Inactivation of Cryptosporidium parvum oocysts using medium- and low-pressure ultraviolet radiation

Creating respiratory pathogen-free environments in healthcare and nursing-care settings: a comprehensive review

Hospital- and nursing-care-acquired infections are a growing problem worldwide, especially during epidemics, posing a significant threat to older adults in geriatric settings. Intense research during the COVID-19 pandemic highlighted the prominent role of aerosol transmission of pathogens. Aerosol particles can easily adsorb different airborne pathogens, carrying them for a long time. Understanding the dynamics of airborne pathogen transmission is essential for controlling the spread of many well-known pathogens, like the influenza virus, and emerging ones like SARS-CoV-2. Particles smaller than 50 to 100 µm remain airborne and significantly contribute to pathogen transmission. This review explores the journey of pathogen-carrying particles from formation in the airways, through airborne travel, to deposition in the lungs. The physicochemical properties of emitted particles depend on health status and emission modes, such as breathing, speaking, singing, coughing, sneezing, playing wind instruments, and medical interventions. After emission, sedimentation and evaporation primarily determine particle fate. Lung deposition of inhaled aerosol particles can be studied through in vivo, in vitro, or in silico methods. We discuss several numerical lung models, such as the Human Respiratory Tract Model, the LUng Dose Evaluation Program software (LUDEP), the Stochastic Lung Model, and the Computational Fluid Dynamics (CFD) techniques, and real-time or post-evaluation methods for detecting and characterizing these particles. Various air purification methods, particularly filtration, are reviewed for their effectiveness in healthcare settings. In the discussion, we analyze how this knowledge can help create environments with reduced PM2.5 and pathogen levels, enhancing safety in healthcare and nursing-care settings. This is particularly crucial for protecting older adults, who are more vulnerable to infections due to weaker immune systems and the higher prevalence of chronic conditions. By implementing effective airborne pathogen control measures, we can significantly improve health outcomes in geriatric settings.

Occurrence, transmission and risks assessment of pathogens in aquatic environments accessible to humans

Pathogens are ubiquitously detected in various natural and engineered water systems, posing potential threats to public health. However, it remains unclear which human-accessible waters are hotspots for pathogens, how pathogens transmit to these waters, and what level of health risk associated with pathogens in these environments. This review collaboratively focuses and summarizes the contamination levels of pathogens on the 5 water systems accessible to humans (natural water, drinking water, recreational water, wastewater, and reclaimed water). Then, we showcase the pathways, influencing factors and simulation models of pathogens transmission and survival. Further, we compare the health risk levels of various pathogens through Quantitative Microbial Risk Assessment (QMRA), and assess the limitations of water-associated QMRA application. Pathogen levels in wastewater are consistently higher than in other water systems, with no significant variation for Cryptosporidium spp. among five water systems. Hydraulic conditions primarily govern the transmission of pathogens into human-accessible waters, while environmental factors such as temperature impact pathogens survival. The median and mean values of computed public health risk levels posed by pathogens consistently surpass safety thresholds, particularly in the context of recreational waters. Despite the highest pathogens levels found in wastewater, the calculated health risk is significantly lower than in other water systems. Except pathogens concentration, variables like the exposure mode, extent, and frequency are also crucial factors influencing the public health risk in water systems. This review shares valuable insights to the more accurate assessment and comprehensive management of public health risk in human-accessible water environments.

Molecular ecological networks reveal the spatial-temporal variation of microbial communities in drinking water distribution systems

Microbial activity and regrowth in drinking water distribution systems is a major concern for water service companies. However, previous studies have focused on the microbial composition and diversity of the drinking water distribution systems (DWDSs), with little discussion on microbial molecular ecological networks (MENs) in different water supply networks. MEN analysis explores the potential microbial interaction and the impact of environmental stress, to explain the characteristics of microbial community structures. In this study, the random matrix theory-based network analysis was employed to investigate the impact of seasonal variation including water source switching on the networks of three DWDSs that used different disinfection methods. The results showed that microbial interaction varied slightly with the seasons but was significantly influenced by different DWDSs. Proteobacteria, identified as key species, play an important role in the network. Combined UV-chlorine disinfection can effectively reduce the size and complexity of the network compared to chlorine disinfection alone, ignoring seasonal variations, which may affect microbial activity or control microbial regrowth in DWDSs. This study provides new insights for analyzing the dynamics of microbial interactions in DWDSs.

The Effectiveness of Far-Ultraviolet (UVC) Light Prototype Devices with Different Wavelengths on Disinfecting SARS-CoV-2

Coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has emerged as a serious threat to human health worldwide. The inactivation of SARS-CoV-2 on object surfaces and in the indoor air might help to halt the COVID-19 pandemic. Far-ultraviolet light (UVC) disinfection has been proven to be highly effective against viruses and bacteria. To understand the wavelength and duration of UVC radiation required for SARS-CoV-2 inactivation, we examined the efficacy of UVC light prototype devices with the wavelengths of 275, 254, and 222 nm. The disinfection effectiveness was determined by cell-based assays including the median tissue culture infectious dose (TCID50) and an immunofluorescent assay on African green monkey kidney epithelial Vero E6 cells. Among the three prototypes, the UVC LED (275 nm) had the best virucidal activity with a log-reduction value (LRV) >6 after 10 s of exposure. The mercury lamp (254 nm) reached similar virucidal activity after 20 s of exposure. However, the excimer lamp (222 nm) showed limited anti-SARS-CoV-2 activity with a LRV < 2 after 40 s of exposure. Overall, in comparison, the UVC LED (275 nm) exhibited superior SARS-CoV-2 disinfection activity than the mercury lamp (254 nm) and the excimer lamp (222 nm).

A Critical Review on Ultraviolet Disinfection Systems against COVID-19 Outbreak: Applicability, Validation, and Safety Considerations

The global health-threatening crisis from the COVID-19 pandemic, caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), highlights the scientific and engineering potentials of applying ultraviolet (UV) disinfection technologies for biocontaminated air and surfaces as the major media for disease transmission. Nowadays, various environmental public settings worldwide, from hospitals and health care facilities to shopping malls and airports, are considering implementation of UV disinfection devices for disinfection of frequently touched surfaces and circulating air streams. Moreover, the general public utilizes UV sterilization devices for various surfaces, from doorknobs and keypads to personal protective equipment, or air purification devices with an integrated UV disinfection technology. However, limited understanding of critical UV disinfection aspects can lead to improper use of this promising technology. In this work, fundamentals of UV disinfection phenomena are addressed; furthermore, the essential parameters and protocols to guarantee the efficacy of the UV sterilization process in a human-safe manner are systematically elaborated. In addition, the latest updates from the open literature on UV dose requirements for incremental log removal of SARS-CoV-2 are reviewed remarking the advancements and existing knowledge gaps. This study, along with the provided illustrations, will play an essential role in the design and fabrication of effective, reliable, and safe UV disinfection systems applicable to preventing viral contagion in the current COVID-19 pandemic, as well as potential future epidemics.

