Evaluating the Impact of Cl2•- Generation on Antibiotic-Resistance Contamination Removal via UV/Peroxydisulfate.

The removal of antibiotic-resistant bacteria (ARB) and antibiotic-resistance genes (ARGs) using sulfate anion radical (SO4•-)-based advanced oxidation processes has gained considerable attention recently. However, immense uncertainties persist in technology transfer. Particularly, the impact of dichlorine radical (Cl2•-) generation during SO4•--mediated disinfection on ARB/ARGs removal remains unclear, despite the Cl2•- concentration reaching levels notably higher than those of SO4•- in certain SO4•--based procedures applied to secondary effluents, hospital wastewaters, and marine waters. The experimental results of this study reveal a detrimental effect on the disinfection efficiency of tetracycline-resistant Escherichia coli (Tc-ARB) during SO4•--mediated treatment owing to Cl2•- generation. Through a comparative investigation of the distinct inactivation mechanisms of Tc-ARB in the Cl2•-- and SO4•--mediated disinfection processes, encompassing various perspectives, we confirm that Cl2•- is less effective in inducing cellular structural damage, perturbing cellular metabolic activity, disrupting antioxidant enzyme system, damaging genetic material, and inducing the viable but nonculturable state. Consequently, this diminishes the disinfection efficiency of SO4•--mediated treatment owing to Cl2•- generation. Importantly, the results indicate that Cl2•- generation increases the potential risk associated with the dark reactivation of Tc-ARB and the vertical gene transfer process of tetracycline-resistant genes following SO4•--mediated disinfection. This study underscores the undesired role of Cl2•- for ARB/ARGs removal during the SO4•--mediated disinfection process.

Non-regulated haloaromatic water disinfection byproducts act as endocrine and lipid disrupters in human placental cells.

The disinfection of drinking water generates hundreds of disinfection byproducts (DBPs), including haloaromatic DBPs. These haloaromatic DBPs are suspected to be more toxic than haloaliphatic ones, and they are currently not regulated. This work investigates their toxicity and ability to interfere with estrogen synthesis in human placental JEG-3 cells, and their genotoxic potential in human alveolar A549 cells. Among the haloaromatic DBPs studied, halobenzoquinones (2,6-dichloro-1,4-benzoquinone (DCBQ) and 2,6-dibromo-1,4-benzoquinone (DBBQ)) showed the highest cytotoxicity (EC50: 18-26 µg/mL). They induced the generation of very high levels of reactive oxygen species (ROS) and up-regulated the expression of genes involved in estrogen synthesis (cyp19a1, hsd17b1). Increased ROS was linked to significant depletion of polyunsaturated lipid species from inner cell membranes. The other DBPs tested showed low or no significant cytotoxicity (EC50 ≥ 100 µg/mL), while 2,4,6-trichloro-phenol (TCP), 2,4,6-tribromo-phenol (TBP) and 3,5-dibromo-4-hydroxybenzaldehyde (DCHB) induced the formation of micronuclei at concentrations much higher than those typically found in water (100 µg/mL). This study reveals the different modes of action of haloaromatic DBPs, and highlights the toxic potential of halobenzoquinones, which had a significant impact on the expression of placenta steroid metabolism related genes and induce oxidative stress, implying potential adverse health effects.

N-nitrosamines induced gender-dimorphic effects on infant rats at environmental levels.

