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.

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.

Synthesis and Characterization of Ag/ZnO Nanoparticles for Bacteria Disinfection in Water.

In this study, two green synthesis routes were used for the synthesis of Ag/ZnO nanoparticles, using cassava starch as a simple and low-cost effective fuel and Aloe vera as a reducing and stabilizing agent. The Ag/ZnO nanoparticles were characterized and used for bacterial disinfection of lake water contaminated with Escherichia coli (E. coli). Characterization indicated the formation of a face-centered cubic structure of metallic silver nanoparticles with no insertion of Ag into the ZnO hexagonal wurtzite structure. Physicochemical and bacteriological analyses described in "Standard Methods for the Examination of Water and Wastewater" were used to evaluate the efficiency of the treatment. In comparison to pure ZnO, the synthesized Ag/ZnO nanoparticles showed high efficiencies against Escherichia coli (E. coli) and general coliforms present in the lake water. These pathogens were absent after treatment using Ag/ZnO nanoparticles. The results indicate that Ag/ZnO nanoparticles synthesized via green chemistry are a promising candidate for the treatment of wastewaters contaminated by bacteria, due to their facile preparation, low-cost synthesis, and disinfection efficiency.

The Role of New Inorganic Materials in Composite Membranes for Water Disinfection.

Today, there is an increasing interest in improving the physicochemical properties of polymeric membranes by merging the membranes with different inorganic materials. These so-called composite membranes have been implemented in different membrane-based technologies (e.g., microfiltration, ultrafiltration, nanofiltration, membrane bioreactors, among others) for water treatment and disinfection. This is because such inorganic materials (such as TiO2-, ZnO-, Ag-, and Cu-based nanoparticles, carbon-based materials, to mention just a few) can improve the separation performance of membranes and also some other properties, such as antifouling, mechanical, thermal, and physical and chemical stability. Moreover, such materials display specific biological activity towards viruses, bacteria, and protozoa, showing enhanced water disinfection properties. Therefore, the aim of this review is to collect the latest advances (in the last five years) in using composite membranes and new hybrid materials for water disinfection, paying particular emphasis on relevant results and new hydride composites together with their preparation protocols. Moreover, this review addresses the main mechanism of action of different conventional and novel inorganic materials toward biologically active matter.

MS2 coliphage inactivation by Al/Fe PILC-activated Catalytic Wet Peroxide Oxidation: multiresponse statistical optimization.

The optimization of the Catalytic Wet Peroxide Oxidation (CWPO) assisted by an Al/Fe-pillared clay (Al/Fe-PILC) was assessed in the inactivation of the MS2 coliphage in the presence of a synthetic surrogate of natural organic matter (NOM). The simultaneous effect of two experimental factors (i) H2O2 dose - (H2O2)d (3.00-25.50 % of the H2O2 theoretically required for full mineralization) and (ii) catalyst concentration (0.33-2.60 g/L), and four non-controllable variables (covariates) (a) circumneutral pH (6.00-9.00), (b) temperature (5.00-25.0 °C), (c) synthetic NOM concentration (2.0-20.0 mg C/L) and (d) MS2 titer (104, 105 and 106 PFU/mL) was investigated by Response Surface Methodology (RSM). Every response was modeled and maximized: (1) MS2 inactivation, (2) fraction of reacted H2O2, (3) decolourization and (4) NOM mineralization. Multi-response optimization via desirability function based on responses (1) to (3) achieved excellent fitting (0.94 out of 1.0) and following set of optimal experimental conditions: 0.33 g Al/Fe-PILC/L, 3.36 % (H2O2)d â€‹(Feactive/H2O2) = 0.46, giving rise to 92.9 % of MS2 inactivation and 100 % of reacted H2O2 at pH 7.07, 25.0 +/- 0.1 °C, 16.06 mg C/L as starting NOM concentration, and MS2 titer of 106 PFU/mL after just 70 min â€‹of reaction.

Inactivation of carbapenem-resistant Klebsiella pneumoniae by photo-Fenton: Residual effect, gene evolution and modifications with citric acid and persulfate.

The photo-Fenton process application to eliminate carbapenem-resistant Klebsiella pneumoniae, an antibiotic-resistant priority pathogen, was evaluated. Initially, reagents concentration effect was tested and under suitable conditions (5 mg L-1 of Fe2+ and 50 mg L-1 of H2O2) complete bacteria inactivation by action of hydroxyl radical and UVA plus hydrogen peroxide was achieved at 120 min. The process presented a strong residual disinfecting effect when light was turned off at only 20 min. Besides, the cultivability of treated K. pneumoniae in a selective medium containing carbapenem antibiotics was considered. bla-KPC, gene responsible for the resistance, evolution was also assessed. The bacteria response to carbapenem antibiotics was higher as the treatment time increased. In turn, bla-KPC gene remained when K. pneumoniae was completely inactivated (120 min); nevertheless, treatment times longer than 120 min diminished bla-KPC presence. Finally, the photo-Fenton process and its modifications (citric acid addition or persulfate anion instead hydrogen peroxide) were applied to a real hospital wastewater in Colombia. In such complex matrix, the conventional photo-Fenton system reached a moderate disinfection (∼3.5 log-units at 300 min). Meanwhile, in presence of citric acid total inactivation was completed at the same time. Interestingly, the H2O2 substitution by persulfate strongly accelerated the microorganism elimination, achieving the 6-log-units reduction after only 60 min of process action. Thus, the effective elimination of K. pneumoniae from water by the modified photo-Fenton evidenced the potential applicability of this process to limit the proliferation of antibiotic resistant bacteria.