Hydroxyl radical scavenging factor measurement using a fluorescence excitation-emission matrix and parallel factor analysis in ultraviolet advanced oxidation processes

The performance of the UV/H₂O₂ advanced oxidation process (AOP) is dependent on water quality parameters, including the UV absorbance coefficient at 254 nm and hydroxyl radical (•OH) water background demand (scavenging factor, s^-1). The •OH scavenging factor represents the •OH scavenging rate of the background substances in the water matrix, and it is known to be one of the key parameters to predict the performance of the UV/H₂O₂ process. The •OH scavenging factor has been determined experimentally by using a probe compound such as pCBA and rhodamine B. The experimental method has been validated to accurately predict the micropollutants removal in the UV/H₂O₂ process, but there is a need for an easier and simple method of determining the OH scavenging factor. We evaluated the alternative method to analyze the •OH scavenging factor using fluorescence excitation-emission matrix and parallel factor analysis (F-EEM/PARAFAC). The correlation between •OH scavenging factor and the spectroscopic characteristics and structure of different organic matter types was evaluated. Organic matter was characterized using a fluorescence excitation-emission matrix, parallel factor analysis, and liquid chromatography-organic carbon detection. Second-order reaction rates of humic acid sodium salt, sodium alginate, Suwannee River humic acid and bovine serum albumin were calculated as 1.30 × 10⁸ M^-1 s^-1, 1.39 × 10⁸ M^-1 s^-1, 1.03 × 10⁸ M^-1 s^-1, and 3.17 × 10⁷ M^-1 s^-1, respectively. Results of PARAFAC analysis, the ratio of humic and fulvic fluorescence component 2 to terrestrial humic-like fluorescence component 1 (C2/C1), and •OH scavenging factor showed high linearity. A predictive model, which combines with the F-EEM/PARAFAC method, predicted the optimal UV and H₂O₂ dose to achieve target compound removal.

Disinfection characteristics of Pseudomonas peli, a chlorine-resistant bacterium isolated from a water supply network

Lack of microbial contamination is crucial for drinking water quality and safety. Chlorine-resistant bacteria in drinking water distribution systems pose a threat to drinking water quality. A bacterium was isolated from an urban water supply network in northern China and identified as Pseudomonas peli by 16S rDNA gene analysis. This P. peli strain had high chlorine tolerance. The CT value (the product of disinfectant concentration and contact time) to achieve 3 lg unit (i.e. 99.9%)-inactivation of this P. peli isolate was 51.26-90.36 mg min/L, inversely proportional to the free chlorine concentration. Chlorine dioxide could inactivate the bacterium faster and more efficiently than free chlorine, as shown by flow cytometry. Thiazole orange plus propidium iodide staining indicated that free chlorine and chlorine dioxide inactivated P. peli primarily by disrupting the integrity and permeability of the cell membrane. The P. peli was also sensitive to ultraviolet (UV) radiation; a UV dose of 40 mJ/cm² achieved 4 lg unit (99.99%)-inactivation. The Hom model was more suitable for analyzing the disinfection kinetics of P. peli than the Chick and Chick-Watson models.

Efficacy of ultraviolet light-emitting diodes (UV-LED) at four different peak wavelengths against Cryptosporidium parvum oocysts by inactivation assay using immunodeficient mice

As an alternative to using ultraviolet (UV) lamps, which are made with mercury that is toxic to the environment and human health, UV light-emitting diodes (UV-LEDs) are expected to be effective for inactivating microorganisms in water. Although UV-LEDs have been reported to be effective against bacteria and viruses, the effectiveness of UV-LEDs against Cryptosporidium parasites has not been fully evaluated. As we report here, we have developed an in vivo quantitative inactivation assay for C. parvum oocysts using immunodeficient mice. Using the assay, we evaluated the effectiveness of treatment by UV lamp (254 nm) at approximately 1000 μJ/cm² (for 3 s at a distance of 95 mm) compared to inactivation by commercially available UV-LEDs (with peak wavelengths of 268, 275, 284, and 289 nm). The shed patterns of oocysts after treatment with 284- and 289-nm wavelength UV-LEDs were significantly delayed compared to that after treatment with a UV lamp. These findings provide the first suggestion that UV-LEDs are effective against these parasites, as assessed using commercially available 350-mA UV-LEDs under conditions of fixed exposure distance and time.

Investigation of chlorine tolerance profile of dominant gram negative bacteria recovered from secondary treated wastewater in Jaipur, India

Management of bacterial survival post chlorine disinfection is vital for safe wastewater reuse for irrigation, as the presence of microorganisms in large numbers may lead to subsequent contamination of the surface and ground water reservoirs. Even after satisfying the current norms of coliform counts after disinfection (less than 1000 MPN per 100 mL), chlorine tolerant bacteria surviving in inadequately treated wastewater may pose a public health threat as many of these bacteria are able to re-grow upon storage. The current study is aimed to assess the magnitude of the problem posed by chlorine tolerant bacteria during chlorine disinfection and attempts to derive a strategy for safe disinfection. The chlorine tolerance was examined in the dominant gram negative bacteria (GNB) recovered from secondary treated sewage from a treatment plant located at Jaipur, India. Bacterial survival and re-growth (after 24 h) studies on test species (n = 11) with reference to E.coli ATCC 25922 reveal that, while the lethal doses of isolates ranged from 0.5 to 1.25 mgL^-1,the chlorine doses for complete inhibition of re-growth were much higher (0.75-1.75 mgL^-1).The isolates showing highest lethal dose and re-growth inhibition dose, identified as Citrobacter freundii, Klebsiella sp. and Stenotrophomonas maltophilia also exhibited very low log effective reduction (0.72-1.90) values and were selected as chlorine tolerant bacteria. Results of inactivation kinetics experiments on chlorine tolerant bacteria reveal a strong correlation (R² > 0.89-0.99) between log reduction values and contact time. In re-growth kinetics experiments, maximum re-growth was observed after 6 h exposure following which, only marginal increase was registered up to 24 h. The study indicates that the existing approach of bacterial elimination post chlorine treatment may be grossly inadequate to assess the performance of the disinfection process adopted for drinking water treatment. It further brings out a novel approach to arrive at meaningful chlorine doses that take bacterial re-growth into account for achieving safe disinfection.

Optimizing the performance of conventional water treatment system using quantitative microbial risk assessment, Tehran, Iran

The performance of conventional drinking water treatment plants (WTPs) can be improved using quantitative microbial risk assessment (QMRA). A QMRA study on Cryptosporidium using actual pathogen density was conducted to examine the performance of Jalaliyeh WTP in Tehran, Iran. The infection risk and the burden of disease attributed to the parasite presence in finished water were estimated incorporating physical and chemical log reduction values (LRVs), using stochastic modeling and disinfection profiling. The risk and burden of disease were compared with health-based targets, i.e. one case of infection per 10,000 people or 10^-6 DALYs per person per year. The parasite's LRVs were 2.31 and 0.034 log provided by physico-chemical treatment and disinfection processes, respectively. The mean of estimated risk (111 cases per 10⁴ people per year) and the burden of disease (11.7 DALYs per 10⁶ people per year) both exceeded the targets. To control the excess risk, three QMRA-based disinfection scenarios were examined including: (1) employing chlorine dioxide (ClO₂) instead of chlorine (2) ozonation with a concentration of 0.75 mg/L (Ct = 22.5 min mg/L) and (3) UV irradiation with a dose of 10 mJ/cm². The LRV of parasite may be increased to 3.0, 5.1 and 4.9 log by employing ClO₂, ozonation and UV irradiation, respectively. The use of ozone or UV as alternative disinfectants, could enhance the disinfection efficacy and provide sufficient additional treatment against the excess risk of parasite. QMRA could make it easier applying appropriate improvement to conventional WTPs in order to increase the system performance in terms of health-based measures.