The safety of drinking water has always been a concern for people all over the world. N-nitrosamines (NAs), a kind of nitrogenous disinfection by-products (N-DBPs), are generally detected as a mixture in drinking water at home and abroad. Studies have shown that individual NAs posed strong carcinogenicity at high concentrations. However, health risks of NAs at environmental levels (concentrations in drinking water) are still unclear. Therefore, the potential health risks of environmentally relevant NAs exposure in drinking water needs to be conducted. In this study, blood biochemical analysis and metabolomics based on nuclear magnetic resonance (NMR) were performed to comprehensively investigate NAs induced metabolic disturbance in infant rats at environmental levels. Results of blood biochemical indices analysis indicated that AST in the serum of male rats in NAs-treated group exhibited a significant gender-specific difference. Multivariate statistics showed that two and eight significantly disturbed metabolic pathways were identified in the serum samples of NAs-treated male and female rats, respectively. In the urine samples of NAs-treated female rats, glycine, serine, and threonine metabolism pathway was significantly disturbed; while three significantly disturbed metabolic pathways were found in the urine of NAs-treated male rats. Finally, results of spearman correlation coefficients suggested that the disturbances of metabolism profile in serum and urine were correlated with changes in the gut microbiota (data derived from our published paper). Data presented here aimed to generate new health risk data of NAs mixture exposure at environmental levels and provide theoretical support for drinking water safety management. ENVIRONMENTAL IMPLICATION: N-nitrosamines (NAs) are a kind of nitrogenous disinfection by-products (N-DBPs) generated during drinking water disinfection processes. Herein, health risks of NAs at environmental levels (concentrations in drinking water) are investigated using blood biochemical analysis and nuclear magnetic resonance (NMR)-based metabolomics. Results confirmed NAs induced gender-specific on the metabolism in rat and the disturbances of metabolism profile in serum and urine were correlated with changes in the gut microbiota. Data presented here aimed to generate new health risk data of NAs mixture exposure at environmental levels and provide theoretical support for drinking water safety management.

Inactivation of Giardia intestinalis cysts in water using a sonochemical method based on mid-high-frequency waves.

Giardia intestinalis is a pollutant of food and water, resistant to conventional disinfection treatments and its elimination requires effective methods action. Herein, mid-high-frequency ultrasound (375 kHz), which produces HO• and H2O2, was used as an alternative method of treatment to inactivate Giardia intestinalis cysts in water. The effect of ultrasound power (4.0, 11.2, 24.4 W) on the sonogeneration of radicals was tested, showing that 24.4 W was the condition most favorable to treat the parasite. The viability of the protozoan cysts was evaluated using the immunofluorescence technique and vital stains, showing this protocol was useful to quantify the parasite. The sonochemical method (at 375 kHz and 24.4 W) was applied at different treatment times (10, 20, and 40 min). A significant decrease in the protozoan concentration (reduction of 52.4% of viable cysts) was observed after 20 min of treatment. However, the extension of treatment time up to 40 min did not increase the inactivation. Disinfecting action was associated with attacks on the Giardia intestinalis cyst by sonogenerated HO• and H2O2 (which may induce structural damage, even the cell lysis). For future work is recommended to test combinations with UVC or Fenton process to enhance the inactivating action of this method.•Mid-high-frequency ultrasound produces HO• and H2O2 profitable to inactivate Giardia intestinalis.•Immunofluorescence technique and vital stains allowed us to quantify the parasite viability.•Giardia intestinalis cysts concentration decreased by 52.4% after only 20 min of sonication.

Chloroacetonitrile reduces rat prenatal bone length and induces oxidative stress, apoptosis, and DNA damage in rat fetal liver.

One of the disinfection byproducts of chlorinating drinking water is chloroacetonitrile (CAN). Thirty-six female rats were used and distributed equally into four groups. The low dose treated group received CAN at a dose of 5.5 mg/kg body weight/day (1/40 LD50 ) orally from the 6th to 12th day of gestation. The high dose treated group received 11 mg/kg body weight/day (1/20 LD50 ) of CAN orally for the same period, the vehicle control group received 1 mL of corn oil, and the water control group received 1 mL of distilled water orally for the same period. High dose exposure to CAN significantly reduced gravid uterine weight, fetal body weights, and length, and caused obvious skeletal deformities, weak mineralization. Fetal tibial growth plates displayed histopathologic changes. Induced oxidative stress and redox imbalance in fetal liver tissues was evidenced by significantly decreased in catalase and superoxide dismutase activity, and elevated malondialdehyde levels. Histopathological, glycogen content changes, and DNA damage were observed in the fetal liver of high dose treated group. Additionally, administration of high dose of CAN induced apoptosis, evidenced by increased caspase-3 concentration in fetal liver. Thus, extensive exposure to CAN induces poor pregnancy outcomes. CAN levels in water should be monitored regularly.

Virtual prototyping and characterization of a point-of-entry UV-LED water disinfection reactor with the synergic effect of radiation, hydrodynamics, and inactivation kinetics.

