r

t i m e t h r o u g h t h e U V u n i t o f 5 0 t o 7 5 m i n u t e s w i l l g i v e a b a l l p a r k s i z e

o f t h e U V u n i t r e q u i r e d f o r i n d u s t r i a l a i r w a s h e r s . F o r e x a m p l e , a n a i r

w a s h e r w i t h a t o t a l w a t e r v o l u m e o f 5 , 0 0 0 g a l l o n s w i l l r e q u i r e a 1 0 0 G P M

U V u n i t a n d a c h i e v e a t u r n o v e r t i m e o f 5 0 m i n u t e s . F o r c o o l i n g t o w e r s ,

a t u r n o v e r t i m e o f 1 0 0 t o 1 2 5 m i n u t e s w i l l g e n e r a l l y b e a d e q u a t e . Thus,

t h e s a m e 1 0 0 G P M U V u n i t w i l l t r e a t a c o o l i n g t o w e r w i t h a w a t e r v o l u m e

o f 1 0 , 0 0 0 t o 1 2 , 5 0 0 g a l l o n s . B u t a g a i n , m a k e u p w a t e r q u a l i t y , l o c a t i o n

o f t h e c o o l i n g s y s t e m , e t c . , w i l l a f f e c t t h e U V a b s o r p t i o n c o e f f i c i e n t

a n d t h u s , t h e s i z e o f t h e U V u n i t r e q u i r e d t o p r o v i d e s a t i s f a c t o r y

c o n t r o l o f m i c r o b i a l g r o w t h . T h i s m a k e s f i e l d i n s p e c t i o n o f a c o o l i n g

system mandatory.

T y p i c a l p a y b a c k p e r i o d s f o r t h e u s e o f t h e T e f l o n b a s e d U l t r a v i o l e t

D i s i n f e c t i o n s y s t e m m a n u f a c t u r e d b y H y d r a S y s t e m s , I n c . w i l l b e b e t w e e n

e l e v e n ( 1 1 ) t o e i g h t e e n ( 1 8 ) m o n t h s . The cost of a 100 GPM unit will be

$ 4 , 5 6 0 . 0 0 , w h i l e a 5 0 G P M u n i t w i l l c o s t $ 2 , 3 0 0 . 0 0 . T y p i c a l t u r n - k e y

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

r u n s , a n d e l e c t r i c a l h o o k u p ) a n d s t a r t - u p m a y a d d u p t o $ 1 , 5 0 0 . 0 0 .

T a b l e 7 b e l o w s h o w s t h e p a y b a c k a n a l y s e s f o r t h i s p a r t i c u l a r a i r w a s h e r

i n s t a l l a t i o n . A s can b e s e e n , p a y b a c k o f t h e c a p i t a l c o s t o f t h e U V

u n i t v e r s u s c h e m i c a l t r e a t m e n t i s r e a l i z e d i n o n l y 1 . 7 7 y e a r s .

Inherent Advantages of UV Disinfection us Chemical Treatment

T h e r e a r e a d d i t i o n a l a d v a n t a g e s t o t h e u s e o f U V d i s i n f e c t i o n o v e r

t r a d i t i o n a l c h e m i c a l t r e a t m e n t . M a n y o f t h e s e m a y b e m o r e s i g n i f i c a n t

i n t h e d e c i s i o n t o u s e U V a s a n a l t e r n a t i v e m e t h o d f o r t h e c o n t r o l o f

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

p e r i o d . T h e f o l l o w i n g a r e s o m e o f t h e i n h e r e n t a d v a n t a g e s o f u s i n g t h e

U V l i g h t u n i t o v e r c h e m i c a l b i o c i d e s f o r m i c r o b i a l c o n t r o l :

1 . ) E l i m i n a t e s t h e e x p o s u r e o f t h e m a i n t e n a n c e o p e r a t o r t o p o t e n t i a l l y

dangerous chemicals .

2 . ) E l i m i n a t e s t h e d i s c h a r g e o f c h e m i c a l b i o c i d e s i n t o s t o r m d r a i n s o r

s a n i t a r y s e w e r s y s t e m s .

3 . ) E l i m i n a t e s t h e c o s t o f m a n p o w e r r e q u i r e d t o a d d t h e b i o c i d e s a n d

e v a l u a t e t h e i r p e r f o r m a n c e .