Instantaneous Water Purification by Deep Ultraviolet Light in Water Waveguide: Escherichia Coli Bacteria Disinfection

The necessity of small water purification equipment has been increasing in recent years as a result of frequent natural disasters. Ultraviolet (UV) radiation treatment is an effective method for the disinfection of bacterial contaminants in water. As an emerging technology, disinfection by deep-ultraviolet light-emitting diodes (DUV-LEDs) is promising. Few studies have used the point-source characteristics of LEDs and have instead replaced mercury vapor lamps with LEDs. Here, we demonstrate the instantaneous purification of contaminated water by combining the point source characteristics of DUV-LEDs with a water waveguide (WW). The principle is based on the WW region acting as an effective DUV disinfector, whereby a high UV dose in a confined WW region can be applied to bacterial contaminants in a short period of time (around one second). We demonstrate the effect of this DUV-LED WW disinfection technique by showing the results of 3-log disinfection levels of water contaminated with Escherichia coli bacteria after a short treatment time. We believe that the combination of the point-source nature of DUV-LED emission, the water-waveguide effect, and a small photovoltaic cell paves the way toward environmentally friendly and emergency preparedness portable water purification equipment that instantaneously supplies clean water just before drinking.

Application of UVOX Redox® for swimming pool water treatment: Microbial inactivation, disinfection byproduct formation and micropollutant removal

Alternative disinfection technologies may overcome some of the limitations of conventional treatment applied in swimming pools: chlorine-resistant pathogens (e.g. Cryptosporidium oocysts and Giardia cysts) and the formation of chlorinated disinfection byproducts. In this paper, results of full scale validation of an alternative disinfection technology UVOX Redox^® (hereinafter referred to as UVOX) that combines ozonation and UV irradiation are presented. The performance was assessed in terms of microbial inactivation, disinfection byproduct formation and micropollutant removal. UVOX was able to achieve 1.4-2.7 log inactivation of Bacillus subtilis spores at water flows between 20 and 76 m³/h. Lower formation of trichloromethane and dichloroacetic acid was observed with UVOX followed by chlorination when compared to chlorination alone. However, due to the use of ozone and the presence of bromide in the pool water, the formation of trihalomethanes and haloacetic acids shifted to more brominated byproducts. Chlorine alone was able to remove the target micropollutants: acetaminophen, atenolol, caffeine, carbamazepine, estrone, estradiol, and venlafaxine (>97% removal) after 24 h, with the exception of ibuprofen (60% removal). The application of UVOX in chlorinated water enhanced the removal of ibuprofen. The application of UVOX could lower the usage of chlorine to the level that provides an adequate residual disinfection effect.

Effect of sequential UV/free chlorine disinfection on opportunistic pathogens and microbial community structure in simulated drinking water distribution systems

Drinking water distribution systems (DWDS) may be a "Trojan Horse" for some waterborne diseases caused by opportunistic pathogens (OPs). In this study, two simulated DWDS inoculated with groundwater were treated with chlorine (Cl₂) and ultraviolet/chlorine (UV/Cl₂) respectively to compare their effects on the OPs distributed in four different phases (bulk water, biofilms, corrosion products, and loose deposits) of DWDS. 16S rRNA genes sequencing and qPCR were used to profile microbial community and quantify target genes of OPs, respectively. Results showed that UV/Cl₂ was more effective than single Cl₂ to control the regrowth of OPs in the water with the same residual chlorine concentration. However, the OPs inhabiting the biofilms, corrosion products, and loose deposits seemed to be tolerant to UV/Cl₂ and Cl₂, demonstrating that OPs residing in these phases were resistant to the disinfection processes. Some significant microbial correlations between OPs and Acanthamoeba were found by Spearman correlative analysis (p < 0.05), demonstrating that the ecological interactions may exist in the DWDS. 16S rRNA genes sequencing of water samples revealed a significant different microbial community structure between UV/Cl₂ and Cl₂. This study may give some implications for controlling the OPs in the DWDS disinfected with UV/Cl₂.

Recreational Use of Spa Thermal Waters: Criticisms and Perspectives for Innovative Treatments

Natural spa springs are diffused all over the world and their use in pools is known since ancient times. This review underlines the cultural and social spa context focusing on hygiene issues, public health guidelines and emerging concerns regarding water management in wellness or recreational settings. The question of the "untouchability" of therapeutic natural waters and their incompatibility with traditional disinfection processes is addressed considering the demand for effective treatments that would respect the natural properties. Available strategies and innovative treatments are reviewed, highlighting potentials and limits for a sustainable management. Alternative approaches comprise nanotechnologies, photocatalysis systems, advanced filtration. State of the art and promising perspectives are reported considering the chemical-physical component and the biological natural complexity of the spa water microbiota.

Cryptosporidium and Giardia in Wastewater and Surface Water Environments

and spp. are significant contributors to the global waterborne disease burden. Waterways used as sources of drinking water and for recreational activity can become contaminated through the introduction of fecal materials derived from humans and animals. Multiple studies have reported the occurence or concentrations of these pathogens in the environment. However, this information has not been comprehensively reviewed. Quantitative microbial risk assessment (QMRA) for and can be beneficial, but it often relies on the concentrations in environmental sources reported from the literature. A thorough literature review was conducted to develop an inventory of reported and concentrations in wastewater and surface water available in the literature. This information can be used to develop QMRA inputs. and (oo)cyst concentrations in untreated wastewater were up to 60,000 oocysts L and 100,000 cysts L, respectively. The maximum reported concentrations for and in surface water were 8400 oocysts L and 1000 cysts L, respectively. A summary of the factors for interpretation of concentration information including common quantification methods, survival and persistence, biofilm interactions, genotyping, and treatment removal is provided in this review. This information can help in identifying assumptions implicit in various QMRA parameters, thus providing the context and rationale to guide model formulation and application. Additionally, it can provide valuable information for water quality practitioners striving to meet the recreational water quality or treatment criteria. The goal is for the information provided in the current review to aid in developing source water protection and monitoring strategies that will minimize public health risks.

