EPA 811-R-96-002
September 1996
ULTRAVIOLET LIGHT DISINFECTION
TECHNOLOGY IN DRINKING WATER
APPLICATION—AN OVERVIEW
Presented to:
U.S. Environmental Protection Agency
Office of Ground Water and Drinking Water
401 M Street, SW
Washington, DC 20460
Presented by:
Science Applications International Corporation
1710 Goodridge Drive
McLean, VA 22102
EPA Contract No. 68-C3-0365; Work Assignment No. 2-1
SAIC Project No. 01-0833-07-4828-000
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DISCLAIMER
The mention of trade names, companies, or products does not constitute and should not be
interpreted as an endorsement, approval, or recommendation for use.
UV Light Disinfection Technology in
Drinking Water Application—An Overview.
Final—September 1996
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- This report has been reviewed in accordance with the U.S. Environmental Protection Agency's peer and
administrative review policies and approved for publication. .This report was prepared by Science Applications
International Corporation (SAIC) under the auspices of the U.S. Environmental Protection Agency's (USEPA) Office
of Ground Water and Drinking Water (OGWDW), represented by Mr. Marc Parrotta (Project Manager). SAIC
wishes to gratefully acknowledge the support of the Project Manager, Mr. Marc Parrotta. SAIC Contract No. 68-C3-
0365, Work Assignment No. 2-1, SAIC Project No. 01-0833-07-4828-000. SAIC contract and work assignment
managers are James Parker, Contract Project Manager; andl Mark Klingenstein, Work Assignment Manager.
Individuals who prepared this report are Faysal Bekdash, PhJX, Consultant; Lynn Kurth, Senior Environmental
Scientist; ,and Lee Solomon, Junior Environmental Engineer. .'' •
UV Light Disinfection Technology in
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ACKNOWLEDGEMENT
The USEPA would like to thank' the following individuals for providing valuable information, comments and
support: Mr. Vmce Monaco, Section Chief, Bureau of Drinking Water, Department of Environmental Protection
New Jersey State; Mr. David Leland, Mr, Gary Burnett, and Ms. Kari Salis of the Drinking Water Division'
Department of Human Resources, Oregon, State; Ms. Dawn Kristof of the Water1 and Wastewater Equipment
Manufacturer s Association, Inc. (WWEMA); Dr. Joyce Donohue and Mr. Bruce Bartley of the National SanLion
fT w°n,^ ^ !Tfrnal: ^ J°Seph HaniSOn °f ^ Water °-Uality Ass^iation (WQA); Mr. Moctar Toure
qf the World Bank and Mr. Le Dit Bokary Guindo of the United Nations Food and Agriculture Organization (FAOV
Dr. Bruce Mac er, Mr. Jon Merkle and Mr. Barry Pollock of USEPA Region IX; Mr. Stan Calow of the Drinking
Water Ground Water Management Branch USEPA Region.VH; Mr. Gerald Opatz of USEPA Region X; Dr. Viola
Young-Harvath of OGWDW, USEPA; Mr. Bak.Srikanth of Aquafme; Mr. Hilary Boehme and Ms. Ann Wysocki
of Atlantic Ultrav,olet; Mr. Jesse Rodriguez of Ideal Horizons; Mr. Mervyh Bowen of Infilco-Degremonf Mr
Charles Readings of Safe Water Solutions; and Dr. William Cairns of Trojan Technologies.
to0 thank % foUowing peer reviewers: Dr. Stephen Edberg of Yale University, Dr. Thomas'
Atherholt of New Jersey State Division of Science and Research, Dr. Rick Sakaji and Mr. Robert Hultquist P E
of CalrformaState Department of Health Services, and Mr. John Wroblewski, Chief of Engineering at Pennsylvania
e °^n J^°teCti0n- ^ J°hn DavidS°n' °ffice °f Policy' PlanninS •«» Evaluation,
UV Light Disinfection Technology in • '- - : ~" '
Drinking Water Application-An Overview Final-September 1996
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PRELUDE
The objective of this report is to support the United States Environmental Protection Agency's (USEPA)
Office of Ground Water and Drinking Water (OGWDW) in its efforts to develop the Ground Water
Disinfection Rule (GWDR). According to USEPA's databases on the number of public water systems in
the United States, there are approximately 178,000 water supply systems servuig fewer than 3,300 people.
Of the 178,000 systems, approximately 130,000 systems are transient nori-community (TNC) and non-
transient non-community (NTNC) ground water supply systems with little or no distribution systems.
\ . " . ' .,-.•- . '
These TNC and NTNC ground water systems may be amenable to alternative disinfection technology
applications. This report presents a preh'minary investigation of ultraviolet light (also called ultraviolet
radiation) use as a ground water disinfection technology. •
To investigate the availability, viability, and costs of ultraviolet equipment for use at potable water
supplies and to obtain current information on equipment costs and operation and maintenance practices,
the USEPA contacted equipment manufacturers or manufacturer representatives, the Water and Wastewater
Equipment Manufacturer's Association, Inc. (WWEMA), the American Water Works Association
(AWWA), the National Sanitation Foundation (NSF) International, the Water Quality Association (WQA),
the Food and Drag Administration (FDA), the National Institute for Occupational Safety and Health
(NIOSH), and universities involved in ultraviolet light research. The USEPA conducted an indepth
literature search to determine ultraviolet light inactivation rates for specific microorganisms, including
Rotavirus, poliovirus, hepatitis A virus, bacteria, and protozoa such as Giardia lamblia,. and
Cryptosporidium parvum. Information on inactivation rates provided by the ultraviolet light industry are
presented next to the inactivation rates reported in the scientific literature. The juxtaposition of scientific
and nonscientific information is intended to show points, of agreement and disagreement between
manufacturers' information and peer-reviewed research data. Information collected regarding ultraviolet
, light pptential for destruction of volatile organic compounds (VOCs) and other priority organics is
presented in Appendix B of this report. <
This report contains^ list of abbreviations, conversion units, and definitions; additionally, chapters 1, 2,
3, and 4 and appendices A and B have each a separate list of references. Subsequent to this Prelude, this
report is arranged in the following format: - .
UV Light Disinfection Technology in
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Prelude
• EXECUTIVE SUMMARY
• CHAPTER 1. BACKGROUND—Presents historic and scientific background information and
a general description of the technology. Also, the chapter provides an assessment of the
availability of appropriate ultraviolet equipment in the United States of America, and presents
information on existing use guidelines.
• CHAPTER 2. ASSESSMENT OF ULTRAVIOLET LIGHT EFFICACY, VIABILITY AND
OPERATIONAL FACTORS—Discusses ultraviolet light disinfection efficacy (i.e., inactivation
rates and issues that surround ultraviolet light applications for drinking treatment in a
groundwater setting, and by-products formation). Issues related to the practicality of using
ultraviolet light in a ground water setting with an emphasis on small systems are presented.
Factors such as .operating procedures and requirements, maintenance requirements, installation
features, and design elements are considered. This chapter presents a description of ultraviolet
light technology (including equipment operational factors, water quality considerations,
hydraulic design considerations, and design considerations specific to small systems), as wen
as a summary with an emphasis on ultraviolet light viability for small drinking water systems
based on the findings and data relative to operational factors.
' CHAPTER 3. EVALUATION OF ULTRAVIOLET SYSTEMS COSTS AND COMPARISON
TO OTHER DISINFECTION TECHNOLOGIES—Provides an assessment of the costs of
using ultraviolet light alone and in combination with, or in lieu of, other disinfectants. This
chapter presents findings to date regarding costs associated with using ultraviolet light to
disinfect ground water sources for five design flow categories (0.024 MOD, 0.087 MOD
0.270 MGD, 0.650 MOD and 1.800 MOD). .
CHAPTER 4. CASE STUDIES—Presents information from sources in the field where
ultraviolet light has been applied. The majority of the presented case studies are non-
community ground water systems.
CHAPTER 5. SUMMARY OF FINDINGS—Offers a summary of the findings on the issues
discussed in the report.
APPENDIX A. OTHER ULTRAVIOLET-RELATED DRINKING WATER DISINFECTION
TECHNIQUES—Presents information available on newly applied ultraviolet-related
disinfection techniques and other ultraviolet-related disinfection techniques that are at the
experimental stage.
APPENDIX B. ORGANICS DESTRUCTION^-Presents an analysis of ultraviolet radiation's
potential for the destruction of VOCs and other priority organics in drinking water.
APPENDIX C. QUESTIONNAIRE USED FOR STATE INQUIRY AND AS GUIDE IN
TELEPHONE INQUIRIES—Presents a list of questions used as a guide to collect information
on ultraviolet systems, water quality, and costs. ,
APPENDIX D. REGULATIONS AND STANDARDS FOR DRINKING WATER
DISINFECTION USING ULTRAVIOLET LIGHT—Provides available regulations and
standards regarding the use of ultraviolet light for drinking water disinfection. A
UV Light Disinfection Technology in
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ABBREVIATIONS LIST
oc. Coefficient of Absorbance
e Molar decadic absorption coefficient in L/mol/cm
t> Frequency in hertz or per second
A. Wavelength in m
,a.u. : ,. Absorbance Units
AA Activated Alumina
ANSI American National Standards Institute
AOC Assimilable Organic Carbon
APHA American Public Health Association
AU Cprp. Atlantic Ultraviolet Corporation
ATCC American Type Culture Collection,
AWWA American Water Works Association
AWWARF American Water Works Association Research Foundation
B(a)P 3,4-benzo(a)pyrene
BAT Best Available Technology -
BDCM Bromodichloromethane .
BOD Biochemical Oxygen Demand
c Speed of light
c/kgal Cents per thousand gallons ' . -
C Concentration of chemical disinfectant in mg/L
C/F Coagulation/Filtration
C of A Coefficient of Absorbance
CC Corrosion Control
CDC Centers for Disease Control
CPU Colony Forming Units
CSTR Continuous Flow Stirred Tank Reactor
CWS Community Water Supply
d Distance .
DBCP Dibromochloro propane . „
D/DF Direct and Diatomite Filtration
DHEW Department of Health, Education and Welfare.
DOC Dissolved Organic Carbon
DRCM Differential Reinforced Clostridial Medium
eV Electron volt
E Energy
ENR Engineering News Record
ENRCC Engineering News Record Construction Cost
EU . European Union
PDA Food and Drug Administration
GAC Granular Activated Carbon
gmol Gram Mole
gpm Gallons per minute
GWDR Ground Water Disinfection Rule
h Planck's Constant Number
HAV Hepatitis A Virus '
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Abbreviations List (Continued)
HOPE High Density Polyethlyene
HHS Department of Health and Human Services
HPC Heterotrophic Plate Count
i Intensity of ultraviolet light
IE Ion Exchange
J Joule
k Rate constant
k$ Thousand dollars
kgpd Thousand gallons per day
KWhr Kilowatt hour .
KeV Kilo electron volt
LED Light-Emitting Diode
L/S Liters per Second
LS Lime Softening
M Molar Concentration
MCL Maximum Contaminant Level
MCLG Maximum Contaminant Levels Goal
mg/L Milligrams per Liter
MOD Million Gallons per Day
MIB 2-methylisoborneol
mol Mole
MPN Most Probable Number
MS Male Specific
mWs/cm2 Milliwatts Second per Square Centimeter
MX 3-chloro-4(dichloromethyl)-5-hydroxy-2(5H)-furanone '
N Surviving bacterial population after exposure to ultraviolet light
NG No'Growth
NCW Non-Community Water
NIOSH . National Institute of Occupational Health and Safety
nm Nanometer 10'9 meter
No Initial bacterial population
NOM Natural Organic Matter
NPDWR National Primary Drinking Water Regulations
NSF National Sanitation Foundation International
NTNC Non-Transient Non-Community
NTU Nephelometric Turbidity Units
NWRI National Water Research Institute .
ODHR Oregon Department of Human Resources
OGWDW Office of Ground Water and Drinking Water
ORP Oxidation Reduction Potential
O&M Operation and Maintenance
OX Oxidation
PAH Polyaromatic hydrocarbon
PCB Polychlorinated biphenyl
PCE Perchloroethylene, tetrachloroethylene
PFR Plug-Flow Reactor
PHCO Photoassisted Heterogeneous Catalytic Oxidation
POE Point of Entry
POM Particulate Organic Matter
POU Point of Use
UV Light Disinfection Technology in
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Abbreviations List (Continued)
PPPI Producer Prices and Price Indexes
PSSM Point Source Summation Method
PTA . Packed Tower Aeration
PVC , , Polyvinyl Chloride
PWS Public Water System .'" ^
RAD Radiation Absorbed Dose
RCRA Resource Conservation and Recovery Act
RO Reverse Osmosis
RTD Residence Time, Distribution
SAIC Science Applications International Corporation
SDWIS Safe Drinking Water Information System
sec Second
SWTR Surface Water Treatment Rule
t Time
TCA 1,1,1-Trichloroethane, methyl chloroform .
TCE 1,1,2-Trichloroethane, vinyl trichloride
THM :. , Trihalomethane
TiO2 Titanium Dioxide
TNC Transient Non-Community , ™
TOC Total Organic Carbon .
IT Treatment Technique
UFC Uniform Fire Code ,
USEPA United States-Environmental Protection Agency
UV Ultraviolet ,
VOC Volatile Organic Compound
WERF Water Environment Research.Federation
WPCF .Water Pollution Control Federation
WQA Water Quality Association
WWEMA Water and Wastewater Equipment Manufacturer's Association, Inc.
UV Light Disinfection Technology in
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CONVERSION UNITS AND DEFINITIONS
Watt is the power produced by a current (a flow of electrons) of one ampere across a potential difference
of one volt. .,
Intensity is the power transferred across a unit area, e.g., watt/m2. In practical terms, intensity is the flux
or rate of delivery of photons to the target.
By-products precursor material is any material that reacts with disinfectants to form disinfection by-
products. '
\ ' '
Mineralization is the conversion of organic compounds into simple mineral acids and inorganic compounds
such as CO2 and H2O.
Einstein is a unit of radiant energy equal to the energy of radiation that is capable of photochemically
changing one mol of photosensitive substance.
Frequency is the number of cycles per second that passes a given point in space.
Radiation Absorbed Dose (RAD) is a unit of absorbed dose of ionizing radiation equal to an energy of
100 ergs per gram of irradiated material.
1 RAD = 100 ergs/gr of irradiated material.
1 Watt is the power produced by the work done by one joule per second.
1 Joule per second = 1 kg m2 sec = 1 Newton Meter
1 Newton = 1 kg m/sec2
1 Horsepower = 75 kgm/sec
1 Watt = 1 J/sec = 1 amp volt = (1/746) Horsepower = (75/746) kgm/sec = 0.1 kgm/sec
1 Watt/m2 =U/m2 sec = mW x 10
cm2
1 mWs/cm2 = 104 ergs/cm2
1 einstein of 254 nm quanta - 4.72 x 105 J/mole
1 Joule = (1/1.6) x 1019 eV = 0.625 x 1016 KeV
1 Joule = 107 ergs
1 Joule = 1 kg m2/sec2
1 Joule = 0.23901 calorie
1 nm = ID"9 m
1 U.S. gallon = 3.7854 liters
1,000 L/hr = 1 nvVhr = 6/340.15 gpd
UV Light Disinfection Technology in
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To convert degrees Centigrade (°C) to degrees Fahrenheit (°F), apply the following equation:
.°C = (°F-32)/1.8 ' , .
Planck's constant = 6.62608 x 10"34 Joules second r
= 6.62608 x ID"27 ergs
Speed of light = 2.997925 x 108 m/sec
When ultraviolet light is transmitted, the energy transmitted is represented by the following formula:
. E = hv
where: -
E = Energy in Joules or Watt second
h = Planck's constant in Joules second
v (nu) = Frequency in hertz.or sec-1
v = — • • " •" • • • ' • ' '
A - '. '• , " ' '••''.. .-"'..'
c = speed of light in m/sec = 2.9979 x 108 m/sec
X = wavelength in m
The energy of a photon is inversely proportional to the wavelength.
The energy of a photon at 253.7 nm:
Power = Work = Energy Transferred
Time Time
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UV Light Disinfection Technology in
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TABLE OF CONTENTS
PRELUDE . . ... . ' i
ABBREVIATIONS LIST ,:......... m
CONVERSION UNITS AND DEFINITIONS . . . . . . . vi
EXECUTIVE SUMMARY ....... ES-1
CHAPTER 1. BACKGROUND '....'.... M
1.1 INTRODUCTION TO ULTRAVIOLET LIGHT ...'..". '.'.['. . /. ' . " " i_2
1.2 GENERAL DESCRIPTION OF ULTRAVIOLET LIGHT
TECHNOLOGY !_6
1.3 EXISTING GUIDELINES FOR ULTRAVIOLET LIGHT
, DISINFECTION IN DRINKING WATER APPLICATIONS '". . . 1-13
1.4 AVAILABILITY OF ULTRAVIOLET TECHNOLOGIES FOR
GROUND WATER DISINFECTION 1.15
1.5 ULTRAVIOLET LIGHT SYSTEMS IN. WATER AND " ,
WASTEWATER APPLICATIONS ' i_20
i.6 REFERENCES . . . . . '.-. '. '. '. ''; i_25
CHAPTER 2. ASSESSMENT OF ULTRAVIOLET LIGHT EFFICACY,
VIABILITY, AND OPERATIONAL FACTORS 2-1
2.1 INTRODUCTION TO .INTENSITIES AND DOSES . 2-2
2.2 -INACTWATTON RATES (EFFICACY) , .......".".['.'. 2-4
2.2.1 Inactivation Rates Provided by Ultraviolet Light
Equipment Manufacturers . 2-4
2.2.2 Inactivation Rates in Drinking Water Treatment as
Compiled from the Scientific Literature - . 2-8
2-2.3 Cryptosporidium patvum Oocysts and Giardia muris Cysts
Inactivation Rates Using Ultraviolet Light . - 2-20
2.2.4 Doses and Inactivation Rates Achieved in Wastewater • ~ . -
.' ' ' . Treatment as Compiled from the Scientific Literature ..... 2-23
2.3 ULTRAVIOLET LIGHT OPERATIONAL FACTORS .. 2-27
2.3.1 Equipment Operational Factors "..-,. 2-27
2.3.1.1 Lamp Output . . .2-28
2.3.1.2 Lamp Agmg . ... . ...'......... . >2-28
2.3.1.3 FouUng and Plating of Lamps and Sleeves . 2-28
2.3.2 Water Quality Considerations ". . . . 2-29
23.3 Hydraulic Design Considerations . : 2-35
2.3.3.1 Dispersion 2-35
2.3.3.2 Turbulence 2-35
' 2.3.3.3 Effective Volume ,.'.-.' '.'.'.'.'.'. 2-35
2.3.3.4 Residence Time Distribution (RTD) 2-36
2.3.3.5 Flow Rate . .... f ....... .... . . . . . 2-37
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Table of Contents (Continued)
2.3.4 Small System Design Considerations 2-37
2.3.4.1 Inspections and Shutdown 2-41
2.3.4.2 Distribution System i ; . ' 2-42
2.3.4.3 Monitoring Devices 2-42 v
2.3.4.4 Manuals and Instructions 2-42
2.3.4.5 Spare Parts and Disposal 2-43
2.4 OTHER CONSIDERATIONS RELATED TO THE USE OF
ULTRAVIOLET LIGHT FOR DRINKING WATER
DISINFECTION 2-43
2.4.1 By-Products Formation and Removal of Organic
Contaminants by Ultraviolet Light Treatment 2-43
2.4.1.1 Removal of MX and Other Contaminants from
Drinking Water 2-44
2.4.1.2 Effects of Ultraviolet Light Treatment on Assimilable
Organic Carbon 2-47
2.4.1.3 Effects on Nitrite Formation 2-48
2.4.1.4 Effects on Mutagenicity Before and After Ultraviolet
Light Application to River Water 2-48
2.4.2 The Phenomena of Photoreactivation, Dark Reactivation,
and Chemical Reactivation 2-49
2.4.3 Ultraviolet Light and Residual Disinfection 2-52
2.4.4 The Search for a Surrogate . 2-59
2.4.4.1 ORP, a Non-Microbial Surrogate 2-62
- 2.4.5 Comparison of Ultraviolet Light to Chemical Disinfection 2-63
2.5 FINDINGS 2-66
2.6 REFERENCES . .> 2-70
CHAPTERS. EVALUATION OF ULTRAVIOLET LIGHT TECHNOLOGY
COSTS AND COMPARISON TO OTHER DISINFECTION
PROCESSES .-••; 3-1
3.1 INTRODUCTION 3-1
3.2 ULTRAVIOLET DISINFECTION COSTS 3-3
3.2.1 Capital Costs > 3-4
3.2.1.1 Equipment Costs 3-4
3.2.1.2 Construction Costs 3-6
3.2.1.3 Total Capital Costs , 3-6
3.2.2 Operation and Maintenance Costs ; 3-8
3.2.2.1 Parts Replacement 3-9
3.2.2.2 Power Costs 3-9
3.2.2.3 Labor Costs 3-9
3.2.2.4 Summary of Operation and Maintenance Costs 3-12
3.2.3 Total Costs of Ultraviolet Disinfection (Capital Costs and
Operation and Maintenance Costs) 3-16
3.3 COMPARISON OF CURRENT ULTRAVIOLET SYSTEMS
COST ESTIMATES TO ULTRAVIOLET COSTS REPORTED
IN A 1993 USEPA DOCUMENT 3-17
UV Light Disinfection Technology in
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Table of Contents (Continued)
3.4 ULTRAVIOLET LIGHT SYSTEM COSTS COMPARED TO
CHLORINATTON AND OZONATION DISINFECTION
TECHNOLOGIES , .... 1 3-25
3.4.1 Ozonation Costs 3-25
3.4.2 Chlorination Costs 3-26
3.5 COST OF ULTRAVIOLET DISINFECTION WTIH ••.••-••/••.•••.
SECONDARY TREATMENT THROUGH CHLORINATION . 3-31
. 3.5.1 Cost of Secondary Treatment . : . . ; 3.31
3.5.2 Total Production Costs for Ultraviolet Disinfection with
Chlorination '...... ....." 3-34
3.5.3 Comparison to Other Treatment Techniques ........ 3.34
3-6 ULTRAVIOLET LIGHT SYSTEM COST ESTIMATES FROM
OTHER SOURCES ..... 3.34
3.7 SMALL NON-COMMUNITY WATER SYSTEMS FLOW
REQUIREMENTS AND COST IMPLICATIONS 3.39
3.8 CONCLUSIONS " ' 3_42
. , • • 3.9 REFERENCES . .;'. ............. ".,'. .'; "" 3.43
CHAPTER 4. OPERATIONAL CASE STUDIES .... .... ; r i_i
4.1 INTRODUCTION'.,.'. . . ..-....,.. M
4.2 CASE STUDIES FROM THE STATE OF NEW JERSEY ....... '.'. '. j' 1-3
4.2.1 PWS in Phillipsburg, New Jersey ; . 1-3
- 4,2.2 TNC in Lebanon, New Jersey ........... 1-4
4.2.3 TNC in Branchville, New Jersey . . . '.'.'.'.'. 1-5.
• • , 4.2.4 NTNC in Harmony Township, New Jersey .................. 1-5
4.2.5 TNC in Ringoes, New Jersey ; . . i-g
4^2.6 NTNC in Ringoes, New Jersey 1-6
. 4.2.7 NTNC in Stewartsville, New Jersey . .'.,1-1
4.2.8 TNC Ground Water System in Washington, New Jersey .... 1-7
4.3 CASE STUDIES FROM THE STATES OF OREGON,
MONTANA, AND MARYLAND . . . . 1^8
4.3.1 Villadom Mobile Home Park CWS In Umatilla County,
Oregon r . . 1-9
4.3.2 Fort Benton, Montana ....................... ; . i_jo
, 4.3.3 Mayo Water Reclamation Facility, Maryland . 1-11
4.4 CASE HISTORY, LANDEUS WATER TREATMENT PLANT
IN THE NETHERLANDS . . .,..!... 1-12
4.5 PERSPECTIVE OF TWO WATER TREATMENT UNITS
SERVICE CONTRACTORS ............. '.. 1-13
4.6 COSTS OF ULTRAVIOLET LIGHT UNITS AND DESIGN
FLOWS OF TNC AND NTNC SYSTEMS AS REVEALED
FROM THE CASE STUDIES , 1-14
4.7 SUMMARY OF FINDINGS . . .............. T 1-15
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Table of Contents (Continued)
: Page
4.8 SUGGESTED CRITERIA FOR THE USE OF ULTRAVIOLET
LIGHT UNITS BASED ON THE PRESENTED CASE
STUDIES , 1-18
4.9 REFERENCES 1-19
CHAPTER 5. SUMMARY OF FINDINGS 5-1
5.1 EFFICACY AND APPLICABILITY 5-1
5.2 OPERATIONAL FACTORS '.- 5-3-
5.3 EVALUATION AND COMPARISON OF ULTRAVIOLET
LIGHT TECHNOLOGY COSTS TO OTHER DISINFECTION
PROCESSES 5-4
5.4 CASESTUDIES ., 5-6
APPENDIX A. OTHER ULTRAVIOLET-RELATED
DRINKING WATER DISINFECTION TECHNIQUES A-l
A.1 PHOTOASSISTED HETEROGENOUS CATALYTIC
OXIDATION (PHCO) . . . . . A-l
A.2 INACTIVATION RATES ACHIEVED WITH THE USE OF
MODULATED ULTRAVIOLET LIGHT ." A-3
A.3 REFERENCES A-4
APPENDKB. ORGANICS DESTRUCTION . .: B-l
B. INTRODUCTION B-l
B.I BACKGROUND . . . B-l
B.2 DESTRUCTION POTENTIAL B-2
B.4 OPERATIONAL FACTORS ... B-14
B.5 ULTRAVIOLET LIGHT TECHNOLOGY AND CURRENT
SAFE DRINKING WATER REGULATIONS ... B-19
B.6 REFERENCES .... . B-20
APPENDIX C. QUESIONNAJGRE USED FOR STATE INQUIRY AND AS GUIDE ,
IN TELEPHONE INQUIRIES C-l
C.1 GENERAL SYSTEM QUESTIONS AND EQUIPMENT . C-l
C.2 WATER DATA C-l
C.3 OPERATION AND MAINTENANCE , C-2
C.4 COSTS ... . C-2
C.5 ON-SITE CONTACT . C-2
UV Light Disinfection Technology in
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Table of Contents (Continued)
APPENDIX D. REGULATIONS AND STANDARDS FOR DRINKING WATER
DISINFECTION USING ULTRAVIOLET LIGHT ......... .
D-l
D.I DEPARTMENT OF .HEALTH, EDUCATION, AND
WELFARE ...
D.2 UTAH . . . . . .......;
D.3 WISCONSIN i
D.4 PENNSYLVANIA .'.., . . . . ......
D,5 NEW JERSEY •
D.6 ANSI/NSF STANDARD 55 .... i
. D-2
'. D-5
. D-7
D-15
D-18
D-19
UV Light Disinfection Technology in
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LIST OF EXHIBITS
Exhibit 1-1. Ultraviolet Light Mode of Action on Microorganisms . . . . 1-3
Exhibit 1-2. Relative Bactericidal Effectiveness as a Function of Wavelength 1-5
Exhibit 1-3. Emission Spectra of Low-Pressure and Medium-Pressure Mercury Lamps 1-7
Exhibit 1-4. Non-Contact Ultraviolet Disinfection Unit 1-8 /
Exhibit 1-5. Closed Vessel Ultraviolet Reactor '. . 1-9
Exhibit 1-6. Vertically Mounted Ultraviolet Lamps in an Open Channel System : . 1-10
Exhibit 1-7. Horizontally Mounted Ultraviolet Lamps in an Open Channel System . 1-11
Exhibit 1-8. Example of Lamp Arrangement in an Ultraviolet Reactor ..... 1-12
Exhibit 1-9. EU Microbiological Parameters Drinking Water Directive 80/778/EEC 1-16
Exhibit 1-10. List of Companies and Individuals That Are Actively Involved in the Ultraviolet
Industry, Either as Manufacturers or as Major Distributors 1-19
Exhibit 1-11. Application of Ultraviolet Disinfection in Three European Countries . 1-21
Exhibit 1-12. Ultraviolet Systems in Wastewater Applications in 1984 and 1990 . i-23
Exhibit 2-1. Dose and Intensity Measurements 2-3
Exhibit 2-2. Doses Required for "Complete Destruction" (>99.9%) of
Microorganisms • 2-5
Exhibit 2-3. Dose Required at 253.7 Nanometers to Inhibit Colony Formation in 90
Percent of the Organisms and for Complete Destruction (>99.9%) 2-6
Exhibit 2-4. Summary of Ultraviolet Light Microorganisms Inactivation Dose
Requirements in mWs/cm2 2-7
Exhibit 2-5. Light Intensities and Mean Lethal Doses for E. Coli 2-8
Exhibit 2-6. Survival Curve of Bacillus Megaterium Irradiated Using Ultraviolet
Light at 280.3 nm . ." . . '.' 2-9
Exhibit 2-7. Ultraviolet Light 254 nm Dose (mWs/cm2) Required for a 90 Percent
Killing of Various Microorganisms ., 2-9
Exhibit 2-8. Inactivation of Health-Related Microbes in Water by Ultraviolet
Radiation ............. 2-12
Exhibit 2-9. Inactivation of B. subtilis Spores Depending on Laboratory Cultural
Methods • '....'. 2-13
Exhibit 2-10. Survival Curves of Ultraviolet Irradiated Bacteria 2-15
Exhibit 2-11. ' Survival Curves of Ultraviolet Irradiated Viruses and Test Surrogate '
Coliphage MS-2 . . ; . ; 2-16
Exhibit 2-12. Ultraviolet Estimation From Linear Regression Model of Coliphage MS-2 . .". . 2-16
Exhibit 2-13. • Comparison of Protozoan and Bacterial Sensitivity to Ultraviolet Light 2-18
Exhibit 2-14. Average Log Reduction of Microorganisms Using Combined Carbon
Block Filter with Ultraviolet Disinfection Unit (>128 mWs/cm2) . ':..'. 2-19
Exhibit 2-15. Giardia muris Cyst Survival Percent Versus Ultraviolet Light
Exposure .:..... 2-21
Exhibit 2-16. Ultraviolet Irradiation Curves for Protozoan Type Organisms .............. 2-22
Exhibit 2-17. Inactivation of Microorganisms in a Mix of 70% Domestic
Wastewater, Secondary Effluent, and 30% Surface Water .. . . . 2-24
Exhibit 2-18. Ultraviolet Light and Chlorine Doses to Achieve 99.9% Inactivation of
Microorganisms in Reclaimed Water 2-25
Exhibit 2-19. Average 33 to 35 Observations of Log Survival of Coliform Bacteria
in Unfiltered Effluent Samples 2-26
UV Light Disinfection Technology in
Drinking Water Application—An Overview
xiv
Final—September 1996
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List of Exhibits (Continued)
Exhibit 2-20. Ultraviolet Light Absorbance as a Function of Turbidity . . 2-27
Exhibit 2-21. Ultraviolet Transmission and Absorbance Coefficient ...'.:.. 2-30
Exhibit 2-22. Chick's Law and Deviations .. ...... 2-33
Exhibit 2-23. Factors Affecting Ultraviolet Light Disinfection Performance 2-34
Exhibit 2-24. Closed Ultraviolet Light Reactor 2-36
Exhibit 2-25. Residence Time Distribution Curves •;.... 2-37
Exhibit 2-26. Practical Application of Ultraviolet Light in Water Disinfection,
Surrogate Used Bacillus subtilis 2-38
Exhibit 2-27. Results of Disinfection By-Products of Ultraviolet Light . . . 2-45
Exhibit 2-28. Disinfection By-Products Found in Chlorinated and UV-Irradiated
EVMWD Tertiary Effluent 2-46
Exhibit 2-29. Effects of Ultraviolet Radiation on AQC Concentration . 2-47
Exhibit 2-30. Surviving Fraction .in Four Microbial Species After Ultraviolet
Irradiation ....-:. 2-50
Exhibit 2-31. Baerum Average Water Quality Parameters . 2-53
Exhibit 2-32. Seasonal Accumulation of Biofilnv Measured as Dry Weight, in the
Different Pipe Systems and Seasonal Variations in Raw Water
Temperature .......... . 2-55
Exhibit 2-33. Baerum Water Quality Parameters 2-56
Exhibit 2-34. Demonstration of Long-Term Inhibitory Effect in U.V.-Irradiated
Water Compared to Raw Water, After Addition to Heterotrophic
Bacteria .....;........ 2-56
Exhibit 2-35. Water Quality Parameters of the Baarum water used in Tracer
Experiments . , . . 2-57
Exhibit 2-36. Bacterial Uptake of 3H-Labelled Leucine in-Water Samples with -
Identical Inoculation Volumes . . . . 2-58
Exhibit 2-37. Bacterial Uptake of 3H-LabeIled Thymidine During 24 Hours in
Ultraviolet-Irradiated and Untreated Control Samples for Various
Volumes of Inocular Added '...-' 2-59
Exhibit 2-38. Extrapolated Inactivation Rates for Bacteria, Viruses, and Test
Surrogate Coliphage MS-2 . . . .....' 2-61
Exhibit 2-39. Germicidal Effects of Ultraviolet Light Versus Chemical Disinfectants
in Drinking Water Applications 2-65
Exhibit 2-40. Relative Ultraviolet Light Dose for Some Microorganisms . . 2-66
Exhibit 2-41. Ultraviolet Light Versus Chlorination and Ozonation in Drinking • • ..
Water ........ ............ ...;. '2-67
Exhibit 3-1. USEPA Flow Categories and Population Served .. 3-2
Exhibit 3-2. Equipment Costs ... ' 3.5
Exhibit 3-3. Added Engineering and Installation Costs i .... 3-6
Exhibit 3-4. Total Capital Costs ; . . . 3.7
Exhibit 3-5. Parts Replacement Costs . . .......... 3-10
Exhibit 3-6. Power Costs ........ 3-11
Exhibit 3-7. Labor Costs . 3-13
Exhibit 3-8. Major Operation and Maintenance Costs (Excluding Miscellaneous
and Chemical Costs). . . 3-14
UV Light Disinfection Technology in
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XV
Final—September 1996
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List of Exhibits (Continued)
Exhibit 3-9. Unit and Total Operations and Maintenance Costs for Ultraviolet Light
Disinfection System •» 3.15
Exhibit 3-10. Total Current Costs 3-16
Exhibit 3-11. Ultraviolet Capital Cost Estimates 3-18
Exhibit 3-12. Ultraviolet Operation and Maintenance Cost Estimates . . . 3-18
Exhibit 3-13. Adjusted (USEPA, 1993a) Operation and Maintenance Costs as per
Manufacturers' Estimates of Labor Requirements 3-19
Exhibit 3-14. Comparison of Total Production Costs with Varying Labor
Requirements '. . ." 3_2Q
Exhibit 3-15. Ultraviolet Cost Estimates 3.21
Exhibit 3-16. Comparison of Capital Costs of Ultraviolet Treatment . % 3-22
Exhibit 3-17. Comparison of Operation and Maintenance Costs of Ultraviolet
Treatment 3.23
Exhibit 3-18. Comparison of Total Production Costs of Ultraviolet Treatment ..'. 1 ......... 3-24.
Exhibit 3-19. Small System Ozonation Costs ... ; 3-26
Exhibit 3-20. Small System Chlorination Costs .'. .; 3-28
Exhibit 3-21. Ultraviolet Light System Costs for USEPA Flow Categories 1-5
Compared to Chlorination and Ozonation in Cents per Thousand
Gallons 3_28
Exhibit 3-22. Ultraviolet [40 mWs/cm2], Chlorination, and Ozonation Total Costs:
USEPA How Categories 1-5. 3-29
Exhibit 3-23. Ultraviolet [140 mWs/cm2], Chlorination, and Ozonation Total Costs:
USEPA Row Categories 1-5 '...:.. ......... 3-30
Exhibit 3-24. Amount of Chlorine Stock Solution Required Per Day (1 mg/L Dose) 3-32
Exhibit 3-25. Total Production Costs of Secondary Treatment Through 1 mg/L
Chlorine 3_32
Exhibit 3-26. Costs of Disinfection Through Chlorination (1 mg/L Dose) 3-33
Exhibit 3-27. Total Production Costs of Ultraviolet Treatment with Secondary
Disinfection . . . . . . . _ 3.34
Exhibit 3-28. Total Production Costs for Ultraviolet Disinfection with Chlorination . 3-35
Exhibit 3-29. Total Costs: Ozonation, Chlorination, and Ultraviolet Radiation (40
mWs/cm2) with Secondary Treatment 3-36
Exhibit 3-30. Total Costs: Ozonation, Chlorination, and Ultraviolet Radiation (140 .
mWs/cm2) with Secondary Treatment 3-37
Exhibit 3-31. Total Production Costs of Ultraviolet Treatment with Secondary
Treatment Compared to Chlorination and Ozonation 3-38
Exhibit 3-32. Estimated Capital and Operating Costs for Ultraviolet Irradiation and
Chlorination/Dechlorination ....................' 3.33
Exhibit 3-33. Ultraviolet Light Treatment System : 3.39
Exhibit 3-34. Ground Water NCW Systems Serving Two Population Ranges 3-40
Exhibit 3-35. Typical Rates of Water Use in Non-Community Water Systems 3-41
Exhibit 4-1. Ultraviolet Light Technology in Drinking Water Applications - Case .
Studies Summary Table 1-17
UV Light Disinfection Technology in
Drinking Water Application—An Overview.
xvi
Final—September 1996
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List of Exhibits (Continued)
Exhibit 5-1. Average Total Costs for Ultraviolet Light Dismfection Systems ............. 5-4
Exhibit 5-2. Comparison of Ultraviolet Light Disinfection Process Costs to
Chlorination and Ozonation Process Costs in Cents per Thousand :
Gallons . . . . 5.5
Exhibit 5-3. Comparison of Total Production Costs of Ultraviolet Treatment with
Secondary Disinfection to Chlorination and Ozonation Process ; 5-5
Exhibit Arl. Cost Estimates for the Removal of DBP Precursors from 1 MOD
Using the PHCO Process A-2
Exhibit B-l. A Precis Description of Chemical Bonding to Explain Organics ,
Destruction Potential Using Ultraviolet Light ........ .^ B-3
Exhibit B-2. Photodegradation of Herbicides of the Atrazine Family B-7
Exhibit B-3. Removal of Organic Chemicals from Water with Ultraviolet Radiation
and Hydrogen Peroxide ........ B-9
Exhibit B-4. Elimination of Pyridine and TOC Reduction by O3/UV and Ozone
Alone . . . .......... • B-1Q
Exhibit B-5. Pyridine Elimination and TOC Reduction at Different pHs ...........;... B-ll
Exhibit B-6. Ultrox® Demonstration at South Gate Ground Water Supply Site B-13
Exhibit E-7. Chlorinated Hydrocarbon Elimination with Ozone/Ultraviolet
Treatment in Drinking Water Supply of Niederrqhrdorf B-14
Exhibit B-8. Power of Light Emitted by Mercury-Vapor Ultraviolet Lamps B-17
Exhibit B-9. Dissociation Energies for Chemical Bonds B-18
Exhibit B-10. Examples of Photochemical Reactions and Their Effects ..:... B-19
UV Light Disinfection Technology in
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EXECUTIVE SUMMARY
CHAPTER 1. BACKGROUND
Ultraviolet treatment in drinking water involves the direct exposure of the water stream to ultraviolet light.
Exposure to the ultraviolet light damages nucleic acids and changes their mode of action in
microorganisms, thus preventing microorganisms from propagating or remaining active. Ultraviolet light
is generated by striking an electric arc through mercury vapor. The low-pressure mercury vapor lamp
emits primarily at a wavelength of 253.7 nm with a lesser output at 184.9 nm. Research has shown that
the dptimuin ultraviolet light wavelength range for .bactericidal effect is between 250 nm and 270 nm and
that maximum ultraviolet absorption by DNA occurs at about 200 nm wavelength..At shorter wavelengths
' i • ' • -
(e.g.; 185 nm), ultraviolet light is powerful enough to produce ozone, hydroxyl radicals, and other free
radicals that have germicidal effects.
The use of ultraviolet light to disinfect drinking water in the United States dates back to 1916. Currently,
several States have regulations that specifically allow the use of ultraviolet light to disinfect public non-
community ground water supplies. Other States, like Mpntana and Oregon, recognize ultraviolet light as-
an acceptable technology for drinking water disinfection and permit its use on a case-by-case basis. At
least four States forbid the use of ultraviolet light technology for water disinfection in public water
systems. • - -•..-,
Guidelines for the use of ultraviolet light for water disinfection, set by the U.S. Department of Health,
Education, and Welfare (DREW) in 1966, require a minimum dose of 16 mWs/cm2 (milliwatts second per
square centimeter) at all points throughout the water disinfection unit. The American National Standards
Institute (ANSI) and the National Sanitation Foundation International (NSF) set the minimum ultraviolet
light requirement to disinfect drinking water at 38 mWs/cm2 for class A point of use (POU) and point of
entry (POE) devices treating visually clear water. Also, the ANSI/NSF standard requires 16 mWs/cm2 for
class B POU treatment devices, which are for supplemental bactericidal treatment of disinfected or,
otherwise safe drinking water '(i.e., to reduce nuisance bacteria only). Some European states have a
minimum dose requirement for ultraviolet disinfection. In Austria, the minimum acceptable ultraviolet
dose for pretreated drinking water disinfection is 30 mWs/cm2. "
At least 20 firms manufacture or are major distributors of ultraviolet light equipment in the United States.
These firms market ultraviolet equipment for disinfection of water and other media. Of the 20 firms, six
UV Light Disinfection Technology in
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Executive Summary
are foreign companies. Some of these firms, including domestic firms, have been in the ultraviolet light
equipment market for decades and have acquired tremendous experience and expertise in the field. The
domestic ultraviolet industry claims that it can deliver closed system units in 4 to 8 weeks.
CHAPTER 2. ASSESSMENT OF ULTRAVIOLET LIGHT EFFICACY, VIABILITY, AND
OPERATIONAL FACTORS
The inactivation of microorganisms in drinking water by means of ultraviolet light is a function of
intensity of the radiation, proper wavelength, exposure time, water quality, flow rate, type and source of
the microorganisms (natural or culture), and the distance from the light source to the targeted
microorganisms. The intensity is measured in milliwatts per square centimeter and time is measured in
seconds. Therefore, the dose is measured in milliwatts second per square centimeter (mWs/cm2).
The data clearly show, with few exceptions, that the order of ultraviolet light disinfection resistance is as
follows:
Bacteria < viruses < bacterial spores < protozoan cysts and oocysts.
Least resistant Most resistant
to ultraviolet light . ' • to ultraviolet light
Some ultraviolet light equipment manufacturers claim that bacteria can be greater than 99.9 percent
inactivated by an ultraviolet dose of 26.4 mWs/cm2 and that protozoa can be completely destroyed by a
dose of 200 mWs/cm2. The claims made by ultraviolet light equipment manufacturers for virus
inactivation ranged from a 1 log reduction at a maximum dose of 11.3 mWs/cm2 to complete destruction
at 440 mWs/cm2 for tobacco mosaic virus.
In general, and mainly under laboratory conditions using distilled water as a medium, the scientific
literature shows that a 3 log reduction of bacteria is achieved using an ultraviolet light dose of 30
mWs/cm2, a 3 log reduction of viruses is achieved at an ultraviolet light dose of 45 mWs/cm2 (Reovirus
1), and a minimum 3 log reduction of bacterial spores is achieved at a dose of 60 mWs/cm2. A 4 log
reduction of bacteriophage MS-2 is achieved at a dose of 93 mWs/cm2. A 4 log inactivation of rotavirus,
poliovirus and Hepatitis A virus is achieved by an ultraviolet light dose of 50 mWs/cm2, 29 mWs/cm2,
and 15 mWs/cm2 respectively. A 2 log reduction of Giardia lamblia is achieved at a dose of 180
UV Light Disinfection Technology in
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Executive Summary
mWs/cm2. For filtered secondary effluent, an ultraviolet light dose of 120 mWs/cm2 can achieve a 4 log
reduction in poliovirus. ' .
Based on their study of the practical experience of ultraviolet disinfection in the Netherlands, Kraithof et
al. (1992) recommended the use of ultraviolet light (without use of a secondary disinfectant) for
disinfecting drinking water from all sources of water provided that two conditions are met: (1) the water
has to be low in biodegradable compounds so regrowth would not occur, .and (2) the distribution network
does not need any additional protection (no biofilm growth is likely due to low AOC and no cross-
contamination is likely). Multiple treatment steps in Dutch waterworks typically ensure protozoa, cysts,
and organic compounds removal.
Ultraviolet Light Systems
There are two types of ultraviolet systems: closed systems and open systems. Closed systems are more
commonly used in potable and sterile water applications and are assumed in this analysis to be the systems
used for meeting small water systems requirements. . . . •
Equipment Operational Factors
The operational factors that affect adequate performance of an ultraviolet light,system are lamp output,
lamp aging, and plating and fouling of unit surfaces. To better "control these operational factors,
continuous dose measurement (i.e., accurate intensity and flow rate measurement) and proper maintenance
(cleaning regimes and lamp and sleeve replacement regimes) are essential.
\ ' • • . -
Water Quality Factors
The performance of an ultraviolet disinfection system is inversely related to ultraviolet light absorbance
of the water being treated. This ultraviolet absorbance is analogous to _chlorine demand in chemical
dismfection processes. Microbial and chemical characteristics are the two major water quality factors that
affect the performance of an ultraviolet unit in treating ground water (i.e., very low turbidity with no or
very low silt and suspended matter content). Microbial water characteristics include type, source, age, and
density. Chemical water characteristics include nitrites, sulfites, iron, hardness, and aromatic organic
levels.
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Drinking Water Application—An Overview ES-3 Final—September 1996
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Executive Summary
Hydraulic Design Considerations
The major hydraulic elements that need to be accounted for in the design arid operation of an ultraviolet
light disinfection system are dispersion, turbulence, effective volume, residence time distribution, and flow
rate.
Small System Design Considerations
Multiple modular units are recommended for small systems. At a minimum, two units, each capable of
carrying design flow, ought to be installed for the purpose of maintaining a continuous disinfection process
while a unit is being serviced and to operate the appropriate number of units during low flow demand
periods. Modular units designed for small drinking water systems should be easy to install (two plumbing
connections per unit and one electrical hookup) and operate. They should be equipped with automatic
cleaners and remote alarm systems. For systems hi remote areas, a set of spare parts should be maintained
and property stored onsite, and a telemetry system for monitoring treatment may be a consideration.
Othej Considerations Related to the Use of Ultraviolet Light for Drinking Water
Disinfection
By-Products Formation and Removal of Organic Contaminants
Some organic contamination removal and breakdown occurs in ultraviolet-light-treated drinking water.
At this point there are no significant by-products formed as a result of ultraviolet light disinfection, and
there is no significant increase in assimilable organic carbon (AOC) and no significant nitrite formation
from nitrate-containing treated water.
The Phenomena of Photoreactivation, Dark Reactivation, and Chemical Reactivation
Some microorganisms damaged by ultraviolet light may recover if they are exposed to visible light shortly
after the exposure to ultraviolet light. In addition to such environmental factors as pH and temperature,
the presence of certain compounds and the availability of repair enzymes are also important in the process
of reactivation. Viruses do not have repair enzymes, so they do not photoreactivate on their own.
However, viruses can use enzymes of the host cell to repair damages and resume activity, The experience
gained from ultraviolet light application hi wastewater disinfection shows a maximum repair .rate of 1 to
2.5 log in coliforms. However, in drinking water application, recent research shows that reactivation does
not occur and is not a significant issue. la addition, a variety of post treatment (i.e., storage, distribution)
configurations may impact reactivation kinetics hi drinking water application.
UV Light Disinfection Technology in
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Executive Summary
Ultraviolet Light and Residual Disinfection
Recent pilot studies show that ultfaviolet-light-treated drinking water has an inhibitory effect on bacterial
growth and replication in the distribution system; however, conditions within distribution systems and
external sources of contamination may dictate the need for providing additional residual (e.g., free
-chlorine) disinfection.
The Search for a Surrogate
traditional indicator surrogate microorganisms such as coHforms are sensitive to ultraviolet light.
Therefore, a surrogate microorganism is needed to quantify the correlation of its inactivation rates to that
of-pathogenic microorganisms. Two challenge microorganisms, Bacillus subtilis spores and coliphage
MS-2, are reviewed as indicators for .ultraviolet light water disinfection efficiency. Both microorganisms
are getting more research attention than other challenge microorganisms.
-,' "," " - • / ' ' - ' ' - - • '
Comparison of Ultraviolet Light to Chemical Disinfection
When comparing ultraviolet light to traditional chemical disinfectants, the following issues stand out:
! - ' - - ' .
• Sensitivity to traditional microbiological parameters, such as coliforms
• Comparative relative effectiveness against specific pathogenic microorganisms
• Capital and operation and maintenance (O&M) costs and space requirements
• Risks associated with the formation of by-products or overdosing
• Effects on secondary water quality parameters, such as smell and taste
• Residual disinfection.
Traditional microbiological drinking water parameters (e.g., coliform) are sensitive to ultraviolet light.
This fact complicates direct comparison of ultraviolet light to chemical disinfection. Studies of the
comparative relative effectiveness of ultraviolet light versus chlorination and ozonation, using fecal
coliform inactivation as the baseline, have been conducted by different researchers with mixed results.
Also, unlike ozonation and chlorination processes, ultraviolet light application in drinking water is not
associated with any negative smell or taste effect.
Disadvantages of ultraviolet light disinfection technology include the lack of a measurable disinfection
residual, the lack of a firm technical database on system efficiency in various water.quality conditions,
UV Light Disinfection Technology in
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Executive Summary
and the lack of an in-place standardized mechanism to measure, calibrate, and certify equipment for
efficiency before and after installation. The general belief in the scientific community is that ultraviolet
technology does not leave a disinfection residual, however, according to recent research, ultraviolet light
does leave some residual disinfection effect in treated water.
CHAPTER 3. EVALUATION AND COMPARISON OF ULTRAVIOLET LIGHT
TECHNOLOGY COSTS TO OTHER DISINFECTION PROCESSES
Cost estimates to disinfect five USEPA flow categories are presented in this chapter. These flow
categories are Design Hows 0.024 MOD, 0.087 MOD, 0.270 MOD, 0.650 MOD, and 1.8 MOD. The
ultraviolet light doses considered in these cost estimates are 40 mWs/cm2 and 140 mWs/cm2. Capital and
O&M costs show that ultraviolet light is an economically feasible disinfectant, particularly in a ground
water setting.
Ultraviolet Light Disinfection Costs
Capital costs considered are equipment and installation costs plus a 20 percent markup for engineering,
site work, and other related items. Equipment costs considered are average costs obtained from ultraviolet
light manufacturers. O&M costs include parts replacement, periodic cleaning, power consumption, labor,
and miscellaneous equipment repair costs. Ultraviolet light disinfection system costs are presented in the
following table, in this Executive Summary and are discussed in more detail in Chapter 3.
Ultraviolet Light System Costs (With and Without Secondary Disinfection) Compared to
Chlorination and Ozonation Disinfection Technologies
\ ' i •
Chlorination and ozonation costs for Flow Categories 1 through 5 were calculated using the USEPA 1993
document Very Small Systems Best Available Technology Cost Estimates. The cost comparisons of
ultraviolet treatment with and without Chlorination as secondary disinfectant are presented in the following
figures, in this Executive Summary and are discussed in more detail in Chapter 3.
CHAPTER 4. OPERATIONAL CASE HISTORIES
The information collected from the case studies revealed satisfaction with the performance of ultraviolet
equipment. The case studies also revealed that generally, ultraviolet systems receive little attention 'and
require very little supervision. Minimum service time, low operation and maintenance costs, and the
absence of a chemical smell and taste in finished water were the main cited factors for selecting ultraviolet
technology over traditional disinfection technologies.
UV Light Disinfection Technology in
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Executive Summary
Ultraviolet Light Disinfection System Costs for USEPA Flow Categories 1-5
at 40 mWs/crn2 and 140 mWs/cm2 Doses
Dose 40 mWs/cm2
EPA Flow
Category
1
2 •
3
4
5
Design
Flow
(MGD)
0.024
0.087
0.27
0.65
1-8
Cost per Year (k$)*
Total
Capital
1.3
1.7
3.7
7.7
16.6
Total
O&M
0.4
0.8
1.7
3.7
9.7
Total
Production
Cost
1.7
' • ' .2.5
5.3
11.4
26.3 '
Cost (c/kgal)
Total
Capital**
15
5
4
3
3
Total
O&M
4
2
2 '
,2
1
Total
Production
Cost***
19
8
5
5
4
Dose 140 mWs/cm2 .
EPA Row
Category,
1
' ,.,2,
3
,• - 4
5
Design
Flow
(MGD)
0.024 :
0;087
0.27
0;65
1-8,
Cost per Year (k$)*
Total
Capital
1.7
3.6
1 0.0
16.5
42.1
Total
O&M
0.8
2.1
5.5
'9.4
34.0
Total
Production
Cost
2.5
5.7
15.5
25:8
76.0
Cost (c/kgal)
Total
Capital**
19
•11
10
7
6
Total
O&M
9
7
6 "'
4
5
Total
Production
Cost***
28
' : 18
6
11
12
•August 1995 dollars ,
**Cpsts amortized .at 10% for 20 years
"'Figures might not add up because of, rounding
CHAPTERS. SUMMARY OF FINDINGS >
Ultraviolet light is an effective disinfection agent for drinking water at sufficient intensity and appropriate
wavelength and exposure time. ''It is suitable for use on clean water sources more than it is for
suspended matter-containing water. The order of disinfection resistance with few exceptions is bacteria
(least resistant) < viruses < bacterial spores < protozoan cysts < protozoan oocysts (most resistant).
For the most resistant microorganisms, the literature shows that a 6 log reduction of Bacillus subtilis
spores is achieved at 120 mWs/cm2, a 5.5 log reduction at 90 mWs/cm2, and a 4 log reduction at
60 mWs/cm2; for Giardia lambliq, a 2 log reduction is achieved at 180 mWs/cm2. For bacteriophage
MS-2 a 4 log reduction could be achieved at a dose of 93 mWs/cm2. For viruses the literature shows that
a 3 log reduction of Reoviras 1 is achieved at 45 mWs/cm2 in a buffered distilled water.
UV Light Disinfection Technology in
Drinking Water Application—An Overview.
ES-7
Final—September 1996
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Executive Summary
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Drinking Water Application—An Overview
ES-8
Final—September 1996
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Executive Summary
UV Light Disinfection Technology in
Drinking Water Application—An Overview.
ES-9
Final—September 1996
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Executive Summary
According to USEPA data covering the years 1971 to 1977, 35 percent of outbreaks of waterbome
diseases in the United States occur in non-community water supply systems. Thirty-three percent of
waterbome disease outbreaks in ground water supply systems are caused by bacteria, 6 percent are caused
by chemical agents, 3 percent by HAV viruses, less than 1 percent by Giardia, and about 58 percent by
unknown agents. Therefore, using any form of disinfection in ground water systems will eliminate or
greatly reduce the number of outbreaks caused by bacterial and viral agents and also may reduce the
number of outbreaks caused by unknown agents.
The data on ultraviolet disinfection efficacy clearly show that many pathogenic bacteria and viruses (e.g.,
Vibrio cholerae, HAV, and pplioviruses) associated with high morbidity and mortality around the world
are very susceptible to ultraviolet light.
Operation and Maintenance
Technological advances have eliminated many of the O&M problems that were associated with earlier
ultraviolet applications for disinfecting drinking water. Current systems are equipped with mechanical
cleaners, ultrasonic cleaners, or some self-cleaning mechanism; lamps that are easy to install and replace;
and alarm systems that indicate minor and major failure.
Evaluation and Comparison of Ultraviolet Costs to Other Disinfection technologies
At a dose of 40 mWs/cm2 and for systems treating design flows of 0.024 MGD through 1.8 MOD
(USEPA How Categories 1 through 5), ultraviolet light systems are economically more feasible than
chlorination at a 5 mg/L dose and ozonation at a 1 mg/L dose for the same flow categories, provided that
a residual disinfectant is not required for distribution and/or storage.
At a dose of 140 mWs/cm2, ultraviolet light systems are less expensive than ozonation at a dose of 1 mg/L
in all flow categories but slightly more expensive than chlorination at a dose of 5 mg/L in flow category
1.8 MGD.
APPENDIX A—OTHER ULTRAVIOLET-RELATED DRINKING WATER DISINFECTION
TECHNIQUES
Nonconventional techniques include pulsed ultraviolet light and Photoassisted Heterogeneous Catalytic
Oxidation (PHCO). These techniques have been used, although on a limited scale, in water and
wastewater applications. In the PHCO process, Titanium dioxide (TiO2) is illuminated by near visible
UV Light Disinfection Technology in
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Executive Summary
ultraviolet light (long wavelengths). The energy absorbed by TiO^ produces a redox potential sufficient
to kill some microorganisms and mineralize organic compounds. The literature shows that under
laboratory conditions, Escherichia coli can be destroyed completely with 30 minutes contact time and a
dose of 1 g/LofTiO2.
APPENDIX B—ORGANICS CONTROL
Ultraviolet light is used alone and in conjunction with 'ozone and hydrogen peroxide to treat ground water
contaminated with organic compounds. However, the intensities and doses used in these treatment
processes are far more than what might be necessary to disinfect drinking water. The current data show
that ultraviolet light does not produce or leave any hazardous by-products in the treated water.
APPENDIX C—QUESTIONNAIRE OF ISSUES USED FOR STATE INQUIRY AND AS GUIDE
IN TELEPHONE INQUIRIES
Twenty-seven questions were used to develop good case studies on ultraviolet use in drinking water
disinfection. Eleven questions concentrated on systems and equipment, four questions were on water
quality conditions, seven questions dealt with operation and maintenance, four questions were cost related,
and one question was about the contact person and system manager.
APPENDIX D—REGULATIONS AND STANDARDS FOR DRINKING WATER DISINFECTION
USING ULTRAVIOLET LIGHT ^
The presented standards show regulations from States that follow the 1966 guidelines published by DHEW
and regulations from States that follow the ANSI/NSF international standards for ultraviolet light use in
drinking water disinfection. The DHEW guidelines require a minimum ultraviolet dose of 16 mWs/cm2.
The ANSI/NSF standard for Class A units requires a minimum ultraviolet light dose delivery of 38
mWs/cm2. .-• •
UV Light Disinfection Technology in
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CHAPTER 1. BACKGROUND
This chapter discusses the history of artificial ultraviolet light and its application as a drinking water
disinfectant in the United States. The chapter presents a general description of ultraviolet light technology
and its mode.of action on microorganisms. Existing guidelines for the use of ultraviolet equipment for
the disinfection of drinking water are presented, and findings are introduced regarding the availability of
ultraviolet light disinfection equipment in the United States and the use of ultraviolet light in water and:
wastewater treatment. :'..-..'.'
