ur.rnnu otET ASS0GIAIIoX ruffiffiffi lssil 152&|0'217 Volume2/1{o.3 6 5 4 3 2 1 0 30 40 50 60 7A 80 90 100 UV Dose (mW-sec/cm2) Effects of differing water qualities on UV performanco (sniceretd.,2000) C o (g o (U c o) o Poliovirus MS-2BacterioPhage Virus O Ground Water 1 r Ground Water 2 a Ground Water3 v Ground Water4 a Ground Water 5 a Ground Water6 a Ground Water 7 E Ground Water8 a Surface Water 1 'l Surface Water2 o Surface Water3 - Lab Grade water See Artide by Malle/, PP. 8-12
Transcript
ur.rnnu otET ASS0GIAIIoXruf f i f f i f f ilssil 152&|0'217 Volume2/1{o.3
6
5
4
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030 40 50 60 7A 80 90 100
UV Dose (mW-sec/cm2)
Effects of differing water qualities on UV performanco (sniceretd.,2000)
Co(g
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Poliovirus MS-2 BacterioPhage Virus
O Ground Water 1r Ground Water 2a Ground Water 3v Ground Water 4a Ground Water 5a Ground Water 6a Ground Water 7E Ground Water 8a Surface Water 1'l Surface Water 2o Surface Water 3
- Lab Grade water
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In semiconductor, bio-pharmaceutical, and
beverage plants worldwide, Aquafine tIV systems
play a key role in disinfection, ozone destruction,
ContentsAWWA's WQTC Will Emphasize UV This November 26-27BC Hydro UV DisinfectionBriefAvailable . . . . . . 7The Bookworm's Corner 4r-42DoseRequirementsforUV Disinfection . . . . . 28-34Effect of Upstream Processes on W Disinfection (Book) 4l-42Engineering UV Disinfection Systems for Drinking Water 8-12History of UV Disinfection in the Last 20 Years 5-'7IUVAMembershipSurveyandResults . . . . . . 18-19Knowledge Gaps: For Reliable UV Application . . . . 20-22Meetings Calendar 40-41MessagefromtheIUVAPresident . . . . . .4New IUVA Corporate Sponsors
- Welcome !! . . . . . . . . 24
Thermodynamics of Hell Questioned on University ExamUV Abstract
has been developed. The cell is filled with a mixture ofhydrogen and deuterium as active gases and argon gs a buffetgas. The cell is pumped with the fourth harmonic of aNd:YAG laser. The partial pressures of the gases are chosento achieve even energy for the first Stokes of hydrogen(299nm) and deuterium (289nm), which are used as DIALwavelengths. The ON and OFF beams, produced in this way,have identical spatial intensity distribution, identical temporalpower profiles and the ability to probe the same air volume atthe same time, which contributes to the decrease of systematicerrors. Special care is taken to diminish the negative influenceof the crosstalk befween channels in the receiving part and thespatial nonuniformity of the receiving photosensors. Lidarmeasure-ments of tropospheric ozone concentration withvertical resolu-tion ranging from 15 to 150 m and distancesfrom 200 to 1200 m are performed. The results are comparedwith ground-based punctual measurements and with DIALmeasurements from a system with two Raman cells.
22aJ
UV Curing - A Major Sector for UV ApplicattonsUV Curing as We Enter the New MillenniumUV Disinfection for Drinkine WaterWater Supply, 5'h Edition
uring the past 20 years, the implementation of UVdisinfection systems has been impacted by numerousregulatory changes, many of which were aimed at
alternative disinfection systems that benefitted theimplementation of W. These regulatory changes -- as well asprocess changes and qystem design changes -- have made itpossible to apply W disinfection over a wide range ofconditions and have resulted in rapid growth in the use of UVsystems in the United States. A rwiew of some of the keyhistorical tnnsitions in the UV industry follows
Regulatory Changes
During the early part of the 1980s, UV disinfection gainedpopularity as a result of funding of Innovative and Alternative(UA) technologies by the United States EnvironmentalProtection Agency (EPA). VA funding allowed newtechnologies to be implemented at wastewater treatmentfacilities with the option for complete replacement if thetechnology failed to achieve compliance with NPDES permitrequirements. Despite a number of failures, UV technologrgalned limited State regulatory acceptance during the 1980s. Insome cases, these failures resulted in many State agenciesdelaying acceptance of UV disinfection until the mid- to late1990s
In California, testing for compliance with Title22 rcquirementswas conducted during the early 1990s. Results of this testing(1,2) indicated that UV disinfection systems can achieve thecoliform limits established by Title 22
Other regulatory requirements that have impacted the growth ofUV systems in the U.S. include Aquatic Toxicity, Uniform FireCode, and OSHA risk management plans (RN{P). Theincorporation of aquatic toxicity limits into NPDES permitsmade it necessary for many communities to dechlorinate thewastewater effluent before it was discharged into the receiving
stream. In 1988 (3) the Uniform Fire Code beg;an to impactfacilities that were undergoing expansion by requiring theinstallation of chlorine scrubbers as protection against theaccidental release of chlorine gas. In I 999, facilities using morethan 1,000 pounds of chlorine were required by OSHA (a) todevelop and implement a RMP for use in the went of theaccidental release of cNorine. Both the Uniform Fire Code andthe RMP requirements have increased the interest in the use ofW for disinfecting wastewater.
Process Changes
Several authors have suggested criteria for the design ofWsystems disinfecting wastewater. The National Water ResearchInstitute (NWRI) has zuggested guidelines for the use of UV forwater reclamation facilities (5). These guidelines have beenadopted by a number of States as standards for the design ofWsystems for reclamation facilities.
Dynamic modeling has become a key parameter in the design ofUV disinfection systems (6,7). The results ofthe modeling runsare leading to improvements in the hydraulic design of the UVreactors. Dose determination also has been refined during thelast 20 years from the Multiple Point Source SunmationApproximation to a model that uses an infinite number of pointsources for the determination of UV dose (8).
On-line sensor measurements of both transmissivity andintensity have presented a challenge rather than providedreliable results. In one study (8), the results from six sensorswere found to be inaccurate. An additional survey completed aspart ofthe same study found that 80 percent ofthe senson usedin operating systems in the northeastern part of the U.S. hadfailed..
Testing of UV disinfection systems using a bioassay approachwas suggested in 1983 (9) Over the past 20 years, testing hasbecome more an art than a science, resulting in disagreementamong professionals regarding the correct methodology fordetermining correct test results (10).
a-
, System Design
Several changes have occurred since the 1980 vintage UVsystems were installed at wastewater treaunent facilities. Mostnotable hasbeen the preference for open channel systems. MostUV systems installed in 1980 were enclosed reactors that didnot allow easy access for cleaning the quartz sleeves. In somecases, enclosed space entry p€rmits were required beforetreatrnent plant operators were allowed access for cleaning.Cleaning generally consisted of manually wiping the quartzsleeves. These systems were replaced during the mid-1980swith open channel designs in either the horizontal or verticalalignment. In 1980, almost all UV systems being used todisinfect wastewater used low-pressure mercury vapor larnps.This type of lamp still is used in smaller UV systems.
In the mid 1990s, UV disinfection systems with mediumpressure lamps were introduced into the wastewater market.Medium-pressure systems produce a high-intensity, broad bandspectrum of light, reducing the number of lamps needed fordisinfection over the traditional low-pressure systems. Sincethese systems offer self+leaning as a standard feature they havebecome popular with wastewater treatment operations staffs.
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By the late 1990s, two additional types of LIV systems appearedonthewastewater market: the first, low-pressure, high intensityUV systems (which basically used a higher wattage low-pressurelamp) and the secon4 pulsed LIV. The low-preszure, highintensity systems typically require a lower number oftraditionallow pressure lamps and greater number of lamps whencompared to medium-pressure UV systems (11). These lampsare offered in either a vertical or horizontal alignment. Thelow-pressure, high intensity systems also are equipped with self-cleaning mechanisms. Testing has indicated that these systemsmay provide some energy savings over the traditional lowpressure and medium pressure systems (12). PulsedUVsystems(13) convert an alternating current to direct current and storethe electrical charge in a capacitor. Tlrc enerry then is releasedthrough a high-speed switch in plasma to generate intenseradiation and LJV light. The pulsed radiation is approximately20,000 times more intense than sunlight at sea level..
,dpplications
LIV disinfection has enjoyed a long history of use in thewastewater industry in the U. S. UV systems have been designedto treat storm water (14), combined sewer overflows (15,16),wastewater effluent for reuse and, most recently, potable watersystems (176,18). One of the most promising advancements isthe use of UV for disinfecting potable water. A number ofresearchers have found that UV can inactivate Giardia Lamb liaand Cryptosporidium, known parasites at doses of 15 to 2MJ/cm'?(19,20).
Growth of IndustrY
In 1984, there were only a handfirl of W systems being used inthe U.S. to disinfectwastewater. Veryfew of these systems hada design capacity greater than 5 mgd. At the end of 1999, thetotal number of installed UV systems treating wastewaterexceeded 500. The average design capacity of these systemsexceeded 20 mgd. Two of the largest systems, both exceeding100 mgd, are located in Canada .(22,23)
Conclusion
V disinfection systems have progressed a long way since1980. Both equipment and process design approacheshave undergone radical changes. These changes have
resulted in a multiplicity of UV lamps and system configura-tions being implemented at treatment facilities. Regulatoryimpacts to other disinfection methods have brought about aresurgenc€ in the acceptance of UVby the wastewater industry.This resurgene will enable tIV disinfection to continue to gainpopularity at a very rapid rate over the next several years.
6
- more -
References
l. Montgomery Watson, A Comparative Study of W andChlori ne Di si nfe ction oflltastewater Re clamat ion. P.epftof Elsirpre Valley Municipal Water District and NationalWater Research Institute, 1994.
3. National Fire Protection Association (NFPA) Life SafetyCode l0l, 1988.
4. 29CFR-1910.119, 1993.5. l{Wzu, W Disinfection Guidelines for l{astewater
Reclamation in Califtrnia. A report prepared by theNational Water Research Institute for the State ofCalifornia Departrnent of Health Services, 1993.
6. Blatchley, E.R. III, DoQuang 2., Savoye P., Janex, M.,lainC, J., Chiu, K., Shapiro, A.J., and Hull C.J.,Optimization of Process Performance in UltravioletDisinfection Systems, Disinfection 98 sponsoredby WaterEnvironment Federation, April 1998.
7. Chui, K., Lyn, D.A. and Blatchley, E.R., III,Measurements and Modeling of Micro-scale Hydro-dynamic Behavior in W Disinfection Systems:Application for Improvement of Process Imprwements,Disinfection 98 sponsored by Water EnvironmentFederation, April 1998.
8. Malley, 1., W Disinfection's Emerging Role in DrinkinglI/ater Treatment - Theories and Practical Questions,U.S.EPA Workshop on UV Disinfection of Drinking Water,Arlington, VA, April 1999.Qualls, R.G.. and Johnson 1.D., Bioassay and DoseMeasurements in Ullroviolet Disinfecfion, Applied andEnvironmental Microbiolory, 45, 87 2, 1982.Personal Communication, Sid Elner, Ultratech.Hunter, G., O'Brierq rff., Hulsey, R., Carns, K., Ehrhard,k, Emerging Disinfection Technologies, Water Environ-ment & Technologr, Volume 10, No 6, June 1998.Jack, 2., Ultraviolet Disinfection of Tertiary FilterEfrluent Using Low-Pre ssure Hi gh-In tensi ty Lamps, W aterand Energy Conference sponsored by Waterworld, August1999.l,aFrertz,R., High Intensity Pulsed Wfor Drinking I'I/aterTreatment, Proceedings AWWA Water Quality Tech-nolog5r Conference, Denver, CO, Novembet 1997.Personal Communication, Trojan Technologies. Inc.Averill, D., Cairns, W., Solid/Liquid Separation and WDisinfection in CSO Treatment Systens, Disinfection 98,Water Environment Federation Specialty Conference,April, 1998.Wright, H.B., and Cairns W.L., Ultraviolet Water Disin-fection, U.S. EPA Workshop on UV Disinfection ofDrinking Water, Arlington, VA, April 1999.
17. Malley, 1., Design Considerations for W DisinfectionSystems for Potable Water, Water auanty andTechnolory, San Diego, November 1999.
19. Finch, G.R and Belosevic,M. Inactivation of C. parvumand G. muris with Medium Pressure Radiation,U. S. EPAWorkshop on UV Disinfection of Drinking Water,Arlington, VA, April 1999.
20. U.S. EPA, Municipal Wastewater Disinfection, Repo( No.EP N6251 l-86/02 l, October 1986.
21. Kwaq d Archer, J, Soroushian, F, Mohammed, dTchobanoglous, G, Factors for the klection of a High-Intensity W Disinfection System For A Inrge-ScaleApplication, Disinfecting Wastewater For Discharge &Reilse, Water Environment FederatiorU lvlarch 1996.
22. Whalley, M.J., Fries, M.K, The Bonn$rook WDisinfection Facility, Planning, Design & Operation ofEfiluent Disinfection Systems, Water EnvironmentFederation Specialty Conference, May 1993.
23. Averill, D., Cairns, W., Solid/Liquid Separation and WDisinfection in CSO Treatment Systens, Disinfection 98,Water Environment Federation Specialty Conference,April, 1998.
This extended abstract appears in W 2000 - A TechnicalSymposium,published by and available from the National WaterResearch Institute, 10500 Ellis Avenue, P.O. Box 20865,Fountain Valley, C A 927 284865; Fax: 7 14-37 8-337 5; email:[email protected]. Price = $15.00 (U.S.).
B C. hy :ro' |UV,Dii inIiCfi.oin:,:Biw
C Hydro's Water and Wastewater Centre has justreleased a6-page Electrotechnologr Brief - UltravioletDisinfection. The publication contains sections dealing
with W Benefits, Description of UV lamps and systems,System Design, Current Status, Applications (municipalwastewater, drinking water, and industrial), Energy Use andCosts, Advantages and Disadvantages, and a partial listing ofUV equipment suppliers.
Copies can be obtained at no cost by contacting BC HydroWater and Wastewater Centre, 6911 Southpoint Drive - El6,Burnaby, B.C., V3N 4X8, CANADA, Tel: l-877431-7648;Fax: 604-528 -l 5 52; E-mail: [email protected]. Or contactKrystyna Chrobok, C€ntre Administrator, Phone: (604)528-1517; Knsh'na.ChroboktDnCHvdro.bc.ca: Fax: (604)528-t552.
9.
10.10.
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11.
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16.
ENGINE ERING"' A F W DTS INFE CTI ON.S YSTEMS .FOR"DRINKING....ffiIIE R
Associate Professor ofEnvironmental Engineering at the University ofNewHampshire (USA)
EXECUTTVE SUMMARY
;lonventional UV disinfection is a physical disinfection
I pr&ess that uses commercially available lamps, which\-/emit UV light in the wavelengths of 2@ nm to 300 nm.
These so called germicidal wavelengths cause damage to DNAand RNA by dimerizing bases such as thymine and uracil. Thedamaged nucleic acids prevent replication thus rendering thepotential pathogen sterile and unable to cause infection.
UV disinfection has had widespread use in the wastewatertreatment field throughout North America. However, it haslong been believed thaf UV was incapable of inactivatingprotozoan cysts or oocysts such as Giardia lamblia cysts andCryptosporidium parvum ocr'ysts at cost€ffective dosages (Riceand Hoff, 1981; Campbell, 1995). More recently however, itwas discovered that the analytical methods commonly used todetect cyst and oocyst viability after UV dosage experiments,chemical excystation and vital stains, were incapable ofpredicting the effectiveness of UV disinfection since UV doesnot kill or inactivate the target pathogen rather it renders itincapable of infecting a cell.