We developed and studied one of the first high-flow UV-LED water disinfection reactors applicable to point-of-entry (POE) water disinfection. A multiphysics computational model was created to predict the performance of UV reactor design concepts by modeling the synergic effect of radiation, hydrodynamics, and the inactivation kinetics of microorganisms. The geometrical optics that describe light propagation in terms of rays were employed to model the radiation profile of multiple UV-LEDs with optical components in complex reactor geometries, the first account of such an approach. The computational solution of the mass, momentum, and species equations was applied to model the hydrodynamics and kinetics. We designed a reactor through a detailed computational study of the optical and hydrodynamic performance of various design strategies. Highly efficient UV fluence distribution in the reactor was achieved by creating nearly collimated UV radiation beams across the reactor and managing the hydrodynamics using a flow distributor. We fabricated a prototype of the optimized reactor design for experimental studies. Biodosimetry tests were conducted for various flow rates and UV transmittances (UVTs), and the experimental results were compared with the model predictions. The design, which employed 14 UV-LEDs assembled over custom-made optical modules, resulted in a reduction equivalent dose (RED) of 65 mJ/cm2 at a flow rate of 20 liters per minute (LPM) while consuming about 50 W energy. This reactor design required only 0.05 W radiant power per LPM flow rate to achieve an NSF Class A UV dose equivalent of 40 mJ/cm2. The findings of this study provide insights into UV-LED reactor development strategies as well as the creation and application of reactor virtual prototyping tools for designing and optimizing highly efficient UV-LED reactors.

Continuous inactivation of human adenoviruses in water by a novel g-C3N4/WO3/biochar memory photocatalyst under light-dark cycles.

Viruses transmitted by water have raised considerable concerns for public health. A novel memory photocatalyst of g-C3N4/WO3/biochar was successfully developed for effective inactivation of human adenoviruses (HAdVs) in water, in which WO3 as an electron-storage reservoir and biochar as an electron shuttle is employed to synergistically improve photocatalytic activity of g-C3N4. The tertiary composite exhibited continuous photocatalytic performance for HAdVs inactivation without regrowth in water under light-dark cycles, i.e., ∼3.9-log inactivation under 6-h visible light irradiation and an additional ∼1.1-log inactivation under the following 6-h dark. The enhanced virucidal mechanism was attributed to the heterojunction formation and especially the electron-transfer pathway switching via biochar incorporation, contributing to electron transfer and storage in the light phase and then electron release in the dark phase, along with obviously increased generation of the virus-killing •OH radicals under light-dark cycles.

Eficácia das medidas domiciliares de desinfecção da água para consumo humano: enfoque para o contexto de Santarém, Pará, Brasil / Efficacy of household methods for disinfecting water for human consumption: focus on the context of Santarém, state of Pará, Brazil / Efectividad de las medidas domiciliarias para desinfectar el agua para consumo humano: desde el contexto de Santarém, estado de Pará, Brasil

Na região Amazônica, cidades como Santarém, no Estado do Pará, Brasil, ainda carecem de Estações de Tratamento de Água para atender toda a população. Nesses locais, medidas domiciliares de desinfecção da água são importantes para preservar a potabilidade e evitar efeitos indesejáveis na saúde. Este estudo avaliou experimentalmente o efeito das medidas domiciliares na eliminação de Escherichia coli em amostras de água. As técnicas avaliadas para esse trabalho foram: (i) hipoclorito de sódio 2,5%; (ii) fervura; (iii) filtro de cerâmica; e (iv) exposição solar. Foram testadas amostras, combinando-se diferentes concentrações de E. coli (entre 3 e 100 unidades formadoras de colônias/100mL). Os resultados mostraram que as medidas domiciliares de desinfecção foram eficazes na eliminação da E. coli, com exceção do filtro de cerâmica, cujas amostras de água, mesmo após a filtragem, apresentaram-se positivas para o crescimento da bactéria. Considerando que a distribuição da água tratada não chega à maior parte da população que reside em Santarém e em áreas periurbanas, como em comunidades quilombolas e ribeirinhas, o uso das medidas como hipoclorito de sódio 2,5%, fervura e exposição solar poderão favorecer a promoção da saúde e diminuir a ocorrência de surtos de doenças diarreicas veiculadas pela água.