To investigate the availability of ultraviolet equipment for use at potable water supplies and to obtain
current information on applications, the U.S. Environmental Protection Agency (USEPA) contacted
equipment manufacturers or manufacturer representatives, the Water and Wastewater Equipment
Manufacturer's Association, Inc. (WWEMA), the American Water Works Association (AWWA), the
National Sanitation Foundation (NSF) International, the Water Quality Association (WQA), the Food and
Drug Administration (FDA), the National Institute for Occupational Safety and Health (NIOSH), and
universities involved in ultraviolet light research. Additionally, European and other nations' guidelines
and experience in using ultraviolet light in drinking water disinfection were investigated. The European
Union representation library in Washington, DC, provided available information on the European drinking
water directive, and the literature search provided a Wealth of scientific findings on ultraviolet light
applications in drinking water. --.""•-'
' / - - ' . . ' • ' •
This chapter is organized as follows: Section 1.1 presents an introduction to natural and artificial
ultraviolet light, as well as a brief explanation of how ultraviolet light inactivates microorganisms and the
wavelength range at which ultraviolet light is most effective. Section 1.1 also presents some historic
background information on ultraviolet radiation treatment. Section 1.2 presents a general description of
ultraviolet light technology and the types available for drinking water and wastewater disinfection
applications. Section 1.3 presents existing official and non-official guidelines for ultraviolet disinfection
in the United States 'and in Europe. Section 1.4 discusses the availability of ultraviolet light disinfection
equipment in the U.S. market. Section 1.5 discusses the extent of ultraviolet technology applications in
water and wastewater treatment.
UV Light Disinfection Technology in ' • -.
Drinking Water Application—An Overview 1-1 Final—September 1996
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Chapter 1—Background
1.1 INTRODUCTION TO ULTRAVIOLET LIGHT
Ultraviolet treatment in drinking water involves the direct exposure of the water stream to ultraviolet light.
Exposure to the ultraviolet light damages and changes the nucleic acids of microorganisms present in the
water, thus preventing them from propagating or remaining active (see Exhibit 1-1).
Naturally occurring ultraviolet light is situated beyond the visible spectrum at its violet end: It has a
wavelength shorter than that of visible light (400 nm - 750 nm1) and longer than those of the X-ray
wavelengths (0.1 nm-lOOnm). Ultraviolet radiation is subdivided into three regions: (1) near-ultraviolet
(400 nm - 300 nm), which is present in sunlight as it reaches the earth and produces important biological
effects; (2) middle-ultraviolet (300 nm - 200 nm), which is not present in sunlight as it reaches the earth
(because of the ozone layer) but is transmitted through the air; and (3) the extreme-ultraviolet (200 nm -
100 nm2), which is not transmitted through the air (Van Nostrand, 1989 and Zumdahl, 1989). The
division of the ultraviolet light spectrum described in the medical/pharmaceutical literature is (1) UV
(100 nm - 200 nm), (2) UVA (200 nm - 290 nm), (3) UVB (290 nm - 320 nm), and (4) UVC (320 nm -
400 nm) (Fessenden and Fessenden, 1986; Sobotka, 1993). Meulemans (1987) puts the division as
follows: UVa (400 nm - 315 nm), UVb (315 nm - 280 nm), UVc (280 nm - 200 nm), and Vacuum-UV
(below 200 nm). Another ultraviolet light spectrum division used in the scientific literature is (1) UVA
(400 nm - 320 nm), (2) UVB (320 - 290 nm), and (3) UVC (290 - 100 nm). Exposure to UVA and UVB
(200 nm - 320 nm) for extended periods of time is known to cause mutation and skin cancer among
humans and animals. In humans, at about 295 nm, ultraviolet light causes sunburn, between 280 and 300
nm it gives rise to Vitamin D, and between 300 and 400 nm it causes browning of the skin (Ellis, 1991).
For purposes of clarity this report will treat ultraviolet light spectrum and other characteristics,
independently of the above classifications.
Artificial ultraviolet radiation is emitted by nearly all light sources (regular light bulbs, halogen bulbs,
high-efficiency mercury-containing light bulbs, television and computer screens, and heat lamps). The
transmission of ultraviolet light hi the shorter wavelength region increases with the increase of excitation
(current) or the temperature of the light source (heat lamps and halogen lamps emit more ultraviolet light
'nm » nanometer; 1 nm = 10"9 m
boundary between the ultraviolet region and the X-ray region at this point is rather arbitrary and could be seen in
some references as 10 nm. •
UV Light Disinfection Technology in
Drinking Water Application— An Overview 1-2 Final— September 1996
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Chapter 1—Background
Exhibit 1-1. Ultraviolet Light Mode of Action on Microorganisms
wavelWhs of electromagnetic radiation. At a wavelength of
Qf d^^eic apid (DNA) fi $
DNA is the molecule in a cell that is unique to it and its species. The DNA molecule contains all
S3? cDNA°rCtn?cl7™ ™f ,rlioati°n- RNA "*nscribes ^««*SlS?SS
in me UNA so that the cell can make the enzymes needed to make the organic constituents
celL The monomenc units of DNA and RNA, called nucleotides, contain nlS^SiSlSSS
components The nrtrogenous heterocyclic components are uracil, thymine, fytosine aSe and
guanne.Ultrav.olet Hght causes the formation of dimers such as hymine-thvrSe
cytos.ned.mers, cytosine-thymine dimers, and uracil dimers (Gaud^d
AnSnH6 pf ^ *" * ""•*" b™« be00ine OUt °f ^^f
Appendix B) and form a new bond with electrons from another molecule.
h ?!-n5lLy dimers a'°ng a DNA strand may inhibit replication, which is lethal to the cell
the ultraviolet light dose was insufficient to cause complete replication inhibition ^ then reolicatinn
.S^SS T±fc "IT C°?et IT" in9 t0 mUt' nt P^U tha^f SnaLle to IS
{ n 7 I )- An insufflcient ultraviolet dose may cause limited damage to the DNA which
celUnder favorable conditions, can repair using terepair enzymes. vlrSes have nc Trepair
enzymes so they use the repair enzymes of the host cell. The phenomena of ceH reaSL
* ^^ ^ °f
o
II
• c.
• N'
C CH3 HN*
I
O~
Thymine
O
II
• C.
•N-
-CH3 ,
UV
Thymine Dimer
ultv
ultraviolet
nht shpectr"m f DNA in ac?ueous solution presented below show two peaks of maximum
hght absorpt.on (von Sonntag and Schuchmann, 1992) at about 200 nrn wavelenoth and
350
nm
e - Molar decadic absorption coefficient in L/moI/cm.
M - Molar concentration.
UV Light Disinfection Technology in
Drinking Water Application—An Overview
1-3
Final—September 1996
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Chapter 1—Background
than regular light bulbs). For example, "Tungsten lamps in quartz envelopes radiate in the ultraviolet
range in accordance with Planck's law, slightly modified by the emissivity function of tungsten. Because
of its high temperature (3,800°K), the crater of an open carbon arc is an excellent source of ultraviolet
radiation, extending to violet emission, mainly in lines and bands. A widely used source of ultraviolet
light is the quartz mercury arc" (Van Nostrand, 1989). The inverse relationship between light energy and
wavelength is explained by the following formula:
E = hv
where:
E = Energy in Joules or in watt second
h = Planck's Constant in joules second
v (nu) SB Frequency in hertz or sec"1
"i
c s= speed of light in m/sec = 2.9979 x 10s m/sec
X s= wavelength in m.
C
Therefore E = h.— and the shorter the wavelength, the greater is the energy of the photon transmitted.
Af
For example, the energy of a photon at 253.7 nm is
Psh c , (6.63xlO-"Joules second) (3.0 xlO*m/s) _, ^1ft.m^ _ „ AOM
* (2.537xlO-7m)
and the energy of a photon emitted at 185 nm is E = 10.8 x 10"19 Watt sec or 6.75 eV.
For water treatment applications two wavelengths are of interest. These wavelengths are 254 nm and 185
nm. These wavelengths are of interest because at these wavelengths ultraviolet radiation significantly
affects microorganisms and certain organic chemicals, and because commercially available low-pressure
mercury lamps omit most of their ultraviolet light energy at these wavelengths.
The optimum ultraviolet light wavelength range for bactericidal effect is between 250 nm and 270 nm;
This was determined by measuring the inhibiting effect of ultraviolet light at different wavelengths on
i
bacterial colony formation (Oda, 1969, as cited in USEPA, 198.6). Exhibit 1-2 shows the most effective
spectrum of ultraviolet light for bacterial colony formation inhibition. As can be seen from Exhibit 1-2,
the colony forming bacteria is more sensitive to ultraviolet light at a wavelength range of 250 nm to 270
nm than at shorten (high energy wavelengths). Microorganisms other than the tested colony forming
bacteria might be more sensitive to ultraviolet light emitted at a different wavelength range. For example,,
nematodes, worm eggs and tobacco mosaic virus are more sensitive to ultraviolet light emitted at 220 nm
(Legan, 1980 as cited in Masschelein, 1992). The literature search did not reveal any practical application
of ultraviolet light microorganisms inactivation in the range of 190 nm to 210 nm wavelength, i.e.,
corresponding to DNA absorption spectrum finding by von Sonntag and Schuchmann, 1992.
UV Light Disinfection Technology in .
Drinking Water Application—An Overview 1-4 Final—September 1996
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Chapter 1—Background
Exhibit 1-2. Relative Bactericidal Effectiveness as a Function of Wavelength
(Oda, 1969, as cited in USEPA, 1986)
S
25O
Wavelength (nm)
3OO
O22E-1S
The experimental use, of artificial ultraviolet light-emitting low-pressure mercury vapor lamps dates back
to 1835 in Europe (Bryant, Fulton, and Budd, 1992). The use of artificial ultraviolet light to disinfect
drinking water in the United States dates back to 1916. Between 1916 and 1928, at least four water
authorities in the United States used ultraviolet light for disinfection. The highest reported treated flows
were 96 to 135 liters per second (1/s) (2.2 MOD to 3.1 MGD) serving a population of up to 12,000
(Jepson, 1972, as reported in- Witherell, Solomon, and Stone, 1979). Today, the wide array of ultraviolet
light treatment systems used for disinfection of water and wastewater, the increase in demand, and the
experience gained over the years within the United States and .abroad have led to a new generation of
ultraviolet systems, for water and wastewater disinfection applications. Many of the old problems that
plagued the industry from its early years to the mid 1980s, such as costs and problems with operation and
maintenance (O&M) (e.g., water leaks), have been solved or have become. manageable (Witherell,
Solomon, and Stone, 1979; Aquafine, 1995). Furthermore, ultraviolet technology is a major and essential
element and component in the disinfection processes used in the food and the pharmaceutical industries
and other specialized industries that require.pathogen-free and chemical-free sterile water (NIOSH, 1995).
-„ - , . . ^ . ^
Cost trends show a decline as more ultraviolet light technology has been developed and used in water and
wastewater disinfection processes (Hoehn, 1976, USEPA, 1992b, USEPA, 1993a, USEPA, 1993b). In its
most recent study on ultraviolet use for disinfecting wastewater, the Water Environment Research
UV Light Disinfection Technology in
Drinking Water Application—An Overview
1-5
Final—September 1996
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Chapter 1—Background
Foundation (WERF, 1995) provided annualized costs (capital and O&M) that clearly show the economic
feasibility of ultraviolet technology for wastewater disinfection. The study shows that the costs of
ultraviolet systems vary widely; nevertheless, these-costs are considerably less than the costs of
comparably designed chlorination systems for treating wastewater effluents. The costs provided in the
WERF study reflect the costs of ultraviolet systems designed to deliver a minimum dose of 140 milliWatts
second per square centimeter (mWs/cm2) of ultraviolet light.
1.2 GENERAL DESCRIPTION OF ULTRAVIOLET LIGHT TECHNOLOGY
Ultraviolet radiation is generated by striking an electric arc through mercury vapor contained in a lamp.
Because ordinary glass absorbs ultraviolet light, the lamp is made of special ultraviolet light transmitting
quartz, polymer or silica. There are several types of ultraviolet lamps, including the low-pressure mercury
vapor lamp, which emits primarily at a wavelength of 253.7 nm (approximately 85% of the light energy
emitted) with a lesser output at 184.9 nm. The low-pressure mercury vapor lamp is the lamp that is used
primarily for drinking water treatment. Exhibit 1-3 shows the emission spectrum of a low-pressure
mercury lamp and a medium-pressure mercury lamp, demonstrating that in low-pressure lamps, most of
the ultraviolet light energy is emitted at 254 nm wavelength, while in a medium-pressure lamp, the
ultraviolet light energy is emitted across a broad range of the visible light and ultraviolet light portion of
the spectrum. Exhibit 1-3 was constructed from spectrum tables cited in Legan, 1982. The medium-
pressure mercury vapor lamp is used primarily for treatment of wastewater and water contaminated with
organic compounds, typically for contaminated groundwater. .
When the electrons in the electric current run through the mercury vapor, the excited mercury molecules
emit ultraviolet light. A good portion of the electric energy is transformed into heat, which necessitates
- ' f '.
quartz sleeves that are larger in diameter than the lamp itself (1.5 to 2.5 cm in diameter) to encase the
lamp. This quartz sleeve serves as an important barrier between the cool water flow and the hot lamp.
Ultraviolet technology applications in water and wastewater fall into two categories: closed systems and
open channel systems. The closed systems can be .further, subcategorized as either contact units or non-
contact units. Contact units consist of ultraviolet lamps encased in quartz around which the water or liquid
to be disinfected flows. Non-contact units are designed such that the ultraviolet lamps transmit energy
to Teflon pipes through which the water or liquid to be disinfected flows. The open channel systems
consist of submerged ultraviolet lamps either vertically or horizontally suspended in an open channel.
Exhibits 1-4,1-5,-1-6,1-7, and 1-8 present schematic drawings of different types of ultraviolet systems
UV Light Disinfection Technology in
Drinking Water Application—An Overview. 1-6 Final—September 1996
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Chapter 1—Background
Exhibit 1-3. Emission Spectra of Low-Pressure and Medium-Pressure Mercury Lamps
(based on Legan, 1982)
100.0%
80.0%
.£* •
J . 60.0%
j| 40.0%
20.0% -
0,0%
Low Pressure (85W)
1367 11291014 S7854fi4»«B3663443I33a3»72a9280275279z6S2S72S4Z48Z4023ZI85
Wavelength (nm)
100.0%
80.0%
60.0%
4ao%
20.0% -
0.0%
Medium Pressure (7,500W)
13*7 U29MM4 578 546 436 «5 3» 344 313 3(B 2»7 289 MO 275 I7D 2«S 237 254 Z« 2« 232 MS
Wavelength (nm)
t/K L/g/>f Disinfection Technology in
Drinking Water Application—An Overview
1-7
Final—September 1996
-------
Chapter 1—Background
Exhibit 1-4. Non-Contact Ultraviolet Disinfection Unit
(USEPA,1986)
ftemovabto Lamp Support Rack
with Imtcrwl Wiring
Teflon Tuba* to
Carry WMW
— 15cm
Lamp
' 16cm
Teflon Tub** |
(8cmerjJtan 15em
16 era
UK 1/g/jf Disinfection Technology in
Drinking Water Application—An Overview.
1-8
Final—September 1996
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Chapter 1—Background
Exhibit 1-5. Closed Vessel Ultraviolet Reactor
(USEPA, 1986)
IttumfewMdUfnp
Monitor InQ Pjml
QiurtzJccuts
Endra'ng UV Limp*
UVImtnrty
M«MuringC«H
UV Light Disinfection Technology in
Drinking Water Application—An Overview
1-9
Final—September 1996
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Chapter 1—Background
§5
tiT
tr
ui
0)
I
1
I
o
S
a-
.i
.S
O
I
s*
1
i
{/f t/sr/jf Disinfection Technology in
Drinking Water Application—An Overview.
1-10
Final—September 1996
-------
Chapter 1— Background
O)
u.
DC
UJ
CD
I
(0
c
(0
O
0>
Q.
O
as
aviolet Lamps
•o
0)
s
o
«s
I
o
JD
z
HI
t/l^ L/g/if Disinfection Technology in
Drinking Water Application—An Overview
1-11
Final—September 1996
-------
Chapter 1—Background
Exhibit 1-8. Example of Lamp Arrangement in an Ultraviolet Reactor
(USEPA, 1986)
Centeriine Spacing
(Horizontal)
.,
Sv Centerline Spacing
(Vertical) ' •
Liquid Volume/Lamp
-4-4-
Quartz I
Sleeve '
Lamp (Typical)
(a) Uniform Array
(b) Staggered Uniform Array
UV Light Disinfection Technology in
Drinking Water Application—An Overview- 1-12
Final—September 1996
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Chapter 1—Background
and lamp arrangements. Open systems are commonly used in wastewater applications, while closed
systems are commonly used in drinking water applications ito maintain positive pressure thus avoiding the
need to repump and to minimize contamination.
1.3 EXISTING GUIDELINES FOR ULTRAVIOLET LIGHT DISINFECTION IN
DRINKING WATER APPLICATIONS
V ... _. . :_
In this section, standards and guidelines set by Federal and State agencies and nationally recognized
institutions are presented. In addition, the available standards from Europe are presented. The current
guidelines in place for the use of ultraviolet radiation for drinking water disinfection on ships were
released by the U.S. Department of Health, Education, and Welfare ,(DHEW), Public Health Division of
Environmental Engineering and Food Protection, in 1966. The guidelines require a minimum dose of 16
milliwatts second per square centimeter (mWs/cm2) at all points throughout the water disinfection chamber.
The policy statement requires that a 3-inch maximum distance be kept between the surface of the lamp
and the walls of the chamber. Evidently, this low dose requirement, as well as other early O&M issues,
led to problems that were evident,on vessels using ultraviolet light for water disinfection (DHEW CDC,
1974). . '••'.•'.••
Several States in the United States recognize ultraviolet light technology as an acceptable technology for
disinfecting ground water. The State of New Jersey, and the State of Pennsylvania as stated in their
drinking water regulations and following the guidelines of DHEW, require a minimum dose of 16
mWs/cm2 (NJ, 1985) to be applied to disinfect ground water sources. Other States, allow the use of
ultraviolet light in disinfecting drinking water on a case-by-case basis. At least five States' codes'
, • ' - y
(Arizona, Delaware, Massachusetts, North Carolina, and Wisconsin) require that an ultraviolet light
disinfection system meet ANSI/NSF Standard 55-1991 (discussed below), while at least four other States
(Alaska, Idaho, Kansas, arid Vermont) forbid the use of ultraviolet light for water disinfection in public
water systems. -
Appendix D of this report contains samples of State criteria for ultraviolet treatment for non-community
public and private water supplies. Appendix D also includes the main section of ANSI/NSF Standard 55-
1991, The State of Wisconsin requires that systems meet the ANSI/NSF Standard 55-1991 for Class A
treatment units. It also has set criteria for ultraviolet water treatment devices used at non-community '
public water supplies, to control microbiological contamination (Wisconsin Department of Natural
Resources [DNR], Nov. 17, 1995). In the State of Wisconsin, eligibility is based on a finding of
UV Light Disinfection Technology in
Drinking Water Application—An Overview 1-13 Final—September 1996
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Chapter 1—Background
microbiological contamination, based on positive total coliform or Escherichia coli tests, failure of system
batch chlorination to eliminate the problem, and a decision that well reconstruction or replacement would
not correct the problem. Water quality characteristics (with "maximum" and "preferred" levels) have been
specified in addition to detailed design and operational criteria, among which are the following:
• Ultraviolet radiation at 253.7 nanometers wavelength with minimum dose of 38 mWs/cm2.
• Quartz or high silica glass jacket and stainless steel housing materials.
* Assemblies must provide accessibility for viewing, cleaning and replacements.
• An alarm and automatic shutdown valve triggered by lamp failure or dose deficiency.
• Identical parallel ultraviolet systems.
• Su,,, sediment prefilter and a cyst reduction filter.
Coliform monitoring, turbiduneter installation on systems exhibiting turbidity variation, and record keeping
provisions are also included (WI, 1995). As stated earlier, Appendix D contains the Wisconsin DNR
criteria in addition to other States criteria for ultraviolet drinking water disinfection systems.
«
Ultraviolet light equipment installed hi water vending machines is regulated by the PDA. The FDA
"standard" for the use of ultraviolet light for disinfecting water sold in these machines is part of the Good
Manufacturing Practice Code. The Code is somewhat vague in that, it requires only that the equipment
disinfect the water; it does not specify a minimum intensity, dose, or log reduction of a surrogate
microorganism (FDA, 1995).
The ANSI/NSF standard 55-1991, which covers Point-of-Use (POU) and Point-of-Entry (POE) ultraviolet
light applications, clearly states that these ultraviolet systems are not intended to be used with water that
has an obvious contamination source or to reuse treated wastewater hi drinking activities (ANSI/NSF,
1991). ANSI/NSF 55-1991 differentiates between POU and POE systems. Class A systems can be used
as POU or POE and require a minimum ultraviolet light dose of 38 mWs/cm2, based on the inactivation
of Bacillus siibtilis spores. Class B systems are POU systems with a minimum ultraviolet light dose of
16 mWs/cm2. This dose was determined based on the inactivation of Saccharomyces Cerevisiae yeast.
Because most vegetative bacteria (i.e., bacteria that propagate by non-sexual processes), including coliform
species, are too susceptible to ultraviolet radiation at the dose range of 16 mWs/cm2 to allow for
measurable testing, Saccharomyces cerevisiae was chosen as the test challenge to allow for a reasonable
influent concentration and an easily measured reduction in the effluent (ANSI/NSF, 1991).
UV Light Disinfection Technology in
Drinking Water Application—An Overview 1-14 Final—September 1996
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Chapter 1—Background
The protocol detailed in ANSI/NSF standard 55-1991 for sensitivity calibration of challenge organisms
requires that laboratory cultured microorganisms be suspended in buffered water. The ANSI/NSF standard
clearly states that the systems are, intended to be used on visually clear water. Class A systems can be
used on prefiltered surface water tested for cyst reduction in compliance with ANSI/NSF Standard 53.
Class B systems are intended to be used as supplemental bactericidal treatment and to reduce
non-pathpgenic or nuisance microorganisms only.
' " ~ N-
The European Union (EU) drinking water directive 80/788/EEC does not specify a treatment technology
or technologies for public water systems to achieve levels below the Maximum Admissible Concentrations
(MAC) specified for microbiological parameters. The EU directive 80/788/EEC microbiological
parameters include total coliforms, fecal coliforms, fecal streptococci, sulphite-reducing clostridia, and total
bacteria counts. (OJC, 1990, Bureau, 1992). The EU microbiological parameters are presented in
Exhibit 1-9.
Also, the EU drinking water'directive does not specify disinfection procedures or set a minimum
ultraviolet dose requirement. However, the directive specifies certain microorganisms for testing and
requires in a general statement that the water intended for human consumption be pathogen-free. Some
EU member states have a minimum dose requirement for ultraviolet light systems. In Norway, for
example, the minimum acceptable ultraviolet light dose for pretreated drinking water is 16 mWs/cm2
measured at the chamber wall (NIPH, 1989). In Austria, the minimum acceptable ultraviolet light dose
level for pretreated drinking water disinfection is 30 mWs/cm2 (Sommer and Cabaj, 1993)
1.4 AVAILABILITY OF ULTRAVIOLET TECHNOLOGIES FOR GROUND WATER
DISINFECTION
to determine the availability of ultraviolet systems hardware in the U.S. market, with emphasis on systems
used in water disinfection, USEPA attempted to obtain information to address the following questions:
• Is, there enough experience and knowledge about the technology to render the risks of using it
calculable or acceptable?
• Is the technology currently available, and can it be delivered in a reasonable time? Are the
equipment and spare parts available to the consumer in a reasonable time?
• Is the use of the technology economically feasible?
UV Light Disinfection Technology in
Drinking Water Application—An Overview 1-15 Final—September 1996
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Chapter 1—Background
Exhibit 1-9. EU Microbiological Parameters Drinking Water Directive 80/778/EEC
Water intended for human consumption should not contain pathogenic organisms. If it is
necessary to supplement the microbiological analysis of water intended for human consumption,
the samples should be examined not only for the bacteria referred to below but also for
pathogens including the following: .
• Salmonella
• Pathogenic staphylococci ,
• Fecal bacteriophages ;
• Enteroviruses.
Nor should such water contain the following:
• Parasites
• Algae
• Other organisms such as animalcules (worms-larvae).
Parameters
Total Coliforms*
Fecal Coliforms
Fecal streptococci
Sulphite-reducing
Clostridia
Results: ,
Volume of "the ~
Sample in ml
100
100
100
20
Guide Level (GL)
_--'
- ' '
—
—
Maximum Admissible Concentration
(MAC)
Membrane Filter
Method
0
0
0
'
Multiple Tube
Method (MPN)
MPN < 1
MPN < 1
MPN<1
MPN < 1
Parameters
Total bacteria
counts for water
supplied for
human
consumption
Total bacteria
counts for water in
closed containers
Temperature
37°C
22°C
37°C
22°C
, Results:
Volume of the
Sample in ml
1
1
1
1
Guide Level (GL)
10b,c
100b'c
5
20
Maximum
Admissible
Concentration
(MAC)
"
— ' • .
20d
100d
* Provided a sufficient number of samples is examined (95% consistent results).
b For disinfected water the corresponding values should be considerably lower at the point where it leaves
the processing plant.
6 If, during successive sampling, any of these values is consistently exceeded, a check should be carried out.
d MAC values should be measured within 12 hours of being put into closed containers with the sample water
being kept at a constant temperature during that 12-hour period.
UV Light Disinfection Technology in
Drinking Water Application—An Overview
1-16
Final—September 1996
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Chapter 1—Background
Exhibit 1-9. EU Microbiological Parameters Drinking Water Directive 80/778/EEC
(Continued) , - '
Parameter
Total Coliforms
Fecal Coliforms
Fecal Streptococci
Sulphite-Reducing
Clostridia
Total Counts
Salmonella
Pathogenic
Staphylococci
Fecal
Bacteriophages
Enteroviruses
Protozoa
Animalcules
(worms - larvae)
- . - _ . •---.-
Analytical Method
Fermentation in multiple tubes. Subculturing of the positive
tubes on a confirmation medium. Count according to MPN
(most probable number).
Membrane filtration and culture on an appropriate medium
such as Tergitol lactose agar, endo agar, 0.4% Teepol
broth, subculturing and identification of the suspect colonies
• Incubation temperature for total coliforms: 37°C
• Incubation temperature for fecal coliforms: 44°C
Sodium azide method (Litsky). Count according to MPN —
Membrane filtration and culture on. an appropriate medium.
A spore count, after heating the sample to 80°C by:
• Seeding in a medium with glucose, sulphite and iron,
counting the black-halo colonies
• Membrane filtration, deposition of the inverted filter on a
medium with glucose, sulphite and iron covered with
agar, count of black colonies
• Distribution in tubes of Differential Reinforced Clostridia!
Medium (DRCM), subculturing of the black tubes in a
medium of litmus-treated milk, count according to MPN.
Inoculation by placing in nutritive agar.
Concentration by membrane filtration. Inoculation on a pre-
enriched medium. Enrichment, subcuituring on isolating
agar. Identification.
Membrane filtration and culture on a specific medium (e.g.,
Chapman's hypersaline medium). Test for pathogenic
characteristics.
Guelin's process.
Concentration by filtration, flocculation or centrifuging, and
dentification.
Concentration by filtration on a membrane, microscopic
examination, test for pathogenicity.
Concentration by filtration on a membrane, microscopic
examination, test for pathogenicity. -' ,
Incubation
Period
24 to 48 hours
24 to 48 hours
24 to 48 hours
24 to 48 hours
48 to 72 hours
. f
UV Light Disinfection Technology in
Drinking Water Application—An Overview
1-17
Final—September 1996
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Chapter 1—Background
This study identified 14 firms in the United States that manufacture and/or distribute ultraviolet light
equipment for disinfection of water and other media. Ultraviolet light technology is used extensively for
disinfection and sterilization in the food industry, electronics industry, spas and swimming pools, ships,
the health industry (hospitals, clinics, and pharmaceutical manufacturing facilities), wastewater facilities
and laboratories. Other applications of ultraviolet, technology include special applications in the space and
defense industries, testing and monitoring equipment industry, and chemical manufacturing industry.
(Zumdahl, 1989).
Ultraviolet light is not used extensively at drinking water facilities in the United States. According to the
American Water Works Association (AWWA, 1992), about 500 drinking water treatment facilities use
ultraviolet light for disinfection in North America. More recent data show that more than 1,000 drinking
water treatment facilities in the United States use ultraviolet light for disinfection, alone or in combination
with a secondary disinfectant (PA, 1996 and NY, 1995).
Ultraviolet light for drinking water disinfection is also used in POU systems, water-vending machines, and
private homes (McSwane, 1994). Exhibit 1-10. presents a list of manufacturers/distributors of ultraviolet
light equipment in the United States. Most of these firms are located on the East Coast, and a few are
in California. Exhibit 1-10 includes six foreign firms (Swiss, Canadian, and British) that export ultraviolet
equipment to the United States. The list provided in Exhibit 1-10 was compiled from different sources
and is believed to be a comprehensive list of ultraviolet light manufacturers of products for water and/or
wastewater disinfection or remediation from organic contamination (NIOSH, 1995).
In public facilities (water and wastewater), most of the current ultraviolet light disinfection market is in
the wastewater treatment field. The ultraviolet equipment designed and manufactured to disinfect waste-
water delivers intensities that are much higher than the intensities generally used for drinking water
disinfection.
There are three available types of ultraviolet light disinfection systems in the U.S. market. The two most
widely used types are (1) the closed chamber ultraviolet disinfection system and (2) the open channel
ultraviolet disinfection system. A third closed system called the non-contact reactor is also available but
not as popular as the other two. The open channel system is used mainly for large flows (roughly 2,000
GPM or 2.9 MOD). This system does not require pumping and usually is custom designed. The closed
chamber system is used for small flows (with units that can handle up to 600 GPM per unit). This system
UV Light Disinfection Technology in
Drinking Water Application—An Overview 1-18 Final—September 1996
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Chapter 1—Background
Exhibit 1-10. List of Companies and Individuals That Are Actively Involved in the
Ultraviolet Industry, Either as Manufacturers or as Major Distributors3
Mr. De Vos, President
AMWAY Corporation
7575 East Fulton Road
Ada, Ml 49355
(616)787-6279 - • •
Ms. Roberta Veloz, President
,Mr. Bak Srikanth, Senior Applications Engineer
Aquafine, Corporation
25230 West Avenue Stanford
Valencia, CA 91355
(800) 423-3015 ext. 651 or
(805) 257-4770; fax: (805) 257-2489
Ms. Colleen O'Neil
Aquafine Wedeco Environmental Systems, Inc
25647 Rye Canyon Road
Valencia, CA 91355
(800) 992-1314
fax:(805)257-5870
Mr. David McCarty> President
Aquionics, Inc.
21 Kenton Lands Road
P.O. Box 18395
Ertanger, KY 41018
(606) 341-0710; fax: (606) 341-2302
Mr. Hilary-Boehme, President
Contact person: Ms. Ann Wysocki, Marketing Director
Atlantic Ultraviolet Corporation
375 Marcus Boulevard
Hauppauge, NY 11788
(516) 273-0500; fax: (516) 273.0771
Mr. Steven W. Rerce, President • '
Contact person: Mr. Leon Martin
Capital Controls Company .
3000 Advance Lane
P.O. Box 211
Colmar, PA 18915
(215) 997-4000; fax: (215) 997-4062
vlr. Karl Scheible, President •
Hydroqual, Inc.
1 Lethbridge Plaza «
Mahwah, NJ 07430
201) 529-5151; fax: (201) 529-5728
Mr. Mark Kurtz
Contact person: Jesse Rodriquez
Ideal Horizons .
1 Ideal Way
Putney, VT 05764
(802) 287-4488; fax: (802) 287-4486
Mr. Art Shapiro
Contact persons: Mr. Geronomo Balallo,
Mr. Kevin Smith, Mr. Mervyn Bowen
Infilco-Degremont
8924 Emerywood Parkway
Richmond, VA 23294
(800) 446-1150; fax: (804) 756-7643
Mr. John Kenin
Contact person: Mr. Peter Waldrin ext 434
Ionic Corporation . • •
65 Grove Street
Watertown, MA 02172
(617) 926-2500; fax: (617) 926-4304
Mr. Donald Lander, Vice President
Pure Pulse
8888 Balboa Avenue
San Diego, CA 92123 ' .
(619) 496-4100; fax: (619)576-1377
Mr. Charles R. Reading, Jr., Director
Safe Water Solutions L.L.C.
20 Hollow Horn Road
Erwinna, PA 18920 •
(610) 294-9376; fax: (610) 294-9590
Mr. Jim Donallen, President
Ultra Dynamics Corporation ' •
299 W. Fort Lee Road
Bogata, NJ 07603
(800) 727-6931; fax: (201) 489-9229
Mr. Bill Himebaugh
Ultrox Division of ,25mpro Environmental
7755 Center Avenue, #1100
Huntington Beach, CA 92647
(714) 545-5557; fax: (714) 557-5396
Foreign Companies Involved in Ultraviolet Applications in the United States
vlr. Marc Parella
Bailey, Fischer & Porter •
134Norfinch
Jownsview, Ontario MSN 1X7, Canada
416) 667-9800; fax: (416) 667-8469
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Chapter 1—Background
requires pumping but is more readily available and is easier to install. The ultraviolet industry can deliver
standard closed system units in less than 4 weeks. The ultraviolet industry claims that it can assess the
requirements (or design), ship, and install a closed system in 4 to 8 weeks on average and an open channel
system in about 12 weeks.
The ultraviolet units available in the market are used as stand-alone treatment systems or as a part bf a series
of other drinking water treatment, processes. A common treatment train using ultraviolet light for
contaminant removal and disinfection of ground water sources involves a combined ozone or hydrogen
peroxide process along with ultraviolet application. Therefore, it is common to find that the manufacturers
of ultraviolet equipment are ozone equipment manufacturers as well. Furthermore, the industry also provides
ultraviolet equipment (mainly the closed chamber units) for short-term uses. Rental units are used in. cleanup
and emergency situations, such as ground water contaminated with spilled toxic organic compounds.
1.5 ULTRAVIOLET LIGHT SYSTEMS IN WATER AND WASTEWATER
APPLICATIONS
The American Water Works Association (AWWA, 1992) reported that more than 2,000 water treatment
facilities in Europe use ultraviolet light for disinfection.
In the United States, more than 1,000 drinking water treatment facilities use ultraviolet light for
disinfection, alone or in combination with a secondary disinfectant. For example, in the State of New
York, 6.4 percent of ground, water systems with some kind of treatment (264 ground water systems-out
of 4,141 ground water systems with treatment records) use ultraviolet light for drinking water disinfection'
(NY, 1995). ,
In the State of Pennsylvania, of the 10,700 PWS systems, 761 systems use ultraviolet light for disinfection
alone or in combination with a chlorine disinfectant at 843 treatment facilities. All the systems using
ultraviolet light for disinfection are ground, water systems. Out of the 843 treatment facilities, only 26
treatment facilities use ultraviolet light in combination with a chlorine disinfectant. These figures do not
include bottled water systems, vending water systems, bulk water hauling, or retail systems that often use
ultraviolet light for disinfection. About 77 percent of the systems using ultraviolet light for disinfection
are TNC ground water systems, 18 percent are NTNC ground water systems, and 4 percent CWS ground
water systems (percentages do not add to 100 because of rounding). The statistics of population served
by these systems show that 82 percent of the systems serve less than 200 people and 96 percent of the
UV Light Disinfection Technology in
Drinking Water Application—An Overview, 1-20 Final—September 1996
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Chapter 1—Background
systems serve less than 500 people. During Pennsylvania State fiscal year 1995, less than 3 percent of
the drinking water systems using ultraviolet light for disinfection experienced MCL bacteriological
violation (PA, 1996). The State of Pennsylvania requires a minimum ultraviolet light dose of 16 mWs/cm2
for drinking water •disinfection (see appendix D).
Ultraviolet disinfection has been employed in European drinking water treatment plants since 1955.
Ultraviolet disinfection became very popular following the awareness about the dangers of trihalomethanes
(THM) formation during chlorination (Zoeteman et al., 1982). Exhibit 1-11 shows a profile of ultraviolet
light applications in drinking water in three European countries. As can be seen from Exhibit .1-1.1, the
number of water treatment plants using ultraviolet light for drinking water disinfection in Norway rose
from no plants to 400 plants in a period of 10 years. Tiiis indicates that, in Norway, ultraviolet technology
is a feasible and demonstrated technology when compared to other disinfection technologies.
Exhibit .1-11. Application of Ultraviolet Disinfection in Three European Countries
•-,-'. (Kruithof, 1992)
Country
Switzerland
Austria , -
Norway
First Application
1955
1955
1975
Number of Installations
in 1985
500
600
400
Maximum Capacity
m3/hr (gpd)
400 (2,536,060)
500 (3,170,075)
1,000(6,340,149)
In the Netherlands, ultraviolet light has been applied to disinfect drinking water. Ultraviolet technology
is used to destroy Escherichia coli and Aeromonas bacteria or to decrease colony counts in ground water,
as well as in bank-filtered water following GAC filtration. Ultraviolet light also is used to replace post
chlorination in extensively pre-treated surface water (Kruithof et al., 1992). The capacity of treatment
plants that use ultraviolet light for disinfection in the Netherlands is between 80 and 2,700 m3/hr (0.5
MOD to 17.1 MOD) with the majority between 0.5 and 5.1 MOD. Kruithof et al. (1992) reported that
the largest surface water plant in the Netherlands (18,000 m3/hr [114 MOD]) is considering the use of
ultraviolet disinfection with medium pressure mercury lamps for organics control and disinfection. The
purpose of employing ultraviolet light for disinfection in three out-of four under construction and planned
water treatment plants in the Netherlands (Kruithof et al., 1992) is to reduce bacterial colony counts (plate
count agar at 37°C) in the finished water. The water sources for these under construction and planned
plants are surface and bank-filtered water.
UV Light Disinfection Technology in
Drinking Water Application—An Overview
1-21
Final—September 1996
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Chapter 1—Background
Wolfe (1990) reported that a 14.5 MOD drinking water treatment in London, England, uses ultraviolet
light for primary disinfection and chlorine for residual disinfection. The treatment plant uses an array of
low-pressure ultraviolet lamps in combination with 16 medium pressure lamps.
. *
Unlike chemical disinfectants, continuous use of ultraviolet light and overdosing does not pose any known
health risks. Gilpin et al. (1985) investigated the applicability of ultraviolet light to disinfect recirculating
water in systems such as whirlpools and hydrotherapy tubs in hospitals. Gilpin et al. (1985) found that
at ultraviolet light intensity of 0.001 mW/cm2 and for a period ranging from 45 minutes to 90 minutes
(dose range 225 mWs/cm2 to 4.5 mWs/cm2) all tested Legionella spp. and pseudomonas aerugino.sa were
completely destroyed. The same inactivation results were obtained by chemical disinfection using a free
\ •
chlorine concentration of 2 mg/1 for 30 minutes. For recirculating water systems, continuous ultraviolet
light disinfection has the advantage of not requiring repeated chemicals additions and the advantage of not
altering the chemical nature of the water.
Sobotka (1992) studied the application of ultraviolet light in combination with ceramic filtration to
disinfect water in swimming pools, health facilities' pools, and water works. Sobotka (1992) reported that
ultraviolet disinfection capability improved when ceramic filters were used prior to ultraviolet treatment.
Also, Sobotka reported that ultraviolet treatment made it possible to reduce chlorine residue in therapeutic
pools in hospitals from 0.4 mg/1 to 0.2 mg/1.
In 1990, approximately 500 to 600 ultraviolet systems were operating in wastewater plants in the United
States (USEPA, 1992). The majority of ultraviolet operating systems were open-channel systems.
Exhibit 1-12 presents a comparison by category of ultraviolet systems in operation at wastewater treatment
plants between 1984 and 1990. As.can be seen from Exhibit 1-12, a significant shift from closed systems
to open-channel systems occurred in-wastewater application. The greatest share loss in system type
application was in the Teflon systems. This decrease in use is due to problems related to Teflon
degradation and cleaning considerations.
However, unlike wastewater application, ultraviolet light systems used in potable and sterile water
applications are more commonly closed systems. The ultraviolet industry representatives contacted
indicated that closed-chamber systems are the only systems used to disinfect and purify water in the
beverage and food industry, pharmaceutical industry, power generation industry, electronics industry,
UV Light Disinfection Technology in
Drinking Water Application—An Overview 1-22 Final—September 1996
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Chapter 1—Background
Exhibit 1-12. Ultraviolet Systems in Wastewater Applications in 1984 and 1990
Year
Number of Plants
<1 MGD
Flows 1-20 MGD
> 20 MGD
Closed Systems
Non-Contact (Teflon)
Contact
Open Channel
Horizontal Lamp Configuration
Vertical Lamp Configuration
Other
1984
50-60
80%
20%
84%
,35%
49%
8%
100%
8%
1990
500-600
50%
47%
3%
32%
7%
25%
66%
85%
15%
2%
(Source: USEPA, 1992) ,
\
household-type potable water applications, and total organic carbon (TOC) reduction applications in
contaminated ground water at Superfund sites.
The reasons for industry's preference for using the closed ultraviolet light system versus the open system
in water purification applications are the following: ;.
• Minimal or no exposure hazard to workers as compared to open-channel systems.
• Very small space requirement and low or no construction costs; For example, the dimensions
of a treatment chamber required to treat a 475 gpm (0.68 MGD) flow of water are 67x16x25
i . inches (Aquafine, 1995).
• Simplicity of installation because of modular design.
• Low maintenance, particularly with systems equipped with automatic mechanical wipers and/or
ultrasonic cleaners.
• The array of alarm systems that would alert an operator to minor or major problems. (With
monitoring systems mounted on the ultraviolet unit and/or connected to other remote monitoring
devices, a water treatment plant operator will always be alerted to any malfunction.)
• Minimal need to store chemicals (nonhazardous cleaning detergents or chemicals).
The components of an ultraviolet light unit that is used in a typical potable water disinfection application
are as follows:
UV Light Disinfection Technology in
Drinking Water Application—An Overview
1-23
Final—September 1996
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Chapter 1—Background
• A stable source of electricity. Low line voltage would result in a lower ultraviolet dose.
• A chamber made of stainless steel or any other material that is opaque and would not corrode
by the action of ultraviolet light or water passing through it.
• Ultraviolet lamps that are properly secured inside quartz sleeves with ease of access for
installation, replacement, or maintenance.
• Quartz sleeves that deliver the ultraviolet 'energy produced by the ultraviolet lamps with
sufficiently high transmission rates.
• Mechanical wipers to maintain optimum transmission between scheduled cleaning and
maintenance work.
• Sensors to monitor the ultraviolet intensity passing through the water. These sensors need to
be connected to alarm systems to alert the operator in case of low ultraviolet intensity. Easy
access to these sensors is necessary for installation, replacement, calibration, and maintenance.
• Safety control to shut off ultraviolet lamps in case of low flow levels and elevated lamp
temperature.
• Arc condition and lamp-out monitors to detect 'any fault condition and alert the operator.
• Electronic ballasts. •
UV Light Disinfection Technology in -
Drinking Water Application—An Overview 1-24 Final—September 1996
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Chapter 1—Background
1.6 REFERENCES
ANSI/NSF (1991). American National Standards Institute/National Sanitation Foundation International
Standard Number 55, Ultraviolet Microbiological Water Treatment Systems.
Aquafine (1995). Personal Communication with Mr. Bak Srikanth.
Aquafine (1995a). Aquafine Corporation Brochure. *
AWWA (1992). American Water Works Association. Comments on EPA's draft ground water
disinfection rule. '-
Bryant; E.A., Fulton, GJP., and Budd, G.C. (1992). Disinfection Alternatives for Safe Drinking Water.
Hazen and Sawyer Environmental Engineers & Scientists. New York: Van Nostrand.
DHEW CDC (1974). Recommendations on Vessel Sanitation. [As cited in Witherell L E Solomon R L
and Stone KM. (1979).]
Ellis, K.V. (1991). "Water Disinfection: A Review with Some Consideration of the Requirements of the
Third World." CRC Critical Reviews in Environmental Control, Vol. 20, No. 5/6, pp. 341-407.
Bureau (1992), "Drinking Water Directive 80/778/EC—Europe's views on Proposals for Modification."
Bureau Secretary General, Union of National Associations of Water Suppliers Aqua Vol 41 No 2
pp. 101-108. • •"•'.''"'
\ , ' = -
FDA (1995). CFR 21 Part 129.8a. Personal communication with Ms. Shelly Davis of the U.S. Food and
Drug Administration.
Fessenden, R.J. and Fessenden, J.S. (1986). "Speetroscopy I: Infrared and Nuclear Magnetic Resonance."
Organic Chemistry. Brooks/Cole Publishing Company, pp. 313-317.
Gaudy, A.F. and Gaudy, E.T. (1980). Microbiology for Environmental Scientists and Engineers
McGraw-Hill.
Gilpin, et al. (1985). "Disinfection of Circulating Water Systems by Ultraviolet Light and Halogenation "
Water Resources. Vol. 19, No. 7. pp. 839-848.
,Hoehn, R.C7 (1976), "Comparative Disinfection Methods." J. AWWA. June, pp. 302-308.
Jepson, J.D. (1972). "Disinfection of Water Supplies by Ultraviolet Radiation." Water Treatment and
Examination. Vol. 64, No. 6, p. 377 (as cited in Witherell, Solomon, and Stone, 1979).
Kruithof, J.C., van der Leer, R.C., and Hijneii, W.A.M. (1992). "Practical Experiences with UV
Disinfection hi the Netherlands." Aqua, Vol. 41, No. 2, pp. 88-94.
Legan, R.W. (1980). "Water Sewage Works." R56 (as cited in Masschelein, 1992).
Legan, R.W. (1982). "Ultraviolet Takes on CPI Role." Chemical Engineering. January 25, 1982. pp.
UV Light Disinfection Technology in
Drinking Water Application—An Overview 1-25 Final—September 1996
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Chapter 1—Background
Lund, V., and Ormerod, K. (1995). "The Influence of Disinfection Processes on Biofilm Formation in
Water Distribution Systems." Water Research. Vol. 29, No. 4, pp. 1013-1021.
Masschelein, WJ. (1992). "Unit Processes in Drinking Water Treatment." Marcel Dekker, Inc.
McSwane D.Z. (1994). "Drinking Water Quality Concerns and Water Vending Machines." Journal of
Environmental Health. Vol. 56, No. 10, pp. 7-10.
Meulemans, C.C.E. (1987). "The Basic Principles of UV-Disinfection of Water." Ozone Sci. Engineering,
9,299. (As cited in Ellis 1991). • ' .
NIOSH (1995). Personal communication with Gene Moss.
NIPH (1989). A Guidance for the Disinfection of Drinking Water. Ultraviolet Irradiation. National
Institute of Public Health (NIPH), OSLO, Norway. ISBN 82-7364-036-1 In Norwegian [as cited in Lund
and Ormerod, (1995)]
*
NJ Bureau of Safe Drinking Water (1985). Standards for the Construction of Public Non-Community and
Non-Public Water Systems NJAC 7:10 12.1 et seq.
NY (1995). New York State Groundwater Systems Statistics Table dated 3/3/95.
Oda, A. (1969). Ultraviolet Disinfection of Potable Water Supplies. Ontario Water Resources
Commission, Division of Research Paper EO12. (As cited in USEPA, 1986).
OJC (1990). "Council Directive 80/778/EEC of 15 July 1980 Relating to the Quality of Water Intended
for Human Consumption (as amended)." OJ L 353, Dec. 17th 1990. 80/778/EEC pp. 173-200.
PA (1996). E-mail from John Wroblewski of the Pennsylvania Department of Environmental Protection
to Mr. Marc Parrotta of the USEPA OGWDW.
Sobotka, J. (1992). "Application of Ultraviolet Radiation for Water Disinfection and Purification in
Poland." Water Science and Technology. Vol. 26, No. 9-11, pp. 2313-2316.
Sobotka, J. (1993). "The Efficiency of Water Treatment and Disinfection by Means of Ultraviolet
Radiation." Water Science and Technology. Vol. 27, No. 3-4, pp. 343-346.
Sommer, R. and Cabaj, A. (1993). "Evaluation of the Efficiency of a UV Plant for Drinking Water
Disinfection." Water Science and Technology. Vol. 27, No. 3-4, pp. 357-362.
USEPA (1986). Design Manual: Municipal Wastewater Disinfection. ORD. EPA 625/1-86/021.
USEPA (1992). Draft Groundwater Disinfection.Rule. July 31, Federal Register, Vol. 57, 33960.
USEPA (1992b). Office of Wastewater Enforcement and Compliance. UV Disinfection Technology
Assessment. EPA 832-R-92-004.
USEPA (1993a). Very Small Systems Best Available Technology Cost Document. Drinking Water
Technology Branch, OGWDW, USEPA, Washington D.C. Draft Document, Malcolm Pirnie, Inc.
UV Light Disinfection Technology in
Drinking Water Application—An Overview 1-26 Final—September 1996
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Chapter 1—Background
USEPA (1993b). Technologies and Costs for Ground Water Disinfection. Drinking Water Technology
Branch OGWDW, USEPA, Washington D.C. Draft Document Malcolm Pirnie^ Inc..
USEPA (1996). E-mail from Mr. Jon Merkel USEPA Region IX to Mr. Marc Parrotta USEPA OGWDW
dated 5/28/96.
Van Nostrand (1989). Ultraviolet. Van Nostrand's Scientific Encyclopedia, pp. 2887-2889.
von Sonntag, C., and Schuchmann, H.P. (1992). "UV Disinfection of Drinking Water and By-Product
'Formation—Some Basic Considerations." / Water SRT—Aqua. Vol. 41, No. 2, pp. 67-74.
WERF (1995). Comparison of UV Irradiation to Chlorination: Guidance for Achieving Optimal UV
Performance Disinfection. Water Environment Research Foundation publications.
WI (1995).- Wisconsin Department of Natural Resources, Criteria for Ultraviolet (UV) Water Treatment
Devices for Private and Non-Community Public Water Supplies to Control Microbiological Contamination.
November 17, 1995.
Witherell, L., Solomon, R., and Stone, K.M. (1979)v Ozone and Ultraviolet Radiation Disinfection for
Small Community Water Systems, pp." 1-39. '. .
Wolfe, R.L. (1990). "Ultraviolet Disinfection of Potable Water, Current Technical and Research Needs."
Environmental Science Technology, Vol. 24, No. 6, pp. 768-773. . .
Zoeteman, B.C.J., Hrubec, J., de Greef, E., and Kool, H.J. (1982).. "Mutagenic Activity Associated With
By-Products of Drinking Water Disinfection by Chlorine, Chlorine Dioxide, Ozone and UV-Irradiation."
Environmental Health Perspectives, Vol. 46, p 197-205. "
Zumdahl, S. (1989). Organic Chemistry. 2nd ed. D.C. Heath and Company, pp. 264, 869-870, 983.
UV Light Disinfection Technology in
Drinking Water Application—An Overview 1-27 Final—September 1996
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CHAPTER 2. ASSESSMENT OF ULTRAVIOLET LIGHT EFFICACY,
VIABILITY, AND OPERATIONAL FACTORS
This chapter presents-reported doses and corresponding inactivation rates achieved for various
microorganisms. It briefly describes methods for ultraviolet light intensity and dose measurements. Also,
it presentsJnformation provided by the ultraviolet light industry and AWWA on inactivation rates and
dose requirements next to the inactivation rates and dose requirements reported in the scientific literature.
This juxtaposition is intended to show points of agreement and disagreement between manufacturers'
information and peer-reviewed research data. -
The inactivation rates reported in this chapter and corresponding dose requirements, may be used as a guide
for ultraviolet light application in ground drinking water disinfection. However, it is important to consider
the conditions under which these inactivation rates were achieved. These conditions include laboratory
conditions, water quality or media used, microorganism type and source, method used to estimate
.ultraviolet light intensity and dose, and reliability of the method used to count the microbial population
that survived the ultraviolet treatment. Additionally, it is important to consider the ambient conditions
where the ultraviolet light treatment will"be used before deciding on a specific dose for disinfection.
This chapter discusses equipment operational factors,,water quality, and hydraulic design considerations.
General and specific small systems design considerations are suggested. Moreover, ultraviolet light
operational case histories are presented to provide information on the practical aspects of, various
ultraviolet light disinfection field applications. Other considerations related to the use of ultraviolet light,
such as by-products formation and the phenomena of reactivation, are presented. Finally, the issue of
finding a suitable challenge surrogate microorganism is discussed, as well as attempted comparisons of
ultraviolet light disinfection efficiency to chemical disinfectants.
This chapter is organized as follows: Section 2.1 is an introduction to drinking-water disinfection by
means of ultraviolet light. It briefly explains how doses and intensities are estimated. Section 2.2 presents
inactivation rates of various microorganisms by means of ultraviolet light in water and wastewater. It
presents microorganism reduction rates attained through the use of ultraviolet light as provided by the
ultraviolet light industry and AWWA (section 2.2.1) and inaetivation rates reported in the scientific
literature (section 2.2.2 and section 2.2.3). Section 2.2.4 provides a brief overview of the inactivation rates
achieved in applying ultraviolet light in wastewater effluent treatment, combined sewer overflow treatment,
UV Light Disinfection Technology in
Drinking Water Application—An Overview 2-1 Final—September 1996
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Chapter 2—Assessment of Ultraviolet Light Efficacy, Viability, and Operational Factors
and recycled water treatment. This section (2.2.4) describes what ultraviolet light disinfection technology
can achieve in microorganism inactivation under worst-case conditions, such as floods, failure of a well
casing, an undetected cesspool failure, or a ground water system coming under the direct influence of
surface water. Section 2.3 gives an insight to the operational factors that govern the application of
ultraviolet light technology in drinking water (section 2.3.1 through section 2.3.4). Section 2.4 discusses
issues related to the use of ultraviolet light in drinking water applications, such as by-products formation
and organics removal (section 2.4.1); the phenomena of photoreactivation, dark reactivation, and chemical
reactivation (section 2.4.2); the issue of disinfectant residual (section 2.4.3), and the availability of a
monitoring and challenge surrogate microorganism (section 2.4.4). Section 2.4.5 discusses the attempts
to compare ultraviolet light disinfection efficacy to chemical disinfection efficacy. Section 2.5 presents
a summary of findings.
2.1 INTRODUCTION TO INTENSITIES AND DOSES
The inactivation of microorganisms in drinking water by means of ultraviolet light is a function of the
intensity of radiation at the proper wavelength, the exposure time, the water quality, and the thickness of
targeted water. The intensity is measured in milliwatts per square centimeter (mWs/cm2). The time is the
theoretical exposure time calculated or measured as the hydraulic detention time in seconds in the
ultraviolet chamber." The proper wavelength is a range (200 nm to 300 nm) with a maximum biocidal
effectiveness at 250 nm to 265 nm. The thickness of the targeted water is the perpendicular distance from
the light source to the wall of the chamber.
Similar to the hydraulic consideration needed in chemical disinfection processes, a primary consideration
in the application of ultraviolet light for disinfection is to ensure that sufficient energy is delivered to the
entire volume of water to be disinfected. The concept of dose in ultraviolet light disinfection is
comparable to the dose concept in chemical disinfection. In chemical disinfection, dose "Ct" is the
product of "C" the concentration of the chemical disinfectant in mg/L and contact time "t" in minutes.
Under the Surface Water Treatment Rule (SWTR), "t" is defined as the contact time measured from the
point of disinfectant application to the point of residual measurement or between points of residual
measurements (USEPA, 1991). Because there is no ultraviolet light residual measurement beyond the light
emitting lamp, contact time in an ultraviolet light application is the hydraulic detention time. Exhibit 2-1
is intended to provide a brief description of the methods used to estimate ultraviolet light intensity and
dose measurements.
UV Light Disinfection Technology in
Drinking Water Application—An Overview 2-2 Final—September 1996
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Chapter 2-Assessmgnt of Ultraviolet Light Efficacy, Viability, and Operational Factors
Exhibit 2-1. Dose and Intensity Measurements
Dose is intensity multiplied by time. It is usually represented in milliwatts second per square centimeter units
(mWs/cm). Time ,s calculated as the hydraulic residence time of the water.in the ultraviolet light reactor
Determining intensity of ultraviolet light at any point in an ultraviolet light reactor is not as simple as measurin*
tone. The intensity of ultraviolet light at 253.7 nm is a function of the light source, the physical arrangement of
the lamps, and energy absorbing elements in the water that will absorb the light or attenuate it-before it reaches
the microorganism to be disinfected or the point of intensity measurement.
Diodes1 employed to measure ultraviolet light; intensity at the farthest point from the light source provide
continuous monitoring of the ultraviolet reactor. However, these sensors are planar receptors; therefore only light
.that stakes the surface of the receptor orthogonally /at a right angle) will be fully measured. Moreover the
ultraviolet light-emitting lamp emits light at wavelengths that are visible or does not have germicidal effect
Diodes might be sensitive to these non-ultraviolet rays. For drinking water disinfection and in a multi-lamp
ultraviolet light reactor, measuring light intensity, becomes more complex because light flux and target
microorganisms are all three-dimensional. °
Currently there are three methods to estimate ultraviolet light intensity. According to these estimates, ultraviolet
light disinfection reactors are designed, tested, and calibrated. These methods are biological assays, chemical
actinometer, and calculation. ' , .
In the biological assays method, collimated ultraviolet light (light directed in a straight line) intensity is measured
by a radiometer (USEPA, 1986). Challenge bacteria is then exposed to the measured intensity for equal intervals
of time, thus yielding specific doses. The surviving bacterial population is plotted against the dose,-and a dose-
response relationship is established (Johnson and Quails, 1984, Quails and Johnson, 1982). This biolo-ical assay
method offers an independent verification of the ultraviolet system, thus serving as a design tool and as a post-
construction performance test. However, this method can be costly, time consuming and cumbersome. Moreover
there is no consensus among scientists about which challenge microorganism to use to make this method more
standardized. - ., ,
Actinometry is the measurement of radiation intensity by the speed of a photochemical reaction. In practical terms
related to drinking water, chemical actinometry is. the measurement of the disinfecting pdwer of ultraviolet li
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Chapter 2—Assessment of Ultraviolet Light Efficacy, Viability, and Operational Factors
The information collected on inactivation rates from the industry and the .scientific literature provide
important information on targeted microorganisms and applied doses. However, data on factors that can
affect disinfection rate and effectiveness of ultraviolet light application are seldom mentioned in the
published literature. Very little data are available on light intensity and method of measurement,
ultraviolet light transmission, efficiency, water or medium absorbance coefficient. Also, very little data
are available on the effects of time, temperature, pH, total dissolved solids, high ultraviolet light absorbing
inorganic compounds such as iron and manganese, total organic carbon or assimilable organic carbon,
color, and turbidity on disinfection efficacy. ,
2.2 JNACTIVATION RATES (EFFICACY)
This section presents microorganism reduction rates attained through the use of ultraviolet light as
provided by the ultraviolet light industry and AWWA. Also provided is 99.9%). ,
UV Light Disinfection Technology in
Drinking Water Application—An Overview 2-4 Final—September 1996
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Chapter 2-Assessment of Ultraviolet Light Efficacy, Viability, and Operational Factors
Exhibit 2-2. Doses Required for "Complete Destruction" (>99.9%) of Microorganisms*
(Atlantic Ultraviolet Corporation, 1995) "
Organism
Streptococcus
Dysentery bacilli
Influenza
Staphylococcus
=ecal Coliform
Salmonella
Legionella pneumophila
Bacteriophage (£, coli)
Dose mWs/cm2
3.8
6.6
6.6
6.6
10.0
12.3
6.6
C?rP°rftion "?as Defined its "complete destruction" term to mean greater than
^m based Upon research conducted by Rudolf Nagy, Westinghou
s Corp in the
Capital Controls Company, Inc., provided information on inactivation rates for various microorganisms
with names of authors who reported the rates (Capital, 1995). Infilco Degerembnt, Inc. (IDI, 1995)
provided inactivation rates for some general microorganisms and one specific microorganism (Escherichia
coli). The ultraviolet light doses specified by Infilco Degeremont, Inc., to achieve 2 log reduction for
various general microorganisms are,difficult to verify. The dose reported by Infilco Degeremont, Inc., to
be sufficient to achieve 2 log reduction in Escherichia coli (6.6 mWs/cm2) is the same dose reported by
Atlantic Ultraviolet Corporation and Aquafine Corporation, to be sufficient to achieve a minimum of 3
log reduction in the same microorganism.