Recent research by Clancy et al. (1998) and Bukhari et aI.(1999) using mouse infectivity as the measure of viabilityshowed tlnt W is higNy effective at inactivating Crypto-sporidium parvnz oocysts. This work was confirmed by threeother research groups using animal infectivity or cell culturetechniques (Finch and Belosevic, 1999; Mofidi et al., 1999;Linden and Sobsey, 1999). Similar work wingGiardia cystsalso has shown that UV can effectively inactivate these cysts(Finch and Belosevic, 1999; and Linden and Sobsey, 1999). Asa result the U.S. EPA nray propoee that UV can be used as a bestavailable technology for treating drinking water supplies.
A draft cost document by Malcolm Pirnie, Inc. for U.S. EPAevaluated a scenario in which a UV dose of 40 mJ/cm2 could begranted inactivation credit of 2-logsfor Giardia cysts and 2-logsfor Cryptosporidium. If UV is granted these levels of disinfec-tion credit by the regulatory community its widespread use indrinking water disinfection in North America is likely since itcan be as low as one fifth the cost ofozone or one tenth the costof membrane filtration (MF size) and it would require a verysmall fraction (about one thousandth) of the space that these
other technologies rcquire. UV system costs (2000 U.S. dollars)were found to range from $0.05 to $0.08 per gallon of installedcapacity for capital costs and from $0.005 to $0.03 per thousandgallons treated for annual operation and maintenance costs.
Key factors which affect UV design include in the order ofimportance: number and rype of UV lamps used; UV reactorhydraulics and hydrodynamics (turndown ratios must becarefrrlly considered); target organism(s) and level ofinactiva-tion required; location of UV in the treatment train degree ofrequired redundancy; water quality characteristics such as: Wattenuation by the water, tuftidity/pafticles, minimum tempera-ture for lamp operation and degree of lamp fouling frominorganic constituents particularly iron and hardness; numberand type of UV sensors; UV reactor gpes, configurations andmaterials; and system instrumentation and controls.
Key issues in W operation and maintenance include the needfor frequent calibration and/or replacement of W sensor(s).Many UV sensors tested were foundto have operatingproblems,easily lose calibration orbecome completely insensitive rapidly.The importance of proper UV lamp and sleeve cleaning andperiodic replacement was found in all studies. The tlpe of UVsystem cleaning selected will directly alfect UV systemheadloss, UV system operation and maintenance costs and Wsystem reliability. Developing detailed day-today performancemonitoring protocols including continuous monitoring of UVsystem equipment readings (sensors, flow, lamp out indicators,lamp hours, electronicVballast temperatures and finished watermicrobiological monitoring plans is critical to gainingregulatory acceptance of W technologies.
KEY WORDS
Ultraviolet disinfection; W ; G i ardi o cysts; Cryptospori diumoocysts; drinking water treatment; surface water treatment;operation and maintenance
INTRODUCTION
Conventional ultraviolet (UV) disinfection is a physical disin-fection process that uses commercially available lamps, whichemit W light in the wavelengths of 200 nm to 300 nm. These
so called germicidal wavelengths cause damage to DNA andRNA by dimerizing bases such as thymine and uracil. Thedamaged nucleic acids prwent replication thus rendering thepotential pathogen sterile and unable to cause infection. UVdisinfection has had widespread us in the wastewater treatrnentfield throughout North America. However, it has long beenbeliwed that UV was incapable at inactivating protozoan cystsor oocysts such as Giardia lamblia cysts and Cryptosporidiumparwm oocysts at cost+ffective dosages (Rice and Hotr, l98l;Campbell, 1995). Recent findings in North America thatconventional, continuous wave ultraviolet CJV) disinfection caninactivate Cryptosporidium parvum as well as many otherhuman pathogens of concern in drinking water at cost+ffectivedosages has spurred tremendous excitement and researchthroughout the U.S. and Canada.
Pending regulations focus on simultaneously protecting thepublic health from microbial risks such as those from Giardia,Cryptosporidizm and viruses and the potential chemical healthrisks from disinfectionby-products has posed a difficult problemfor the drinking water industry. In the U.S. negotiations areunderway between all stakeholders to adopt the Stage 2Microbial and Disinfection By-Product regulations. Concernsexist that if tighter Cryptosporidium inactivation requirementsare imposed then drinking water Eystems will need to shift tomore costly technologies such as long ozonation CxT times ormembrane filtration. In addition, if DBP regulations forbromate or individual brominated organics are imposed, thenozone rnay not be an optimal solution. The potential tlnt UVdisinfection processes could be used to inactivate microbes ofconcern while reducing or as a minimum not adding to DBPformation has caused many drinking water organizations tofocus on bench, pilot and full-scale research for applying UV tosurface drinking water disinfection requirements.
UV DISINFECTION EFFECTTVENESS
Drinking water disinfection requirements have been driven inrecent years by concerns about the risks from Giardia lamblia,Cryptosporidium parvum and human enteric viruses. In theU.S., the 1986 Surface Water Treatment Rule (SWTR)mandated a 3Jog removaVinactivation of Giardia and a 4-logremovaVinactivation of viruses. More recently, the InterimEnhanced SWTR essentially added a 2-log removal ofCryptospor i diarn through an optimized filtration requirement.
Figure I shows the effectiveness of UV for inactivation ofCryptosporidium parvum oocysts and Gi ardia cysts. These datareflect the recent understanding that UV effectiveness forinactivating protozoan systs or oocysts must be waluated usinganimal infectivity or cell tissue culture methods @ukhari et al.,1999). The Cryptosporidium data shows that a W dose of l0mJ/cm2 inactivated up to 4-logs of oocysts in most cases. Finchand Belosevic, 1999 observed a tailing effect in their results, but
concluded ilut a W dose of l0 mJ/cm2 would reliably achievea2-loginactivation. By contrasfi older literature suggested thatdoses of hundreds or thousands of mJ/cm2 would be required toinactivate protozoan cysts (Campbell, 1995). It is alsointeresting to note that the Cryptosporidium data based onanimal infectivity generated by Bukhari et al., 1999 and byFinch and Belosevic, 1999 conesponds well with theCryptosporidium databa*A on cell tissue culture generated byLinden and Sobsey et al., 1999 and Mofidi et al., 1999.
rF ^ Lin. R.pr!3anb D.ta Rcporbd.3 >/t.0 log Inactivation o
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UV Dose (mJ/cm2)
Figure l. W Dose-Response Data for Cryptospori dium parvumoocysts in filtered surface water samples. Data reported by:Bukhari et al., 1999; Finch and Belosevic et al., 1999; Lindenand Sobsey et al., 1999 and Mofidi et d., 1999.
The Giardia data suggests that greater than 2Jogs inactivationof rysts can be achieved at a dose of l0 mJ/cm2. Finch andBelosevic, 1999 working with Giardia muris cysts noted atailing effect which was not observed by Sobsey and Linden,1999 who were using Giardia lamblia cysts. In either case, thedata sets both demonstrate that a UV dose of l0 mJ/cm2 or lesswill effectively inactivate at least 2-logs of Giardia qsts.
The effectiveness of UV for inactivating virus is well docu-mented but it is important to note that there is a wide variety ofvirus strains that may be of concern in drinking water and theirrelative susceptibility to UV can vary widely. Table I srilnma-rizes the effects of UV on the major virus strains currently ofinterest to the drinking water industry. These data are compiledfrom work done by the authors on a variety of water qualitiesand data available in the current literature. These data suggestthat Adenovinrs, a double stranded (DS) DNA virus, may be themost resistant to UV inactivation. This finding would beconsistent with earlier reports that Adenovirus has the capabilityto repair enzymatically damage to the DNA. Aside fromAdenovirus data, which is currently undergoing further studyand verification, it has been generally accepted that thesurrogate MS-2 phage is a conservative indicator of humanenteric virus inactivation by UV. If future work supports the
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Table l. UV for virus
VirusUV Dose (mJ/cm2) for Inactivation of:
2-los, 3-los 4-log Reference
Adenovirus 40 59 90 t2l Mene & Gefta. 1996
Adenovirus 4l 50 80 Meng & Gefta, 1996
Coxsackievirus 85 t4 2l Battieelli et al.. 1993
Heoatitis A HM-175 4-5 I 1-13 r6-22 Snicer et al.. 2000
Poliovirus Type I 8- l I l5-19 23-29 Snicer et al.. 2000
Reovirus Troe I 36 Harris et al.. 1987
Rotavirus WA 25-32 3546 50-70 snicer et al.. 2000
Rotavirus SA-11 l9 25 36 Wilson et al.. 1992
Surroeate: MS-2 25-39 3863 50-93 Snicer et al.. 2ooo
a-
Adenovirus data then the UV dose for 2-log credit would likelybe increased to about 60 mJ/cm'?.
EFFECTS OF WATER QUALITY MATRD(ON UV PERFORMANCE
Water quality conditions can affect all disinfection process€s.In the case of UV these effects are broken into direct andindirect effects. Direct effects include water quality constituentsthat attenuate or block W light and thus reduce the moles ofphotons of LIV light which reach the nucleic acid of targetpathogen. Indirect effects are water quality conditions whichcan affect lamp performance, foul UV lamp quartz sleeves andUV sensors or Grus€ organisms to surface-associate with parti-cles or aggregate (clump) thus making them more Uv-resistant.
Direct effects can be the result ofdissolved solutes such as iron,zulfites, natural organic matter (color or TOC) and qyntheticorganic compounds or the result of particles (tutbidity) andsuspended solids. It is well documented that UV disinfection isnot directly affected by pH and temperature. Snicer et al., 2000performed a study funded by the AWWARF in which 30groundwaters, 15 conventionally treated surface waters and 18synthetic waters were examined to determine which waterquality parameters directly affected the ability of UV toinactivate human enteric viruses and the surogate MS-2bacteriophage virus. Examples of these data are shown inFigure 2. The study showed that the parameters, whichsignificantly affected UV performance, were the dissolved ironconcentration. the UV absorbance measured at 254 nm(resulting from dissolved organic matter or iron) and the natureand type of particles. The efrects of dissolved solutes can beaccounted for by using the UV absorbance measurements toadjust the UV dose provided to the water. However, the degreeto which the UV dose can be increased to account forbackground absorbance is limited by practical qpace and costconsiderations.
inactivation.
Effects of particles (often measured by tutbidity) or suspendedsolids on UV performance are a function of their nature, typeand concentration as well as their interaction with the targetorganism. Experiments looking at the effects of three ffierentparticles on the ability of UV to inactivate MS-2 are shown inFigure 3. In these studies, samples of wastewater effluent(representing amorphous biological particles); settled conven-tional drinking water (representing amorphous inorganic (alum)floc); and conventional filter effluent which had breakthroughof discrete inorganic clay like particles were collected andspiked with MS-2. After 8 hours of mixing, these samples weresubjected to batch bench-scale collimated beam UV tests todetermine the dgse required to inactivate 2Jog of MS-2. Thesedata show that amorphous solids have a much more dramaticeffect on UV performance. Further, the particles passed throughconventional filtration did not significantly affect performanceuntil levels above 3 NTU were obtained. These data suggestthat the type and nature of particles will b€ important. Inaddition, these data suggest that placing UV post-filtrationrather than prior to filters is the optimal location in a conven-tional drinking water plant. Additional work is on-going todetermine how the nature of particles, which may contain highlevels of org;anic matter or algae, will affect W.
These g/pes of particles often are encountered in unfilteredwater supplies and in conventional filter plant effluents that aretreating highly colored waters or algae-laden reservoirs.
The most significant indirect effects of water quality parametenwere found to be sleeve and sensor fouling by dissolved iron,hardness or minerals and the effects of water temperature onlamp stability. Iron and minerals were found to significantlyincrease the rate of UV lamp sleeve fouling especially inmedium pressure UV lamp systems due to their increasedoperating temperatures. Water temperature was found tosignificantly affect low pressure and low pressure high outputUV lamps systems, likely because these lamp qystems tpicallyoperate at internal temperatures of 40 to 60'C.
l0
MS-2 Bacteriophage Virus
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1QTreating surface drinking water supplies in northern climateswith UVis one of the first applications in which waters enteringthe UV system may be at temp€ratures as low as 0.5"C. At theselower temperatures the UV lamps may have unstable output ortake longer to reach a stable operating lwel. Therefore,designers must account for these effects when selecting lamptypes, quafiz sleeve designs and operating procedures.Temperature effects on mediumpressure UV lamp systems werenot found likely due to the fact that MP W lamps operate atinternal temperatures of 400 to 600'C.
KEY FACTORS AFFECTING UVSYSTEM DESIGN
As shown in Figure 4, there are several factors which must beconsidered when designing UV systems. One critical factor isminimum UV dose which is affected by UV lamp design (type,number and orientation), IJV reactor hydraulics, and waterquality parameters. As prwiously discussed, the target
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UV Dose (mW-sec/cm2)Figure 2. Effects of differing water qualities on W performance (Snicer et al., 2000).
t : Settled /Settbd {..: Awn /+gffit:l""'
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Figure 3. Effects of particle (uftidity) type and concentrationon UV performance.
organism and the degree of inactivation desired also will
strongly inlluence the minimum design dose, since organismsvary in their resistance to UV. The importance of water quality
also has been demonstrated in this paper.
are critical to the day to day performance monitoring of W
systems and the sensors must be carefirlly maintained and
calibrated frequently to ensure reliability.
ACKNOWLEDGMENTS
Funding for the research presented was providedby AWWARF'
U.S. EPA and EPRI. Albert Ilges (AWWARF Project Officer)has provided tremendous help and insights during the past eightyears Colleagues Milie Belosevic, Gordon Finch (deceased),
Karl Lindeq Aaronlvfargolin and Alex Mofidi are thanked for
sharing their most recent UV inactivation data. Former UNHgraduate students Jen Wagler, Jefr Shaw, Jim Ropp' Greg
Snicer, Shannon Hogan, Annette Doucette, and Bryan Town-
send have contributed greatly to our current knowledge of UV'
REFERENCES
Battigelli, D.A., et al. (f993) The inactivation of Hepatitis A
viruiand other model viruses by W irradiation. I(at' Sci' &
Tech.27:34:339.gukttari, 2., et al. (1999) Medium Pressure W for Oocyst
Inactivation. Jour. AIIWA. 9 I :3 :86.Campbell, A.T. et al. (1995) Inactivation of Oocysts of Crypto-
tporidiu* Paruum by Ultraviolet lrradiation. Water Research'
29:ll:2583.Clancy, J.L. et al. (1998) W Light Inactivation of Cryptospor-
idium Oocysts. Jour. AWWA, 9O:9 :92.Finch. G. and Belosevic, M. (1999) Presentation to the U'S'
cysts by Ultraviolet lrradiation. Jour' Appl' and Envir'
Mi crobiolow. 42(3) 546.Sni."t, G.A. et al.. 2OCf.' Evaluation of Ultraviolet Technologt
in Drinking Water Treatmenf. AWWARF Final Report'
AWWARF/AWWA Publ. Denver, CO.Wilson, B.R. et al. (1992) Coliphage MS-2 as a W ll/ater
Disinfection Efficacy Test Surrogate for Bacterial and Viral
Pathogens. Proc. 1992 AWWA WQTC, Toronto, Ontario,
Canada. AWWA Fubl. Denver, CO' USA.