In the Amazon region, cities such as Santarém, in the state of Pará, Brazil, still lack Water Treatment Stations to serve the entire population. In these places, household methods of water disinfection are important to preserve potability and avoid undesirable health effects. Our study experimentally evaluated the effect of household methods for eliminating Escherichia coli in water samples. The techniques evaluated for this study were: (i) sodium hypochlorite 2.5%; (ii) boiling; (iii) ceramic filter, and (iv) sun exposure. Samples were tested, combining different concentrations of E. coli (from 3 to 100 colony forming units/100mL). The results showed that household disinfection methods were effective in eliminating E. coli; except for the ceramic filter, the water of which was still positive for their growth, even after filtration. Considering that the distribution of treated water does not reach most of the population living in Santarém and in peri-urban areas, such as the quilombola and riverside communities, the use of such methods as sodium hypochlorite 2.5%, boiling, and sun exposure may favor health promotion and reduce the occurrence of outbreaks of dysentery transmitted by water.

En la región Amazónica, las ciudades como Santarém, en el estado de Pará, Brasil, todavía carecen de Estaciones de Tratamiento de Agua para atender a toda la población. En estos lugares, las medidas de desinfección domiciliaria del agua son importantes para preservar la potabilidad y evitar efectos indeseables en la salud. Este estudio evaluó el efecto de medidas domiciliarias en la eliminación de Escherichia coli en muestras de agua. Las técnicas evaluadas en este trabajo fueron: (i) hipoclorito de sodio al 2,5%; (ii) hervir el agua; (iii) filtro cerámico y (iv) exposición al sol. Se probaron muestras combinando diferentes concentraciones de E. coli (entre 3 y 100 unidades formadoras de colonias/100mL). Los resultados mostraron que las medidas de desinfección domiciliaria fueron efectivas en la eliminación de E. coli, con excepción del filtro cerámico que presentó un resultado positivo para su crecimiento en las muestras de agua, aún después de filtrada. Considerando que la distribución de agua tratada no llega a la mayoría de la población residente en Santarém y en áreas periurbanas como comunidades quilombolas y ribereñas, el uso de técnicas como el hipoclorito de sodio al 2,5%; hervir el agua o exponerla al sol pueden favorecer una promoción de la salud y reducir el surgimiento de brotes de enfermedades diarreicas transmitidas por el agua.

Oxidative injury induced by drinking water disinfection by-products dibromoacetonitrile and dichloroacetonitrile in mouse hippocampal neuronal cells: The protective effect of N-acetyl-L-cysteine.

Dibromoacetonitrile (DBAN) and dichloroacetonitrile (DCAN) are haloacetonitriles (HANs) produced as by-products of chloramine disinfection of drinking water and can cause neurotoxicity. The molecular pathways leading to HAN-induced neuronal cell death remain unclear. The nuclear factor erythroid 2-related factor 2 (Nrf2) is an important regulator of oxidation reactions. We explored the role of the sequestosome 1 (p62)-Kelch-like ECH-associated protein 1 (Keap1)-Nrf2 pathway in DBAN- and DCAN-induced mouse hippocampal neuronal (HT22) cell injury. DBAN and DCAN reduced cell viability, increased lactate dehydrogenase release rate, and promoted apoptosis. Over the same treatment time, DBAN at lower concentrations caused cell injury, suggesting that DBAN is more cytotoxic than DCAN. DBAN and DCAN triggered oxidative stress by reducing intracellular glutathione and increasing reactive oxygen species concentrations. DBAN and DCAN activated the Nrf2 pathway. Furthermore, Nrf2 inhibitors (all-trans retinoic acid) attenuated DBAN- and DCAN-induced toxicity, whereas Nrf2 activators (tert-Butylhydroquinone) achieved the opposite effect. This indicates that activation of the Nrf2 pathway mediates DBAN- and DCAN-induced cell injury. Notably, the expression of p62, a noncanonical pathway that mediates Nrf2 activation, increased, whereas the expression of Keap1, another regulator of Nrf2, decreased. We noted that high p62 expression activated the Nrf2 pathway, and p62 was regulated through Nrf2, forming a positive feedback loop. N-acetyl-L-cysteine, a mercaptan substance, protected against DBAN- and DCAN-induced toxicity and inhibited the Nrf2 pathway. In summary, Nrf2 pathway inhibition and mercaptan supplementation prevent DBAN- and DCAN-induced HT22 cell injury, accordingly, targeting them is a potential approach to preventing HAN-induced neurotoxicity.