Photocatalytic Inactivation of Enterobacter cloacae and Escherichia coli Using Titanium Dioxide Supported on Two Substrates

The antibacterial photocatalytic activity of TiO2 supported over two types of substrates, borosilicate glass tubes (TiO2/SiO2-borosilicate glass tubes (BGT)) and low-density polyethylene pellets (TiO2-LDPE pellets), which were placed in a compound parabolic collectors (CPC) reactor, was evaluated against Enterobacter cloacae and Escherichia coli under sunlight. Three solar photocatalytic systems were assessed, suspended TiO2, TiO2/SiO2-BGT and TiO2-LDPE pellets, at three initial bacterial concentrations, 1 × 105; 1 × 103; 1 × 101 CFU/mL of E. coli and total bacteria (E. cloacae and E. coli). The solar photo-inactivation of E. coli was achieved after two hours with 7.2 kJ/L of UV-A, while total bacteria required four hours and 16.5 kJ/L of UV-A. Inactivation order of E. coli was determined, as follows, suspended TiO2/sunlight (50 mg/L) > TiO2-LDPE pellets/sunlight (52 mg/L) > TiO2/SiO2-BGT/sunlight (59 mg/L), the best E. coli. inactivation rate was obtained with TiO2-LDPE pellets/sunlight, within 4.5 kJ/L and 90 min. The highest total bacteria inactivation rate was found for TiO2/sunlight (50 mg/L) and TiO2-LDPE pellets/sunlight (52 mg/L), within 11.2 kJ/L and 180 min. TiO2 deposited over LDPE pellets was the most effective material, which can be successfully used for water disinfection applications. Bacterial regrowth was assessed 24 h after all photocatalytic treatments, none of those microorganisms showed any recovery above the detection limit (2 CFU/mL).

The Biological Basis for Ballast Water Performance Standards: "Viable/Non-Viable" or "Live/Dead"?

The shipping industry is critical to international commerce; however, contemporary shipping practices involve uptake and discharge of ballast water, which introduces the potential for transfer of nonindigenous, invasive species among geographically distinct habitats. To counteract this hazard, regulations for ballast water management have been implemented by the International Maritime Organization (IMO) and by regulatory agencies such as the United States Coast Guard (USCG). IMO and USCG discharge standards are numerically identical, but involve different definitions of treatment end points, which are based on fundamentally different biological assays for quantification of ballast water treatment effectiveness. Available assays for quantification of the responses of organisms in the 10-50 μm size range include vital stains based on fluorescein diacetate (FDA), sometimes used in combination with 5-chloromethylfluorescein diacetate (CMFDA), observations of motility, and the most probable number dilution culture method (MPN). The mechanisms and implications of these assays are discussed relative to the Type Approval process, which quantitatively evaluates compliance with ballast water discharge standards (BWDSs) under controlled shipboard and land-based tests. For antimicrobial processes that accomplish treatment by preventing subsequent replication of the target species, the FDA/CMFDA and MPN methods can yield dramatically different results. An important example of a treatment process that is affected by the choice of assay is ultraviolet (UV) irradiation. Results of laboratory and field experiments have demonstrated UV-based technologies to be effective for accomplishing the objectives of ballast water treatment (inactivation of cellular reproduction), when the MPN assay is used as the basis for evaluation. The FDA, CMFDA, motility, and MPN methods are subject to well recognized sources of error; however, the MPN method is based on a response that is consistent with the objectives of ballast water management as well as the mechanism of action of UV-based inactivation. Complementary assays are available for use in compliance testing; however, the development of relevant indicative tests remains as a research priority. Historical lessons learned from applications of vital stains (and other indirect methods) for quantification of microbial responses to UV irradiation in other settings also support the use of assays that provide a direct measure of growth and reproduction, such as MPN. Collectively, these observations point to the use of MPN assays as the standard for type testing, especially when UV-based treatment is employed.

Usefulness of Sunlight and Artificial UV Radiation Versus Chlorine for the Inactivation of Cryptosporidium Oocysts: An in Vivo Animal Study

BACKGROUND

Cryptosporidium is an important waterborne protozoan.

AIM

The aim of this study was to investigate the effect of sunlight being the natural source of UV and artificial UV irradiation on Cryptosporidium oocysts versus the effect of chlorination, being the traditional method of water disinfection and to provide an insight into the viability and degree of infectivity of Cryptosporidium oocysts, using an animal model.

METHODS

An experimental study including 300 neonatal mice was carried out to investigate the effect of artificial ultraviolet (UV) irradiation and sunlight being the natural source of UV irradiation versus chlorine, the traditionally used water disinfectant on the infectivity of Cryptosporidium oocysts present in water. For each item, nine different exposure times were investigated. Parasitological assessment (Modified Ziehl Neelsen stained stool smears) and histopathological assessment of the excised segments of the small intestine (stained by both Haematoxylin & Eosin and ZN stain) of mice were used to verify the inactivation of oocysts.

RESULTS

Cryptosporidium oocysts failed to induce any noticeable infection after 4 hours of artificial UV exposure that provided a UV dose of 10mJ/cm2 and after an 8 hours exposure to sunlight, whereas they showed resistance to disinfection by chlorine.

CONCLUSION

The results of the study demonstrate the important role of an 8 hours sunlight exposure of potable water in plastic bottles in achieving complete inactivation of any contaminating Cryptosporidium oocysts, thus offering an applicable, economical and convenient method for the control of cryptosporidiosis especially in developing countries.

Assessing viability and infectivity of foodborne and waterborne stages (cysts/oocysts) of Giardia duodenalis, Cryptosporidium spp., and Toxoplasma gondii: a review of methods

Giardia duodenalis, Cryptosporidium spp. and Toxoplasma gondii are protozoan parasites that have been highlighted as emerging foodborne pathogens by the Food and Agriculture Organization of the United Nations and the World Health Organization. According to the European Food Safety Authority, 4786 foodborne and waterborne outbreaks were reported in Europe in 2016, of which 0.4% were attributed to parasites including Cryptosporidium, Giardia and Trichinella. Until 2016, no standardized methods were available to detect Giardia, Cryptosporidium and Toxoplasma (oo)cysts in food. Therefore, no regulation exists regarding these biohazards. Nevertheless, considering their low infective dose, ingestion of foodstuffs contaminated by low quantities of these three parasites can lead to human infection. To evaluate the risk of protozoan parasites in food, efforts must be made towards exposure assessment to estimate the contamination along the food chain, from raw products to consumers. This requires determining: (i) the occurrence of infective protozoan (oo)cysts in foods, and (ii) the efficacy of control measures to eliminate this contamination. In order to conduct such assessments, methods for identification of viable (i.e. live) and infective parasites are required. This review describes the methods currently available to evaluate infectivity and viability of G. duodenalis cysts, Cryptosporidium spp. and T. gondii oocysts, and their potential for application in exposure assessment to determine the presence of the infective protozoa and/or to characterize the efficacy of control measures. Advantages and limits of each method are highlighted and an analytical strategy is proposed to assess exposure to these protozoa.

UV-induced effects on toxicity of model disinfection byproducts

UV (Ultraviolet)-based treatment has been demonstrated to be effective for removal of some disinfection byproducts (DBPs) and to be beneficial for reduction of genotoxicity and cytotoxicity in chlorinated water. However, to a large extent, UV-induced effects on chemistry and toxicology have been treated as a black box, in the sense that little or no UV dose-dependent behavior has been reported. To address this issue, the effects of UV₂₅₄ irradiation on 1,4-dibenzoquinone (BQ), 2,6-dichloro-1,4-benzoquinone (DCBQ), and chlorocreatinine (Cl-Cre) as model DBPs were examined, both in terms of photodegradation and cytotoxicity. These compounds have been identified as DBPs that are relevant in swimming pool settings; however, these compounds will be relevant in other water treatment settings, including drinking water production and wastewater reuse. UV₂₅₄ irradiation was shown to promote photodecay of all three compounds. However, for BQ and DCBQ, the corresponding cytotoxicity of the UV-irradiated samples remained essentially unchanged, even when the compound was completely photodegraded. These results indicate that the photodegradation products of BQ and DCBQ carry similar cytotoxicity as their respective parent compounds. On the other hand, UV₂₅₄-irradiation of Cl-Cre yielded a decrease in cytotoxicity that correlated with photodechlorination of Cl-Cre. These experiments also demonstrated a reduction in cytotoxicity in connection with photodechlorination of an N-chlorinated organic compound. Overall, the results of these experiments indicate the importance of defining products of UV photodecay processes, both in terms of chemistry and toxicity; these attributes are expected to be important in many UV-based applications, including potable water production, water reuse, and recreational water settings.