Both Capital Controls Company, Inc. and Infilco Degeremont, Inc. claimed to contact out bioassay studies
to independent laboratories, however, both companies did not provide detailed information or data from
the studies conducted.
The motivation rates provided by the industry are difficult to verify at this point. In addition, industry-
provided information on inactivation rates did not include information on the type of medium in which
the organisms were targeted, the source of the organisms, and other parameters, such as turbidity. The
inactivation dose ranges provided by the five companies are summarized in Exhibit 2-4.
The ultraviolet light dose requirements provided by the ultraviolet light industry (>99.9% inactivation for
some microorganisms) are lower than the doses reported in the scientific literature for water disinfection.
For example, two industry sources claimed that 22 mWs/cm2 is sufficient for >99,9% inactivation of B.
Subtilis;the research by Chang et al., 1985, shows 3 log reduction at an ultraviolet dose of 60 mWs/cm2.
UV Light Disinfection Technology in
Drinking Water Application—An Overview
2-5
Final—September 1996
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Chapter 2—Assessment of Ultraviolet Light Efficacy, Viability, and Operational Factors
Exhibit 2-3. Dose Required at 253.7 Nanometers to Inhibit Colony Formation in
90 Percent of the Organisms arid for Complete Destruction (>99.9%)
(Atlantic Ultraviolet Corporation, 1995)
Organism
Bacillus anthraces
B. Megaterium spp. (veg.)
B. Megaterium spp. (spores)
B. paratyphosus
B. subtilis
B. subtilis spores
Corynebacterium diphtheria
Dysentery bacilli
Eberthella typos
Escherichia coli
Micrococcus candidus
Micrococcus sphaeroides
Neisseria catarrhalis
Phytomonas tumafaciens
Proteus vulgaris
Pseudomonas aeruginosa
Pseudotnonas fluorescens
S. enteritldis
S. typhimurium
Sarcina lutea
Serratia marcescens
Shigella paradysenteriae
Spirillum rubrum
Staphylococcus albus
Staphylococcus aureus
Streptococcus hemolyticus
Streptococcus lactis
Streptococcus viridans
(mWs/cm2)
90%
4.52
1.3
2.73
3.2
5.8
11.6
3.37
2.2
2.14
3.0
6.05
10.0
4.4
4.4
3.0
5.5
3.5 '
4.0
8.0
19.7
2.42
1.68
4.4
1.84
2.6
'2.16
6.15
2.0
>99.9%
8.7
2.5
5.2
6.1
11.0
22.0
6.5
4.2
4.1
6.6
12.3
15.4
8.5
8.5
.6.6
10.5
6.6
7.6
15.2
26.4
' 6.16
3.4
6.16
5.72
6.6
.5.5
8.8
3.8
Yeast
Saccharomyces ellipsoideus
Saccharomyces spp.
Saccharomyces cerevisiae
Brewer's yeast
Baker's yeast
Common yeast cake
6.0
8.0
6.0
3.3
3.9
6.0
13.2
17.6
13.2
6.6
8.8
13.2
Mold Spores (Color)
Penhlllium rogueforti (Green)
Penlcillium expansum (Olive)
Penicilllum dig'rtatum (Olive)
Aspergillus glaucus (Bluish green)
Aspergillus flaws (Yellowish green)
Aspergillus niger (Black)
Rhlsopus nigricans (Black)
Mucor racemosus A (White gray)
Mucor racemosus B (White gray)
Oospora lactis (White)
13.0
13.0
44.0
44.0
60.0
132.0
110.0
17.0
17.0
5.0
26.4
22.0
88.0
88.0
99.0
, 330.0
220.0
35.2
35.2
11.0
UV Light Disinfection Technology in
Drinking Water Application—An Overview
2-6
Final—September 1996
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Chapter 2-Assessment of Ultraviolet Light Efficacy, Viability, and Operational Factors
Exhibit 2-4. Summary of Ultraviolet Light Microorganisms
Inactivation Dose Requirements in mWs/cm2
Source
Aquafine :
Atlantic Ultraviolet
Corporation
Capital Controls
Company
Infilco Degeremont,
Inc.
Trojan
Bacteria
2.5-26.4
2.5-26.4
1.3 - 19.7
1 - 54.5**
2.9 - 15.2
. 1 - 54.5**
Virus
' 6.6 - 440*
' " . -" .•• ' '
-. 2.6 - 240***
6.6-8
3.6-11.3
Protozoa
200
-r
60 - 200
- • • '
60 - 200
Inactivation
>3 log
>3 log
1 log
1 log
2 log
1 log
s; the second highest dose reported by Aquafine was 8 mWs/cm2.
„.„.,-. ... , 2 ,---_.-. _. -r~-~s; the second highest dose reported for a bacteria was 20.5 mWs/om2
240 m Ws/cm was reported for tobacco mosaic virus; the second highest dose reported for a virus was 3.6 mWs/cm2.'
The inactivation rates provided by the industry appear to be adopted from European literature. A list of
energies required to achieve 90 and 100 percent reduction in microorganism by means of ultraviolet light
at 253.7 nm wavelength published in Developments in Food Microbiology Vol. 3 (Snowball and Homsey,
1988) shows dose requirements identical for the most part to those provided by the ultraviolet industry
for drinking water disinfection. However, the list provided by Snowball and Homsey, 1988, clearly states
that all dose, requirements data were collected under laboratory conditions and in a static air medium
(emphasis added) and that the relevance of such data when applied to the same listed microorganisms in
water must be suspect (Snowball and Hornsey, 1988). " '
In its comment to .the USEPA on the 1991 draft Qround Water Disinfection Rule (GWDR), the American-
Water Works Association (AWWA) referred to studies conducted at the University of New Hampshire
involving inactivation rates,of surrogate microorganisms for drinking water disinfection using ultraviolet
light. AWWA, 1992, provided preliminary results for the inactivation of bacteriophage MS-2. According
to AWWA, a 4 log reduction of MS-2 was achieved at a 150 mWs/cm2 dose at 10°C and pH 7.0. At pH
of 5.5 and at 10°C, a dose of 152 mWs/cm2 was required to achieve a 4 log reduction. These preliminary
results suggest that ultraviolet light treatment is pH independent in that range. Malley, Shaw and Ropp,
1996 (as cited in Snicer et al.f 1996) examined MS-2 inactivation under different temperature and pH
levels in ground waters containing less than 0.15 ppm iron. The test results showed that temperature had
little effect on MS-2 inactivation, but a significant difference in inactivation was detected between the tests
at pH levels of 7.0 and 8.5 and that of tests at a pH level of 5.5. The researchers attributed the detected
difference to morphological changes nit he nature of the protein coat that caused clumping of
UV Light Disinfection Technology in
Drinking Water Application—An Overview
2-7
Final—September 1996
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Chapter 2—Assessment of Ultraviolet Light Efficacy, Viability, and Operational Factors
microorganisms. Other technical references (Montgomery, 1985 and USEPA, 1986) conclude that
ultraviolet light treatment is pH insensitive. The doses reported in the preliminary results of bacteriophage
MS-2 4 log inactivation as reported by AWWA, 1992, are about twice the doses reported by Wilson et
al., 1993, and Weidenmann et al., 1993, for 4 log inactivation of the same microorganisms.
2.2.2 Inactivation Rates in Drinking Water Treatment as Compiled from the Scientific
Literature
Based on the literature search, Lea (1947) provided mean lethal dose values for Escherichia coli at
different ultraviolet intensities. Using an ultraviolet light at 253.6 nm of wavelength, he reported the
results presented in Exhibit 2-5.
Exhibit 2-5. Light Intensities and Mean Lethal Doses for E. Coli (Lea, 1947)
Intensity ergs/cmVsec
1.2x102(0.012mW/cm2)
3.1 x 103 (0.31 mW/cm2)
•6.4x10*(6.4mW/crn2)
Mean Lethal Dose ergs/cm2
• 7.5 x103 (0.75 mWs/cm2)
8.5 x103 (0.85 mWs/cm2)
8.5 x 103 (0.85 mWs/cm2)
- Mean lethal dose here is defined as the dose required for the reduction of £. coli to 37%
(l.e., .43 log reduction) . . " '
— 1 erg = 1O'7 joules
- 1 joule = 1 watt second
— mWs/cm2 s milliwatts second per square centimeter = 104 ergs/cm2
Lea (1947) concluded that bacterial disinfection using ultraviolet light is a first-order reaction. This
conclusion was based on data compiled by Lea using ultraviolet light of 280.3 nm wavelength on Bacillus
megaterium (see Exhibit 2-6). Lea (1947) also concluded that the mean lethal dose is independent of
intensity (as reported in Lamanna and Mallette, 1965). The measurements of the intensity of ultraviolet
light and the efficiency of light transmission at the reported wavelengths were not reported.
Therefore, the reliability of these low doses compared with current experience is questionable. Also, the
determination that this is a first-order reaction was based on data with less than 1 log reduction of the
targeted bacteria.
Groocock (1984) of the Derwent Division of the Severn-Trent Authority in the United Kingdom reported
ultraviolet light doses required to achieve one log reduction (90 percent inactivation) for several
microorganisms. The reported doses are presented in Exhibit 2-7. Groocock (1984) did not report
specific information on the types of protozoa reduced, methods used to estimate doses, test setting,' or
UV Light Disinfection Technology in
Drinking Water Application—An Overview 2-8 Final—September 1996
-------
Chapter 2-Assessment of Ultraviolet Light Efficacy, Viability, and Operational Factors
Exhibit 2-6. Survival Curve of Bacillus Megaterium Irradiated
Using Ultraviolet Light at 280.3 nm (Lea, 1947)
Dose (mWs/cm2)
022E-11
Exhibit 2-7. Ultraviolet Light 254 nm Dose (mWs/cm2) Required for a 90 Percent
Killing of Various Microorganisms (Groocock, 1984)
Microorganism
Serratia marlescens
Pseudomonas aeruginosa
Mycobacterium tuberculosis
Salmonella enteritidis
Salmonella paratyphi
Salmonella typhi (1)
Salmonella typhimurium
ShigeUa dysenteriae (2)
Shigella paradysenteriae
Escherichia coli
Proteus vulgaris
Bacillus anthracis .
Bacillus megaterium (cells)
Bacillus megaterium (spores)
Bacillus suMfe (cells and spores)
Dose
2.42
5.50
6.00
4.00
3.20
2.14
8.00
2.20
1.68
3.00
2.70
4.52'
3.75
9.07
7.10
• Microorganism
Bacillus subtilis (spores)
Clostridium tetani
Staphylococcus aureus
Streptococcus viridans
Streptococcus pyogenes
Micrococcus candidus
Micrococcus sphaeroides
Sarcina lutea (M. luteus)
Micrococcus lysodeikticus (M. luteus) ATCC 12698
Mictococcus radiodurans (Phosphate buffer)
Yeast (average)
Protozoa
Algae, blue-green
Aspergillus niger (bread)
Dose
12.00
4.90
2.18
2.00
' 2.16
6.05
10.00
19.70
23.00
20.50
4.00
60-100
300-600
100
UV Light Disinfection Technology in
Drinking Water Application—An Overview
2-9
Final—September 1996
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Chapter 2—Assessment of Ultraviolet Light Efficacy, Viability, and Operational Factors
water quality parameters under which the reduction occurred. However, Groo.cock's paper has often been
used as a reference in the scientific literature and is often used as a testament to the efficacy of ultraviolet
light Many of the dose figures provided in Groocock (1984) are the same figures provided in the
literature published by the ultraviolet light industry.
Meulemans, 1987, as cited in Ellis, 1991, shows a 1 log reduction in bacteria at a dose range of 2.1
mWs/cm2 to 12 mWs/cm2 and a 1 log reduction in protozoa at a range of 64 to 100 mWs/cm2. Whitby,
1989, reported more than a 4 log reduction in fecal coliform at an estimated dose of 33 mWs/cm2.
The guidance manual for compliance with the filtration and disinfection requirements for public water
systems using surface water sources (USEPA, 1991) listed a 2 log reduction in Hepatitis A virus (HAV)
at a dose of 21 mWs/cm2 and a 3 log reduction of-HAV at a dose of 36 mWs/cm2. The dose values were
derived by applying a safety factor of 3 to the HAV inactivation data that were reported by Sobsey (1988).
The HAV has been established as an important cause of waterborne disease (USEPA 1991).
Wiederanann et al., 1993, achieved an inactivation rate of 4 logs for MS-2 in a 0.9 percent NaCl solution
with an ultraviolet dose of approximately 74 mWs/cm2 (intensity 0.184 mW/cm2, tune 400 seconds) and
a 4 log reduction in HAV with an ultraviolet dose of approximately 18.5 mWs/cm2 (intensity 0.184 ,
* - ** '
mW/cm2, time 100 seconds). The Wiedenmann et al. (1993) test results suggest that MS-2 is four times
more resistant to ultraviolet light than HAV. The incomparability of Spbsey's (1988) results with the
Wiedenmann et al. (1993) figures can be attributed to the source of microorganisms, medium difference,
and ultraviolet intensity estimates. The same reasons can be given when comparing the Battigelli, Sobsey,
and Lobe, 1993, 4 log reduction of HAV achieved with 16 mWs/cm2 of ultraviolet light dose to the
reductions mentioned previously.
In their recent research, Battigelli, Sobsey, and Lobe (1993) confirmed in a lab setting what other
researchers have found. The researchers' ultraviolet light disinfection test results showed that MS-2
bacteriophage is more resistant to ultraviolet light than rotavirus strain SA 11, coxsackie .virus type B 5,
HAV virus strain HM-175, and bacteriophage <3>X174. The 4 log reduction doses for HAV strain HM-175
and bacteriophage
-------
Chapter 2—Assessment of Ultraviolet Light Effipacy, Viability, and Operational Factors
Sobsey (1989) summarized data on inactivation of pathogens in water and wastewater by ultraviolet light.
He noticed that vegetative bacteria (i.e., bacteria that propagate by nonsexual processes, such as coliforms)
are inactivated (>3 log reduction) at doses below the DHEW-recommended minimum level of 16
mWs/cm2 and that higher doses are required to achieve 3 log reductions in viruses, bacterial spores, and
protozoan cysts. Data show that all bacteria and viruses (including Simian rotavirus SA-11), with the
exception of Reovirus 1, suffered 3 log reduction at doses below the ANSI/NSF-recommended level of
38 mWs/cm2, regardless of the liquid medium except for sewage medium. Data compiled by Sobsey
(1989) are presented in Exhibit 2-8.
As, can be seen from Exhibit 2-8, bacterial sensitivity to ultraviolet light .varies from one species to
another. Even the same species exhibit nonuniform sensitivity. This variation is a function of medium
quality, source of microorganism, age of the microorganisms, microorganism population, and possible
measurement errors or inconsistent methods in measuring the applied average ultraviolet light dose. The
, range of ultraviolet light doses to disinfect bacteria (3 to 4 ^reduction) in media other than sewage is
0.14 for Escherichia coli to 60 mWs/cm2 for B. subtilis spores.
The, range of sensitivity within tested viruses as reported in Exhibit 2-8 is 21 to 45 mWs/cm2 at 3 log
reduction. Also, the data presented above show that ultraviolet light is effective against protozoa at high
doses. The 3 log removal of a protozoa (Acanthamoeba Castellanii) reported in Exhibit 2-8 at a dose
of 100 mWs/cm2 and that of a 1 log removal of another protozoa (paramecium) at the same dose as
reported by Meulemans, 1987, show that inactivation rates for some groups of microorganisms vary
considerably.
Sobotka (1993) concluded that a bactericidal dose of 25 mWs/cm2 is sufficient for most pathogenic
organisms; however, Sobotka (1993) did not provide any specific evidence or cites for his conclusion.
Sommer and Cabaj (1993), using three different cultural techniques of Bacillus subtilis spores, concluded
that one of the three methods gave consistent inactivation rates between a dose of 200 j/m2 to 900 j/m2
(20 mWs/cm2 to 90 mWs/cm2) with 5.5 log reduction at 90 mWs/cm2 and 6 log reduction at 120
mWs/cm2. In their experiment, Bacillus subtilis spores were suspended in potable water and irradiated
in a commercially available drinking water ultraviolet disinfection unit. The results of inactivation of
Bacillus subtilis spores depending on cultural methods are presented in Exhibit 2-9. Sommer and Cabaj
(1993) recommended the use of cultural method C because it yielded Bacillus subtilis spores that were
UV Light Disinfection Technology in
Drinking Water Application—An Overview 2-11 Final—September 1990
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Chapter 2—Assessment of Ultraviolet Light Efficacy, Viability, and Operational Factors
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t/V L/gftf Disinfection Technology in
Drinking Water Application—An Overview
2-12
Final—September 1996
-------
Chapter 2—Assessment of Ultraviolet Light Efficacy, Viability, and Operational Factors
Exhibit 2-9. Inactivation of B. subtilis Spores Depending on Laboratory Cultural
-• ; ~ Methods (Sommer and Cabaj, 1993)
0
-1
-2
-3
-4
-5
-6
-7
Reduction [log]
• MethodA
+ Method B
* Method C
0
20 40 60 80
Dose (mWs/cm2)
100
120
022E-12
Bacillus subtilis (ATCC 6633) spores were cultured with three different methods.
Method A: Bacteria were inoculated on Cplumbia agar plates (Oxoid) with 2% CaCL, incubated
at 37°C for 7 days, harvested, and suspended in sterile aqua dest.
Method B: Bacteria were inoculated on Schaeffer sporulation agar plates (Munaka and Rupert
1972), incubated at 37°C for 6 days, harvested, and suspended in sterile aqua dest.
Method C: Schaeffer medium was modified as a liquid enrichment bouillon 'Bacteria were
inoculated, incubated at 37°C for 3 days, harvested by centrifugation (4,000 g, 15 min 10°C) and
suspended in sterile aqua dest. -
UV Light Disinfection Technology in
Drinking Water Application—An Overview
2-13
Final—September 1996
-------
Chapter 2—Assessment of Ultraviolet Light Efficacy, Viability, and Operational Factors
more resistant to ultraviolet light treatment and showed a linear relationship between dose and log
reduction over a wider dose range than Methods A and B.' Sommer and Cabaj's study is discussed further
under section 2.4.4.
Wilson et al. 1993 tested the sensitivity of pathogenic water borne microorganisms to ultraviolet light.
The researches conducted experiments on nine different water borne bacteria (Klebsiella Terrigena, vibrio
cholerae, Salmonella typhi, Escherichia coli 0157:H7, Shigella dysenteriae, Yersinia enterocolitica,
Campylobacter jejuni, Aeromonas hydrophila, and Legionella pneumophild) and three different water
borne viruses (rotavirus SA-11, pqliovirus type 1 and hepatitis A virus) in addition to coliphage MS-2.
The researches used collimated ultraviolet light test apparatus, laboratory-cultured microorganisms and
phosphate-buffered distilled water. The individual microorganisms suspension was placed in a petri dish
and exposed to collimated ultraviolet light beam. The test results of Wilson et al. 1993 are presented in
Exhibit 2-10 and Exhibit 2-11. Exhibit 2-10 shows that under similar conditions, all tested pathogenic
bacteria will suffer a minimum of 5 log reduction at an ultraviolet dose of approximately 16 mWs/cm2.
Exhibit 2-11 shows that under similar conditions, all tested pathogenic viruses will suffer a minimum of
6 log reduction at a dose of about -60 mWs/cm2. It is important to note that naturally occurring
microorganisms are typically more resistant to disinfection than laboratory-cultured microorganisms. In
addition the phosphate-buffered distilled water may have lower ultraviolet demand than fresh water.
Wilson et al. 1993 using the coliphage MS-2 inactivation data conducted a linear regression analysis to •
estimate ultraviolet dose with 95 percent confidence intervals.
Wilson et al. 1993 reported ultraviolet dose predictions are presented in Exhibit 2-12.
Considering the lower end of the 95 percent confidence interval and based on Wilson et al. 1993 work .
(see exhibits 2-10 and 2-11), an ultraviolet light dose of 60 mWs/cm2 will result in more than 4 log
reduction for the viruses tested and more than 6 log reduction in all the tested pathogenic bacteria.
The results and statistical inferences of Wilson et al., 1993 are supported by a more recent research.
sponsored by the American Water Works Association Research "Foundation (AWWARF). In their
AWWARF- supported research, Snicer et ai., 1996, concluded that 4-log inactivation of MS-2 can be
achieved by an ultraviolet light dose of 64 mWs/cm2 to 93 mWs/cm2. Snicer et. al., 1996 also concluded
that 4 log inactivation of rotavirus, poliovirus and Hepatitis A virus can be achieved by an ultraviolet light
UV Light Disinfection Technology in
Drinking Water Application—An Overview 2-14 Final—September 1996
-------
Chapter 2-Assessment of Ultraviolet Light Efficacy, Viability, and Operational Factors
Exhibit 2-10. Survival Curves of Ultraviolet Irradiated'Bacteria
o
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1 .*
-6
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-8-
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\\
D Klebsiellaterrigena
•*• Aeromonas hydrophila
A Yersinia enterocolitica
0 4 8 12 16 2
^\ : • '• " ' .
^I'^fxg 9 \
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n Salmonella typhi
+ Campylobacterjejuni
A Vibrio cholerae
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4 8 12 16 20
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UV Dose (rriW sec/cm2)
l.^J' te j*s ^ere done in phosphate-buffered distilled water usinq laboratory
cultured microorganisms. **w*r+M+*g t f ^\*lMl t\JM\J^y Hi
Drinking Water Application—An Overview 2-15
Final—September 1996
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Chapter 2—Assessment of Ultraviolet Light Efficacy, Viability, and Operational Factors
Exhibit 2-11. Survival Curves of Ultraviolet Irradiated Viruses and Test Surrogate
Coliphage MS-2 (Wilson et al., 1993)
1 ' • N
0.
"o"
Z -1-
~3>
2.9 .
•£.
H5 -3.
U) .4 .
£ WJ
> -5-
^3 .R .
CO
rn .7 .
§1
-9 •
^5Ov +>sti
BV^^ ^VL M^^^ '
NR>J"K^
"\\\. %^
\V\, ^
"= \& N. u ^vn
^\ K ^^
V \ D ^- B
\ \ ^^
\ \
1 1 IX 1^1 1 • 1
0 20 40 60 80 100 120 140
UV Dose (mW sec/cm2)
* All tests were done in phosphate-buffered distilled water using laboratory
cultured micro-organisms. '
. _.
n Coliphage MS-2
+ Rotavirus SA-11
A Poliovirus type 1
• Hepatitis A
Exhibit 2-12. Ultraviolet Estimation From Linear Regression Model of Coliphage MS-2
(Wilson et al., 1993)
Ultraviolet Dose mWs/cm2
38
46.5
60
120
Relative Standard Deviation
. 21%
17.3%
13.4%
6.74%
95% Confidence interval mWs/cm2
29.9-46.1
38.5-54.6
51.9-68.1
112-128
'one tailed t test. .
dose of 50 mWs/cm2, 23 mWs/cm2 to 29 mWs/cm2, and 6 mWs/cm2 to 15 mWs/cm2 respectively. Snicer
et al., 1996, conducted pilot scale and bench scale studies and pipe loop studies on waters from different
groundwater sources. The two pilot plants constructed for the experiments operated for one full year. One
pilot plant simulated intermittent water use while the other operated continuously. The bench scale
• laboratory studies were designed to compare MS-2 sensitivity to ultraviolet light to that of poliovirus,
rotavirus and Hepatitis A virus (HAV). The bench scale laboratory studies also were designed to compare
UV Light Disinfection Technology in
Drinking Water Application—An Overview
2-16
Final—September 1996
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Chapter 2-Assessment of Ultraviolet Light Efficacy, Viability, and Operational Factors
the effects of varying groundwater quality on ultraviolet light dose requirements to achieve a 4-log
reduction in the tested microorganisms.
The pilot scale studies demonstrated mat 4-log reduction in MS^2 can be achieved through ultraviolet light
disinfection. An ultraviolet light dose of 87.4 mWs/cm2 was sufficient to achieve 4 log reduction in ground
water containing up to 0.65 ppm iron (the USEPA has set the secondary MCL of iron at 0.3 ppm). It was
also found that performance and maintenance is a function of water quality especially when water
chemistry lends itself to deposition or scaling. In addition, pilot studies found that electronic ultraviolet
light sensors should be calibrated at the time of installation to guarantee reliable, and accurate results.
Pipe loop studies showed that the use of Assimilable Organic Carbon (AOC) as an indicator was not
sensitive enough to detect differences in regrowth potential in low TOC groundwaters, and that ultraviolet
light did not significantly increase or decrease regrowth. Snicer et al., (1996), did not infer any detailed
conclusions from the loop study because of the cursory nature of the study. Laboratory studies
demonstrated that groundwater quality is directly related to required ultraviolet light dose for viral
inactivation. Ultraviolet light doses ranging from 64 to 93 mWs/cm* are required for 4-log inactivation
of MS-2 bacteriophage in the groundwaters studied.
Ultraviolet light disinfection systems operating cost estimates ranged between $0.059 and $0.106 per
thousand gallons assuming an ultraviolet light dose of 60 mWs/cm2 and a power cost of $0.15/kWhr and
excluding maintenance and lamp replacement costs (Snicer, et al., 1996).
Karanis et al. (1992) examined the sensitivity of different protozoan parasites and bacteria to ultraviolet •
light. Karanis et al. (1992) research shows that ultraviolet light can kill protozoan parasites, cysts, and
trophozbites, but these organisms require a higher dose than that needed to kin the less complex and
smaller bacteria. The results of Karanis et al. (1992) experiments are presented in Exhibit 2-13. As can
be'seen from Exhibit 2-13, commercially available ultraviolet light systems are effective against
Escherichia coli bacteria, with 3 log reduction at 152 mWs/cm2, but less effective against bacterial spores
with 3 log reduction of B. subtilis spores at 50,mWs/cm2.
Abbaszadegan et al. (1993) conducted experiments on POU systems that combined a carbon block filter
with an ultraviolet light system. The carbon block filter was designed to remove Giardia lamblia cysts
-. and CryptQsporidium oocysts. The ultraviolet light dose, as reported in the published study, was greater
UV Light Disinfection Technology in
Drinking Water Application-An Overview 2-17 Final-September 1996
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Chapter 2—Assessment of Ultraviolet Light Efficacy, Viability, and Operational Factors
Exhibit 2-13. Comparison of Protozoan and Bacterial Sensitivity to Ultraviolet Light
(Karanis et al., 1992)
Microorganism
Reduction (log AMV0)
Dose (mWs/cm2)
Medium
Parasites
Trichomonas vaginalis
secondary
culture
secondary
culture
Acanthamoeba /ysocfes3
cysts
trophozo'rtes
Acanthamoeba quina/lugdunensi&
cysts
trophozoftes
Giardta lamblia
human cysts
gerfail cysts
N
<3
NG"
>2.3
NG
1.8
1.6
<2
2-7
2
2
402
160-240
241
80
72
60
72
72
180
180
0.9% NaCI,
water from medicinal spring
dist. H2O
tap water
dist. H2O
tap water
dist. H2O
dist. H2O
Bacteria .
Escherichia coli (ATCC 1 1229)
Salmonella typhimurium
(ATCC 13311)
Yerslnla enterocolftica
(ATCC 2371 5)
B. subtilis spores (ATCC 6051)
3
<3
3
3
15
10
10
50
buffered water
buffered water
buffered water
buffered water
^Acanthamoeba cysts and trophozoites were 7 days old.
"NG = No growth.
than 128 mWs/cm2. Abbaszadegan et al. (1993) reported approximately 4 log reduction in HAV, Giardia
lamblia, and Cryptosporidium parvum. Other inactivation rates reported in the study of Abbaszadegan
et al. (1993) are presented in Exhibit 2-14.
It must be noted that the reductions in microorganisms presented in Exhibit 2-14 are the function of the
combined carbon block filter and ultraviolet light system. The published study did not provide any details
on the reductions achieved by the carbon block alone and those achieved by ultraviolet light. However,
the study shows a consistent pattern of sensitivity to ultraviolet light, with cysts being more resistant to
inactivation by ultraviolet light than viruses and viruses being more resistant than bacteria.
UV Light Disinfection Technology in
Drinking Water Application—An Overview
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Final—September 1996
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Chapter 2—Assessment of Ultraviolet Light Efficacy, Viability, and Operational Factors
Exhibit 2-14. Average Log Reduction of Microorganisms Using Combined Carbon Block
Filter with Ultraviolet Disinfection Unit (>128 mWs/cm2) (Abbaszadegan et ah, 1993)
Microorganisms
Log Reduction
Poliovirus
4.28
Rotavirus
4.29
HAV
3.92
MS-2
Giardia lamblia cysts
3.99
Cryptosporidium parvum
4.3
Vibrio cholerae
5.96
Shigella dysenteriae
6.7
Escherichia coll
6.3
Salmonella typhi
6.52
ANSWSF Standard 55-1991 for POU Class A systems, which requires a minimum 38 mWs/cm2 dose to
disinfect clear drinking water, was based on the work of Chang (1985) and Harris (1986). Chang's work
(1985) as cited in-ANSI/NSF (1991) shows 3, to 4 log reduction in both poliovirus and rotavirus and a
projected 6 log reduction of Escherichia coli at an ultraviolet light dose of 30 mWs/cm2.
Harris' work (1986) as cited in ANSI7NSF (1991) shows a 5 log reduction of poliovirus at a dose of
40mWs/cm2. NSF concluded that a 4 log .reduction of poliovirus will be achieved at a dose of
38mWs/cm2. .
: ' . , -'A
.-='.- - ' /-
Exhibits 2-2 through 2-14 and the above discussion illustrate that inactivation rates of specific
microorganisms vary among investigators. It is hypothesized that the previously cited characteristics of
microbes tested and/or test conditions contribute to such differences. Generally speaking, however, the
data show clearly and with few exceptions that algae, fungi, protozoa, and bacterial spores are more
resistant (in that order) to ultraviolet light than bacteria and viruses. Also, gram-positive bacteria are more
resistant to ultraviolet light than, gram-negative bacteria. Generally, gram-positive bacteria have thicker
walls than gram-negative bacteria; therefore, they provide the cell's DNA with better protection from
ultraviolet light exposure (Ellis, 1991).
UV Light Disinfection Technology in
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Final—September 1996
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Chapter 2—Assessment of Ultraviolet Light Efficacy, Viability, and Operational Factors
2.2.3 Cryptosporidium parvum Oocysts and Giardia muris Cysts Inactivation Rates
Using Ultraviolet Light
Under normal conditions, ground water sources are not expected to contain Cryptosporidium species or
Giardia species. However, primary sources of ground water contamination are leaks from septic tanks,
cesspools, drainage fields, municipal sewer systems, and treatment lagoons (Wolfe, 1990). Also, in cases
of floods, natural disasters, or failure of a well casing, ground water might come under direct influence '
of Cryptosporidium- and Giardia-containing surface water.
This section and the following section are intended to provide available information about ultraviolet light
doses needed to disinfect water that deteriorated in quality and that might contain pathogenic protozoa.
Operators in such emergency situations have been known to increase ultraviolet dose by increasing the
electric potential difference (voltage) and/or by reducing the flow rate to increase the residence time as
deemed necessary.
In 1985, the USEPA (Carlson et al., 1985) funded a project to study the use of ultraviolet light to disinfect
drinking water for small water supply systems. Giardia muris cysts, Yerisinia enterocolitica, and
EscJierichia coli were spiked into an ultraviolet light treatment unit influent. The researchers found that
Giardia nutris cysts .are more resistant "to ultraviolet light than Yerisinia enterocolitica and Escherichia
coli. The researchers also'found that the presence of relatively small inorganic or organic particulates (5
pm diameter or less) had no discernible effect on the ultraviolet light disinfection of cysts. In contrast,
turbidity in the form of particulates (> 5 um) may provide shielding and protection to the organisms
present in the treated water. To achieve less than 1 percent survival rate of Giardia muris cysts, a
minimum ultraviolet light dose of above 121 mWs/cm2 is needed (reported intensity 0.0914 mW/cm2,
exposure time 22 minutes). Exhibit 2-15 is a graphical presentation of Giardia muris cyst survival rates
as reported by Carlson et al. (1985).
Karanis et al. (1992) examined the disinfection capabilities of ultraviolet light against protozoan parasites.
The researchers used Giardia lamblia cysts extracted from both animals and humans. Both groups of
cysts suffered a 2 log reduction when irradiated by ultraviolet light at 180 mWs/cm2 dose (see Exhibits
2-13 and 2-16). Karanis et al. (1992) also used lab-cultured protozoa and protozoa in dormant and
vegetative states from human and animal sources along with different types of bacteria to test then-
sensitivity to ultraviolet light (most of the experiments were conducted using distilled or buffered water).
UV Light Disinfection Technology in
Drinking Water Application—An Overview 2-20 Final—September 1'996
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Chapter 2-Assessment of Ultraviolet Light Efficacy, Viability, and Operational Factors
Exhibit 2-15. Giardia muris Cyst Survival Percent Versus Ultraviolet Light Exposure
: (Carlson, 1985)
Ptin Ray UV Bench-Scale Study
1-Liter. 4-inch Diameter Vessel
2nd Fttm (9/27/83)
3rd Run (10/4/831
m this experiment was 0.0914 mW/cm<
35
20 25 30
Exposure Time, min
82.3 109.7 137.1 754.5 791.9
UV Dosegc. i
Exhibit 2-16 clearly shows that the source of parasites is important in determining dose requirements and
'tfaatlhe growth stage of the microorganism is another important factor. As can be seen from Exhibit 2-16,
Aconthamoeba rhysodes trophozoites are more sensitive to ultraviolet light than Acanthamoeba cysts at
a dose of about 38 mWs/cm2 but more resistant to inactivation at a dose above 40 mWs/cm2.
Campbell et al. (1995) used a low-pressure ultraviolet light system of a theoretical minimum intensity of
14.58 mWs/cm2 at the germicidal wavelength of 253.7 nm for 10 minutes (ultraviolet dose 8,748
mWs/cm2) for the purpose of inactivating Cryptosporidium parvum opcysts. The preliminary results from
Campbell et al. (1995) show a potential for inactivating Cryptosporidium parvum oocysts in clean water,
using an ultraviolet light disinfection system. CampbeU et al. (1995) indicated that the 2 to 3 log
reduction in the viability of oocysts of Cryptosporidium parvum is a conservative estimate of the .actual
inactivation because the viable oocysts count is restricted by the limitations of the standard enumeration
technique developed by Campbell et al. (1992) (vital dye assays that rely on morphology and inclusion/
UV Light Disinfection Technology in
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Final—September 1996
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Chapter 2—Assessment of Ultraviolet Light Efficacy, Viability, and Operational Factors
Exhibit 2-16. Ultraviolet Irradiation Curves for Protozoan Type Organisms
(Karanis et a!., 1992)
(a)
50
100
150
200
Dose mWs/cm2
Ultraviolet irradiation curves (a) 48-h-o!d Trichomonas vaginalisirom a medicinal spring (5 x 104
trichomonads/ml; n=10 trials), (b) Acanthamoeba rhysodesirom tap water (1x103amoebas/ml:)
(o) 7 day-old-trophozoites (n=2 trials). (•) 28-day-old cysts (n=3 trails), (c) Giardia lamblia from
distilled water: (a) 2 x 1034-9-day-oId group: cysts/ml from humans (1 trail); (•) 9-27 x 10s 3-9-
day-old group II cysts/ml from gerbils (n=4 trials). . .
UV Light Disinfection Technology in
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Final—September 1996
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Chapter 2—Assessment of Ultraviolet Light Efficacy, Viability, and Operational Factors
exclusion of two vital dyes). To adequately determine ultraviolet light disinfection potential against
Cryptosporidium parvum using the same system and dose, Campbell et al. (1995) recommended the use
of an automated counting system such as flow cystometer and suggested that the use of such technique
might reveal an actual log reduction in viability that is higher than the morphological enumeration
technique used by the researchers. The best defense against Cryptosporidium parvum is filtration, with
slow sand filtration providing the possibility of 5 to 6 log reduction in oocysts (Jeffrey, 1991).
A recent report (SWS, 1996) by Clancy Environmental Consultants (CEC), with the support of the
University of Arizona, agrees generally with the above-cited findings of Campbell et al. regarding the
efficacy of ultraviolet irradiation of Cryptosporidium parvum in water. The device, composed of filters
(2 urn nominal) that capture Giardia and Cryptosporidium oocysts and ultraviolet irradiation at a
maximum dosage of greater than 8,000 mWs/cm2, was tested and found to produce a greater than 3 log
reduction in oocyst viability. Tests were conducted on cold (4°C) treated surface water. In addition, an
accompanying animal infectivity study was conducted that led investigators to believe that reductions may
have been much greater, because no animals were found to be infected. Some cautions were expressed
by the investigators, mainly in the area of examination of oocysts microscopically for physical
characteristics, damage, and/or viability. Evidently the animal infectivity part of this study provided
greater confidence in the cyst-reduction results. The investigators also point to the need for additional
study of the ultraviolet treatment unit used in the experiment under differing water quality, including
ground waters and finished surface waters. Mineral content, natural organics, and inorganic debris (silica,
clay) could affect treatment (SWS, 1996).
Recent research studies conducted by Bank et al. (1990) and Dunn, Ott, and Clark (1995) on the use of
new ultraviolet light manipulation-techniques to inactivate Cryptosporidium parvum are discussed in
Appendix B of this report.
2.2.4 Doses and Inactivation Rates Achieved in Wastewater Treatment as Compiled
from the Scientific Literature (
The National Water Research Institute (NWRI, 1993) proposed guidelines for wastewater reclamation in
California that call for a minimum dose of 140 mWs/cm2 to disinfect filtered, secondary effluent. This
dose is based on pilot studies in which 4 logs of inactivation of polioviras were accomplished at an
ultraviolet dose between 100 and 120 mWs/cm2. The works of Chen and Kuo (1992) and CH2M HILL
(1992) were,cited as a_base for the above recommendation (NWRI, 1993).
UV Light Disinfection Technology in
Drinking Water Application—An Overview 2-23 Final—September 1996
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Chapter 2—Assessment of Ultraviolet Light Efficacy, Viability, and Operational Factors
In a Canadian pilot plant study, Zukovs et al. (1986) applied ultraviolet light to disinfect effluent combined
sewer overflows (CSOs). Log reductions ranging from 1.5 to 3.5 for Pseudomonas aeruginosa were
achieved at ultraviolet light doses of 100 mWs/cm2 to 500 mWs/cm2. Pseudomonas aeruginosa can cause
illness, especially in immunodepressed patients. In water jt can be found even in the absence of coliform
bacteria and can cause enteric, eye, ear, and upper respiratory tract infections (USEPA, 1984);
Dizer et al. (1993) conducted a detailed study on the use of ultraviolet light for inactivation of bacteria
and coliphage in a mix of 70 percent domestic wastewater secondary effluent and 30 percent surface
water. Dizer et al. (1993) also used cultured bacteria that were artificially added to the ultraviolet reactor.
The results of his study are presented in Exhibit 2-17. The reduction in inactivation rates in coliphage
adsorbed to colloidal material from 94 percent (1.22 log reduction) to 54 percent (0.34 log reduction)
indicates the limits of ultraviolet use for disinfection of turbid or unfiltered drinking water sources at the
dose used in this experiment.
Exhibit 2-17. Inactivation of Microorganisms in a Mix of 70% Domestic Wastewater,
Secondary Effluent, and 30% Surface Water as Reported in Dizer et al. (1993)
Microorganism
Range of Log Inactivation9
11 2
3
-4
Natural " •
Total Coliform
E. Col!
Fecal streptococci
Colfphage f2
<***********>
<*""**"**>
1
Artificial Trter
Coliphage f2
Adsorbed Coliphage f2b
Free Coliphage 12°
Salmonella enteritidis
Streptococcus faecalis ,
<***********>
0.33
1.22
I
*
'Reported ultraviolet light dose in the study is 47 mWs/cm2. Residence time 3.54 seconds.
Introduced to the reactor adsorbed to colloids in a slurry containing fine sand soil sediment of 0.1 g/ml concentration.
introduced to the reactor in a slurry medium containing fine sand soil sediment of concentration of 0.1 g/ml.
Dizer .et al. (1993) results show lower inactivation rates when compared to experiments using laboratory-,
cultured microorganisms. Reports of the high sensitivity of various laboratory-cultured microorganisms
to ultraviolet disinfection as compared with naturally occurring microorganisms confirm the findings of
Dizer et al. (1993) (Martiny, Wlodavezzyk, and Riiden 1988; Martiny et al., 1988; Martiny, Seidel, and
Riiden, 1989; and Sommer et al., 1989). '..'•-.
UV Light Disinfection Technology in
Drinking Water Application—An Overview
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Final—September 1996
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Chapter 2—Assessment of Ultraviolet Light Efficacy, Viability, and Operational Factors
Naranjo et al. (1993) evaluated the removal of coliphage MS-2, rotavirus SA-11, and poliovirus 1 from
wastewater by ultrafiltration and ultraviolet disinfection. The study did not report the intensity, time, or
dose of ultraviolet light applied. The study reported an average removal of MS-2 of more than 4 log in
all tests after ultrafiltration achieved log reduction between 2.3 and 3 in four experiments. Because of the
high levels of viruses used in the study, Naranjo et al. (1993) concluded that using this system to treat
drinking water would result in no detectable enteric viruses in the final product water.
In recent research, Oppenheimer et al. (1993) conducted a study on microbial inactivation rates and by-
products formation in reclaimed water in California. Oppenheimer et al. analyzed samples collected from
tertiary effluent at the Elsinore Valley Municipal Water District (EVMWD) Regional Plant. The
bacteriological analysis included heterotrophic plate count, fecal streptococci, fecal coliform, total coliform,
OX174 virus, MS-2 bacteriophage, and enterococci. The inactivation rates test results of Oppenheimer
et al. are presented in Exhibit 2-18. The tertiary effluent quality parameters include a total dissolved
solids level of 664 mg/L, a turbidity level of 0.6 NTU, a nitrate level of 13 mg/L as N, and a TOC level
of 5.6 mg/L. Exhibit 2-18 shows that the bacteriophage MS-2 is more resistant to ultraviolet light
treatment than all the other microorganisms tested in the experiment.
Exhibit 2-18. .Ultraviolet Light and Chlorine Doses to Achieve 99.9% Inactivation
of Microorganisms in Reclaimed Water (Oppenheimer et al., 1993)
Organisms
Ultraviolet Light Dose (mWs/cm^)
Chlorine Dose* (mg/IY
Bacteria
Heterotrophic Plat Count •
Total Coliform
Fecal Coliform
Fecal Streptococci
Enterococci
70
35
30 '
30
30
3.0
2.5
1.5
.2.5
3.0
Virus
MS-2 ,
«>X174
85
20 ,
1.0
0.5
*2 hours contact time.
Ultraviolet light treatment pilot studies have been plagued by varying sensitivity of bacteria and the
differences in applied intensities or the lack of reporting for such information. Quails et al. (1985), using
a simplified system where various water quality parameters could be accurately measured, conducted an
average of 33 to 35 observations of irradiated unfiltered effluent samples and concluded that ultraviolet
light sensitivity of a single cell and small aggregates of coliforms are relatively uniform from plant to
UV Light Disinfection Technology in
Drinking Water Application—An Overview 2-25 Final-^September 1996
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Chapter 2—Assessment of Ultraviolet Light Efficacy, Viability, and Operational Factors
plant. However, the wide variation in survival curves is caused by the varying degree of protection
afforded by different particle sizes arid by the varying proportion of coliforms that are aggregates or
attached to colloids particles. Exhibit 2-19, provided by Quails et al. (1985), is useful as a generalized
range of coliforms survival data for planning equipment needs where accurate dose-survival data do not
exist and pilot studies are deemed expensive. The upper and lower graph boundaries represent samples
± standard deviation bars. ' .
Exhibit 2-19. Average 33 to 35 Observations of Log Survival of Co I if or m Bacteria in
. Unfiltered Effluent Samples (Quails et al., 1985)
Or-
10
15 20 25 30
DOSE (mW-s/cm2!.
35
4O
45
Harris et al. (1987) studied the effects of turbidity on ultraviolet disinfection of secondary municipal
wastewater effluents and photoreactiyation potentials using two different ultraviolet light reactors. Harris
et al. observed up to 2 log survival in total coliform photpreactivation and little evidence of photo-
reactivation of fecal streptococci. Exhibit 2-20 is a graphical presentation of the relationship between
ultraviolet absorbance at 254 nm and turbidity as reported by Harris et al. 1987. The study showed highly
significant correlations between suspended solids, fecal coliforms survival at 5 mWs/cm2, and ultraviolet
light absorbance at 254 nm. The researchers concluded that wastewater turbidity can be used as a good
surrogate measure of disinfection efficiency and ultraviolet light absorbance. The graph shows that at a
turbidity level close to 5 NTU, about 25 percent of ultraviolet light transmittance is absorbed by turbidity-
causing wastewater constituents. It should be recognized that other factors (iron, organics, etc.) may play
an additional role in absorbing ultraviolet light in practical drinking water use. However, for drinking
water applications and in the absence of similar experiments in turbid drinking water, the Harris et al.
work can be used as a base to account for turbidity absorbance of ultraviolet light.
UV Light Disinfection Technology in
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Final—September 1996
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Chapter 2-Assessment of Ultraviolet Light Efficacy, Viability, and Operational Factors
Exhibit 2-20. Ultraviolet Light Absorbance as a Function of Turbidity (Harris et al., 1987)
W.O
4.0-
2.O-
0.0
Turbidity - 28.18 Absbrbonce -2.26
r'-O.TS
0.70 0.25 0.30
UV Absofbonce (254 nm)
0.40
0.48
2.3 ULTRAVIOLET LIGHT OPERATIONAL FACTORS
In this section, factors such as operating procedures and requirements, maintenance requirements,
installation features, and design elements are analyzed to determine the viability of ultraviolet light in a
ground water treatment setting.-This section is organized as follows: section 2.3.1 presents a general
description of ultraviolet light equipment operational factors; section 2.3.2 discusses water .quality
considerations. Hydraulic design considerations are presented in section 2.3.3; and design considerations
specific to small systems are presented in section 2.3.4.
2.3.1 Equipment Operational Factors
Ultraviolet light bulb efficiencies decline over time. Therefore, it is important when adopting a standard
for ultraviolet light treatment that the standard reflect the efficiency of the light bulb at its lowest point
according to the manufacturer's suggested effective use time. The current effective life of ultraviolet light
bulbs ranges from 7,000 to 14,000 hours (Aquafine, 1995). Industry brochures show about 30 percent
reduction in light transmission efficiency over aperiod of 10,000 hours. Operators and maintenance crews
need to be adequately trained to service the equipment as recommended by the manufacturer.
UV Light Disinfection Technology in
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Chapter 2—Assessment of Ultraviolet Light Efficacy, Viability, and Operational Factors
The operational factors that affect adequate performance of an ultraviolet light system are lamp output,
lamp aging, and fouling of unit surfaces. '
2.3.1.1 Lamp Output
Ultraviolet lamp output is directly dependent on the optimum conditions of the mercury vapor discharge
requirements. These requirements include a steady electric potential that does not fluctuate and drop
below a certain level set by the designer. For example, a drop of 5 volts ,in the electric potential
difference acting on a 5-amp lamp means a drop of 25 watts in energy available to the lamp.
Another factor that affects the output of a standard ultraviolet lamp is temperature. The optimum
temperature for maximum ultraviolet lamp efficiency is generally between 35°C (95°F) and 50°C (122°F).
Maintaining optimum temperature and pressure in an ultraviolet lamp is important to maintain maximum
light emission at the desired wavelength. This concern is less important in new ultraviolet lamp models
that have devices to regulate temperatures and in those that can operate at temperatures higher than 50°C
(122°F).
2.3.1.2 Lamp Aging
Several factors affect the performance of an ultraviolet lamp as it advances in hours of use: solarization
(i.e., the effect of ultraviolet light on the lamp and the sleeve that causes lamps to become opaque over.
time), electrodes failure, and plating of the mercury to the interior lamp wall. If combined, these factors
might reduce the efficiency of an ultraviolet light lamp by as much as 30 percent after 7,000 hours of use.
The electrodes in an ultraviolet lamp will deteriorate progressively with an increase hi the number of times
the lamp is started. According to various industry sources, the maximum allowed number of starts per
lamp per day is four. In a typical potable water application, ultraviolet lamps are expected to run 24 hours
per day. According to various industry sources, the current effective life span of an ultraviolet lamp
ranges from a minimum of 7,000 hours to,a maximum of 14,000 hours. •
2.3.1.3 Fouling and Plating of Lamps and Sleeves
Fouling of the unit's quartz sleeves surface reduces the light energy reaching the volume of water.
Typically, high quality fused quartz sleeves have a transmissibility of more than 90 percent when new and
clean. With time, the surfaces of the quartz sleeves that are in contact with the body of water start
collecting organic and inorganic debrisr—such as calcium scale, silt, or iron fouling—causing a reduction
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Chapter 2-Assessment of Ultraviolet Light Efficacy, Viability, and Operational Factors
in transmissibility. Therefore, it is very important to maintain the surfaces of the sleeves to ensure that
they are clean and free of deposits. . -
To .maintain clean ultraviolet units, mechanical wipers can be used. However, like all other mechanical
devices, they must.be checked periodically to ensure that they are sufficiently cleaning the lamps. To
combat fouling, ultrasonics are highly recommended in hard water situations and in .ground water that
contains iron. The alternative to ultrasonics is the periodic use of detergents such as sulfuric acid or
hydrochloric acid. To combat plating (forming a thin coating on surfaces), high water pressure also is
used effectively to routinely clean the inside surfaces of the ultraviolet unit. High water pressure cleaning
techniques are recommended in situations where ground water contains very fine silt materials, sulfites,
or manganese. \ .
Kreft, Scheible, and Venosa (1986), based on hydraulic studies conducted on three wastewater ultraviolet
treatment units, recommended both chemical and physical cleaning of ultraviolet units. They also
suggested the use of high-pressure nozzles to scour fouled surfaces and arecirculation system for chemical
cleaning. The researchers found that.wipers and ultrasonics have a great potential for keeping clean units,
but neither negates the necessity for occasional chemical treatment or swabbing of the ultraviolet tubes.-
2.3.2 Water Quality Considerations
The performance of an ultraviolet disinfection system is directly related to ultraviolet light absorbance by
the treated water. When ultraviolet light travels through the water body, the light intensity decreases as
the distance from the light source increases. This is caused by energy dilution as light dissipates in a
larger volume of water. Another factor that causes ultraviolet light to be absorbed is'water quality.
Ultraviolet absorbance by water is analogous to chlorine demand in chemical disinfection processes.
However, with respect to ultraviolet applications, Weber (1989) suggested that pure water also exerts an
ultraviolet demand. Weber (1989) reported that even distilled water absorbs about 8 percent of the applied
ultraviolet energy at a depth of 3 cm'. , '
The transmittance of water commonly is used to describe the ultraviolet demand. This can be determined
from the absorbance measurement expressed in percent:
% Transmission = 100 x l(T(a-u-A:m)-d
.Where: a.u. = absorbance units
d = distance in centimeter
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Chapter 2—Assessment of Ultraviolet Light Efficacy, Viability, and Operational Factors
The percent absorbed is 100 percent minus transmission. The parameter most often used for design
purposes is the Coefficient of Absorbance (C of A) or cc expressed as
a = 2.3 (a.u./cm).
The unit of ultraviolet absorbance coefficient is cm"1.
In general, ultraviolet absorbance coefficients decrease with an increase in water quality.
Exhibit 2-21 (courtesy of Aquafine Corporation) presents absorbance coefficient curves as a function of
ultraviolet light transmission and distance. For ground water systems using ultraviolet light for
disinfection, it is important to determine the absorbance coefficient by sampling at different periods during
the year to account for seasonal and temporal water quality fluctuations. In the absence of field data,
Exhibit 2-21 or similarly constructed graphs can be used to select an appropriate absorbance coefficient.
From Exhibit 2-21, an absorbance coefficient of 0.1 may be a reasonable conservative assumption "a"
value for ground water.
Exhibit 2-21. Ultraviolet Transmission and Absorbance Coefficient
(Source: Aquafine Corporation, 1995)
C of A Values
o
1
i
High purity water: a = 0.01
Municipal drinking water: a = 0.06 to
a = 0.15
% Transmission at "d": = 100 x'lo;(ail-/en*d
= 100 x e^"
0 2 4 S 8 18 12 14 16 11
Distance (cm)
As with other disinfection technologies, better disinfection results are achieved with ultraviolet light if the
water is free of turbidity. Ultraviolet industry representatives recommend that ground water with a
turbidity level of 5 Nephelometric Turbidity Units (NTUs) or more should be treated for turbidity removal
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Chapter 2—Assessment of Ultraviolet Light Efficacy, Viability, and Operational Factors
before it is ran through the ultraviolet light reactor (Atlantic Ultraviolet Corporation, 1995a; Voitle, 1994;
Wagenett and Lemley, 1994). Similarly, ground water with suspended solids levels of more than 10 mg/L
(10 mg/L was the U.S. Department of Health drinking water standard for turbidity [Steel, I960]) should
be monitored to determine whether the high levels are of a permanent, seasonal, or ephemeral nature.
Knowing the upper range of suspended solids in water is important in order to determine which type of
ultraviolet light unit will be required.
In wastewater applications, ultraviolet systems are designed to accommodate liquids with suspended solids
levels as high as 30 mg/L for any consecutive 30:day period (WPCF, 1986). Therefore, ultraviolet
systems for ground water disinfection could be designed to allow for high suspended solids situations
although such levels are not expected to occur in drinking water situations. To compensate for ultraviolet
light absorbed by high levels of suspended solids, higher ultraviolet light doses need to be applied in order
to achieve desired levels of disinfection.
The two major water quality factors that affect the performance of an ultraviolet unit in (clear) ground
water are microbial factors and chemical factors.
Severin, Suidan, and Engelbrecht (1983) studied the-effects of temperature on ultraviolet light disinfection
and found that ultraviolet disinfection is relatively insensitive to temperature changes. The disinfection
tests were conducted at 5°C, 20°C, and 35°C. However, earlier in vitro studies showed that more
disinfection may occur at lower temperatures than at higher temperatures because at lower temperatures
(below 25°C), single-stranded polynucleotides and DNA strands are in a stacked configuration. Stacked
DNA and stacked single-stranded polynucleotides are more subject to dimerization than unstacked DNA
(Rahn, 1970). Malley, Shaw and Ropp, 1996 (as cited in Snicer et al., 1996) concluded that pH levels
might have an effect on ultraviolet light disinfection efficiency. The researchers attributed the detected
effect to morphological changes in the nature of the protein coat that caused clumping of microorganisms.
Montgomery (1985) and USEPA (1986) reported that disinfection by ultraviolet light is pH independent.
As mentioned earlier, AWWA (1992) reported that research studies conducted at the University of New
Hampshire show that ultraviolet light disinfection processes are independent of water pH. Therefore,
unlike chemical disinfection processes, water quality parameters such as temperature and pH have an
insignificant effect on ultraviolet light disinfection capabilities. In chemical "disinfection processes, an
-increase in temperature results in an increase in the killing rate of the disinfectant. This, could be
explained in the context of increased chemical reaction rate and in the decrease of surface tension between
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Chapter 2—Assessment of Ultraviolet Light Efficacy, Viability, and Operational Factors
microorganisms, microorganisms and colloidal particles, and the decrease in the viscosity of the medium
(Gaudy and Gaudy, 1980). In chemical disinfection processes, pH influence on disinfection rate varies
from one chemical to the other. For example, an increase in pH will decrease the disinfection efficiency
of chlorine gas and slightly increase the disinfection efficiency of chlorine dioxide (Montgomery, 1985).
*. .•-.-•
Important microbial water quality parameters to be taken into account when selecting an ultraviolet unit
for disinfecting ground water are the microbial water quality and the densities of the microbial population.
High densities of the microbial population may cause a decrease in the inactivation efficiency of ultraviolet
light by shielding and hosting. For an adequate evaluation of the microbial parameters and the potential
for microbial contamination, it is recommended that water samples be taken during the warm season after
a rainy period to test for Heterotrophic Plate Count (HPC), HPC, also known as the standard plate count,
is a procedure for estimating the number of live heterotrophic bacteria in water and measuring changes
during water treatment and distribution. In an HPC procedure, colonies may arise from pairs, chains,
clusters, or single cells, all of which are included in the term "colony-forming units" (CPU). A high HPC
of more than 500/ml may cause a decrease in inactivation rate of viruses (by shielding and hosting).
Therefore, it is important to have the microbial data available before purchasing and installing an
ultraviolet unit.
The effect of the ultraviolet light on microorganisms is a function of the energy absorbed by the
microorganism. The energy absorbed is defined as the product of the rate at which the energy is delivered
and the length of time the microorganism is exposed to that intensity.
The ideal ultraviolet disinfection model follows Chick's law (Chick, 1908) whereby:
N = Noe'*1 ; - .
Where No = initial bacterial population
N = surviving bacterial population after exposure to ultraviolet light
k = rate constant
i = intensity of ultraviolet light
t = time of exposure.
Exhibit 2-22 is a graphical presentation of Chick's law and deviations from it. Chick's law assumes a
uniform susceptibility of all organisms within the strain or species. Deviations from this ideal first order
representation are manifested by tailing effects and shouldering. In general, the presence of "shoulders"
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Chapter 2-Assessment of Ultraviolet Light Efficacy, Viability, and Operational Factors
Exhibit 2-22. Chick's Law and Deviations (Source: USEPA, 1986)
o
Z
O
^5
CO
oc
1
•>
D
C?
Shoulder
(Threshold dose)
Tailing
Ideal First Order
= e
UV Dose {Dose = IT)
indicates a time lag between the application of ultraviolet light and the onset of disinfection. The presence
of "tailing" indicates a decrease in the rate of inactivating surviving microorganisms at higher ultraviolet
energy doses. ,
The presence of a "shoulder" or "tailing off' or both may be explained by the following:
• The presence of protective extracellular layers '
• The presence of colloids that absorb ultraviolet light
• The presence of organic and inorganic substances that absorb ultraviolet light
• The presence of organic and inorganic substances that induce microbial resistance to ultraviolet
light. ...... .
• Inherent differences in sensitivities of the microbial population.
Although avoiding "shouldering" and "tailing off' in disinfection processes is difficult, knowing water
quality parameters and designing an ultraviolet system accordingly may result in a lesser manifestation
of such phenomena.