Polyphenol modified natural collagen fibrous network towards sustainable and antibacterial microfiltration membrane for efficient water disinfection.

Because of their low-cost and high bacterial interception efficiency, large-scale membrane separation technologies like microfiltration (MF) have been widely implemented for water disinfection. However, lack of antibacterial ability and low sustainability are two major drawbacks of most petroleum-based MF membranes, which are normally associated with hazardous issues including biofouling and nonbiodegradable waste. In this work, abundant animal hides, which are by-products of the meat processing industry, were proposed as raw materials to fabricate a sustainable MF membrane due to their natural, hierarchical, and renewable collagen fibrous network (CFN) with inherent biodegradability. After the removal of non-collagen compositions from animal hides, such as hair and fat, through a facile pretreating process base on green chemistry principles, a thin CFN based membrane (CFN-M) with a similar micropore size to that of commercial MF membranes could be produced. Furthermore, inspired by conventional leather tanning technology, tannic acids (TA) were selected as plant polyphenol tanning agent to modify collagen fibers based on tanning chemistry to improve the thermal stability of CFN-M. Moreover, the TA cross-linked CFN-M (TA@CFN-M) exhibited excellent antibacterial properties due to the production of reactive oxygen species (ROS) by the catechol functional group. The resulting TA@CFN-M achieved >99.9% water disinfection efficiency with a flux of ∼150 L m-2 h-1 via gravity-driven operation, while simultaneously showing admirable anti-biofouling ability. Different from the commercial MF membrane, based on the green chemistry principle, this work may shed light on designing new sustainable and antibacterial membranes for anti-biofouling water disinfection.

Assessment of the 20L SODIS bucket household water treatment technology under field conditions in rural Malawi.

Two billion people worldwide consume unsafe drinking water. The problem is particularly pronounced in Sub-Saharan Africa, where more than a quarter of the population relies on unimproved surface water sources. Based on the principles of solar water disinfection (SODIS), a new household water treatment technology, the SODIS bucket, was developed to improve the microbial quality of water from these sources based on controlled tests in a laboratory setting. This study set out to evaluate the efficacy of the technology in a field setting, in rural communities in the Chikwawa District in southern Malawi. SODIS experiments were carried out in two different vessels (1-L PET bottles and 20-L polypropylene SODIS buckets), over three months using unprotected water sources normally used by community members. Vessels were exposed to direct sunlight for 8 h per day in a village setting and were sampled at regular intervals to determine total coliforms, E. coli, turbidity, UV transmittance and UV dose. In these experiments, the SODIS bucket reached inactivation targets for E. coli (<1 CFU/100 mL) in two of seven experiments and for total coliforms in one of seven for total coliforms (<50 CFU/100 mL), despite having greater UV doses than were seen in the evaluation carried out under controlled conditions during the bucket's development. PET bottles reached inactivation targets for both E. coli and total coliforms in five of seven experiments. There was no single factor that could be identified as preventing adequate inactivation, but the role of organic matter, inconsistent nature of the water source, and vessel size, when coupled with organic matter, were identified as contributing factors. This study highlights the need for further prototyping to provide a suitable pre-treatment step for unprotected water sources, and the importance of field testing with real-life parameters to ensure new technologies are context appropriate.

Dual-wavelength light radiation for synergistic water disinfection.

