Preliminary insights on the development of a continuous-flow solar system for the photocatalytic degradation of contaminants of emerging concern in water.

The ubiquity and impact of pharmaceuticals and pesticides, as well as their residues in environmental compartments, particularly in water, have raised human and environmental health concerns. This emphasizes the need of developing sustainable methods for their removal. Solar-driven photocatalytic degradation has emerged as a promising approach for the chemical decontamination of water, sparking intensive scientific research in this field. Advancements in photocatalytic materials have driven the need for solar reactors that efficiently integrate photocatalysts for real-world water treatment. This study reports preliminary results from the development and evaluation of a solar system for TiO2-based photocatalytic degradation of intermittently flowing water contaminated with doxycycline (DXC), sulfamethoxazole (SMX), dexamethasone (DXM), and carbendazim (CBZ). The system consisted of a Fresnel-type UV solar concentrator that focused on the opening and focal point of a parabolic trough concentrator, within which tubular quartz glass reactors were fixed. Concentric springs coated with TiO2, arranged one inside the other, were fixed inside the quartz reactors. The reactors are connected to a raw water tank at the inlet and a check valve at the outlet. Rotating wheels at the collector base enable solar tracking in two axes. The substances (SMX, DXC, and CBZ) were dissolved in dechlorinated tap water at a concentration of 1.0 mg/L, except DXM (0.8 mg/L). The water underwent sequential batch (~ 3 L each, without recirculation) processing with retention times of 15, 30, 60, 90, and 120 min. After 15 min, the degradation rates were as follows: DXC 87%, SMX 35.5%, DXM 32%, and CBZ 31.8%. The system processed 101 L of water daily, simultaneously removing 870, 355, 256, and 318 µg/L of DXC, SMX, DXM, and CBZ, respectively, showcasing its potential for real-world chemical water decontamination application. Further enhancements that enable continuous-flow operation and integrate highly effective adsorbents and photocatalytic materials can significantly enhance system performance.

Global prevalence of potentially pathogenic free-living amoebae in sewage and sewage-related environments-systematic review with meta-analysis.

Free-living amoebae (FLA) include amphizoic microorganisms important in public health, widely isolated from air, water, and soil. However, its occurrence in sewage-related environments still needs to be systematically documented. This study summarizes the occurrence of FLA in sewage-related environments through a systematic review with meta-analysis. A total of 1983 scientific article were retrieved from different databases, of which 35 were selected and analyzed using a random effects forest plot model with a 95% confidence interval (IC). The pooled overall prevalence of FLA in sewage across 12 countries was 68.96% (95% IC = 58.5-79.42). Subgroup analysis indicates high prevalence in all environments analyzed, including sewage water from the sewage treatment plant (81.19%), treated sewage water (75.57%), sewage-contaminated water (67.70%), sediment contaminated by sewage (48.91%), and sewage water (47.84%). Prevalence values of Acanthamoeba spp., Hartmanella/Vermamoeba spp., and Naegleria spp. are 47.48%, 28.24%, and 16.69%, respectively. Analyzing the species level, the distribution is as follows: Acanthamoeba palestinensis (88%), A. castellanii (23.74%), A. astronyxis (19.18%), A. polyphaga (13.59%), A. culbertsoni (12.5%), A. stevensoni (8.33%), A. tubiashi (4.35%) and A. hatchetti (1.1%), Naegleria fowleri (28.4%), N. gruberi (25%), N. clarki (8.33%), N. australiensis (4.89%) and N. italica (4.29%), Hartmannella/Vermamoeba exundans (40%) and H.V. vermiform (32.61%). Overall, our findings indicate a high risk associated with sewage-related environments, as the prevalence of FLA, including pathogenic strains, is high, even in treated sewage water. The findings of this study may be valuable both for risk remediation actions against amoebic infections and for future research endeavors.

Agar dehydration: a simple method for long-term storage of Acanthamoeba spp. collection at room temperature.

This study describes dehydration of agar containing cysts as a novel and inexpensive method for long-term storage of Acanthamoeba spp. collections at room temperature. Five hundred microliters of axenically cultured Acanthamoeba spp. trophozoites (106 cells/mL) in PYG media or 150 µl of amoeba suspension (106 cells or cysts/mL) from monoxenic plate culture was spread onto the surface of non-nutritive agar (NNA, 2-3-mm thick) without or with a layer of heat-inactivated Escherichia coli, respectively. The plates were sealed and incubated at 30 °C. After the encystment, the Parafilm® was removed, and the plates were kept at the same temperature until the NNA was completely dehydrated. The dehydrated cyst-containing NNA was cut in rectangles and stored in airtight tubes at room temperature for up to 3 years. Cyst viability was assessed by inoculating them in fresh NNA with a layer of E. coli and in PYG followed by incubation at 30 °C. One hundred percent of samples from all specimens (19) stored over the 3 years allowed new cultures to be re-established; however, two strains showed reduced viability, at 66.7% and 62.5%, after 2 years of room temperature storage. One hundred percent of the cyst samples produced axenically and maintained in dry NNA allowed the re-establishment of axenic cultures through direct incubation in PYG, with excystment occurring within 24 or 48 h. For the first time, we report the dehydration of cyst-containing agar as an economical and effective method for the long-term storage of Acanthamoeba spp. collections at room temperature. It enables the creation of large collections using reduced space and economical transport of Acanthamoeba strains, in addition to allowing better organization of the collection.