Like chemical disinfectants, there are chemical and water quality factors that affect the performance of
an ultraviolet light disinfection unit. These factors are presented in Exhibit 2-23 and include hardness,
nitrites, sulfites, manganese, and aromatic organics levels. These water quality factors are known to,
icause
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Chapter 2—Assessment of Ultraviolet Light Efficacy, Viability, and Operational Factors
Exhibit 2-23. Factors Affecting Ultraviolet Light Disinfection Performance*
Factor
Hardness
Iron
Nitrites
Sulfites
Manganese
HPC
Aromatic organics
Turbidity
Ultraviolet transmission
inorganic suspended solids
Color
> 100 mg/I
£ 0.2 mg/I
> 500
> 10 NTU
< 75%
> 5 urn
> 15 NTU
Short circuiting in contact chamber
High flow rate
Low line voltage supply
Improper lamps arrangement
Effect
Plating**
Fouling***
Plating
Plating
Plating
Decrease inactivation of viruses
Plating
Plating
•Inadequate destruction
Shielding
Reduce disinfection efficiency
Inadequate inactivation
Reduce disinfection efficiency
Low light transmission
Low light efficiency decrease inactivation efficiency
'USEPA, 1992. Draft Ground Water Disinfection Rule FR.; Negron, 1994.
"Forming a thin coating on surfaces.
""Incrustation.
plating (the coverage of inner surfaces with a layer of minerals) and fouling (the formation of a crust on
sleeve and inner sides of the unit) in ultraviolet units that are not equipped with mechanical wipers and
ultrasonic cleaners. "Plating and fouling cause inadequate ultraviolet light transmittance and a decrease in
inactivation efficiency. Modern ultraviolet units are equipped with automatic wipers and ultrasonic
cleaners. The continuous action of the mechanical wipers along with periodic ultrasonic cleaning greatly
reduces plating and fouling. It is recommended, as a good process tracking tool, that a log be maintained
to record all water quality parameters to recognize any change in ground water quality. For example,
levels of nitrites in particular are required to be kept at less than 1 mg/L. Nitrites are regulated under the
National Primary Drinking Water Regulations, and their presence in ground water sources may indicate,
in the absence of any other explanation, a fresh contamination that requires immediate response.
Other secondary contaminants need to be removed for other reasons. For example, although iron is not
a primary drinking water contaminant, iron removal from drinking water sources is highly desirable and
is more economical at the treatment plant than at the tap. Ground waters with dissolved iron content
above 0.3 ppm will cause brown-red stains on sinks, porcelain, and bathroom fixtures. Upon heating, the
clear water color will turn brown-red and will cause cloth discoloration and brown-red stains on cooking
pots. At above 3 ppm of iron content, the water will have an offensive metallic taste and the water will
be colored. In some cases, precipitation will occur; in other cases, a brownish cast that does not
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Chapter 2—Assessment of Ultraviolet Light Efficacy, Viability, and Operational Factors
precipitate will persist. Some iron-containing waters have iron in colloidal form, thus making drinking
water very offensive to look at and to use for drinking, cooking, or washing (USEPA, 1991a). Although
there are no known health risks associated with high iron levels in drinking water, aesthetic qualities are
very important to assure users of the safety .of their drinking water,
2.3.3 Hydraulic Design Considerations
The major elements that must be considered in the hydraulic design and operation of an ultraviolet reactor
include the following: .
• Dispersion . .
• Turbulence
• Effective volume ,
• Residence Time Distribution (RTD) _ -
• Flow rate.
2.3.3.1 Dispersion
Dispersion is the characteristic of water elements to scatter spatially in two or three dimensions. The ideal
ultraviolet light disinfection reactor is a Plug-Flow Reactor (PFR). In a PER,, water particles are assumed
to enter into the reactor and discharge from the reactor in the same sequence they entered. Therefore, in
a PFR, each element of the water passing through the reactor resides in the reactor for the same period
of time. Hence, an ideal PFR has no flow dispersion. In reactor design, this type of flow is approximated
in a long tank with high length-to-width ratio in which longitudinal dispersion is absent or minimal.
2.3.3.2 Turbulence
In addition to the desired PFR characteristics, an ideal ultraviolet light reactor is a reactor with a flow that
is turbulent radially from the direction of flow with no dead zones. The radially turbulent flow pattern
promotes more uniform application of ultraviolet light. However, having a radially turbulent flow results
in some axial dispersion, thus disrupting the ideal plug flow sought in a disinfection reactor. By not
aligning inlets and outlets of units and using perforated.baffle plates, designers accommodate the
contradicting plug flow and turbulence requirements.
2.3.3.3 Effective Volume
Avoiding dead zones (i.e., areas of no or reduced flow) results in maximum use of the volume of the
reactor. It also results hi an effective, volume as close as possible to the actual volume Available. Exhibit
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Chapter 2—Assessment of Ultraviolet Light Efficacy, Viability, and Operational Factors
2-24 presents a configuration (top figure) of a closed ultraviolet light reactor where dead zones are induced
by a specific, inlet and outlet configuration. Trie exhibit shows how the introduction of perforated baffle
plates can help distribute the flow over the entire cross-sectional plane of the reactor, thereby eliminating
dead zones.
Exhibit 2-24. Closed Ultraviolet Light Reactor (USEPA, 1986)
Lamp Battery (Generally
parallel to flow Path)
\_
/, /
Potential
Dead Zones
Perforated Baffles
2.3.3.4 Residence Time Distribution (RTD)
RTD is used as a design and diagnostic tool to determine the effects of hydraulics on the ultraviolet
system performance. The shape of the curve and the distribution of the area under the curve indicate the
hydraulic characteristics of a system and also indicate whether it is close to an adequate disinfection
design. Exhibit 2-25 presents RTD curves for various flow characteristics.
An RTD curve closer to a Continuous-Flow Stirred Tank Reactor (CSTR) or to an arbitrary flow curve
than to a PFR curve indicates inadequate performance and poor design. An RTD curve is generated by
sampling water at successive intervals of time to measure for concentrations of a non-reactive
(conservative) tracer that is pulse-injected into the reactor and then plotting the concentration values versus
time. Detailed discussions on RTD and dispersion models in plug-flow reactors are found in Metcalf and
Eddy, 1991; USEPA, 1986; and WERF, 1995.
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Chapter 2—Assessment of Ultraviolet Light Efficapy, Viability, and Operational Factors
Exhibit 2-25. Residence Time Distribution Curves
Flow Characteristics
Arbitrary (c)
Row
(Age Distribution)
Area =
(a) CSTR
(b)PFR
(c) Arbitrary
(d) Hypothetical Resj
Concentration
o*
Tracer
2.3.3.5 Flow Rate
The flow rate is usually set by design based on projections of water consumption. Because multiple
parallel ultraviolet units may be used in a water treatment plant, balanced flow split between modules is
important for two reasons: first, the balance will avoid overloading a single unit or group of units,
hydraulically and with deposits, and second, the inactivation rate increases as flow rate decreases (Sommer
and Cabaj, 1993). - . , -
/ , . " i '
Sommer and Cabaj (1993) conducted experiments on Bacillus subtilis spores using various flow rates of
potable water and ultraviolet doses. The researchers showed that a decrease in ultraviolet transmission
results in a decrease in Bacillus subtilis spore inactivation. The spore reduction could be read directly as
a function of dose and transmission, for different flows treated in the same reactor. The work of Sommer
and Cabaj as presented in Exhibit 2-26 is important because it provides a view of the range of practical
application of ultraviolet light in water disinfection under various flow conditions. In any case, it is
important that actual flow through an ultraviolet unit does not exceed the manufacturer's recommended
Tflow rate. • ,
2.3.4 Small System Design Considerations
Ultraviolet equipment varies in design. Minor design details may have significant effects on operation
and disinfection capabilities of the ultraviolet light unit. Therefore, onsite testing of the equipment may
be recommended to determine whether the unit is properly designed for a specific quality of water. It is
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Chapter 2—Assessment of Ultraviolet Light Efficacy, Viability, and Operational Factors
Exhibit 2-26. Practical Application of Ultraviolet Light in Water Disinfection, Surrogate
Used Bacillus subtilis (Source: Sommer and Cabaj, 1993)
Reduction [log]
Dose mWs/cm2
5-
4-
3-
2
n
80
65
50
35
20
IS Im3/h]
2.5 (ma/hl
3.5lm3/h)
4.5lm3/hl
0 10 20 30 40 SO 60 70 80
Transmission (10 cm; 254nm) %
recommended also that an engineer design the disinfection system or that an independent third party test
the efficacy and reliability of the equipment under various raw water conditions. Testing an ultraviolet
unit should include efficiency tests under low flow conditions, high flow conditions, low quality water,
and for multiple lamp units, simulation of a situation where one or more lamps are not functioning.
(Efficiency tests involve injecting a bacterium stock [challenge microorganism] at a steady rate into the
reactor and assaying the effluent to determine surviving population.)
For small ground water applications, ultraviolet systems should consistof multiple units rather than one
unit, even if one is capable of carrying the entire design flow. Backup or dual units serve the purpose of
maintaining a continuous disinfection process while a unit is being serviced. Also, a system with multiple
units can shut down a unit during low flow. Therefore, at a niinimum, two ultraviolet units should be
provided per system with each unit capable of carrying peak hourly flows.
For a small public water system, it is recommended that all electric fittings be of the modular type in order
to make installation, replacement, and maintenance quick and easy. It is also important that the
manufacturer provide information on the unit's theoretical and mean residence time at specific flows, as
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Chapter 2—Assessment of Ultraviolet Light Efficacy, Viability, and Operational Factors
well as information on peak design flow, ultraviolet transmission assumptions, and minimum dose at the
end of the lamp's life. Operation manuals should include a description of control systems, alarm
functions, records, and reports. >
The manufacturer should provide an equipment operation plan that includes procedures and intervals for
cleaning sleeves, frequency of lamp replacement, and frequency of calibration of monitoring equipment.
The operator of the ultraviolet unit should be well informed about the location, access, and quantity of
a backup supply of lamps, ballasts, and Other critical components. Contingency plans for emergencies that
necessitate a complete shutdown of the ultraviolet system should be drafted before the system is up and
running.
For small ground water systems installing an ultraviolet unit, the operators should consider the following:
• The ultraviolet system should be installed in a place that would permit free movement around"
the unit and ample space for service (lamp and sleeve removal, periodic cleanup).
-An ultraviolet unit should be equipped with before-and-after shutoff valves, and the housing
should have a drain close to the ultraviolet unit to minimize the amount of water the service
personnel will encounter upon opening the unit for service.
• Cleanliness of an ultraviolet reactor is an important operation and maintenance issue; therefore,
continuous intensity monitoring is recommended to detect fouling of the system.
Operators of small public water systems should at a minimum do the following:
• Check fail-safe devices for proper operation.
• Calibrate me ultraviolet intensity measuring periodically for proper sensitivity.
- Disconnect the unit and clean the lamps by wiping with a soft cloth moistened with ethanol
(APHA, 1989) or any other solvent recommended by the manufacturer.
• Inspect and/or clean the ulterior of the ultraviolet chamber every 6 months.
• Examine seals annually (and then calibrate the intensity meter). Replace the lamps if they emit
less than 70 percent of initial output.;
' ' -• f
• Monitor water turbidity and color since they are natural barriers to the transmission of
ultraviolet light. Also, some dissolved minerals have a tremendous effect on ultraviolet
absorbance. For example, iron as low as 1 ppm may increase absorbance of ultraviolet li^ht
by more than 80 percent (Weber, 1989).
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Chapter 2—Assessment of Ultraviolet Light Efficacy, Viability, and Operational Factors
Operators of very small ground water systems are not typically in the treatment plant on a daily basis and
are not expected to be on duty 24 hours a day. Therefore, it is recommended that the operator be
equipped with a remote system (telemetering) that at a minimum can provide alarm signals for major
ultraviolet light system failure. .
Major or high priority alarm systems are alarm systems that are initiated by a unit failure or a component
failure that might result in an unacceptable level of disinfection. Major alarms, as opposed to minor
alarms, are those alarms that would sound or flash in case of ultraviolet lamp failure, power failure, unit
failure, or ballast failure. Minor alarms are those alarms that would indicate the failure of equipment that
does not affect the disinfection process directly such as a light-emitting diode failure. Many ultraviolet
i
light systems are equipped with automatic treatment plant shutdown in case of a major equipment failure.
In its comment on the Draft EPA GWDR, AWWA suggested that ultraviolet light systems be.required to
have the following minimum operational controls and procedures: •
• A central display showing indicators and alarms for power failure, lamp failure, hours of lamp
operation, low ultraviolet dosage, high lamp temperature, high ballast temperature, and high
system flows. ' - .
• Systems that monitor lamp temperature, ballast temperature, and system water flows.
•• A photodiode sensor to monitor ultraviolet dosage at 254 nm. A minimum of two sensors per
unit is recommended. These sensors must be'calibrated using approved standards each time the
lamps are cleaned or replaced or the ultraviolet chamber is serviced; •
• Automatic ultraviolet system by-pass or shutoff to be activated whenever peak design flow rates
are exceeded, when ultraviolet dosage is low, or when lamp or ballast temperatures are high.
• System redundancy should be provided for the average flow when the largest unit is out of
service. ...•/..,
To assess ultraviolet disinfection viability for small drinking water treatment systems, an evaluation should
be made of system flexibility, reliability, complexity, and effectiveness. Ultraviolet systems in modular
units are easy to upgrade, accommodate flow expansion plans in phases, and are easy to maintain and
service. For ground water situations where water quality does not fluctuate as much as surface water
quality, ultraviolet systems are reliable and can perform well if properly maintained.
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Chapter 2-Assessment of Ultraviolet Light Efficacy, Viability, and Operational Factors
Modern ultraviolet light systems are less complex than early ultraviolet models. They are easier to install,
requiring only one electrical connection and two plumbing connections. Changing lamps in modern
models is no more difficult than changing a fluorescent light bulb.
For small, ground water systems, particularly TNC and NTNC water supply systems, ultraviolet
disinfection systems may be more appropriate than chlbrination and ozonation, when the ground water is
high in THM precursors, for the following reasons:
• Ultraviolet light does not generate THMs.
• For disinfection, ultraviolet light is pH and temperature independent.
• Ultraviolet light is effective in inactivating many pathogenic bacteria and viruses and at higher
doses is effective against protozoa.
• There is no danger of overdosing.
• There are no safety precautions to be taken for transporting, storing, or applying chemicals.
• Environmental impacts from ultraviolet systems are lower'than impacts related to the use of
chlorine or ozone.
• The equipment is reliable and easy to maintain. Many manufacturers provide equipment
warranties and transmission performance warranties.
'. . i •• ' - .
• Process control is flexible and simple. •
• Overall, operation and maintenance costs are low.
• There is no need for daily measurement of chemical dose.
• There is no need to prepare fresh stocks of disinfectants (as. is the case when using sodium or
calcium hypochlorite).
' .. • ' . - - N . ' '
Following are additional factors that should be considered in the design and operation of an ultraviolet
facility.
2.3.4.1 Inspections and Shutdown
For small water systems using ultraviolet light for disinfection, it is important to. maintain a clean.
ultraviolet unit and conduct periodic inspections of all monitoring devices. Adequate training of the
ultraviolet unit operator is essential, and emergency plans should be in place in case of a ultraviolet system
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Chapter 2—Assessment of Ultraviolet Light Efficacy, Viability, and Operational Factors
shutoff. If a shutdown occurs, emergency plans must ensure that positive pressure is maintained in the
water supply network to prevent infiltration and cross-contamination and to provide for fire protection.
2.3.4.2 Distribution System ,
For small ground water systems installing ultraviolet units for disinfection, it is important to exercise good
sanitary practices, particularly if ground water contains dissolved organic compounds (DOCs) and natural
organic matter (NOM). It is recommended that these systems flush the distribution network, particularly
dead ends, before installing ultraviolet units and at least once or twice in spring through summer when
temperatures rise. Flushing and cleaning the system is recommended to remove accumulated sediments
and reduce biofilm accumulation in the pipe network, reservoirs, and storage tanks. Both sediments and
biofUm contain essential substrates that will increase the likelihood of microbial reactivation (as discussed
in section 2.4.2). .
2.3.4.3 Monitoring Devices
.Regular calibration of monitoring devices and checking key components for. proper functioning are
important steps to avoid any sudden shutdown or malfunction. For example, in some cases the Light-
Emitting Diode (LED) may not give a true indication of whether the ultraviolet lamp is actually operating.
Therefore, checking for a faulty LED, burned out LED, or malfunctioning ballasts should be done
regularly.
2.3.4.4 Manuals and Instructions
Instructions for installation, operation, maintenance, and initiation of service should be provided with each
system and component. Compliance with Federal, State, and local engineering, manufacturing, and safety
laws and regulations must be ensured. For example, power should be automatically switched off whenever
a unit is opened for service to protect maintenance workers', eyes. Manuals provided by the manufacturer
typically include drawings and lists of parts for ease of identification and for ordering replacement parts.
Because ballasts of ultraviolet lamps may provide a different electrical potential difference (voltage) than
those available for fluorescent lamps, operators of ultraviolet units used in water disinfection should not
use ballasts other than those specified for use with ultraviolet lamps.
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2.3.4.5 Spare Parts and Disposal
' Many small systems, particularly in remote areas, should have at a minimum a set of spare parts that
includes ballast, lamps, and sleeves. All ultraviolet systems operators, particularly small system operators
in remote areas, should follow the manufacturers' disposal and recycling guidelines for ultraviolet
mercury-containing lamps, ballasts, and sleeves.
General operation and maintenance practices are well documented in Chapter VI of Microorganism
Removal for Small Water Systems, USEPA, 1983. In addition, ultraviolet system operators should follow
the specific operation and maintenance practices for ultraviolet units that are documented in Chapter VH
of Design Manual: Municipal Wastewater Disinfection, USEPA, 1986.
2.4 OTHER CONSIDERATIONS RELATED TO THE USE OF ULTRAVIOLET
LIGHT FOR DRINKING WATER DISINFECTION
This section discusses issues related to ultraviolet treatment in drinking water. It presents scientific
findings on by-products formation and removal of organic contaminants from ultraviolet-treated drinking
water. It discusses the issues of microbial reactivation, residual disinfection, and availability of a
challenge surrogate microorganism. Finally, this section presents efficiency comparisons between
ultraviolet light and chemical disinfectants.
.- • . , , ' •
2.4.1 By-Products Formation and Removal of Organic Contaminants by Ultraviolet
Light Treatment
This section discusses the potential for by-products formation and removal of organic contaminants during
the ultraviolet light disinfection process. The effect of ultraviolet light on organic compounds is the result
of two mechanisms. The first mechanism is the direct action of ultraviolet light on the chemical bonds
of the targeted organic compounds. The second mechanism is the action of ultraviolet light on water
molecules and dissolved oxygen that results in the formation of powerful oxidizing agents, such as ozone
and hydrogen peroxide, which in turn react with the targeted organic compounds and destroy them.
Disinfection processes that result in chemical by-products that are harmful or that might contribute to
microbial growth should be controlled to minimize the presence of adverse chemical by-products in
drinking water. More details on prganics removal are presented in Appendix A. Section 2.4.1.1 provides
information on the removal of known organic contaminants in drinking water by ultraviolet light. Sections
2.4.1.2, 2.4-1.3, and 2.4.1.4 provide information available on by-products formation.
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Chapter 2—Assessment of Ultraviolet Light Efficacy, Viability, and Operational Factors
2.4.1.1 Removal of MX and Other Contaminants from Drinking Water
In a study conducted in Japan, Fukui et al. (1991) used an 18-watt, 30-cm long low-pressure ultraviolet
lamp to treat an aqueous solution containing a high potency Ames mutagen 3-chloro-4-(dichloromethyl)-5-
hydroxy-2(5H)-furanone (MX). MX is a known by-product of the drinking water chlorination process.
One milliliter of the solution was placed in a petri dish 30 cm below the lamp and irradiated for 60
minutes. The removal rate of MX was 76 percent, and its mutagenic potency was reduced by 79 percent.
The researchers found that the hydroxyl radicals1 formed as by-products of the ultraviolet irradiation were
not responsible for the removal of MX. When ultraviolet irradiation effects on MX removal were
compared to those of oxidative treatments, including H2O2 and ozone in the presence of iron ions and
thermal treatment, ultraviolet light treatment proved more effective than thermal treatment (59 percent
removal) and reductive treatments. However, the researchers noted that thermal treatment is useful for
drinking water application if boiled water is kept in a thermos jar more than 60 minutes, which is a
practice shared by many Japanese in the work force. •
Beltrfn, Garcia-Araya, and Acedo, 1994, conducted experiments on atrazine removal by ultraviolet
irradiation. The researchers concluded that mainly hydroxyl radicals are responsible for the oxidation of
atrazine. Therefore, atrazine-containing drinking water will be oxidized by ultraviolet light-generated
hydroxyl radicals during the disinfection process. However, quantification of atrazine oxidation by
ultraviolet light needs further investigation to determine the dose-degradation relationship and the effects
of chemical and physical water quality parameters oh the process.
Nick et al. (1992) noticed that many herbicides do not absorb ultraviolet light above 240 nm and that only
those herbicides that contain an aromatic ring or similar chromophore may degrade at wavelengths above
240 nm. Nick et al. (1992) showed that a conversion of more than 10 percent of atrazine, simazine,
promazine, and terbuthylazine by photodegradation did not result in mutagenicity (using the Ames test),
even when the irradiated material was applied in high concentrations. Therefore, ultraviolet photolysis
i
of triazine herbicides did not give rise to new equally or more hazardous compounds.
At a low ultraviolet light dose of 25 mWs/cm2, four triazine herbicides in drinking water degrade by up
to 5 percent (Nick et al., 1993). Adding hydrogen peroxide and/or ozone to the water to be treated for
organics control (before applying ultraviolet light) increases the reduction rate of contaminants (Frances,
'Hydroxyl radicals are formed by the portion of ultraviolet light emitted by mercury:containing lamps at 185 nm.
UV Light Disinfection Technology in
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Chapter 2—Assessment of Ultraviolet Light Efficacy, Viability, and Operational Factors
1989; Berglind, Gjessing, and Johansen, 1979). A high pH of approximately 10.3 to 10.5 also improves
total organic carbon (TOC) reduction rates (Xu et al., 1989).
Li et al., 1996, studied the effects of ultraviolet light (30-watt low-pressure lamp) on a 2 percent humic
acid (a major organic compound in natural water) solution. The test results of Li et al., 1996, show a
decrease in humic acid TOC (15 to 5 mg/L in about 375 minutes) and almost a complete loss of the
yellowish-brown color of the solution.
Awad, Gerba, and Magnuson (1993) conducted a demonstration-scale study to determine the effectiveness
of ultraviolet light in disinfecting reclaimed water. During the pilot testing doses of 45 and 147 mWs/cm2
were evaluated. Samples .from the influent and effluent of the pilot unit were collected and analyzed for
by-products, as presented in Exhibit 2-27.
Exhibit 2-27. Results of Disinfection By-Products of Ultraviolet Light
(Awad, Gerba, and Magnuson, 1993)
Parameter
Influent
Effluent
(45mWs/cm2)
Trihalomethanes, |ig/I
CHCI3
CHBrCL,
CHBr2CI
CHBr3
Total
0.88
0.13
0.11
0.19
1.3
0.61
. 0.11
ND
0.18
0.9
Effluent
(147mWs/cm2)
-
0.78
0.12
0.10
0.15
1.2
Aldehydes, ug/I - ' "
Formaldehyde,
Acetaldehyde
Heptaldehyde - • . -
Benzaldehyde
Glyoxal
Methyl glyoxal •
TOC, mg/l
UV absorbance
@254.nm, a.u./crh
Bromide mg/l
Bromate, mg/l
8- to 16-carbon hydrocarbons
, 3.54
5.94
ND
ND
2.55
1.25
8.27
0.173
0.11
<0.005
5.90
7.29
- ND
ND
2.73
1.26
8.60
0.165
0.11
<0.005
9.62
8.34
ND
ND
3.44
1.56
8.61
0.165
0.10
<0.005
2 log reduction was observed due to ultraviolet light treatment
Detection limits are 0.1 ug/I for trihalomethanes and 1 ug/I for aldehydes
As can be seen from the exhibit, some increase in formaldehyde, glyoxal, and acetyldehyde compounds
occurred, with formaldehyde concentration almost tripling at a dose of 147 mWs/cm2., Another
UV Light Disinfection Technology in
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Chapter 2—Assessment of Ultraviolet Light Efficacy, Viability, and Operational Factors
observation is that some trihalomethanes removal occurred at 45 mWs/cm2 and at 147 mWs/cm2.
Formaldehyde is aBl carcinogen i.e. probable human carcinogen with limited evidence in epidemiological
carcinogenicity studies (based on inhalation exposure). The health advisory for the contaminant
formaldehyde is 1 mg/L for a lifetime exposure for a 75 kg adult, and 20 mg/L for long-term exposure.
For a 10-kg child, the longer-term health advisory for formaldehyde is 5 mg/L (USEPA, 1996). Therefore,
the increases are insignificant and do not pose any known health risks. Moreover, it is unlikely to find
formaldehyde in drinking water sources. (USEPA, 1996). There are no health advisories for acetyldehyde
and glyoxal (USEPA, 1996).
In a comparative study of highly concentrated effluents from nine wastewater treatment plants, Jolley et al.
(1982) determined that the chemical effects of ultraviolet irradiation at 60 mWs/cm2 were relatively slight,
with the elimination of mutagenic constituents in one effluent. '
As stated earlier, Oppenheimer et al. (1993) conducted a study on by-products formation in reclaimed
water in California. Compared to chlorination, ultraviolet light has minimal by-products formation and
some contaminants removal effect. Exhibit 2-28 shows that ultraviolet light either reduced or slightly.
increased the concentrations of some trihalomethane compounds.
Exhibit 2-28. Disinfection By-Products Found in Chlorinated and UV-lrradiated EVMWD
Tertiary Effluent (Oppenheimer et al., 1993)
Compounds Detected
4-methyl-2-pentanone
Chloroform
Dichlorobromomethane
Dibromochloromethane
Methyl Bromide
Bromoform
Before Disinfection
(H9/I)
5.4
2.7
0.9
1.1
2.8
<0.5
Chlorine" (iig/l)
5.9
21
22
<1.0
<1.0
3.1
uVftig/l)
4.5
2.9
1.0
0.8
<1.0 ,
<0.5
4 Chlorine = 9.8 mg/l dose and 2-hour contact time
" UV = 300 mWs/cm2
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Chapter 2-Assessment of Ultraviolet Light Efficacy, Viability, and Operational Factors
2.4.1.2 Effects of Ultraviolet Light Treatment on Assimilable Organic Carbon
Assimilable Organic Carbon (AOC)2 compounds are best described as ready-to-eat substrate for
microorganisms. Therefore, the presence of AOC in drinking water may result in rapid increases in the
microorganism population in the distribution system. The relationship between the growth of coliform
bacteria and AOC in finished water is well documented (USEPA, 1992a). The effects of AOC in treated
drinking water can be seen in biofilm growth in distribution systems and in episodes of high levels of
coliform and nuisance bacteria in distribution systems. The following paragraph presents a preliminary
literature review of the findings on the issue of AOC formation in ultraviolet-disinfected water.
The effects of ultraviolet light on the AOC of Pseudomonosfluorescens strain P 17 (AOC P 17) have been
reported in an American Water Works Association-Research Foundation (AWWARF) publication. At low
intensities of ultraviolet light sufficient to cause 1 to 2 log reduction of colony counts on a nutrient-poor
nonselective medium, small increases of the AOC P 17 concentrations were observed (AWWARF, 1988)
as shown in Exhibit 2-29. The literature search did not find any more recent studies on the effects of
ultraviolet light at higher doses on AOC formation. Evidently, extrapolation from these limited data may
not be reliable. However, these data remain significant for assessing any future research needs in the area
of ultraviolet light effect on drinking water quality.
Exhibit 2-29. Effects of Ultraviolet Radiation on AOC Concentration (AWWARF, 1988)
Log Reduction3 of
Colony Count
1.2
2.0
1.9
0.0
1-2
0.76
0.71
1.25
0.77
AOC (P 17)" ngr ac-Ce eq/l
Before UV
2.0
2.0
4.4
1.7
1.6
3.7
3.6-
4.3
4.4
After UV
2.8
2.8
7.0
1.9
1.6
4.5
3.9
4.4
5.4
Colony counts (CFU/ml) streak plate method on diluted peptone meat extract agar incubated at 25°C for 10
days. ; '
Average values of duplicate measurements.
cac-C—acetate carbon.
2AOC = Assimilable Organic Carbon. Carbon in organic compounds that are easily biodegradable by a specified
microorganism. These compounds •include proteins, peptides, amino acids, carbohydrates, carboxylic acids, and other
compounds that are components of the living biomass.
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Chapter 2—Assessment of Ultraviolet Light Efficacy. Viability, and Operational Factors
2.4.1.3 Effects on Nitrite Formation
Groocock (1984) of the Derwent Division of the Severn-Trent Water Authority in the United Kingdom
reported an average of about 1 percent conversion of nitrate to nitrite (as N) occurring with two ultraviolet
light units used in the Derwent Division of the Severn-Trent Water Authority. The early experiences with
ultraviolet light use in drinking water suggest that there can be some conversion of organic nitrogen and
nitrate to nitrite due to the effect of radiation.of below 240 nm. Groocock (1984) suggested the use of
lamp envelopes made from materials that absorb wavelengths below 240 nm (such as Vycor from
Corning) in cases of high nitrite production. However, these envelopes have a higher rate of solarizatioh
(thus preventing light from passing through) than the common envelopes and therefore a shorter effective '
lamp life.
*
In a more recent research, von Sonntag and Schuchmann (1992) concluded that by-product formation is
of minor importance and significance. The researchers discussed as an example the formation of nitrites
from nitrates caused by ultraviolet application at doses used to disinfect water. However, the researchers
did not provide any data or citations to support the given example. ,
2.4.1.4 Effects on Mutagenicity Before and After Ultraviolet Light Application to River
Water .
Zoeteman et al. (1982) studied the mutagenic activity associated with by-products formed by drinking
water from the Rhine River disinfection with chlorine, chlorine dioxide, ozone, and ultraviolet light at a
dose of 120 mWs/cm2. The study showed that ultraviolet light application does not affect the mutagenicity
level of Rhine River water. Prior to 1982, most of The Netherlands' drinking water was not chlorinated.
Even part of the drinking water derived from polluted surface waters was distributed without chlorination
when bank filtration was applied (Zoeteman et al., 1982). The study by Zoeteman et al. (1982) shows
that few compounds are formed and that some destruction of compounds occurs by ultraviolet irradiation.
The study showed that some unidentified compounds were formed by ultraviolet irradiation and that a
known carcinogen, benzene, was detected at a level, of 1 ug/1. There were no more recent studies that
confirmed the Zoeteman et al. finding of benzene formation in ultraviolet treated drinking water.
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Chapter 2—Assessment of Ultraviolet Light Efficacy, Viability, and Operational Factors
2.4.2 The Phenomena of Photoreactivation, Dark Reactivation, and Chemical
Reactivation. .
Ultraviolet radiation causes damage to nucleic acids. This damage is not always permanent. Exposure
of some damaged microorganisms to visible light (400 to 750 nm) reverses the damage, provided that the
exppsure to the visible light occurs shortly after the exposure to ultraviolet light (Gaudy and Gaudy, 1980;
Salle, 1973). This is known as photoreactivation. Also, exposure to visible light before exposure to
ultraviolet light for inactivation reduces the damage in some microorganisms. Environmental factors such
as temperature and pH are. also important in the process of reactivation. The reactivation phenomena
associated with the use of ultraviolet light for wastewater disinfection may imply, to some extent, that the
inactivation is temporary and hence not an appropriate technology for drinking water disinfection.
Therefore, it is important to present the issues surrounding microorganism reactivation mechanisms and
the research conducted to investigate this phenomena.
The key to the reactivation process in irradiated microorganisms is the presence of repair enzymes in the
cell. The speed at which a microorganism can recover depends on the growth mechanisms. Spores and
slow-growing microorganisms are less affected by ultraviolet light than fast-growing microorganisms. In
a fast-growing microorganism, the original DNA in a rapidly replicating active cell is lost to the changes
caused by ultraviolet light before any repair activity could start. When the cell is no longer exposed to
ultraviolet radiation (at 254 nm wavelength), excited P/.(jc) electrons in not fully damaged DNA strands
in slow-growing microorganisms will return to a lower energy state. Under favorable conditions, the
microorganism will repair the damaged sections using the cell's enzymes and resume replication activities.
A detailed explanation of the physical action of ultraviolet light on chemical bonds is presented in -
Appendix B.
Viruses do not have repairenzymes, and thus, theoretically, their inactivation is easier than the inactivation
of bacteria or protozoa. However, if a.virus is living as a parasite in a bacteria or protozoa, then the
viability of the virus, is subject to the reactivation of the host cell. In other words, if the host cell
reactivates, then viruses protected by the host cell will resume their activities as soon as the host cell
reactivates. The same principle applies to infectious bacteria inside a protozoa, such as Acanthamoebae
spp. or Cryptosporidium spp., where, upon photo or chemical reactivation, the parasites may become a
source of bacterial contamination _(King et al., 1988).
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Chapter 2—Assessment of Ultraviolet Light Efficacy, Viability, and Operational Factors
The problems associated with photo reactivation and dark repair mechanisms have been studied since 1948
(Witherell, Solomon, and Stone, 1979). It has been shown that microorganisms that are not fully
destroyed by ultraviolet light could be revived by exposure to long wavelength light (visible light of
wavelength between 400 nm and 750 nm). The degree of reactivation in visible light is a function of
temperature, pH, and time and intensity of the exposure to visible light (Lamanna and Mallette, 1965).
The longer the irradiated cells are kept in the dark, the fewer the number of cells reactivated in visible
light The degree of recovery possible is dependent on ultraviolet light dose. The greater the dose, the
smaller the population of the cells that reactivate. Temperature effect was observed in the
photoreactivation process. The warmer the cells during exposure to visible light, the greater the proportion
of reactivated cells [up to a temperature of 45°C to 50°C (113°F to 122°F)] (Salle, 4 973). Exhibit 2-30
shows the difference in the surviving fraction in four microbial species. As can be seen from Exhibit
2-30, the difference in the surviving fraction (in this experiment of Kelner, 1949) of dark-kept arid light-
kept irradiated cells ranges from 2 logs to 5 logs.
Exhibit 2-30. Surviving Fraction in Four Microbial Species After Ultraviolet Irradiation
Dark survival3
Light survival"
S. griseus
2.1 x10'6
6.6x1 0-1
E.coli
4,5x1 0'6
i:2xicr1
P. notatum
5.5x1 O^4
2.5x1 0'1 '
S. cerevisiae
1.px1Q-5
I.OxlO"3-
'Surviving cells kept in dark after exposure to ultraviolet light.
"Surviving cells after illumination with long wavelength light following exposure to ultraviolet light.
Source: Kelner, 1949, as cited in Lamanna and Mallette, 1965.
Cells irradiated by ultraviolet light may be reactivated by chemical means. The chemical reactivation
phenomenon and the importance of the type of culture and media in which the microorganisms are
irradiated have been observed since 1927. Bedford (1927) (as reported in Salle, 1973) irradiated growth
media and discovered the formation of hydrogen peroxide. This discovery is important because it .means
that the ultraviolet light dose inactivation rate relationship in a growth medium that produces hydrogen
peroxide as a by-product cannot be used for design purposes in drinking water application. Wyss et al.
(1948) (as reported in Salle [1973]) found that the addition of enzyme catalase would negate the effects
of hydrogen peroxide formed by irradiation. Addition of compounds such as nicotinamide-adenuie
dinucleotide (NAD) and coenzyme A as well as pH adjustment can counter the effect 'of ultraviolet light
irradiation. For example, reducing the pH from 8 to 5 within 2 hours after irradiation increased the
number of survivors producing colonies of Escherichia coli by as much as 1 x 103 (Weatherwax, 1956,
as cited in Salle, 1973). , .
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Chapter 2—Assessment of Ultraviolet Light Efficacy, Viability, and Operational Factors
- ' - j • • -a. . i """ . ^^^^^™"^^™""*"^"'*1"^^™""«"^^""^—«^^^^«^^—i^^^»«»
Groocock (1984) discussed the issue of reactivation and repair mechanisms of microorganisms treated with
ultraviolet irradiation. One of these repair mechanisms (photorepair) is encouraged by exposure within
2 to 3 hours of ultraviolet treatment to higher wavelength radiation, notably above 300 nm, i.e., in the
ultraviolet long wavelength band/visible bands. This would appear to be largely due to reversal of the
dimerization of pyrimidines (chiefly thymidirie) caused by irradiation. "Dark repair", mechanisms,
however, exist—particularly where only one strand of the double link has been affected. Enzyme action
snips out the damaged length and then uses the remaining undamaged strand as a template in the
reconstruction. Groocock (1984) argued .that it would seem likely that the nucleic acids need to be
damaged in more than one place (i.e., more than one photon strike) to ensure permanent inactivation.
Therefore, a dose threshold will probably be reached before this happens to any great extent. Ellis (1991)
cited Angehrn and Trager in their disbelief that reactivation and repair mechanisms are possible under
operational drinking water conditions. Ellis (1991) cited Angehrn and Trager in reporting that no cases
of reinfection resulting from photprepair mechanisms have been proved in effectively treated drinking
water.
-The experience gained from using ultraviolet light to disinfect wastewater shows that photoreactivatiog
is seasonally influenced. During the summer season (because of less cloud cover, because the northern
hemisphere is directly facing the sun, and because of longer daylight time and higher cell temperature),
a maximum repair of :i to 2.5 log increase in total coliforms, fecal coliforms, and Escherichia coli has
been observed in ultraviolet-treated wastewater (USEPA, 1992b). Whitby and Palmateer (1993) conducted
experiments to test the significance of photpreactivation in ultraviolet-treated wastewater. The researchers
used labeled Escherichia coli in their experiment. -After ultraviolet treatment, the photoreactivated labeled
Escherichia coli were detected in glass bottles but not in the receiving stream. The researchers concluded
that in the natural environment, photoreactivation is not an important issue. Under operational wastewater
conditions, microorganisms receiving insufficient ultraviolet dose (because of shielding as well as other
wastewater quality factors) may reactivate. The insufficiently ultraviolet-hit cells exhibit the state known
,as biostatic activity. As stated earlier, biostatic activity is a term that indicates inhibited metabolism.
Some of these cells do reactivate as they come hi contact with visible light as soon as they leave the '
ultraviolet realtor, and as stated earlier, the faster the cells are put in a favorable environment the more
likely that they will recover. Under operational ground drinking water conditions, with sufficient
ultraviolet dose, it is very doubtful that many cells will be in the biostatic state. It is very doubtful that
cells in the biostatic state will be able to reactivate as soon as water is drawn from use from the faucets
because there is some residence time spent in the dark closed distribution system.
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Chapter 2—Assessment of Ultraviolet Light Efficacy, Viability, and Operational Factors
The reactivation of microorganisms that have been subject to disinfection is not unique to the process of
ultraviolet light disinfection. Because disinfection as a process is not sterilization, microorganisms injured
by chemical disinfection and not completely destroyed can revive (as microorganisms disinfected with
ultraviolet light do) under favorable conditions. At insufficient-to-kill chemical disinfectant concentrations,
the disinfectant may cause the microorganisms .to go into a state known as biostatic activity. In a. biostatic
state, metabolism is inhibited and that sets the microorganisms on a course that with time leads to death.
The effect of the insufficient-to-kill chemical concentration could be reversed if the microorganisms were
placed in a more favorable environment. At concentrations lower than the concentrations sufficient to
trigger the biostatic state in microorganisms, no inactivation effect of any kind may be exhibited, and with
various disinfectants or microbial poisons a very small concentration may stimulate growth (Gaudy and
Gaudy, 1981). The problems associated with reactivated microorganisms range from biofilm growth in
drinking water distribution systems (USEPA, 1992a) to sicknesses that often go unreported as water-related
(USEPA, 1984).
To nunirnizephotoreactivation of microorganisms in ultraviolet treated drinking water, if proved to happen
under operational conditions, four possible approaches that need further investigation may be followed:
1. Provide ample disinfection arid attenuation time (residence time in the ultraviolet reactor by
reducing the flow rate, adding another in-series ultraviolet unit, or providing a closed
reservoir immediately after the ultraviolet unit). This additional attenuation timemight not
exceed few to tens of seconds, but is crucial for inflictirig greater damage on the genetic
material of slow-growing microorganisms.
2. Increase the intensity and/or use a shorter wavelength emitting lamp (185 nm) along with
the standard 254 nm emitting lamp (combine a low-pressure mercury lamp with a medium-
pressure mercury lamp) to provide a broader range of germicidal wavelengths that include
ozone, peroxides, and free radicals producing wavelengths.
3. In extreme cases use ozone or hydrogen peroxide or both for disinfection prior to ultraviolet
to increase the disinfection power of the reactor, particularly when high levels of organic
compounds or assimilable organic compounds are present, and follow that by a GAC filter
to eliminate any residual by-products.
4. Find the most appropriate disinfection wavelength for specific recalcitrant microorganisms
and use the custom manufactured lamp that emits it, in addition to the low-pressure mercury
lamp.
2.4.3 Ultraviolet Light and Residual Disinfection
Groocock (1984) noted, from the experience of the Severn-Trent Water Authority in the United Kingdom,
, that a small amount of ozone is produced by radiation at wavelengths below 200 nm, thus giving a slight
UV Light Disinfection Technology in
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Chapter 2— Assessment of Ultraviolet Light Efficacy, Viability, and Operational Factors
.enhancement and prolongment of the germicidal action. In a 20-month pilot plant study, Lund and
Ormerod, 1995, found that ultraviolet treatment had an inhibitory effect on biofilm formation. The
inhibition effect of ultraviolet light is thought to be the 'result of hydrogen peroxide and/or other oxygen-
containing free radicals produced by irradiation. Gjessing and Kallqvist (1991), as cited in Lund and
Hongve, 1994, reported the inhibition of Selenastrum capricornutum alga growth in ultraviolet irradiated
water that lasted for several weeks. It is known that free radicals and oxygen species formed during
ultraviolet are very reactive and snort lived, but H2O2, one of the known ultraviolet irradiation by-products,
has a half-life in water ranging from 1 to 8 hours in natural water and more than 80 hours under sterile
conditions i.e. H^ half-life is water quality dependant. (Cooper and Zepp, 1990 as cited in Lund and
Hongve, 1994).
Lund and Ormerod, 1995, investigated the effects of chlorination, ultraviolet light treatment and ozonation
on biofilm formation in water distribution systems. The ozonated test water received an ozone dose of
1.8 ± 0.4 mg/L. The ultraviolet irradiated water received a 42 mWs/cm2 dose. The chlorinated water
maintained a free residual chlorine level of at least 0.05 mg/L after a 30 minutes contact time. The control
test water did not receive any treatment other than straining. The average values of the physicochemical .
properties of tested water at the Baeram water treatment plant near Oslo, Norway are presented in Exhibit
2-31. Exhibit 2-31 includes the number of samples taken during the 20-month pilot study.
Exhibit 2-31. Baerum Average Water Quality Parameters (Lund and Ormerod, 1995)
Parameter
Turbidity (NTU)
pH
Color (mg Pt/L)
DOCa (mg C/L
Feb(ug/L)
Mn(ug/L)
Total N (mg N/L)
Total P (u,g P/L)
Number of Samples
146
95
94
24
40
36
15
14
Mean Value
0.4
6.4
35
4.6
128
36
0.34
4
Standard Deviation
0.06
0.16
5.2
0.76
23.5
7.6
0.05 r
0.8
aNo pronounced seasonal variation
"Maximum values in August 1988 and August 1989
All raw water used in the experiments of Lund and Ormerod, 1995 was strained with a 35 um mesh size.
The raw water pipe was forked into four laterals, one for control and one for each of the three disinfection
treatments. After the application of treatment at the head of each lateral pipe, the waters were pumped
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Chapter 2—Assessment of Ultraviolet Light Efficacy, Viability, and Operational Factors
at a flow rate of 0.20 to 0.25 I/s into 2.6m pipes of 20.4 mm inner diameter. The lateral pipes used in
the experiment were high density polyethylene (HDPE) pipes. Each of the four lateral pipes had pieces
of mica held inside the HDPE pipe by a fitted-in poly vinyl chloride (PVC) pipe. The pieces of mica were
held in a position parallel to the flow of the tested water. Water samples were withdrawn on a monthly
basis for measuring Biochemical Oxygen Demand (BOD), ultraviolet absorbance, and Dissolved Organic
Carbon (DOC) content. •
Forqualitative'characterization of thebiofilms formed, Lund and Ormerod, 1995 examined the mica pieces
using an electron microscope. The microscopic inspection of the mica pieces showed that mica from
chlorinated water was colonized by rod-shaped bacteria assembled in star-shaped colonies. The mica from
the other three systems (control, ultraviolet treatment and ozone treatment) were colonized by rod-shaped
and budding bacteria. Extracellular polymer substances were not evident in the chlorinated system but
were evident in the other three systems (forming networks on the mica surface) most in the ozonated
system and least in the ultraviolet irradiated system.
The BOD test results showed that ozonated water had the highest BOD level (10% higher than the control
BOD level) which indicated an increase in the content assimilable organic carbon. Ultraviolet irradiated
water showed 70 percent less BOD than the control.
Lund and Ormerod, 1995, noted that biofilm formation started early in the experiment, but amounts of
sludge, measured as dry weight, were hot produced until the water temperature started to rise above 5°C
in May.
Exhibit 2-32 presents seasonal accumulation of biofilm measured as dry weight. The biofilm formed in
ultraviolet irradiated water was similar, but not identical, to the "biofilm found in the control system.
;
Lund and Ormerod, 1995, concluded that prevention of biofilm formation in distribution systems is best
done by removing as much as possible for the organic material (mean value of DOC in the treated water
was 4.6 mg/L) from the source water and maintaining a low free chlorine residual in the distribution
system.
To summarize, the test results of the 20-month pilot study by Lund and Ormerod showed that no biofilm
formed in the pipes carrying chlorinated water. It also showed that the highest biofilm formation occurred
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Chapter 2—Assessment of Ultraviolet Light Efficacy, Viability, and Operational Factors
Exhibit 2-32. Seasonal Accumulation of Biofilm, Measured as Dry Weight in the
Different Pipe Systems and Seasonal Variations in Raw Water Temperature
. (Lund and Ormerod, 1995)
a .
FMAM J-J AS OND J FMAM J JASON
JFMAMJ J AS OND J F.M.AM J J A S O N;
1988 1989
* Microstrained system
o Onzonated system
4 Ultraviolet irradiated system
D Chlorinated system
Periods with stagnant water
in pipe systems
in the pipes carrying ozonated water followed by control water. The pilot study also showed that
ultraviolet-treated water formed considerably less biofilm production than the control water.
Lund and Hongve (1994) investigated the phenomena of bactericidal effect of ultraviolet-irradiated water. '•
To confirm that ultraviolet treatment yield a durable bacterial growth inhibitory effect, Lund and Hongve,
1994, conducted a series of experiments aimed at determining the duration of that inhibitory effect and
aimed at determining the residual bactericidal effect of ultraviolet treatment. The researchers used water
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Chapter 2—Assessment of Ultraviolet Light Efficacy, Viability, and Operational Factors
from Bserum waterworks near Oslo (Exhibit 2-33) and irradiated separate volumes with 42 mWs/cm2 and
96 mWs/cm2. Heterotrophic bacteria inoculum was added to the ultraviolet treated water. Water samples
were drawn after one minute and 60 minutes of inoculation for enumeration of surviving bacteria. The
test results show that 7 days after ultraviolet irradiation, heterotrophic bacterial growth was inhibited.
Exhibit 2-34 presents the test results as reported in Lund and Hongve (1994). The researchers found that
approximately 60 percent of the heterotrophic bacteria inoculum in the water samples from the pilot plant
near Oslo, Norway, were inactivated within 1 hour of contact time with ultraviolet disinfected drinking
water. . *
Exhibit 2-33. Baerum Water Quality Parameters (Lund and Hongve, 1994)
Parameter
DOC (mg/0
UVjj* absorbance (per cm)
Color (mg Pt/l) =
PH .
Fe (mg/l)
Ca (mg/l)
Mn (mg/l)
Alkalinity (mmol/l)
Conductivity @25°-C (mS/m)
Level
3.9
0.17
30
6.4
0.01
• 3
: 0.35 ,
0.05
' 2.7
Exhibit 2-34. Demonstration of Long-Term Inhibitory Effect in U.V.-lrradiated Water
Compared to Raw Water, After Addition to Heterotrophic Bacteria
(Lund and Hongve, 1994)
Storage Time of
U.V. Irradiated
Test Water at
4*C (days)
0
0
7
7
14
14
Contact Time
Between
Bacteria and
Test Water
(min)
1
60 .
1
60
1
60
Bacterial Counts (CPU/nil)
95% Conf. Intervals*
Normal U.V.
Dose
430±87a .
540±85m
4,056 ± 232"
2,570 ± 185"
overgrown
overgrown
High U.V. Dose
440 ±67
463 ± 79
4,'920±314
4,035 ± 284
overgrown
overgrown
Reduction in Bacterial
Concentration
Normal U.V.
Dose
42mWs/cm2
66%
57%
22%
51%
0%
0%
High U.V. Dose
96 mWs/cm2
, 65%
63%
5%
22%
0%
0%
* Poisson distribution model.
* Initial cone, was 1,250 £ 105 CFU/ml.
" Initial cone, was 5;200 ± 100 CFU/m!.
UV Light Disinfection Technology in
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Chapter 2-Assessment of Ultraviolet Light Efficacy. Viability, and Operational Factors
Over a period of 7 days, the growth curves for heterotrophic bacteria in inoculated control raw water and
irradiated water samples, show an exponential growth after the first day of inoculation. The growth rate
for control samples is significantly higher than the growth rate in irradiated water. The growth rate in
control samples are double the rates of treated water samples. The water samples were stored in the dark
at 4°C. The difference in results between the42 mWs/cm2 irradiated water and the 96,mWs/cm2 irradiated
water is statistically insignificant (Lund and Hongve, 1994).
Also Lund and Hongve, 1994, conducted tracer studies to measure metabolic inhibition and replication
inhibition of microorganisms in ultraviolet irradiated humic water. The researchers used 3H-labelled
thymidine and leucine as a tool to quantify cell growth and replication in ultraviolet-irradiated water.
Leucine is knowii to be incorporated in the DNA of active bacteria during protein synthesis and thymidine
is known to be incorporated in the DNA when the cell is multiplying. The uptake of leucine and thymidine
by a microorganism is dependent on the presence of biodegradable organic substances: The physico-
chemical properties of the humic water used in the tracer studies are presented in Exhibit 2-35^
Exhibit 2-35. Water Quality Parameters of the Basrum water used in Tracer Experiments
(Lund and Hongve, 1994)
Parameter
Level
DOC (mg/l)
7.8
UVg54 absorbance (per cm)
0.30
Color (mg Pt/l)
60
PH
7.4
Fe (mg/l)
0.5
Ca (mg/l)
Mn (mg/l)
0.08
Alkalinity (mmol/l)
0.3
Conductivity @25°C (mS/m)
2.7
The tracer experiments were conducted on 0.2um filtered control water. In addition to the control samples,
the water samples were either preheated to 70°C or irradiated with an ultraviolet dose of 240 mWs/cm2.
Exhibit 2-36 shows bacterial uptake of 3H-labeled leucine in treated and control water samples. The
uptake rates of Leucine in irradiated water compared to the uptake rates in control water show that
ultraviolet light has an inhibitory effect on bacterial growth.
Experiments on microorganisms uptake of 3H-labelled thymidine in ultraviolet irradiated water and control
of water samples during 24 hours were conducted with various volumes of added inoculum. Exhibit 2-37
UV Light Disinfection Technology in
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Final—September 1996
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Chapter 2—Assessment of Ultraviolet Light Efficacy, Viability, and Operational Factors
Exhibit 2-36. Bacterial Uptake of 3H-Labelled Leucine in Water Samples with Identical
Inoculation Volumes (Lund and Hongve, 1994)*
4 i—
55. 3
u
CO
W
CO
H.
D
A
A
a
a
A
A
d?
-H-
50
100
ISO
Minutes
+ Ultraviolet irradiated water samples (240 mWs/cm2)
* Heated water samples (70°C)
n Sterile filtered water samples (0.2 um) '
* Inoculants were prepared using 100 times the concentration of a chemically treated sewage effluent.
presents thymidine uptake test results. As can be seen from Exhibit 2-37, a near constant 3H-labelled
thymidine uptake levels for the control samples -are attained. Lund and Hongve, 1994, attributed this
uptake inhibition, i.e., cell reproduction inhibition, to a micronutrient limitation. Exhibit 2-37 shows that
3H-labelIed thymidine uptake levels-in ultraviolet irradiated water samples are consistently lower than the
uptake levels in all the control water samples. ' /
Lund and Hongve noted that ultraviolet irradiation alone may inhibit biofilm formation in new and clean
distribution systems and may prevent adherence of organic matter on the walls of pipes in short
distribution systems. However, Lund and Hongve 1994 cautioned that the inhibitory effect of ultraviolet
irradiated water may be very limited in distribution systems with well established biofilm or water high
in biodegradable organic substances.
UV Light Disinfection Technology in
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Chapters-Assessment of Ultraviolet Light Efficacy, Viability, and Operational Factors
Exhibit 2-37. Bacterial Uptake of 3H-Labelled Thymidine During 24 Hours in Ultraviolet-
Irradiated and Untreated Control Samples for Various Volumes of Inocular Added
• • (Lund jand Hongve, 1994)*
15 r—
u
o
to
>S
O
.«
0.
10 -
5 -
| 1 u.v.-irradiated water
R53 Raw water
BJ
0.2
0.6 1.8 ., 5.1
Inoculum, % of total volume
14
* The inoculated suspension was prepared using 100 times the concentration of particulate organic
matter extracted from the same water.
As stated earlier, ultraviolet radiation produces hydrogen peroxide in irradiated water. Lund and Hongve,
1994, believe that the residual disinfectant effect in ultraviolet-irradiated waters is due to hydroxyl radicals
produced as a by-product of hydrogen peroxide reaction with reduced compounds such as ferrous iron in
humic compounds. Lund and Hongve, 1994, allude, to the fact that oxygen species radicals produced in
some disinfection processes such as ozonation, can give rise .to more biodegradable substances and hence
surmised that ultraviolet irradiation may to some degree enhance bacterial growth in humic water.
2.4.4 The Search for a Surrogate
Because traditional surrogate microorganisms (e.g., total coliform) are sensitive to ultraviolet light, and
because it is not economically feasible to test every target pathogenic microorganism, an appropriate
surrogate microorganism is needed to quantify the correlation of its inactivation rates to that of
microorganisms of interest, such as reoviras, rotavirus, or Hepatitis A virus (HAV). Therefore, the
viability of ultraviolet technology depends to a certain extent on the identification of a surrogate
microorganism that is suitable and reliable in quantifying ultraviolet efficacy against pathogenic micro-
organisms commonly found in ground water sources.
UV Light Disinfection Technology in
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Chapter 2—Assessment of Ultraviolet Light Efficacy. Viability, and Operational.Factors
Wilson et al. (1993) proposed the use of coliphage
MS-2 as a challenge surrogate microorganism to
test the efficacy of ultraviolet light. The main
reason for his proposal is the similar reaction to
chemical and ultraviolet treatment exhibited by
MS-2 and members of the genus enteroviruses that
includes polioviruses, Norwalk, and Coxsackie
virus. Wilson et al. (1993) compared the ultra-
violet inactivation results of, MS-2 to those of a
variety of waterborne pathogens (see Exhibits 2-10
and 2-11). The work of Wilson et al. (1993) shows
that a 99.5 percent inactivation (2.3 log reduction)
at 39.4 mWs/cm2 of MS-2 using ultraviolet light is
equivalent or greater than 6 log reduction of
Klebsiella Terrigena, vibrio cholerae, Salmonella
typhi, Escherichia coli 0157:H7, Shigella
dysenteriae, Yersinia enterocolitica, Campylobacter
jejuni, Aeromonas. hydrophila, and Legionella
pneumophila. For the same (2.3 log) reduction in
MS-2, using ultraviolet light, a 4 log reduction was
obtained in HAV, rotavirus SA-11, and poliovirus
type 1. In this study, Wilson et al. (1993)
concluded that a minimum of 6 log reduction in all
of the above-mentioned pathogenic bacteria could
be achieved using an ultraviolet light dose of 15.6
mWs/cm2 and that a 39.4 mWs/cm2 minimum
ultraviolet dose was necessary to achieve a
Surrogates: An "EPA Perspective
Many problems are associated with trying to detect
specific pathogens: Because of these problems,
bacteria that are not themselves pathogenic are
measured as surrogates for the more harmful
bacteria. The ideal indicator for drinking water
contamination is:
• Suitable for all types of drinking water
• Present in polluted water at higher concentrations
than harmful bacteria
„• Able to survive in water at least as long as
pathogens and is at least as resistant to
disinfection
• Easy and inexpensive to measure in drinking
water samples
• Generally not present unless harmful
contamination is also present.
(USEPA, 1992a)
minimum of 4 log reduction in the tested viruses.
Surrogates: A German Perspective
In Germany, drinking water is assumed to be
microbiologically acceptable when coliform bacteria
or E. coli are not detected in water samples.
Carlson (1991) suggested specific requirements for
microorganisms to be acceptable as surrogate
indicators for microbial contamination:
• The microorganisms must.be present in large
numbers.
• They must be easily and reliably detected with
routine methods.
• Their survival period should correspond at least
to that of the pathogenic organism in question.
The last requirement presents a problem because
some pathogens, like certain viruses, remain
infectious in the environment for longer periods than
bacteria. As presented by Carlson (1991), the
German view for selecting a surrogate vindicator
microorganism is very close to the USEPA
perspective on the subject, but not as specific as the
USEPA point of view: . ,
Exhibit 2-38 presents the bar graph inactivation
rates. The work of Wilson et al. (1993) may be
considered in the Agency's technical review for a
ground water disinfection requirement using ultraviolet light. However, it is worthwhile to consider that
UV Light Disinfection Technology in
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Final—September 1996
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Chapter 2-Assessment of Ultraviolet Light Efficacy. Viability, and Operational Factors
Exhibit 2-38. Extrapolated Inactivation Rates for Bacteria, Viruses, and Test
Surrogate Cbliphage MS-2 (Wilson et ai., 1993)
99.9999%
Inactivation* 99.99%
99.5%
so UV Dose
(mW sec/cm2)
022E-16
Inactivation rates extrapolated using linear regression model
the above-cited 6 log and 4 log reductions presented in the bar graph in Exhibit 2-38 were concluded by
extrapolation. To extrapolate and estimate ultraviolet'doses, Wilson et al. (1993) used a linear regression
analysis software (Statgraphics® Version 5.1,1991) to develop an MS-2 linear regression model (no tailing
factor is considered) based on the data presented in Exhibits 2-10 and 2-11. From the linear regression
model, ultraviolet light dose estimates with 95-percent confidence intervals were calculated using a one-
tailed t test. It is important also to note that all challenge microorganisms and the proposed surrogate
microorganism were tested in phosphate-buffered distilled water. Phosphate-buffered distilled water media
may have lower ultraviolet demand than does naturally occurring water. .In addition, naturally occurring
microorganisms are typically more resistant to disinfection than laboratory-cultured microorganisms.