Drivers of Microbial Risk for Direct Potable Reuse and de Facto Reuse Treatment Schemes: The Impacts of Source Water Quality and Blending

Although reclaimed water for potable applications has many potential benefits, it poses concerns for chemical and microbial risks to consumers. We present a quantitative microbial risk assessment (QMRA) Monte Carlo framework to compare a de facto water reuse scenario (treated wastewater-impacted surface water) with four hypothetical Direct Potable Reuse (DPR) scenarios for Norovirus, Cryptosporidium, and Salmonella. Consumer microbial risks of surface source water quality (impacted by 0-100% treated wastewater effluent) were assessed. Additionally, we assessed risks for different blending ratios (0-100% surface water blended into advanced-treated DPR water) when source surface water consisted of 50% wastewater effluent. De facto reuse risks exceeded the yearly 10-4 infections risk benchmark while all modeled DPR risks were significantly lower. Contamination with 1% or more wastewater effluent in the source water, and blending 1% or more wastewater-impacted surface water into the advanced-treated DPR water drove the risk closer to the 10-4 benchmark. We demonstrate that de facto reuse by itself, or as an input into DPR, drives microbial risks more so than the advanced-treated DPR water. When applied using location-specific inputs, this framework can contribute to project design and public awareness campaigns to build legitimacy for DPR.

Cryptosporidium Attenuation across the Wastewater Treatment Train: Recycled Water Fit for Purpose

Compliance with guideline removal targets for Cryptosporidium which do not provide any credit for the inactivation of oocysts through wastewater treatment processes can considerably increase the cost of providing recycled water. Here we present the application of an integrated assay to quantify both oocyst numbers and infectivity levels after various treatment stages at three Victorian and two South Australian (SA) wastewater treatment plants (WWTPs). Oocyst density in the raw sewage was commensurate with community disease burden, with early rounds of sampling capturing a widespread cryptosporidiosis outbreak in Victoria. The level of infectivity of oocysts in sewage was stable throughout the year but was significantly lower at the SA WWTPs. Removals across secondary treatment processes were seasonal, with poorer removals associated with inflow variability; however, no decrease in the oocyst infectivity was identified. For SA WWTPs, those oocysts remaining within the secondary treatment-clarified effluent were proportionally more infectious than those in raw sewage. Lagoon systems demonstrated significant inactivation or removal of oocysts, with attenuation being seasonal. Examination of a UV system emphasized its efficacy as a disinfectant barrier but conversely confirmed the importance of a multibarrier approach with the detection of infectious oocysts postdisinfection. The ability to characterize risk from infectious oocysts revealed that the risk from Cryptosporidium is significantly lower than previously thought and that its inclusion in quantitative risk assessments of reuse systems will more accurately direct the selection of treatment strategies and capital expenditure, influencing the sustainability of such schemes.IMPORTANCE Here we present the application of a recently developed integrated assay not only to quantify the removal of Cryptosporidium oocysts but also to quantify their infectivity across various treatment stages at five wastewater treatment plants (WWTPs), thereby better measuring the "true effect" of the treatment train on oocyst risk reduction. For a number of the WWTPs analyzed in this study the risk, is significantly lower than previously thought. Therefore, the inclusion of oocyst infectivity in guideline values and in quantitative microbial risk assessment (QMRA) has the potential to affect future treatment directions and capital expenditure.

UV Disinfection of Wastewater and Combined Sewer Overflows

Municipal wastewater contains bacteria, viruses, and other pathogens that adversely affect the environment, human health, and economic activity. One way to mitigate these effects is a final disinfection step using ultraviolet light (UVL). The advantages of UVL disinfection, when compared to the more traditional chlorine, include no chlorinated by-products, no chemical residual, and relatively compact size. The design of most UV reactors is complex. It involves lamp selection, power supply design, optics, and hydraulics. In general, medium pressure lamps are more compact, powerful, and emit over a wider range of light than the more traditional low pressure lamps. Low pressure lamps, however, may be electrically more efficient. In UV disinfection, the fraction of surviving organisms (e.g. E. coli) will decrease exponentially with increasing UV dose. However, the level of disinfection that can be achieved is often limited by particle-associated organisms. Efforts to remove or reduce the effects of wastewater particles will often improve UV disinfection effectiveness. Regrowth, photoreactivation, or dark repair after UV exposure are sometimes cited as disadvantages of UV disinfection. Research is continuing in this area, however there is little evidence that human pathogens can photoreactivate in environmental conditions, at doses used in wastewater treatment. The UV disinfection of combined sewer overflows, a form of wet weather pollution, is challenging and remains largely at the research phase. Pre-treatment of combined sewer overflows (CSOs) with a cationic polymer to induce fast settling, and a low dose of alum to increase UV transmittance, has shown promise at the bench scale.

Degradation of DEET and Caffeine under UV/Chlorine and Simulated Sunlight/Chlorine Conditions

Photoactivation of aqueous chlorine could promote degradation of chlorine-resistant and photochemically stable chemicals accumulated in swimming pools. This study investigated the degradation of two such chemicals, N,N-diethyl-3-methylbenzamide (DEET) and caffeine, by low pressure ultraviolet (UV) light and simulated sunlight (SS) activated free chlorine (FC) in different water matrices. Both DEET and caffeine were rapidly degraded by UV/FC and SS/FC but exhibited different kinetic behaviors. The degradation of DEET followed pseudo-first-order kinetics, whereas the degradation of caffeine accelerated with reaction. Mechanistic study revealed that, under UV/FC, ·OH and Cl· were responsible for degradation of DEET, whereas ClO· related reactive species (ClOrrs), generated by the reaction between FC and ·OH/Cl·, played a major role in addition to ·OH and Cl· in degrading caffeine. Reaction rate constants of DEET and caffeine with the respective radical species were estimated. The imidazole moiety of caffeine was critical for the special reactivity with ClOrrs. Water matrix such as pH had a stronger impact on the UV/FC process than the SS/FC process. In saltwater matrix under UV/FC and SS/FC, the degradation of DEET was significantly inhibited, but the degradation of caffeine was much faster than that in nonsalty solutions. The interaction between Br^- and Cl^- may play an important role in the degradation of caffeine by UV/FC in saltwater. Reaction product analysis showed similar product patterns by UV/FC and SS/FC and minimal formation of chlorinated intermediates and disinfection byproducts.