4 . ) E l i m i n a t e s a n y c h e m i c a l b i o c i d e f r o m t h e a i r r e t u r n i n g t o t h e

p r o d u c t i o n a r e a . ( M a n y b i o c i d e s h a v e o b n o x i o u s o r i r r i t a t i n g o d o r s

a n d m a y a l s o b e c o r r o s i v e t o t h e d u c t w o r k a n d f a n s . )

5 . ) E l i m i n a t e s p r o b l e m s o f f o a m i n g c a u s e d b y s o m e c h e m i c a l b i o c i d e s .

6 . ) E l i m i n a t e s u n d e s i r a b l e p H s w i n g s c a u s e d b y c e r t a i n b i o c i d e s ,

e s p e c i a l l y t h e c h l o r i n e / b r o m i n e d o n o r s .

7 . ) E l i m i n a t e s u n d e s i r a b l e c o m p a t i b i l i t y p r o b l e m s b e t w e e n b i o c i d e s a n d

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

" ion control ".

8 . ) R e d u c e s t h e o b j e c t i o n a b l e o d o r s a s s o c i a t e d w i t h m i c r o b i a l f o u l i n g

o f m i s t e l i m i n a t o r b l a d e s , b a s i n w a l l s , e t c .

9 . ) P r o v i d e s m o r e c o n s i s t e n t c o n t r o l o f a l l t y p e s o f m i c r o o r g a n i s m s

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

c o n t a m i n a n t .

1 0 . ) P r o v i d e s m o r e e f f i c i e n t o p e r a t i o n o f r e f r i g e r a t i o n e q u i p m e n t

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

11. ) R e d u c e s d o w n t i m e r e q u i r e d t o c l e a n s l i m e f o u l e d e q u i p m e n t .

CONCLUSIONS

1 . ) T h e U l t r a v i o l e t D i s i n f e c t i o n U n i t e m p l o y e d o n t h i s t e x t i l e a i r

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

a n d m a i n t a i n a t a l e v e l o f 1 0 T h i s l e v e l w a s a n a v e r a g e4

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

2 . ) M a i n t e n a n c e o f t h e u l t r a v i o l e t d i s i n f e c t i o n u n i t w a s n o t r e q u i r e d

t o k e e p t h e u n i t o p e r a t i n g e f f i c i e n t l y . O v e r t h e s i x m o n t h

e v a l u a t i o n p e r i o d , w e t t e d s u r f a c e s o f t h e U V u n i t d i d n o t r e q u i r e

c l e a n i n g .

3 . ) T h e u s e o f a s m a l l e r u l t r a v i o l e t d i s i n f e c t i o n u n i t ( l / 2 t h e n u m b e r

of germic ida l lamps or a 50 GPM UV uni t ) and employ ing 35% hydrogen.

p e r o x i d e a t a f e e d r a t e o f t w o ( 2 ) p o u n d s p e r d a y ( $ 6 . 3 0 / w e e k )

y i e l d e d s i m i l a r r e s u l t s . T h e r e f o r e , t h i s i n s t a l l a t i o n m i g h t

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

a d d i t i o n a l $ 3 6 0 . 0 0 f o r c h e m i c a l f e e d p u m p , $ 4 5 . 0 0 f o r a 1 0 g a l l o n

t a n k a n d $ 3 2 7 . 6 0 / y r i n 3 5 % h y d r o g e n p e r o x i d e .

4 . ) E v a l u a t i o n o f a n u l t r a v i o l e t d i s i n f e c t i o n u n i t u s e d i n c o n j u n c t i o n

w i t h a s a n d f i l t e r i s - s t i l l i n p r o g r e s s . ( A s u p p l e m e n t a l r e p o r t o n

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

APPENDIX

FIGURE 1: SCHEMATIC OF 100-lX UV DISINFECTION UNIT

13

12

11

10

9

8

7

6

5

4

3

2

1

0

l =TPC

0 1 2 3 4 5 6 12 18 24

TIME POST UV STARTUP [HOURS]

13

11

10

9

l =TPC

0

0 1 2 3 4 5 6 7 8 9 10 11 12 13

T I M E P O S T U V S T A R T U P[ D A Y S]

6

5

4

3

2

1

0

A = AIR EXIT - SURFACE

0 1 3 9 15 2 2

T I M E P O S T u v S T A R T U P [ D A Y S ]