Fdor lrdox:A Mr*nln W Dose - f (hnp ad r€6r frydalic e*tn)B. Tdgd qgankiln a.d e€i€d KiI'(Dooo-Rosponsa Varies)C. Vfator Oratlty ltihfix - ( Fe, lih' pl-l' T6' TtttUd'tty/Padides)O. W Sgrsors - CRITIOAL TO PERFORIVIAI{CE }ilf,NTffil'GE. WLarpTpe(tP,[P,tFf i3,Fhsh) t 'F. Sleoro ilat;d (OLsrtz, T€fror\ C@t€dOuarts) ild Cl€r*lgG. qfiie.n El€ctrorics (Balla$s), lrrtnnnentalion ard Conlrob .X. nea&r ttperuaterid (charnC \6. pressure vessel ' SS w' Fr'Q
Figure 4. UV reactor schematic and key design factors'
UV sensors are critical to the day to day operation andperformance verification of UV systems. Concerns over UV
sensor reliability remains the largest obstacle to UV acceptance
by regulatory officials and water utility operators. The author
has found that the precision, a@uracy and stability of UV
sensors varies widely. An initial survey of UV sensors in place
at over 100 wastewater UV disinfetion facilities found that
80p/o ofthem were unreliable and hence not used. In wastewater
W systems, day to day performance can be verified by measur-
ing effluent coliform organisms; however, in drinking water
treatment there is no acceptable surrogate that is always present
in the water and UV sensors will be critical. Increased
emphasis by W manufacturers on developing reliable s€nsors
has led to improvements. Recent AWWARF research per-
formedby the author has shown that reliable W sensors for low
pressue systems now are in use. However, effective sensors for
medium pressure W systems are less cornmon' All sensors
must be properly maintained and calibrated frequently (at least
quarterly) to produce meaningful results.
CONCLUSIONS
UV disinfection systems have been found to effectively
inactivate Giardia qsts, Cryptosporidium oocysts and human
enteric viruses at cost€ffective dosages. This result combined
with earlier findings ttnt UV does not increase concentrations
of disinfection by-products or contribute to regrowth problems
in distribution systems makes it an attractive technologr for
meeting emerging water quality regulations in the U'S' UV
system design and performance is a function of lamp design and
reactor hydraulics as well as key water quality parameters such
as UV absorbing constituents, particles and solids, and constitu-
ents that can foul UV quartz sleeves and sensors. UV sensors
t2
TIV DISINFECTION FOR DRINKING WATER
J. Cosman and H. Wright
Trojan Technologies, 3020 Gore Roa{ l,ondoiu onulrio, CANADA NSV 4fi::,,:,r"r''i-rilizl:'rtn; il'zr rl ; F; ;i;l;z-mro ; e-maii; [email protected]
Introduction
The ongoing changes in the Surface Water Treatment Rule andthe Disinfectant/Disinfection By-Froducts Rule have resulted ina reevaluation of disinfectants and disinfection strategies.Ultraviolet (tJD disinfection is a versatile, safe and cost-effective technology that effectively inactivates pathogenicvirus€s, bacteria, and protozoa, all without the production ofharmful disinfection byproducts. This paper evaluates lfV, asa compliance technology for drinking water disinfection, usingthe following criteria:
l. Effective against a wide range of pathogens2. Minimal sensitivity to water quality3. Minimal by-product formation4. Minimal space requirernents5. Low capital and O&M costs6. Safe to operate7. Compatible with Multi+arrier Disinfection Strategies
Effective Against a Range of Pathogens
Microbial inactivation is directly dependent on absorption ofW energr by microbial nucleic acids (DNA and RNA). Thedegree ofinactivation and loss ofinfectivity is related to ttrc Wdose absorbed. UV dose may be defined using IT values, theproduct of delivered UV intensity and the exposure time. ITvalues are analogous to the CT values used to define chemicaldisinfectant dose. Dose-response data reported in the literature(Table l) illustrate the effectiveness of UV against a widevariety of pathogenic viruses, bacteria, and protozoa. Animaland tissue assay methods recently have demonstrated that lowdoses of UV inactivate Giardia cysts @inc[ 1999; Linden andSobsey, 2000) and Cryptosporidium ooc'ysts (Mofidi et al., I 999;Bukhari et al., 1999; Shin et al., 2000). These low doses are afraction of the design dose currently specified in most UV disin-fection applications, indicating tlrat UV is extremely effectiveagainst these waterborne protozoa. The UV dose used in aspecific tIV application will depend on theregulatory require-ments for pathogen inactivation, the target pathogens, thenumber of microbes pres€nt, and the association of thosemicrobes with particles.
In potable water, the concentration of pathogens and indicatormicrobes often are below the detection limits of routine assaymethods. Accordingly, drinking water regulations, srch as theSurface Water Treatment Rule, specif target doses (CT and ITvalues) as opposed to target microbe concentrations' Withchemical disinfection, Giardia cysts are considered moreresistant than baaeria and viruses (U.S. EPA, 1989).Consequently, Giardia inactivation determines the chemicaldesign dose. In the case of W, viruses are more resistant thanbacteria, Giardia, and, Cryptosporidium. Therefore, a UV-resistant virus stch as rotavirus would be a more suitable targetfor the selection of a UV dose for the primary disinfection ofpotable water.
Minimal Sensitivity to Water Quality
While the action of chemical disinfectants varies depending onthe temperature and pH of the water (U.S. EPA, 1989),pathogen inactiVation by W light is independent of thesefactors (Severin et al., 1983; Snicer et al., 1998)' UVdisinfection is equally effective at both high and low watertemperatures, whereas cold-water inactivation of a pathogensuch as Cryptosporidiumby ozone or other chemicals requiresadditional dose to attain a specified CT value (U.S. EPA, 1989;Finch et Ll.,1997\,.
Various chemical species in water may react with chemicaldisinfectants or absorb W light, thereby competing with thepathogens for the disinfectant. The complexity of chemicalmixtures in water makes it difficult to anticipate chemicaldisinfectant demand and its impact on pathogen disinfection'However, the UV absorbency of water is easily measured and itsimpact on tIV dose delivery readily predicted, thereby providingconfidence that a target pathogen reduction will be achieved.
Pathogens within particles are more resistant than dispersedpathogens to both chemical (Berman et al., 1988) and UVdisinfection (.oge et al., 1996). With treated potable water witha turbidity less than I NTU, UV disinfection may be assumed tofollow the disinfection of dispersed microbes measured inlaboratory cultures (Malley, I 999).
l4
Table IIV inactivation of1. associated with waterborne outbreaksPethogen Source Average IIV Dose mJ/cm2 Required to Inactivate by
Giardianaris cvsts J 1.2 4.7 NA NAVibrio cholerae 4 0.8 1.4 2.2 2.9Shisella dvsenteriae 4 0.5 1.2 2.0 3.0Esc heri ch i a co I i Ol 57 :H7 4 1.5 2.8 4.1 5.6Salmonella tvphi 4,5 t.8-2.7 4.14.8 5.54.4 7.1-8.2Shisella sonnei ) 3.2 4.9 6.5 8.2Salmone lla enteriti dis 6 ) 7 9 l0Legionella pneumophila 4 3.1 ) 6.9 9.4Hepatitis A virus 4.7.8 4.1-5.5 8.2-t4 12-22 16-30Poliovirus Tvoe I 4,5,9. l0 44 8.7-14 t4-23 2t-34Coxsackie 85 virus 7 6.9 t4 22 30Rotavirus SAll 4,5,7 7.1-9.1 l5-19 23-26 3r-36NA - Data Not Available
References. (l) Wright (2000), (2) Linden and Sobsey (2000), (3) Finch (1999), (4) l{ilson et al. (1992), (5) Chang etal. (1985), (6) Tosa and Hirata (1998), (7) Battigelli et al. (1993), (8) I{iedenmann et al. (i,993), (9) Harris et al.(198D, (10) Meng and Gerba (1996).
Chemical species such as iron and calcium in water may formfouling deposits on the quartz sleeves that protect the UV lamps.Fouling caus€s a reduction in the W intensity delivered to thewater. UV sensors may be used to monitor the impact offoulingand trigger cleaning cycles. For small UV systems with lowfouling rates, periodic manual cleaning may be the most cost-effective approach. For larger systems and systems with rapidfouling, automatic wiping mechanisms that combine bothphysical and chemical cleaning may be more appropriate.
Minimal Byproduct Formation
Chemical ryecies in water can react with a disinfectant to formdisinfection byproducts @BPs) (Zavaleta et al., 1999). Chlo-rine DBPs include trihalomethanes, haloacetic acids, and highmolecular weight halogenated compounds. Many of these DBPsare carcinogenic, mutagenic, capable ofcausing birth defects,and therefore are regulated. Chlorine dioxide forms chlorateand chlorite DBPs. Ozone can convert many large organicpolymers to smaller organic molecules, thus forming nutrientsthat (unless biodegraded within the treatment plant) promotebiofilm growth in distribution lines (Akhlaq et al., 1990).Ozonation also converts bromide to bromate ion, a regulatedcompound.
UV disinfection in water, wastewater and reclaimed wastewaterhas been found to produce negligible concentrations ofDBPs(Wolfe, 1990), even at UV doses in excess of those needed fordisinfection (Oppenheimer, I 993 ). UV produces no measurablechange in the DBPs formed when chlorine or chloramine areused as a secondary disinfectant following UV (Malley et al.,1995). While some UV lamp technologies produce low UVwavelengths capable of converting nitrate to nitrite ion,appropriate lamp technology selection or the use of opticalfilters can minimize nitrite formation @ernhardt, l99l).
Minimal Space Required
With a small footprint, [fV systems are flexible and can bedesigned to retrofit into existing treatment facilities.
Acceptance and Cost-Effectiveness
With experience in over 1000 groundwater installations in theUSA and over 2000 ground and surface water installations inEurope (U.S. EPA, 1996), UV is an accepted and cost+ffectivedrinking water disinfection technology. UV disinfectioninstallations in Europe vary from 0.5 MGD to 79 MGD (Wolfe,1990; Kruithof,1992; Anon, 1997). Recent analysis (Malley,1999) suggests that the capital costs for UV range from $US
15
0.05 to $0.07 per US gallon of installed capacity. Operation andmaintenance costs range from $0.005 to $0.03 per thousandgallons produced. UV technologies using low-pressure mercurylamps are most cost€flective for small-scale applications, while
technologies using medium-pressure mercury lamps are most
cost+ffective for plant flows greater than 2 MGD.
Safety to OPerators and the Public
With proper training, UV technologr is simple and safe to
operate. Use of UV removes the need to u"nsport' store, andhandle dangerous disinfectant chemicals. When zuch practices
are regulatd costs associated with disinfection may increase by
30%. The Uniform Fire Code (IFCI, 1997) calls for accidentinsurance, ventilation ard storage requirements, and treatmentfacilities capable ofdealing with an accidental release ofchlo-rine gas or a caustic liquid spill. From the public's perspective,
UV offers increased protection from tlte broad spectrum ofpathogens. UV achieves disinfection without forming DBPs,
unpleasant taste and odors, and without the need to transport
chemicals through the community to the treatment plant.
Similar to thermometers, fluorescent lamps, and dental
amalgams, UV lamps contain mercury in elemental form.
Elemental mercury is poorly absorbed by the gastrointestinal
tract and is not considered a health ltAZArd (see
nrvw.emedicine.comlEMERG/topic8l3.htm), even in thequantities found in thermometers. Release of mercury due to
lamp breakage has not led to restricted use of UV disinfectionfor surface and ground water treatment in Europe (>2000
systems), and for groundwater treatment in the States of New
York (>264 systems) and Pennsylvania (>761 qystems) (U.S'
EPA, 1996). UV disinfection's continued acceptanc€ in thesejurisdictions is a result of good engineering design and
equipment performance validation by the manufacturer, and the
use of trained personnel by the end user.
Compatibility with Multipte Barrier Strategies
Because there is no ideal disinfectant, treatment proc€sses are
built around several unit operations, each ofwhich contributes
to the overall reduction in pathogens and hence a reduction in
the risk to public health. Negligible DBPs, minimal space
Camp Dresser &McKee Inc.
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Water/Wastewater UV Disinfection
Wastewater Reclamation
and operations services to the Analytical Techniques for UV Measutementswater and wastewater industry.
Our ultraviolet (UV) experts,
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t6
requirements, modular desigq low cost, and a broad spectrumof pathogen inactivation allow UV to be combined flexibly witha variety of other physical and chemical unit operations. UVdisinfection could be used either as a primary disinfectiontechnolory, as a codisinfectant with chlorine to achieveprimary disinfection, or as an add-on technolos/ to achieveCryptosporidium and, Giardia inactivation credits. Since UVdoes not provide a residual UVas a primary disinfectant couldbe followed by chloramine, a secondary disinfectant for biofilmcontrol in the distribution line. Sincc Giardia and Legionellaare resistant to chlorine (Sobsey, 1989; Ilaas et al., 1999) butsensitive to UV (see Table l), W used in tandem with chlorinemight prove a very efflective primary disinfection strates/,especially given the emergence (Friedman-Huftnan and Rose,1998) of other chlorine-resistant pathogens such as Myco-bacterium avium. L,ast, the ability of UV to readily inactivateCryptosporidium and, Giardia would allow UV to supplementchemical disinfectants, such as chlorine (Sobsey, 1989), whichare ineffective against Cryptosporidium. In the case of ozone,using W would reduce the amount of ozone required for coldwaters or when bromate ion is a con€rn.
Summary
The U.S. EPA (1990) ranked water treatment technologies aseither experimental, emerging, established, or Best AvailableTechnology (BAT) based on their performance, suitability totreatment plant size, degree of acceptance, conditions requiredfor effective operation, operation and maintenance require-ments, and compatibility with other treatment operations.Established technologies are defined as those commonly used inwater treatment. BAT is defined as a regrrlatory designationthat indicates a level of contaminant removal achievablethrough specification of a technology.
By achieving cost€ffective, pH- and temperature-independentdisinfection of waterborne pathogens including Crypto-sporidium, all without the production of harmfirl disinfectionbJproducts, UV disinfection is unique among disinfectiontechnologies and may be considered a candidate for BAT status.UV disinfection is an accepted viable treatment technology invarious jurisdictions around the world, providing effectivetreatnent at thousands of facilities for flow rates up to 79 MGD.Experience with UV disinfection has demonstrated fl exibility ininstallation, low operation and maintenance requirements, anda compatibility within a multi-barrier approach towards watertreatment. Based on atack record of successful practice andbscked by eight decades of science, W disinfedion can beconsidered an efiablished disinfeaion technologt.