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.

Toxicological aspects of trihalomethanes: a systematic review.

Chlorine is considered the most used chemical agent for water disinfection worldwide. However, water chlorination can lead to by-product generation which can be toxic to humans. The present study aimed to perform a systematic review on the toxicity of trihalomethanes (THMs) through bioindicators of cytotoxicity, genotoxicity, and mutagenicity. The results showed that studies on the effects of THMs on DNA are a current research concern for evaluating the toxicity of the pure compounds and real samples involving several types including water for recreational use, reused water, and drinking water. THMs deleterious effects have been assessed using several biosystems, where the Ames test along with experimental animal models were the most cited. A wide range of THM concentrations have been tested. Nevertheless, DNA damage was demonstrated, highlighting the potential human health risk. Among the studied THMs, chloroform presented a different action mechanism when compared with brominated THMs, with the former being cytotoxic while brominated THMs (bromodichloromethane, bromoform, and dibromochloromethane) were cytotoxic, genotoxic, and mutagenic. The described evidence in this research highlights the relevance of this topic as a human health issue. Nevertheless, research aimed to represent THMs current exposure conditions in a more accurate way would be needed to understand the real impact on human health.

Characterization and antimicrobial activity of silver nanoparticles mycosynthesized by Aspergillus brasiliensis.

AIMS: Since mycosynthesis of metal nanoparticles (NPs) is advertised as a promising and ecofriendly approach. Thus, this study aims to investigate the capability of Aspergillus brasiliensis ATCC 16404 for mycosynthesis of silver NPs (AgNPs). METHODS AND RESULTS: One-factor-at-a-time-technique was used to study the effect of different physicochemical parameters: the reaction time, pH, temperature, different stirring rates, illumination, and finally, the different concentrations of silver nitrate and fungal biomass on the mycosynthesis of AgNPs. The visual observation showed the characteristic brown colour formation due to the bioreduction of Ag+ ions to Ag0 by the mycelial cell-free filtrate (MCFF). The UV/visible spectrophotometric technique displayed a characteristic sharp peak at ʎ440 confirming the mycosynthesis of AgNPs. The zeta potential value -16·7 mV assured the long-term stability of AgNPs and the dynamic light scattering analysis revealed good dispersion and average particle size 77 nm. The energy dispersive X-ray spectroscopy displayed a maximum elemental distribution of silver elements. The X-ray diffraction spectroscopy demonstrated the crystallinity of the mycosynthesized AgNPs. The field emission scanning electron microscope and high-resolution transmission electron microscope revealed monodispersed spherical shaped AgNPs with average particle size of 6-21 nm. The FTIR analysis showed the major peaks of proteins providing the possible role of MCFF in the synthesis and stabilization of the AgNPs. The mycosynthesized AgNPs expressed good biocidal activity against different pathogenic micro-organisms causing some water-related diseases and health problems to local residents. CONCLUSIONS: This study proved that A. brasiliensis ATCC 16404 MCFF has good potential for mycosynthesis of AgNPs, which exhibited good antimicrobial effect on different pathogenic micro-organisms; thus, it can be applied for water disinfection. SIGNIFICANCE AND IMPACT OF THE STUDY: This research provides a helpful insight into the development of a new mycosynthesized antimicrobial agent.

Inactivation, lysis and degradation by-products of Saccharomyces cerevisiae by electrooxidation using DSA.

The yeast Saccharomyces cerevisiae, a microorganism with cell walls resistant to many types of treatments, was chosen as a model to study electrochemical disinfection process using dimensionally stable anodes (DSA). DSA electrodes with nominal composition of Ti/RuO2TiO2 and Ti/RuO2TiO2IrO2 were evaluated in 0.05 mol L-1 Na2SO4 containing yeast. The results showed inactivation about of 100 % of the microorganisms at Ti/RuO2TiO2 by applying 20 and 60 mA cm-2 after 120 min of electrolysis, while a complete inactivation at Ti/RuO2IrO2TiO2 electrode was achieved after 180 min at 60 mA cm-2. When chloride ions were added in the electrolyte solution, 100 % of the yeast was inactivated at 20 mA cm-2 after 120 min of electrolysis, independent of the anode used. In the absence of chloride, the energy consumption (EC) was of 34.80 kWh m-3, at 20 mA cm-2 by using Ti/RuO2TiO2 anode. Meanwhile, in the presence of chloride, EC was reduced, requiring 30.24 and 30.99 kWh m-3 at 20 mA cm-2, for Ti/RuO2TiO2 and Ti/RuO2IrO2TiO2 electrodes, respectively, The best performance for cell lysis was obtained in the presence of chloride with EC of 88.80 kWh m-3 (Ti/RuO2TiO2) and 91.85 kWh m-3 (Ti/RuO2IrO2TiO2) to remove, respectively, 92 and 95 % of density yeast. The results clearly showed that yeast, as a model adopted, was efficiently inactivated and lysed by electrolysis disinfection using DSA-type electrodes.