Gallium maltolate, a promising low toxicity drug with curative effect on mice chronically infected with Trypanosoma evansi.

Trypanosoma evansi is a flagellate protozoan that infects a wide range of hosts, especially horses. Clinically, the infection is characterized by rapid weight loss, anemia and mobility disorders. This study evaluated the efficacy of treatment gallium maltolate (GaM) in rats infected with T. evansi in the acute and chronic phases of the disease and its influence on the enzyme and blood parameters. 48 animals (Rattus norvegicus) were divided into 8 groups (A-H) of 6 animals each, namely: A: (negative control) uninfected; B: acutely infected positive control; C: chronically infected positive control; D: acutely infected, treated with GaM for 7 days post infection (p.i.); E: acutely infected treated with GaM for 3 days before infection (b.i) and 7 days p.i.; F: chronically infected, treated with GaM for 7 days p.i.; G: chronically infected, treated with GaM for 3 days b.i. and 7 days p.i.; and H: uninfected treated with GaM for 10 days. Acute infected animals (B, D and E) had a progressive increase in parasitemia and were died or euthanized before completing treatment days (5th days p.i.) as they had high parasitemia (over 100 field trypanosomes in the blood smear). Thus, it can be concluded that GaM was not effective against an acute infection. In untreated chronically infected animals (C) the parasitemia also increased progressively and they were euthanized on the 7th day p.i.. The chronically infected and treated animals (F and G) showed low parasitemia and after treatment became negative, showing no trypanosomes in the bloodstream until the 50th day of the experiment. Thus, we conclude that GaM was effective against chronic infections. In uninfected and treated animals (H) hematological, biochemical and enzymatic parameters had no significant changes when compared to the negative control group (A) demonstrating the low toxicity of GaM.

Global prevalence of free-living amoebae in solid matrices - A systematic review with meta-analysis.

The ubiquitous free-living amoebae (FLA) are microorganisms of significant medical, sanitary, and ecological importance. However, their characterization within solid matrices such as soil, dust, sediment, mud, sludge, and compost remain to be systematized. In this study, we conducted a systematic review with meta-analysis to explore the global distribution of FLA in solid matrices. From the analysis of 104 out of 4,414 scientific articles retrieved from different databases, it was found that the general global prevalence of FLA in solid matrices was of 55.13% (95% confidence interval (CI) 49.32-60.94). Specifically, FLA prevalence was high in soil (72.40%, 95% CI 69.08-75.73), sediment (57.91%, 95% CI 50.01-65.81), mud (52.90%, 95% CI 24.01-81.78), dust (48.60%, 95% CI 43.00-54.19), and sewage sludge (40.19%, 95% CI 30.68-49.70). In aerosols it was comparatively lower (17.21%, 95% CI 12.76-21.66). Acanthamoeba spp. (52.23%) and Hartmanella/Vermamoeba spp. (36.06%) were found to be more prevalent, whereas Naegleria spp. (34.98%) and Balamuthia spp. (27.32%) were less prevalent. The distribution of the highest global prevalence values for species of Acanthamoeba spp., considering different publication periods of the studies, is as follows: A. hatchetti (51.46%), A. rhysodes (47.49%), A. polyphaga (36.37%), A. culbertsoni (34.31%), A. castellanii (34.21%), and A. lenticulata (32.82%). For other FLA species, the distribution is: Hartmannella/Vermamoeba vermiformis (91.57%), Naegleria fowleri (42.32%), Naegleria gruberi (32.39%), and Balamuthia mandrillaris (25%). The most prevalent Acanthamoeba genotypes were T4 (33.38%) and T3 (23.94%). Overall, the global prevalence of FLA in solid matrices is as high as or greater than that reported in water by previous systematic reviews. Thus, actions aimed at reducing exposure to FLA or exploring their ecological dynamics should consider not only water but also the various solid matrices. The finding outlined here can provide valuable insights for such actions, e.g., informing on the level of exposure to FLA, or on the microbial biodiversity of specific environmental compartments.

A challenge in washing water with the sun: 24h of SODIS fails to inactivate Acanthamoeba castellanii cysts and internalized Pseudomonas aeruginosa under strong real sun conditions.