References
Akhlaq, M.S., Schuchmann, H.-P. and von Sonntag, C.(1990) "Degradation of the polysaccharide alginic acid: Acomparison ofthe effects ofLIV light and ozonen, Environ. Sci.Technol., Vol. 24, pp. 379-383.Anonymous (1997) "Helsinki Installs World's l^argest UVSystem for Potable Water Disinfection", Ozone Nevs, 25(2):7 -8.Battigelli; D..d, Sobsey, M.D. and Lobe, D.C. (1993) "Theinactivation ofHepatitis Avirus and other model virusesby UVirradiation", Wat. Sci. Tech., Vol. 27, No. 34, pp.339-342.Berman, D., Rice, E.W. and Hoff, J.C. (1988) "Inactivationof particle-associated coliforms by chlorine andmonochloramine", Appl. Environ. Microbiol. 54(2):507 -5 12.Bernhardt, H. (1991) 'Disinfection of reservoir water withUV-rays'; Proceedings of the SecondBiennial Conference, TheWater Institute of Southern Africa, Mayl3-15, pp. 1440.Bukhari, L, IJarg, T.M., Bolton, J.R, I)ussert' B. andClancy, J.L (1999) 'Medium-pressure UV light for oocystinactivation", J. Am. Water Works Assoc. 9l(3):86-94.Chang, J.C.H., Osoff, S.F., Lobe, D.C., Dot{man, M.H.'Dumais, C.M., Qualls, RG. and Johnson, J.D. (1985)'UVinactivation of pathogenic and indicator microorganisms",Appl. Environ. Microbiology, Vol. 49, No. 6, pp. 1361-1365.Finch, G.R, Gyiirtk, LL., Liyanage, L.RJ., Belosevic' M.(1997) Effect of Various Disinfection Methods on the Inactiva-tion of Cryptospori dium, AWWARF/AWWA, Denver, CO.Finch, G. (1999) Effects of medium pressure UV on Crypto-sporidium parvum andGiardiamuriC', U.S. EPA Workshop onUV Disinfection of Drinking Water, Apnl28-29, 1999.Friedman-Huffman, D. and Rose, J.B. (1998) "Waterbornepathogens. Emerging Issues, Emerging Treatments - Areviewn, Water Conditioning & Purification, August, pp. 48-53.Haas, C.N., D'Andrea, D., Dmochowski, J., Jacangelo, J.,Chellam, S. and Gerba, C.P. (1999) "Inactivation ofLegionella pneumophila by Free Chlorine" Presented at theAWWA International Symposium on Watertorne Pathogens,August 29 - September l,1999, Milwaukee, WI.Harris, G.D., Adams, V.D., Sorensen, D.L., Curtis, M.S.(1987) "Ultraviolet inactivation of selected bacteria and viruswith photoreactivation of bacteria", Wat. Res., 2l(6):681492.IFCI (1997) Uniform Fire Code, Uniform Fire Code Institute,Whittier, CA.Kruithof, J.C., van der Leer, RC. and Hijnen, W.A.M.(1992) "Practical experiences with UV disinfection in theNetherlands", J Water SRT - Aqua, Vol. 41, No. 2, pp. 88-94.Linden, ICG. and Sobsey, M. (2000) Private Communication.Loge, F.J., Emerick, RW., Heath, M., Jacangelo, J.,Tchobanoglous, G. and Darby, J. (1996) nUltraviolet
disinfection of secondary wastewater effluents: prediction ofperformance and design", Water Environment Research, Vol.68, No. 5, pp. 900-916.
t7
Malley, J.P., Shaw, J.P. and Ropp, J.R (1995) Evaluation ofBy-Products Produced by Treatment of Groundwaters withUltraviolet Irradiation, AWWA RF and AWWA, Denver, CO.Malley, J.P. (1999) "UV Disinfection for Drinking Water - ABAT But Not A Panacea", Technology Primer, M /DBP Stage2 FACA Meeting, Washington, D.C., September 23, L999.
Meng, Q. S. and Gerba, C.P. ( I 996)'Comparative inactivationof enteric adenovirus, poliovirus and coliphages by ultravioletirradiation'. Wat. Res., Vol. 30, No. 11, pp.2665-2668.Mofidi, A..d, Baribeau, H. and Deleon, R. (1999)
Proceedings of the AWWA WQTC, Tampa, FL'Oppenheimer, J.d, Hoagland, J.E., Lein6, J.-lVL, Jacangelo'J.G. and Bhamrah, A" (1993) *Microbial inactivation andcharacterization of toxicity and by-products occurring in
reclaimed wastewater disinfected with UV radiation", Planning,Design & Operation of Effluent Disinfection Systems,Whippany, N.J., May 23-25,1993, WEF.Severin, B.F., Suidan, M.T. and Engelbrecht' RS. (1983)
"Effects of temperature on ultraviolet light disinfectiono,Environ. Sci. Technol., Vol. 17, No. 12, pp.717-721.Shin, G.-.d, Linden, IC and Sobsey' M.D. (2000)"Comparative inactivation of Cryptospori dium pawun oocystsand coliphage MS2 by monochrornatic UV radiation',Disinfection 2000: Disinfection of Wastes in the NewMillennium, WEF, New Orleans, LA, March 15-18, 2000'
Snicer, G..d , Malley, J.P., Margolin, A-B. and Hogan' S.P.(1998) 'Evaluation of ultraviolet technolory in drinking watertreatment", AWWARF and AWWA, Denver, CO.Sobsey, M.D. (1939) 'Inactivation of health-relatedmicroorganisms in water by disinfection processesrr, Wat. Sci.Tech., Vol. 21, No. 3, PP. 179-195.Tosa, trL and Hiratao T. (1998) *I{RWM-39:Photoreactivation
of Salmonella following UV disinfection", IAWQ I 9th BiennialIntl. Conference. Vol. 10 Health-Related Water Microbiolory.U.S. EPA (1939) Guidance manual for compliance with thefiltration and disinfection requirements for prftlic water systemsusing zurface water sources. Offtce of Drinking Water, USEnvironmental protection Agency, Washington, DC.U.S. EPA (1990) Technologies for Upgrading Existing orDesigning New Drinking Water Treatment Plants, EPN625|4-891023, U.S. EPA, Cincinnati, OH.U.S. EPA (1996). Ultraviolet light disinfection technology indrinking water application - an overview. EPA 8l l-R-96-002Washin4on, DC: U.S. Environmental Protection Agency,Offrce of Ground Water and Drinking Water'Wiedenmann, A. , Fischer, B., Straub, U., Wang, C.-H.'Flehmig, B. and Schoenen, D. (1993) "Disinfection ofHepatitis A virus and MS-2 coliphage in water by ultravioletirradiation: Comparison of UV-susceptibility'1, Wat. Sci. Tech',Yol. 27, No. 3-4, pp. 335-338.Wilson, B.R, RoesslerrP.F.rVan Dellen, E., Abbavadegan'M. and Gerba, C.P. (1992) "Coliphage MS-2 as a UV waterdisinfection efficacy test surrogate for bacterial and viral
pathogens", AWWA-WQTC Proc. Water Quality TechnoloryConference, Nov 15-19, 1992, Toronto, Canada, pp.219'235.Wolfe, RL. (1990) 'Ultraviolet disinfection of potable water",Environ. Sci. Tech., Yol.24, No. 6, pp. 768'773.Wright, E.B. (2000) "Dose Requirements for WDisinfection',IWA News, Vol 2, No. 3.T,avrleta, J.O., Ilauchman, F.S. and Cox' M.W. (1999)"Epidemiolog5r and toxicology of disinfection by-products". In:Formation and Control of Disinfection By-Products in DrinkingWater, Edited by P.C. Singer, AWWA" Denver, CO.
I-n an effort to serve our members better and to provide better
I directions to our organization, we conducted a membershipIsurvey in early 20@ to get a better understanding of ourmembers' needs and vision. The survey was sent to all existingmembers of IUVA mainly via email -- hopefirlly to get htterresponses. About 160 surv€ys were sent out, and 46 responseswere returned. From the responses, it is obvious tlnt ourresponding members are very excited about this neworganization and many are eager to help and contribute to thesuccess of IUVA.
Among others, we received input for what people would like/notlike to see in the IWA newsletter. This should help to caterour newsletter to suit our readers' needs and plan for ourupcoming issues.
The responses confirmed that we need to broaden our ex?osureto non-water/wastewater areas.
With this first survey completed, however, our job has just
begun. We will need to explore and implement ways to fulfillour members'vision of this world-class organization.
I want to thank all those who took the time to respond to oursurvey. Your efforts will bear fruit.
Questions and summations of the respons€s canbe found on thenext Page (19)'
sylvester S. HsuMembership Committee Chair
l8
IUVA Membership Survey Results (see p. 18)
Ouestion Responses
How did 1'ou hear about IUVA? Frum Board nembers; Through confercnces of other essociationsThrough other rssocietiondagenciesFnom colleaguedother offices within companyThrcueh nublicationsl Through clients/others
Wlnt wae tlre main rcason voujoined II.IVA?
Obtain and get updated info on IIVCurrently involved in IIV projects - want infoNetwork with other IIV industry peopleHave been involved in IIV for long time, wanted to fom one all alongPlatform to share idees, experience with others in IIV industryFurther IIV applicationsComnanv wants to be at forefront of IIV Technolow
How can IUVA benefit yourcompan5'/career?
Get info on IIV - updated development, end future planningPlctform to Serc/erchenge ideas end infoFurther design/manufacture of IIV systemsHelp company to market IIV productdservicesMay use IIV et own facilities in the futureLearn which companies active in the IIV field
Wlut kind of articleVinfowould you like/not like to seein the IUVA newsletter?
Summary/results of pasUon-going/future research projectsCase histories/real-life experience of IIV in different applicationsRegulatory issueVdiscussionsl Domestic/International IIV newsAbstracts of IIV publications;'tIV productdapplication developmentRecent and upcoming [IV-related events announcementsBroader aspect, not just WaterMastewaterO&A area - follow un bv uncomins issuedneonle
Wlut kind of activitieV-frrnctions would 1'ou like IIIVAto organize?
LocaUregionaVinternational conferencesSymposiumdworkshops/seminars/courses - by itself or around othermajor conf (AWWA, etc.) - local or regionalOn-net workshop - people'hook'up and discuss thoughts on theinternet; Field trips to UV installations - regionatSpecialty conference and trade shows on different IIV areas (Technologr,legislative, applicationg research)Graduate scholarshio for IIV research administered bv IIIVA
What interest groups (Water,wastewater, UV curing, foodprocessing, semiconductors,bioteclmolog'. nondestructivetesting, etc.) would 1'ou like tosee formed witlfn IUVA?
Water/Wastewater/Odor ControUSemiconductor/Biotech/llledicaUAirPurification/UV curing/Beverage and food processing/Advancedoxidation/Ultrepu rc water/Aquaculture/Non-destmctive testing/tlVsurface chemistry
wlnt industry groups do 1'oubelieve are currently under-repre sente d within IIJVA?
Everything but water/wastewater - IIV curing/air purification/[IVmeasu nement/ semicon ductors/instrumentVnon-destruction testingUtilities/regulatory agencieVusers-operators of llV(industrial,commercial. residential)/internationals
Side notes IUVA increase credibility of UV TechnologrIIIVA must not be biased. Should not be IIV stakeholder/advocate.Neutral stance: Website set un iob database"
l9
Knowledge Gaps: Wtat is Required for Reliable UV Application?
Fred Soroushian, PE.,
cH2M Hill. 3 Hutton Centre Drive, Suite 200, S-,u o* C onrr,rn "'"
Presented a, tlv-,zooi, lan, zz--ib, 2000, Cista Mesa,,"CA (USil
dvances in UV technology, more efftcient lamps, andmore reliable equipment are increasing,the popularity ofUV disinfection. These advances have resulted in
commercial application of UV for water treatment inpharmaceutical, food, and electronic industries and for
municipal water and wastewater disinfection.
Determining the effrcienry of UV technologies requiresrecognition that it is a combination of UV system (lamp
technology and output spectra, lamp age, reactor hydraulics),water quality parameters, and microorganism's action spectra/-repair capabilities and their state ofaggregation (free or particle
associated) that determines the efftciency of the UV systems andDBP formation. Today, there is not a single model that canreliably predict how the interaction of these parameters impactsthe UV dose and performance of W systems. Therefore, theneed exists for a simple standardized technology validationapproach that integrates the complex variables of UVdisinfection into a simple output that can be measured readily
to assess the performance of UV systems. To achieve thisobjective and assess the performance and reliability of UVsystems, the following major issues need to be addressed:
. Protocol for establishing UV dose and validating UVsystems performance and scale-up.
. Target pathogens and surrogate microorganisms.
. Microorganism response spectra and repair mechanisms.
. UVby-products and associated disinfectionby-products.
. Performance monitoring requirements and instruments.
The following presents these significant W disinfection issuesin greater detail.
Protocol for Establishing UV Dose and Validating
UV Systems Performance and Scale-Up
In addition to the low-pressure low-intensity systems' which arewidely used, other technologies such as low-pressure high-intensity, medium-pressure high-intensity, pulsed UV, andexcimer systems are being proposed for use in water andwastewater disinfection. There are significant differences in
power input, intensity output, lamp arc length, power supply,and reactor configuration among these technologies. Inaddition, UV manufacturers use different methods for estima-ting effective germicidal intensity for polychromatic lamps andfor calculating W dose within the reactor, which furthercomplicates establishing the performance of these systems.
The measurement of UV dose in a non-idealized, continuous-flow UV reactor is complicated by the complex flow patterns,contact time distribution within the reactor, and variations inchemical and physical water quality parameters (Severin, et al.'l983a,b; Qualls et al., 1985). For measurement of UV dose in
bench-scale and pilot-scale systems, two approaches have beenused: (l) to use actinometric methods, either chemical orbiological actinometers (Linden and Darbey, L99'7; andQuallset al., 1989), or (2) to measure W intensity and retention timedistribution with results substantiated by actinometry(Soroushian et al., 1999). Although these methods may besatisfactory for bench-scale dose verification, neither oftheseapproaches alone would b€ completely satisfactory for dosemeasurement in a continuous-flow reactor. Therefore, theprocess modeling of a continuous-flow reactor based on acombination of mathematical modeling, biological or chemicalactinometry, and laboratory measurements using collimatedbeam is the most valuable tool for characterizing the UVdisinfection effrciency for the commercially available UVsystems. Because currently there is not a single protocol fordetermination of the applied UV dose in a non-ideal reactorwith polychromatic lamps, a standardized protocol for measure-ment of UV dose and validation of reactor performance isnecessary.
Target Pathogens and Surrogate Microorganisms
The UV inactivation ofbacterial pathogens indicates that 3-logsinactivation can be achieved with doses of less than l0mWVcm2 (Roessler and Severin, 1996). The pathogenic virusesthat can cause waterborne outbreaks are more resistant. Forexample, the required dose for 3-logs inactivation of viruseswould range from 23 to 50 mWVcm2 for poliovirus, reovirus,Coxsackie virus, echovirus, and BacilluswDfl/ls spores to 55 to
20
a-
65 mWs/cm2 for coliphage MS2. The adenovirus is mostresistant requiring a dose of 80 to 90 mWJcmz @oessler andSeverin, 1996). Recent studies indicate that UV is moreeffective than chemical disinfectants for the inactivation ofprotozoa. Three-logs inactivation of Cryptospori dium requireda UV dose of less than l0 mWVcm2.
Kallenbach et al. (1989) made an interesting observationconcerning the relative resistance of viruses. They noted thatviruses with high molecular weight, double-stranded DNA orRNA, were easier to inactivate than those with low molecularweight, double-stranded genomes. This was similarly true forsingle-stranded viruses. However, viruses with double-strandedgenomes are less susceptible than those with single-strandedgenomes.
Pathogens of concern and emerging pathogens weresummarized at recent EPA-sponsored workshops. Vibriocholerae, Salmonella typhi, Shigella, Mycobacteria, andCampylobacter were listed as pathogenic bacteria. Poliovirus,Coxsackie virus, Norwalk virus, echovirus, rotavirus, andHepatitis A virus were listed as pathogenic viruses.Cryptosporidium and Giardia were listed as pathogenicprotozoa. Mycobacterium avium is an emerging pathogen ofhigh priority and heliobacter, Norwalk, calcivirus, Cyclospora,Microsporidium, and toxin-producing algae are emergingmedium-priority pathogens. However, little is known about theeffectiveness of UV light against many of the emergingwaterborne pathogens. These include Helicobacter pyroli,My co b ac t e r i um av i um, astrovirus, calciviruses, Norwalk virus,picobirnavirus, and picotrirnavirus.