Wilson et al. (1993) argued in favor of adopting coliphage MS-2 as a surrogate microorganism because
(1) it is more resistant to ultraviolet light than all the tested pathogenic bacteria and viruses; (2) it has
highly reproducible ultraviolet light inactivation results; (3) the cost is low; (4) high liters are easily
attainable; (5) it shows results within 6 hours; and (6) it is not pathogenic to humans. Moreover,
coliphage MS-2 requires 18 to 24 hours to culture.
UV Light Disinfection Technology in
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Chapter 2—Assessment of Ultraviolet Light Efficacy, Viability, and Operational Factors
Sommer and Cabaj (1993), realizing that lab-cultured microorganisms are more sensitive to disinfection,
proposed criteria for selecting a suitable surrogate microorganism. The microorganism that satisfies these
criteria would then be used to test the efficiency of ultraviolet light disinfection in drinking water. The
proposed criteria call for a microorganism with the following characteristics:
• A steady inactiva'tion over a wide dose
• A simple and sufficient culturability
• Nonpathogenic
• A temporal stability with regard to ultraviolet susceptibility.
Sommer and Cabaj (1993) proposed a specific cultural procedure (method C) for Bacillus subtilis spores
(ATCC6633) that satisfies the above criteria. The proposed cultural procedure (presented previously in
Exhibit 2-11) is not the same cultural procedure required under ANSI/NSF Standard 55-1991 for the same
c
challenge microorganism Bacillus subtilis spores and was selected after two other cultural procedures
failed to satisfy the proposed criteria (refer to Exhibit 2-11 for more details). Bacillus subtilis spores
require 3 days to culture (method C). The test results of its susceptibility to ultraviolet light are highly
reproducible.
2.4.4.1 ORP, a Non-Microbial Surrogate
Carlson (1991) addressed the issue of microbiological water examination in Germany. According to the
provisions of the Bundes-Seuchengesetz (Federal Communicable Disease Act), proving the existence of
bacterial pathogens requires special permission from the authorities. Moreover, it is a time-consuming
process, and it is impractical if not impossible for a public water system to get sampling test results before
the water is pumped into the distribution network or consumed. The fact that various pathogenic bacteria
actually lead to an outbreak after a long incubation period further complicates the issue of microbiological
examination of water. For example, the incubation period of HAV infection is 15 to 50 days depending.
on dose, with an average of 28-30 days. A 1- to 3-week incubation is needed to have typhoid fever
symptoms (APHA, 1981). If an operational error or system failure allowed the pathogens causing HAV
infection or typhoid fever to be waterbome through the distribution system to the consumer, it would take
at least 15 days before the first case of HAV infection would be reported and a minimum of 1 week
before the first case of typhoid fever would be reported. Thus, if water is examined for the pathogen
I
causing the typhoid fever.dt is more than likely that the microorganism will not be found because it would
have been flushed out of the system during the incubation period. Because of-the impracticality.of testing
UV Light Disinfection Technology in
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Chapter 2—Assessment of Ultraviolet Light Efficacy, Viability, and Operational Factors
all pathogens that might exist in drinking water, surrogate challenge and indicator microorganisms are used
to test disinfection efficiency. Still, testing for these surrogate microorganisms is time consuming,
requiring skills that might not be available in operators of small and remote water systems.
Because the Oxidation Reduction Potential (ORP)3 of the medium plays an important part in the
physiology and ecology of microorganisms, the metabolism of a microorganism and, consequently, its
ability to survive and propagate are influenced by the ORP of the medium in which it lives. The range
of the ORP at which bacteria can live is limited, with anaerobes propagating in medium to low levels and
aerobes in the low to high ORP levels. The inability of anaerobes and aerobes to survive at high ORP
levels can be explained by the fact that the SH groups (these are highly oxidizable groups that play an
important role in electron transfer mechanisms in microorganisms) or radicals-containing enzymes, within
the microorganism will be inactivated at high levels of ORP. For microorganisms, like all life forms
including humans, placing them in direct contact with an extreme environment will be detrimental.
Therefore, the elimination of microorganisms in drinking water can be achieved by high ORP, so that the
vital enzymes are blocked. Appendix B of this report describes how ultraviolet light is used to achieve
high levels of ORP in polluted drinking water sources. Carlson (1991) argued in favor of using ORP as
an indicator of disinfection efficiency. The researcher presented studies that correlate the killing rates of
pathogenic organisms to ORP levels. The studies .conducted by Carlson (1991) to determine ORP levels
at which chlorination would result in a satisfactory disinfection show that ORP levels above 700 mV
versus a saturated calomel electrode at pH 7 should be maintained for at least 10 to 30 seconds. If this
proves to be reliable, it will be easier to train water works operators on how to place an ORP probe in
, finished water and take a continuous reading than to take a water sample and to test for microbial presence
on an occasional basis.
2.4.5 Comparison of Ultraviolet Light to Chemical Disinfection
Because it is not economically feasible to require public water supply systems to test for every pathogenic
microorganism that might be present in drinking water, surrogate microorganisms are tested for and used
as indicators of microbial water quality and disinfection. 'Traditional indicator surrogate microorganisms
Oxidation is defined as the addition of oxygen tp a compound, the removal of a hydrogen, or the loss of a pair of
electrons (Gaudy & Gaudy, 1980). Reduction is the removal of oxygen from a compound, the addition of hydrogen, or
the addition of a pair of electrons. In an oxidation-reduction reaction, a potential is formed at'a submersed platinum
electrode by supplying and accepting electrons. This potential is measured by using an electronic voltmeter without
drawing current against a reference electrode (saturated calomel electrode or silver-silverchloride electrode). The difference
in potential between the reference electrode and the metal at which the oxidation and reduction reaction takes place is
referred to as the ORP. •'/,'•
UV Light Disinfection Technology in
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Chapter 2—Assessment of Ultraviolet Light .Efficacy, Viability, and Operational Factors
(e.g., total coliform, Escherichia coli microorganisms) are sensitive to ultraviolet light. Therefore, it would
be inappropriate to compare the inactivation rate of ultraviolet light and those of traditional chemical
disinfectants for those indicator surrogate microorganisms. Moreover, quantified comparison of chemical
doses (in mg/L) and ultraviolet light doses (in mWs/cm2) for specific microorganism inactivation rates
cannot be established at this point. However, when comparing chemical disinfection with ultraviolet light
disinfection, a few issues stand out:
• Cryptosporidium spp. is resistant to chemical disinfection and cannot be inactivated using
chlorine or ozone at doses normally used for drinking water disinfection (USEPA, 1993).
Therefore, for ground water contaminated with Cryptosporidium spp., chemical disinfection has
no advantage over-ultraviolet light.
• The 1991 Article 80 of the Uniform Fire Code (UFC) requires treatment systems to handle the
accidental release of chlorine gas, chlorine dioxide, or sodium chlorite, as well as provide
emergency power sufficient to operate chemical scrubbing equipment (WERF, 1995). These
new requirements may well double the costs of chlorination (gas type) systems in States that
require compliance with the UFC. .
• For small systems where space is not available, or where capital and construction experience
is not available, ultraviolet systems are useful in upgrading and retrofitting with minimal
construction work. An ultraviolet unit can disinfect 0.5 MOD in a 40 ft2 space (USEPA, 1983)
while a chlorination unit requires more than 1,000 ft2 space, assuming a 30-minute contact time
and a flow velocity of 0.1 ft/sec.
• Unlike chemical disinfection, there are no known risks associated with oversizing the unit and
there is no limit on the dose that could be applied. These qualities give ultraviolet light an
edge over chemical disinfection in water applications where disinfection by-products pose health
risks, and their production is sensitive to chemical dose.
• At proper dose applications, ultraviolet light systems are effective in destroying bacterial and
viral pathogens. • . .
Exhibit 2-39 compares the germicidal effects of ultraviolet light with chemical disinfectants (Yip and
Konasewich, 1972). Using fecal coliform log reduction as a yardstick to measure the number of yardstick
units required by chlorine, ozone, and ultraviolet light to achieve the same log reduction for a number of
pathogenic microorganisms, Yip and Konasewich (1972) showed that ultraviolet light is comparatively
more effective than chlorination and ozonation with about the same relative dose requirement for five
different pathogens other than Escherichia coli. However, another study by Chang et al. (1985) showed
that ultraviolet light is less effective.
Chang et al. (1985) address the issue of using coliforms as a valid indicator for disinfection efficiency
using ultraviolet light Based on the relative dose required to disinfect pathogenic organisms (see Exhibit
2-40), they concluded that the survival rate of coliform bacteria hi ultraviolet irradiated effluents does not
UV Light Disinfection Technology in .
Drinking Water Application—An Overview 2-64 Final—September 1996
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Chapter 2—Assessment of Ultraviolet Light Efficacy, Viability, and Operational Factors
Exhibit 2-39. Germicidal Effects oj Ultraviolet Light Versus Chemical Disinfectants in
Drinking Water Applications (Yip and Konasewich, 1972)
I
. *•
£4
!»
-L
•
o
uvao. a
III Tl
c
1
uv
1
0
•
c
...
uv
1
1
a
pj
u
V
UVCI
1
' .- * ? 4 5 ''•«.'
(1) EKberidila coll B C8) Salmonella fyphou
(9)Stapbjiococctuaaretu(4)Pollotypelvinu
CO CtaMdde AZ vinu («) Adenorlras lype S.
directly reflect the level of disinfection needed to disinfect the more resistant organisms. The ultraviolet
light resistances of viruses and Escherichia coli as reported by Chang et al. (1985) are not as comparable,
as implied by Yip and Konasewich (1972) (see Exhibit 2-39). The Yip and Konasewich 1972 study
showed a comparatively uniform ultraviolet light disinfection capability against a variety of pathogenic
microorganisms, while Chang et al. showed a nonuniform ultraviolet light disinfection capability. For
example, Kip, and Konasewich (1972) found that Escherichia coli and poliovirus require the same
ultraviolet dose to achieve the same log reduction. Chang et al. (1985) found that the poliovirus requires
more than three times the ultraviolet light dose-applied to Escherichia coli to achieve the same log
reduction. To compare ultraviolet resistance by various microorganisms, Chang et al. (1985) proposed
the use of standardized growth conditions of the tested microorganisms.
The advantages of using ultraviolet light rather than chemical disinfection are the following:
• No known toxic or significant nontoxic by-products.
• No danger of overdosing.
• Some removal of organic contaminants.
• If used for volatile organic compound (VOC) destruction, no VOC emissions or toxic air
emissions result (WWEMAj 1990). •
• No onsite smell and no final water product smell.
UV Light Disinfection Technology in
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Chapter 2—Assessment of Ultraviolet Light Efficacy. Viability, and Operational Factors
Exhibit 2-40. Relative Ultraviolet Light Dose for Some Microorganisms
(Chang et al., 1985)
2
MICROORGANIS
A. eattttanS cyus
.
.... . t A saHK/i* ffntf*
| Standard plate eoynt
mm^f^fj ^^m coBwcwt
• \EtcJ*f*MocoU
,^^^J SrtlfftjfO 3QOft9f
~~~\Se*9on99G tyffif
i t i 11 i i
2 4 68 IO 12 14 16
DOSAGE RELATIVE TO El coti = 1
• Very little residence time (seconds versus minutes for chemical disinfection).
• No storage of hazardous material required.
• Minimal space required for equipment and contact chamber.
• Taste is "not- negatively altered, only improved, with the destruction of some organic
contaminants and nuisance microorganisms.
• Minerals in water are not affected. -
• No mutagenicity effect using the Ames test.
• No or little (disposal of spent lamps or obsolete equipment) impact on the environment.
The main disadvantage of using ultraviolet light for disinfection is that no long-term residual disinfection
is provided, Exhibit 2-41 presents a quick comparison between ultraviolet light and common chemical
processes.
2.5 FINDINGS
Ultraviolet light of sufficient intensity and exposure is an excellent disinfecting agent for drinking water.
However, because of its limited penetration power at 254 nm, microorganisms that are covered with
protective membranes or are parasites in other microorganisms are less affected by the ultraviolet light
intensity and time of exposure needed to kill exposed microorganisms. Ultraviolet light is suitable to
disinfect clear water at intensities and times of exposure that are feasible to accomplish disinfection rates
UV Ught Disinfection Technology in
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Chapter 2-Assessment of Ultraviolet Light Efficacy, Viability, and Operational Factors
Exhibit 2-41. Ultraviolet Light Versus Chlorination and Ozonation in Drinking Water
Parameter
Tannins, Humus,
Dissolved Organics, and
Colloidal Material
Iron and Magnesium
Suspended Solids
(Turbidity)
pH Effect
Temperature Effect
Mutagenicity
Time Required to
Inactivate Microorganisms
Limits of Solubility at
Normal Temperatures
Microorganism Inactivation
By-Product Formation
Hazardous Material
Storage Requirement
Chlorine
Increased
Demand
Increased
.Demand
Increased
Demand
Varies
Yes
Yes
Minutes
Varies
. Effective
Yes
Yes
Ozone
Increased
Demand
Increased
Demand
Increased
Demand
Little
Yes
Unknown
Minutes
Yes
Effective
Yes
No „
UV
Increased
Demand
Increased
Demand
Increased
Demand
None
No
No
Seconds
N/A
Effective
No
No
Remarks
Increased harmful by-products for both
chlorine and ozone. Some contaminants
removal by ultraviolet light.
Could require pretreatment for efficient
use of ultraviolet light.
Significant suspended solids levels are
not likely in most ground water.
Some chlorine compounds are sensitive
topH. pH is a factor in organics
destruction efficiency by ultraviolet light
Recent research suggests better
inactivation rates at lower temperatures
using ultraviolet light.
. - - •
Ultraviolet light systems have the
smallest space requirement.
comparable to chemical disinfectants. The successful use of ultraviolet light for disinfection in the food
industry is a testimony to its feasibility and viability. In the food industry, ultraviolet light is used to
sterilize equipment, control surface growth on bakery products, inhibit mold growth and bacterial growth
in meat-processing plants, and treat water used for the depuration of shellfish and the production of cell
protein. ' .
The data reviewed to date clearly show that:
• The required inactivation dose for bacteria using ultraviolet light varies from one organism to
another and within the same species. Many factors could contribute to this variance:
— Source of microorganism •
— Age of microorganism
- Method of ultraviolet dose measurement
— Medium used -
- Organic and inorganic media quality parameters
- Physical parameters
• — initial microorganisms density
" - Ultraviolet intensity used
- Residence time
- Flow rate. :
UV Light Disinfection Technology in
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Chapter 2—Assessment of Ultraviolet Light Efficacy, Viability, and Operational Factors
• The order of disinfection resistance with few exceptions is as follows: bacteria < viruses <
bacterial spores < protozoan cysts and oocysts, with Gram-positive bacteria being more resistant
to ultraviolet light than Gram-negative bacteria.
• Naturally occurring microorganisms are more resistant to inactivation by ultraviolet light than
microorganisms cultured in laboratories.
• Current indicator surrogate microorganisms are more sensitive to ultraviolet light than many
identified microorganisms (including viruses) that are of concern in drinking water.
• In the meantime, two challenge surrogate microorganism candidates appear to be the best to test
ultraviolet light disinfection efficiency: Bacillus subtilis spores and bacteriophage MS-2.
Disinfectants, including ultraviolet light, have limitations, such as undesirable interaction with other water
constituents, lack of residual effect, or O&M costs and problems. In many applications, it might be useful
to consider the use of multiple disinfectants and water treatment processes. .An example of the practical
applicability of multiple use of disinfection treatment can be found aboard cruise ships that use ultraviolet
light for disinfection (the DHEW guideline dose is 16 mWs/cm2) followed by chlorine as a secondary
disinfectant for residual effect as per shipboard regulations (USEPA, 1983). In England, multiple
disinfection systems have been in use for more than 10 years; small systems of up to 2 MGD use
ultraviolet light for primary disinfection followed by hypochlorite for distribution system residual effects
(McCarty, 1986). The new studies from Norway concluded that ultraviolet light has some residual
disinfection effect although this is believed to be. of very limited effect. For a large number of small
NTNC and TNC ground water systems, a secondary disinfectant may not be necessary, as these systems
have no or a small distribution network. ' ,
As a tool to disinfect drinking water, ultraviolet light is effective against microorganisms. Ultraviolet light
is not, however, a panacea. For example, if a ground water source is iron-rich, it can cause fouling to the
ultraviolet light system and, hence, reduce light transmissibility. Therefore, the water needs to be treated
before reaching the ultraviolet disinfection unit. Located at the end of the treatment process where proper
pretreatment is needed or required, water entering an ultraviolet unit may be assumed to be clear and
contain little or no suspended matter or colloids.
To summarize the data reviewed, the effectiveness of ultraviolet light depends on the proper wavelength,
the intensity of the radiation, the exposure time, the distance from the light source to the organism to be
disinfected, and the water quality. Therefore, any guidelines to be developed for the use of ultraviolet
light for ground water disinfection need to consider the above-mentioned factors. However, based on the
UV Light Disinfection Technology in • •
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Chapter 2—Assessment of Ultraviolet Light Efficacy, Viability, and Operational Factors
work of Sommer and Cabaj (1993), a 60 mWs/cm2 ultraviolet .dose-is sufficient to achieve a 4 log
reduction in Bacillus subtilis spores. Based on Harris et al. (1987), a dose of 45 mWs/cm2 is sufficient
• to achieve a 3 log reduction in Reovirus 1 in buffered distilled water. A dose of 40 mWs/cm2 is sufficient
to cause a 5 log reduction in poliovirus (Harris, 1986). The scientific literature review revealed that a
greater than 2 log reduction of Giardia muris cysts can be achieved using ultraviolet light at a dose of 121
mWs/cm2. A minimum of 2 to 3 log reduction in Cryptosporidium parvum oocysts can be achieved using
an ultraviolet light dose of about 8,750 mWs/cm2.:
• ' .• ! ....•• • . ,
Some by-products formation is associated with the use of ultraviolet light to "disinfect effluent waters.
However, by-products formation is insignificant in effluent -treatment and extremely insignificant in
drinking water applications. Moreover, by-products formation in ultraviolet disinfection processes in water
and wastewater application is far less than that produced with the use of chlorination or ozonation.
Guidance on use of ultraviolet disinfection technology should identify a minimum specific intensity and
residence time and specify lamp arrangement and spacing based upon principal water quality parameters.
A breakdown in etiological agents of waterborne disease in outbreaks in the United States between 1971
and 1977 shows that in ground water systems bacteria accounts for 33 percent (main agents: Shigella,
30 percent; S. typhi, 2 percent; arid Salmonella, 1 percent). .HAV conies in second place as a microbial
agent of waterborne diseases with 3 percent. Finally, Giardia comes in third place with Jess than 1
percent. -Other agents of waterborne disease include chemical agents (6 percent) and unknown agents (58
percent) (USEPA, 1993b). The non chemical-related waterborne disease outbreaks in all water systems
resulted in about 130,000 cases of illness between 1971 and 1988 (USEPA, 1993b). The information
provided in USEPA, 1993, shows that 35 percent of outbreaks of waterborne diseases in the United States
occurred in non-community water supply systems. This figure is very conservative because of long
incubation periods and because symptoms of illness often occur in geographical areas far from where the
exposure occurred. A study by Moore et al., 1993 shows-that 68 percent of outbreaks (for the 1991-1992
period) of waterborne disease associated with drinking water occurred in non-community systems with
well water being the source in 77 percent of the cases. Therefore, any form of disinfection in TNC and
NTNC water systems will greatly reduce the number of outbreaks. The reviewed data clearly show that
many pathogenic bacteria (such, as Vibrio choleroe) and viruses (such aspoliovirus'and HAV) associated
with high morbidity and mortality around the world and that might be found in ground water sources, are
susceptible to ultraviolet disinfection. TNC ground water systems and NTNC ground water systems that
are not under direct influence of surface water (protozoa free) and that have little or no distribution
systems may benefit the most from ultraviolet light application.
UV Light Disinfection Technology in
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Chapter 2—Assessment of Ultraviolet Light Efficacy, Viability, and Operational Factors
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*• ' ' • ' . > - ' • . • ''
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Yip, R.W., and Konasewich, E. (1972). "Ultraviolet Sterilization of Water, Its Potential and Limitations."
Water & Pollution Control (Can.), Vol. 110, pp. 6-14.
ZefF, JJD. (1993). "Testing of a Full Scale UV/Oxidation System to Obtain a Permit for Removing PCE
from a Drinking Water at a Well Site in the City of South Gate, California." Ozone in Water and
Wastewater Treatment. Vol. 2, pp. S-13-1—S-13-14.
Zoeteman, B.C.J., et al. (1982).' "Mutagenic Activity Associated With By-Products of Drinking Water
Disinfection by Chlorine,' Chlorine Dioxide, Ozone and UV-Irradiation." Environmental Health
Perspectives, Vol. 46, pp. 197-205.
Zukovs, G., et al. (1986). "Disinfection of Low Quality Wastewaters by Ultraviolet Light Irradiation."
J. Wat. Pollut. Control Fed. Vol. 58, pp. 199-206.
Zumdahl, S. (1989). Organic Chemistry. 2nd ed. D.C. Heath and Company, pp. 264, 869-870, 983.
UV Light Disinfection Technology in
Drinking Water Application—An Overview. 2-78 Final—September 1996
-------
CHAPTER 3. EVALUATION OF ULTRAVIOLET LIGHT TECHNOLOGY
COSTS AND COMPARISON TO OTHER DISINFECTION PROCESSES
3.1 INTRODUCTION
Presented in this chapter are findings to date on costs associated with using ultraviolet light to disinfect
ground water sources of public drinking water. Cost factors relevant to ultraviolet light disinfection
include capital costs (i.e., equipment and construction costs) and operation and maintenance costs (i.e.,
parts replacement, power, and labor costs). Ultraviolet light costs derived from available information are
presented in section 3.2. Section 3.3 compares these costs with ultraviolet system cost estimates developed
previously by USEPA. Ultraviolet light costs are compared to costs associated with other disinfection
technologies such as chlorination and ozonation in section 3.4, while the costs of providing secondary
disinfection (i.e., a residual to protect distribution systems) are addressed in section 3.5. Section 3.6
presents costs from some foreign ultraviolet light systems.
The ultraviolet light system cost estimates and costing methodology in this report were based on previous
USEPA cost estimate reports, cost information collected from ultraviolet light equipment manufacturers,
other USEPA drinking water reports, and articles published in the scientific literature. Cost information
collected from ultraviolet light equipment manufacturers was used to compare current market prices with
previously reported cost estimates and to compare current ultraviolet costs with the cost of other well-
established disinfection technologies such as chlorination and ozonation. The costs presented in this report
are estimates and subject to some variance. Site-specific considerations, such as influent water quality,
are a major Variable in cost estimation and would impact the overall cost of the ultraviolet disinfection
system. In addition, USEPA considers these to be preliminary estimates of cost which will be subject to
change as cost methodologies, and groundwater disinfection requirements develop.
The cost estimates in this report are for USEPA flow categories 1 through 5. This includes all U$EPA
flow categories for small water systems, one medium-flow, and one large-flow USEPA category. The
average flow, design flow, and population served for those flow categories are presented in Exhibit 3-1.
Capital and operation and maintenance costs were studied for two doses: 40 mWs/cm2 and 140 mWs/cm2
at 253.7 nm for USEPA flow categories 1 through 5. The 40 mWs/cm2 dose was selected based on the
work of Harris (1986) that showed a 5 log reduction of poliovirus. Harris' work was adopted as the base
UV Light Disinfection Technology in
Drinking Water Application^-An Overview 3-1 Final—September 1996
-------
Chapter 3—Evaluation of Ultraviolet Light Technology Costs and Comparison
to Other Disinfection Processes
Exhibit 3-1. USEPA Flow Categories and Population Served
USEPA Row
Category
1
2
3
4
5
Average Flow (MGD)
0.0056
0.024
0.086
0.23
0.7
Peak Factor
4.3
3.6
3.1
2.8
2.6
Design Flow (MGD)
0.024
0.087
0.270
0.650
1.80
Population Range
25-100
101-500
501-1,000
1,001-3,300
3,301-10,000
for ANSI/NSF (1991) standard 55-1991 for Class A POU drinking water disinfection treatment systems.
The 140 mWs/cm2 dose is the minimum dose required under the National Water Research Institute
(NWRI, 1993) guidelines for water reclamation (e.g., for agricultural end users) in California. The NWRI
(1993) guidelines are based on the works of Chen and Kuo (1992) and CH2M HILL (1992) that showed
a 4 log reduction of poliovirus in treated domestic wastewater.
Costs can be expressed as annual costs or costs per thousand gallons of treated water. Costs per thousand
gallons are helpful in estimating the impact on the consumer's water bill. Both methods of cost expression
are used in this chapter to facilitate the use of the generated cost figures to assess the impact on the
consumer's water bill and to assess the national economic impact of using ultraviolet light for disinfecting
ground water for drinking.
Costs in this report are based on the use of modular vessels (closed systems) that require one electrical
connection and two plumbing connections. The capacity of modular units is assumed to follow the
following criteria:
• There' is a minimum of two units per treatment plant.
• When one unit is not in service, the other unit(s) have the capacity to carry peak design flow
(daily or hourly). The determination of whether the remaining units should be capable of
carrying hourly or daily peak flow capacity must be based on the system's water storage
capacity to account for peak hourly demand.
These criteria are based on USEPA's suggested recommendations for the use of ultraviolet systems under
the Draft Ground Water Disinfection Rule (GWDR). , ,
UV Light Disinfection Technology in
Drinking Water Application—An Overview
3-2
Final—September 1996
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Chapter 3— Evaluation of Ultraviolet Light Technology Costs and Comparison
_ - - • _ to Other Disinfection Processes
3.2 ULTRAVIOLET DISINFECTION COSTS
-' s " . ,
The total cost estimate for an ultraviolet system is the sum of two major costs: capital, including
equipment cost, and operation and maintenance cost.
Due to the fact that costs rise and fall in accordance with the economic market, costs need to be adjusted
to current value. Capital costs are adjusted through the use of the Engineering News Record Construction
Cost (ENRCC) Index (ENR, 1995). Operation and maintenance costs are adjusted using the Producer
Price Index, which is found in the publication Producer Prices and Price Indexes (PPPI, 1995). All
capital costs obtained from earlier reports and used in this:study were adjusted to the August 1995 20-city
average ENRCC Index value of 5506.33. This average value is not as accurate as a value for a specific
city or region of the United States and may overestimate or underestimate costs due to varying
construction costs in different parts of the country. If a specific city or region is known to be the future
site of an ultraviolet treatment system, the ENRCC index for that city or region should be used. This
method of cost adjustment is more applicable to chlorination systems than to ultraviolet systems, because
ultraviolet systems require very little construction work. '
Cost data in other literature were updated for comparison with current costs using the following standard
equation (WERE, 1995):
Construction Cost = — : - 5506.33 _ _ ReDorted r ^
Reported ENRCC Index KeP°rte
-------
Chapter 3—Evaluation of Ultraviolet Light Technology Costs and Comparison
to Other Disinfection Processes
Capital Cost (c/kgal) =
Capital Cost ($) x Amortization factor x
lOOc x 1 Year x 1 MG
$1 X 365 days X 1000 Kgal.
Flow (MOD)
3.2.1 Capital Costs
The capital cost for an ultraviolet system is mainly the equipment cost. Capital costs for this quasi "turn-
key" system involve the purchase of equipment and construction (if any) of a protection structure (room
or shed) and installation of the system. These costs depend on several factors, such as flow rate, degree
of treatment, and influent water quality. As flow rate increases, more lamps will be needed to provide
adequate light energy. The equipment becomes larger and more complex, and the cost rises accordingly.
The degree of treatment also affects the cost of equipment. An ultraviolet treatment for drinking water
that is closer to sterilization requires doses that are far higher than the doses required for disinfection.
Therefore, a high degree of treatment could be far more expensive than current disinfection requirements.
By the same token, a "poor" quality water that is high in microorganism densities or in plating and fouling
agents requires more ultraviolet energy to achieve the desired treatment levels.
The degree of treatment considered in this analysis is based on the use of ultraviolet systems capable of
delivering 40 mWs/cm2 and 140 Mws/cm2 doses to achieve the 5 log reduction of poliovirus in "good,"
i.e., filtered water sources that are low in plating and fouling agents, and a 4 log reduction of poliovirus
in "poor" water quality sources comparable to a filtered secondary wastewater effluent, respectively.
3.2.1.1 Equipment Costs
The cost estimates presented here are quotes from tiiree manufacturers that have considerable market share
and experience in ultraviolet technology. The equipment considered for use in small water systems
includes closed chamber ultraviolet modules with lamps and quartz sleeves, module support racks,
i
instrumentation and control panels, power supply distribution and ballasts, automatic cleaners, pipes and
valves, and other equipment to control and monitor the system. Through the use of modular systems, the
equipment cost can be calculated easily by estimating the number of modules required. The cost of
shipping and installation is included in the estimates. It is assumed in this study that all units include self-
cleaning mechanisms. Prefilter cost, if any, is not included in this analysis. The equipment costs and the
number of modular units and lamps required for different systems are summarized in Exhibit 3-2. As
UV Light Disinfection Technology in
Drinking Water Application—An Overview
3-4
Final—September 1996
-------
Chapter 3—Evaluation of Ultraviolet Light Technology Costs and Comparison
• to Other Disinfection Processes
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-------
Chapter 3—Evaluation of Ultraviolet Light Technology Costs and Comparison
to Other Disinfection Processes .
shown in Exhibit 3-2, the cost range for equipment delivering 40 mWs/cm2 is $8,000 to $143,000 and
$11,000 to $381,000 for equipment delivering 140 mWs/cm2.for flow categories 1 through 5.
3.2.1.2 Construction Costs
Because ultraviolet modules are typically small in size, no major construction costs are assumed in this
cost analysis. However, a 20-percent markup of the equipment cost is included in total capital cost to
account for engineering (10%); legal, fiscal, and administrative services (3%); sitework and interconnecting
piping (6%); and contingencies (1%), including any minor construction work that may be necessary, such
as a small shed to protect the ultraviolet equipment and its spare parts from the elements. This is shown
in Exhibit 3-3. According to USEPA (1993a), factors such as contractor's overhead and profit, electrical
connections, and standby power should be added to equipment costs to calculate capital costs for all types
of systems. However, these cost factors are not included here because closed ultraviolet systems resemble
a turnkey job more than an engineering design, construction, and supervision job. Also, USEPA (1993a)
states that electrical work would cost $1,300 per installed horsepower or approximately $1,740 per
installed kilowatt. This is not applicable to ultraviolet systems; because there is little electrical work
involved beyond plugging the system in. In addition, such costs account for comparatively insignificant
amounts.
Exhibit 3-3. Added Engineering and installation Costs
Item i
Engineering
Legal, Rscal, and Administrative
Sitework and Interconnecting Piping
Contingencies
Cost*
10 percent of equipment cost
3 percent of equipment cost
6 percent of equipment cost
1 percent of equipment cost
•Modified from USEPA (1993a).
3.2.1.3 Total Capital Costs
Equipment costs are the major source of capital costs. Therefore, total capital cost is equipment cost plus
20 percent, as detailed earlier. Although sheds, piping, electrical connections, engineering, legal services,
and construction in general do not account for a fixed percentage, the 20-percent markup in equipment
costs allows for variations in prices from one region to another and among different industries. For large
systems, the 20-percent markup might be an over-estimation, thus providing a more conservative cost
assessment of ultraviolet systems. This is illustrated in Exhibit 3-4, which gives, a straightforward total
UV Light Disinfection Technology in
Drinking Water Application—An Overview
3-6
Final—September 1996
-------
Chapter 3—Evaluation of Ultraviolet Light Technology Costs and Comparison
'" ' ' to Other Disinfection Processes
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Chapter 3—Evaluation of Ultraviolet Light Technology Costs and Comparison
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of capital costs in dollars and capital costs estimates in cents per thousand gallons for ultraviolet systems
delivering the two set doses of 40 mWs/cm2 and 140 mWs/cm2 for USEPA flow categories 1 through 5.
3.2.2 Operation and Maintenance Costs
Once a treatment system is in place, costs are incurred in the everyday operation of the facility.
Continuous 24-hour per day operation for the treatment system is assumed. However, during periodic
maintenance, a unit can be shut down while another unit or units carry the design flow. Operation and
maintenance costs include parts replacement, electric power consumption, and labor. The subsequent
operation and maintenance cost estimates are based on the following assumptions:
• The size of the system is based on design flow with redundancy in equipment, i.e., a minimum
of two module units with each unit capable of carrying design flow; if more than two module
units are used, then the total number of units minus one unit should be capable of carrying the
set design flow.
• Power consumption of lamp and ballast is calculated according to manufacturer's estimates (the
range is 70 - 85 watts for low-pressure lamp units).
• Lamp replacement is calculated according to manufacturer's estimates of lamp life at 70 percent
of its initial efficiency (as measured after 100 hours of service, the range is 8,000 - 14,000
hours). -
• Ballast replacement is done every ten years (worst case assumption).
• Quartz sleeves are replaced every five years (worst case assumption).
• Labor is estimated at 0.5 hours per lamp per year for cleaning and repairs. (The range is 0.25
hours per year to two hours per year)." •
• Chemicals (0.1 gallon per lamp per year) for cleaning once every 6 months (range 6 to 12
months).
• Miscellaneous equipment repair costs are accounted for at 0.1% of capital costs with a
minimum of $15 per year [for repairs such as replacement of a malfunctioning LED].
It is assumed that ultraviolet equipment is disposed of in a safe manner consistent with the disposal of any
electrically driven equipment, such as high-efficiency mercury-containing lamps and fluorescent lamps and
ballasts, and therefore present no significant additional costs. It should be noted that, sqme manufacturers
willingly take back ultraviolet lamps and ballasts for recycling of materials, presumably at no cost to the
water system user.
UV Light Disinfection Technology in
Drinking Water Application—An Overview 3-8 Final—September 1996
-------
Chapter 3—Evaluation of Ultraviolet Light Technology Costs and Comparison
to Other Disinfection Processes
3.2.2.1 Parts Replacement
Regular maintenance of equipment is necessary to keep the system operating properly. Materials in need
of regular replacement in an ultraviolet treatment system include ultraviolet lamps, ballasts, and sleeves.
Based on industry quotes, lamps cost between $40 and $100 each and should be replaced every 8,000 to
14,000 hours. Ballasts and LEDs may need to be replaced every 10 years. Quartz sleeves and
miscellaneous switches, valves, and rings may need to be changed every 5 years,
Exhibit 3-5 presents part replacement costs for equipment used to provide for the doses considered in this
report. These costs were provided by ultraviolet equipment manufacturers. Exhibit 3-5 shows that .the
difference in maintenance costs could be significant. The calculated maintenance costs for manufacturer
"A" are almost twice those of manufacturer "B" for all ultraviolet systems delivering 40 mWs/cm2 and
more than thrice the calculated maintenance costs of manufacturer "B" for systems delivering
140mWs/cmV '
3.2.2.2 Power Costs
Power costs are estimated assuming a unit rate of $0.086 per kilowatt-hour (USEPA, 1993b). This rate
is highly variable based .on the geographic location of the facility in the country and the source of electric
power. Power costs are based on the power requirements for each type of lamp and unit as provided by
the manufacturers assuming 24-hour per day operation.
( ' **.• -
Exhibit 3-6 presents calculated power costs in cents per thousand gallons of treated water for the doses
considered in this report and for USEPA flow categories 1 through 5.
3.2.2.3 Labor Costs
The facility's labor requirements are for the replacement of parts, general maintenance (cleaning of lamps,
sleeves, and the unit body), and monitoring. Cleaning requirements are highly site-specific in frequency,
level of effort, and time requirements. For high-quality water, an annual cleaning could be accomplished
by flushing the unit with a liquid detergent (approved synthetic organic detergent, ethanol, dilute
phosphoric acid, or dilute hydrochloric acid) after recycling it under pressure for a specific time, according
to manufacturer's recommendations. For low-quality water with fouling and plating problems, a monthly
cleaning might be necessary. The labor rate is assumed to be $15.50 per hour. This rate is in August
1995 dollars and is -based on estimates cited by DPRA (1993) fo^ a 10-city average for non-union scale
UV Light Disinfection Technology in
Drinking Water Application—An Overview 3-9 Final—September 1996
-------
Chapter 3—Evaluation of Ultraviolet Light Technology Costs and Comparison
to Other Disinfection Processes
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Chapter 3—Evaluation of Ultraviolet Light Technology Costs and Comparison
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UV Light Disinfection Technology in
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3-11
Final—September 1996
-------
Chapter 3—Evaluation of Ultraviolet Light Technology Costs and Comparison
to Other Disinfection Processes
laborers. The hourly rate of $15.50 includes an average salary of $9.15 per hour plus a 12.2 percent
fringe benefit and a 50 percent labor overhead cost. Average salaries ranged from $7.65 to $10.75 per
hour in the south central and western United States, respectively. , Fringe benefit rates ranged from
approximately 8 to 15 percent, depending on the region of the country (DPRA, 1993).
Based on these .assumptions, Exhibit 3-7 presents labor requirements in hours per lamp per year, total
hours per year, labor costs per year, and labor costs in cents per thousand gallons. As can be seen from
Exhibit 3-7, the labor costs for ultraviolet systems of 140 mWs/cm2 dose capacity are about double those
required for ultraviolet systems of 40 mWs/cm2 dose capacity for the same treated flows. Labor costs are
directly tied to the total number of lamps used in an ultraviolet light system. The increase in labor costs
between flow categories 4 and 5 could be traced back to the number of lamps used (see Exhibit 3-2).
3.2.2.4 Summary of Operation and Maintenance Costs
Major operation and maintenance costs can be found simply by adding part replacement cost, power cost,
and labor cost. It may be most appropriate to put major operation and maintenance costs in cents per
thousand gallons, as this allows for simple estimation of cost based on a plant's flow. Exhibits 3-5 (parts
replacement costs), 3-6 (power costs), 'and 3-7 (labor costs) are summarized in Exhibit 3-8.
Exhibit 3-9 presents an itemized account for total operation and maintenance costs per year and in cents
per thousand gallons. All the components of major operation and maintenance costs are included plus
miscellaneous and chemicals costs. The. figures in Exhibit 3-9 are average figures calculated from Exhibits
3-5, 3-6, and 3-7 according to the assumptions detailed in section 3.2.2. Where possible, unit prices are
listed, or a range is specified or a calculation method is provided. As can be, seen for Exhibit 3-9, for
every flow category, parts replacement costs constitute the highest operation and maintenance costs
followed by power consumption costs. Labor costs come in third place constituting less than 10 perpent
of the total operation and maintenance costs /for ultraviolet systems of 140 mWs/cm2 and 40 mWs/cm2 for
USEPA flow categories 1 through 5.
UV Light Disinfection Technology in
Drinking Water Application—An Overview 3-12 • . Final—September 1996
-------
Chapter 3—Evaluation of Ultraviolet Light Technology Costs and Comparison
- . to Other Disinfection Processes
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UV Light Disinfection Technology in
Drinking Water Application—An Overview
3-13
Final—September 1996
-------
Chapter 3—Evaluation of Ultraviolet Light Technology Costs and Comparison
to Other Disinfection Processes
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UV Light Disinfection Technology in
Drinking Water Application—An Overview
3-14
Final—September 1996
-------
Chapter 3—Evaluation of Ultraviolet Light Technology Costs and Comparison
- to Other Disinfection Processes
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UV Light Disinfection Technology in
Drinking Water Application—An Overview
3-15
Final—September 1996
-------
Chapter 3—Evaluation of Ultraviolet Light Technology Costs and Comparison
to Other Disinfection Processes
3.2.3 Total Costs of Ultraviolet Disinfection (Capital Costs and Operation and
Maintenance Costs)
Total production cost is the capital cost, amortized at 10 percent interest over a period of 20 years, plus
the operation and maintenance cost. The total cost estimates of ultraviolet systems as per quotes available
from ultraviolet equipment manufacturers are presented in Exhibit 3-10. Exhibit 3-10 was constructed
by combining the annualized cost estimates presented in Exhibit 3-4 (capital costs) and Exhibit 3-9
(operation and maintenance costs). Analysis of total production costs and operation and maintenance costs
indicate a linear relationship with flow capacity above 0.087 MOD.
Exhibit 3-10. Total Current Costs
Dose 40 mWs/cm2
USEPA
Row
Category
1
2
3
4
5
Design
Flow
(MGD)
0.024
0.087
0.27
0.65
1.8
Cost per Year
Total
Capital**
1.30
1.66
3.65
7.68
16.56
Total
O&M
0.38
0.79
1.69
3.70
9.74
k$)
Total
Production
Costs
1.7
. 2.5
5.3
11.4
26.3
Cost (c/kgal)
Total
Capital**
14.80
5.24
3.70
3.24
2.52
Total
O&M
4.32
2.49
1.71
1.57
1.48
Total
Production
Costs
19
8
5
5
4
Dose 140 mWs/cm2
USEPA
Flow
Category
1
2
3
4
5
Design
Flow
(MGD)
0.024
0.087
0.27
0.65
1.8
Cost per Year (k$)
Total
Capital"
1.66
3.63
10.01
16.45
42.05
Total
O&M
0.79
2.05
5.49
9.39
33.98
Total
Production
Costs
2.5
5.7
15.5
25.8
76.0
Cost(cTkgal)
Total
Capital**
18.99
11.42
10.16
6.94
6.40
Total
O&M
8.97
6.45
5.57
3.96
5.18
Total
Production
Costs
28
18
16
•11
12
'August 1995 dollars.
"Costs amortized at 10% for 20 years.
UV Light Disinfection Technology in
Drinking Water Application—An Overview 3-16
Final—September 1996
-------
Chapter ^Evaluation of Ultraviolet Light Technology Costs and Comparison
' to Other Disinfection Processes
3.3 COMPARISON OF CURRENT ULTRAVIOLET SYSTEMS COST ESTIMATES
TO ULTRAVIOLET COSTS REPORTED IN A 1993 USEPA DOCUMENT
For comparison, the document titled Very Small Systems Best Available Technology Cost Document
(USEPA, 1993a) provides a recent estimate of costs of using-ultraviolet technology in drinking water
treatment. '
V,
As stated earlier, cost estimates calculated in section 3.2 are based on two ultraviolet light doses
40 mWs/cm2and 140 mWs/cm2. Very Small Systems Best Available Technology Cost Document (USEPA,
1993a) presents models for the calculation of ultraviolet light system capital and operation and
maintenance costs. These models were not used in the development of cost estimates for this report
because.they were based on the 1984 WATER model, which assumes an ultraviolet light dose of 16 to
30 mWs/cm2. Also, when equipment and costs are being considered, it is reasonable to assume that the
ultraviolet technology of 1984 does not include all the components of 1995, such as better control systems
and greater lifespan. Moreover, the 1984 WATER model is an old model that might not reflect all the
cost variables encountered in 1995 ultraviolet systems (such as ultrasonic cleaners and automatic wipers).
The cost estimates generated using the USEPA 1993a cost analysis are presented here to show similarities
and differences among cost estimates.
For flows less than or equal to 270 kgpd, the governing equation used in USEPA (1993a) to calculate
capital costs is: - "
: GAP = 0.099[FLOW] +3.45 . , •
WHERE: CAP = Total capital costs (k$)
"FLOW = Design flow (kgpd)
The governing equation:
CAP = 0.125 [FLOW] + 4.16 .
is used to calculate capital costs for flows greater than 270 kgpd. The capital costs according to this
equation, adjusted to 1995 dollars, are presented in Exhibit 3-11 for the five EPA flow categories.
UV Light Disinfection Technology in
Drinking Water Application—An Overview 3-17 Final—September 1996
-------
Chapter 3—Evaluation of Ultraviolet Light Technology Costs and Comparison
to Other Disinfection Processes
Exhibit 3-11. Ultraviolet Capital Cost Estimates (Source: USEPA, 1993a)
USEPA Row
Category
1
2
3
4
5
Average Flow
(kgpd)
5.6
24
86
230
700
Design Flow
{kgpd)
24
87
270
650
1,800
Capital Cost
(k$)
5.83
12.06
30.18
85.41
229.16
Annualized: Capital Cost*
(c/kgal)
7.82
4.46
3.60
4.23
4.10
•Costs are annualized at 10% interest for 20 years. ,
The WATER model for operation and maintenance costs for ultraviolet light disinfection systems assumes
a maximum 30 mWs/cm2 dose and 0.12 hours per week for labor requirements. The model does not
explicitly indicate whether equipment redundancy is considered in the cost estimates.
For flows less than or equal to 86 kgpd, the governing equation used in USEPA, 1993a to calculate
!• ' '
operation and maintenance is: " ,
1
OM = 17.8 [AVG]-0'427 + 209.4 [LAB]' [AVG
WHERE: OM = Operation and maintenance costs (c/kgal)
AVG = Average daily flow (kgpd)
LAB = Labor required (hours/week).
For flows greater than 86 kgpd, the equation used to calculate operation and maintenance cost is:
OM = 17.8[AVG]-°-427 + 398;9 [LAB] [AVG]-1
The operation and maintenance costs calculated using this model are presented in Exhibit 3-12.
Exhibit 3-12. Ultraviolet Operation and Maintenance Cost Estimates
(Source: USEPA, 1993a)
USEPA Flow Category
1
2
3
4
5
Average Flow (kgpd)
5.6
24
86
230
700
Design Flow (kgpd)
24
87
270
650
1,800
O&M(c/kgaI)
13.02
5.63
2.95
1.95
1.15
•August 1995 dollars.
UV Light Disinfection Technology in
Drinking Water Application—An Overview
3-18
Final—September 1996
-------
Chapter 3—Evaluation of Ultraviolet Light Technology Costs and Comparison
, • to Other Disinfection Processes
To account for varying labor estimates for different flow categories, the USEPA (1993a) O&M estimates
are adjusted in Exhibit 3-13 using average labor requirements from three manufacturer quotes based on
an ultraviolet light dose of 40 mWs/cm2. A graphical comparison of total production costs based on
USEPA (1993a) labor requirement estimates (see Exhibit 3-12) and based on manufacturer's labor
requirement estimates (see Exhibit 3-13) is presented in Exhibit 3-14. Exhibit 3-14 is constructed by
adding the USEPA, 1993a annualized capital costs (see Exhibit 3-11) to USEPA, 1993a operation and.
maintenance costs (see Exhibit 3-12), and to the adjusted operation and maintenance costs (see Exhibit
3-13). Exhibit 3-14 shows that adjusted labor costs have the greatest impact on the total production costs'
of flow category one.
Exhibit 3-13. Adjusted (USEPA, 1993a) Operation and Maintenance Costs as per
Manufacturers'Estimates of Labor Requirements
USEPA Flow
Category
1
2
3
- 4
5 . -
Average Flow -
(kgpd)
5.6
24
86
230
700
Design Flow
. (kgpd)
24
87
270
650
1,800
Labor Required*
(hours per week)
0.045
0.090
0.160
0.346
0.782
Adjusted O&M
Costs (c/kgal)
10.21
5.37
3.05
2.35
1.53
•Based on average labor requirements as recommended in three manufacturer quotes. .
Exhibit 3-15 summarizes the total cost estimates of ultraviolet systems calculated based on labor
requirements as reported in Very Small Systems Best Available Technology Cost Document (USEPA,
1993a), and based on adjusted operation and maintenance costs.
For cost verification purposes, graphical comparisons of the costs developed by SAIC under this task for
ultraviolet systems delivering a 40 mWs/cm2 dose and a 140 40 mWs/cm2 dose and costs calculated based
on the methodology provided in USEPA (1993a). Graphical presentation for capital costs are presented
in,Exhibit 3-16. As can be seen from Exhibit 3-16, for How category 1 (design flow 24 Kgpd), capital
costs for ultraviolet systems delivering doses ranging from 16-30 mWs/cm2 to 140 mWs/cm2 are very
close.
For flow categories 2 and 3, capital costs for ultraviolet systems delivering an ultraviolet light dose of less
than 40 mWs/cm2 are almost identical. The capital costs of 140 mWs/cm2 ultraviolet treatment system
UV Light Disinfection Technology in
Drinking Water Application—An Overview
3-19
Final—September 1996
-------
Chapter 3—Evaluation of Ultraviolet Light Technology Costs and Comparison
to Other Disinfection Processes
Exhibit 3-14. Comparison of Total Production Costs with Varying Labor Requirements
25
20 -
*
1
8
10 -
5 -
0
0.024
0.087 0.27 0.65
Design Flow (MGD)
1.8
Total Production Costs: USEPA (1993a) Estimate of Labor Requirements
Total Production Costs: Manufacturers' Estimates of Labor Requirements
UV Light Disinfection Technology in
Drinking Water Application—An Overview
3-20
Final—September 1996
-------
Chapter 3—Evaluation of Ultraviolet Light Technology Costs and Comparison
' • to Other Disinfection Processes
Exhibit 3-15. Ultraviolet Cost Estimates (Source: USEPA, 1993a)
USEPA
Flow
Category
1
4
Average
Flow
(kgpd)
5.6
r 24
86
230
700
Design
Flow
(kgpd)
24
87
270
650
1,800
Capital
Cost (k$)
5.83
12.06
30.18
85.41
229.16
Annualized
Capital Cost*
(c/kgal)
7.82
4.46
3.60
4.23
4.10
O&M**
(c/kgal)
13.02
5.63
2.95
1.95
1.15
Total
Production
Costs
(c/kgal)
21
10
7
6
5
Total Production
Costs with
Adjusted O&M
Costs (c/kgal) •
18
10
•7
7
6
•Capital cost amortized at 10% interest over 20 years. ' .
"Based on USEPA (1993a) tebor requirements of 0.12 hours per week, for all flow categories.
' ' ' • • V
is the highest for flow categories 2 through 5. For flow categories 4 and 5, current capital cost estimates
for 40 mWs/cm2 ultraviolet systems are lower than capital cost estimates calculated based on the USEPA,
1993a water cost model for a 16-30 mWs/cm2 ultraviolet treatment system. Graphical presentations of
operation and maintenance costs for 16-30 mWs/cm2,40 mWs/cm2,and 140 mWs/cm2 ultraviolet treatment
systems are presented in Exhibit 3-17. As can be seen from Exhibit 3-17, operation and maintenance cost
estimates for a 140 mWs/cm2 ultraviolet treatment system are higher than the operation and maintenance
cost estimates for a 40 mWs/cm2 ultraviolet treatment system for flow categories 1 through 5. Operation
and maintenance cost estimates for a 140 mWs/cm2 ultraviolet treatment system are higher than the
operation and maintenance costs estimates developed using USEPA, 1993c methodology for flow
categories 2 through 5. , -
Graphical comparisons of total production cost estimates developed by SAIC under'this task for 40
,mWs/cm2 and 140 mWs/cm2 ultraviolet treatment systems and total production cost estimates for 16-30
mWs/cm2 ultraviolet treatment systems developed using USEPA, 1993a methodology are presented in
Exhibit 3-18. ,
As can be seen from Exhibit 3-18, the costs estimated by USEPA (1993a) are close to those estimated
using manufacturer's quotes for the 40 mWs/cm2 dosage. Overall, however, costs for ultraviolet systems
delivering 40 mWs/cm2 dosage are consistently approximately two cents per thousand gallons less
expensive than the USEPA (1993a) estimates for total production costs for ultraviolet systems delivering
16to 30 mWs/cm2 dosage.
UV Light Disinfection Technology in
Drinking Water Application—An Overview
3-21
Final—September 1996
-------
Chapter 3—Evaluation of Ultraviolet Light Technology Costs and Comparison
to Other Disinfection Processes
Exhibit 3-16. Comparison of Capital Costs of Ultraviolet Treatment
UV Light Disinfection Technology in
Drinking Water Application—An Overview
3-22
.Final—September 1996
-------
Chapter 3-Evaluation of Ultraviolet Light Technology Costs and Comparison
„ /to Other Disinfection Processes
Exhibit 3-17. Comparison of Operation and Maintenance Costs of Ultraviolet Treatment
UV Light Disinfection Technology in
Drinking Water Application—An Overview
3-23
Final—September 1996
-------
Chapter 3—Evaluation of Ultraviolet Light Technology Costs and Comparison
to Other Disinfection Processes
Exhibit 3-18. Comparison of Total Production Costs of Ultraviolet Treatment
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-------
Chapter 3—Evaluation of Ultraviolet Light Technology Costs and Comparison
"- . . ' ' to Other Disinfection Processes
3.4 ULTRAVIOLET LIGHT SYSTEM COSTS COMPARED TO CHLORINATION
AND OZONATION DISINFECTION TECHNOLOGIES
In this section, the current total cost for ultraviolet treatment is compared to that of chlorination and
ozonation. Chlorination and ozonation costs reported here are obtained from USEPA (1993a), calculated
in August 1995 dollars.
3.4.1 Ozonation Costs
The following formulas apply to small and large decentralized systems employing primary treatment
through ozonation (USEPA, 1993a):
CAPITAL COSTS: :
For flows less than or equal to 270 kgpd, the equation used to calculate capital costs for an ozonation
system that can deliver an ozone dose of 1 mg/L is:
|0.272
CAP1 = 24.2[DES]
WHERE: CAP1 =.Total capital cost, 1 mg/L ozone dose (k$)
DBS = Total design .flow (kgpd)
For flows greater than 270 kgpd, the equation used to calculate capital costs for an ozonation system that
can deliver an ozone dose of 1 mg/L is:
CAP1 = 28.0PES]0-269
WHERE: CAP1 = Total capital cost, 1 mg/L ozone, dose (k$) •
DBS = Total design flow (kgpd) ,
These ozonation costs are based on a dose of 1 mg/L and an assumed contact time of 10 minutes. This
dose is a "low demand" dose with an assumed residual of Q.I mg/L. Ozone treatment at this dose
provides the lowest cost estimate for ah ozone drinking water disinfection system.
O&M COSTS: ,
For flows less than or equaTto 86 kgpd, the equation used to calculate operation and maintenance costs
of an ozone system delivering 1 mg/L is:
OM1 = 24.8[AVG]^-486 + 209.8[LAB][AVG]
UV Light Disinfection Technology in
Drinking Water Application—An Overview 3-25 Final—September 1996
-------
Chapter 3—Evaluation of Ultraviolet Light Technology Costs and Comparison
to Other Disinfection Processes
WHERE: OM1 = O&M costs, 1 mg/L ozone dose, (c/kgal)
AVG = Average daily flow (kgp'd) ,
LAB = Available labor for O&M (hrs/week)
For flows greater than 86 kgpd, the equation used to calculate operation and maintenance costs is:
OM1 = 24.8[AVG]-°-486 + 398.9[LAB][AVG3-'
WHERE: OM1 = O&M costs, 1 mg/L ozone dose, (c/kgal)
AVG = Average daily flow (kgpd)
LAB = Available labor for O&M (hrs/week)
According to USEPA (1993a), labor requirements are assumed to be 7 hours per week. The cost estimates
for the ^installation of such an ozone facility include an off-gas destruction unit, ozone gas detector and
alarm, and building with ventilation to house the system (USEPA, 1993a).
Exhibit 3-19 is a tabular representation of the calculated costs of ozone treatment from USEPA (1993a).
Exhibit 3-19. Small System Ozonation Costs
(Source: USEPA, 1993a)
USEPA Row
Category
1
2
3
4
5
Average
•Flow (kgpd)
5.6 .
24
86
230
700
Total Capital
(k$)
57.44
81.54
110.95
159.39
210.29
Total Capital
(0/kgal)
77.02
30.16
13.22
7.92
3.76
Total O&M
(c/kgal)
273.99
66.48
19.92
13.90
5.02
Total Production
Cost (c/kgal)
351
97
33
22-
9
'August 1995 dollars.
"Cost amortized at 10% for 20 years.
3.4.2 Chlorination Costs
Chlorination cost estimates are based on a 5 mg/L dose with an assumed residual concentration of at least
0.5 mg/L and a labor requirement of seven to ten hours per week. This extrapolates (linear extrapolation)
to 7, 7.1, 7.4, 8.1, and 10 hours per week for flow categories 1 through 5, respectively. While chlorine
treatment dose could range from 1 to 10 mg/L, the 5 mg/L dose also reflects a "medium demand" dose
and provides a reasonable cost estimate for a Chlorination process (sodium hypochlorite feed system). The
cost estimates based on the USEPA (1993a) document for the installation of a Chlorination facility include
a metering pump, a mixer and storage tank, and various pipes and valves.
UV Light Disinfection Technology in
Drinking Water Application—An Overview
3-26
Final—September 1996
-------
Chapter 3—Evaluation of Ultraviolet Light Technology Costs and Comparison
• • - to Other Disinfection Processes ,
CAPITAL COSTS
.For flows less than or equal to 270 kgpd, the capital cost!;are assumed to be:
. CAP = 4.7 • '. . • .•-.'" •'• ' '.- .
For flows greater than 270 kgpd, the capital costs are assumed to be:
CAP = 6.9 . ' '. ,
WHERE: CAP = Total capital cost (k$)
It is important to note that the capital costs do.not vary with flow due to the wide range of pumping rates
• achievable by similarly priced pumps (USEPA, 1993a)
O&M COSTS: .
• For flows less than or equal to 86 kgpd, the governing equation for operation and maintenance costs is:
OM = 66.0CAVG]-1 + 0.67[C1] + 209.4[LAB][AVG]-1
WHERE: OM=t O&M costs (c/kgal)
AVG = Average daily flow (kgpd) ,
Cl = Chlorine dosage (mg/L)
LAB = Available labor for O&M (hrs/week) '
. For flows greater than 86 kgpd, the governing equation for operation and maintenance costs is:
OM = 66.0[AVGr] + 0.67[C1] + 398.9[LAB][AVG]-1
WHERE: OM = O&M costs (c/kgal)
AVG = Average daily flow (kgpd)
Cl = Chlorine dosage (mg/L)
LAB = Available labor for O&M (hrs/week) , '
Exhibit 3-20 presents the calculated costs for chlorination based on the equations provided in the USEPA
(1993a) document. • '
Exhibit 3-21 is a tabular presentation of current ultraviolet light system costs developed for ultraviolet
light doses of 40 mWs/cm2 and 140 mWs/cm2 compared to ozonation and chlorination. Exhibit 3-22 is
a graphical presentation of current ultraviolet light costs for an" ultraviolet dose of 40 mWs/cm2 developed
under this work assignment compared to costs of ozonation and chlorination. Exhibit 3-23 is a graphical
presentation of current ultraviolet light system costs for an ultraviolet light dose of 140 mWs/cm2
developed under this task compared to costs of ozonation and chlorination.
UV Light Disinfection Technology in
Drinking Water Application—An Overview 3-27 Final—September 1996
-------
Chapter 3—Evaluation of Ultraviolet Light Technology Costs and Comparison
to Other Disinfection Processes /
Exhibit 3-20. Small System Chlorination Costs (Source: USEPA, 1993a)
USEPA Flow
Category
1
2
3
4
5
Average
Flow
(kgpd)
5.6
24
86
230
700
Total
Capital
(k$)
4.70
4.70
4.70
6.90
6.90
Total
Capital
(c/kgal)
6.30
1.74
0.56
0.34
0.12
Labor
Requirements
(hours/week)
7
7.1
7.4
8.1
10
Total O&M
(c/kgal)
276.89
68.05
22.14
17.68.
