Assessing ozone disinfection with nonbiological surrogates

Mariñas, Benito J.; Rennecker, Jason L.; Teefy, Susan; Rice, Eugene W.

doi:10.1002/j.1551-8833.1999.tb08699.x

Cited by 11 publications

(13 citation statements)

References 5 publications

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“…Similar to the observation in previous studies (17), preliminary tests revealed that the fluorescence intensity of the microspheres supplied by the manufacturer was too high for optimum simulation of the kinetics of C. parvum oocysts inactivation. A trial-anderror approach revealed that an optimum kinetic match could be achieved by reducing the average microsphere fluorescence intensity by approximately 95%.…”

Section: Methodssupporting

confidence: 76%

Modeling Cryptosporidium parvum Oocyst Inactivation and Bromate Formation in a Full-Scale Ozone Contactor

Tang

Adu-Sarkodie

Kim

et al. 2005

Environ. Sci. Technol.

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The inactivation of Cryptosporidium parvum oocysts and the formation of bromate were assessed simultaneously by performing experiments with a full-scale ozone bubble-diffuser contactor used for drinking water disinfection. Fluorescence-dyed polystyrene microspheres were used as surrogates for C. parvum oocysts. Semi-batch ozonation experiments were performed to determine the fluorescence-intensity decay of individual microspheres, which was measured by flow cytometry. The results obtained with the microspheres were correlated to the inactivation kinetics of C. parvum oocysts by choosing an appropriate threshold fluorescence intensity below which microspheres were considered to be equivalent to nonviable oocysts. A mathematical model was then used to predict the inactivation efficiency and bromate formation. The contactor hydrodynamics were characterized by running tracer tests, and the kinetic parameters for ozone decomposition and bromate formation were obtained by performing batch experiments. Model predictions were in good agreement with full-scale experimental results. Additional model simulations revealed that ozone contactors should be designed with the lowest possible backmixing so that the target inactivation efficiency can be achieved with the lowest possible formation of bromate.

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Section: Methodssupporting

confidence: 76%

Modeling Cryptosporidium parvum Oocyst Inactivation and Bromate Formation in a Full-Scale Ozone Contactor

Tang

Adu-Sarkodie

Kim

et al. 2005

Environ. Sci. Technol.

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“…To investigate this, a novel pilot-scale water distribution system representative of the Stockholm drinking-water distribution system was constructed within the Lovö Waterworks, Sweden. Naturally grown biofilms were exposed to hydrophobic and hydrophilic fluorescent polystyrene microspheres, Salmonella bacteriophage 28B, and Legionella pneumophila bacteria, and their accumulation and persistence in biofilms were measured over a 38-day experimental period.Fluorescent microspheres have been used as surrogate particles in a variety of applications to examine and quantify the accumulation and fate of particulate material within microbial biofilms and are favored for their similarity to bacteria in size and cell surface properties as well as their resistance to biodegradation and disinfection (4,6,10,19,23,24,29). The latter two properties were exploited in this investigation to allow the separation of biological, i.e., loss in culturability, grazing from physical phenomena such as detachment.…”

mentioning

confidence: 99%

“…Fluorescent microspheres have been used as surrogate particles in a variety of applications to examine and quantify the accumulation and fate of particulate material within microbial biofilms and are favored for their similarity to bacteria in size and cell surface properties as well as their resistance to biodegradation and disinfection (4,6,10,19,23,24,29). The latter two properties were exploited in this investigation to allow the separation of biological, i.e., loss in culturability, grazing from physical phenomena such as detachment.…”

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confidence: 99%

Accumulation and Fate of Microorganisms and Microspheres in Biofilms Formed in a Pilot-Scale Water Distribution System