Development of the narrow-band mercury-free light sources, such as light emitting diodes (LEDs) and excilamps, has stimulated research on inactivation of pathogenic microorganisms by dual-wavelength light radiation. To date, dual-wavelength light radiation has emerged as an advanced tool for enhancing microbial inactivation in water in view of potential synergistic effect. This is the first review that aims at elucidating its mechanisms under dual-wavelength light exposure and surveying a body of related literature in terms of yes-or-no synergy. We have proposed three key inactivation mechanisms, which function in the estimated spectrum ranges I (190-254 nm), II (250-320 nm) and III (300-405 nm) and provide a synergistic effect when combined. These mechanisms involve proteins damage and DNA repair suppression (I), direct and indirect DNA damage (II) and generation of reactive oxygen species (ROS) by endogenous photosensitizers (III), such as porphyrins and flavins. A synergy under dual-wavelength light irradiation simultaneously or sequentially occurs if coupling two wavelengths of different ranges (I + II, I + III, II + III) in order to trigger different inactivation mechanisms. Recent advances of dual-wavelength light strategy in photodynamic therapy could be applied for water disinfection. They bring opportunities for applying the sources of near-UV and visible radiation and making the disinfection processes more energy- and cost-effective. From this standpoint, the synergistically efficient dual-wavelength combinations II + III and the combinations within the extended to 700 nm range III (near-UV + VIS) appear to be promising for developing novel advanced oxidation processes for disinfection of real turbid waters.

SARS-CoV-2 in environmental perspective: Occurrence, persistence, surveillance, inactivation and challenges.

The unprecedented global spread of the severe acute respiratory syndrome (SARS) caused by SARS-CoV-2 is depicting the distressing pandemic consequence on human health, economy as well as ecosystem services. So far novel coronavirus (CoV) outbreaks were associated with SARS-CoV-2 (2019), middle east respiratory syndrome coronavirus (MERS-CoV, 2012), and SARS-CoV-1 (2003) events. CoV relates to the enveloped family of Betacoronavirus (ßCoV) with positive-sense single-stranded RNA (+ssRNA). Knowing well the persistence, transmission, and spread of SARS-CoV-2 through proximity, the faecal-oral route is now emerging as a major environmental concern to community transmission. The replication and persistence of CoV in the gastrointestinal (GI) tract and shedding through stools is indicating a potential transmission route to the environment settings. Despite of the evidence, based on fewer reports on SARS-CoV-2 occurrence and persistence in wastewater/sewage/water, the transmission of the infective virus to the community is yet to be established. In this realm, this communication attempted to review the possible influx route of the enteric enveloped viral transmission in the environmental settings with reference to its occurrence, persistence, detection, and inactivation based on the published literature so far. The possibilities of airborne transmission through enteric virus-laden aerosols, environmental factors that may influence the viral transmission, and disinfection methods (conventional and emerging) as well as the inactivation mechanism with reference to the enveloped virus were reviewed. The need for wastewater epidemiology (WBE) studies for surveillance as well as for early warning signal was elaborated. This communication will provide a basis to understand the SARS-CoV-2 as well as other viruses in the context of the environmental engineering perspective to design effective strategies to counter the enteric virus transmission and also serves as a working paper for researchers, policy makers and regulators.

Mechanism and efficacy of virus inactivation by a microplasma UV lamp generating monochromatic UV irradiation at 222 nm.

This study evaluated the potential of a microplasma UV lamp as an alternative UV source to the current mercury-based (Hg-based) UV lamp for water disinfection. We developed a set of PCR-based molecular assays (long-range qPCR, DNase, and binding assay) to quantify the adenovirus genome, capsid, and fiber damage with a wide detection range (100.5-106.5 PFU/mL). We used these molecular assays to characterize adenovirus (AdV) inactivation kinetics by microplasma UV that produced monochromatic UV at 222 nm. We found that the inactivation rate constant (0.142 cm2/mJ) due to microplasma UV was 4.4 times higher than that of low-pressure Hg UV (0.032 cm2/mJ). This high efficacy was attributed to monochromatic UV wavelength at 222 nm damaging the AdV capsid protein. The results of these molecular assays also proved that microplasma UV and medium-pressure Hg UV with a bandpass filter at 223 nm (MPUV223nm) have a similar influence on AdV (p>0.05). We then estimated the relative energy efficiency of MPUV and microplasma UV to LPUV for 4 log reduction of the viruses. We found that the microplasma UV resulted in higher inactivation rate constants for viruses than the current Hg-based UV. Consequently, microplasma UV could be more energy efficient than low-pressure Hg UV for water disinfection if the wall-plug efficiency of the microplasma UV lamp improved to 8.4% (currently 1.5%). Therefore, the microplasma UV lamp is a promising option for water disinfection.