9.14
Total
Production Cost
(c/kgal)
283
70
23
18
9
*Costs amortized at 10% interest for 20 years.
"August 1995 dollars.
Exhibit 3-21. Ultraviolet Light System Costs for USEPA Flow Categories 1-5 Compared
to Chlorination and Ozonation in Cents per Thousand Gallons*
USEPA Row
Category
1
2
3
4
5
Design Flow
MGD
0.024
0.087
0.27
0.65
1.8
Ultraviolet
Dose
40 mWs/cm2
19
8
5
5
4
Chlorination
Dose 5 mg/L
283
70
23
18
9
Ozonation
Dose 1 mg/L
351
97
33
22
9
Ultraviolet
Dose
140 mWs/cm2
28
18
16
11
12 '
'August 1995 dollars.. ' ,
Based on the above, it is clear that ultraviolet light technology is an economically viable and feasible
technology, particularly for small water systems that lack highly paid qualified operators. Moreover, it
is anticipated that, as more ultraviolet light technology is developed, the capital and operation and
maintenance costs associated with ultraviolet treatment will decrease, making this technology more
competitive. ' .
UV Light Disinfection Technology in
Drinking Water Application—An Overview
3-28
Final—September 1996
-------
Chapter 3—Evaluation of Ultraviolet Light Technology Costs and Comparison
' • to Other Disinfection Processes .
Exhibit 3-22. Ultraviolet [40 mWs/cm2], Chlorination, and Ozonation Total Costs:
USEPA Flow Categories 1-5
400
300 -
^
I
200 -
100 -
0
0.024 0.087 0.27 0.65
Design Flow (MGD)
1.8
Ozonation Dose: 1 mg/l §• Ghlorination Dose: 5 mg/L
UV Radiation Dose: 40 mWs/sq cm
UV Light Disinfection Technology in
Drinking Water Application—An Overview 3-29
Final—September 1996
-------
Chapter 3—Evaluation of Ultraviolet Light Technology Costs and Comparison
to Other Disinfection Processes
Exhibit 3-23. Ultraviolet [140 mWs/cm2], Chlorination, and Ozonation Total Costs:
USEPA Flow Categories 1-5
400
300 -
ff
I
8
200 -
100 -
0
0.024 0.087 0.27 0.65
Design Flow (MOD)
1.8
Ozonation Dose: 1 mg/1
UV Radiation Dose: 140 mWs/sq cm
Chlorination Dose: 5 mg/1
UV Light Disinfection Technology in
Drinking Water Application—An Overview 3-30
Final—September 1996
-------
Chapter 3— Evaluation of Ultraviolet Light Technology Costs and Comparison
. _ __ _ to Other Disinfection Processes .
3.5 COST OF ULTRAVIOLET DISINFECTION WITH SECONDARY TREATMENT
THROUGH CHLORINATION
Because a residual may be desired in the distribution system, ultraviolet disinfection may be supplemented
by chlorination as a secondary treatment process. This typically involves the use of sodium hypochlorite
or calcium hypochlorite. A chlorine concentration of 1 mg/L can "be assumed. Such a concentration is
sufficient to control microbial growth in the distribution system.
3.5.1 Cost of Secondary Treatment
- " . ' - , • i
For our purposes, sodium hypochlorite will be used, which, according to USEPA (1993a), costs
approximately $190 per ton of chemical. The amount of chemical to be used per day can be calculated
by dividing the amount of chlorine required per day by the percentage of -available chlorine in the
chemical to be purchased. One can assume that sodium hypochlorite (NaOCl) or calcium hypochlorite
[Ca(ClO)2] is at least 65 percent available chlorine (practical grade; theoretical available chlorine in NaOCl
is 95.4% and in Ca(ClO)2 is 99.2%). The use of the dose-dependent equation for chlorine disinfection
costs presented iri USEPA (1993a) as shown in section 3.4.2 is appropriate here, assuming a chlorine dose
of 1 mg/L. This dosage is high enough to leave a residual and ensure thorough disinfection while low
enough to minimize costs.
Although it is not necessary to determine the amount of chlorine required to satisfy a 1 mg/L dosage
requirement, doing so may shed some light on the size of storage tank needed and the amount of labor.
required to mix the chemicals and fill the storage tank. The following equations may be used to determine
chlorine arid stock solution requirements: -
• Pounds per day chlorine required =.
.-:'- Average Flow f-^-1 x dose fail x l ^ x — *i x '
'
—
dayj ' (I ) 1000000 mg 0.45kg gal
• Assume 65% available chlorine in sodium hypochlorite and a 5% stock solution
• Gallons per day of stock solution requires =
Qbs/day chlorine)
(5% Hypochlorite Strength) x 8.3 £
gal
The resulting stock solution requirements are presented in Exhibit 3-24.
UV Light Disinfection Technology in
Drinking Water Application— An Overview 3-31 Final— September 1996
-------
Chapter 3—Evaluation of Ultraviolet Light Technology Costs and Comparison
to Other Disinfection Processes
Exhibit 3-24. Amount of Chlorine Stock Solution Required Per Day (1 mg/L Dose)
USEPA How
Category
1
2
3
4
5
Average Daily Flow
(kgpd)
5.6
2.4
86.0
230.0
. 700.0
Gallons/Day Stock
Solution Required - .
0.12
0.48
1.71
4.60
14.00
Because these are relatively small amounts of required stock solution, a standard 150-gallon tank would
be too large. If a 150-gallon stock is prepared for use, the chlorine would evaporate out of the solution
before the solution is completely used. A smaller storage tank that would necessitate refilling with stock
solution would be more suitable. To prepare fresh stocks, a 2-hour labor requirements is assumed every
4 days for flow categories one, two, and three (35 hrs/week). A 2-hour labor requirement is assumed for
flow categories four and five with chlorine stock solution prepared every other day (7 hrs/week).
i
The costs associated with secondary treatment are presented in tabular .form in Exhibit 3-25 and
graphically in Exhibit 3-26. Some non-community water systems may find the 1 mg/L dosage of chlorine
suitable for complete water treatment, in which case these costs could be adapted to estimate primary
disinfection through chlorination. In a 20-month pilot study, 0.05 mg/L of free chlorine after ultraviolet
treatment was found to be sufficient to suppress biofilm formation (Lund and Ormerod, 1995). In small
systems, a residual free chlorine levels of 0.2 mg/L are considered to be sufficient to protect water supplies
(Huck, 1989). It is of interest to note that the overall cost of treatment with 1 mg/L chlorine differs from
treatment with 5 mg/L chlorine by only a few cents per thousand gallons.
Exhibit 3-25. Total Production Costs of Secondary Treatment Through 1 mg/L Chlorine
USEPA
Flow
Category
1
2
3
4
5
Average
Row
(kgpd)
5.6
24
86
230
700
Design
Row
{kgpd)
24
87
270
650
1800
Capital
Cost (k$)
4.70
4.70
4.70
6.90
6.90
Amortized
Capital Cost
(c/kgal)
6.30
1.74
0.56
0.34
0.12
Labor
Requirement
(hrs/week)
3.5
3.5
3.5
7.0'
7.0
O&M
Costs
(c/kgal)
143.33
33.96
9.96
13.10
4.75
Total
Production
Costs (c/kgal)
150
36
11
13
5 .
UV Light Disinfection Technology in
Drinking Water Application—An Overview
3-32
Final—September 1996
-------
Chapter 3-Evaluation of Ultraviolet Light Technology Costs and Comparison
to Other Disinfection Processes
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t/1/ L/g/jf Disinfection Technology in
Drinking Water Application—An Overview
3-33
Final—September 1996
-------
Chapter 3—Evaluation of Ultraviolet Light Technology Costs and Comparison
to Other Disinfection Processes
3.5.2 Total Production Costs for Ultraviolet Disinfection with Chiorination
Total production costs of primary disinfection through ultraviolet treatment and secondary disinfection
through chlorination are presented in Exhibit 3-27. These costs were found by simply adding the costs
of ultraviolet treatment at dosages of 40 and 140 mWs/cm2 to the costs of chlorination at a dosage of 1
mg/L. Total production costs for ultraviolet treatment and secondary disinfection through chlorination are
presented graphically in Exhibit 3-28.
Exhibit 3-27. Total Production Costs of Ultraviolet Treatment with
Secondary Disinfection
USEPA
Row
Category
1
2
3
4
5
Average
Flow
(kgpd)
5.5
24
86
230
700
Design
Flow
(kgpd)
24
87
270
650
1800
Total Production Costs (c/kgal)
40 mWs/cm2
UV Treatment
19
8
5
•• 5
. 4
140 mWs/cm2
UV Treatment
28 . .
18
16
11
12
40 mWs/cm51 UV
Treatment with
1 mg/L Chorine
169
44
16
18
9
140 mWs/cm2 UV
Treatment with
1 mg/L Chorine
178
54
27
24
17
3.5.3 Comparison to Other Treatment Techniques
Exhibits 3-29 and 3-30 are graphical presentations of the total costs of ozonation, chlorination, and
ultraviolet disinfection with 1 mg/L chlorine secondary treatment, at ultraviolet doses of 40 mWs/cm2 and
140 mWs/cm2, respectively. Exhibit 3-31 is a tabular presentation of the costs of ultraviolet light system
with chlorination compared to ozonation and chlorination. '
3.6 ULTRAVIOLET LIGHT SYSTEM COST ESTIMATES FROM OTHER
SOURCES
E
The Canadian pilot plant study cited earlier (Zukovs et al., 1986) compared the costs of ultraviolet light
application in combined sewer overflows (CSOs) to those of chlorination/dechlorination systems required
to achieve similar bacterial kill. The estimated capital costs for ultraviolet light systems used on low-
quality CSOs were consistently higher than those for chlorination/dechlorination systems for flow rates
between 5,000 and 500,000 m3/d (1.3 MOD - 132 MOD). However, the operation and maintenance costs
for both systems were within the same order of magnitude (Exhibit 3-32).
UV Light Disinfection Technology in
Drinking Water Application—An Overview
3-34
, Final—September 1996
-------
Chapter 3-Evaluation of Ultraviolet Light Technology Costs and Compari
to Other Disinfection Processes
son
Exhibit 3-28. Total Production Costs for Ultraviolet Disinfection with Chlorination
noijonpoo&
UV Light Disinfection Technology in
Drinking Water Application—An Overview ,3-35
Final—September 1996
-------
Chapter 3—Evaluation of Ultraviolet Light Technology Costs and Comparison
to Other Disinfection Processes
Exhibit 3-29. Total Costs: Ozonation, Chiorination, and Ultraviolet Radiation
(40 mWs/cm2) with Secondary Treatment
400
300 -
k>
•^
1
100 -
0
0.024 0.087 0.27 0.65
Design Flow (MOD)
1.8
Ozonation Dose: 1 mg/L Hi Chiorination Dose: 5 mg/L
UV Radiation Dose: 40 mWs/sq cm plus 1 mg/L chlorine
UV Light Disinfection Technology in
Drinking Water Application—An Overview
3-36
Final—September 1996
-------
Chapter 3-Evaluation of Ultraviolet Light Technology Costs and Comparison
'• _ to Other Disinfection Processes
Exhibit 3-30. Total CoSts ozonation, Chlorination, and Ultraviolet Radiation
(140 mWs/cm2) with Secondary Treatment
0
0.024 0.087 0.27 0.65
Design Flow (MOD)
1.8
Ozonation Dose: 1 mg/L
I Chlorination Dose: 5 mg/L
UV Radiation Dose: 140 mWs/sq cm plus 1 mg/L chlorine
:UV Light Disinfection Technology in
Drinking Water Application—An Overview 3-37
Final—September 1996
-------
Chapter 3—Evaluation of Ultraviolet Light Technology Costs and Comparison
to Other Disinfection Processes
Exhibit 3-31. Total Production Costs of Ultraviolet Treatment with Secondary Treatment
Compared to Chlorination and Ozonation
USEPA Row
Category
1
2
3
4
.5
Design
Row
(MGD)
0.024
0.087
0.27
0.65
1.8
Average
Flow
(kgpd)
5.6
24
86
' 230
700
Total Production Costs (Cents per Thousand Gallons)1
Chlorination
Dose 5 mg/L
280
70
20
20
;10
Ultraviolet
Dose 40
mWs/cm2
with 1 mg/L
Chlorination
170
40
20
20
10
• Ozonation
Dose 1 mg/L
350
100
30
20
10
Ultraviolet
Dose 140
mWs/cm2
with 1 mg/L
Chlorination
180
50
30
, 20
20
'Rgures are rounded to nearest ten.
Exhibit 3-32. Estimated Capital and Operating Costs for Ultraviolet Irradiation and
Chlorination/Dechlorination (Zukovs et al., 1986)'
Flowrate MGD
1.3
13.2
132
UV Irradiation
Capital Cost ($1985
Canadian)
245,200
2,208,180
21,801,000
O&M Cost ($1985
Canadian/Year)
.18,110
78,925
672,700
Chlorination/Dechlorination
Capital Cost ($1985
Canadian)
50,560
84,120
380,305
O&M Cost ($1985
Canadian/Year)
16,790
60,700
496,000
In an actual case study of costs associated with ultraviolet disinfection in the Zevenbergen drinking water
treatment plant (the Netherlands), the annual costs associated with a design flow of 450 nrVhr (1,981 gpm)
with an actual production of 2.5 x 10s m3/yr (1.8 MGD) using'two different ultraviolet light disinfection
devices were $0.0054/m3 and $0.0057/m3 (2.04 c/kgal and 2.16 c/kgal) (see Exhibit 3-33). The annualized
cost of ultraviolet light disinfection reported in the text of the article by Kruithof et al; (1992) at
$1/2,000 m3 (0.1893 c/kgal) is one order of magnitude less than, the figures shown in Exhibit 3-33.
Evidently, this low cost figure of 0.1893 c/kgal. is the result of a mathematical error on the part of the
authors.
As can be seen from Exhibit 3-33, the high cost estimates of ultraviolet light water disinfection systems
in the United States (see Exhibits 3-4, 3-9, and 3-10) compared to the costs of ultraviolet disinfection
systems in the Netherlands as reported in Kruithof et al. (1992) has to do primarily with capital costs
($73,000 to $80,000 per system in the Netherlands compared to $91,200 to $171,100 per system for the
same flow category as a 40 mWs/cm2 ultraviolet dose in the United States) and energy costs (5.2 to 5.5
UV Light Disinfection Technology in
Drinking Water Application—An Overview
3-38
Final—September 1996
-------
Chapter-3—Evaluation of Ultraviolet Light Technology Costs and Comparison
to Other Disinfection Processes
~ Exhibit 3-33. Ultraviolet Light Treatment System
Model Berson ,
3X2HGS-200
Depreciation
$73,000; annuity 15 years, 7%
Energy Consumption
61,325 kWhr for UV radiation
7,700 kWhr for headless
Replacements
6 UV-bymers
2 Quartz tubes
Total Costs
Costs: perm3
per kgal
$8,000
$3,200
$420
$1,350
$270
$13,240
$0.0054
$0.0204
Model Katadyn
2XGFM6
Depreciation
$80,000; annuity 15 years, 7%
Energy Consumption
1 0,946 kWhr for U V radiation
20,989 kWhr for headless
Replacements
20UV-bumers
4 Quartz tubes
Total Costs
Costs: per m3
per kgal
$8,700
$600
$1,1500
$2,900
• $1,000
$14,350
$0.0057
$0.0216
cents per kWhr in the Netherlands compared to 8.6 cents per kWhr in the United States). The average
annualized cost of ultraviolet disinfection systems in the Netherlands is about 2 c/Kgal for a flow of 1.8
MOD. The average annualized cost estimated for comparable systems in the United States is 4.4 c/Kgal.
3.7 SMALL NON^COMMUNITY WATER SYSTEMS FLOW REQUIREMENTS AND
COST IMPLICATIONS
Ultraviolet disinfection cost estimates for USEPA flow category 1 are estimated at $1,700 per year for an
ultraviolet light system delivering 40 mWs/cm2, and at $2,500 per year for an ultraviolet light system
delivering 140 mWs/cm2. As stated earlier, USEPA flow category 1 has a design flow of 24,000 gallons
per day and an average flow production of 5,600 gallons per day. Such design and average flow
assumptions are believed to be sufficient to satisfy me drinking water requirements of a population of 25
/to 100 persons served by a Community Water Supply (CWS) system. These flows and population
assumptions imply a minimum average water production of 56 gallons per person per day (based on a
population of 100).
While such assumptions are useful to USEPA in its evaluation of costs projected for community water
supply systems, it is unlikely that they will apply to many Non-Community Water (NCW) systems
according to some sources. The drinking water requirements for water use in many NCW systems are
expected to be much lower than those required in small CWS systems. The information obtained from
USEPA's Safe Drinking Water Information System (SDWIS) shows that approximately 91,000 ground
water NCW systems service a population of about 12 million. Exhibit 3-34 presents SDWIS data on
ground water NCW systems facility type for two population ranges.
UV Light Disinfection Technology in
Drinking Water Application—An Overview 3-39
Final—September 1996
-------
Chapter 3—Evaluation of Ultraviolet Light Technology Costs and Comparison
to Other Disinfection Processes
Exhibit 3-34. Ground Water NCW Systems Serving Two Population Ranges
Facility
(SDWIS Description)
Day Care Center
Dispenser
Homeowners Association
Hotel/Motel
Highway Rest Area
Industrial/Agricultural
Interstate Carrier
Institution
Medical Facility
Mobile Home Park
Mobile Home Park, Principal
Residence
Municipality
Other Area
Other Non-Transient Area
Other Residential Area
Other Transient Area
Recreation Area
Residential Area
Retail Employees
Restaurant
School
Sanitary Improvement District
Summer Camp
Secondary Residences
Service Station
Subdivision
Water Bottler
Wholesaler (Sells Water)
TOTAL
Number of Systems Serving a
Population of 25 to 50
Persons
280
-
-
1864
293
2059
11
437
122
346
.
,
4,840
946
314
10,450
7,609.
716
•
7,649
921
-
895
-
1,376
- •
-
42
41,170
Number of Systems Serving a
Population Greater Than 3,300
Persons
- ' •
, -
2
37
19
2
3
4
. . .
- '
-
18 . •.
8
-
22
68
6
-
10
14
-
3
• -
• 1
-
-
-
217
' Based on 9/25/96 SDWIS data for ground water NCW systems with treatment equipment '
UV Light Disinfection Technology in
Drinking Water Application—An Overview
3-40
Final—September 1996
-------
Chapter 3—Evaluation of Ultraviolet Light Technology Costs and Comparison
. .; to Other Disinfection Processes
Exhibit 3-35 provides a list of average water use per person at typical NCW facilities. If the USEPA flow
rate for category 1 (i.e., 5,600 gpd) were used in this context (for small NCW systems), then NCW
systems servicing carry-out restaurants or airports, could conceivably be providing enough water for 1,865
persons and 1,600 persons, respectively, which is far greater than the number of people served by that
flow category (25 - 100). • - . •
Exhibit 3-35. Typical Rates of Water Use in Non-Community Water Systems*
Facility
Airport —
Amusement Parks: - :
^H? wf ter enterta'inment, food facilities, flush toilets, and shower facilities
Without water entertainment, but with food facilities and flush toilets
Camps:
Construction •
Day with no meal served
Luxury
Resorts . -
Tourist with central bath' and toilet facilities
Cottages . : . r. —
Country Club , "- '- ~
Day Care Center : "
Department Store r • <
Factory •.'••• :
Highway Rest Area
Highway Rest Area with Minimarket : ~~~
Hospital — —
Lodging House/Tourist House
Medical Facility •
Motel
Office - .
Parks: —•
Overnight with Flush Toilets •
Trailers
Picnic Areas
Restaurant: - : —
Conventional
Carry-Out
Bar and Cocktail Lounqe • ,
Schools:' "~- :
With cafeteria, gymnasium, and showers
With cafeteria, but no gymnasium or showers
Without cafeteria, gymnasium, or showers
Side Road Store
Shopping Center ;
Theater :
Worship Places: • :
With day care facility, and no permanent residents
With abolition facilities, day care facility, and no permanent residents
With less than 25 permanent residents and day care facility '
With less than 25 permanent residents and no day care facility
Average Water Use
gal/person/day
3.5
40
10
10
50
15
100
50
35
50
40
4
10
10
100
40
10
40
15
25
40
10
9
3
.15
25
• 20
15
5
o
4
2
5
12
10
'Based in part on best professional judgment, Metcalf and Eddy, 1991 and Corbitt, 1990.
UV Light Disinfection Technology in
Drinking Water Application—An Overview
3-41-
Final—September 1996
-------
Chapter 3—Evaluation of Ultraviolet Light Technology Costs and Comparison
to Other. Disinfection Processes
•"""—^-^mm•••WMMWVMi^^_«M.^..'ma^^—m«H^MMIM^^^^^^-VM.
Water use rates shown in Exhibit 3-35 were compiled in part from Metcalf and Eddy, 1991, and Corbitt,
1990, and based in part on best professional judgment. Exhibit 3-35 suggests a need for developing new
flow methodologies for USEPA treatment cost analyses addressirig various types of NCW systems.
3.8 CONCLUSIONS
Based on the cost estimates presented in this chapter, ultraviolet light technology is an economically viable
and feasible technology, particularly for small water systems. The costs of using ultraviolet light alone
(at a dose of 140 mWs/cm2 or less) to disinfect ground water are far lower than using ozone and more
economical than chlorination for flow categories 1 through 4 (design flow 0.024 to 0.65 MGD). The costs
of using ultraviolet light alone at a dose of 40 mWs/cm2 are far lower than using ozone or chlorine
(hypochlorites) for primary disinfection for flow categories 1 through 5 (design flow 0.024 to 1.8 MGD).
The costs of chlorination, used in this chapter for comparison purposes, do not include the additional costs
incurred to cover the new requirements under Article 80 of the Uniform Fire Code (UFC) of 1991. These
new requirements include additional equipment to handle accidental release of chlorine gas or chlorine
dioxide and its onsite production components (where used) and emergency power sufficient to operate
chemical scrubbing.equipment. The costs associated with these requirements can represent as much as
25 percent of the total capital costs for small systems using chlorine gas or chlorine dioxide for
disinfection (WERE, 1995).
The costs of using ultraviolet light (at a dose of 140 mWs/cm2 or less) for primary disinfection in
combination with chlorination for secondary disinfection to disinfect ground water are lower than the costs
of ozonation and chlorination for flow categories 1 and 2. Ultraviolet disinfection costs, at a dose of 140
mWs/cm2, plus the costs of chlorination for residual disinfection, are comparable to ozonation costs for
USEPA flow categories 3 and 4 and higher than the costs of ozonation and chlorination alone for USEPA
flow category 5. Ultraviolet light disinfection costs at 40 mWs/cm2 plus the costs of chlorination for
residual disinfection are comparable to the costs of chlorination for USEPA flow categories 3 through 5
and are comparable to the costs of ozonation for USEPA flow categories 4 and 5 and lower than the costs
of ozonation for USEPA flow category 3. Also, it is concluded that rationale are available to justify use
of an alternate flow regime and, therefore, alternate cost estimates that would better fit in the analysis of
non-community type water systems. v
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Chapter 3—Evaluation of Ultraviolet Light Technology Costs and Comparison
- •' • '• - to Other Disinfection Processes
3.9 REFERENCES
ANSI/NSF (1991). American National Standards Instimtl/Natibnaf Sanitation Foundation International
Standard Number 55, Ultraviolet Microbiological Water Treatment Systems.
Chen, C.L. and Kuo, J.F. (1992). UV Inactivation of Bacteria and Viruses in Tertiary Effluent
Presentation to the DHS UV Disinfection Committee on Research at the County Sanitation Districts of
Los Angeles County. (As cited in WERF, 1995) .
CH2M HILL (1992). UV Disinfection Pilot Study - Rapid Infiltration/Extraction (RIX) Demonstration
Project. Prepared for Santa Ana Watershed Project Authority, City of San Bernardino, City of Colton
(As cited in WERF, 1995) -.-'..
Corbitt, R.A. (1990). Standard Handbook of Environmental Engineering. McGraw-Hill, Inc.
DPRA (1993). Small Water System By-products Treatment and Disposal Cost Document. Draft Final
Prepared for USEPA OGWDW.
ENR (1995). "Construction Cost Index History 1907-1995:" Engineering News Record, March 27,1995.
p. 80. ' .'-.'.,
Harris, G.D., et al. (1986). "UV Inactivation of Selected Bacteria and Viruses with Photoreactivation of
the Bacteria." „ Water Resources, Vol. 21, pp. 687-692.
Huck, P. (1989). "Reduction in Organic Levels and Disinfection Demand by Slow Sand Filtration in
Western Europe." Drinking Water Treatment Small.System Alternatives. Toft, T.obin, and Sharp, editors
New York: Pergamon Press, pp. 77-94. . "
Kraithof, J.C., van der Leer, R.C., and Hijnen, W.A.M. (1992). "Practical Experiences With UV
Disinfection in the Netherlands." Aqua, Vol. 41,"No! 2, pp. 88-94.
A . • , ••*.• =
Lund, V. and Orrrierod, K. (1995).' The Influence of Disinfection Processes on Biofilm Formation in
Water Distribution Systems. Water Research, Vol. 29, No. 4, pp. 1013-1021.
Metcalf and Eddy (1991). Wastewater Engineering: Treatment; Disposal and Reuse. 3rd Ed. McGraw-
Hill, Inc.
NWRI (1993). UV Disinfection Guidelines for Wastewater Reclamation in California and UV Disinfection
Research Needs Identification. National Water Research Institute, pp. 1-28.
PPPI (1995). "Survey of Current Business." Producer Prices and Price Indexes, Vol. 75, -No. 8. U.S.
Bureau of Labor Statistics, U.S. Department of Commerce. .
USEPA (1983). Microorganism Removal in Small Systems. Office of Drinking Water EPA 570/9-83-
012. . ,
USEPA (198,9). Technologies for Upgrading Existing or Designing New Drinking Water Treatment
Facilities. .Office of Drinking Water. EPA 625/4-89/023.
UV Light Disinfection Technology in
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Chapter 3—Evaluation of Ultraviolet Light Technology Costs and Comparison
to Other Disinfection Processes
USEPA (1992). UV Disinfection Technology Assessment. Office of Wastewater Enforcement and
Compliance. EPA 832-K-92-004.
USEPA (1993a). Very Small Systems Best Available Technology Cost Document. Drinking Water
Technology Branch, OGWDW, USEPA. Malcolm Pirnie, Inc.
USEPA (1993b). Technologies and Costs for Ground Water Disinfection. Drinking Water Technology,
Branch, OGWDW, USEPA. Draft Document, Malcolm Pirnie, Inc.
USEPA (1993c). Technical and Economic Capacity of States and Public Water Systems to Implement
Drinking Water Regulations—Report to Congress.
WERF (1995). Comparison of UV Irradiation to Chlorination: Guidance for Achieving' Optimal
Performance. Water Environment Research Foundation.
WWEMA (1992). Water and Wastewater Equipment Manufacturer's Association, Inc. Comments on the
Ground Water Disinfection Rule. ,
Zukovs, G., et al. (1986). "Disinfection of Low Quality Wastewaters by Ultraviolet Light Irradiation."
J. Wat. Pollut. Control Fed. Vol. 58, pp. 199-206.
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3-44
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CHAPTER 4. OPERATIONAL CASE STUDIES
4.1 INTRODUCTION
In this chapter, ultraviolet light operational case studies are presented. The purpose of this chapter is to
provide brief summaries of available information from public water systems (PWS) that have installed
ultraviolet (UV) treatment for ground water disinfection. The availability of information from operators
of PWS systems or the lack of it provides insight into the practicality of using ultraviolet treatment.
Operators' information provides an opportunity to assess actual field experiences. Such assessment helps,
., in determining the degree and level of operation and maintenance this technology requires and provides
a realistic estimate of the expenses incurred by various communities to obtain and maintain an ultraviolet
system. -
In general, case studies indicate actual performance evaluation of the technology investigated, and indicate
realistic operation and maintenance problems for specific site conditions. Ultraviolet light technology .
application case studies also serve as an indicator for the acceptance or rejection of technologies that are
not well established, (or accepted by the scientific community or by the USEPA as a reliable technology)
to disinfect drinking water.
The case studies also may serve as indicators of the price small and often rural and isolated communities
are willing to'pay in the absence of State mandates for ground water disinfection. Another aspect of these
case studies is reported water use and production capacities in Transient Non-Community (TNC) arid Non-
Transient Non-Community (NTNC) water systems. The information reported by the operators of very
small TNC and NTNC systems shows that average water production appears to be much less than the
water consumption generally assumed in calculating treatment costs for Community Water Systems (CWS)
with similar population sizes. In addition to the ultraviolet light application in drinking water case studies,
this chapter also presents information collected from two ultraviolet light equipment service contractors
and a general discussion of ultraviolet units costs as demonstrated from the case studies and the design
flows of the investigated systems. Finally, this chapter presents suggested criteria for the use of ultraviolet
light units based on the interviews conducted to develop the case studies.
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The case studies presented from the State of New Jersey are for TNC and NTNC ground water. The case
study presented from the State of Oregon is a ground water CWS case study. A surface water case study
from the State of Montana and a brief case study from the State of Maryland where ultraviolet light is
used in a wastewater reclamation facility are presented. Moreover, one case history from the Netherlands
is presented.
To obtain information about drinking water systems that have installed ultraviolet light technology for
disinfection, the USEPA contacted drinking water program supervisors in four states (New Jersey,
" - > '
Montana, Oregon, and California). The State of New Jersey provided the name, address, and contact
person telephone number for twenty drinking water facilities that use ultraviolet light for primary
disinfection (Monaco, 1996). The State of Oregon provided information on the single public water system
that uses ultraviolet light for primary disinfection and chlorine as a secondary disinfectant. The State of
California informed the USEPA that they are not aware of any PWS systems that have installed an
ultraviolet light unit to disinfect drinking water. The State of Montana provided the telephone number
of the contact person in a PWS that uses ultraviolet light for primary disinfection.
Apparently there are many private non-community water systems that use ultraviolet light for disinfection
in the State of Oregon1 and in the State "of New Jersey2. These private/water systems include private
homes and small shops. Interviews, conducted with two water treatment units service contractors,
presented in this report, show the extent to which very small communities, families and individuals are
willing to go to have safe disinfected drinking water available on demand.
Most of the information presented in this chapter was collected through telephone interviews with systems'
managers or operators. The information provided here on the CWS that uses ultraviolet light for
disinfection in the State of Oregon was collected by the State. The information collected via telephone
interviews with system operators or through field visits by State representatives were based on a
questionnaire that covers basic information on operation and maintenance, system costs and water quality
parameters and compliance. The questionnaire is presented in Appendix C.
'Personal communication with Mr. Gary Burnett and Ms. Kari Sails of the Oregon Drinking Water Program
(5/20/96).
Personal communication with Mr. Pete Cicalese an ultraviolet light equipment service contractor (fi/27/96).
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Newly proposed ultraviolet light use regulations developed by the State of New Jersey are included in
Appendix D. Also, Appendix D includes drinking water regulations from the State of Utah, and the U.S.
Department of Health, Education, and Welfare (DHEW) [now the Department of Health and Human
Services (HHS)] 1966 Policy Statement on the use of ultraviolet light for drinking water disinfection.
While theproposed regulations for the use-of ultraviolet light in the State of New Jersey require the same
minimum dose (16 mWs/cm2) mandated under current State regulations, the new regulations specify some
construction and light monitoring requirements (New Jersey, 1995). The ultraviolet light disinfection
application regulations in the State of Utah appear to be modeled oh the DHEW regulations. .
4.2 CASE STUDIES FROM THE STATE OF NEW JERSEY
The case studies,presented from the State of New Jersey cover mainly TNC and NTNC systems and
reflect satisfaction with ultraviolet use for disinfection. The systems in these case studies draw their water
from ground water sources. All ultraviolet light units were reported to operate 24 hours per day and the
majority had one unit in operation without a backup unit onsite. These case studies include a TNC system
that has been in operation for more than 10 years. Another case study presents a TNC system that
switched from chemical disinfection to ultraviolet disinfection.
Examining the information collected from the case studies conducted in the State of New Jersey revealed
that ultraviolet, units receive little attention and require very little supervision. On the other hand
operators of the PWS do not know much about the technology or the units that were purchased and
installed, Basic water quality parameter information is typically not kept onsite and certain parameters
that could affect.the disinfection efficiency of an ultraviolet unit such as iron or turbidity had never been
tested. Very few operators know the minimum ultraviolet dose their unit could provide. Not a single
PWS operator or contact person complained about operation and maintenance costs. All contacted persons
praised the minimum service time ultraviolet units require and how practical it is to use such a technology.
All the persons who had experience with chemical disinfection equipment complained about equipment
monitoring and service time and costs.in contrast to ultraviolet treatment operational requirements. In
addition, it appears that in most of these systems installation costs were very minimal, as were engineering
requirements and site modification.
4.2.1 PWS in Phillipsburg, New Jersey
The public water supply system in Phillipsburg, New Jersey, serving about 30 persons, installed its
ultraviolet light disinfection unit in October 1995. The age of the majority of the population served is
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above 47 years (range 47 years to 98 years). The disinfection capacity of the. unit, at 30 mWs/cm2- is 20
gpra (29,000 gpd). The system has no backup unit and no storage capacity. The reason given for
favoring ultraviolet disinfection over chlorination is the dislike of chlorine taste and that in ultraviolet
treatment, chlorine and chemicals do not have to be added to drinking water. The unit is equipped with
a 5 micron filter, a light emitting diode, a sound alarm and a manual wiper. The ultraviolet light unit is
a closed ultraviolet light unit, made in Vermont and came with a 1-year warranty on parts. According the
manager of the system the ground water source is of "good quality". There are no turbidity measurements,
but according to the contact person, the ground water is clear and ,the turbidity may be assumed to be
"very low". There have been no conform outbreaks from the time the system was installed. Once a week,
in a few seconds, the system manager would manually clean the bulbs by pulling and pushing the arm of
the manual wiper a few times. No detergents or chemical agents are used in the weekly cleaning. During
the annual service, the ultraviolet light bulb is changed (i.e., once every 9,000 hours) and the unit is
t
thoroughly cleaned. The capital cost of the system was $2,100 including engineering, installation and
instruction. The operation and maintenance cost is estimated at $90 to $100 per year. /
4.2.2 TNC in Lebanon, New Jersey
The ultraviolet light disinfection equipment at this TNC in Lebanon, New Jersey was installed near the
end of the year 1994. Before installing the present unit the facility had an old ultraviolet light unit that
could not be maintained any longer. The present unit serves an average of 50 persons per day. The
owners of the facility estimate water consumption at 200 gpd. The unit's design flow is 15 gpm (21,600
gpd). Part of the facility that uses the unit is a restaurant. The negative effect of chlorination on water
taste and the operation and maintenance requirements for chlorinators favored the use of ultraviolet light
technology over traditional chemical disinfection technology. The system has a storage capacity of 80
gallons. The unit delivers a minimum dose of 17 mWs/cm2 assuming water with an absorbance coefficient
of 0.1 (a level between an absorbance coefficient of 0.06 for municipal drinking water and ah absorbance
coefficient of 0.15 for sea water). • .
The unit, manufactured in Pennsylvania, is equipped with a mechanical wiper, a sound alarm system, and
one ultraviolet lamp, and is made out of stainless steel. It came with a 1-year warranty. Water tests have
shown no presence of total coliform in the finished water. The person who services the system said that
he has not noticed any biofilming in the storage tank or the pipes connected to the ultraviolet light, unit.
The unit is cleaned with synthetic detergents and alcohol. The owners of the facility say that once a year
the bulb is changed and the full service cleanup takes about 1/2 an hour. The capital cost was estimated
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at $2,000 to $3,000 (including engineering and installation). The operation and maintenance is contracted
out. The operation and maintenance costs for the system are estimated at $500 per year including all
quarterly water sampling, analysis, testing and reporting requirements.
4.2.3 TNC in Branchville, New Jersey
The ultraviolet light system was installed in 1990-1991. It serves an average population of 40 per day.
Ultraviolet light was considered because of its effectiveness against nuisance microorganisms and because
it does not add any taste to the water. Before installing the ultraviolet light unit, disinfection was available
through an iodinator. The use of chemical disinfection was not satisfactory because of its effects on the
taste of the beverages served at the facility such as tap soda. In addition, some operation and maintenance
problems associated with the chemical disinfection unit, such as measuring and applying the right chemical
dose, brought the owner to the decision of installing an ultraviolet unit with the promise that it requires
little attention. The unit was manufactured in the United States and is equipped with one light bulb and
a sound alarm system. The system has a storage capacity of 40 gallons.
Turbidity levels and iron levels are unknown. However, for some time the system was. equipped with a
softener which at the time of the interview had not been, used for over a year and a half. There were no
eoliform or other microbiological outbreaks;
Service of the ultraviolet light unit is contracted out to the firm that installed it. The unit is serviced once
per year. The service includes cleaning the unit and replacing the light bulb. The annual service of the
unit takes about 20 minutes. As stated earlier the unit was put in service 5 to 6 years ago, nevertheless,
no diodes, ballasts, or sleeves have been replaced. Moreover, the owners of the facility have not noticed
any biofilm accumulation in the pipes or the storage tank. The cost of the system including engineering
and installation was $1,500. The operation and maintenance cost is estimated at $125 to $150 per year.
4.2.4 NTNC in Harmony Township, New Jersey
The ultraviolet light unit at this system was installed in the winter of 1994. The unit is a closedrtype unit.
The treated water is used by 20 employees for showering and washing only. The owners of the facility
provide bottled water for drinking. The average water consumption is about 10,000 gallons per day. The
ultraviolet light unit has the capacity of treating 24 gallons per minute (34,560 gallons per day). Water
treatment includes an activated carbon filter installed before the ultraviolet unit. The facility where the
ultraviolet unit is installed is a chemical manufacturing facility. The ultraviolet light unit was
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manufactured in New Jersey and came with a 1-year warranty on parts. The-unit is equipped with two
ultraviolet light bulbs, a sound alarm system and mechanical wipers. The quarterly tests for coliform
bacteria in treated waters show an absence of coliforms. ,
i
The unit is serviced once every 6 months. It takes about one person-hour to clean and service the unit.
Iron deposits are removed using dilute acids. The installer did not provide any special training for the
employee who services the unit. Bulbs are replaced when ultraviolet light emission is at 50 percent of
the maximum power. The .caretaker of the unit could not provide any information on the intensity of the
unit or its dose. Installation and capital costs are not known, however, the operation and maintenance
costs are estimated at $1,000 per year.
4.2.5 TNC in Ringoes, New Jersey '
This TNC system in Ringoes, New Jersey, is a deli store with 12 regular employees. It serves about 300
persons per day. The ultraviolet unit was installed in 1985. .The reason for selecting ultraviolet light
treatment over chemical treatment is unknown to the current owners. The unit is a closed-type Unit
equipped with one ultraviolet light bulb and a water meter. The unit is not equipped with a light or a
sound alarm system or any other accessories. The current owners do not know where the unit was
manufactured and could not tell whether it was covered by any form of a warranty. The system has a
storage capacity of 50 gallons. The water is pre-treated by means of a "paper-like" filter of unknown pore
size. This filter removes some silt and sediments. The operators could not provide any information on
the ultraviolet light intensity the unit is capable of delivering.
The unit is cleaned once a year. The cleaning is done manually and the unit is flushed with a chlorine
solution. During the past 10 years there has been one positive coliform test, in 1992. The owners
attribute the positive coliform test to the fact that the ultraviolet light bulb was not changed in a year and
half. '.'..'.'
The owners could not provide any information on capital, installation and operational and maintenance
costs. However, the owners expressed satisfaction with the performance of the unit as it requires very
little attention on their part and its service is contracted out to a plumbing company.
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4.2.6 NTNC in Ringoes, New Jersey
According to the contact person at this PWS, this system provides water to about 30 residents in an
apartment building, and a store with 3 employees which serves about 50 to 100 customers per day. The
system was installed 7 years ago. The new owner does not know why ultraviolet light was selected by
the previous owner. According to the store manager where the ultraviplet light unit is located, the
ultraviolet light system is an open-type unit. The'unit is installed in a storage room. The contact person
knows that the unit is working by looking at the blue light coming from the unit (ultraviolet light units
do emit some gray-blue visible light). Microbiological tests are conducted by the county health
department. The new owner did not know that the unit needs periodic service such as changing the
ultraviolet light bulbs or occasional service such as cleaning. According to the contact person there is no
sign at the door where the ultraviolet light unit is located to warn the users of that room that looking
directly at the light emitted from the ultraviolet lamps is hazardous and could cause temporary and
permanent eye injury. Store employees, where the unit is located, did not appear to be warned in any
manner against gazing at the unit with its serene blue light.
-.-. ' f •'.--"-.
4.2.7 NTNC in Stewartsville, New Jersey
This NTNC system is located in a metal work manufacturing facility. The population served is 50 persons
per day. The capacity of the ultraviolet unit is 20 gallons per minute (29,000 gpd). The intensity and
dose of the unit are not known. The unit was installed, in 1991, when for the first time the ground water
source tested positive for cohTorm bacteria. Because the water source is contaminated with hightevels
of nitrates and nitrites, the treated water isjised only for washing, sanitation and toilets flushing.
According to the contact person at the facility, the source of ground water contamination is a 1.5 million-
chicken farm, located about 2 miles away from the facility. According to the contact person, the well
water is tested by the county department of health for microbial contamination once every 6 months and
possibly for nitrates/nitrites. The ultraviolet unit installed 5 years ago was manufactured in the United
States, it contains two ultraviolet light bulbs and came with a 2-year warranty ;on parts. The system does
not have any storage capacity. There has been no positive coliform test after the installation of the unit.
Twice a year, the unit is fully serviced. This service includes replacing the bulbs and cleaning the unit
with detergents. The full service is done by one person and it takes several hours to complete. The unit
cost including engineering and installation was about $1,000. The operation and maintenance costs are
estimated at $200 per year. _
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4.2.8 TNC Ground Water System in Washington, New Jersey
Merrill Creek Visitors Center in Washington, New Jersey, is a transient non-community water supply
system. The system has three sites where ultraviolet light is used for ground water disinfection. The sites
include a visitors center, a rental property (guest houses), and a pump house.
The Center has four closed ultraviolet light units—three units each with one bulb and one unit with four
bulbs (guest houses site). The operator could not provide information on the dose or intensity used. The
population served is estimated by the operator to be between 5,000 to 10,000 per year. The system is not
equipped with an alarm or telemetry system. The system is a U.S.-made system, -manufactured in
California. It was -installed 8 years ago. There is no distribution system and the system has no storage
capacity. Also, chlorination is not used as a secondary disinfection.
There are no turbidity measurements taken. There have been no conform outbreaks and no biofilm
formation in the pipes within the buildings. The system uses a pH adjuster on only one site and applies
hardness and iron removal treatment prior to ultraviolet treatment. Microbiological samples are taken on
a monthly basis. Cleaning of the units is performed once HPC reaches 100 CFU/ml. If the HPC count
remains high, the light bulbs are replaced. Also, light bulbs are changed annually; during the past 8 years,
only one faulty ballast was changed; and no diodes have been changed. The system is not equipped with
wipers or ultrasonics. Cleaning of units occurs once every 6 months and it takes 2 hours to finish the
cleaning process. The operator mentioned that over the last 8 years only two quartz sleeves were broken
during maintenance.
The estimated O&M costs are $100 to $200 per year, and the capital costs for one of the units, including
pH adjuster and softener, were approximately $4,000 to $5,000 (personal communication with the
supervisor, 1996).
4.3 CASE STUDIES FROM THE STATES OF OREGON, MONTANA, AND
MARYLAND
The case study presented from the State of Oregon covers a ground water CWS. The case study reflects
satisfaction with ultraviolet use for primary disinfection. The four ultraviolet units installed in this CWS
operate 24 hours per day. A close look at the information presented in this case study shows that the
theoretical flow capacity of this CWS system is 100,800 gallons per day or 70 gpm. The theoretical
disinfection capacity of the installed ultraviolet units is even greater at 115,200 gallons per day. The
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USEPA assumed design flow category for a CWS population of less than 100 persons is 24,000 gallons
per day or 16.67 gpm. The USEPA average flow category for a CWS population of less than 100 persons
is 5600 gallons per day or 3.89 gpm. The ratio of USEPA design flow category to the USEPA average
flow is 4.3. Some authorities use a factor of three for instantaneous peak factor (i.e., maximum water
demand/average water demand per day) (Masschelein, 1992). Using the USEPA peak factor figure to
determine average water demand would yield 245 gallons per capita per day (population served 96). An
average water demand of 52 gpd is normally considered to calculate water demand in very high-standard
residential areas (Masschelein, 1992). The case study from Montana is a Ranney-filtered drinking water
application. The case study from Montana reflects satisfaction with ultraviolet application for primary
disinfection. The case study from Maryland covers a water reclamation facility that uses an open channel
ultraviolet system. The case study from Maryland reflects satisfaction with ultraviolet application for
treated wastewater disinfection. .
4.3.1 Villadom Mobile Home Park CWS In Umatilla County, Oregon
Only one public water system in Oregon has installed ultraviolet light for primary disinfection, with '
chlorination providing secondary disinfection.' This community water system, Villadom Mobile Home
Park is located just north of Milton-Freewater, in Umatilla County. The system has a well with a capacity.
of 70 gpm, and serves a population of 96.
Ultraviolet light was first considered at Villadom in 1990, but was-not chosen as a disinfectant until June
of 1994 when a series of samples (May and June) tested positive for total coliform. With no existing
disinfectant capabilities, the owner decided to install bpth an ultraviolet light system, and a liquid sodium
hypochlorinator to provide the required residual. Household bleach (5.25%) is used and diluted 1:5. The
owner chose not to use chlorine as the main disinfectant due to the undesirable taste and high maintenance
needs.
The ultraviolet light system installed, Water Soft model UV-20F, is a stainless steel cylinder with a space
requirement of 13 x 7 x 36 inches per unit. The system uses four units in parallel, each preceded by a
120-mesh screen filter, to provide a maximum capacity of 80 gpm (note: this capacity exceeds well
capacity). The shipping weight of each unit is 23 pounds. The dose provided by each unit is 30
mWs/cm2. Each unit has a capacity of 20 gpm, and is equipped with' an automatic shut-off valve
("Failsafe" brand) in case of a malfunction or a weak bulb. The shut-off valve is also hooked up to an
alarm. The manufacturer location is unknown, as Water Soft purchased the product and marketed it as
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a Water Soft product. Pump and Drilling Supply, located in Wilsonville, OR, was the distributor for these
units, but the line has been discontinued. The distributor offered a 1-year warranty, but overall the CWS
system operators have not found any major problems with the product.
Villadom Mobile Home Park has a storage capacity of 75 gallons, from three pressure tanks. The feed
pump for chlorination is a 28 gpd capacity Mec-a-Matic, with a theoretical dosage of 1.6 ppm. However,
at the time of the field visit, a chlorine residual was barely detected (<0.2 ppm). The owner was not
available for further questioning.
Turbidity levels for this system are not known. The source is a 48 foot deep well, and sand entering the
treatment system has been an occasional problem in the past. No problems other than complaints about
the aesthetic water quality were experienced. There is no noticeable iron in the source water, although
there is no record of any lab analysis results. All monthly tests for coliform bacteria after June 1994 have
been negative. The chlorine residual is not routinely measured at the time of sample collection, so the
level of protection provided by chlorine is unknown. No increase in biofilm formation has been noticed
in the PVC distribution pipe. No other microbiological problems are known.
The pre-filters would be cleaned only when sediment builds up, and this has not been necessary in the 2
years the system has been in operation. The ultraviolet units are cleaned with alcohol whenever the bulb
is changed. With the Failsafe feature, the unit ceases operation if the ultraviolet light bulb is out or
weaker than the set dosage. The local supplier is on call for any operation or maintenance needs. The
supplier attended a 4-day "Water Soft" seminar covering all aspects of the ultraviolet light units in order
to be able to sell and service them. He changes the light bulb at least every year, and cleans the glass
sleeve at that time. It takes one person about an hour and a half to accomplish both of these tasks on all
four units. He has never broken a sleeve or bulb during cleaning or changing, though he says it is
common with inexperienced private homeowners. The sleeves, diodes, and ballasts have not yet needed
to be replaced, and the safety valve would shut the unit off should anything go wrong. As far as
calibration, the only adjustable parameter the service person knew of was the capacity, which is designed
for 20 gpm per unit but could be lowered using the flow control valve,
The cost of the ultraviolet light system was about $20,000. Each 20 gpm unit costs $5,000, including
engineering and installation. Operation and maintenance costs are as little as $550 per year, which
includes materials and labor (about an hour and a half to change, the bulbs and clean the sleeves).
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4.3.2V Fort Benton, Montana
The city of Fort Benton, Montana, obtains drinking water from the Missouri River. The filtration plant,
which is more than 20 years old, was in need of upgrading due to coliform bacteria outbreaks. Rather
than building a new filtration plant, the city built a new 0.088 m3/sec (2 MOD) treatment plant in 1987.
Water is drawn through Ranney collectors installed 6 to 7.5 m (20 to 25 ft) below the river bed, a system
that allows the river bed to naturally filter the raw water. Turbidities of water entering the treatment plant
average 0.08 NTU. No Giardia cysts have been found in the flow from the Ranney collectors.
The water is treated with ultraviolet radiation fof primary disinfection, then chlorinated for secondary
disinfection. An applied chlorine dosage of about 1 mg/L is used. The entire water treatment system is
housed in a 2.97-m2 (32 sq ft) building.
The ultraviolet disinfection system consists of six irradiation chambers, two control cabinets with alarms,
chart recorders, relays, hour-run meters, lamp and power on-lights, six thermostats, electrical door
interlocks, mimic diagrams, and six ultraviolet intensity monitors measuring total ultraviolet output. Each
irradiation chamber contains one 2.5 kW mercury vapor, medium-pressure arc tube, generating ultraviolet
radiation including radiation at 253.7 nm.
i " . - •..,.• . . - • • - •
The initial ultraviolet dosage is 41 mWs/cm2 at maximum water flow of 104 L/S (1,650 gal/min) through
each irradiation unit. Expected arc tube life is 4,500 operating hours, providing a minimum .ultraviolet
dosage of 25 mWs/cm2 at 253.7 nm. These conditions were assumed to reduce concentrations of
Esckerichia coli organisms by a minimum of 5 logs (10s reduction) (USEPA, 1989).
The system (made in EnglandXis equipped with a telemetry control system and fully automated backup
system. Each bank of three irradiation chambers has two units on-line at all times, with the third unit
serving as backup. In the event that the ultraviolet intensity drops below acceptable limits (20 mWs/cm2
in any of the chambers), the automatic butterfly valve on the standby unit will open. The alarm system
also is activated if ultraviolet intensity drops below acceptable limits in any of the chambers. The
ultraviolet alarm system is interfaced with an automatic dialer and alarm system.
In 1987, total equipment costs for the six-unit ultraviolet irradiation system with butterfly valves were
$74,587 (USEPA; 1989). The current population served by the system is about 1,700. No outbreaks of
UV Light Disinfection Technology in
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Chapter 4—Operational Case Studies
conform bacteria have occurred since the installation of the ultraviolet unit.in 1987, and the system is
cleaned once a year (personal communication 'with superintendent, 1996).
4.3.3 Mayo Water Reclamation Facility, Maryland
In the Greater Washington, D.C. area, the Mayo Water Reclamation Facility (that treats gray water before
discharging it into a river) uses ultraviolet light for disinfection. The Mayo Water Reclamation Facility
is located in Anne Arundel County on the Eastern Shore of Maryland, near the town of Edgewater. The
ultraviolet disinfection system is an open-channel system that has been in operation for 7 years. The
system was designed and built by Trojan and disinfects a peak flow of about 0.5 MOD. The BOD levels
are about 90 mg/1, and the suspended solids levels are about 60 mg/1. The effluent from the ultraviolet
disinfection system is discharged directly to Rhode River. The dose applied at the Mayo water
reclamation facility could not be verified by the current operator.
An early problem in operating the system was rapid algae growth in the ultraviolet unit. The problem was
corrected by covering the open channel and preventing the sunlight from reaching the water. The
operation and maintenance crew clean the ultraviolet lamps weekly with diluted HC1 solution. The unit
is equipped with an intensity meter to indicate when the lamps must be- cleaned and an alarm system to
indicate a lamp failure. Although the manufacturer recommended that lamps be replaced once a year,
according to the operator, some lamps that were put in operation a few years ago are still functioning
satisfactorily (personal communication with operator, 1995).
4.4 CASE HISTORY, LANDEUS WATER TREATMENT PLANT IN THE
NETHERLANDS
Kruithof et al. (1992) presented a ground water treatment plant case history from the Netherlands. The
case history shows that ultraviolet light was used at the Landeus water treatment plant following an
outbreak of coliforms and Escherichia coli bacteria in 1980. In the 5-year period (1981-1985) following
the installation of an ultraviolet light disinfection system, Escherichia coli tested positive in the finished
water five times of 200 measurements. Simultaneously, the source water total coliforms were detected
116 times and Escherichia coli were detected 65 times. The reason for Escherichia coli presence in the
finished water (five times out of 65 Escherichia coli detection in source water) was low ultraviolet
radiation dose. In three cases, the cause of the low dose was a malfunctioning ultraviolet light intensity
monitor showing a higher dose than the actual. In the other two cases, the dose was experimentally
reduced to 23 mWs/cm2, a level that did not eliminate all coliform bacteria. In the 6 years that followed
UV Light Disinfection Technology in
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Chapters—Operational Case Studies
the year 1985, no Escherichia coli outbreaks occurred. The no-outbreak period came following more
accurate monitoring and routine lamp replacement at 60 percent (24 mW/cm2) of the original intensity (40
mW/cm2). No capital or operation and maintenance coks were reported by Kruithof et al. (1992).
However, Kruithof etal. (1992) reported costs associated with the use of ultraviolet light for drinking
water disinfection for other treatment plants in the Netherlands. The costs reported by Kruithof et al.
(1992) are presented in chapter 3.
4.5 PERSPECTIVE OF TWO WATER TREATMENT UNITS SERVICE
CONTRACTORS
As the case studies have revealed, many ultraviolet units operation and maintenance services are contracted
out to professional contractors or plumbing firms, and these are typically the same firms that market and
, install the units. This indicates that some ultraviolet units are sophisticated enough to warrant professional
assistance particularly when thorough cleaning is required. Two contractors were interviewed to provide
information that the contact persons could not provide about their systems' ultraviolet light unit.
Moreover, the contractors were asked two specific questions that raised some concerns about possible
environmental impacts of spent ultraviolet light bulbs, and about actual operation and maintenance costs.
The first question was about the fate of the spent bulbs." The second question was about how often bulbs
and sleeves get broken when being installed or replaced. The fact that ultraviolet light bulbs contain some
mercury, and that at least in one State (California) wastewater treatment plants utilizing ultraviolet
technology for disinfection are required to recycle spent bulbs, prompted the first question. The second
question was in response to claims that the expensive ultraviolet light bulbs and sleeves often break during
cleaning and replacement. '
The interviewed contractors, in New Jersey and the other in Umatffla county, Oregon, said that ever since
they started servicing ultraviolet units, they have not broken any ultraviolet light bulbs. The contractor
in New Jersey said that his firm services well over 150 ultraviolet units per year. The contractor admitted
to breaking one sleeve 3 years ago. Both contractors indicated that bulbs and sleeves do break if an
inexperienced person like a homeowner tries to do the job himself or herself. Usually people try to do
the replacement themselves in the first or second year of installing the unit. Then when the expensive
bulb breaks they ask for help. :
The contractor in New Jersey said that spent ultraviolet light bulbs are disposed of along with regular
trash. The contractor in Oregon said that spent bulbs are disposed of along with other toxic substances
UV Light Disinfection Technology in
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Chapter 4—Operational Case Studies
in a toxic wastes landfill. When asked if spent bulbs break in the shop or before being disposed of during
transportation or storage, the contractor in Oregon said that never happens because the bulbs come in well
padded corrugated cardboard boxes. When'asked if he thinks that spent ultraviolet light bulbs constitute
an environmental hazard his response was that the amount of mercury in the bulbs is less than the amount
one would find in the old electric heating and air conditioning switches installed in homes, therefore the
pollution risk in his view is small.
The contractor in New Jersey estimates his service charge at an average of $175 per Unit, with one light
bulb per year. This includes changing the bulb and the "O" rings, and cleaning the unit. The contractor
in Oregon charges $46 per service call plus parts.
The contractor in Oregon services chlorinators also, including that used for secondary disinfection at the
ViUadom Mobile Home Park CWS. Servicing a chlorinator is time consuming and requires close
attention. The service includes checking and cleaning the valves once every 2 mpnths and testing the
chlorine level once per week. It also entails filling the chlorine tank and preparing the solution once every
3 days. His fees for these services are the same as those for servicing an ultraviolet unit (i.e., $46 per
service call plus materials with each service call lasting for about an hour). The contractor in New Jersey
also services chlorinators at private homes and very small private water systems! The contractors' remarks
- . ,._>_.
on chlorinators were similar to those expressed by the service contractor in Oregon adding that the service
requirements are cumbersome to private home owners and time consuming to the service worker.
Both service contractors indicated that they have not noticed any biofilm accumulation in pipes or storage
tanks and did not need to change diodes. According to the contractor in New Jersey, ballasts are changed
once every 4 years, mostly because of improper use or lightening. The contractors experience with the
industry indicates that the ultraviolet industry stands behind the quality of its products and the parts it
supplies.
4.6 COSTS OF ULTRAVIOLET LIGHT UNITS AND DESIGN FLOWS OF TNC
AND NTNC SYSTEMS AS REVEALED FROM THE CASE STUDIES
The costs of the ultraviolet light treatment units reported in these case studies reflect actual costs incurred
by these systems. The installed equipment costs for treating flows less than 100,000 gpd ($1,000 to
$5,000), vary greatly although the units provide similar disinfection power to almost similar flows. The
reported capital costs reflect the variance in price quotes obtained directly from.ultraviolet light unit
UV Light Disinfection Technology in .
Drinking Water Application—An Overview 4-14 Final—September 1996
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Chapter 4—Operational Case Studies
manufacturers and reported in Chapter 3 of this report. The same observation, can be made when looking
into the reported operation and maintenance costs ($90 per year per unit to $200 per year per unit). The
operation and maintenance costs reported in Chapter 3. of this report are comparable to those reported in
these case studies (the-operation and maintenance costs reported in chapter 3 of this report are higher
because they include power costs and other miscellaneous costs for ultraviolet units with higher dose
capabilities). None of the investigated PWS systems were equipped with telemetry equipment. The
benefit of equipping water systems troubled with microbiological and monitoring Violations is reported
in a case study from California (USEPA, 1995), In this case study installing telemetry equipment reduced
operation and maintenance costs by about 33 percent. This was in a rural California.system that was
plagued with bacteriological and monitoring violations. Installing telemetry equipment reduced the
required daily inspection visits to weekly visits, thus reducing the time required to operate and maintain
the system to 13 hours per month including travel time. '
The flows reported in the case studies above show that many small systems have some storage capacity.
Having some storage capacity helps in reducing the peak demand on the treatment plant. This reduction
in peak demand at the treatment plant also translates into installing equipment with smaller capacity and .
hence lower capital and operation costs. The case studies also show thatjn small systems, using chemicals
to maintain residual disinfection in the network might not be necessary. As stated earlier the flow
requirements for TNC and NTNC systems might not be the -same as those of CWS with similar
population. This area warrants further investigation as it bears heavily on treatment options and cost
' estimates.