FIGURE 6: LONG TERM EFFECT OF ULTRAVIOLET DISINFECTION ON

TPC FROM AIR WASHER NO. 1

DIP SLIDE BACTERIA COUNTS PER ML

TABLE 1: HSI MODEL 100-LX UNIT SPECIFICATIONS

- E n c l o s u r e : 3 0 4 s t a i n l e s s s t e e l , 1 6 g a u g e-Max. Flow, GPM: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 125- D i m e n s i o n s , I N . ( L x W x H ) : . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85x 12x 12- I n l e t & O u t l e t , I N . : . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 N . P . T . F- S h i p p i n g W t . , L B S . : . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 350- N o . T e f l o n T u b e s : . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1- T e f l o n T u b e , D i a . , I N . : . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 . 3 5- T e f l o n T u b e , T h i c k n e s s , IN: . . . . . . . . . . . . . . . . . . . . . . . . . 0 .030- T e f l o n T u b e , L e n g t h , I N : . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 8 . 5-No. Lamps: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-Type of Lamp: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . G64T5L-Lamp output , micro-watt-sec/cm2 : . . . . . . . . . . . . . . . . . . . . 30,000-Lamp Wave Length, nm: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 253.7- P o w e r , W a t t s : . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 840- P o w e r , U o l t s / H e r t z : . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 120160-Phase: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1- N o . o f F a n s : . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2- N o . o f B a l l a s t : . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

TABLE 2: AIR HANDLING SYSTEM NO. 1 SPECIFICATIONS ANDULTRAVIOLET SYSTEM DESIGN CRITERIA

Cooling System Water Volume:- C o o l i n g T o w e r N o . 1, 350 T o n : ( g a l ) . . . . . . . . . . . . . 4 , 6 5 3- P i p i n g s y s t e m : ( g a l ) . . . . . . . . . . . . . . . . . . . 147- E x c h a n g e r : ( g a l ) . . . . . . . . . . . . . . . . . . . . .200- T o t a l W a t e r V o l u m e , T o w e r N o . 1 : ( g a l ) . . . . . . . . 5 ,000- A i r W a s h e r N o . 1 : ( g a l ) . . . . . . . . . . . . . . . . . 4 , 0 9 5- P i p i n g S y s t e m : ( g a l ) . . . . . . . . . . . . . . . . . . . . . . 393- C h i l l e r : (gal ) . . . . . . . . . . . . . . . . . . . . . . . . 200-Total Water Volume, Air Washer No.:(gal) ...............................4,688

D i s i n f e c t a n t S y s t e m D e s i g n P a r a m e t e r s :-Cooling Tower No. 1:

- R e q u i r e d W a t e r T u r n o v e r : ( m i n ) . . . . . . . . . . . . . . . . . . .- F l o w , T o t a l : ( w m ) . . . . . . . . . . . . . . . . . . . . . .- P r e s s u r e : ( p s i g ) . . . . . . . . . . . . . . . . . . . . . . . . . .-Water Temperature: (F, max) . . . . . . . . . . . . . . . . . . . . . . . . . . .- M i c r o o r g a n i s m D e s t r u c t i o n : ( % ) . . . . . . . . . . . . . . . . . . .

- A i r W a s h e r N o . 1 :- R e q u i r e d W a t e r T u r n o v e r : ( m i n ) , . . . . . . . . . . . . . . . . .- F l o w , T o t a l : (gpm) . . . . . . . . . . . . . . . . . . . . . . . . . . . .- P r e s s u r e : ( p s i g ) . . . . . . . . . . . . . . . . . . . . . . . .-Water Temperature: (F, max) . . . . . . . . . . . . . . . . . . . . . .- M i c r o o r g a n i s m D e s t r u c t i o n : ( % )

50100

30110

99.9+

47100

30110

99.9+

TABLE 3:PRELIMINARY MICROBIAL ANALYSIS BY DIP SLIDE TECHNIQUE a

SAMPLE BACTERIA b

DATE TIME C F U / m l )- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

1 1 / 0 5 / 8 6 13:00 10 8

1 1 / 1 2 / 8 6 13:30 10 8

11/20/86 08:30 10 9

11/25 /86 15:30 10 5

1 2 / l 2 / 8 6 10:00 1 0 9

12/16/86 15:00 10 8

12/16/86 17:30 105.