Virus Disinfection from Environmental Water Sources Using Living Engineered Biofilm Materials.

Waterborne viruses frequently cause disease outbreaks and existing strategies to remove such viral pathogens often involve harsh or energy-consuming water treatment processes. Here, a simple, efficient, and environmentally friendly approach is reported to achieve highly selective disinfection of specific viruses with living engineered biofilm materials. As a proof-of-concept, Escherichia coli biofilm matrix protein CsgA was initially genetically fused with the influenza-virus-binding peptide (C5). The resultant engineered living biofilms could correspondingly capture virus particles directly from aqueous solutions, disinfecting samples to a level below the limit-of-detection for a qPCR-based detection assay. By exploiting the surface-adherence properties of biofilms, it is further shown that polypropylene filler materials colonized by the CsgA-C5 biofilms can be utilized to disinfect river water samples with influenza titers as high as 1 × 107 PFU L-1. Additionally, a suicide gene circuit is designed and applied in the engineered strain that strictly limits the growth of bacterial, therefore providing a viable route to reduce potential risks confronted with the use of genetically modified organisms. The study thus illustrates that engineered biofilms can be harvested for the disinfection of pathogens from environmental water samples in a controlled manner and highlights the unique biology-only properties of living substances for material applications.

Effect of chemical, microwave irradiation, steam autoclave, ultraviolet light radiation, ozone and electrolyzed oxidizing water disinfection on properties of impression materials: A systematic review and meta-analysis study.

OBJECTIVES: The objective of this systematic review and meta-analysis study was to identify the different disinfection methods and materials and the existing evidence on their effect on properties of the different impression materials. MATERIAL AND METHODS: An electronic search of MEDLINE (PubMed), Science Direct, and Google Scholar databases was performed to retrieve related English-language articles published between January 2000 and July 2019. Available studies with search terms such as: Impression disinfection, disinfection method, impression dimensional stability and impression wettability were used. The selected articles were reviewed by screening their titles and abstracts and full text. Finally, a total of 70 articles were considered relevant and were included in this study. RESULTS: Extensive studies were conducted to determine the effect of the different disinfection methods and materials on the properties of the different impression materials such as dimensional stability, wettability and surface roughness. While some studies reported significant changes in the properties of the impression materials, others reported either no changes or minor insignificant effects. CONCLUSIONS: Some studies reported significant changes in the properties of the impression materials as a result of using different disinfection methods, whereas others reported either minor insignificant or no changes. Although the findings of the studies were controversial, care should be taken to avoid distortion of impressions and loss of their surface details that can adversely affect the fitting accuracy of the restorations. Therefore, better designed and standardized studies are needed to evaluate the effect of different commonly used disinfectants on properties of impression materials. Moreover, manufacturers should be encouraged to recommend specific disinfection methods and materials for disinfecting the impression materials to ensure their optimal accuracy.

Legionella pneumophila and Protozoan Hosts: Implications for the Control of Hospital and Potable Water Systems.

Legionella pneumophila is an opportunistic waterborne pathogen of public health concern. It is the causative agent of Legionnaires' disease (LD) and Pontiac fever and is ubiquitous in manufactured water systems, where protozoan hosts and complex microbial communities provide protection from disinfection procedures. This review collates the literature describing interactions between L. pneumophila and protozoan hosts in hospital and municipal potable water distribution systems. The effectiveness of currently available water disinfection protocols to control L. pneumophila and its protozoan hosts is explored. The studies identified in this systematic literature review demonstrated the failure of common disinfection procedures to achieve long term elimination of L. pneumophila and protozoan hosts from potable water. It has been demonstrated that protozoan hosts facilitate the intracellular replication and packaging of viable L. pneumophila in infectious vesicles; whereas, cyst-forming protozoans provide protection from prolonged environmental stress. Disinfection procedures and protozoan hosts also facilitate biogenesis of viable but non-culturable (VBNC) L. pneumophila which have been shown to be highly resistant to many water disinfection protocols. In conclusion, a better understanding of L. pneumophila-protozoan interactions and the structure of complex microbial biofilms is required for the improved management of L. pneumophila and the prevention of LD.