4.7 SUMMARY OF FINDINGS
The presented case studies revealed important commonalities in general systems' features and in specific
operation and maintenance procedures. Examination of the information collected from the.case studies
shows the following:
• All the investigated systems have ultraviolet units with disinfection capabilities for flows that
exceed actual water' demand. The summary table presented below clearly shows that the per
capita water consumption availability atthese systems exceeds, by far, normal residential water
consumption demand. The reported estimate of average water consumption at the TNC PWS
in Lebanon, NJ is 4 gallons per capita per day while the system's conservative available
average demand capacity is at 100 gallons per capita per day. Installing equipment with'
appropriate capacity and having some storage capacity would certainly result in lower capital
costs and operation costs.
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Chapter 4—Operational Case Studies
• All ultraviolet units operate 24 hours per day. s .
• There are no backup units available onsite:
• Maintenance is contracted out.
• Operation and maintenance costs were not specifically raised as a concern.
• Installation costs are part of the equipment costs and site modification are either minimal or not
necessary. Space requirements are very small and the weight of a single unit is less than 25
pounds.
• Chemical and physical water quality parameters are often not known.
• No coliform violation occurred with ultraviolet treatment.
• No biofilming in networks pipes or reservoirs occurred.
• Operat6rs and users expressed satisfaction with the performance of the installed ultraviolet units,
and the simplicity of its operation and maintenance requirements.
• Sleeves and bulbs breakage was not specifically reported as a concern.
f
Exhibit 4-1 presents a summary table of ultraviolet light disinfection applications in drinking water based
on case studies.
UV Light Disinfection Technology in
Drinking Water Application—An Overview 4-16 Final—September 1996
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Chapter 4—Operational Case Studies
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Chapter 4—Operational Case Studies
4.8 SUGGESTED CRITERIA FOR THE USE OF ULTRAVIOLET LIGHT UNITS
BASED ON THE PRESENTED CASE STUDIES
Based on the interviews conducted with operators of public water systems using ultraviolet light to
disinfect drinking water or water for human consumption, the following requirements are suggested for
the use of ultraviolet units in small public water, systems:
• All units must be of the closed-type.
• Mechanical wipers and ultrasonic cleaners should be mandatory if water fouling agents such
as iron are present in the water entering the unit.
• Annual cleaning of the unit, at a minimum.
• Minimum set dose at any wavelength(s) within the 250nm to 270nm spectruni (this needs to
be decided by the work group).
• Automatic shutoff valve, flow control valves with shutoff triggered when light intensity falls
below the minimum set level.
• Sound and light alarm and-telemetry equipment if users or operators' are not close by.
• The unit body needs to be made of material that would not permeate or degrade under the
effect of ultraviolet light, such as high quality stainless steel.
• Testing the disinfection efficiency of the unit as a whole by means of bioassay or actinometry
before installation. Research might be necessary to determine whether recalibration of the
installed unit is necessary after years of service. Testing the unit's ballasts and diodes after
years of service ajso requires some research to determine the time span when such testing might
be necessary. ' . .
• Microbiological tests for ultraviolet treated finished water should include HPC tests. HPC
microorganisms may provide a better assessment of disinfection than the ultraviolet sensitive
coliforms. .
• Education of the users and the servicepersons about the hazardous compounds contained in the
components of the ultraviolet light unit and proper ways of disposing spent parts.
• When possible a backup unit should be available or at least one set of spare parts stored onsite.
UV Light Disinfection Technology in
Drinking Water Application—An Overview 4-18 Final—September 1996
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Chapter 4—Operational Case Studies
4.9 REFERENCES
Kruithof, J.C., Van der Leer, R.C., and Hijnen, W.A.M. (1992). "Practical Experiences with UV
Disinfection in the Netherlands." Aqua, Vol. 41, No. 2, pf>. 88-94.
Masschelein, W. J. (1992). Unit ^Processes in Drinking Water Treatment. Marcel Dekker Inc. New York!
Monaco Vince, (1996). Memoranda to Dr. Faysal Bekdash Sr. Environmental Engineer dated 4/18/1996
and 4/30/1996.
New Jersey, (1995). Regulations for Disinfection by Ultraviolet Light. New Jersey Register CITE 27
N.J.R 4112. November 6, 1995.
USEPA, (1995). Restructuring Small Drinking Water Systems. Options and Case Studies. Office of
Water. Washington D.C. EPA 810-R-95-002.
UV Light Disinfection Technology in
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CHAPTER 5. SUMMARY OF FINDINGS
This chapter summarizes the findings presented in the previous chapters. Sections 5.1,5.2, and 5.3 present
the main findings of chapters 2 and 3. Section 5.4 presents the main findings of chapter 4.
5.1 EFFICACY AND APPLICABILITY
The initial summary of findings presented below is based on the reviewed literature and information
provided by non-governmental organizations and ultraviolet light manufacturers. These findings are
presented in more detail in section 2.5.
• Ultraviolet light (at a 253.7 nm wavelength) is effective against a wide range of pathogenic and
nuisance microorganisms commonly found in ground water.
• The required inactivation dose of bacteria using ultraviolet light varies from one organism to
another and within the same species.
• GeneraUy, the order of disinfection resistance is as follows: bacteria (least resistant) < viruses
< bacterial, spores < protozoan cysts and oocysts (most resistant).
• Naturally, occurring microorganisms are more resistant to inactivation than-microorganisms
cultured in laboratories.
• Current contamination indicator surrogate microorganisms (total coliform bacteria, fecal
coliforms; EschericMa colt) are. more sensitive to disinfection by ultraviolet light than many
identified pathogenic microorganisms (including viruses) that are of concern in drinking water.
• Bacteriophage MS-2 inactivation data show that in a pilot study setting a 4 log reduction can
be achieved by an ultraviolet light dose of 93 mWs/cm2. Bacillus subtilis spores inactivation
data show that in a laboratory setting a 4 log reduction can be achieved using an ultraviolet
light dose of 60 mWs/cm2. A 60 mWs/cm2 dose is sufficient to cause more than a 5 log
reduction in poliovirus. A 50 mWs/cm2 dose is sufficient to achieve 4 log reduction in
rotavirus, which is more resistant to ultraviolet light than poliovirus and Hepatitis A virus.
• Two log reduction of Giardia lamblia is achieved at a dose of 180 mWs/cm2. A minimum of
3 log reduction of Cryptosporidium is achieved at a dose of about 8,750 mWs/cm2.
.• For water with a turbidity level of 5 NTU, 25 percent of the ultraviolet light is absorbed by
', turbidity-causing water constituents.
UV Light Disinfection Technology in
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Chapter 5—Summary of Findings
Additional advantages of using ultraviolet light for disinfection are: .
• Based on the current literature research, the use of ultraviolet light for water disinfection is not
associated with the formation of known toxic or non-toxic conventional treatment by-products.
If used for VOC destruction, no VOC emissions result.
• Unlike chemical disinfectants, there are no known risks associated with over-sizing the
disinfection chamber and there is no limit to the dose that could be applied in the disinfection
process. Overdesign of ultraviolet systems may be advantageous to cover transient periods
during which surface water may contaminate a source.
• Ultraviolet light is successfully being applied in the field to mitigate contaminated ground water
at Superfund sites. The literature search conducted for this report shows that even at low doses
of ultraviolet light (doses'that are normally applied in POU commercially available devices)
certain commonly used organic pesticides are slightly reduced.
• Ultraviolet light disinfection systems are very practical tools for upgrading and retrofitting small
systems requiring small space with minimal or no construction work.
• Ultraviolet light disinfection systems require no storage of hazardous material.
• No onsite smell and no final water product smell.
• Very little residence time.
• Taste is not altered (only improved) with the destruction of some organic contaminants and
nuisance microorganisms. .*••
• Minerals in water are not affected.
• No or little (disposal of spent lamps or obsolete equipment) impact on the environment (some
States require recycling of ultraviolet lamps). -'
The Dutch waterworks guidance on the use of ultraviolet shows that if both the number of microorganisms
and AOC concentrations are low (no definite figure given), then post-disinfection can be omitted
completely (ultraviolet light application fits here as an additional safety measure). In a typical Dutch
waterworks, this occurs when multiple filtration steps (rapid filtration, GAC filtration, and slow sand filter)
are the final treatment steps. If the high concentrations of AOC are present in the water, then regardless
of the number of microorganisms, post-disinfection with a residual disinfectant is necessary. If high
numbers of microorganisms and low concentrations of AOC are present in the water (this may happen
when GAC filtration is the final step in the treatment train), then disinfection to decrease the number of
microorganisms is needed. It is in this last situation where ultraviolet light technology, fits best for ground
water application (Kruithof et al., 1992).
UV Light Disinfection Technology in ,
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Chapter 5—Summary of Findings
Therefore (according to the Dutch experience), the main parameter used to determine the applicability of
ultraviolet light as a disinfectant instead of chemical disinfectants is the AOC level in the water before
'the disinfection stage. ' . ' , '
are:
Disadvantages of using ultraviolet light for disinfection
• Lack of measurable disinfection residual.
• Lack of an in-place standardized mechanism to measure and calibrate equipment efficiencv
before and after installation.
• Lack of a firm technical database on system efficacy in various water quality conditions.
: Need for a secondary disinfectant for distribution network. •
5.2 OPERATIONAL FACTORS
Closed ultraviolet light systems are recommended for drinking water applications rather than the open
ultraviolet systems used in wastewater treatment. The practical advantages of closed ultraviolet light
systems, which are commonly used for drinking-water disinfection, are:
• Minimal or no exposure hazards to workers as compared to open systems
, • Very small space requirement; therefore, minimal or no construction costs
• Simplicity of installation due to modular design with two plumbing connections and one
electrical hook-up ,
• Simplicity of dismantling and replacing small units with larger units as population increases
without the need for extensive construction
• Lower maintenance requirements as compared to open systems, .which are exposed to
depositions from the air. ,
Ultraviolet light systems designed for small drinking water systems should consist of several modular units
to allow for a continuous operation while one or two units are maintained. For small ground water
systems, it is recommended that all electric fittings be of 'the modular type to facilitate installation,
replacement, and maintenance. All ultraviolet light systems should be equipped with monitoring devices
and before-and-after shut off valves.
UV Light Disinfection Technology in ~"~"~
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Chapter 5—Summary of Findings
5.3 EVALUATION AND COMPARISON OF ULTRAVIOLET LIGHT TECHNOLOGY
COSTS TO OTHER DISINFECTION PROCESSES
Capital costs for two ultraviolet light systems (one provides a dose of 40 mWs/cm2 and the other provides
140 raWs/cm2) were compiled from three ultraviolet,light equipment manufacturers. The average total
costs are presented in Exhibit 5-1. Exhibit 5-2 compares the costs of the ultraviolet systems at the two
set doses to ozonatikra at 1 mg/1 and chlorination at 5 mg/1. Exhibit 5-3 compares the costs of ultraviolet
systems that included chlorination as a secondary disinfectant at a dose of 1 mg/1 to ozonation at a dose
of 1 mg/1 and chlorination at a dose of 5 mg/1.
Exhibit 5-1. Average Total Costs for Ultraviolet Light Disinfection Systems*
Dose 40 mWs/cm2
EPA Row
Category
1
2
3
4
5
Design
Flow
(MGD)
0.024
0.087
0.27
0.65
1.8
Cost per Year (k$)
Total
Capital
1.3
. 1-7
3.7
7.7
16.6
Total O&M
0.4
0.8
1.7
3.7
9.7
Total
Production
Cost
1.7
2.5
5.3'
11.4
26.3
Cost per Year (c/kgal)
Total
Capital
14.8
5.2
3.7
3.2
2.5
Total
O&M
4.3
2.5
1.7
1.6'
1.5
Total
Production
Cost
19
8
5
• ;5 . •
,4
Dose 140 mWs/cm2
EPA How
Category
1
2
3
4
5
Design
Flow
(MGD)
0.024
0.087
0.27
0.65
1.8
Cost per Year (k$)
Total
Capital
1.7
3.6
10.0
16.5
42.1
Total
O&M
0.8
2.1
5.5
9.4
34.0
Total
Production
Cost
2.5
5.7
15.5
25.8
76.0
Cost per Year (c/kgal)
Total
Capital
19.0
11.4
10.2
6.9
6.4
Total
O&M
9.0
6.5
5.6
4.0
5.2
Total
Production
Cost
28
18
16
11
12
"August 1995 dollars
UV Light Disinfection Technology in
Drinking Water Application—An Overview
5-4
Final—September 1996
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Chapter 5—Summary of Findings
Exhibit 5-2. Comparison of Ultraviolet Light Disinfection Process Costs to Chlorination
and Ozonation Process Costs in Cents per Thousand Gallons
USEPAFlow
Category \
1
2
3 ,
..-4
5
« •*»
Design *Ffow ,
~MGD*
0.024
0.087
0.27
0.65
1.8
- Ultraviolet
„ Dose
^mWs/cm2
19
8
5 V .
5
4
Chlorination '
~ ^Dose
' Smgfl
280
70
20
20 ,
10
Ozonation
..'Dose
-' 1 mgfl
350
100
30
20 -
10
Ultraviolet
". Dose
140 mWs/cm2
30
20
'20
10
10
Exhibit 5-3. Comparison of Total Production Costs of Ultraviolet Treatment with
Secondary Disinfection to Chlorination and Ozonation Process
Costs* in Cents Per Thousand Gallons
USEPAFlow
Category
1
2
3
4
5
Design: Flow
(MGD)
- 0.024
0.087
0.27
0.65
1.8
40mWs/cm2
Ultraviolet
Dose with 1
mgfl chlorine
170
40
20
20
: 10
Chlorination
Dose 5 mg/I
280
70
20
20
10
Ozonation
Dose 1 mg/1
350
100
30
20
10
140mWs/cm2
Ultraviolet Dose
withlmg/l
chlorine
180
50
30
20
20
*Costs are rounded to the nearest ten.
As can be seen from Exhibit 5-2, ultraviolet light disinfection at the selected doses (without Chlorination
as a secondary disinfectant) is more economically feasible than ozonation and Chlorination for treating all
TJSEPA'flow categories 1 through 4; and is more feasible than ozonation and Chlorination at a 40
mWs/cm2 dose for the largest flow category. At 140 mWs/cm2, ultraviolet light treatment cost for flow
category 5 is more expensive but comparable to ozonation and Chlorination costs. As can be seen from
Exhibit 5-3, at the selected doses ultraviolet light technology plus Chlorination is still economically as
feasible or more feasible than ozonation for flow categories 1 through 4, less feasible at 140 mWs/cm2
than ozonation for flow category 5, but has the same cost estimate as ozonation at 40 mWs/cm2 for flow
category 5. Ultraviolet light disinfection at 40 ~mWs/cm2 plus Chlorination is more feasible than
UV Light Disinfection Technology in
Drinking Water Application—An Overview
5-5
Final—September 1996
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Chapter 5—Summary of Findings
chlorination alone for USEPA flow categories 1 and 2 and as feasible as chlorinatioh for USEPA flow
categories 3 through 5. At a 140 mWs/cm2 dose plus chlorination, ultraviolet light is economically more
feasible than chlorination for USEPA flow categories 1 and 2, less feasible for flow categories 3 and 5,
and as feasible as chlorination as flow category 4.
5.4 CASE STUDIES
Satisfaction with ultraviolet treatment in water and wastewater applications has been expressed by the
operators and systems managers contacted for this report. Ease and low cost of operation and maintenance
were stated to be the major factors in selecting ultraviolet technology over chlorination.
UV Light Disinfection Technology in
Drinking Water Application—An Overview
5-6
Final—September 1996
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APPENDIX A. OTHER ULTRAVIOLET-RELATED
DRINKING WATER DISINFECTION TECHNIQUES
This appendix provides a brief description of nonconventional ultraviolet disinfection technologies. These
technologies include photoassisted heterogenous catalytic oxidation (PHGO), and pulsed or modulated
ultraviolet irradiation.
The new ultraviolet manipulation techniques are either at experimental stage or have limited field
applications. Both techniques seem to be very promising and warrant further investigation and investment
in terms of research and development. At this point, both techniques lack a firm technical database for
system design and feasibility (technical and economical). One technique manipulates the amplitude of
ultraviolet light (pulsed ultraviolet light technique). The other one uses ultraviolet light on a catalyst
(TiO2), the water to be treated (PHGO). ~
A.1 . PHOTOASSISTED HETEROGENOUS CATALYTIC OXIDATION (PHCO)
Purifies®, an ultraviolet light firm in Canada, uses a new ultraviolet light manipulation technique known
as Photoassisted Heterogeneous Catalytic Oxidation (PHCO) to inactivate microorganisms and to destroy
organic contaminants. This technique is being used successfully at many contaminated ground water sites
(Purifies, 1995). PHCO is a process where photoactivated titanium dioxide (TiO2) is illuminated with near
visible ultraviolet light in an oxygenated suspension. The energy absorbed by titanium dioxide would
produce a redox environment sufficient to mineralize organic compounds. The high oxidation reduction
potential (ORP) levels achieved through this technique are also sufficient to inactivate microorganisms in
water and wastewater. The source of ultraviolet light could be either artificial or natural. TiO2 could be
used in the form of TiO2-coated mesh or hi the form of powder suspended hi an aqueous solution. The
PHCO process has been reported to be effective in degrading disinfection by-products precursors
compounds (Hand, Perram, and Crittenden, 1995). Also, the PHCO process has been shown to
successfully degrade a wide variety of organic contaminants, including drinking water regulated
contaminants, such as polychlorinated biphenyls (PCBs) and polyaromatic hydrocarbons (PAHs), into
simple mineral acids, carbon dioxide, and water. As mentioned above, the PHCO process has been
reported to inactivate microorganisms. However, one of the known drawbacks of the process is the lack
of a residual disinfectant after treatment. Richardson et al. 1996 (unpublished study) investigated the
effects of using chlorination for residual disinfection on water treated with ultraviolet-activated TiO2. The
UV Light Disinfection Technology in
Drinking Water Applications-Art Overview A-l Final—September 1996
-------
Appendix A. Other Nonconventional Drinking Water Disinfection Techniques
research investigated the presence of by-products before and after chlorine treatment. As a result of the
PHCO alone, the research identified one disinfection' by-product (tentatively identified as 3-methyl-2,4-
hexanedione). When chlorine was used as a secondary disinfectant following the PHCO treatment, several
chlorinated and bromrnated DBFs were formed. Most of these DBFs (although less in number and lower
in concentration than DBFs resulting from chlorination only) were the same as those DBFs identified when
chlorine was used alone for disinfection (Richardson et al., 1996).
Wei et al., 1994, and Ireland et al., 1993,'investigated the inactivation of Escherichia coli by TiO2
photocatalytic oxidation. The researchers concluded that the PHCO process is effective against
Escherichia coli and reported 100 percent destruction at a TiO2 catalyst dose of 1 g/L and a contact time
of 30 minutes. The researchers cautioned that although the results may be exciting, any optimism must
be tempered by the fact that Escherichia coli and other traditional surrogate microorganisms are rather
"easy" targets for disinfection by ultraviolet disinfection techniques. The real challenge would involve
demonstration of the efficacy of TiO2 in inactivating recalcitrant pathogenic microorganisms such as
Giardia lamblia and Cryptosporidium parvum (Wei et al., 1994).
/
Hand, Perram, and Crittenden, 1995, demonstrated in a laboratory setting that PHCO degrades DBF
precursors using an .artificial ultraviolet light source or sunlight. A minimum of 66 percent of the Total'
THM Formation Potential (TTHMFP) were destroyed (contact time 30 minutes). Hand et al., 1995,
provided information on PHCO process cost estimates using artificial light and sunlight as a source for
TiO2 illumination. The Hand et al. cost estimates for treating 1 MOD are presented in Exhibit A-l.
Exhibit A-l. Cost Estimates for the Removal of DBF Precursors from 1 MGD
Using the PHCO Process (Hand et al., 1995)
Contact Time
(min)
Artificial Light
15
30
45
60
Sunlight
Capital Costs
(K$)
75.3
117
143 ,
176.7
1,082
• Annualized
Capital Cost (K$)
8.844
13.750
16.800
20.800
127
Annual
Operation and
Maintenance (K$)
109
193
267
346
49
Total Production
Cost(e7Kgal)
32
57
75
100
48
UV Light Disinfection Technology in
Drinking Water Application—An Overview
A-2
Final—September 1996
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Appendix A. Other Nonconventional Drinking Water Disinfection Techniques
Exhibit A-l shows that the operation and maintenance cost of sunlight-activated PHCO process is about
56 percent of the total annual cost of treatment; the operation and maintenance cost of artificial light is
about 97 percent of the total annual cost of treatment. Hand et al., 1995, reported that electricity costs
alone account for 80 percent of the total annual cost of treatment in systems using artificial ultraviolet
lights. .
Hand et al. (1991), as reported in USEPA (1992) at 4-41, gave the following advantages:
• Removal of non-purgeable organic carbon (NPOC) and disinfection by-products (DBF)
precursors .. • . ' •
• Reduction in biodegradable fraction of NPOC
• Lower disinfection dosage, compared to the use of direct ultraviolet light
• Mineralization of trace organics such as pesticides, hydrocarbons, chlorinated hydrocarbons, and
taste and color compounds -
• Inactivation of pathogenic microbes
• Sunlight or near-ultraviolet light will activate the catalyst.
Disadvantages:
» Uncertainties in cost (no information is available at this point)
• Lack of a firm technical database for system design.
\
A.2 INACTIVATION RATES ACHIEVED WITH THE USE OF MODULATED
ULTRAVIOLET LIGHT
Bank et al. (1990) studied the effectiveness of computer-controlled modulated ultraviolet-C (200 nm to
280 nm) hi a series of in vitro experiments. The low-intensity pulsed1 lamp (< 0.04-mW/cm2 at 8 cm
distance) was used to irradiate 5 strains of bacteria. The exposure time was 60 seconds, which implies .
an ultraviolet light dose of about 2,5 mWs/cm2 at 8 cm distance using the pulsed lamp. Bacteria were
irradiated with modulated ultraviolet light for 60 seconds at 31 cm, which indicates -a dose that is
considerably less than 2.5 mWs/cm2. The bactericidal effect was almost the same for Escherichia coli
ATCC 25922, Staphylococcus aureus ATCC 25923, Pseudomonas aeruginosa ATCC 27853, Serratia
'In pulsed energy techniques, power (energy/time) is magnified many times by means of a capacitor. A capacitor stores
the electric energy and then releases it rapidly all together. This allows power to be amplified using average power
consumption. . - . - •
UV Light Disinfection Technology in
Drinking Water Application—An Overview A-3 Final—September 1996
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Appendix A. Other Nonconventional Prinking Water Disinfection Techniques .
marcesceus ATCC 8100, and Staphylococcus epidermidis VAS 9, with 6 to 7 log reduction in the number
of viable bacteria. When bacteria were irradiated with non-modulated ultraviolet light at the same
intensity and distance, the number of colonies surviving the treatment was more than 100 times the
number of colonies surviving the modulated treatment. The energy requirements and costs of this new
technique are considerably less than those of the traditional ultraviolet systems required to meet same log
reduction; however, the capital costs are unknown and the applications are still in the experimental stage.
Dunn, Ott, and Clark (1995) reported a 6 to 7 log reduction of both Klebsiella terrigena and
Cryptosporidium parviim ooqysts, using pulsed ultraviolet light at a dose of 1000 mWs/cm2. The dose
is delivered in one flash. The source of Cryptosporidium parvum oocysts was infected mouse feces. The
same results were achieved by two pulsed-light flashes at a dose of 500 mWs/cm2 each.
For surface applications (food, equipment, etc., disinfection), Dunn, Ott, and Clark ,(1995) reported that
the cost of apulsed-ultraviolet light system capable of delivering 4,000 mWs/cm2 is less than a few tenths
of a cent per square foot of treated area. This conservative cost estimate includes equipment amortization,
lamp replacement, electricity, and maintenance (Dunn, Ott, and Clark, 1995).
A.3 REFERENCES
Bank, H.L., et al. (1990). "Bactericidal Effectiveness of Modulated UV Light." 'Applied and
Environmental Microbiology. Vol. 56, No. 12, pp. 3888-3889. "
Dunn, Ott, and Clark (1995). "Pulsed-Light Treatment of Food and Packaging." Food Technology,
September, pp. 95-98.
Ireland, et al. (1993). "Inactivation of Escherichia coli by Titanium Dioxide Photocatalytic Oxidation."
Applied and Environmental Microbiology. Vol. 59, No. 5, pp. 1668-.
Purifies (1995). Personal communication with Mr. Brian Gutters and Mr. Tony Powell.
Richardson, et al. (1996). "Identification of TiO2/UV By-Products in Drinking Water," draft paper of
research conducted by the USEPA Ecosystems Research Division, National Exposure Research Laboratory,
Athens, Georgia, and the USEPA Drinking Water Research Division, National Risk Management Research
Laboratory, Cincinnati, Ohio. 13 pages, 29 references, 5 figures, and 2 tables.
it
USEPA (1992). Technologies and Costs for Control of Disinfection By-Products (Draft). Science and
Technology Branch, Criteria and Standards Division, OGWDW. Malcolm Pimie, Inc.
Wei, et al. (1994). "Bactericidal Activity of TiO2 Photocatalyst in Aqueous Media: Toward a Solar
Assisted Water Disinfection System." Environmental Science and Technology. Vol. 28, pp. 934-.
UV Light Disinfection Technology in
Drinking Water Application—An Overview A-4 Final—September 1996
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APPENDIX B. ORGANICS DESTRUCTION
""•^""^•••••••••^••••"••^"••^"•^^••^^^•••••••^^••^^••l
B. INTRODUCTION
This appendix provides a brief description of the theoretical scientific foundation that explains the potential
destruction capabilities of ultraviolet light against organic-compounds. It presents current findings from
a literature search and information provided by ultraviolet light equipment manufacturers. Appendix B
also describes the analysis' of ultraviolet light technology potentials for the destruction of volatile organic
compounds and other priority organics that might be found in drinking water sources.
B.1 BACKGROUND
Molecules absorb specific wavelengths (range) of electromagnetic radiation. The most useful region of
the ultraviolet spectrum for transferring energy to a molecule is at wavelengths greater than 200 nm.
When a molecule, absorbs ultraviolet radiation, the energy level in the bonds of that molecule increases.
The absorption of ultraviolet radiation also results in an increase hi the orbiting level of the excited
electron or electrons hi higher energy orbitals (Fessenden and Fessenden, 1986). In general, molecules
that require more energy for electron promotion absorb photons at shorter wavelengths and molecules that
require less energy absorb photons at longer wavelengths. ;
As a practical electromagnetic energy form, ultraviolet light has been employed in many chemical
manufacturing processes. A classical example of the use of ultraviolet light to form chemical compounds
is the production process of the widely used solvent, carbon tetrachloride (CG1J (Giancoli,;i991).
Ultraviolet light energy is used td break the C-H bonds hi natural methane gas (CH^ hi the presence of
' chlorine molecules (C12): ;
, CH4 + 2CLJ hv CC14 + 2H,
At a wavelength of 254 nm, organic compounds with double conjugated bonds like the C=C bond absorb
ultraviolet radiation. The presence of pesticides and other organic contaminants hi varying amounts in
ground water sources raises the issue of the efficacy of ultraviolet light for destroying organic compounds
found in ground water and of the possibility of harmful by-product formation.
UV Light Disinfection Technology in
Drinking Water Application—An Overview B-l Final—September 1996
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Appendix B. Organics Destruction
The scientific literature contains sufficient evidence that ultraviolet light, alone and in combination with
03 and H2O2, is a viable tool in degrading toxic and nuisance organic compounds that occur in ground
water. However, the efficacy of ultraviolet light at doses typically applied in household treatment devices
to destroy organic compounds has not been studied by many researchers.
B.2 DESTRUCTION POTENTIAL
The effects of ultraviolet light on organic compounds are well known. The formation of ozone and
hydrogen peroxide from the action of ultraviolet light on drinking water is one of two mechanisms that
lead to the disinfection of microorganisms and destruction of organic compounds. The other mechanism
is the direct action of ultraviolet light on the bonds connecting the atoms in organic compounds, thus
destroying the fundamental building blocks in an organic compound or microorganism. In contaminated
ground water, the use of ozone and hydrogen peroxide in combination with ultraviolet light hastens the
oxidation process and, hence, the destruction of both microorganisms and organic contaminants.
The destruction potential of organic compounds using ultraviolet light can be explained through
understanding the chemical bonding processes and the effect of electromagnetic energy on the electrons
engaged in bonding processes. The figures and illustrations presented within Exhibit B-l are intended
to be used as theoretical background information and are not intended to be used as exact figures or for
interpolation for direct field application.
t
Ultraviolet light is a viable technology for destroying organic contaminants in drinking water sources,
however, cost may be an obstacle. For example, the equipment manufactured to destroy high levels of
organic contamination in ground water Superfund sites is designed to produce ultraviolet light at
significantly higher doses and intensities than those needed for conventional drinking water treatment
purposes. Therefore, the power costs required to operate equipment specifically intended for organic
destruction are high. ''•'•:*
UV Light Disinfection Technology in
Drinking Water Application—An Overview B-2 Final—September 1996
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Appendix B. Organics Destruction
Exhibit B-1. A Precis Description of Chemical Bonding to Explain
Organics Destruction Potential Using Ultraviolet Light
A coyaient bond results from the sharing of a pair of electrons by two atoms, m a covalent bond,
the molecular orbital that is symmetrical about its axis is called a sigma (a) molecular orbital and
the covalent bond is a sigma bond. An example of a cr bond is a C-H bond in a methane molecule.
The energy from ultraviolet light pushes the pair of electrons into a higher orbital level, causing the
electrons to become out-of-phase (in wave function). This is called an antibonding orbital and is
given the symbol a*. -
The figure below shows a two-dimensional schematic presentation of electrons in orbital motion.
Closer to reality representation is far more complex and beyond the scope of this report. The
important aspect of this presentation is that it shows that when two electrons are in phase forming
a bond, .both electrons do move together above and below the axial plane. The positive and
negative signs'in the figure are used to indicate the presence of electrons above the plane or below
the plane and are not an indication of charge or anything else.
Electrons in in Phase and out of Phase Wavelengths
or
In Phase Electrons
or
Out of Phase
022E-06
A covalent Pi (TC) bond is a molecular orbital bonding joining two atoms and is located above and
below the plane of sigma bond. An example of this bond would be the double bond in ethylene
H2C = GH2 where the first C-C bond is the a bond and the second C-C bond is the 7t bond. When
a TC bond is unexcited, the, electrons are in phase. When ultraviolet light is absorbed by the
molecule, the electrons become out of phase and the antibonding orbital is called K* (McMurrv
- 1992). . J'
Because all organic contaminants have a and n bonds, the transition of TC and o electrons into an
antibonding state is a very important step in the destruction of organic contaminants hi drinking
water. Many of the slow or non-biodegradable organic contaminants found in ground water have
ring molecules like benzene, pyridine, and furan compounds. Ultraviolet light is very effective in
breaking up rings and making these compounds more prone to undergo mineralization or become
more biodegradable. .
Also important in the understanding of molecular destruction through ultraviolet light is the role of
nonbonded electrons. These are pairs of electrons (called the (i\) pair of electrons) that fill a
molecular orbital, but were not formed by a bond.
An example of (T|) electrons is the electron pairs of an oxygen atom in methyl alcohol CH3OH..
UV Light Disinfection Technology in
Drinking Water Application—An Overview
B-3
Final—September 1996
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Appendix B. Organics Destruction
Exhibit B-1. A Precis Description of Chemical Bonding to Explain
Organics Destruction Potential Using Ultraviolet Light (Continued)
When ultraviolet light is absorbed by such a molecule, the orbital containing (TJ) electrons does not
have an antibonding orbital like
-------
Appendix B. Organics Destruction
Exhibit B-1. A Precis Description of Chemical Bonding to Explain
Organics Destruction Potential Using Ultraviolet Light (Continued)
Cl
j
H-C-CI
I
Cl
Trichloromethane (Chloroform)
Examples of Photochemical Reactions
Cl
\
Cl
\
Cl H
Trichioroethene
Cl
p-Dichlorobiphenyl
Os/hv
H2O
Os/hv
H20
HO OH
Oxalic Acid
hv
HCOOH
Formic Acid
o
II +hv
CHsCCHs
Acetone
CO2 + H2O
-C^O + CH3
I OH- 10H-
CHgCOOH CH3OH
Methyl Alcohol (Methanol)
Acetic Acid
CHsCOOH
Acetic Acid
OH- COOH
OH-
hv
COOH hv COOH
CO2 + H2O
. GOOH
Oxalic Acid
022E-07
UV Light Disinfection Technology in
Drinking Water Application—An Overview
B-5
Final—September 1996
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Appendix B. Organics Destruction
The destruction of an organic compound by ultraviolet light is given in the following example:
Trichloroethylene (TCE) is a contaminant found in many ground water sources in the United States.
C = C + hv — >• CO2 + HjO + 3C1
Ultraviolet light absorbed by dissolved oxygen and water molecules ultimately leads to the formation of
unstable radicals such as hydroxyl radicals. These radicals react with excited TCE molecules and break
them up, leading to the formation of the innocuous final product of water and carbon dioxide.
To effectively control organic compounds in water and wastewater using ultraviolet light, three approaches
can be followed:
1. Determine the optimal absorption wavelength of the target compound, and order the hardware that
can deliver ultraviolet light at that wavelength. The absorption spectra of many organic
compounds are available in the literature.
2. Use ultraviolet-light to produce compounds that can attack the target compound. For example,
ultraviolet light at 184.9 nm attacks water molecules to produce H" and OH" radicals that are
powerful oxidizing agents.
3. Increase the oxidizing power available by adding oxidizing agents such as ozone and hydrogen
peroxide and then irradiate the water. The use of ultraviolet light not only will produce free
radicals as in approach number 2 but also will excite the added ozone and hydrogen peroxide, thus
increasing their already powerful oxidizing power.
It must also be noted that the oxidation potential of ultraviolet-produced radicals in drinking water
compared to those of chlorine gas and ozone (in volts) is in the following order (Jody, Klein, and Judeikis,
1989): . , .
OHT > O- > 03 > H02* > C12
2.80 2.42 2.07 1.70 1.36 in volts ,
The literature search conducted for this report resulted in the following findings regarding the destructive
potential of organics using ultraviolet light. Nick et al. (1992) studied the degradation of selected triazine
herbicides by ultraviolet light as used in the ultraviolet disinfection of drinking water. Triazine herbicides
are a family of herbicides that include simazine and atrazine. Atrazine is a commonly used herbicide in
UV Light Disinfection Technology in
Drinking Water Application—An Overview B-6 . • Final—September 1996
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Appendix B. Organics Destruction
corn cultivation and is found in many ground water sources. In their research, Nick et al. (1992)
addressed two issues:
• The extent to which ultraviolet photolysis of herbicides gives rise to new anthropogenic
compounds that are as, or more, dangerous than the original compounds
• The extent to which herbicides degrade during normal ultraviolet application to drinking water.
Nick et al. (1992) noticed that many herbicides do not absorb ultraviolet light above 240 nm and that only
those herbicides that contain an aromatic ring or similar chromophore may degrade at wavelengths above
240 nm. Using an ultraviolet lamp of an average dose of 25 mWs/cm2, Nick et at (1992) concluded that
the degradation of triazine herbicides remains below 5 percent. Nick et al. (1992) also reported that a
conversion of more than 10 percent of atrazine, simazine, propazine; and terbuthylazine by
photodegradation did not result in mutagenicity (using the Ames test), even when the irradiated material
was applied in high concentrations. Therefore, ultraviolet photolysis of triazine herbicides did not give
rise to new equally or more hazardous compounds, mtraviolet photolysis of triazine compounds does
eliminate the mutagenicity risks associated with the triazine compounds. Treatment of drinking water for.
disinfection by commercially available POU ultraviolet lamps, even at doses as low as 25 mWs/cm2, has
a positive side effect. The Nick et al. (1992) research shows a herbicide degradation of less than 5 percent
for four triazine compounds.
Exhibit B-2 presents the photodegradation of herbicides of the atrazine family as reported by Nick et al.
(1992). ' .' ' . .-.
Exhibit B-2. Photodegradation of Herbicides of the Atrazine Family
Herbicide
Atrazine
Simazine
Propazine
Terbuthylazine .
Fraction Decomposed at
25mWs/cm2(%)
2.4
3.4
4.1
4.4
Dose Required to Achieve 90%
Decomposition (mWs/cm2)
2400
2700
1400
1300
As can be seen from Exhibit B-2, the dose required to degrade 90 percent of the initial herbicide
concentration in the solution is about two orders of magnitude higher than the dose emitted by most
commercially available ultraviolet devices used for disinfection purposes.
UV Light Disinfection Technology in
Drinking Water Application—An Overview
B-7
Final—September 1996
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Appendix B. Organics Destruction
Francis (1989) studied the physio-chemical parameters of oxidating organic pollutants using ultraviolet
light and ozone. Using ethylene glycol as a surrogate and a 2 kw antimony halide medium-pressure lamp,
Francis (1989) concluded that using ultraviolet light after saturating the flow with ozone increased the
reduction rate of TOC. Francis (1989) made another important observation. He. observed that a smaller
reactor in series with a larger reactor leads to an increase in TOC reduction. Francis (1989) attributed this
increase in TOC reduction to the improved uniformity of the ultraviolet light distribution in the smaller
reactor.
Berglind, Gjessing, and Johansen (1979) studied the effects of ultraviolet light in combination with H2O2
on aquatic humus and organic compounds. The early results compiled by the researchers showed that,
after one minute of irradiating hydrogen peroxide containing water, a 45 percent reduction in color and
a 43 percent reduction hi organic carbon were achieved. The researchers also reported their own research
on water containing humus and, 65 ug/1 of the contaminant 3,4-benzo(a)pyrene [B(a)P] (a polyaromatic
hydrocarbon [PAH] compound, which is a contaminant regulated under the National Primary Drinking
Water Regulations [NPDWR]), 1 ug/I 2-methylisoborneol (MB), 100 ug/1 of chloroform, and 100 ug/1
of bromodichloromethane (BDCM). The results of the researchers' experiments are presented in Exhibit
B-3. The ultraviolet radiation unit consisted of six 30-watt ultraviolet lamps; however, the intensity was
not reported in the published paper.
As can be seen from Exhibit B-3, after 2 hours of irradiation without hydrogen peroxide, 29 percent of
B(a)P was destroyed and 91 percent was destroyed in the presence of hydrogen peroxide.
The results for chloroform and BDCM were better, with 58 percent and 91 percent reduction in chloroform
and 25 percent and 91 percent reduction in BDCM without and with the addition of 0.1 ml 35-percent
hydrogen peroxide in a 0,8 liter reactor. .
Xu et al. (1989), using ozone and ultraviolet light, examined TOC reduction in wastewater under different
pH conditions. Xu et al. (1989) used the compound pyridine as a surrogate for refractory compounds
commonly found in industrial wastewater. The Xu et al. (1989) research shows that at high pH, better
TOC reductions could be attained. The research also suggests that the breakup of pyridine molecules
occurs in stages where the ozone breaks the ring molecule, leading the way to more oxidative intermediary
UV UgM Disinfection Technology in
Drinking Water Application—An Overview B-8 Final—September 1996
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Appendix B. Organics Destruction
Exhibit B-3. Removal of Organic Chemicals from Water with Ultraviolet Radiation
and Hydrogen Peroxide
ug/l (percent destruction)
'
Minutes UV
Radiation
0
30
.60
120
' 240
Without H2Q2
B(a)P
65(0)
-
-
42 (29)
-
Chloroform
100(0)
92 (8) '
42 (58)
-
BDCM
100(0)
-
91 (9)
75 (25)
-
With 0.1 ml-35%H.,O,/l
B(a)P
'- - •
-
18 (72)
6(91)
1 (98)
MIB
1
0 (100)
—
.—
-.
Chloroform
100 (0)
75 (25)
68 (32)
9(91)
-
BDCM
100(0)
58 (42)
44(56)
9 (91)
—
B(a)P: 3,4-Benzo(a)pyrene
MIB: Methylisoborneol
BDCM:' Bromodichloromethane
(): Denotes percent-reduction
B(a)
Percent reduction of chemicals in aqueous solutions with
different "UV doses"; 0.1 ml 35% \^QJ\ was added.
MIB = Methylisoborneol
BDCM = Bromodichloromethane
B(a)P = 3,4 Benzo(a)pyrene
30 60
120 240
Minutes UV - Radiation
022E-01
compounds. Once all pyridine molecules are destroyed, a fast degradation of TOC occurs as the newly
formed intermediary compounds quickly mineralize (i.e., breaking organic compounds down to inorganic
compounds such as CO2 and H2O). Xu et al. (1989) found that pH 10.3 to be the optimal.pH. The results
of the Xu et al. (1989) work are presented in Exhibits A-4 and A-5.
Exhibit B-4 shows that the breakup rate of pyridine in an ozone/ultraviolet system was faster than the TOC
'reduction rate in the same system and under the same conditions. This implies that complete
mineralization of pyridine is not direct and that intermediary organic compounds are formed in the process.
Exhibit B-4 also shows that a combined ozone/ultraviolet system is more effective in destroying pyridine
and reducing TOC than an ozone system alone.
UV. Light Disinfection Technology in
Drinking Water Application—An Overview
B-9
Final—September 1996
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Appendix B. Organics Destruction
Exhibit B-4. Elimination of Pyridine and TOC Reduction by O3/UV and Ozone Alone
100
CC 50
6
25
Og/UV
60
240
120 180
Time (Minutes)
b. Percent reduction of pyridine TOC by Og/UV and O3 alone
022E-03
T=40°C
pH=10.5
O3=11mg/I
UV=50w
T=40°C
pH=10.5
O3=11mg/l
UV=50w
UV Light Disinfection Technology in
Drinking Water Application—An Overview
B-10
Final—September 1996
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Appendix B. Organics Destruction
Exhibit B-5. Pyridine Elimination and TOC Reduction at Different pHs
60 120
Time (Minutes)
a. Percent elimination of pyridine at different pHs
180 -
022E-04
too -
o
e.
60 120 180
Time (Minutes)
b. TOC reduction at different pHs
1. pH=2.1
2. pH=12
3. pH=7.8
4. pH=10.5
T=40°C, UV=50W
O3 at 10,7-10.8 mg/l
initial concentration
of pyridine 194ppm
1. pH=2.1
2. pH=12
3. pH=3.5
4. pH=7.8
5. pH=10.5
T=40°C, UV=50W
O3 at 10.7-10.8 mg/l
initial concentration
of pyridine 194ppm
UV Light Disinfection Technology in
Drinking Water Application—An Overview B-ll
Final—September 1996
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Appendix B. Organics Destruction
Exhibit B-5 shows that at low pH, pyridine destruction rate and TOC reduction rates are the lowest. The
highest pyridine destruction rate and TOC reduction rate occurred at a pH of 10.5.
Yu, Wan, and Tsai (1989) compared TOC removal from activated sludge using oxygen/ultraviolet systems
versus ozonation as pretreatment. The researchers found that in activated sludge, pretreatment with ozone
had a better effect on the biodegradability of phenolic compounds than the O2/UV system. The researchers
did not report any ultraviolet doses in their published paper.
Zeff, Leitis, and Barich (1989) used ultraviolet/ozone and ultraviolet/H2O2 systems to control an array of
contaminants usually found in ground water at Superfund sites. The researchers reported that
tetrachloroethylene or perchloroethylene (PCE) contaminated water treated with these systems resulted in
\
the reduction of VOCs and color to below State action level. They also reported that
dibromochloropropane (DBGP) and PCBs were reduced to less than 1 ppb. Both contaminants are
regulated under NPDWR with an MCL of 0.002 mg/1 for DBCP and an MCL -of 0.0005 mg/1 for PCBs.
The researchers reported direct operation and maintenance costs associated with treating PCE-contaminated
* drinking ground water of 200 ppb as being $0.20 to $0.30 per 1,000 gallon (1989 prices).
Jody, Klein, and Judeikis (1989), using ozone/ultraviolet systems to treat wastewater containing hydrazine
compounds, found that the presence of metal ions such as copper and iron help in the destruction of
hydrazine compounds. The researchers also confirmed the findings of Xu et al. (1989) that the destruction
of organic compounds is more efficient at high pH. The researchers did not report any, ultraviolet doses
in their published paper. More research on the effects of metal ions on the destruction of organic
contaminants is needed to elucidate the processes involved and determine the kinetics of the destruction
process. ' •
In a more recent study of Ultrox®, Zeff (1993) reported the results of using an ozone/hydrogen peroxide/
ultraviolet system to remove PCE from a contaminated ground water well. The results are presented in
Exhibit B-6. As can be seen from Exhibit B-6, the system tested is capable of reducing PCE levels to
below MCL levels and 1,1,2-trichloroethane (TCA) levels in two tests. However, the author did not report
any specific ultraviolet doses. .
UV Light Disinfection Technology in
Drinking Water Application—An Overview B-12 Final—September 1996
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Appendix B. Organics Destruction
Exhibit B-6. Uitrox® Demonstration at South Gate Ground Water Supply Site
' ,
Test No.
1
2
3
4
5
6
7
8
9
10
11
12 '
O3 Dose
(rrig/|)
13
19 '
19
0
0
0
13
0
o
9
13
9
Pilot Test Procedures and Analytical Results*
(all tests run at 50 gpm)
H2O2 Dose
(mg/l)
None
None
8.3
13
8.3
0
8
8.3
8.3
4
0
0
UVLamp
Complement
Full
Full
None
None v
One Third
Full
None
One Fourth
One Half
None
None
None
PCE Analysis
Infl.HjQ
(PPb)
14
20
17
17
17
17.5
18
16
J6
18
-
18
Effl.H.,0
-------
Appendix B. Organics Destruction
Exhibit B-7. Chlorinated Hydrocarbon Elimination with Ozone/Ultraviolet Treatment
'in Drinking Water Supply of Niederrohrdorf
Parameter
1 ,1 -Dichloroethylene
cis-1 ,2k-DichIoroethylene
Chloroform
1 , 1 -Dichloropropene
Trichloroethylene
Perchloroethylene
Sample A (ng/I)
Before
After
Ozone/UV-Treatment
<0.05
31
0.12
0.12
100
0.12
0.12
0.37
<0.05
<0.05
5.9
<0.05
Sample B (pg/l)
Before
After
Ozone/UV-Treatment
n.a.
16
<0.05
n.a.
84
n.a.
n.a.
0.06
•0.1
n.a.
5.3
n.a.
Gehringer et al. (1993) investigated the feasibility of using an ozone/ultraviolet system to treat TCE- and
PCE-contaminated water in a real situation compared to an ozone/electron beam system. The researchers
found that the destruction of organic compounds using an O3/electron beam system was about one order
of magnitude higher than the destruction obtained using the ozone/ultraviolet system. Moreover, the
researchers found that the electric power consumption in an ozone/electron beam accelerator system was
five times less than that of an ozone/ultraviolet system. The ultraviolet lamp used in the experiment had
an output of 7.8 kw and the electron beam output was a 500 keV electron accelerator, or 8xlO~14 Joules.1
In 1994, the Journal of Hazardous Waste Consultants compared the use of ultraviolet systems for the
destruction of VOCs with other technologies and noted that ultraviolet systems destroy VOCs found in
drinking water, while air stripping systems, for example, transfer the VOC contamination from the liquid
phase to the gas phase (JHWC, 1994). . i
B.4 OPERATIONAL FACTORS , V
Operational factors that should be considered for maximizing the effectiveness of ultraviolet systems for
the destruction of organic contaminants are the following:
• Proper selection of an ultraviolet lamp that emits the proper effective wavelength range and .that
delivers the required dose.
• Age of the lamps.
'KeV « 1.6 x 10-'s Joules
1 Watt = 1 Joule/sec
UV Light Disinfection Technology in
Drinking Water Application—An Overview
B-14
Final—September 1996
-------
Appendix B. Organics Destruction
• Keeping track of lamp efficiency, particularly when lamps are at the end of their operational
life span.
• Cleaning the unit periodically as recommended in the manufacturer's manual, regardless of
whether the unit looks clean-to the naked eye.
• Waters that contain light-obstructing material, such as colloids or certain minerals such as iron,
need to be treated before entering the ultraviolet unit.
• Keeping a record of influent and effluent quality parameters such as pH and ORP (oxidation
reduction potential) to monitor any sudden changes that require immediate attention.
The following section discusses factors related to ultraviolet wavelength transmission and presents
intensities required to destroy certain chemical bonds normally found in organic contaminants. Other
operational factors are discussed hi more detail in Chapter 2. .
The graphical presentation for the distribution of wavelengths emitted by low- and medium-pressure arcs
given in (Exhibit 1-3) was constructed from a paper published by Legan in 1982. As can be seen from
Exhibit 1-3 and Exhibit B-8, for that specific low-pressure lamp, about 93 percent of ultraviolet light is
, transmitted at 254 nm and 6 percent is transmitted at 185 nm.
The distribution of wavelengths emitted by modern low-pressure arcs used in water application varies but
is assumed to be at a minimum about 85 percent of the energy at 254 nm (range 85% - 90%), 7-10
percent of the emitted energy in the 180 to. 185 nm range, and 5 percent at more than 254 nm (von
Sonntag and Schuchman, 1992). This spectrum of ultraviolet light range increases the likelihood of
ultraviolet absorption by different molecules. As stated earlier, molecules absorb ultraviolet energy at
specific wavelengths and not at all wavelengths. For example, benzene absorbs ultraviolet light at 260
nm. Thus, when a low-pressure ultraviolet light is used for disinfection of drinking water, a contaminant
that -absorbs a wavelength other than 254 nm wavelength will absorb the specific wavelength that
constitutes a small fraction of the light emitted by the ultraviolet lamp. "
There are medium-pressure and high-pressure arc lamps that are capable of producing a broader spectrum
of the ultraviolet range, and there are high-pressure arc lamps that produce the bulk of their ultraviolet
light at a higher energy wavelength (180 to 185 nm). These high-energy (shorter)2 wavelengths are
Intensity is defined as the power transferred across a unit area, where:
Power = Work/time = Energy transferred/time, where Energy is inversely proportional to wavelength.
For further details, please refer to page vii.
UV Light Disinfection Technology in
Drinking Water Application—An Overview B-15 Final—September 1996
-------
Appendix B. Organics Destruction
capable of producing unstable radicals that in turn attack other organic compounds found in the water.
This is an important mechanism in which contaminants that do not absorb the ultraviolet light emitted
energy, or only a small portion of it, get destroyed by intermediaries formed by ultraviolet light action.
Exhibits A-9 and A-10 (presented below) are intended to give an idea of the destruction potential of
ultraviolet light against various organic and inorganic compounds. The maximum wavelengths (lowest
energy) needed to break a bond (a or TC) varies from one compound, to the other. This variation in energy
requirements to break an organic compound also can be found in the range of wavelengths that could be
absorbed in certain compounds. For example, for aromatic compounds, intense ultraviolet light absorption
occurs at 205 nm, while weak ultraviolet light absorption occurs at 260 nm (McMurry, 1992).
•
The power of various wavelengths emitted by different ultraviolet lamps are presented in Exhibit B-8.
Exhibit 2-8 shows that the wavelengths emitted by ultraviolet light vary from one pressure lamp to the
other. As can be seen from Exhibit B-8, low-pressure arc lamps emit the bulk of their energies at about
254 nm wavelength, while medium- and high-pressure lamps emit their energies at a wider range. The
germicidal effects of ultraviolet light at 254 nm are high. Because of that, when ultraviolet light is to be
used for disinfection, low-pressure mercury lamps are selected over medium- and high-pressure mercury
lamps.
Exhibit B-9 presents the maximum light wavelengths (minimum energies) absorbed by electrons in
different chemical bond settings and leading to their dissociation. Exhibit B-9 shows the energy required
to break different types of covalent bonds. The values presented in Exhibit B-9 are to be Viewed as trend-
indicative and not as exact values. Exhibit B-9 shows which wavelengths, and therefore ultraviolet
energies, can interfere in the motions of a pair of electrons forming a covalent bond to the level of
breaking the bond they form. For example, the H-O bond in water will break under the effect of
ultraviolet light at a wavelength of about 185 nm. This H-O bond break will lead to the formation of
powerful hydroxyl radicals. In natural waters, these radicals react with organic compounds or
microorganisms normally found in water and cause a change in their nature.
, ' . . •
Exhibit B-10 presents important photochemical reactions that relate to organics destruction and
microorganisms disinfection. The photochemical reactions presented in Exhibit B-10 show the formation
of free radicals in water under the effect of ultraviolet light.
UV Light Disinfection Technology in
Drinking Water Application—An Overview B-16 Final—September 1996
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Appendix B. Organics Destruction
Exhibit B-8. Power of Light Erhitted by Mercury-Vapor Ultraviolet Lamps
Wavelength, nm
Infrared
1,367.3
1,128.7
1,0.14.0
Visible
578.0 (yellow)
546.1 (green)
435.8 (blue) .
404-5 (violet)
Ultraviolet
366.0
334.1
313.0
302.5
296.7
289.4 ,
280.4 -
275.3
270.0
265.2
257.1
253.7 (germicidal)
248.2,
240.0
232.0
184.9
• .
Total ultraviolet power
Power, W
Low-pressure
(85W)
' _
— ' •
- • -'
"•
3.04
0.26
.0.30
0.12
0.16
0.01
0.18
0.02
0.06
0.01 ,
0.01
0.01
—
0.02
• . ' — ' • -
30.00
. • — '
— -. '
— ,
1.80
32.30
Medium-Pressure
(550W)
4.6
3.8
12.2
23.0
28.2
23.3
12.7
30.1,
: 2.8
15.0
8.2
5.0
1.8
2.8
0.8
, 1-2
4.6
1.8
5.0
2.6
2.2
2.4
0.3
95.2
High-Pressure
(7J500W)
39.3
46.2
165.0
' •'
297.0
290.0
216.0
150.0
44.30
46.6 -
270.0
117.6
66.9
21.0
'63.9
'21.6,
22.9
158.0
31.0
137.0
41.8
31.9
31.2
8.2
1,619.1
Source: Canrad-Hanovia, Inc., as cited in Legan, 1982.
UV Light Disinfection Technology in
Drinking Water Application—An Overview
B-17
Final—September 1996
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Appendix B. Organics Destruction
Exhibit B-9. Dissociation Energies for Chemical .Bonds
Bond
Carbon
C-C
C-C
GeC
C-C1
C-F
C-H
C-N
C=N
CaN
C-O
C=O (aldehydes)
C=O (ketones)
C-S
• C=S
Hydrogen
H-H
Nitrogen
N-N
N=N
NsN
N-H (NH)
• N-H (NHg)
N-O
N=O
Oxygen
0-0(02)
-o-o-
O-H (water)
Sulfur
S-H
S-N
S-O
Dissociation
Energy,
kcal/gmol
82.6
145.8
199.6
81.0
116.0
98.7
72.8
147.0
212.6
85.5
176.0
179.0
- 65.0
166.0
104.2 .
52.0
60.0
226.0
85.0
102.0
48.0
162,0
119.1
47.0
117.5
83.0
115.0
119.0
UVLight
Maximum
Wavelength
to Break
Bond, nm
346.1
196.1
143.2
353.0
246.5
289.7 ;
392.7 ,
194.5
134.5
' 334.4
162.4
159.7
439.9
172.2 ,
274.4
549.8
476.5
126.6
336.4
280.3
595.6
' 176.5
240.1
608.3
243.3
344.5
248.6
240.3
Will UV Light at These
Wavelengths Break the Bond?
253.7 nm
yes
no
no
yes
•' no.
yes
yes
no
no
yes
no
no
yes
no
yes
yes
yes
no
yes
yes
yes
no
no
yes
no
yes
no
no
184.9 nm
yes
yes
no
yes
yes ,
yes
yes
yes
no
yes
no
no
yes
no
yes
yes
yes
no
yes
yes
yes
no
yes
yes
yes
yes
yes
yes
Source: Dean, 1973, as cited in Legan, 1982.
UV Light Disinfection Technology in
Drinking Water Application—An Overview
B-18
Final—September 1996
-------
Appendix B. Organics Destruction
Exhibit B-10. Examples of Photochemical Reactions and Their Effects
Reaction
H20 + hv = H' + HO'
H202 + hv = 2 HO*
O2 + hv = O3
RH + hv = H' + FT
Fe+2 + hv = Fe*3 .
Fe(CN)6'4 4- hv = Fe(CN)6-3 "
NO + hv = N2 + O2
NO2 + hv = NO + O
NH3 + hv = NH2* + H* ,
Effective
Wavelength,
nm
184.9
253.7
253.7
184.9
253.7
184.9
184.9
313.0
184.9
Result
Water broken into free radicals
Hydrogen peroxide broken into hydroxyl radicals
Oxygen molecules converted to ozone
Organic broken into free radicals
Ferrous ion converted to ferric ion
Ferrocyanide ion converted to ferricyanide ion
Nitric oxide decomposed (smog avoided)
Nitric oxide formed (part of smog cycle)
Ammonia broken into free radicals '
Source: Calvert and Pitts, 1966, as qited in Legan, 1982.
B.5 ULTRAVIOLET LIGHT TECHNOLOGY AND CURRENT SAFE DRINKING
WATER REGULATIONS
Ultraviolet light is not identified as a Best Available Technology (BAT) for the treatment of any NPDWR
contaminant, the current advances in ultraviolet technology and its wide applications alone and in
combination with ozone and hydrogen peroxide in treating ground water contamination in many Resource
Conservation and Recovery Act (RCRA) Superfund sites strongly suggest its dual beneficial use. as a
disinfectant and as an organics control technology.
UV Light Disinfection Technology in
Drinking Water Application—An Overview B-19
Final—September 1996
-------
Appendix B. Organics Destruction
B.6 REFERENCES
Berglind, L., Gjessing, E., and Johansen, E. Skipperud (1979). Oxidation Techniques in Drinking Water
Treatment: Drinking Water Pilot Project, Report 11A, Advanced Treatment Technology. USEPA ODW,
Washington, DC. EPA-570/9-79-020. ,
Fessenden, R.J., and Fessenden, J.S. (1986). "Spectroscopy I: Infrared and Nuclear Magnetic
Resonance." Organic Chemistry: pp. 313-317'. Brooks/Cole Publishing Company.
Francis, P.D. (1989). "Oxidation of Organic Pollutants by UV Light and Ozone: Modelling the Process
Parameters in a Flow Reactor." Ozone in Water Treatment, pp. 672-687.
Gaudy, A.F., and Gaudy, E.T. (1980). Microbiology for Environmental Scientists and Engineers.
McGraw-Hill. , .
Gehringer P. et al. (1993). "Groundwater Treatment for Chlorinated Ethylenes Using Ozone and Electron
Beam Irradiation." Ozone in Water and Wastewater Treatment. Vol 2, pp. S-13-26 - S-13-32.
Giancoli, D.C. (1991). Physics, Principles -with Applications. 3rd ed. Prentice-Hall.
JHWC (1994). "Comparing Treatment Options for VOC-Contaminated Ground Water." The Hazardous
Waste Consultant, pp. 1.20-1.24.
Jody, BJ., Klein, M.J., and Judeikis, H. (1989). "Catalytic O/UV Treatment of Wastewater Containing
Mixtures of Organic and Inorganic Pollutants." Ozone in Water Treatment, pp. 619-631.