Långmark

Storey

Ashbolt

et al. 2005

Appl Environ Microbiol

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The accumulation and fate of model microbial "pathogens" within a drinking-water distribution system was investigated in naturally grown biofilms formed in a novel pilot-scale water distribution system provided with chlorinated and UV-treated water. Biofilms were exposed to 1-m hydrophilic and hydrophobic microspheres, Salmonella bacteriophages 28B, and Legionella pneumophila bacteria, and their fate was monitored over a 38-day period. The accumulation of model pathogens was generally independent of the biofilm cell density and was shown to be dependent on particle surface properties, where hydrophilic spheres accumulated to a larger extent than hydrophobic ones. A higher accumulation of culturable legionellae was measured in the chlorinated system compared to the UV-treated system with increasing residence time. The fate of spheres and fluorescence in situ hybridization-positive legionellae was similar and independent of the primary disinfectant applied and water residence time. The more rapid loss of culturable legionellae compared to the fluorescence in situ hybridization-positive legionellae was attributed to a loss in culturability rather than physical desorption. Loss of bacteriophage 28B plaque-forming ability together with erosion may have affected their fate within biofilms in the pilot-scale distribution system. The current study has demonstrated that desorption was one of the primary mechanisms affecting the loss of microspheres, legionellae, and bacteriophage from biofilms within a pilot-scale distribution system as well as disinfection and biological grazing. In general, two primary disinfection regimens (chlorination and UV treatment) were not shown to have a measurable impact on the accumulation and fate of model microbial pathogens within a water distribution system. Biofilms are organized in highly efficient and stable ecosystems and play a major role in the sorption of planktonic microorganisms from the bulk water, including indicator bacteria as well as microbial pathogens (3,11,33). Furthermore, distribution pipe biofilms are also implicated in reducing the aesthetic (taste, color, and odor) and microbiological quality of water through the continual detachment of biomass into the bulk water. The importance of biofilm processes, including the attachment, penetration, and detachment of particles, has been recognized in recent years, and a range of studies investigating the fate of model pathogens and indicators such as coliforms (20, 21), legionellae (22), and viruses (27, 32) in a range of model water distribution systems have been undertaken. The limitation of these and similar studies, however, is that they have failed to apportion particle accumulation and loss to biological (i.e., inactivation and predation) and physical (i.e., detachment and disinfection) phenomena.During the current investigation, the effects of two primary disinfection methods, chlorination and UV treatment, on biofilm biomass and the fate of particles within naturally grown biofilms were investigated. The primary disi...

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“…Other variations in parameter values result in increased estimates of health gain. Increasing CCp RAW or reducing the efficiency of CSF result in health benefits up to [8][9][10][11][12] DALYs/mpy (Figure 7 A, B) unboiled water consumption to 1 L/day increases the net health benefit to 3 DALYs/1 mpy. The results are less sensitive to the total water consumption; to reduce the net health gain to 0 would require per capita consumption of 5 L/day.…”

Section: Risk Characterizationmentioning

confidence: 99%

Balancing the risks and benefits of drinking water disinfection: disability adjusted life-years on the scale.

Havelaar

Hollander

Teunis

et al. 2000

Environ Health Perspect

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To evaluate the applicability of disability adjusted life-years (DALYs) as a measure to compare positive and negative health effects of drinking water disinfection, we conducted a case study involving a hypothetical drinking water supply from surface water. This drinking water supply is typical in The Netherlands. We compared the reduction of the risk of infection with Cryptosporidium parvum by ozonation of water to the concomitant increase in risk of renal cell cancer arising from the production of bromate. We applied clinical, epidemiologic, and toxicologic data on morbidity and mortality to calculate the net health benefit in DALYs. We estimated the median risk of infection with C parvum as 10-3/person-year. Ozonation reduces the median risk in the baseline approximately 7-fold, but bromate is produced in a concentration above current guideline levels. However, the health benefits of preventing gastroenteritis in the general population and premature death in patients with acquired immunodeficiency syndrome outweigh health losses by premature death from renal cell cancer by a factor of > 10. The net benefit is approximately 1 DALY/million person-years. The application of DALYs in principle allows us to more explicitly compare the public health risks and benefits of different management options. In practice, the application of DALYs may be hampered by the substantial degree of uncertainty, as is typical for risk assessment. Key work: bromate, Cryptosporidium parvum, disinfection, drinkmg water, ozone, quality of life, risk assessment. Environ Health Perspect 108: 315-321 (2000).[Online 21 February 2000] htp:/lle/hpnetl.nie,hs.nih.gov/docs/2OOO/108p315-321havelaar/abstract.htmIThe microbiologic safety of drinking water is of paramount importance to public health (1). Source protection is generally accepted as the primary strategy to obtain microbiologically safe drinking water. However, many sources (surface waters in particular) are highly polluted and need extensive treatment before distribution to the consumer. Chemical disinfection is prominent in these treatment schemes. Highly oxidizing chemicals such as chlorine and ozone kill a variety of pathogenic microorganisms during treatment, and chlorine is applied in many countries as an additional safeguard in the distribution system. An important drawback of the use of these chemicals is the generation of disinfection by-products, which have suspected adverse effects on human health. This situation calls for a formal quantitative framework to compare the positive and negative health effects of drinking water disinfection and to assist in the design and operation of treatment plants (2).Microbiologic risks are expressed as the annual individual probability of infection for a given consumption of drinking water. Chemical risks related to genotoxic carcinogens are usually associated with an increase in cancer incidence attributable to a lifetime exposure. The public health impact of these disease end points is very different and cannot be compared directly. Hen...

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Assessing ozone disinfection with nonbiological surrogates

Cited by 11 publications

References 5 publications

Modeling Cryptosporidium parvum Oocyst Inactivation and Bromate Formation in a Full-Scale Ozone Contactor

Modeling Cryptosporidium parvum Oocyst Inactivation and Bromate Formation in a Full-Scale Ozone Contactor

Accumulation and Fate of Microorganisms and Microspheres in Biofilms Formed in a Pilot-Scale Water Distribution System

Balancing the risks and benefits of drinking water disinfection: disability adjusted life-years on the scale.

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