Despite access to drinking water being a basic human right, the availability of safe drinking water remains a privilege that many do not have and as a result, many lives are lost each year due to waterborne diseases associated with the consumption of biologically unsafe water. To face this situation, different low-cost household drinking water treatment technologies (HDWT) have been developed, and among them is solar disinfection (SODIS). Despite the effectiveness of SODIS and the epidemiological gains being consistently documented in the literature, there is a lack of evidence of the effectiveness of the batch-SODIS process against protozoan cysts as well as their internalized bacteria under real sun conditions. This work evaluated the effectiveness of the batch-SODIS process on the viability of Acanthamoeba castellanii cysts, and internalized Pseudomonas aeruginosa. Dechlorinated tap water contaminated with 5.6 × 103 cysts/L, contained in PET (polyethylene terephthalate) bottles, was exposed for 8 h a day to strong sunlight (531-1083 W/m2 of maximum insolation) for 3 consecutive days. The maximum water temperature inside the reactors ranged from 37 to 50 °C. Cyst viability was assessed by inducing excystment on non-nutrient agar, or in water with heat-inactivated Escherichia coli. After sun exposure for 0, 8, 16 and 24 h, the cysts remained viable and without any perceptible impairment in their ability to excyst. 3 and 5.5 log CFU/mL of P. aeruginosa were detected in water containing untreated and treated cysts, respectively, after 3 days of incubation at 30 °C. The batch-SODIS process is unable to inactivate A. castellanii cysts as well as its internalized bacteria. Although the use of batch SODIS by communities should continue to be encouraged, SODIS-disinfected water should be consumed within 3 days.

Occurrence of Naegleria fowleri and their implication for health - a look under the One Health approaches.

One Health approaches are becoming increasingly necessary in the world we live in. Human beings, animals, plants and the environment are intrinsically interconnected and when some intervention occurs, mainly through the action of man himself, everyone suffers the consequences. The objective of this review was to collect data about the occurrence and dispersion of Naegleria fowleri, an amphizoic free-living amoeba, and its implications for health approaches through the One Health concept. N. fowleri is an opportunistic amoeba, better known as brain-eating amoeba, which causes Primary Amoebic Meningoencephalitis. This amoeba is widely distributed around the world, being isolated from different matrices of natural or anthropogenic environments with temperatures above 30 °C with an upper limit of 45-46 °C. Highly lethal, it has claimed numerous humans patients and only five people have survived the disease so far. Our results indicate that climate change plays a major role in the growth and dispersion of the pathogen in the environment, causing damage to humans and animals. Changes in temperature, antimicrobial resistance, possible transport of other microorganisms by the amoeba, conventional treatments with chlorination, among others, were addressed in our study and should be considered in order to raise questions and possible solutions to this problem that involves health as a whole. The diagnostic methods, prospection of new anti-Naegleria drugs and the control of this parasite in the environment are specific and urgent issues. We know that the human-animal-plants-environment spheres are inseparable, so it is necessary to turn a directed look at the One Health approaches related to N. fowleri.

Epidemiological and immunological gains from solar water disinfection: Fact or wishful thinking?

OBJECTIVE: There is still no consensus on the impact of using solar disinfection (SODIS) to reduce the prevalence of waterborne gastrointestinal diseases. The reported reduction in diarrhoea prevalence among SODIS users has been attributed to the consumption of water free of viable pathogens. However, it has also been suggested that ingestion of SODIS-inactivated pathogens may induce protective immunological changes that may also contribute to a reduction in the frequency of diarrhoea. The present study aimed to critically review the epidemiological and immunological gains of using SODIS. METHODS: We critically reviewed 22 articles published in English, selected from 2118 records systematically retrieved from the databases. RESULTS: All trials (except one) reported a significant reduction in diarrhoea prevalence among children using SODIS, but some of the data from trials report contrary findings. All in vitro and in vivo assays indicate that SODIS-inactivated pathogenic bacteria have the potential to induce immunological alterations that may result in protective immunological effects. Studies with a low risk of bias are still awaited to confirm the ability to use SODIS to reduce the prevalence of diarrhoea. CONCLUSION: Reducing the prevalence of diarrhoea depends on the success of SODIS delivery strategies in inducing behavioural changes in communities that result in the production of SODIS-compliant outcomes. The results of trials reporting a reduction in the prevalence of diarrhoea due to the use of SODIS seem to support the hypothesis of the contribution of the protective immunological effect against diarrhoea in SODIS users.

Prevalence of free-living amoebae in swimming pools and recreational waters, a systematic review and meta-analysis.