1 2 / l 9 / 8 6 09:30 109

12 /23 /86 13:30 106

12/29/86 09:30 107

12 /29 /86 13:30 105

12/30/86 14:00 10 7

a S e l e c t i c u l t - T T C , S c o t t L a b s , F i s k e v i l l e , R . I .b C o l o n y F o r m i n g U n i t s P e r M i l l i l i t e r ( N o a t t e m p t

w a s m a d e t o q u a n t i t a t e t h e s e d i p s l i d e s ) .

TABLE 4: SUMMARY OF RAW DATA COLLECTED IN PHASE 1 a

TIME( h r )

TPC( b )

pH TURB ABSOR CDND HARD ALK Cl( c ) ( d ) ( e ) ( f ) ( g ) ( h )

0 1.31 x 10 6 7 . 5

1 2 .34 x 10 5 7 . 7

2 2 .23 x 10 5 7 . 5

3 1.69 x 10 5 7 . 8

4 1.49 x 10 5 7 . 8

5 1.32 x 10 5 7 . 5

6 1.14 x 10 5 7 . 6

12 8 .35 x 10 4 7 . 4

18 9.80 x 10 4 7 . 8

24 7.20 x 10 4 7 . 6

48 6.70 x 10 4 7 . 5

72 8.20 x 10 4 7 . 5

120 1.02 x 10 4 7 . 9

144 2 .29 x 10 4 8 . 0

168 1.74 x 10 4 7 . 8

240 5.30 x 10 4 7 . 6

312 1.91 x 10 4 8 . 4

2 0.240 450 43 81 28.0 108 10

5 0.235 400 39 77 28.0 107 9

7 0.235 300 37 77 27.5 162 90

7 0 .235 450 35 77 27.0 150 52

5 0.230 450 31 79 27.5 142 38

3 0.220 450 35 79 28.0 121 10

3 0.220 450 34 76 28.5 173 18

3 0.215 250 34 78 30.5 153 4

2 0.215 450 34 80 29.0 165 0

5 0.200 400 33 79 30.0 125 4

5 0.171 250 38 82 32.5 275 124

3 0.171 150 40 79 34.5 275 154

5 0.159 550 41 86 38.0 277 10

2 0.146 650 43 81 39.0 256 24

3 0.127 450 44 76 40.0 291 34

1 0.145 600 45 1330 39.0 402 179

ND 0.170 750 51 1505 41 .o 422 103

TS TVS( i ) Cj>

- - - - - - - - -

D a t a r e p r e s e n t a v e r a g e o f d u p l i c a t e a n a l y s i s .Tota l P late Counts (Tota l Bat ter i a /ml 1 .T u r b i d i t y ( F T U ) .U l t r a v i o l e t A b s o r b a n c e a t 2 5 3 . 7 n m .C o n d u c t i v i t y , ( u m h o s ) .Total Hardness as CaC03.A l k a l i n i t y a s C a C 0 3 .C l o r i d e a s N a C l .T o t a l S o l i d s ( m g / l ) .Total Volital Solids (mg/l).

TABLE 5: SOLIDS ANALYSIS

TIME( h r )

0

1

2

3

4

5

6

12.

18

24

48

72

120

144

168

240

312

TS b TVS C

( m g / l ) (mg/l 1

108 10

107 9

162 90

150 52

142 38

121 10

173 18

153 4

165 0

125 4

275 124

275 154

277 10

256 24

291 34

402 179

422 103

% TVS d

( O r g a n i c s )

9

8

56

35

27

8

10

3

0

3

45

56

4

9

12

45

24

a Data represent average of duplicate analysis.b Total Solids.c Total Volitle Solids.d Percent Total Volitle Solids = Organics.

TABLE 6: MICROBIAL ANALYSIS BY DIP SLIDE TECHNIQUE a

SAMPLE DATENO.

SAMPLEN O .