Because of the problems associated with handling of pathogensand the difficulties in their production and assay, surrogates areused for pilot-scale testing. The surrogates, as discussedprwiously, include coliphage MS2, Bacillus subtilis, andGiardia muris. Coliphage MS2 is the most commonly usedsurrogate microorganism. Bacillus subtilis also is used as avirus indicator in IIV disinfection studies. Giardia muris is asurrogate for protozoa.
Recent unpublished work has suggested that the age of MS-2coliphage after production may affect its resistance toinactivation by W light (Gerba, unpublished). Although thegowth state of bacteria is known to affect W light resistance(bacteria are more susceptible to UV light in the log phase ofgrowth), no studies have been done to assess impact of holdingconditions on virus susceptibility (temp€rature, in the presenceof organic matter, pH). Such information is critical toaccurately assess virus inactivation.
Currently, the basic knowledge regarding UV wavelength-specific inactivation and repair of pathogens is deficient.Meulemans (1986) defined an effective W dose obtained bysumming the dose contribution of each wavelength weightedbythe germicidal action spectra of the irradiated microbe.However, the wavelength-specific information regardingmicrobial responses to UV irradiation is limited. Therefore, itis not currently possible to apply more fundamental(wavelength-specific) approach for dose calculation.
DNA/RNA damage caused by UV disinfection can be reversedby microbial repair mechanisms. Exposure of microorganismsto visible light shortly after UV irradiation activates enzymesthat reverse pyrimidine dimers created by W (photoreacti-vation). Even in the absence of light, enzyme systems exciseand rebuild sections of damaged nucleic acid (dark repair).Some, but not all, bacteria are capable ofphotorepair and darkrepair mechanisms. The ability to undertake repair is also afunction of the UV dose, with less repair observed with greaterUV doses. The photorepair ability of a microorganism also isreduced it after W radiation, the sample is kept in the dark fora period of time prior to exposure to visible light (Groocock,1984). Although viruses cannot repair themselves, they mayutilize the enrymes within host cells to undertake repair.
UV By-Products and AssociatedDisinfection By-Products
Compared to chemical disinfectants, UV is considered to formminimal disinfection by-products. Malley et al. (1995) did notfind any significant DBPs in groundwaters or coagulated andfiltered surface waters exposed to UV doses of 60 to 200mWS/cm2. Low levels of formaldehyde were produced in highlycolored waters, and BDOC levels were increased in untreatedsurface waters.
The combination of UV and chlorine did not significantlychange THM production and HAA concentrations (Zheng et al.,1999) wen at doses as high as 4,000 mWVcm2. Von Sonntag(1992) demonstrated that UV can result in the formation ofnitrite ion. Pulsed UV was reported to result in very littlechange in THM and HAA formation and small production offormaldehyde, nitrite, and AOC next to the lamp (Mofidi,1998). Study of by-product formation for medium-pressure,high-intensity lamps in secondary and tertiary-treatedwastewater confirmed that there were no appreciable differencesin concentrations of volatile and semivolatile organiccompounds and THMs between untreated and UV irradiatedwaters, but there were small increases in aldehydes (Soroushianet a1., 1997). Small increases in formaldehyde, acetaldehyde,
21
and glyoxal and a 2-log reduction in g to 16 carbon hydro.carbons with UV doses of up to 150 mWJcm2 with a low-pressure UV system were reported by Awad et al., (1993).
Referenceg
Awad, J. 'Ultraviolet Disinfection for Water, Reuse. planningDesign, and Operation of Effluent Disinfection Systems.' ZEFSpecialty Conference proceedings, Whippany, New Jersey.1993.Groococlq N.H. 'Disinfection of Drinking Waterby UltravioletLight." Journal of the Institution of ll/ater Engineers andScientists. Vol. 38, No. 2. 1984. pp. 163-172.Linden, K and J. Darb5'. 'Estimating Germicidal UV Dose FromMedium Pressure Lamps: Comparison of
. Bioassay,
ldathematical and Chemical Actinometry Approaches.;Proceedings, CSCUASCE Environmentat EigineeringConference. 1997.Malley et al. oEvaluation ofBy-products produced by TreatmentofGrourdwaters With Ultraviolet Irradiatio n., AIIqWA ResearchFoundation and American Water ll/orks Association. 1995.Meulemans, C.C.E. 'The Basic principles of UV-DisinfectionofWater." Ozone: Sci. &Eng.1987.Mofidi, A.A., et. al., Disinfection Using High-Intensity pulsed_Ultraviolet Irradiation, AWl,yA proceedings Watei euatityTechnologt Conference, San Diego, CA, November 199g.Qualls, R-G., M.H. Dorfinan, and J.D. Johnson. "Evaluation ofthe Effrciency of [lltraviolet Disinfection Systems." ZalerResearch.1989.Qualls, R-G. and J.D. Johnson. "Modeling and Effrciency ofUltraviolet Disinfection Systems.' lVater Re se arc h. I 9g5.Roessler, P. and B. Severin. ,Modeling Disease Transmissionand Its Prevention by Disinfection." Cambridge UniversityPress. 1996.Swerin, B.F., M.T. Suidan, and R-S. Engelbrecht. "KineticModeling of UV Disinfection of Water." llater Researeh.1983a.Soroushian, F., J. Norman, M. patel, G. Leslie, and G.Tchobanoglous. "Is There a Standard Method for ComparingUltraviolet Disinfection Technologies?', in proce e di ngs, WatiEnvironment Federation 72nd Annuat Confereice andExposition. 1999 .Soroushian, F., C. Abramson, M. Ferris, and A. Mohammed."Pilot-Scale Studies of High-Intensity UV Disinfection By_products." in Proceedings, l{EF Annual Conference aidExposition. 1996.Von Sonntag, C. and H.p. Schuchmann, UV Disinfection ofDrinking Water and By-product Formation -- Some BasicConsiderations, Aqua, Journal I'\/SR&T, Apil 1992.Zheng, M., Andrews, S.A., Bolton, J.K, Impacts of MediumPressure IIV and lJIy'lHzOz on Disinfection By_productFormation, Technical Proceedings AWI/A NationalConference, Chicago, IL, June 20-24. lggg.
This extended abstract appears in W 2000 _ A TechnicalSymposium, published by and available from the National WaterResearch Institute, 10500 Ellis'Avenue, p.O. Box 20g65.FountainValley, CA 927254865; Fax: 714-379-3375: email:[email protected]. price = $15.00 (U.S.).
Therm odynamici of Heil,Ouestibntd, . ' 'on =rhivemity Exeminition,,,,.,', ',
verett W. Hobart of Spencerporq N.y., couldn't believehi-s eyes upon finding inthe National Catholic Reporterof Jan. 28 an intriguing bonus question from the midterm
chemistry exam at the University of Washington:
Is hell exothermic or endothermic?
The only student who got an A on the question responded asfollows (in paraphrased form):
First, you must know the rate of change of the mass of hell _-the rate at which souls are moving into and out of it. you cansafely aszume that nobody is leaving. Members of most of themany religions contend that members of all others end up inhell, so you can project that all souls go there. Given currentbirth and death rates, the number of souls in hell - its mass _can be expected to expand exponentially.
For temperature and pressure in hell to stay the same, thevolume must expand as souls are added. The student wrote."This offers trvo possibilities:
If hell is expanding at a slower rate than tlp rate at which soulsenter, then the temperature and pressure will increase until allhell breaks loose.
Ifhell is expanding at a rate faster than the increase ofsoulsthere, then the temperature and pressure will drop until hellfreezes over.n
lack & Veatch is an employee-owned consulting,engineering and construction firm serving infrastructure,environmental and other markets from offtces around the
world. With a dedicated Global Process Design Team and aworld of utility and industrial experience, we offer specialexpertise in advanced water and wastewater treatment. Black& Veatch Corporation was recently ranked No. 1 in Water andNo. 8 in SewerAVaste among the top 500 design firms byEngineering News-Record (April 2000), while subsidiary BinnieBlack & Veatch was ranked #2 in Water and Wastewater amongUK firms by NCE (March 2000).
The Black & Veatch companies - including Paterson CandyLtd. as well as Binnie Black & Veatch and Black & VeatchCorporation - have an impressive history of incorporating UVin both water and wastewater treatrnent process€s. Our UVexperience ranges from basic and applied research to theapplication of UV for disinfection and advanced oxidation forlarge treatment facilities. As a leader in tackling toughtreatment challenges through the use of emerging technologies'we can help our clients fully hnefit from UV options and builda better world.
Key Contacts: Black & Veatch: - Lee Harms, Bob Hulsey,Gary Hunter - 8400 Ward Parkway, Kansas City, MO, U.S.A.64114. Tel.: 913458-2000: Fax: 913-458-3730
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Internet Si tes: www.bv.cont. www.bbv- l td.com.ww1r" Daterson cand\'. coln
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Typical Applicationso Lamp Aging - monitoring irradiation decay. Air Pollution - gas monitoring. Water Analysis - ozone detection in water. Medical - blood analysis
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II.Vto be Emphasized at AWWA's,,,WQTC November,20,00 Meeting
his coming November 5-8 LIV technologies will befeatured during the AWWA's Water Quality Technoloryconference in salt Lake city, utah (usA).
Three separate sessions on UV are planned, two of which arecalled "UV Disinfection I and II". Each of these sessions has 6papers. There also will be a Sunday workshop, the descriptionof which is given below.
Lastly, there will be a day-long technical tour to a local facility,the Utah County Water Consewancy District and theTimpanogas Wastewater Facility, (Minimum 30, Maximum 45p€ople). Participants on this tour will learn about and seeultraviolet technolory and its use in the water industry.
Sunday Preconference WorkshopWl . WDISINFECTIONSunday, November 5, 20008:30 a.m. - 5:00 p.m.Moderator: Gil Crozes
(A portion of the workshop to be held off-si1s at Utah Valleyl{ater Treatment Plant in Orem, Utah. Limited to 40 attendees)
The overall goal of this workshop is to familiarize the attendeeswith the basic theory of UV disinfection, and the systemscomponents, as well as testing, design, and implementationissues. This workshop will provide the attendees with apractical understanding of the UV disinfection for drinkingwater applications.
The workshop will have technical overview presentations andhandson interactive workshdp stations.
Technical Overview (held at conference center)
8:30 Thomas Hatg, Clancy Environmental Consultants,Inc., How and Why W Shows Promise for DrinkingWater Disinfection?
9:00 James Malley, University of New Hampshire, HowDoes UVWork?
9:30 Bruce Macler, U.S. EPA, Regulatory Perspective andStatus Update
10:00 Break10:15 James Bolton, Bolton Photoscienges; Inc., What UV
dose is required for chemical oxidation?10:45 Gil Crozes, Carollo Engineers, As a New Water
Treatment Tool, How Do UV Technologies Fit amongOther Technologies?
ll:30 Lunch
12:30 Bus departs for afternoon session
Interactive Sessions (off-site, bus departing at 12:30 fromthe convention center)
Station No. 1 - Methodologr of Bench-Scale Bioassay Uringa Collimated Beam Apparatus Station Animator: Dr. KarlLinden
In this workshop statioru a collimated beam (CB) apparatus willbe described. Key features and design components of the CBapparatus will be reviewed and a MS-2 virus challenge studywill be performed. A "cooking shoC' approach will be usdwith precultured plates at various stages of MS-2 growth. Asimilar experiment will be demonstrated vsingbacillus spores.Dose response results will b€ presented for various watermatrices.
Station No 2 - Flow-Through Pilot-Scale BioassayMethodologr Station Animators: Dr. James Malley and Dr.Jennifer Clancy
In this session; the methodology of bioassay in dynamicconditions of industrial size units will be demonstrated. Similarto the CB Workshop Station, a "cooking show" approach willbe used, with prectltured plates ofboth MS-2 and spores. Doseresponse obtained in flow-through conditions will be pr€sentedand compared to the data generated using a CB apparatus forsimilar water matrices. The impact of hydraulic behavior oftheUV contactor will be demonstrated by comparison betweenbatch and flow-through dose response results.
Interactive Work Session No. 3 - Hands-on Evaluation of IIVSystem Components Station Animators: Dr. ErinMackey andDave Hardy
For this workstation, two UV systems will be dismantled andthe critical components will be available for examination.Special emphasis will be given to the lamp g'pes, sleeves,cleaning mechanisms, hydraulic confi guratiorl operation andmaintenance features.
Monitoring and reporting issues will be discussed andillustrated. Dave Hardy will provide key input regarding UVsystem operations based on pilot system experience. Operationand maintenance issues for various commercially availablesystems will be discussed and addressed.
26
Interactive Workshop Station No. 4 - Approach to Design ofIIV Systems Station Animators: Dr. Bob Cushing and Dr.Chip BlatcNey
In this workshop sessioq the various commercially availableW systems will be reviewed and compared. Key design criteriawill be outlined. An approach for developing design criteria forspecific applications (i.e., typre of microorganisms to beinactivated, level of inactivation, UV dose effect on watermatrix) will b€ discussed.
Approaches for integration of UV in existing water treatmentplants will be reviewed. The predesign studies for three UtahWater Treatment plants will be described using variousdisplays. A rational approach for system preselgction will bedescribed along with suggested approaches for proprietary UVequipment procurement.
Panel Discussion
At the end of the day, the attendees will regroup for a generalsession in a panel discussion format. The panel will b€composed of the various speakers and workshop stationsanimators.
Water Treatment Rule (SWTR). These rule revisions are beingdriven in part by a need to control Cryptosporidium anda need
to reduce risk associated with disinfection blproducts withoutcompromising microbial risk.
UV disinfection is an appropriate technology to me€t the needsof both the D/DBPR and the SWTR. Animal infectivity studieshave sho*n that W disinfection at relatively low dosesprovides several logs of Cryptosporidium and Giardiainactivation'(Bukhari et al, 1998; Finch, 1999). UV disin-fection also has been shown to inactivate a wide range of
waterborne pathogenic virus and bacteria without producing
significant DBPs (Wolfe, 1990). UV disinfection can solve thedilemma of balancing microbial and DBP risk and offers aviable solution to disinfect ing C ry p to s po r i di u m.
Currenfly, LfV disinfection is being evaluated across the UnitedStates. The U.S. EPA has a Technical Working SubGroupinvestigating the potentials of UV for the Stage 2 SWTR. NSF
of Ann Arbor, Michigan is reviewing the role of tfV for home
applications in their rewrite of Standard 55. And the State of
California is reviewing the role of UV within Title 22
applications involving water reuse. These efforts all face
similar challenges. This paper attempts to address several of
these challenges, namelY,
. What UV dose is required to disinfect potable water, and
. What safety factors should be incorporated into thoserequirements.
Current UV Dose Requirements
Various jurisdictions throughout the world specifr different UV
dose requirements (U.S. EPA, 1996) (see Table l). In 1966, theUnited States Department of Health, Education, and Welfare
@HESD proposed a UV dose guideline of 16 mJ/cm2 for
disinfecting potable water used on ships'
Introduction
he Safe Water Drinking Act Amendments mandate theU.S. EPA to promulgate-revisions to the.DisinfectanU-Disinfection By-Products Rule (D/DBPR) and the Surface
ANSINSF Standard 55-1991 defines two standards for Point-of-Use and Pointof-Entry UV disinfection systems. Class A
UV disinfection units are designed to disinfect virus andbacteria to safe levels and must provide a minimum UV dose of38 mJ/cm2. Class B units are designed for the supplementaldisinfection oftreated and predisinfected public water and mustprovide a minimum dose of 16 mJ/cm2. NSF stated that a doseof 16 mJ/cm2 would provide greater than 2-logs inactivation ofnon-spore-forming heterotrophic bacteria and a dose of 38mJ/cm2 would provide 4-logs of inactivation of poliovirus androtavirus. The standard also requires that dose delivery by acommercial UV reactor be validated by comparing the disinfec-tion achieved in the reactor using a challenge microbe (either
Saccharomyces cerevisiae or Bacillus subtilis) to the UV dose-response curve obtained using a lab-scale collimated beamapparatus.