Free-living amoebae (FLA) are cosmopolitan microorganisms known to be pathogenic to humans who often have a history of contact with contaminated water. Swimming pools and recreational waters are among the environments where the greatest human exposure to FLA occurs. This study aimed to determine the prevalence of FLA in swimming pools and recreational waters, through a systematic review and meta-analysis that included studies published between 1977 and 2022. A total of 106 studies were included and an overall prevalence of FLA in swimming pools and recreational waters of 44.34% (95% CI = 38.57-50.18) was found. Considering the studies published up to 2010 (1977-2010), between 2010 and 2015, and those published after 2010 (> 2010-2022), the prevalence was 53.09% (95% CI = 43.33-62.73) and 37.07% (95% CI = 28.87-45.66) and 45.40% (95% CI = 35.48-55.51), respectively. The highest prevalence was found in the American continent (63.99%), in Mexico (98.35%), and in indoor hot swimming pools (52.27%). The prevalence varied with the variation of FLA detection methods, morphology (57.21%), PCR (25.78%), and simultaneously morphology and PCR (43.16%). The global prevalence by genera was Vahlkampfia spp. (54.20%), Acanthamoeba spp. (33.47%), Naegleria spp. (30.95%), Hartmannella spp./Vermamoeba spp. (20.73%), Stenamoeba spp. (12.05%), and Vannella spp. (10.75%). There is considerable risk of FLA infection in swimming pools and recreational waters. Recreational water safety needs to be routinely monitored and, in case of risk, locations need to be identified with warning signs and users need to be educated. Swimming pools and artificial recreational water should be properly disinfected. Photolysis of NaOCl or NaCl in water by UV-C radiation is a promising alternative to disinfect swimming pools and artificial recreational waters.

Solar disinfection (SODIS) technologies as alternative for large-scale public drinking water supply: Advances and challenges.

Gastrointestinal waterborne diseases, continue to stand out among the most lethal diseases in developing countries, because of consuming contaminated water taken from unsafe sources. Advances made in recent decades in methods of solar water disinfection (SODIS) have shown that SODIS is an effective and inexpensive method of providing drinking water, capable of substantially reducing the prevalence and mortality of waterborne diseases. The increased impact of SODIS in communities lacking drinking water services depends on a successful upgrade from conventional SODIS (based on PET bottle reactors) in high flow continuous flow systems for solar water disinfection (CFSSWD). This review aimed to identify the main limitations of conventional SODIS that hinder its application as a large-scale drinking water supply strategy, and to propose ways to overcome these limitations (without making it economically inaccessible) based on the current frontier of advances technological. It was found that the successful development of the CFSSWD depends on overcoming the current limitations of conventional SODIS and the development of systems whose configurations allow combining the properties of solar pasteurization (SOPAS) and SODIS. Different improvements need to be made to the main components of the CFSSWD, such as increasing the performance of solar radiation collectors, photo and thermal reactors and heat exchangers. The integration of disinfection technologies based on photocatalytic and photothermal nanomaterials also needs to be achieved. The performance evaluation of the CFSSWD should be made considering resistant microorganisms, such as the environmental resistance structures of bacteria or protozoa (spores or (oo)cysts) as targets of disinfection approaches.

A new continuous-flow solar water disinfection system inactivating cysts of Acanthamoeba castellanii, and bacteria.

Solar water disinfection (SODIS) is an effective and inexpensive microbiological water treatment technique, applicable to communities lacking access to safely managed drinking water services, however, the lower volume of treated water per day (< 2.5 L per batch) is a limitation for the conventional SODIS process. To overcome this limitation, a continuous-flow solar water disinfection system was developed and tested for inactivation of Acanthamoeba castellanii cysts and Escherichia coli, Salmonella Typhimurium, Enterococcus faecalis, and Pseudomonas aeruginosa. The system consisted of a solar heater composed of a cylindrical-parabolic concentrator and a UV irradiator formed by a fresnel-type flat concentrator combined with a cylindrical-parabolic concentrator. Deionized water with low or high turbidity (< 1 or 50 nephelometric turbidity unit (NTU) where previously contaminated by 108 Cysts/L or 105-106 CFU/mL of each of four bacterial species. Then was pumped from the heating tank flowing through the heater and through the UV irradiator, then returning to the heating tank, until reaching 45, 55, 60 or 70 °C. The water was kept at the desired temperature, flowing through the UV irradiator for 0.5 and 10 min. Trophozoites were not recovered from cysts (during 20 days of incubation) when water with < 1 NTU was exposed to UV and 60 °C for 0.5 min. In water with 50 NTU, the same result was obtained after 10 min. In water with < 1 NTU, the inactivation of all bacteria was achieved when the water with < 1 NTU was exposed to 55 °C and UV for 0.5 min; in water, with 50 NTU the same result was achieved by exposure to 60 °C and UV for 0.5 min. The prototype processes 1 L of water every 90s. The system is effective and has the potential to be applied as an alternative to the large-scale public drinking water supply.