Desinfecção do sistema de água de equipamentos odontológicos com clorexidina / Disinfection of dental unit waterline with chlorexidine

Introdução: A água utilizada em procedimentos odontológicos pode apresentar- se contaminada, sendo fonte de infecção para profissionais e pacientes. Objetivo: Comparar a efetividade da clorexidina 0,1% e do hipoclorito de sódio 1% na desinfecção do sistema de água de equipamentos odontológicos. Método: Três equipamentos odontológicos sofreram desinfecção com clorexidina; e três, com hipoclorito de sódio mediante acionamento da seringa tríplice durante dois minutos. Amostras de água coletadas antes, após a desinfecção e no final do dia foram analisadas microbiologicamente. Amostras do filtro de abastecimento também foram analisadas. Resultados: As amostras coletadas antes da desinfecção mostraram altos níveis de contaminação (>500 UFC/ml). Após emprego dos desinfetantes, estas apresentaram-se nos padrões recomendados pela American Dental Association – ADA (<200 UFC/ml). A água do filtro de abastecimento também estava dentro dos limites estabelecidos pela ADA. Conclusão: Clorexidina 0,1% mostrou-se tão efetiva quanto hipoclorito de sódio 1% na desinfecção do sistema de água de equipamentos odontológicos.

Introduction: The water used in dental procedures may be contaminated and source of infection for patients and dental staff. Objective: The aim of this study was to compare the effectiveness chlorhexidine 0.1% and sodium hypochlorite 1% in the disinfection of dental unit waterline. Method: Three dental units were disinfection with chlorhexidine and three with sodium hypochlorite by flushing the triple syringe for two minutes. Water samples collected before and after disinfection and in the end of the day were analyzed microbiologically. Samples of the supply filter were also analyzed. Results: Samples collected before disinfection showed high levels of contamination (> 500 CFU / ml). After use of disinfectants, the samples were within the recommended standards by the American Dental Association – ADA (< 200 CFU / ml). The water supply filter was also within the limits established by the ADA. Conclusion: Chlorhexidine 0.1% was effective as sodium hypochlorite 1 % for the disinfection of dental unit waterlines.

Avaliação da eficácia da clorexidina na desinfecção do sistema de água odontológica / Chlorhexidine efficacies evaluation on disinfection of dental unit waterline

Introdução: A água utilizada nos procedimentos odontológicos apresenta-se contaminada e pode causar infecção cruzada. Objetivos: Neste estudo, investigou-se a qualidade da água de equipos odontológicos e a ação de diferentes concentrações de clorexidina na redução da contaminação. Métodos: Os parâmetros de contaminação utilizados foram o da American Dental Association e do Ministério da Saúde. Realizou-se análise bacteriológica em amostras de água de 17 seringas tríplices para verificar a qualidade microbiológica da água tratada ou não com clorexidina in vitro. Testaram-se concentrações de clorexidina 0,4%; 0,2%; 0,1%. Utilizou-se clinicamente clorexidina 0,1% na desinfecção do sistema de água por um minuto em 13 equipos e realizou-se nova análise bacteriológica da água. Resultados: Todos os grupos-controles apresentaram níveis elevados de contaminação, 100% dos grupos tratados in vitro com clorexidina e dos equipos que sofreram desinfecção com clorexidina 0,1% apresentaram-se descontaminados. Conclusão: Clorexidina 0,1% foi efetiva na redução da contaminação da água odontológica.

Introduction: The water used in dental procedures is contaminated and can cause crossed infection. Objective: This study investigates the quality of water on dental units and the action of different concentrations of chlorhexidine in the reduction of this contamination. Method: The contamination parameters used were the American Dental Association and the Brazilian Health State Department. It was executed a bacteriological analysis of water samples from 17 air-water syringes to verify the microbiological quality of water treated or not with chlorhexidine in vitro. It was examined concentrations of 0.4%; 0.2%; 0.1%. One percent chlorhexidine was used, clinically, in disinfection of dental unit waterline for one minute in 13 dental units and a new bacteriological analysis of water was made. Results: All control groups showed high levels of contamination, 100% of groups with chlorhexidine in vitro and all dental units who suffered disinfection with 0.1% chlorhexidine were free of contamination. Conclusion: One percent chlorhexidine was effective in reducing contamination of the dental water.