The SWTR requires a W dose of 2l and 36 mJ/cm'to provide'
respectively, 2- and 3-logs inactivation of IIAV. This doserequirement incorporates a safety factor of 3. The Small SystemCompliance Technology List for the Surface Water TreatmentRule lists the NSF Class A standard of 38 mJ/cm2 as a suggestedlower bound and 140 mJ/cm2 as an upper bound. The upperbound is based on 4-logs virus or MS2 reduction with a safetyfactor of 2 to 3. Noteworthy is that 140 mJ/cm2 also is theNational Water Research Institute proposed guideline for
wastewater reclamation in California to disinfect filteredsecondary wastewater.
The German and Austrian standards require a UV dose of 40
mJ/cm2 to provide at least 4-logs reduction ofpathogenicvirusesand bacteria.
Chemical Disinfectant Dose Requirements
The Guidance Manual for Compliance with Filtration andDisinfection Requirements for Public water Systems UsingSurface Water Sources (U.S.EPA, 1989) includes in AppendixF the rationale for the CT values for the inactivationof Giardiaand virus by chlorine, chlorine dioxide, ozone, and chloramines.In this rationale, all CT values include a safety factor to accountfor the limited availability of inactivation data, the variability in
the inactivation data, and the extrapolation ofinactivation data
28
Table l. Present UV Standards for Water Disi
Jurisdiction Year Dose Requirement(mJ/cm2)
U.S. DHEW 966 T6
ANSI/NSF 55 Class A 991 38
ANSI/NSF 55 Class B 991 t6
SWTR- 2-loes HAV 989 2l
SWTR- 3-loes HAV 989 36
Small System Compliance Technology List forthe SWTR
t997 38-140
Austrian Standard OHOnU M 5873 1996 40
German DVGW Standard W294 1997 40
to other pH levels, temperatures, disinfectant demands,disinfectant concentrations, and inactivation levels. Table 2summarizes the safety factors incorporated into currentchemical disinfectant CT requirements.
With chlorine inactivation of Giardia, inactivation data from ananimal infectivity study was combined with data from an excys-tation study and fitted using multivariate regression as afunction of inactivation level (I), chlorine concentration (C), pH,and temperature (T). The regression equation was used topredict the 99fr percentile confidence level for 4-logsinactivation at a temperature of 5oC and a given pH andchlorine concentration. Assuming first order kinetics, this CTvalue was used to estimate CT values at lower levels of inactiva-tion. The effect of temperature then was estimated assuming atwo-fold decrease for every 10Co increase above 5oC.
CT requirements for Giardia inactivation by chlorine dioxideand ozone were derived from 2-logs inactivation data obtained"respectively, at pH 7 and pH 5 and extrapolated to other pHvalues, inactivation levels, and temperatures. A safety factor of1.5 was applied to the average dose observed with chlorinedioxide while a safety factor of 2 was applied to the highest doseobserved with ozone. A larger safety factor for the disinfectionof Giardiaisapplied to ozone and chlorine dioxide compared tochlorine in part because (a) less data are available for ozone andchlorine dioxide compared to chlorine and (b) data for ozoneand chlorine dioxide are based on exrystation studies, whichdue to limitations of the excystation method, only reflect slightlybeyond two logs of inactivation.
CT requirements for virus inactivation by chlorine and chlorinedioxide are based on HAV inactivation data since HAV wasfound to be more resistant to these disinfectants than poliovirusand rotavirus. Lacking HAV inactivation data, CTrequirements for virus inactivation by ozone are based onpoliovirus. A safety factor of 3 was applied to the highest doseobserved with chlorine, a factor of 3 was applied to the average
nfection
dose observed with ozone, and a factor of 2 was applied to theaverage dose observed with chlorine dioxide.
Where chloramination involves ammonia addition followingchlorine, the chlorine disinfection that occurs during the shortchlorine contact time prior to tlte ammonia addition acts as asafety factor. Accordingly, no additional safety factor wasapplied to the chloramine CT values.
The CT values for the inactivation of Giardia and virus bychemical disinfectants do not incor@rate safety factors toaccommodate for disinfection equipment performance. Instead,equipment performance is dealt with by requiring that CTvalues be calculated using T,6, the time required for l0% of theflow to pass through the disinfection contact chamber. Ttovalues are determined through either tracer studies or estimatesbased on contact chamber design.
Rationalizing UV Dose Requirements
Dose requirements for different disinfection technologies shouldbe based upon a rationale that is consistent among those tech-nologies. A bias favoring one technolory over another will notlead to the optimal application of water treatrnent technologiesnor optimal public health protection. Ideally, dose requirementsshould be based on pathogen reduction levels that have beenderived using risk analysis that incorporates occurrence ofthepathogen in the raw water, the impact of multi-barrier watertreatment, and human dose-response @egli et al, 1991).
Dose requirements for UV disinfection should be designed toprotect the public from outbreaks of disease caused bywaterborne pathogens. To be practical, regulations should bebased on pathogens (see Table 5) that have been associated withwaterborne outbreaks due to drinking water (e.g., HAV, rota-virus, Giardia, Cryptosporidium) as opposed to indicatormicrobes or pathogens that have not been associated with suchoutbreaks [e.g., MS2 phage, adenovirus (Meng and Gera,
29
Table 2. factors into chemrcal dlslnlectant C'I
Disinfectant Giardia CT SafetyFactor
Target Virus Virus CT Safetytr'actor
Chlorine 99ft percentile HAV 3 'max dose
Chlorine dioxide 1.5 ' mean dose HAV 2 ' mean dose
Ozone 2 ' max dose Poliovirus 3 ' mean dose
Chloramine None applied HAV None applied
1996)1. This approach is consistent with current requirementsfor chemical disinfectants. For example, CT requirements forvirus inactivation by chlorine currently are based on HAVinactivation wen though coliphage Vl, MS2, and reovirus allhave been reported to be more resistant to chlorine than HAV,with coliphage Vl being more than an order of magnitude moreresistant (Grabow et a1,1983). Future research on UV andchemical disinfectant dose-response needs to focus on thosewaterborne pathogens not yet evaluated.
Safety factors for UV dose requirements should be based on thevariability observed in reported UV dose-response data. A 99ftpercentile confidence limit can be defined for UV dose-responseand is accepted as appropriate with chlorine disinfection ofGiardia. Aspects of UV dose-response that justiff using a 996percentile confidence limit to define UV dose requirements asopposed to a2 or 3 times safety factor are:
. Suffrcient data exists from numerous sources to define doserequirements (mean + standard deviation) for a range ofwaterborne pathogens ofconcern through a wide range ofinactivation levels (0 to > 4 log).
. Extrapolation of dose-response data is not required. UVdose-response is not dependent on pH, temperature, IIVintensity, nor UV demand over the range of these variablesseen in drinking water applications.
Figures I and 2 present, respectively, the UV dose-response datareported for HAV and rotavirus. A first order kineticsassumption was used to estimate mean and the 99h percentiledose requirements to achiwe a given log reduction.
Figure 3 presents the IJV dose-response of Cryptosporidiumparvum oocysts as reported by four research groups. Crypto-sporidium dose-response shown in Figure 3 demonstrates rapidinactivation at low doses followed by tailing at higher doses.The reported tailing at higher doses may be related to theclumping of the oocysts, inhomogeneous irradiation by thecollimated beam apparatus, or the presence ofa resistant sub-population. The latest researchonCryptosporidium (Shin et al.,2000), howwer, demonstrates nearly three logs of inactivationwithout tailing. Thus, the tailing shown in Figure 3 probably isdue to experimental methods as opposed to a resistant sub-population.
Due to tailing effects, the variance in the W dose required ttachieve a given log inactivationof Cryptosporidium, as showrin Figure 3, increases with inactivation level. A 0.5-lo1inactivation was achieved on average with a UV dose of 2.3mJ/cm2 with an associated 99h percent confidence interval ol6.1 mJ/cm2, while 2.5-logs inactivation was achieved with anaverage dose of 5. I mJ/cm2 and a 99e percentile of 17 mJ/crn-r.If tailing effects are shown to be an artifact of the experimentalmethods, lower dose requirements will be justified.
Figure 4 presents the W dose-response of Giardia muris cystsas reported by Finch et al (1999). Given the limitations of thedata, a99m percent confidence limit was not calculated. WhileGiardia muris has a UV sensitivity similar to that of Crypto-sporidium for up to 2 logs ofinactivation, considerable tailingin the UV dose-response was observed for inactivations beyond2 logs; Data soon to be released, however, will show up to 4-logs of inactivation of Giardia oocysts unafiected by tailing(Linden and Sobsey, 2000).
Based on data presented in Figures I through 4, Table 4presents a proposal for disinfection credits for UV disinfection.UV disinfection might be used as either a primary disinfectiontechnology, as a codisinfectant with chlorine to achieveprimary disinfection, or as an addon technology to achieveCryptosporidium and Gi ardi a inactivation credits. Dependingon the disinfection credits achieved by water treatment proc€ssesupstream, primary disinfection using W would be expected toachieve either 2, 3 or 4-logs of virus inactivation credit. SinceGiardia, Legionella, and Mycobacterium are resistant tochlorine but sensitive to uv (Table 5), w used in tandem withchlorine might prove a very effective primary disinfectionstrategy.
With chemical disinfection systems, the dose delivered iscalculated as the product of the measured chemical disinfectantresidual and the estimated or measured T'0. With UVdisinfection, W dose delivered by UV reactors is a complexinteraction of UV intensity and fluid flow fields through thereactor. Residence times can be short (<l s) making tracerstudies diffrcult if not impossible to perform. Divergence of UVemitted from the lamps and UV absorbance by the water willlead to UV intensity gradients throughout the reactor.Accordingly, there is no simple calculation, similar to the CT
30
acalculation used with chemical disinfectants, that may be usedto represent the dose delivered by UV reactors.
o Wedennnnn etal. 19So BattigBlli etal, 19@ oa \Mlson et al, '1992
-lulean ./ /- 'St |% .a /
B-a/o-/ o /
q%
1015?o
UV Dose (mJrcrnl
Figure 1. Hepatitis A virus UV dose-response.
?o304050@
UV Dose 1mJ/cm2)
Figure 2. Rotavirus UV dose-response.
As an alternative to calculating UV dose delivered by Wreactors, many jurisdictions using UV disinfection require Wreactors be assessed by an independent third party for their UVdose delivery through a validation/certification process @VGW,1997; ASI, 1996). In the validation process, UV dose deliveryby the reactor is directly measured using a microbiological assay(bioassay) as a function of flow rate through the reactor, UVabsorbance of the water, and the UV intensity measured usingthe reactor's on-line UV intensity sensor. Dose delivery by thereactor, as established by the bioassay, is assured when the UV
intensity sensor reads above a set point value for a given flowand UV absorbance. Certification of the reactor provides theend user with reactor performance data that can be used toensure compliance to UV dose requirements.
.oA
c dro'toao
{ {o o
zi--u l Lz 'o {^ // : Y:it':'i' 'l*:o Bukhari et al, 19S.rde /8 I t^ , a Finch etal, 1999;Jf r-f l ;
i r sffnetal '2ooo
.'L - ' -Mean>ol- '99th Percentile
UV Dose (rrJ/crn]
Figure 3. Cryptosporidium oocyst UV dose-response(Adapted from Malley, 1999).
3.5
3
543to
trJoga2
J
1
-E z.s.E
"Z^E.oE r.sIJ1
0.5
0
30x
10
55E+EE3
9,1
4
3.5
ac9 rc
IE2E
8'-Jl
n5
0
A Finch et al, 1999
- Mean
1040 60
UV Dosc (mJ/cm2)
Figure 4. Giqrdia muris cy*.UV dose-response.
Key to ensuring UV dose delivery by the reactor is the on-lineUV sensor. On-line sensor measurements must be verifiableusing a reference sensor calibrated to a traceable standard.Ensuring dose delivery by an installed W system will requirethat the end user regularly compare the measurement made withthe on-line sensor to that ofthe reference sensor. If they differby a predetermined amount, the on-line sensor must be eithercleaned, recalibrated, or replaced.
o Changetal, l9B5o Battigelli et al, 1993
^ \Mlsonetal. 1W
' Sniceretal, 1S8 o -/
o. '
- lVlean -/ ' , '
o)- /
-/
31
w2tertnrne (Friedman-Hufftnan and 99E
Enteric virusesHeoatitis A and E* Rotavirus* Echovirus*
Norwalk* Coxsackie*
Protozoan ParasitesC rypto spori d i um parvum * Microsporidia* Toxoplasma gondii*
Leoio nel I a p ne u mo Phil a Leptospira Ye rsi ni a e nterocolitica
Campvlobacter ieiuni Shiseila M vcob acte ri u m t u be rculosis
E. coli OI57H:7* Helicobacter pyloi* Mvcobacterium avium*
The dose delivery set point must include a safety factor to
account for the measuremgnt uncertainty of the sensor and, in
the case of multi-lamp reactors, the variability in UV outputfrom one lamp to the other. Since approaches towardsmonitoring and controlling UV reactors will vary among
manufacturers, the dose delivery set point also will vary. For
example, if a single UV sensor with a measurement uncertainty
of l}o/"is used to monitor a bank of 10 lamps whose UV outputper lamp may vary up to 20%o from lamp to lamp, the dose setpoint value must be increased above and beyond the regulatoryiequirement by those uncertainties. In other words, if the
syite* is targeting a dose of 45 mJ/cm2 to achieve 4 logs of
rotavirus CT credit, ttre sy$em alarm set point must correspondto a bioassay equivalent dose of 1.1 x 1.2 x 45 = 59.4 mJ/cm2'
On the other hand, if the UV reactor uses one sensor per lamp,
the system s€t point must be based on the lowest sensormeasurement made and must correspond to a dose equal to theregulatory requirement plus the sensor uncertainty. Notable is
994
that the reference sensor may be used to measure the lamp-to-lamp variability as well as validate the on-line sensor.Confidence limits on lamp-to-lamp variability may be calculatedusing standard statistical methods.
This approach for defining equipment safety factors allows the
UV industry to develop differing designs without compromisingpublic health protection. Regulators must ensure protocols for
certificationfualidation include an ass€ssment of varianceassociated with UV sensor mea$uements and lamp UV output.