Effects of UV-based treatment on volatile disinfection byproducts in a chlorinated, indoor swimming pool

Ultraviolet (UV) irradiation and chlorination are commonly used together in treatment of swimming pool water because they function as complementary disinfectants and because UV-based processes have been shown to promote photodecay of chloramines. However, UV-based treatment also has the potential to promote formation of some disinfection byproducts (DBPs). As a result, the overall effects of UV irradiation with chlorination on swimming pool chemistry remain unclear. To address this issue, a three-year study was conducted in a chlorinated, indoor swimming pool under three different operating conditions: conventional chlorination (1st year) which served as a control, chlorination augmented by MP UV irradiation (2nd year), and chlorination augmented by LP UV irradiation (3rd year). Water samples were collected from the pool for measurement of pH, temperature, total alkalinity, free and combined chlorine, eleven volatile DBPs, and urea concentration. After installation of MP UV, the concentrations of most volatile DBPs decreased; similar effects were observed after inclusion of LP UV. Collectively, these results imply an overall improvement in water quality as a result of the inclusion of the both UV systems. In general, MP UV was more efficient than LP UV for reducing the concentrations of most of the volatile DBPs measured in this pool. However, a need exists to standardize the application of UV systems in recreational water settings.

Pathogen and Particle Associations in Wastewater: Significance and Implications for Treatment and Disinfection Processes

Disinfection guidelines exist for pathogen inactivation in potable water and recycled water, but wastewater with high numbers of particles can be more difficult to disinfect, making compliance with the guidelines problematic. Disinfection guidelines specify that drinking water with turbidity ≥1 Nephelometric Turbidity Units (NTU) is not suitable for disinfection and therefore not fit for purpose. Treated wastewater typically has higher concentrations of particles (1-10NTU for secondary treated effluent). Two processes widely used for disinfecting wastewater are chlorination and ultraviolet radiation. In both cases, particles in wastewater can interfere with disinfection and can significantly increase treatment costs by increasing operational expenditure (chemical demand, power consumption) or infrastructure costs by requiring additional treatment processes to achieve the required levels of pathogen inactivation. Many microorganisms (viruses, bacteria, protozoans) associate with particles, which can allow them to survive disinfection processes and cause a health hazard. Improved understanding of this association will enable development of cost-effective treatment, which will become increasingly important as indirect and direct potable reuse of wastewater becomes more widespread in both developed and developing countries. This review provides an overview of wastewater and associated treatment processes, the pathogens in wastewater, the nature of particles in wastewater and how they interact with pathogens, and how particles can impact disinfection processes.

The application of computational fluid dynamics and small-scale physical models to assess the effects of operational practices on the risk to public health within large indoor swimming pools

Swimming pools provide an excellent facility for exercise and leisure but are also prone to contamination from microbial pathogens. The study modelled a 50-m × 20-m swimming pool using both a small-scale physical model and computational fluid dynamics to investigate how water and pathogens move around a pool in order to identify potential risk spots. Our study revealed a number of lessons for pool operators, designers and policy-makers: disinfection reaches the majority of a full-scale pool in approximately 16 minutes operating at the maximum permissible inlet velocity of 0.5 m/s. This suggests that where a pool is designed to have 15 paired inlets it is capable of distributing disinfectant throughout the water body within an acceptable time frame. However, the study also showed that the exchange rate of water is not uniform across the pool tank and that there is potential for areas of the pool tank to retain contaminated water for significant periods of time. 'Dead spots' exist at either end of the pool where pathogens could remain. This is particularly significant if there is a faecal release into the pool by bathers infected with Cryptosporidium parvum, increasing the potential for waterborne disease transmission.

Estimating the burden of acute gastrointestinal illness due to Giardia, Cryptosporidium, Campylobacter, E. coli O157 and norovirus associated with private wells and small water systems in Canada

Waterborne illness related to the consumption of contaminated or inadequately treated water is a global public health concern. Although the magnitude of drinking water-related illnesses in developed countries is lower than that observed in developing regions of the world, drinking water is still responsible for a proportion of all cases of acute gastrointestinal illness (AGI) in Canada. The estimated burden of endemic AGI in Canada is 20·5 million cases annually – this estimate accounts for under-reporting and under-diagnosis. About 4 million of these cases are domestically acquired and foodborne, yet the proportion of waterborne cases is unknown. There is evidence that individuals served by private systems and small community systems may be more at risk of waterborne illness than those served by municipal drinking water systems in Canada. However, little is known regarding the contribution of these systems to the overall drinking water-related AGI burden in Canada. Private water supplies serve an estimated 12% of the Canadian population, or ~4·1 million people. An estimated 1·4 million (4·1%) people in Canada are served by small groundwater (2·6%) and surface water (1·5%) supplies. The objective of this research is to estimate the number of AGI cases attributable to water consumption from these supplies in Canada using a quantitative microbial risk assessment (QMRA) approach. This provides a framework for others to develop burden of waterborne illness estimates for small water supplies. A multi-pathogen QMRA of Giardia, Cryptosporidium, Campylobacter, E. coli O157 and norovirus, chosen as index waterborne pathogens, for various source water and treatment combinations was performed. It is estimated that 103 230 AGI cases per year are due to the presence of these five pathogens in drinking water from private and small community water systems in Canada. In addition to providing a mechanism to assess the potential burden of AGI attributed to small systems and private well water in Canada, this research supports the use of QMRA as an effective source attribution tool when there is a lack of randomized controlled trial data to evaluate the public health risk of an exposure source. QMRA is also a powerful tool for identifying existing knowledge gaps on the national scale to inform future surveillance and research efforts.

A hydrodynamics-based approach to evaluating the risk of waterborne pathogens entering drinking water intakes in a large, stratified lake

Pathogen contamination of drinking water lakes and reservoirs is a severe threat to human health worldwide. A major source of pathogens in surface sources of drinking waters is from body-contact recreation in the water body. However, dispersion pathways of human waterborne pathogens from recreational beaches, where body-contact recreation is known to occur to drinking water intakes, and the associated risk of pathogens entering the drinking water supply remain largely undocumented. A high spatial resolution, three-dimensional hydrodynamic and particle tracking modeling approach has been developed to analyze the risk and mechanisms presented by pathogen dispersion. The pathogen model represents the processes of particle release, transport and survival. Here survival is a function of both water temperature and cumulative exposure to ultraviolet (UV) radiation. Pathogen transport is simulated using a novel and computationally efficient technique of tracking particle trajectories backwards, from a drinking water intake toward their source areas. The model has been applied to a large, alpine lake - Lake Tahoe, CA-NV (USA). The dispersion model results reveal that for this particular lake (1) the risk of human waterborne pathogens to enter drinking water intakes is low, but significant; (2) this risk is strongly related to the depth of the thermocline in relation to the depth of the intake; (3) the risk increases with the seasonal deepening of the surface mixed layer; and (4) the risk increases at night when the surface mixed layer deepens through convective mixing and inactivation by UV radiation is eliminated. While these risk factors will quantitatively vary in different lakes, these same mechanisms will govern the process of transport of pathogens.