1 0 1 / 2 7 / 8 7

2 0 1 / 2 8 / 8 7

3 0 1 / 2 9 / 8 7

4 0 1 / 3 0 / 8 7

5 0 2 / 0 1 / 8 7

6 0 2 / 0 2 / 8 7

7 0 2 / 0 3 / 8 7

8 0 2 / 0 6 / 8 7

9 0 2 / 0 9 / 8 7

10 0 2 / 1 6 / 8 7

11 0 2 / 1 7 / 8 7

12 0 2 / 1 8 / 8 7

13 0 2 / 1 9 / 8 7

14 0 2 / 2 0 / 8 7

15 0 2 / 2 1 / 8 7

16 0 2 / 2 2 / 8 7

17 0 2 / 2 3 / 8 7

18 0 2 / 2 5 / 8 7

19 0 3 / 0 2 / 8 7

20 0 3 / 0 4 / 8 7

21 0 3 / 0 5 / 8 7

22 0 3 / 0 9 / 8 7

23 0 3 / 1 0 / 8 7

24 0 3 / 1 1 / 8 7

25 0 3 / 1 2 / 8 7

26 0 3 / 1 7 / 8 7

BACTERIA b

(CFU/ml)

1 0 6

10 4

10 4

1 0 4

1 0 4

1 0 4

10 4

1 0 4

1 0 4

1 0 4

1 0 4

10 4

1 0 4

10 4

1 0 4

1 0 4

1 0 4

1 0 4

1 0 5

1 0 4

1 0 5

l - 0 4

1 0 3

1 0 3

10 4

1 0 4

27

28

29

30

31

32

33

34

35

36

37

38

39

40

41

42

43

44

45

46

47

48

49

50

51

52

DATE

0 3 / 1 8 / 8 7

0 3 / 2 0 / 8 7

0 3 / 2 6 / 8 7

0 4 / 0 2 / 8 7

0 4 / 0 7 / 8 7

0 4 / 1 0 / 8 7

0 4 / 1 4 / 8 7

0 4 / 2 3 / 8 7

0 4 / 2 4 / 8 7

0 4 / 2 4 / 8 7

0 4 / 3 0 / 8 7

0 5 / 0 1 / 8 7

05105187

0 5 / 0 6 / 8 7

0 5 / 0 7 / 8 7

0 5 / 0 8 / 8 7

0 5 / 0 9 / 8 7

0 5 / 1 1 / 8 7

0 5 / 1 3 / 8 7

0 5 / 1 8 / 8 7

0 5 / 2 0 / 8 7

0 5 / 2 1 / 8 7

0 5 / 2 3 / 8 7

0 5 / 2 6 / 8 7

0 5 / 2 7 / 8 7

0 5 / 2 9 / 8 7

BACTERIA b

(CFU/ml)

1 0 4

10 4

41 0

1 0 4

1 0 6

41 0

310 3

1 0 3

41 0

41 0

41 0

41 0

41 0

31 0

31 0

41 0

1 0 3

10 3

1 0 4

41 0

10 4

1 0 3

1 0 4

10 4

51 0

51 0

a S e l e c t i c u l t - T T C , S c o t t L a b s , F i s k e v i l l e R . I .b C o l o n y F o r m i n g U n i t s P e r M i l l i l i t e r ( N o a t t e m p t

w a s m a d e t o q u a n t i t a t e t h e s e d i p s l i d e s ) .

TABLE 7: PAYBACK ANALYSIS - 100-LX UV UNIT

C a p i t a l C o s t U V U n i t : . . . . . . . . . . . . . . . $ 4,560

Flow Capac i ty , GPM: . . . . . . . . . . . . . . . . . 100

Power Usage, Watts: . . . . . . . . . . . . . . . . 840

Annual Lamp Replacement Cost( c u r r e n t p r i c e s ) : . . . . . . . . . . . . . . . . . . $ 544

Annual Energy Cost(@ $0.035 / KW-HR): . . . . . . . . . . . . . . $ 258

A n n u a l O p e r a t i n g C o s t : . . . . . . . . . . . . . . . . . . . . . . . . $ 802

. . . . . . . . . . . . . . . . . . . . . $ 3,450

Dif ference between UV & Chemical TreatmentA n n u a l O p e r a t i n g C o s t : . . . . . . . . . . . . . . . . . . . . . $ 2 ,578

P a y b a c k O f C a p i t a l C o s t : . . . . . . . . . . . . . . . . . . . . . . . . 1 . 7 7 y r .

* B a s e d o n a n a v e r a g e b i o c i d e c o s t o f $ 6 6 . 3 5 / w e e k = $ 3 , 4 5 0 , 0 0 / y r .

ultraviolet light disinfection of water in a textile air ...infohouse.p2ric.org/ref/03/02919.pdf ·...

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