Conclusions
Current disinfection practice used with chemical disinfectionprovides a framework upon which to rationalize doserequirements for W disinfection. UV dose requirementsshould be based on waterborne pathogens that cause a knownhealth impact arising from the consumption and utilization of
@hogens as listed in Friedman'Huffman and Rose (1998).
disinfection credits for UV disinfectionTable 4. A for
RemovalCredit
HAV Rotavirus Cryptospori.diumparvum
Giardiamuris
MeanDose
99t o/o
DoseMeanDose
99ft o/o
DoseMeanDose
99h Vo
DoseMeanDose
0.5 2.3 6.1 0.8
1.0 3.0 7.4 t .2
t .5 J-t 9.3 1.9
2.0 l0 t7 I7 25 4.3 12 3.6
2.5 5.1 t7 l0
3.0 15 2l 26 35
4.0 20 26 36 45
32
able Relative sensit ol-mrcrobes to UV and chlonne
Microbes Disinfectant Dose Ratio Reference
3log Giardia:3log HAV
Chlorine, pH6,5oC 34-71 u.s. EPA (1s8e) CTdata without safety
factorChlorine, pH 6, 25"C 51-107
Cryptospo idi u m pa Nu m'.HAV
ChlorinepH 6-7. -4-5'C
106 Sobsey, 1989
Myco bacte i u m fo rt u it u m:HAV
ChlorinepH6-10
>190 Grabow et al, 1983
2 fogs Legionella:2 foos Giardia
ChlorinepH 6-8,5-25'C
2-8 Haas et al, 1999
4logs HAV:4 loos Rotavirus
UV 30/36 = 0.82 Wilson et al, 1992
2logs Giardia muis:2loos Rotavirus
UV 3.6/19 =0.19
Finch et al, 1999
3logs C. paruum:3 loos rotavirus
UV 3.2t26 =0.12
Shin et al, 2000
4logs Mycobacteiumsmeo matis:4 loos rotavirus
UV 20136 = 0.56 Hoyer, 1998
4 logs Legionella:4 logsrotavirus
UV 9.4/36 =0.26
Wilsonet al, 1992
Note: Dose ratios for UV are relative to rotavirus requirements as reported by Wilson et al (1992).
drinking water. Rotavirus is the most UV-resistant pathogenthat has been associated with waterborne outbreaks of diseasedue to drinking water and as such is appropriate as the target forvirus inactivation credits. Tables defining disinfection creditsfor the UV inactivation of Giardia, Cryptosporidium, andviruses are needed. These tables will reflect the relative UVsensitivity of these microbes and will therefore allow a range ofapplication strategies to be identified from using UV as an add-on technolory for Cryptosporidium control to a compliancetechnologr for primary disinfection. As is the case withchlorine disinfection, dose requirements in these tables shouldbe based on the 99ft percent confidence level ofthe publishedUV dose-response data for the target pathogens. Since Wdose-response data exists over the required range ofinactivationlevels for the target microbes and UV dose-response is notdependent on water temperature, pH, the applied UV intensity,nor the UV demand of the water, a 99h percentile confidencelevel is more appropriate for W disinfection dose requirementsthan an arbitrary 2 or 3 times safety factor.
All commercial W reactors must undergo validation andcertification through an independent third party. Validatior/-certification will determine lhe reactor's UV dose delivery as afunction of the flow rate through the system, the absorbance ofthe water, and the UV intensity measurement made by the
reactor's on-line UV intensity sensor. Certification is anassurance to the end user and regulators that the W qystem willdeliver a target dose.
The UV dose targets for installed systems must equal theregulatory requirement specified in the dose table plus a safetyfactor to account for equipment performance. This safety factorarises largely from the uncertainty associated with measure-ments made by online W intensity sensors and, in the case ofmulti-lamp reactors, the variability in UV output from lamp tolamp. A reference sensor calibrated to a traceable standardmust be used by end users and health authorities to verirymeasurements made by the on-line sensor and veriS claimsmade on the output of UV lamp.
References
ASI ( 1996) Plants for the Disinfection ofDrinking Water UsingUltraviolet Radiation, Austrian Standards Institute, Vienna,Austria.Battigelli, D.A., Sobsey, M.D. and Lobe, D.C. (1993) *The
inactivation of Hepatitis A virus and other model vinrses by UVirradiation", Wat. Sci. Tech., Vol. 27, No. 3-4, pp. 339-342.
JJ
Bitton, G. (1994) Wastewater Microbiology, Wiley-Liss, Inc',
New York, NY.Bukhari, Z.,Hatgy,T.M., Bolton, J.R., Dussert, B. and Clancy,
J.L. ( 1999)'Medium-pressure Wlight for oocyst inactivation',
J. Am. Water Works Assoc. Vol' 91, No. 3, pp' 86-94'
Dumais, C.M., Qualls, R.G. and Johnson' J'D. (1985) 'UVinactivation of pathogenic and indicator microorganisms",Appl. Environ. Microbiology, Vol. 49, No. 6' pp. 1361-1365'DVCW (1997) W Disinfection Devices for Drinking Water
Supply - Requirements and Testing, DVGW Deutscher Verein
des Gas- und Wasserfaches e.V., Bonn, Germany.Finch, G. (1999) Effects of medium pressure UV on
Cryptosporidium parvum and Giardia muris", U'S' EPA
Workshop on WDisinfection of Drinking Water, Apil28'29,
t999.Friedman-Huffman D. and Rose, J.B. (1998) 'Waterbornepathogens. Emerging Issues, Emerging Treatments - A
ieview', Water Conditioning & Purification, AugusL pp' 48-53'
Grabow. W.O.K., Gauss-Muller, V., Prozesky, O'W' andDeinhardt, F. (1983) "Inactivation of Hepatitis A virus and
indicator organisms in water by free chlorine residuals", Appl'
Environ. Microbiologr, Vol.46, No. 3, pp. 619424.Haas. C.N., D'Andrea, D., Dmochowski, J., Jacangelo, J',
Chellam. S. and Gera, C.P. (1999) "Inactivation of Legionella
pneumophila by Free Chlorine" Presented at the AWWA
International Symposium on Waterborne Pathogens, August 29
- September 1,1999, Milwaukee, WI.Hoyer, O. (1993) *Testing performance and monitoring of W
systems for drinking water disinfection', Water Supply, Vol' 16,
No. l/2, pp.424429.Linden, K.G. and Sobsey, M. (2000) Private Communication'Malley, J.P. (1999) "UV Disinfection for Drinking Water - A
BAT But Not A Panacea", Technology Primer, M /DBP Stage
2 FACA Meeting, Washington, D.C., Septembet 23,1999'Meng, Q.S. and Gera, C.P. (1996) "Comparative inactivation of
enteric adenovirus, poliovirup and coliphages by ultravioletirradiation'. WaL Res., Vol. 30, No. I l, pp.2665-2668.
Mofidi, A.A., Baribeau, H. and Deleon, R. (1999) Proceedings
of the AWWA WQTC, TamPa, FL'Regli, S., Rose, J.8., Haas, C.N. and Gera, C.P. (1991)
"Modeling the risk from Giardia and viruses in drinking water",
Journal AWWA, November, 1991.Shin, G.-A., Linden, K. and Sobsey, M'D. (2000) "Comparative
inactivation of Cryptosporidium parvum oocysts and coliphageMS2 by monochromatic UV radiation", Disinfection 2000:
Disinfection of Wastes in the New Millennium, WEF, New
Orleans, LA, March 15-18, 2000'Snicer, G.A. , Malley, J.P., Margolin, A.B. and Hogan, S.P.(1998) "Evaluation ofultraviolet technology in drinking water
treatment". AWWARF and AWWA, Denver, CO.Sobsey, M.D. (1939) "Inactivation of health-related micro-
organisms in urater by disinfection processes', Wat. Sci. Tech.,
Vol. 21, No. 3, PP. 179'195.
U.S. EPA (1996). ultraviolet light disinfection technology in
drinking water application - an overview. EPA 811-R-96402
Washington, DC: U.S. Environmental Protection Agency,
Offrce of Ground Water and Drinking Water.U.S. EPA (1989) Guidance manual for compliance with the
filtration and disinfection requirements for public water systems
using surface water sources. Office of Drinking Water, US
Environmental protection Agency, Washington, DC.
Wiedenmann, A. , Fischer, B., Straub, U., Wang, C'-H',Flehmig, B. and Schoenen, D. (1993) "DisinfectionofHepatitisA virus and MS-2 coliphage in water by ultraviolet irradiation:
34, pp. 335-338.Wilson, B.R., Roessler, P.F., VanDellen, E., Abbaszadegan,M'
and Gerba, C.P. (1992) "Coliphage MS-2 as a UV water
disinfection effrcacy test surrogate for bacterial and viralpathogens", AWWA-WQTC Proceedings, Water QualityTechnolory Conference, Nw 15-19, 1992, Toronto, Canada, pp'
2t9-235.Wolfe, R.L. (1990) "Ultraviolet disinfection of potable water",Environ. Sci. Tech., Vol. 24, No. 6, pp. 768-773.
Send for your FREE copy of the Booklet" lJ ltraviolet Application s H andbook'
bY James R Bolton, Ph.D.
Bolton PhotosciencesInc.
Offering consulting and research services in'
' Ultraviolettechnolo€ies;
. Ultravioletdisinfection;
. Advanced Oxidation destruction ofpollutants in contaminated watens;
By David HarbourneFusion Systems, InC-, Gaithersburg, MD
T TV *ting technolory has made tremendous strides in tlre
| | taS century - from the first commercial successes in the\-rr 1960s to today where we find applications such as
overprint varnishes in the graphic arts industry, medical prodrrctassembly, optical fiberoating and CD/DVD production whereUV curing is considered the norm. With only 3o/; to 4%o of allcoatings being UV cured, we still have far to go, and manyopportunities lie before us in the next century. As we enter thenew millennium, it is important to take a look at the challengesW curing technology faces, from an equipment and processperspective, and the likely advances that will be made. Thisunderstanding can lead to new insights and greater success forthe UV curing industry in the next millennium.
Macro Trends
To better understand future customer needs and project futureadvances and impediments to overcome, it is helpful to look atthe external trends affecting every business today. First andforemost is that we live in a global economy. This means thatwhat happens to Asia's economy affects others, that the workforce is more diverse and that more economies are nopening
up." WeVe already seen consolidations among raw materialssuppliers and formulators. Will we see continued consolidationof the equipment manufacturers or among equipment rnnu-facturers and raw materials or formulating companies?Increasingly, companies will have to have a global presence tobe players in this global economy. Equipment manufacturenwill have to make their equipment easier to use for a morediverse work force. Information must be available in anylanguage, and system graphical user interfaces will haveuniversally understood symbols. As economies such as Russiaand China embrace the power and flexibility of UV curing, itwill provide tremendous new opportunities for growing UVcuring, even in market segments tlut currently may be nraturein Europe, Japan or the United States.
Another trend is a worldwide prioritization of cleaning up theenvironment. Just as the United States is cleaning up itsenvironment through stricter legislation and with increasingconsumer demand for "green" products, this "green" trend willmigrate throughout the world. In the next century we are likelyto see more strict environmental requirements in EasternEuropean countries and South America among others. Thisbodes well for the growth of UV curing technology because it is
a clean technologr tlnt can often seamlessly replace a 'dirty"process as customers are faced with stiffer environmentalregulations.
Mass custornization is another major trend that will affect ourcustomers and, as a result, affect us. Mass custornization mearncreating individual solutions on a mass scale irstead ofthe massmarket/mass production concept of the 20th century A goodexample is Dell Computer, which sells millions of personalcomputers, each one customized to the consumer's specifica-tions. We may need to create flexible UV curing systems thatallow customers to quickly and easily change their productionlines daily or even hourly, or perhaps systems that are smallerscale for decentralized/small batch runs.
Finally, as we neartp end of this c€ntury we have transitionedfrom the industrial age to the early stages of the informationage, a trend that will continue to mature far into the nextcentury. Will this result in more Irrternet publications, lessprinted materials and thus less UV-cured printed materials?Perhaps, but don't forget all the unforeseen applications thatmay result because of the information age. Who would havethought about the optical fiber market in the early part of thiscentury, and yet this has become a market dominated by Wcuring. Who would have thought of coatings for cell phoneswhen cell phones didn't exist? W curing likely will enable newproducts to be brought to market in the information age of thecoming millennium.
UV Curing Equipment Trends
Of course, it is always dangerous to forecast the future. In I 98 l,Bill Gates was quoted as saying, '640K ought to be enough foranybody'. At the risk ofputting myself in a similar position, I'lldiscuss some trends and forecast some directions I thinkequipment improvements will take in the next century.
Much like the software industry, where hardware manufacturersneed software that runs on their machines and the softwaremanufacturers need machines that will run their software, UVcuring industry suppliers will need to work jointly to createsuccessfi.rl customer solutions. Formulators cannot sell theirproducts if there is no lamp that will cure their formulation, andlamp manufacturers cannot sell lamps if there is no formulationto cure. A team approach to process design will serve future
35
customer interests and do much to further the growth of UVcuring. Lamp manufacturers working closely with originalequipment manufacturers will ensure an integrated approach tothe process design and more successful applica-tions. In thefuture we'll s€e even more collaboration, strategic alliances andformal agre€ments among suppliers as a way to gain marketdominance, especially in the more mature market segments.
There will be an overall trend to produoe UVaring equipmentthat is easy to use, maintain and operate to meet customerneeds-for example, tool-free changeouts, quick disconnects andreduced preventive maintenance requirements. UV curingequipment will get smaller and larger - smaller so that it can fitinto smaller spa€s in machines and presses, a need of originalequipment manufacturers. We may even se€ portable or hand-held UV curing equipment that is small and lighfweight so itcan be used safely nfree hand' on a shop floor or onjob sites.Larger UV curing systems will be needed for wider web presses,for curing large 3-D parts and for accommodating banks oflamps to increase production speeds. More equipment willincorporate smart controls that free the operator from having toworry about the UV curing system and instead focus on theproduct. For example, remote diagnostics will be tied intoautomatic replacement parts ordering systems and alert users oreven fix problems before they stop production. Eventually,improvements in analytical instrumentation and radiometry willlead to continuous monitoring of cure capabilities and enablebetter diagnostics resulting in higher product quality.
We will continue to see higher-intensity UV light sources withimprovements in maintaining constant output over the life ofthe lamp. There will be an increased use of excimer (nanowband wavelength) that will be synergistic with new families ofphotoinitiators. This is being driven by the need to efftcientlydeliver maximum intensity for faster, deeper curing ofpigmented and white matings. Lamps will be introduced thatare precisely tuned to match the spectral requirements ofphotoinitiators. All of this leads to the design of UV curingsystems that are more ef,ftcient, using an optimized amount oflamps and cure materials to reduce product costs withoutcompromising product quality.
Better heat rnanagement methods will be introduced, perhapsthrough reduced lamp IRoutput befter lamp coolingtechniquesor other new, innovative methods. More sophisticated reflectorsystems will be developed for better cooling, more effrcientlydelivering light intensity without the associated infrared.
Impediments to Overcome
A lack of technical and commercial knowledge of UV curing,especially among end users, is a major impediment to the futuregrowth during the next century. In many market segments, UVcuring is still viewed as an experimental technolog5r, not aproven technology. Through RadTech International No(hAmerica, the UV+uring industry has really pulled together asa team, putting competitive interests aside, to increase
purti'[cdltcltt ccsts
,e* #-
wffiiffigiitENV IRCNTftMAL IFCHl0lOCre' rrvc.I
awareness of the benefits of UV curing. The successfulintroduction of commercial W powder curing applications injust the last year is an excellent example. Many customers arenot always willing to share their successfirl UV curing stories.After all, they have proprietary proc€ss€s that incorporate UVcuring giving them a significant competitive advantage in theirmarkets. When appropriate, we all must find ways to spread theword about successfirl applications, especially in new markets,if we are to grow UV curing in the next century.