Chlorine Dioxide Degradation Issues on Metal and Plastic Water Pipes Tested in Parallel in a Semi-Closed System.

Chlorine dioxide (ClO2) has been widely used as a disinfectant in drinking water in the past but its effects on water pipes have not been investigated deeply, mainly due to the difficult experimental set-up required to simulate real-life water pipe conditions. In the present paper, four different kinds of water pipes, two based on plastics, namely random polypropylene (PPR) and polyethylene of raised temperature (PERT/aluminum multilayer), and two made of metals, i.e., copper and galvanized steel, were put in a semi-closed system where ClO2 was dosed continuously. The semi-closed system allowed for the simulation of real ClO2 concentrations in common water distribution systems and to simulate the presence of pipes made with different materials from the source of water to the tap. Results show that ClO2 has a deep effect on all the materials tested (plastics and metals) and that severe damage occurs due to its strong oxidizing power in terms of surface chemical modification of metals and progressive cracking of plastics. These phenomena could in turn become an issue for the health and safety of drinking water due to progressive leakage of degraded products in the water.

Inactivation of Adenovirus in Water by Natural and Synthetic Compounds.

Millions of people use contaminated water sources for direct consumption. Chlorine is the most widely disinfection product but can produce toxic by-products. In this context, natural and synthetic compounds can be an alternative to water disinfection. Therefore, the aim of this study was to assess the inactivation of human adenovirus by N-chlorotaurine (NCT), bromamine-T (BAT) and Grape seed extract (GSE) in water. Distilled water artificially contaminated with recombinant human adenovirus type 5 (rAdV-GFP) was treated with different concentrations of each compound for up to 120 min, and viral infectivity was assessed by fluorescence microscopy. The decrease in activity of the compounds in the presence of organic matter was evaluated in water supplemented with peptone. As results, NCT and GSE inactivated approximately 2.5 log10 of adenovirus after 120 min. With BAT, more than 4.0 log10 decrease was observed within 10 min. The oxidative activity of 1% BAT decreased by 50% in 0.5% peptone within a few minutes, while the reduction was only 30% for 1% NCT in 5% peptone after 60 min. Organic matter had no effect on the activity of GSE. Moreover, the minimal concentration of BAT and GSE to kill viruses was lower than that known to kill human cells. It was concluded that the three compounds have potential to be used for water disinfection for drinking or reuse purposes.

Assembly of pi-functionalized quaternary ammonium compounds with graphene hydrogel for efficient water disinfection.

Graphene hydrogels hold great potential for the disinfection of bacteria-contaminated water. However, the intrinsic antibacterial activity of graphene hydrogels is not satisfactory, and the incorporation of other antibacterial agents often results in their unwanted releases. Here, we present a new strategy to improve the antibacterial activities of graphene hydrogels. We first synthesized a new pi-conjugated molecule containing five aromatic rings and two side-linked quaternary ammonium (QA) groups, denoted as piQA. Next, we fabricated composite gravity filters by assembling piQA with reduced graphene oxide (rGO) hydrogel. The rGO hydrogel helps to form a sponge-like physical sieve, contributes to the overall antibacterial activity, and provides abundant pi-rich surfaces. The large aromatic cores of piQA allow the formation of collectively strong pi-pi interactions with rGO, resulting in a high piQA mass loading of ∼31 wt%. Due to the sieving effect of rGO hydrogel and the synergistic antibacterial activity of rGO and piQA, the filters prepared based on piQA-rGO assemblies can remove over 99.5% of Gram-negative Escherichia coli (E. coli) and Gram-positive Staphylococcus aureus (S. aureus) cells with a high-water treatment capacity of 10 L g-1. Furthermore, the piQA-rGO assemblies show low toxicity towards two different mammalian cell lines (L929 and macrophages), and the release of piQA is also negligible. Overall, the new piQA-rGO assembly demonstrates high potential for water disinfection applications.