Legan, R.W. (1982). Ultraviolet Takes on CPI Role. Chemical Engineering. January 25, 1982. pp. 95-
100. " - -
Leitzke, O. (1993). "Treatment of Contaminated Ground Water with the Ozone/UV Combination System."
Ozone in Water and Wastewater Treatment. Vol 2, pp. S-13-15-S-13-25.
McMurry, J. (1992). Organic Chemistry. 3rd ed. Brooks/Cole Publishing Company.
Nick, K., et al. (1992). "Degradation of Triazine Herbicides by UV Radiation Such as Used in the
Disinfection of Drinking Water." / Water SRT-Aqua Vol 41, No 2, pp. 82-87.
von Sonntag, G., and Schuchmann, H.P. (1992). "UV Disinfection of Drinking Water and By-Product
Formation—Some Basic Considerations" J Water SRT—Aqua Vol. 41, No. 2, pp. 67-74.
Xu, S., et al. (1989). "Treatment of Pyridine Containing Wastewater by Ozonation Under UV Irradiation."
Ozone in Water Treatment, pp. 743-750. , :
Yu, Y., et al. (1989). "Comparison Between O3 and O/UV in Their Effects on the Biodegradability of
Some Phenolic Compounds." Ozone in Water Treatment, pp. 751-765.
Zeff, J.D. (1993). "Testing of a Full Scale UV/Oxidation System to Obtain a Permit for Removing PCE
from a Drinking Water at a Well Site in the City of South Gate, California." Ozone in Water and
Wastewater Treatment. Vol 2, pp. S-13-1-S-13-14.
Zeff, JJD., Leitis, E. and Barich, J.T. (1989). "UV-Oxidation Case Studies on the Removal of Toxic
Organic Compounds in Ground, Waste and Leachate Waters." Ozone in Water Treatment, pp. 720-730.
UV Light Disinfection Technology in
Drinking Water Application—An Overview B-20 Final—September 1996
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APPENDIX C. QUESTIONNAIRE USED FOR STATE INQUIRY AND AS
GUIDE IN TELEPHONE INQUIRIES
u.s. EPA : . .
SAIC Contract 68-C3-0365 -
Ultraviolet Light Disinfection Study
C.1 GENERAL SYSTEM QUESTIONS AND EQUIPMENT
1. What is the location of the system? ' •
.2. What is the population served and design flow? , •'
3. When was the system installed? ." . -
4. Why was UV treatment selected? What was the anticipated advantage over traditional
disinfection systems?
, 5. Is the UV system a closed-type system or an open type system?
6. Is the system equipped with telemetry control system? Is there a fully automated backup
system in place?
7. Was the UV system locally manufactured? Did it come with a warranty?
8. Does the public water, system have storage capacity? What is the capacity? "Open reservoirs
or cisterns?
9. Type of treatment applied before and after UV. treatment (secondary disinfection)?
10. If chlorination is used as a secondary disinfectant what kind of chlorination (gas, chloramine,
calcium or sodium hypochlorites)? What are the assumed and residual doses?
11. How are UV intensity and dose measured? .
C.2 WATER DATA
• * ' . •
1: What is the maximum turbidity levels before and after UV treatment?
2. What are the maximum iron levels in source water or before UV treatment?
3. Have there been any coliform outbreaks? Any increase in biofilm formation in the network
has been noticed?
4. Have there been any microbiological problems?
UV Light Disinfection Technology in
Drinking Water Application—An Overview C-l Final—September 1996
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Appendix C. Questionaire Used for State Inquiry and as Guide in Telephone inquiries
C.3 OPERATION AND MAINTENANCE
1. How often does the system get cleaned?
2. Is the system equipped with mechanical wipers? Ultrasonic cleaners? Are cleaning agents
used to clean the system manually? Is water Tinder high pressure used to clean the units? At
what pressure? If any which cleaning agents are used (synthetic detergents, dilute
hydrochloric acid, dilute sulfuric acid, dilute phosphoric acid)?
3. Was any special training provided for employees dealing with UV equipment?
4. How much time does it take to clean a unit? How many persons do the cleaning at a time?
5. How often does a sleeve or bulb get broken during cleaning?
6. How often are bulbs, sleeves, diodes, and ballasts replaced? .
7. How often and by what method does the system get calibrated?
C.4 COSTS ,
1. What was the cost of the system?
2. Were engineering, installation, and training included in the price? If not, what was the ,
additional cost?
3. What are the operation and maintenance costs? What are the labor requirements (hours per
week) and costs? . .
4. If the system is equipped with telemetry control, what was the cost?
C.5 ON-SITE CONTACT
1. Contact name, phone number, and address
UV Light Disinfection Technology in
Drinking Water Application—An Overview
C-2
Final—September 1996
-------
APPENDIX D. REGULATIONS AND STANDARDS FOR DRINKING
WATER DISINFECTION USING ULTRAVIOLET LIGHT
D. INTRODUCTION
This appendix provides available regulations and standards regarding the use of ultraviolet light for
drinking water disinfection. This appendix includes the 1966 U.S. Department of Health, Education, and
Welfare (DREW) policy statement on the use of ultraviolet light for water disinfection (copies provided
by Ideal Horizons, Inland Atlantic Ultraviolet Corporation). Also, this appendix presents ultraviolet light
regulations, guidance, and standards used in .the States of Utah, Wisconsin, Pennsylvania, and New Jersey.
In addition, Sections 1 through 6 and the preface of the ANStfNSF Standard 55-1991 are presented in this
appendix. These excerpts are reprinted with permission from NSF International. All the regulations,
guidance, and standards are copied verbatim and seriatim from documents provided by the respective
State's drinking water supervision managers. -
UV Light Disinfection Technology in
Drinking Water Application—An Overview
D-l
Final—September 1996
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Appendix D. Regulations and Standards for Drinking Water Disinfection Using Ultraviolet Light
D.1 DEPARTMENT OF HEALTH, EDUCATION, AND WELFARE
[April 1, 1966]
DEPARTMENT OF HEALTH, EDUCATION, AND WELFARE
PUBLIC HEALTH SERVICE
Division of Environmental Engineering and Food Protection
Policy Statement on Use of the Ultraviolet Process for Disinfection of Water
The use of the ultraviolet process as a means of disinfecting water to meet the bacteriological requirements
of the Public Health Service Drinking Water Standards is acceptable provided the equipment used meets
the criteria described herein.
In the design of a water treatment system, care must be exercised to insure that all other requirements of
the Drinking Water Standards relating tp the Source and Protection, Chemical and Physical Characteristics,
and Radioactivity are met. (In the case of an individual water supply, the system should meet the criteria
contained in the "Manual of Individual Water Supply Systems", Public Health Service Publication # 24.)
The ultraviolet process for disinfecting water will not change the chemical and physical characteristics of
the water. Additional treatment, if otherwise dictated, will still be. required, including possible need for
residual disinfectant^ in the distribution system.
Color, turbidity, and organic impurities interfere with the transmission of ultraviolet energy and may
decrease the disinfection efficiency below levels requked to insure destruction of pathogenic organisms.
It may be necessary to pretreat some supplies to remove excess turbidity and color. In general, units of
color and turbidity are not adequate measures of the decrease that may occur in ultraviolet energy
transmission. The organic nature of materials present in waters can give rise to significant transmission
difficulties. As a result, an ultraviolet intensity meter is required to measure the energy levels to which
the water is subjected. •
Ultraviolet treatment does not provide residual bactericidal action. Therefore, the need for periodic
flushing and disinfection of the'water distribution system must be recognized. Some supplies may require
routine chemical disinfection, including the maintenance of a residual bactericidal agent throughout the
distribution system.
UV Light Disinfection Technology in
Drinking Water Application—An Overview D-2 Final—September 1996
-------
Appendix D. Regulations and Standards for Drinking Water Disinfection Using Ultraviolet Light
D.1 DEPARTMENT OF HEALTH, EDUCATION, AND WELFARE (CONTINUED)
Criteria for the Acceptability of an Ultraviolet Disinfecting Unit
1. Ultraviolet radiation at a.level of 2,537 Angstrom units must be applied at a minimum dosage of
16,000 microwatt-seconds per square centimeter at all points.throughout the water disinfection
chamber.
2. Maximum water depth in the chamber, measured from the tube surface to the chamber wall, shall
not exceed three inches. - '
3. The ultraviolet tubes shall be:
A. Jacketed so that a proper operating tube temperature of about 105°F is maintained.
B. The jacket shall be of quartz or high silica glass with similar optical characteristics.
4. A flow or time delay mechanism shall be provided to permit a two minute tube warm-up period
before water flows from the unit.
5. The unit shall be designed to permit frequent mechanical cleaning of the water contact surface of
the jacket without disassembly of the unit.
6. An automatic flow control valve, accurate within the expected pressure range, shall be installed to
restrict flow to the maximum design flow of the treatment unit.
7. An^ accurately calibrated ultraviolet intensity meter, properly filtered to restrict its sensitivity to the
disinfection spectrum shall be installed in the wall of the .disinfection chamber at the point of
greatest water depth from the tube or tubes. •
8. A flow diversion valve or automatic shut-off valve shall be installed which will permit flow into
the potable water system only when at least the minimum ultraviolet dosage is applied. When
power is not being supplied to the unit, the valve should be in a closed (fail-safe) position which
prevents the flow of water into the potable water system.
9. An automatic, audible alarm shall be installed to warn of malfunction or impending shutdown if
considered necessary by the Control or Regulatory Agency.
10. The materials of construction shall not impart toxic materials into the water either as a result of the
presence of toxic constituents in materials of construction or as a result of physical of [sic] chemical
changes resulting from exposure to ultraviolet energy.
11. The unit shall be designed to protect the operator against electrical shock or excessive radiation.
UV Light Disinfection Technology in
Drinking Water Application—Ah Overview D-3 Final—September1996
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Appendix D. Regulations and Standards for Drinking Water Disinfection Using Ultraviolet Light
D.1 DEPARTMENT OF HEALTH, EDUCATION, AND WELFARE (CONTINUED)
As with any potable water treatment process, due consideration must be given to the reliability, economics,
and competent operation of the disinfection process and related equipment, including:
1. Installation of the unit in a protected enclosure not subject to extremes of temperature which cause
malfunctions. • •
2. Provision of a spare ultraviolet tube and other necessary equipment to effect prompt repair by
qualified personnel properly instructed in the operation and maintenance of the equipment.
3. Frequent inspection of the unit and keeping a record of all operations, including maintenance
problems. . ' .
UV Light Disinfection Technology in
Drinking Water Application—An Overview D-4 Final—September 1996
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Appendix D. Regulations and Standards for Drinking Water Disinfection Using Ultraviolet Light
D.2 UTAH
R309 Drinking Water Regulations
Utah Department of Environmental Quality,
Division of Drinking Water
R309-107-9. Ultraviolet Light.
Proposals for use of ultraviolet disinfection should be discussed with the Division of Drinking Water prior
to the preparationi of final plans and .specifications.
Secondary disinfection and maintenance of the required residual will.be necessary where disinfection of
the supply is required.
Ultraviolet disinfection will be permitted where the design conforms to the minimum recommendations
of the U.$. Public Health Service listed below. .
(1) Ultraviolet radiation at a level of 2,537 Angstrom units mus~t be applied at a^minimum dosage of
16,000 microwatt-seconds per square centimeter per second (1,600 Finsen Units), at all points
throughout the water disinfection chamber. .
(2) Maximum water depth in the chamber, measured .from the tub surface to the chamber wall, shall
not exceed three inches. •
(3) The ultraviolet tubes shall be:
(a) Jacketed so that a proper operating tube temperature of about 105 degrees F is maintained.
(b) The jacket shall be of quartz, or high silica glass wim similar optical characteristics.
(4) A flow or time delay mechanism shall be provided to permit a two minute tube warm-up period
before water flows from the unit.
s
(5) The unit shall be designed to permit frequent mechanical cleaning of the water contact surface of
the jacket without disassembly of the unit.
(6) An automatic flow control valve, accurate within the expected pressure range, shall be installed to
restrict flow to the maximum design flow of the treatment unit. • f
(7) An accurately calibrated ultraviolet intensity meter, properly filtered to restrict its sensitivity to the
disinfection spectrum, shall be installed in the wall of the disinfection chamber at the point of
greatest water depth from the tube or tubes. .
UV Light Disinfection Technology in
Drinking Water Application—An Overview D-5 Final—September 1996
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Appendix D. Regulations and Standards for Drinking Water Disinfection Using Ultraviolet Light
D.2 UTAH (CONTINUED)
(8) A flow diversion valve or automatic shut-off valve shall be installed which will permit flow into
the potable water system only when at least the minimum ultraviolet dosage is applied. When
power is not being supplied to the unit, the valve should be in a closed position which prevents the
flow of water into the potable water system.
(9) An automatic, audible alarm shall be installed to warn of malfunction or impending shutdown.
(10) The materials of construction shall not impart toxic materials into the water either as a result of the
presence of toxic constituents in materials of construction or as a result of physical or chemical
changes resulting from exposure to ultraviolet energy.
(11) The unit shall be designed to protect the operator against electrical shock or excessive radiation.
(12) As with any potable water treatment process, due consideration must be given to the reliability,
economics, and component operation of the disinfection process and related equipment, including:
(a) Installation of the unit in a protected enclosure not subject to extremes of temperature which could
cause malfunction.
(b) Provision of a spare UV tube and other necessary equipment to effect prompt repair by qualified
personnel properly instructed in the operation and maintenance of the equipment.
UV Light Disinfection Technology in
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P- Regulations and Standards for Drinking Water Disinfection Using Ultraviolet Light
D.3 WISCONSIN
, Department of Natural Resources Criteria for
Ultraviolet (UV) Water Treatment Devices
. for Private and Non-Community Public Water Supplies
To Control Microbiological Contamination
November 17, 1995 , .
.Introduction
The Department'has historically required use of wells that naturally produce bacteriologically safe water.
The rational is that micrqbiologically safe groundwater provides the best long-term public health
protection. The potential for providing a naturally safe water source must be fully evaluated and found
to be impracticable before a treatment process caii be approved by the Department.
., •- -'"'"'. ' • '' /
This document^contains information about UV treatment design criteria for microbiologically contaminated
private and non-community public water supplies. It contains general information and guidance, specifies
when DNR approval is required, lists information that is to be submitted for DNR approval and lists likely
approval conditions. Refer, to the well code, Chapter NR 812, Wis. Adm., Code, specifically ss. NR
812.09 and NR 812.37, for specific administrative code requirements. :
General
Well owners may install a UV water treatment system on a safe water supply without Department
approval. The Department recommends that the owner comply with the design criteria specified in the
remainder of this document. Unsafe water supply wells eligible for UV treatment are those that have
confirmed positive test results for total coliform or Escherichia coli bacteria more than once, have failed
three attempts at batch chlorination to eliminate the problem and which do not appear to be correctable
by well reconstruction or replacement.
Wells where treatment is proposed for microbiological contamination shall comply with chapter NR 812,
Wis. Adm. "Code requirements. The well depth and depth of casing must be determined from the well
construction report or an actual measurement. Casing depths shall meet either the special casing
requirement-for the area or be extended to a greater depth than the present special casing requirement.
An exception may be made when the Department agrees that there is a low probability of acquiring safe
water at a greater depth. In this case, the required minimum well casing depth shall be determined on a
/ case-by-case basis.
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Appendix D. Regulations and Standards for Drinking Water Disinfection Using Ultraviolet Light
D.3 WISCONSIN (CONTINUED)
Private residential UV water treatment devices serving one or two dwellings must be approved by the
Department of Industry, Labor and Human Relations (DILHR) prior to installation or sale. Installation.
-must be made according to manufacturers printed instructions and Chapters BLHR 81 through 86,
Wisconsin Administrative Code. An owner may install the treatment device on their residence. A
licensed pump installer or plumber is required for installation on rented property that an owner does not
occupy and for non-community systems. Contracted work shall be done by a licensed pump installer if
the device will be installed before the pressure tank. A licensed plumber must install the equipment after
the pressure tank. All work must comply with applicable code requirements.
Water .Quality Characteristics
The water supply shall be analyzed for the following water quality parameters and the results shall be
included in the UV application. Pretreatment is required for UV installations if the water quality exceeds
any of the following maximum limits. When an initial sample exceeds a maximum limit, a check sample
shall be taken and analyzed.
Parameter
Color • ,
Dissolved Iron
Dissolved Manganese
Hardness
Hydrogen Sulfide
Iron Bacteria
PH
Suspended Solids
Turbidity
Total Coliform
Escherichia coli
Maximum
15 APHA units
0.3 mg/L
0.05 mg/L
120 mg/L
Non-Detectable
None
6.5 to 9.5
10 mg/L
5.0 NTU,
1,000 Colonies/100 mg/L
100 .
Preferred
No APHA units
<0.01 mg/L
<0.0004mg/L
17.1 mg/L
Same
Same
Same
<1 mg/L
1.0 NTU
Raw water quality shall be evaluated and pretreatment equipment shall be designed to handle water quality
changes. Turbidity caused by rainfall events is of special concern.
UV with Microfiltration Approval Process
DNR approval is required prior to installation of a UV water treatment device on a microbiologically
unsafe water supply.
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Appendix D. Regulations and Standards for Drinking Water Disinfection Using Ultraviolet Light
D.3 WISCONSIN (CONTINUED)
1. 'The owner must sign a short statement describing the steps taken to correct the microbiological
problem and send it along with the application to:
DNR Private Water Supply WS/2
Box 7921 ,
Madison, WI 53707-7921
2. The DNR win review the application for completeness. Incomplete materials will be returned
Disapproved applications will be returned to the applicant with the reasons for disapproval There is no
fee for reviewing the application.
3. Installation of the DNR approved water treatment system may proceed subject to approval
conditions. Most approvals require: ,
a. Installation according to the submitted plans and approval conditions.
' •. b. Initial sampling of raw water and treated water at startup and a routine sampling program.
c. Routine maintenance requirements.
.d. Non-Community public water supply systems will be required to submit periodic reports of
sample results and maintenance actions to the Department.
Application
The information that is required for a complete application is found in the attached outline. The
Department asks that you take the time to obtain the information specified and be as complete as possible
in your application. Information as requested in item #5 on the attached outline about .the depth of well
casing, casing integrity and the well's .total depth must be obtained in order to evaluate the request. In
addition, the water quality data specified in item #6 on the attached outline is critical in designing a UV
water treatment system. Attached are the UV specifications that must be met in order for the Department
to approve the installation of the water treatment device(s) on a microbiologically unsafe water supply.
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Appendix D. Regulations and Standards for Drinking Water Disinfection Using Ultraviolet Light
D.3 WISCONSIN (CONTINUED)
Application Content
1. Property Owner: .
2. Water Treatment Device,
Operator:
3, Property Location and Legal
Description:
4. Property Map:
5. Well Description:
6. Water Quality:
7. Water Quantity:
Include the name, mailing address, and telephone number.
Provide the name, mailing address and telephone number
of the water treatment device operator if different from
owner above.
Provide the village or city street and number or if rural,
the road and fire number and the legal description
including the 1A1A Section, V* Section, Section number,
Town and Range numbers, and County.
Locate the property on a map. A plat map or topographic
map is acceptable.
Provide a copy of the well construction report if available.
If not available, provide the following information:
a. The approximate date of well construction,
b. The total depth of the well and
c. The depth of the casing in the well.
d. A copy of an inspection report showing compliance
.of the well and pumping system with Chapter
NR812. !
Results of the following well water quality tests collected
at the well sampling faucet:
a. Total coliform bacteria,
b. E-Coli bacteria,
c. Iron bacteria, •
d. Color,
e. Dissolved iron,
f.- Dissolved'manganese, • .
' g. Hardness,
h. Hydrogen sulfide if odor is present,
i. pH,
j. Suspended solids,
k. Turbidity
These tests shall be performed by a state Safe Drinking
Water Act certified laboratory.
Measure or estimate the average daily water usage in
gallons. Indicate the pump capacity in gallons per
minute.
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Appendix D. Regulations and Standards for Drinking Water Disinfection Using Ultraviolet Light
D.3 WISCONSIN (CONTINUED)
8.
Water Distribution System
Sketch:
9.
Water Treatment Device or
System Installation Information:
10. Maintenance Program:
Provide a sketch of the water distribution system from the
well to the final treated water distribution point including
the location of any sampling faucets, pressure gauges,
shutoff valves, by-pass piping, pressure tanks, any other
treatment devices, and the proposed location of the water
treatment device or water treatment system.
Provide the name of the manufacturer, the product name
and model number.
Describe the required maintenance for the UV water
treatment device and any pretreatment devices to be
installed. Provide a copy of any maintenance and
operational agreements. Specify the responsible party for
maintaining the water treatment system.
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Appendix D. Regulations and Standards for Drinking Water Disinfection Using Ultraviolet Light
D.3 WISCONSIN (CONTINUED)
DESIGN AND OPERATIONAL CRITERIA
FOR POINT-OF-ENTRY INSTALLATIONS USING ULTRAVIOLET (UV) FOR PRIVATE AND
NON-COMMUNITY WATER SUPPLY SYSTEMS.
The following are Wisconsin Department of Natural Resources (WDNR) criteria for installation,
monitoring and replacement requirements for consideration of UV treatment of a microbiologically unsafe
water for private and non-community public water supplies. The following criteria must be met in order
to install a UV water treatment device on a bacteriologically unsafe water supply well.
A. CRITERIA FOR UV WATER TREATMENT DEVICES
1. UV water treatment devices must comply with Class A criteria under the American National
Standard Institute (ANSI)/National Sanitation Foundation (NSF) Standard 55 - Ultraviolet
Microbiological Water Treatment Systems; Residential UV models shall be approved by the
Department of Industry, Labor and Human Relations (DILHR); each UV water treatment device
shall meet the following standards;
a. Ultraviolet radiation at an [sic] wavelength of 253.7 nanometers shall be applied at a
minimum dose of 38,000 microwatt-seconds per square centimeter (uW-sec/cm2) at the failsafe set
point at the end of lamp life;
b. The UV device shall be fitted with a lamp viewing port to safely visually verify
electrical operation of the lamp(s);
c. The UV light assembly shall be insulated form direct contact with the influent water
by a lamp jacket and the lamp and lamp jacket shall be replaceable; '
d. An automatic fixed flow rate control shall be provided to prevent flow above the
manufacturer's maximum rated flow over the manufacturer's recommended operating pressure
range; • . •,
e. The UV assemblies shall be accessible for visual observation, cleaning and replacement
of the lamp jackets and sensor window/lens;
f. The ultraviolet tube(s) shall be 1) jacketed so that a proper operating lamp temperature
of about 104 degrees Fahrenheit is maintained and 2) the jacket shall be of quartz or high silica
glass with similar optical and strength characteristics;
g. A narrow band UV monitoring device shall be provided. It shall be accurately
calibrated to 253.7 nanometers and installed at the point of greatest water depth. The device shall
trigger an audible alarm in the event the sensor or lamp fails or if insufficient dosage is detected
as defined in item "a" above;
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Appendix D. Regulations and Standards for Drinking Water Disinfection Using Ultraviolet Light
D.3 WISCONSIN (CONTINUED)
h. An automatic shutdown valve shall be installed ahead of the UV treatment system that
will be activated whenever the water treatment-system loses power or is tripped by a monitoring
device when me dosage drops below 38,000 uW-sec/cm2.
i. The UV housing shall be stainless steel 304 or 316L;
2. A flow delay mechanism shall be provided to permit a sufficient time for tube warm-up per
manufacturer recommendations before water flows from the unit upon startup.
3. Identical parallel UV treatment systems shall be provided at public water systems to provide
a continuous water supply when one unit is out of service;
4. No bypasses shall be installed;
5. All water from the well shall be treated; •
6. The well pump shall have adequate pressure capability to maintain minimum water system
pressure after the water treatment devices; ;
B. PRETREATMENT '
1. •• A 5 micron sediment prefilter shall be installed before the UV device. The filter model shall
be approved by DILHR" if installed on a residential water supply; ,
2. A filter rated for cyst reduction shall be installed before the UV device. The filter shall be'
approved by DILHR if installed on a residential 'water supply;
3. The prefilter and cyst reduction filter shall be replaced when the pressure loss across an in
use filter has increased by 10 psig above a clean new filter at the manufacturers rated service flow
rate. • •. .
4. Other pretreatment water treatment devices may be necessary depending on source water
quality.
C. REQUIRED ONGOING WATER QUALITY MONITORING
Total coliform monitoring will be used to evaluate UV treatment effectiveness. The monitoring
frequency will be as follows:
Startup and 2 weeks after start up - one raw and one treated sample - all systems
Monthly thereafter for all public water systems - raw and treated
Private water system owners are encouraged, but not required, to routinely monitor effectiveness
of the water treatment system.
' Monitoring for additional parameters or total coliform on an increased frequency may be required
by the Department on a case-by-case basis.
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Appendix D. Regulations and Standards for Drinking Water Disinfection Using Ultraviolet Light
D.3 WISCONSIN (CONTINUED)
D. OVERSIGHT AND MONITORING
UV light intensity of each installed unit shall be monitored continuously., Treatment units and the
water system shall automatically shutdown if the UV dosage falls below the required output of
38,000 uW-sec/cm*. Water systems that have a large variation in the turbidity of the water source
may be required to install a turbidimeter ahead of the UV water treatment device. An automatic
shutdown valve shall be installed and operated in conjunction with the turbidimeter. Each owner
shall have at least one replacement lamp, quartz sleeve, 5 micron replacement, filter and cyst
reduction filter available onsite.
E. SEASONAL OPERATIONS
UV water treatment devices that are operated on a seasonal basis shall be inspected and cleaned
prior to use at the start of each operating season. All prefilters shall be replaced prior to start up
of the water supply system after a shut down of greater than three months. The UV water treatment
system including the filters shall be disinfected prior to placing the water treatment system back into
operation. A procedure for shutting down and starting up the UV treatment system shall be
developed for or by each owner based upon manufacturer recommendations and submitted in
writing to the department. *
F. APPLICATION, RECORD KEEPING and ACCESS
A record shall be kept of the water quality test data, dates of lamp replacement and cleaning, a
record of when the device was shutdown and the reason for shutdown, and the dates of prefilter
replacement.
Department representatives shall have access to the UV water treatment system and records.
Non-community wajer systems will be required to submit operating reports and required sample
results on a monthly or quarterly basis as described in the conditions of approval.
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Appendix D. Regulations and Standards for Drinking Water Disinfection Using Ultraviolet Light
D.4 PENNSYLVANIA
? '
Public Water Supply Manual - Part IV
Noncommunity System Design Standards
Pennsylvania Department of Environmental Protection
3.3 Ultraviolet Irradiation (UV)
Ultraviolet light produced by UV lamps has been shown to be effective bactericide for certain
pathogenic bacteria. However, the department does not consider the use of UV acceptable for the
inactivation of Giardia lamblia. Only UV systems approved as Class A units under the National
Sanitation Foundation (NSF) Standard 55 - Ultraviolet Water Treatment Systems are acceptable for
use in drinking water disinfection.
Ultraviolet light disinfection will be considered only for small nonresidential water supplies and in
certain special cases where other methods are not considered feasible. As ultraviolet treatment does
not provide a residual disinfectant, post-chlorination may be required to maintain safe water in the
system. , ~ •
UV system or component shall be designed and constructed so that its intended purpose shall be
accomplished when installed and operated according to the manufacturer's instructions.
Components shall not be adversely affected by the normal environment to which they are subjected.
Normal environment shall include usual vibration, shock, climate condition and cleaning procedures
as prescribed by the manufacturer.
3.3.1 Materials
- - . •••• V '• - •-- ''• ~, '-•'; • '
, The materials in contact with water must not impart undesirable taste, odor, color, and/or
toxic materials into the water as a result of the presence of toxic constituents in materials of
construction or as a result of physical or chemical changes resulting from exposure from
ultraviolet energy. Materials exposed to ultraviolet irradiation shall be formulated to resist
deterioration and shall not impart undesirable tastes, odor, color, and/or toxic chemicals to
the water upon irradiation.
Systems and/or components shall be constructed of materials suitable to withstand
temperatures generated during sustained periods when the unit is not in use.
3.3.2 Design Criteria
The use of UV devices as a means of disinfection of public water supplies in Pennsylvania
is acceptable provided the equipment used meets the design criteria described herein:
1. Ultraviolet radiation at a level of 2,537 Angstrom units must be applied at a minimum
dosage of 16,000 microwatt-seconds per square centimeter at all points throughout the
, water disinfection chamber; .
2. The UV system or component shall be provided with a visual means to verify
.electrical operation of lamps;
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Appendix D. Regulations and Standards for Drinking Water Disinfection Using Ultraviolet Light
D.4 PENNSYLVANIA (CONTINUEQ)
3. UV lamp assemblies shall be designed to be insulated from direct contact with the
influent water. If the ultraviolet lamps or assemblies are intended to be replaced, they
shall be removable;
4. The unit is to have an automatic flow control device, accurate within the expected
range of operating pressures, so that the maximum design flow rate of the unit is not
exceeded;
5. The systems and all components subject to line pressure shall be designed for a
working pressure of at least 689 kPa'(100 psig);
6. The system or component' shall be designed to be accessible for cleaning and
replacement of the lamp jackets and sensor window/lens which are provided on the
systems. The manufacturer's cleaning procedures shall result in thorough cleaning of
the system. The treatment chamber shall be designed so that at least one end can be
dismounted for cleaning.
7. Maximum water depth in the chamber measured from the tube surface to chamber wall
must not exceed three inches; . .
8. The ultraviolet tubes must be: • '
a. Jacketed so that a proper operating tube temperature of about 105° F is.
maintained,
b. The jacket shall be of quartz or high silica glass with similar optical
characteristics; :
9. A flow or time delay mechanism is to be provided to permit a two minute tube warm-
up period before water flows from the unit;
10. An accurately calibrated ultraviolet intensity meter, properly filtered to restrict its
sensitivity to the disinfection chamber at the point of greatest water depth from the
tube(s) shall be provided;
11. A flow diversion valve or automatic shut-off valve is to be installed which permits
flow into the potable water system only when at least the minimum ultraviolet dosage
is applied. When power is not being supplied to the unit, the valve should be in a
closed (fail-safe) position which prevents the flow of water into the potable water
system; '
12. The unit must incorporate a device for monitoring or sending ultraviolet transmission
or intensity through the maximum depth of water in the chamber during operation.
The monitoring or sensing device is to be installed that triggers an audible alarm hi
the event of lamp or sensor failure or if insufficient ultraviolet light reaches the sensor;
13. The unit must protect the operator against electrical shock or excessive ultraviolet
energy;
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Appendix D. Regulations and Standards for Drinking Water Disinfection Using Ultraviolet Light
D.4 PENNSYLVANIA (CONTINUED)
14. The operation of the ultraviolet light unit shall be synchronized with the operation of
the well pump. ,
3.3.3 Installation ,
1. The unit should be installed in a protected enclosure not subject to extremes of
temperature which could cause malfunction. .
2. Spare UV tubes and other necessary equipment are to be provided to effect prompt
repair by qualified personnel properly instructed in the operation and maintenance of
.the equipment. ,
"3. The unit is to be installed so as to allow ease of access for disassembly, repairs, or
replacement. ' ' •
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Appendix D. Regulations and Standards for Drinking Water Disinfection Using Ultraviolet Light
D.5 NEW JERSEY
NEW JERSEY PROPOSED REGULATIONS FOR DISINFECTION
BY ULTRA-VIOLET LIGHT AS APPEARED IN THE NEW JERSEY REGISTER
CITE 27 NJ.R.4112 NOVEMBER 6,1995
(c) Regulations for disinfection by ultra-violet light are as follows:
1. Ultra-violet tubes shall be jacketed so that a temperature of 105 degrees Fahrenheit is maintained.
2.
4.
5.
6.
7.
The jacket on the ultra-violet light tubes shall be quartz or high-silica glass with similar optical
characteristics.
3. The ultra-violet light disinfection unit shall be designed to permit frequent mechanical cleaning of
the water contacts surface of the ultra-violet tube jacket without disassembly of the unit.
The maximum water depth in the disinfection chamber, measured from the ultra-violet light tube
surface to the outer walls of the chamber, shall not exceed three inches.
Ultra-violet radiation at a level of 2,537 Angstrom shall be applied at all points throughout the
disinfection chamber at a minimum rate of 16,000 microwatt seconds per square centimeter.
An automatic flow control valve, accurate within the expected pressure range, shall be installed to
restrict flow to the maximum design flow of the ultra-violet disinfection unit.
An accurately calibrated ultra-violet light intensity meter, filtered to confine its sensitivity to the
range of disinfection spectrum, shall be installed in the wall of the disinfection chamber at the point
of greatest water depth from the light transmitting source.
8. A flow diversion valve or automatic shut-off valve controlled by the ultra-violet light intensity
meter shall be installed so as to permit water flow into the water system only when the minimum
radiation level specified at (c)5 is applied. When power is not being supplied to the unit, the valve
shall be in a closed (fail-safe) position to prevent the flow of water into the water system.
9. The ultra-violet light disinfection unit shall be installed in a manner such that it cannot be bypassed.
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Appendix D. Regulations and Standards for Drinking Water Disinfection Using Ultraviolet Light
D.6 ANSI/NSF STANDARD 55-1991
STANDARD55
FOR
ULTRAVIOLET MICROBIOLOGICAL WATER TREATMENT SYSTEMS
PREFACE
, This standard was developed for the purposes of establishing reliable methods for determining the
performance,of point-of-entry and point-of-use ultraviolet water treatment systems designed to reduce
specific contaminants from public or private water supplies, Systems covered by this standard are in
keeping with the Report of Task Force on Guide Standard and Protocol for Testing Microbiological Water
Purifiers, April 1987.l .
It is recognized that the federal, state and local objective is to provide a safe water supply without user
treatment. However, many users are faced with the presence of contaminants of both aesthetic and health
concern in their water supply and need guidance as to the availability of tested and certified point-of-entry
and point-of-use ultraviolet water treatment systems. This standard will help to'meet this need, but cannot
be expected to address claims beybnd those covered in this standard.
Since it was not economically feasible to mount a routine testing program using all of the target
microorganisms, e.g., bacteria, viruses, and protozoan cysts, an equivalent "disinfection" set of tests and
requirements were developed for point-of-use and point-of-entry ultraviolet disinfection systems.
A virus reduction of 4-log against a poliovirus and rotavirus challenge and a bacteriological reduction of
6-logs against a challenge of a coliform bacteria (Klebsiella terrigena) has been recommended by Schaub
and an expert task force (1987).2 ; ••' '
The technical and health protection problems (laboratory staff) and the inherent cost of establishing and
maintaining a live virus test program precludes its routine application in a multipurpose standards testing
laboratory. Consequently, an alternate means of assuring virus efficacy was developed.
Guide Standard and Protocol for Testing Microbiological Water Purifiers, Report of Task Force, submitted bv Steven
A. Schaub to the USEPA, April 1987. -
' '• ' ••.'-.• •.•••-,-•.'•'
~ 2Ibid.,p. 7. - ' • .
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Appendix D. Regulations and Standards for Drinking Water Disinfection Using Ultraviolet Light
D.6 ANSI/NSF STANDARD 55-1991 (CONTINUED)
Survival data for poliovirus and rotavirus (Chang, 1985)3, show between a 3 to 4-log reduction in both
poliovirus and rotavirus may be accomplished by a UV'dosage of 30,000 fiW-sec/cm2 while a greater than
6-log reduction of Escherichia coli may be projected. Additional data (Harris, 1986)4 shows a 5 log
reduction of poliovirus at 40',000 uW-sec/cm2. Consequently, a minimum UV dosage of 38,000 uW-
sec/cm2 at the failsafe setpoint is set as an equivalent 4-log virus reduction requirement.
Since ultraviolet light has limited cysticidal ability, information will be required for the use as to the need
for a prefflter complying with ANSI/NSF Standard 53: Drinking Water Treatment .Units - Health Effects
for cyst reduction.
Where drinking water is considered to be free of disease causing pathogenic organisms and has a turbidity
level within acceptable drinking water standards, ultraviolet treatment may be useful for the supplemental
treatment of this drinking water. It would be suitable for the reduction of normally occurring
microbiological flora (non-spore forming heterotrophic bacteria) commonly found in drinking water.
Survival data (Chang, 1985)5 show a greater than 2 log reduction of non-spore forming heterotrophic
bacteria may be accomplished by an ultraviolet dosage of 16,000 uW-sec/cm2. The yeast organism
Saccharomyces cerevisiae was chosen as the test challenge to allow for a reasonable influent concentration
and an easily measured reduction in the effluent. Most vegetative bacteria including cbliform species are
too susceptible to UV radiation at the dose range of 16,000 uW-sec/cm2 to allow for measurable testing.
This standard and the accompanying testing program will provide assurance to the use and the regulatory
officials that point-of-entry and point-of-use ultraviolet water treatment systems will perform, with proper
, operation and maintenance, in accordance with the claims made under the standard. However, final
acceptance of systems for any application covered under governmental regulation will be subject to the
approval of the appropriate federal, state, and/or local regulatory agency having jurisdiction.
*UV Inacdvation of Pathogenic and Indicator Microorganisms, Chang, J.C., Johnson, J. Donald, et al. Journal of
Applied Environmental Microbiology, Vol. 49, pp. 1361-1365, 1985.
*UV Inactivation of Selected Bacteria and Viruses With Photoreactivation of the Bacteria, Harris, D.'George Adams
Dean, et al., Water Resources, Vol, Vol. 21, pp. 687-692, 1986. .
slbid., p. 1362.
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Appendix D. Regulations and Standards for Drinking Water Disinfection Using Ultraviolet Light
D.6 ANSI/NSF STANDARD 55-1991 (CONTINUED)
SECTION 1. GENERAL
1-0 SCOPE: This standard covers ultraviolet (0V) microbiological water treatment systems and
components for point-of-use (POU) and point-of-entry (POE) applications. Systems are intended
to be used under the following specific conditions.
1.0.1 CLASS A SYSTEMS: Class A point-of-entry and point-of^use systems covered by this
standard are designed to disinfect and/or remove microorganisms from contaminated water
including bacteria and viruses, to a safe level. Systems covered by this standard are not
intended for the treatment of water that has an obvious contamination source, such as raw
sewage; nor are systems intended to convert wastewater to microbiologically safe drinking
. water. The systems are intended to be installed on visually clear water (not colored, cloudy,
or turbid). Systems intended for treatment of surface waters will need to be installed
downstream of a prefilter tested for cyst reduction in compliance with ANSI/NSF Standard
53: Drinking Water Treatment Units - Health Effects.
1.0.2 CLASS B SYSTEMS OR COMPONENTS: Class B poiht-of-use systems covered by this
standard are designed for supplemental bactericidal treatment of treatedand disinfected public
drinking water or other drinking water which has been tested and deemed acceptable for
human consumption by the state or local health agency having jurisdiction. The system is
designed to reduce normally occurring nonpathogenic or nuisance microorganisms only. The
Class B system is not intended for the disinfection of microbiologically unsafe water.
1.1 MINIMUM REQUIREMENTS: Variations from these minimum requirements may be permitted
if they make the system or component as resistant to corrosion, wear, and physical damage or if
they improve the general operation or performance of the system or component. Proposed
variations shall be accepted by the testing agency prior to use. Systems with components or
functions covered under existing NSF standards or criteria shall comply with those applicable
requirements. • *
•1.2 ALTERNATE MATERIALS: If specific materials are mentioned, other materials equally
satisfactory from the standpoint of performance and sanitation that meet the requirements of the
standard shall be acceptable.
1.3 REVIEWS AND REVISIONS: A. complete review of the standard shall be conducted at least every
five years. These reviews are to be conducted by representatives from the industry, public health
and user groups of the NSF Joint Committee on Drinking Water Treatment Units.
SECTIONS. DEFINITIONS
2.0 ACCESSIBLE: Fabricated to be exposed for cleaning and inspection using simple tools
(screwdriver, pliers, open-end wrench). >
i ' v - . . ' • . : - t
2.0.1 READILY ACCESSIBLE:' Fabricated to be exposed for cleaning and inspection without
using tools. •
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Appendix D. Regulations and Standards for Drinking Water Disinfection Using Ultraviolet Light
D.6 ANSl/NSF STANDARD 55-1991 (CONTINUED)
2.1 CHALLENGE WATER: The stream entering a component, system, or process.
2.2 CLASS A SYSTEMS: Systems qapable of producing an ultraviolet dosage at the failsafe setpoint )
equivalent to a dosage of 38,000 uW-sec/cm2.
2.3 CLASS B SYSTEMS: Systems capable of producing an ultraviolet dosage equivalent to" a dosage
of 16,000 jiW-sec/cm2 at 70 percent of the ultraviolet lamp normal output or at the failsafe point.
2.4 CORROSION RESISTANT MATERIAL: Capable of maintaining original surface characteristics
under prolonged contact with the use environment.
2.5 DISINFECTION: The action of removing, killing, or inactivating all types of disease-causing
microorganisms to render contaminated water safe for drinking.
2.6 DRINKING WATER: Water intended for human consumption.
2.7 EFFLUENT WATER: The stream emerging from a unit, system, or process.
2.8 FAILSAFE SET. POINT: The point at which the ultraviolet sensor activates the alarm.
2.9 FLOW CONTROL: An automatic flow control device which limits flow over a pressure range to
the specified flow rate for the system or component.
2.10 JOINING MATERIAL: Any substance used to produce a tight joint; e.g., solvent cements,
adhesives; or elastomeric seals.
2.11 NORMAL OUTPUT (CLASS B SYSTEMS): The UV dosage provided by the ultraviolet lamp
after a 100 hour conditioning period.
2.12 POINT-OF-ENTRY SYSTEMS:. A system used to treat all or part of the water for the facility at
the point of entry. For Class A systems a/acility shall be considered a single family dwelling.
2.13 POINT-OF-USE SYSTEMS: A system used to treat the water at a single tap or multi-taps, but not
for the entire facility. . , ,
2.14 REMOVABLE: Fabricated to be taken away from the system or component us.ing simple tools
(screwdriver, pliers, open-end wrench, etc.).
2.14.1 READILY (OR EASILY) REMOVABLE: Fabricated to be taken away from the main
system or component without using tools. .
2.15 SENSITIVITY CALIBRATION: A measured level of spore and/or yeast inactivation resulting from
the specified ultraviolet dose. (Term is synonymous with UV sensitivity.) , '• ,
2.16 TOXIC: Having an adverse physiological effect on humans.
2.17 TURBIDITY: A condition caused by the presence of suspended and/or colloidal matter, which
results in the scattering and/or absorption of light rays.
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Appendix D. Regulations and Standards for Drinking Water Disinfection Using Ultraviolet Light
D.6 ANSi/NSF STANDARD 55-1991 (CONTINUED)
2.18 ULTRAVIOLET SENSOR: The physical sensing system used to measure the intensity of
ultraviolet light (225-300 Nanometers [nm]) transmitted.
2.19 ULTRAVIOLET COMPONENT: the ultraviolet treatment lamp of an ultraviolet system.
2.20 ' WASTEWATER: Blackwaste and grey waste generated from residences, commercial buildings,
industrial plants, and institutions, and the water or medium used to transport it.
2.20.1 BLACKWASTE: Human and/or animal body waste, toilet paper, and any other
material intended to be deposited in and discharged therefrom a receptacle designed
;._ to receive urine and/or feces.
2.20.2 GREYWASTE: Waste materials, exclusive of urine, feces, or industrial waste,
deposited in and discharged therefrom plumbing Fixtures found hi residences'
commercial buildings, industrial plants, and institutions.
SECTIONS. MATERIALS
3.6 GENERAL: Materials in contact with water shall not impart undesirable taste, odor, color, and/or
toxic substances to the water when tested and evaluated in accordance with Annex A. Materials
used in me construction of systems or components shall be capable of withstanding exposure to the
intended use environment. Materials exposed to ultraviolet irradiation shall be formulated to resist
deterioration and shall not impart undesirable tastes, odor, color, and/or toxic chemicals to the water i
upon irradiation. , ,
3.1 TEMPERATURE RESISTANCE: Systems and/or components shall be constructed of materials
suitable to withstand temperatures generated during sustained periods of no water use.
3.2 CORRODIBLE MATERIALS-: Corrpdible materials shall be provided with a corrosion resistant.
protective coating completely covering all wetted surfaces.
3.3 GASKETS, O-RINGS, SHAFT SEALS, AND PACKING MATERIALS: Gaskets, o-rings, shaft
seals, and:packing materials shall conform to the applicable requirements of Item 3^0.
3.4 DISSIMILAR METALS: Dissimilar metals not normally considered compatible on the
electromotive scale shall not be in direct contact.
3.5 INSULATING FITTINGS: Insulating fittings shall be provided when materials are not compatible
on the electromotive scale with adjoining fittings or parts. '
3.6 PLASTICS: If plastics are exposed to UV light, the manufacturer shall provide data to substantiate
that the plastics meet the requirements of Items 3.0 and 3.1.
3.7 SOLDER: Solder and fluxes on water contact surfaces shall be hard solder and shall conform to
the requirements of Item 3.0. Lead based solders (0.2% lead or greater) shall not be used.
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Appendix D. Regulations and Standards for Drinking Water Disinfection Using Ultraviolet Light
D.6 ANSI/NSF STANDARD 55-1991 (CONTINUED)
3.8 WELDING: Welded seams and deposited Weld material shall meet the requirements of Items 3.0
and 3.4.
SECTION 4. DESIGN AND CONSTRUCTION
4.0 GENERAL: A system or component evaluated under this standard shall be designed >and
constructed so that its intended purpose will be accomplished when installed and operated according
to the manufacturer's instructions. (Components shall not be adversely affected by the normal
environment to which they are subjected. Normal environment shall include usual vibration, shock,
climate condition, and cleaning procedures as prescribed by the manufacturer. Systems and
components shall be designed to eliminate UV light exposure to humans when operated and
serviced according to manufacturer's recommendation.
4.1 LAMP OPERATION INDICATION: The UV system or component shall be provided with a visual
means to verify electrical operation of all lamps.
4.2 UV LAMP ASSEMBLIES: UV lamp assemblies shall be designed to be insulated from direct
contact with the influent water. If the UV lamps or assemblies are intended to be replaced,'they
shall be removable.
4.3 FLOW CONTROL: An automatic fixed flow rate control shall be provided to prevent flow above
the manufacturer's maximum rated flow over the manufacturer's recommended operating pressure
range. • .
4.4 PERFORMANCE INDICATION: Class A systems shall be equipped with an UV sensor to monitor
UV transmission or intensity through the water during operation. A visual and/or auditory alarm
shall be used to indicate ineffective operation. A system that terminates discharge when ineffective
operation occurs shall be considered as meeting this requirement. Class B systems or components
" are exempt from these requirements. If an alarm is provided on a Class B system to measure UV
transmission the alarm shall comply with Item 4.4.1. . .
4.4.1 The alarm shall operate for at least 100 on-off cycles when tested in accordance with Annex
F-
4.5 ELECTRICAL REQUIREMENTS: Systems and components shall be accepted by a recognized
electrical testing laboratory (Underwriters Laboratories [UL] or equivalent) when applicable.
Certification of conformance shall be provided by the manufacturer.
4.6 WORKING PRESSURE: The systems, and all components subject to line pressure, shall be
designed for a working pressure of at least 689 kPa (100 psig).
4.7 LAMP REPLACEMENT (CLASS B SYSTEMS): The recommended lamp replacement intervals
for Class B systems shall be verified by submittal of intensity vs. time curves. The intensity shall
be measured at 254 nm at a distance of 1 m (3.3 ft,).
4.8 MAINTENANCE: The system or component shall be designed to be accessible for cleaning and
replacement of the lamp jackets and sensor window/lens provided, on the systems. The
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Appendix P. Regulations and Standards for Drinking Water Disinfection Using Ultraviolet Light
D.6 ANSI/NSF STANDARD 55-1991 (CONTINUED)
manufacturer's cleaning procedures shall result in thorough cleaning of the system. The treatment
chamber shall be designed so that at least one end can be dismounted for cleaning.
SECTIONS. PERFORMANCE
5.0 GENERAL: Systems and components covered under this standard shall be designed to meet the
microbiological performance requirements at the manufacturer's recommended operating pressures
and flow rates.
5.1 STRUCTURAL INTEGRITY PERFORMANCE: Systems and components shall comply with the
following, structural integrity performance requirements when tested in accordance with Annex E.
5.1.1 Units with permanent pressure vessels less than 203 mm (8 in.) in diameter subject to line
pressure shall conform to the foUowing requirements:
"• Complete assemblies shall withstand a hydrostatic test pressure of 2.4 times the
working pressure or 1654 kPa,(240 psig), whichever is greater, for a period of 15
minutes without leakage of water from the unit.. - - .
Metallic pressure vessels shall withstand a hydrostatic test pressure of 24 times the
working pressure or 1654 kPa (240 psig), whichever is greater, for a peri9d of 15
minutes without excessive permanent distortion, defined as an increase in vessel
circumference more than 0.2 percent of the original circumference or top or bottom
head deflection more than 0.5 rpercent of the tank diameter.
* Nonmetallic pressure vessels shall have a burst pressure of at least 4.0 times the
.working pressure or 2756 kPa (400 psig), whichever is greater.
Nonmetallic pressure vessels shall be watertight at 1034 kpa (150 psig) and after a
minimum of 100,000 pressure cycles of 0 to 1034 kPa (0 to 150 psie) at 20 ± 2 5° C
(68±5°F). . " ' . • ,
Valves and controls subject to line pressure shall be watertight at 1034 kPa (150 psig)
and after a minimum of 100,000 pressure cycles of 0 to 1034 kPa (0 to 150 psig) at
20 ± 2.5° C (68 ± 5° F). , -
5.1.2 Units with permanent pressure vessels 203 mm (8 in.) and greater in diameter subject to line
pressure shall conform to the following requirements:
• Complete assemblies shall withstand a hydrostatic test pressure of 1.5 times the
working pressure or 1034 kPa (15p psig), whichever is .greater, for a period of 15
minutes without leakage of water from the unit.
Metallic pressure vessels shall withstand a hydrostatic test pressure of 1.5 times the
working pressure or 1034 kPa (150 psig), whichever is greater, for a period of 15
minutes without excessive permanent distortion, defined as an increase in tank
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Appendix D. Regulations and Standards for Drinking Water Disinfection Using Ultraviolet Light
D.6 ANSI/NSF STANDARD 55-1991 (CONTINUED)
circumference more than 0.2 percent of the original circumference, or top or bottom
head deflection more than 0.5 percent of the vessel diameter.
• Nonmetallic pressure vessels shall have a burst pressure of at least 4.0 times the
working pressure or 2756 kPa (400 psig), whichever is greater.
5.1.3 DISPOSABLE PRESSURE VESSELS: Disposable pressure vessels and. all replaceable
components subject to line pressure shall meet the following requirements:
• Disposal pressure vessels and replaceable components shall withstand a hydrostatic test
pressure of 2.4 times the working pressure or 1654 kPa (240 psig), whichever is
greater, for a period of 15 minutes without leakage of water from the unit.
• Disposable pressure vessels and replaceable components shall be water-tight and show ,
no evidence of failure after being subjected to 10,000 pressure cycles of 0 to 1034 kPa
(0 to 150 psig) at 20 ± 2.5° C (68 ± 5° F).
5.1.4 UNITS DESIGNED FOR OPEN DISCHARGE: All components subject to pressure,
including connecting tubing where required, shall meet the following requirements:
• Complete assemblies, with the outlet plugged, shall withstand a hydrostatic test
pressure of 1.2 times the working pressure or 867 kPa (120 psig), whichever is greater,
for a period of 15 minutes without leakage of water from the unit.
I
• Complete assemblies, with the outlet plugged, shall be watertight at 344 kPa (50 psig)
after a minimum of 10,000 cycles of 0 to 344 kPa (0 to 150 psig) at 20 ± 2.5° C (68
±5°F).
5.1.5 PORTABLE UNITS: Portable units, not designed for direct pressurized connection to a
water line, shall meet the following hydrostatic requirements:
f
• Units designed to be pressurized by the user shall withstand a hydrostatic test pressure
of 1.5 times the working pressure for a period of 15 minutes without leakage of water
. from the unit. . , • . •
• Units designed for only atmospheric (open) pressure or only gravity flow shall be
exempted from hydrostatic tests, but shall be water-tight in normal use.
5.2 SENSmVITY CALIBRATION: Spore and/or yeast sensitivity calibration (UV sensitivity) shall
be determined in accordance with Annex B prior to conducting performance testing in accordance
with Annex C or D.
5.3 DISINFECTION PERFORMANCE: Disinfection performance for a-Class A system shall provide
a minimum UV dose equivalent to 38,000 uW-sec/cm2 at the fail-safe point, as determined by the
inactivation of spores whose sensitivity has been determined in Item 5.2,
5.4 MICROBIAL REDUCTION PERFORMANCE: Microbial reduction performance for a Class B
system shall provide a minimum UV dose equivalent to 16,000 uW-sec/cm2 at 70 percent of the
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Appendix P., Regufations and Standards for Drinking Water Disinfection Using Ultraviolet Light
D.6 ANSI/NSF STANDARD 55-1991 (CONTINUED)
UV lamps'normal output or at the fail-s^fe point as determined by the inactivation of yeast whose
sensitivity has been determined in Item 5.2.- .'
SECTION 6. mSTRUCTION AND INFORMATION
6.0 OPERATION; MAINTENANCE, AND INSTALLATION INSTRUCTIONS: instructions for
installation, operation, maintenance, and initiation of service shall be provided with each system or
component. Installation instructions shall note the need for compliance with state and local model
laws and regulations. Supply sources for expendable components and supplies for the system or
component shall be clearly stated. A manual shall be provided which includes drawings and parts
lists for easy identification and ordering of replacement parts and shall include:
Model number and class designation
• Statement of applications: ~
This Class A system conforms to NSF Standard 55 for the disinfection of microbiologicallv
contaminated water that meets all other public health standards. The system is not intended
for the treatment of water that has an obvious contamination source, such as raw sewage; nor
is the system intended to convert wastewater to microbiologically safe drinking water 'The
system is .intended to be installed on visually clear water (not colored, cloudy or turbid
water). If this system is used for the treatment of surface, waters a prefilter found to be in"
compliance for cyst reduction under ANSI/NSF Standard 53: Drinking Water treatment
Units - Health Effects shall be installed upstream of the system.
NSF Standard 55 defines wastewater to include human and/or animal body waste 'toilet
paper, and any other material intended to be deposited in a receptacle designed to receive
unne and/or feces (blackwaste); and other waste materials deposited in plumbing fixtures
(greywaste).
OR :
This Class B system or component conforms to NSF Standard 55, and contains ultraviolet
) lamps that require replacement at intervals in accordance with the manufacturer's instructions
The system is designed for the supplemental bactericidal treatment of either treated and
disinfected public drinking water or other drinking water which has been tested and deemed
acceptable for human consumption by the state or local health agency having jurisdiction
The system is designed to reduce normally occurring non-pathogenic or nuisance
microorganisms only. Class B Systems are not intended for treatment of contaminated water.
• • Model number of UV lamp
• Use limitations
• Cleaning instructions
• Maximum and minimum flow rates
; • Recommended frequency for the replacement of UV lamps (Class B systems)
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D.6 ANSI/NSF STANDARD 55-1991 (CONTINUED)
6.1 DATA PLATE: A data plate or plates shall be clearly and permanently affixed to the system or
component in a readily accessible location and shall contain:
• Manufacturer's name and address
• Model number and class designation
• Model number of UV lamps
• Maximum operating feed water temperature in degrees C (degrees F)
• Applicable warning signs ;.
• Use limitations statement: "See instruction manual for use conditions."
• Maximum rated operating pressure in kPa (psi)
• Maximum flow rate in L/min (gpm or gpd)
• Operational volts, amperage, and Hertz of system
• Recommended frequency for the replacement of UV lamps (Class B systems)
• The following applicable statement:
CLASS A SYSTEM: Conforms to NSF Standard 55 for the disinfection of microbiologically
contaminated waster that meets all other public health standards. The system is not intended
for the treatment of water that has an obvious contamination source, such as raw sewage; nor
is the system intended to convert wastewater to microbiologically safe drinking water.
,OR
CLASS B SYSTEM: The system or component conforms to NSF Standard 55, and contains
ultraviolet lamp(s) that require replacement at intervals in accordance with the manufacturer's
instructions. The system is intended for the supplemental bactericidal treatment of either
treated and disinfected public drinking water or other drinking water that has been tested and
deemed acceptable for human consumption by the state or local health agency having
jurisdiction. The system is designed to reduce normally occurring non-pathogenic of
nuisance microorganisms only. Class B Systems 'are not intended for the disinfection of
contaminated water.
6.2 SALES FACTS SHEET: A sales fact sheet shall be available to the purchasers and shall include
the following information:
• Model number and class designation
• Statement of applications:
This Class A system conforms to NSF Standard 55 for the disinfection of microbiologically
contaminated waster that meets all other public health standards. The system is not intended
for the treatment of water that has an obvious contamination Source, such as raw sewage; nor
is the system intended to convert wastewater to microbiologically safe drinking water. The
system is intended to be installed on visually clear water (not colored, cloudy, or turbid
water). If this system is used for the treatment of surface waters a prefilter found to be in
compliance for cyst reduction under ANSI/NSF Standard-53: Drinking Water Treatment Units
- Health Effects shall be installed upstream of the system.
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Appendix D. Regulations and Standards for Drinking Water Disinfection Using Ultraviolet Light
D.6 ANSI/NSF STANDARD 55-1991 (CONTINUED)
NSF Standard 55 defines wastewater to Delude human and/or animal body waste, toilet
paper, and any other material intended to be deposited in a receptacle designed to receive
urine and/or feces (blackwaste); and other waste materials deposited in plumbing fixtures
, (greywaste).
OR
This Class B system or component conforms to NSF Standard 55, and contains ultraviolet
lamps that require replacement at intervals in accordance with the manufacturer's instructions.
The system is designed for the supplemental bactericidal treatment of either treated and
disinfected public drinking water or other drinking water which has been tested and deemed
acceptable for human consumption by the state or local health agency having jurisdiction.
The system is designed to reduce normally occurring non-pathogenic or nuisance
microorganisms only. Class B Systems are not intended for treatment of contaminated water.
• Manufacturer's name and address
• Rated service flow rate in L/min (gpm or gpd) v
• Pressure drop of unit in kPa (psig) at rated flow.
• „ Electrical characteristics, volts, amperage, and Hertz. Recommended service life of UV
lamps
• Maximum and minimum operating pressure in kPa (psig).
'» • Maximum operating feed water temperature in degrees C (degrees F).
• Use limitations
Recommended frequency for the replacement of UV lamps (Class B systems)
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Appendix D. Regulations and Standards for Drinking Water Disinfection Using Ultraviolet Light
D.6 ANSVNSF STANDARD 55-1991 (CONTINUED)
'The preface and pages 1 through 9 of ANSI/NSF Standard 55-1991 "Ultraviolet
Microbiological Water Treatment Systems" are reprinted with the permission of NSF
International. To assure you have the complete and current standard, please contact:
NSF International
3475 Plymouth Road •
P.O. Box 130140
Ann Arbor, MI 48113-0140
1-800-NSF-MARK
World Wide Web Address: http://www.nsf.org
&-Mail Address: info@nsf.org
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