UV irradiation responses in Giardia intestinalis

The response to ultraviolet light (UV) radiation, a natural stressor to the intestinal protozoan parasite Giardia intestinalis, was studied to deepen the understanding of how the surrounding environment affects the parasite during transmission. UV radiation at 10 mJ/cm(2) kills Giardia cysts effectively whereas trophozoites and encysting parasites can recover from UV treatment at 100 mJ/cm(2) and 50 mJ/cm(2) respectively. Staining for phosphorylated histone H2A showed that UV treatment induces double-stranded DNA breaks and flow cytometry analyses revealed that UV treatment of trophozoites induces DNA replication arrest. Active DNA replication coupled to DNA repair could be an explanation to why UV light does not kill trophozoites and encysting cells as efficiently as the non-replicating cysts. We also examined UV-induced gene expression responses in both trophozoites and cysts using RNA sequencing (RNA seq). UV radiation induces small overall changes in gene expression in Giardia but cysts show a stronger response than trophozoites. Heat shock proteins, kinesins and Nek kinases are up-regulated, whereas alpha-giardins and histones are down-regulated in UV treated trophozoites. Expression of variable surface proteins (VSPs) is changed in both trophozoites and cysts. Our data show that Giardia cysts have limited ability to repair UV-induced damage and this may have implications for drinking- and waste-water treatment when setting criteria for the use of UV disinfection to ensure safe water.

Elevation and vegetation determine Cryptosporidium oocyst shedding by yellow-bellied marmots (Marmota flaviventris) in the Sierra Nevada Mountains

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Yellow-bellied marmots of Sierra Nevada Mountain shed Cryptosporidium oocysts.

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Oocysts loads are low compared to other mammals in California.

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Shedding of oocysts is associated with altitude and vegetation type.

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Cryptosporidium oocysts were 99.9%–100% match to Cryptosporidium parvum.

Wildlife are increasingly recognized as important biological reservoirs of zoonotic species of Cryptosporidium that might contaminate water and cause human exposure to this protozoal parasite. The habitat range of the yellow-bellied marmot (Marmota flaviventris) overlaps extensively with the watershed boundaries of municipal water supplies for California communities along the foothills of the Sierra Nevada. We conducted a cross-sectional epidemiological study to estimate the fecal shedding of Cryptosporidium oocysts by yellow-bellied marmots and to quantify the environmental loading rate and determine risk factors for Cryptosporidium fecal shedding in this montane wildlife species. The observed proportion of Cryptosporidium positive fecal samples was 14.7% (33/224, positive number relative to total number samples) and the environmental loading rate was estimated to be 10,693 oocysts animal^-1 day^-1. Fecal shedding was associated with the elevation and vegetation status of their habitat. Based on a portion of the 18s rRNA gene sequence of 2 isolates, the Cryptosporidium found in Marmota flaviventris were 99.88%–100% match to multiple isolates of C. parvum in the GenBank.

Environmental considerations on solar disinfection of wastewater and the subsequent bacterial (re)growth

Solar disinfection of wastewater is under study, as a process initiated on-site and continuing in nature. The environmental factors implicating the process (light intensity, intermittence and receiving water matrix) are also under study.

UV-induced effects on chlorination of creatinine

Ultraviolet (UV) irradiation is commonly employed for water treatment in swimming pools to complement conventional chlorination, and to reduce the concentration of inorganic chloramine compounds. The approach of combining UV irradiation and chlorination has the potential to improve water quality, as defined by microbial composition. However, relatively little is known about the effects of this process on water chemistry. To address this issue, experiments were conducted to examine the effects of sequential UV254 irradiation/chlorination, as will occur in recirculating system of swimming pools, on disinfection byproduct (DBP) formation. Creatinine, which is present in human sweat and urine, was selected as the target precursor for these experiments. Enhanced formation of dichloromethylamine (CH3NCl2) and inorganic chloramines was observed to result from post-chlorination of UV-irradiated samples. Chlorocreatinine was found to be more sensitive to UV254 irradiation than creatinine; UV254 irradiation of chlorocreatinine resulted in opening of the ring structure, thereby yielding a series of intermediates that were more susceptible to free chlorine attack than their parent compound. The quantum yields for photodegradation of creatinine and chlorocreatinine at 254 nm were estimated at 0.011 ± 0.002 mol/E and 0.144 ± 0.011 mol/E, respectively. The N-Cl bond was found to be common to UV-sensitive chlorinated compounds (e.g., inorganic chloramines, CH3NCl2, and chlorocreatinine); compounds that were less susceptible to UV-based attack generally lacked the N-Cl bond. This suggested that the N-Cl bond is susceptible to UV254 irradiation, and cleavage of the N-Cl bond appears to open or promote reaction pathways that involve free chlorine, thereby enhancing formation of some DBPs and promoting loss of free chlorine. Proposed reaction mechanisms to describe this behavior based on creatinine as a precursor are presented.

Bacterial inactivation in water, DNA strand breaking, and membrane damage induced by ultraviolet-assisted titanium dioxide photocatalysis

The effects of UV-assisted TiO2-photocatalytic oxidation (PCO) inactivation of pathogenic bacteria (Escherichia coli O157:H7, Listeria monocytogenes, Salmonella typhimurium) in a liquid culture using different domains of UV irradiation (A, B and C) were evaluated. Structural changes in super-coiled plasmid DNA (pUC19) and genomic DNA of E. coli were observed using gel electrophoresis to demonstrate the photodynamic DNA strand breaking activity of UV-assisted TiO2-PCO. Membrane damage in bacterial cells was observed using both a scanning electron microscope (SEM) and a confocal laser scanning microscope (CLSM). Both UVC-TiO2-PCO and UVC alone resulted in an earlier bactericidal phase (initial counts of approximately 6 log CFU/mL) in 60 s and 90 s, respectively, in liquid culture. UVC-TiO2-PCO treatment for 6 min converted all plasmid DNA to the linear form; however, under UVC irradiation alone, super-coiled DNA remained. Prolonged UVC-TiO2-PCO treatment resulted in structural changes in genomic DNA from E. coli. SEM observations revealed that bacteria suffered severe visible cell damage after UVC-TiO2-PCO treatment for 30-60 min. S. typhimurium cells showed visible damage after 30 min, which was confirmed using CLSM. All treated cells were stained red using propidium iodide under a fluorescent light.

Ultraviolet-induced effects on chloramine and cyanogen chloride formation from chlorination of amino acids

Ultraviolet (UV)-based treatment is commonly used to augment chlorination in swimming pools. However, the effects of combined application of UV254/chlorine on disinfection byproduct (DBP) formation are incompletely defined. To examine this issue, experiments were conducted with amino acids (l-arginine, l-histidine, and glycine) that are representative of those introduced to swimming pools via human body fluids. For each precursor, stepwise experiments were conducted with chlorination and UV254 exposure, with/without post-chlorination. Net formation and decomposition of chloramines and cyanogen chloride (CNCl) were measured for a range of chlorine/precursor (Cl/P) molar ratios and UV254 doses. Substantial production of NH2Cl from l-arginine and l-histidine was observed at Cl/P = 1.0 and 2.0 when post-chlorination was applied to UV254-irradiated samples. These results suggested a mechanism of rapid N-chlorination, followed by cleavage of NH3 by UV254 irradiation. CNCl formation was observed from UV254-irradiated samples of l-arginine and l-histidine when Cl/P = 2.0 and 3.0, as well as from glycine for Cl/P ≤ 1. Structurally related precursor compounds were examined for CNCl formation potential in chlorination/UV experiments. CNCl formation was promoted by UV254 exposure of chlorinated imidazole and guanidine compounds, which suggested that these groups contributed to CNCl formation. The results have implications with respect to the application of chlorine and UV for water treatment in swimming pools and other settings, such as water reuse and advanced oxidation processes.