Closely tied to this lack of knowledge are misunderstandings orpreconceived notions about UV curing that must be overcome.For example, customers have reported in Ken Lawson's(president, DSM Desotech and past secretary of RadTechInternational North America) surveys that UV coatings havepoor adhesion to a wide range of substrates. While we would allagree that some substrates are more challenging than others, Ithink most of us would also agree that UV curing is beingsuccessfully applied on a widervariety of substrates. Again, thisgets back to the need for industry suppliers to work closelytogether to find proc€ss solutions for customers. With today'shigher molecular weight chemistries and cationic curing, ajointeffort by industry suppliers usually can meet most customers'needs, no rntter what challenges the substrate presents. Withthe right combination of chemistry, UV light intensity andspectrum, many substrates will accept a UV-cured coating withexcellent adhesion.
a
Ukr aV iolet D evices, Inc,UVC Technology
ISO 9001 Certif iedFDA-QSR Compliant Class l l ManufacturerTechnology LeaderConcept Design, Development & ValidationSolid State Power Supply DesignilestCapabil ityProprietary Lamp Fabrication
28220Industry Drive,Valencia California 91 355Phone: (877) PUREUVC
Fax: (661) 295-8350www.uvdi.com
Certain customers occasionally comment that both equipmentand curable products cost too much. Most customers comparethe cost ofchemicals per gallon or the initial purchase price ofthe integrated UV equipment. Again, industry suppliers mustwork jointly to sharc information and create cost models thatfocus customers on the bigger picture that affects their bottomlines: the production cost per unit of product. UV curingtypically increases product throughput rates, reduces labor, floorspace, work in process inventory and energy use. All of theseand other factors that affect production costs must be includedin accurate cost evaluation for W curing. RadTech's LVPowder Coating Focus Group has created such a cost model thatdebuted at the RadTech 2000 conference in April. Additionalcost models will be needed for other applications and markets.It is up to each of us to guide customers we talk to and assistthem in their analysis.
Conclusion
VOCs often remain the driver, with value-added processes thefrequent result. Improved understanding of cure parameters,through better radiometry and tests for "cure,', and strongeralliances with process solution providers will ensure continuedgrowth for UV-curing technolory well into the next century.We must be less enchanted with the technology itself andinstead put more focus on fulfilling customer needs.
FromRadTech Report, Nov/Dec 1999, pp. 16-18,with permission
t . . . : ' ' . . . . .'::: p.o. go;:r ir0, Ayr, oN, Cr*d" Nog igs ,', 'ii"tr s t s-z+ t<zat ; ra* i r s6i z-Ci+ r ; Email : jbotton@iuva. org
1-n early April, 2000, I attended RadTech 2000, the annual
I conference of RadTech International, North America aItraOe organization representing more than 700 companiesinvolved in Ultraviolet (UD and Electron Beam @B) curing ofcoatings and inks. This was an eye{pener for me - I knew thatUV curing existed and that there were several UV companiesproducing equipment for these applications, but I was notprepared to see the scope and maturity of this rapidly growingindu$ry. There were almost 2000 delegates and 122 exhibitorsin a large exhibition including 23 exhibitors who were suppliersof W curing equipment, UV lamps, UV power supplies or UVtesting equipment. This article is not a "conference report" butwill be my attempt to outline the field of UV curing from thestandpoint of an expert in UV Disinfection and AdvancedOxidation Technologies, but certainly not an expert in UVcuring @adTech International North America has published anexcellent *W/EB Curing Primer"t).
UV curing is defined as "tle chemical process of converting a100% solids (iquid) to a high molecular weight polymer
matrix".2
It has been a known proc€ss for a long time @adTech wasestablished over 14 years ago), but only recently has the industryexpanded greatly as a result of environmental concerns withthermally dried solvent based coatings. Also, it has been foundthat UV curing can produce abetter coating with a widervarietyofoptions and degree ofcontrol.
A traditional UV curing operation would involve passing a flat
surface coated with polymer monomer solution containing aphotoinitiator on a transport bed under a bank of UV lamps withreflectors. so that the UV is directed onto the surface of thematerial to be ooated (e.g., wood paneling). Several types of UV
t C. J. Rechtel, Ed., *UV/EB Curing Primer: Inks, Coatingsand Adhesives", RadTech International North America, 3Bethesda Metro Center, Suite 700, Bethesda, MD 20814,1995.2 S. Whittle, "Dwelopments in W Curing Equipment",RadTech Report, Jan/Feb, 2000, 13-15.
reflectors are employed. Figure I shows two of the coillmontypes. The elliptical reflector in Figure la is the more commonq'pe since it can deliver an intense "line" of UV onto themoving coating. In situations where a uniform (and lower)irradiance is desired over a larger area, the parabolic tpe ofcollector (Figure lb) is used.
UV curing applications are expanding rapidly. Almost anysubstrate can be used (paper, wood, metal, leather, vinyl andother plastics, glass, magnetic tape and wen human teeth) ineither 2D or 3D configuration. Application of the UV-sensitivecoating extends through the range of the primitive *dip andwipe" to curtain coater, roll coater, silk screen, printing pressand state-of-the-art nitrogen-assisted airless spray.
Competition has driven wer-improving characteristics of thecured coatings, such as long-term shelfstability, cure stabilityand adhesion to a wide variety of substrates. Products that nowuse UVIEB curing include: varnishes for wood and particle
boards, wall paneling, doors, glass coating for litho-printedpaper, record albums, folding cartons, magazines, papeftackbooks. business forms, bank notes and money bills, vinylflooring/tiles, screen painted bottles, plastic lenses and creditcards. Many printing operations for newspapers, magazinesand book publishing now use "instant dry" UV curing in theprinting line. Many adhesives, such as those for pressuresensitive tapes, labels and decals, automotive parts, potting andencapsulations and jewelry assembly, now use UV/EB curing intheir application. A large section of the Exhibition Floor atRadTech 2000 was devoted to a display ofvarious products thathad used UV/EB in their fabrication. I was amazed at howmany of the products we us€ daily were included.
UV curing almost always employs high-power medium-pressureUV lamps (up to 25 kW). In some cases, the lamps are doped(e.g., with Fe) to modifu the spectral output. Most UV curingequipment uses conventional electrode lamps, but one company(Fusion UV Systems) is making strong inroads with a UVcuring system that employs "electrodeless" W lamps driven bymicrowave generators.
The reflector is a very important part of a UV curing system.The ellipsoidal design provides the highest UV irradiance at thesubstrate surface, but it also focuses the infrared radiation andleads to heating problems on tlre substrate. This problem can bealleviated by either "defocusing" the beam, switching to aparabolic reflector design (see Figure 1) or using one ofthe new"dichroic" reflectors that reflect the UV effrciently, but allowinfrared radiation to be transmitted beyond the reflector. Lineshutdovrns are a reality in the manufacturing process, so somemechanism for quickly turning offthe UV beam on the substratemust be part of the UV curing system. This usually is done byfast action shutters.
The chemistry of the UVcuring process is fascinating (perhapsbecause I am a chemist!). Basically UV light is absorbed by a"sensitizer", which almost always contains one or more doublebonds. This leads to the release of active agents (usually freeradicals or cations) that initiate "cross-linking" (formation ofbonds between polymey' chains), a process that "cures" theformulation by greatly increasing its viscosity (or stifiness). Acomplete formulation for a coating, ink -or adhesive consists ofa mixture of:
. the base plastic (oligomer) that imparts most of the basicproperties to the final cured or cross-linked material;
. monofunctional monomers that dilute the formulations tothe suitable application viscosity;
. multifunctional monomers that help form cross-linksbetween segments of the oligomer;
. specialized adhesives used to impart special properties;
. pigment for inks and some coatings .
. photoinitiators or "sensitizers" that generate free radicalsor cations that initiate the polymerization and formation ofcross-links.
Photoinitiators fall into three classes:
. photocleavage initiators, such as benzoin ethers
'ooR
@8-i-oH
hydrogen-abstraction initiators, such as benzophenone
. cationic initiators, such as triarvlsufonium salts:
ArrS*X
In summary, UV curing is an exciting and rapidly growingapplication of UV technologies. At present, the markets andindustrial bases probably are much larger than those of UVdisinfection of water and wastewater, so IUVA should devotemuch more attention to this UV application.
ot lc
39
\ ,/
llpcoming frleetings
Meetings With IUVA Involvement
2000 Meet ings . . . . """
3d Intl. Symposium on lI/astewater Reclamation' Recycling and
Reuse, Parii, France, 3-7 July 2000' Contact: Ms' Nicole
Couesnon, bgE, Uoin. of Montpellier II, cc057' 34095
Ultrapure l{ater ASIA 2000 Technical Conference , Westin Plaza
Hote! Singapore, October 24, 2000' Caltfor Papers" One-page
abstracts to Ultrapure l{ater Journal, P'O' Box 621669' Litfleton'
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(USA) 22314'1994; Ph: l-8006664206 (US/Canada); all
other; 703 48 4 -24 52; Fx: 703 -684-247 I ; confinfo @w ef 'or g
Wasser Berlin 2000,Betlin Germany, October 23'27'2000 -
IUVA is invited by the IOA (International Ozone Association)
to participate in the technical program' C-ontlct: IUVA' Ayr'
ON,.C"*a" (see p. 3 insert) or IOA, EA3G offrce, 83 Av Foch'
F-75ll6Paris, France, Jsl; +33 I 53 70 13 58; Fax: +33 I 53
'70 13 40: e-mail: IOA-Paris@compuserve'com' See
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. 2001 Meetings .. " " " ..
First International Congre ss on W Technologles' Washington'
DC, June 2001. Dates and location being developed'
Meetings Of Other Organizations
. . . . . . . . . . 2000 Meet ings . . " . . "
American ll'ater Works Assoc', Annual Convention' Denver'
CO, June 11-15, 2000. Contact: AWWA, 6666 West Quincy
Ave., Denver, CO 80235. Tel: 303-794'7711'
Sixth International Conference on Advanced Oxidation
Technologies for l{/ater and Air Remediation and Fifth
Internatiinal bonference on TiO, Photocatalytic Purif cati on
and Treatment of Water and Air, The Hilton Hotel, London'
Ontario, Canada, June 25-30, 1999' Contact: Dr' Hussain Al-
Assoc. of l4/ater Technologies - llater Technologies 2000,Honolulu, HI, 31 Oct - 4 Nov.,2000. Contact: +703610-9012.
AWII/A llrater Qualily Technologt Conference, Salt Lake City,UT, USA, Nov. 5-8,2000. Contact: AWWA, 6666 WestQuincy Ave., Denver, CO 80235. Tel: 303-794-1'111.
Intl. Beverage Industry - InterBev 2000 Exhibition & Congress,New Orleans, LA, USA, Dec. 4{,2000. Contact: +203-E40-5618.
Natl. Ground Water Assoc., 57d Convention & Expo, LasVegas, NV, USA Dec.13-16,2000. Contact: +614-898-7791.
The Bookwoim's,ir coinet
The Effect of Upstream Processes on UVDisinfectionPerformance, published by the Water Environment Federation,1999, 90 pages, soft cover.
The research presented in this report encompasses fourcomponents: l) development of new techniques to analyzewastewater characteristics applicable to UV disinfection, 2)application of those techniques to measure the fundamentalparameters impacting UV disinfection performance, 3) processmodeling, and 4) evaluation of the impact that upstream treatrnentprocess tlpe and operation has on UV disinfection performance.
Table of Contents
1.0 fntroduction
BackgroundProject ObjectivesResearch ApproachOrganization of the Report
2.0 Light Penetration into Wastewater Particles
Light Attenuation Characteristics of Wastewater ParticlesInternal Scattering in Wastewater SolidsAbsorbance of Wastewater SolidsLight Attenuation as a Function of WavelengthLight Penetration into Wastewater ParticlesSummary
3.0 Modeling the Inactivation of Coliform BacteriaAssociated with Particles
Model DevelopmentModeling the Inactivation of Disperse Coliform BacteriaModeling the Inactivation of Particle-Associated Coliform
BacteriaDetermination of the Model ParametersNumber of Particles Associated with Coliform BacteriaInactivation Rate CoeffrcientModel TestingUse of the Model to Predict Coliform Bacteria InactivationApplicability of the Model to Target Organisms Other than
Coliform BacteriaPotential Uses of the Coliform Bacteria Inactivation ModelSummary
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4.0 Upstream Treatment Process Impact on the Formationof Partictes with Associated Coliform Bacteria
Influence of Specific Parameters on Residual Coliform BacteriaConcentration at High UV Doses
Total Suspended Solids ConcentrationInactivation Rate CoefficientNumber of Particles Containing Coliform BacteriaImpact of Floc-Formation on Particles with Associated
Coliform BacteriaImpact of Activated Sludge Process Variations on the Formation
of Particles with Associated Coliform BacteriaImpact of Dilution on the Formation of Particles with'
Associated Coliform BacteriaTrickling Filter Process Impact on the Total Number ofParticles
with Associated Coliform BacteriaInlluence of Particle Size Distribution on the Total Number of
Particles with Associated Coliform BacteriaImpact of Filtration on UV Disinfection PerformanceSummary
5.0 Research Limitations and Future Research Needs
Limitations of this ResearchFuture Research NeedsExperimental TechniquesData Collected at Each Treatment Plant SiteDevelopment of a Flourescent 165 RRNA OligonucleotideProbe Specific to the Family Enterobacteriaceae
References
Order this book (Order No. D930 12ML) from the WERF onlineBookstore: u$rn.wef.ors or call l-800 6664206 (outside theU.S. and Canada, call +l-703584-2452), Fax: +l-703-684-2492. Hcns: WERF Subscribers: $10.00; WEF Members:$55.00; Non-Members: $75.00. All prices subject to shipping,handling and taxes.
Warer Supply 5th Edition
Editors: Alan C. Twort, Formerly consrltant at Binnie, Black& Veatch Consulting Engineers, UK, Don D. Ratnayaka,Malcolm J. Brandt , Both consultants at Binnie, Black & VeatchConsulting Engineer, UK.
Since the previous edition of Water Supply was published in1994, there have been significant changes in the field. Systemshave been updated and redesigned, and new concepts such asdemand management are now commonplace in the watertechnologist's environment.
The new editi on of Water Supply is written by experts from oneofthe top engineering consultancies in the world and covers
up-todate issues in water engineering. International standardsare examined in depth and there is detailed coverage of WHO,UK, European and US standards, organizations and practices. Theauthon adopt a prrctical approach throughout and provide a widesurvey of all the processes involved in procuring, treating anddistributing water.
Contents
Public water supply requirements and its measurementsThe organization and financing of public water suppliesHydrologr and surface supplies, Groundwater suppliesDams, impounding reservoirs and river intakesChemistry, microbiolory and biology of waterStorage, clarification and filtration of waterSpecialized ond advanced wqter bedment processesDkinfedion of water, Hydraulics, Service reservoirsPumping plant: instrumentation, control and automation (ICA)systems, Pipes, pipeline constnrction and valvesPipeline and distribution system design and analysisDistribution practice.
May 2000 800 pages ISBN: 0 340 72018 2 llardbackIWA Members Price: f49.50ruS$80Non Members Price: f66ruS$106
TO ORDER: Contact our Distributor: Portland Press Ltd,commerce way, whitehall Ind Estate, colchester co2 8HP, LIK1sf; +44 (0) 1206 796351; pa{; +44 (0) 1206 799331Email : sales@,portlandoress. com; wurr. uortlandpress. com
IWA Publishing has launched a free email contents alertingservice for all its journals. Visit our website for more informationand to sign up online. To receive information on our newpublications join our mailing list viahttp : //r'wrp. iwarr. co. uk/books/book mailine list. htm
Jo Holman, Marketing Manager, IWA PublishingAlliance House, 12 Caxton Street, London SWIH 0QS, UKEmail: [email protected]; http://www.iwap.co.ukCompany registered in England No. 3690822.
42
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