Halobenzoquinones in swimming pool waters and their formation from personal care products

Halobenzoquinones (HBQs) are a class of disinfection byproducts (DBPs) of health relevance. In this study, we aimed to uncover which HBQs are present in swimming pools. To achieve this goal, we developed a new method capable of determining eight HBQs while overcoming matrix effects to achieve reliable quantification. The method provided reproducible and quantitative recovery (67-102%) and detection limits of 0.03-1.2 ng/L for all eight HBQs. Using this new method, we investigated water samples from 10 swimming pools and found 2,6-dichloro-1,4-benzoquinone (2,6-DCBQ) in all the pools at concentrations of 19-299 ng/L, which was as much as 100 times higher than its concentration in the input tap water (1-6 ng/L). We also identified 2,3,6-trichloro-(1,4)benzoquinone (TriCBQ), 2,3-dibromo-5,6-dimethyl-(1,4)benzoquinone (DMDBBQ), and 2,6-dibromo-(1,4)benzoquinone (2,6-DBBQ) in some swimming pools at concentrations of <0.1-11.3, <0.05-0.7, and <0.05-3.9 ng/L, respectively, but not in the input tap water. We examined several factors to determine why HBQ concentrations in pools were much higher than in the input tap water. Higher dissolved organic carbon (DOC), higher doses of chlorine and higher temperatures enhanced the formation of HBQs in the pools. In addition, we conducted laboratory disinfection experiments and discovered that personal care products (PCPs) such as lotions and sunscreens can serve as precursors to form additional HBQs, such as TriCBQ, 2,6-dichloro-3-methyl-(1,4)benzoquinone (DCMBQ), and 2,3,5,6-tetrabromo-(1,4)benzoquinone (TetraB-1,4-BQ). These results explained why some HBQs existed in swimming pools but not in the input water. This study presents the first set of occurrence data, identification of new HBQ DBPs, and the factors for their enhanced formation in the swimming pools.

Recent advances in drinking water disinfection: successes and challenges

Drinking water is the most important single source of human exposure to gastroenteric diseases, mainly as a result of the ingestion of microbial contaminated water. Waterborne microbial agents that pose a health risk to humans include enteropathogenic bacteria, viruses, and protozoa. Therefore, properly assessing whether these hazardous agents enter drinking water supplies, and if they do, whether they are disinfected adequately, are undoubtedly aspects critical to protecting public health. As new pathogens emerge, monitoring for relevant indicator microorganisms (e.g., process microbial indicators, fecal indicators, and index and model organisms) is crucial to ensuring drinking water safety. Another crucially important step to maintaining public health is implementing Water Safety Plans (WSPs), as is recommended by the current WHO Guidelines for Drinking Water Quality. Good WSPs include creating health-based targets that aim to reduce microbial risks and adverse health effects to which a population is exposed through drinking water. The use of disinfectants to inactivate microbial pathogens in drinking water has played a central role in reducing the incidence of waterborne diseases and is considered to be among the most successful interventions for preserving and promoting public health. Chlorine-based disinfectants are the most commonly used disinfectants and are cheap and easy to use. Free chlorine is an effective disinfectant for bacteria and viruses; however, it is not always effective against C. parvum and G. lamblia. Another limitation of using chlorination is that it produces disinfection by-products (DBPs), which pose potential health risks of their own. Currently, most drinking water regulations aggressively address DBP problems in public water distribution systems. The DBPs of most concern include the trihalomethanes (THMs), the haloacetic acids (HAAs), bromate, and chlorite. However, in the latest edition of the WHO Guidelines for Drinking Water Quality, it is recommended that water disinfection should never be compromised by attempting to control DBPs. The reason for this is that the risks of human illness and death from pathogens in drinking water are much greater than the risks from exposure to disinfectants and disinfection by-products. Nevertheless, if DBP levels exceed regulatory limits, strategies should focus on eliminating organic impurities that foster their formation, without compromising disinfection. As alternatives to chlorine, disinfectants such as chloramines, ozone, chlorine dioxide, and UV disinfection are gaining popularity. Chlorine and each of these disinfectants have individual advantage and disadvantage in terms of cost, efficacy-stability, ease of application, and nature of disinfectant by-products (DBPs). Based on efficiency, ozone is the most efficient disinfectant for inactivating bacteria, viruses, and protozoa. In contrast, chloramines are the least efficient and are not recommended for use as primary disinfectants. Chloramines are favored for secondary water disinfection, because they react more slowly than chlorine and are more persistent in distribution systems. In addition, chloramines produce lower DBP levels than does chlorine, although microbial activity in the distribution system may produce nitrate from monochloramine, when it is used as a residual disinfectant, Achieving the required levels of water quality, particularly microbial inactivation levels, while minimizing DBP formation requires the application of proper risk and disinfection management protocols. In addition, the failure of conventional treatment processes to eliminate critical waterborne pathogens in drinking water demand that improved and/or new disinfection technologies be developed. Recent research has disclosed that nanotechnology may offer solutions in this area, through the use of nanosorbents, nanocatalysts, bioactive nanoparticles, nanostructured catalytic membranes, and nanoparticle-enhanced filtration.

Considering the risk of infection by cryptosporidium via consumption of municipally treated drinking water from a surface water source in a Southwestern Ontario community

Through the use of case-control analyses and quantitative microbial risk assessment (QMRA), relative risks of transmission of cryptosporidiosis have been evaluated (recreational water exposure vs. drinking water consumption) for a Canadian community with higher than national rates of cryptosporidiosis. A QMRA was developed to assess the risk of Cryptosporidium infection through the consumption of municipally treated drinking water. Simulations were based on site-specific surface water contamination levels and drinking water treatment log₁₀ reduction capacity for Cryptosporidium. Results suggested that the risk of Cryptosporidium infection via drinking water in the study community, assuming routine operation of the water treatment plant, was negligible (6 infections per 10¹³ persons per day--5th percentile: 2 infections per 10¹⁵ persons per day; 95th percentile: 3 infections per 10¹² persons per day). The risk is essentially nonexistent during optimized, routine treatment operations. The study community achieves between 7 and 9 log₁₀ Cryptosporidium oocyst reduction through routine water treatment processes. Although these results do not preclude the need for constant vigilance by both water treatment and public health professionals in this community, they suggest that the cause of higher rates of cryptosporidiosis are more likely due to recreational water contact, or perhaps direct animal contact. QMRA can be successfully applied at the community level to identify data gaps, rank relative public health risks, and forecast future risk scenarios. It is most useful when performed in a collaborative way with local stakeholders, from beginning to end of the risk analysis paradigm.

Biofilms reduce solar disinfection of Cryptosporidium parvum oocysts

Solar radiation reduces Cryptosporidium infectivity. Biofilms grown from stream microbial assemblages inoculated with oocysts were exposed to solar radiation. The infectivity of oocysts attached at the biofilm surface and oocysts suspended in water was about half that of oocysts attached at the base of a 32-μm biofilm.