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 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.

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.

Remoção de carbono orgânico dissolvido de águas filtradas com tratamento complementar por pré-oxidação com ozônio e adsorção em carvão ativado / Removal of dissolved organic carbon in filtered water complemented with treatment by pre-oxidation with ozone and adsorption on activated carbon

Resumo Este trabalho teve como objetivo avaliar as remoções de carbono orgânico dissolvido presente em águas filtradas de estação de tratamento de água com tratamento complementar por pré-oxidação com ozônio e adsorção em carvão ativado granular. Para o estudo de adsorção foi utilizado o método de ensaio rápido em coluna de escala reduzida, com carvão ativado produzido de cascas de coco. Realizou-se a comparação entre as curvas de ruptura para os ensaios com e sem aplicação de ozônio. Os resultados mostraram reduções nas concentrações de carbono orgânico dissolvido no início dos ensaios e após a passagem da água com e sem pré-ozonização pelas colunas ensaio rápido em coluna de escala reduzida seguida de incrementos progressivos das concentrações à medida que se aumentou o volume de leitos tratados. Na fase final dos ensaios, os aumentos de volume de leitos tratados não causaram mudanças significativas nas concentrações efluentes de carbono orgânico dissolvido. O mesmo comportamento foi observado com relação à absorção em radiação ultravioleta a 254 nm. O uso de ozônio previamente à adsorção em carvão ativado granular, usando o método ensaio rápido em coluna de escala reduzida, resultou em maiores reduções na absorbância da luz ultravioleta em 254 nm do que nas concentrações de carbono orgânico dissolvido. As absorbâncias específicas à radiação ultravioleta das amostras ozonizadas foram menores do que as que não receberam ozônio.

Abstract The objective of this study was to evaluate the removal of dissolved organic carbon in filtered water followed by pre-oxidation with ozone and adsorption on granular activated carbon. The rapid small-scale column test was used for the adsorption essays with activated carbon produced from coconut shells. A comparison was made between the breakthrough curves for tests performed with and without pre-oxidation with ozone. The results showed reductions in dissolved organic carbon concentrations after initial passage of water with and without ozone through the rapid small-scale column test column, followed by progressive increases in concentrations along with the number of the bed volumes. In the final phase of the tests, increases in bed volumes did not cause significative changes in effluent dissolved organic carbon concentrations. The same behavior was also observed with respect to ultra-violet absorbance at 254 nm. The use of ozone prior to adsorption on GAC, using the ERCER method, caused greater reductions on UV254 absorbance than in concentrations of dissolved organic carbon. The specific ultraviolet absorbance values of samples that received ozone were lower than those that were not ozonized.

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.

Caracterização da matéria orgânica dissolvida em processos de tratamento de água para consumo humano usando fracionamento rápido / Characterization of dissolved organic matter in drinking water treatment processes using rapid fractionation

RESUMO Matéria orgânica natural (MON) é uma complexa matriz de compostos orgânicos originados de fontes naturais que estão presentes em corpos hídricos. A MON é comprovada precursora de subprodutos da desinfecção (SPD), além de afetar processos de tratamento de água, tais como a coagulação, a desinfecção, a oxidação, a adsorção em carvão ativado e a filtração em membranas. Por essas razões, a redução da MON no tratamento de água para consumo humano é importante. Vários métodos são usados para caracterizar e quantificar a MON, tais como adsorção em resinas e parâmetros de massa. Carbono orgânico total (COT), carbono orgânico dissolvido (COD), absorção na região do ultravioleta (UV254) e absorbância específica de luz ultravioleta (AEUV) são usualmente utilizados como parâmetros de massa. O fracionamento rápido é uma técnica que usa diferentes resinas para separar frações da MON. Nesse contexto, este trabalho teve como objetivo geral caracterizar a matéria orgânica dissolvida (MOD) em processos de tratamento de água para consumo humano usando o método do fracionamento rápido e os parâmetros COD, UV254 e AEUV. Também foram analisados as variáveis turbidez, cor, pH e alcalinidade. Foram avaliados os efeitos dos processos de coagulação, sedimentação, filtração e adsorção em carvão ativado nas frações que formam a MON. Ácidos muito hidrofóbicos (AMH) constituíram a principal fração da MOD na água estudada, havendo redução de 89% entre a água bruta e o efluente do filtro de carvão ativado granular (CAG). A segunda fração predominante foi de ácidos levemente hidrofóbicos (ALH), reduzidos em 83% ao longo do tratamento. Na água bruta, as frações de matérias hidrofílicas carregadas (MHC) e de neutras (MHN) apresentaram concentrações de 0,11 mg L-1 e 0,04 mg L-1, não sendo removidas pelo tratamento.

ABSTRACT Natural organic matter (NOM) is a complex matrix of organic compounds originated from natural sources that are present in water bodies. NOM is a known precursor of disinfection by-products (DBP) and affects drinking water treatment processes such as coagulation, disinfection, oxidation, activated carbon adsorption, and membrane filtration. For these reasons, the reduction of NOM in water treatment is important. Several methods are used to characterize and quantify NOM, such as resin adsorption and mass parameters. The latter include total organic carbon (TOC), dissolved organic carbon (DOC), ultraviolet absorption at 254 nm (UV254), and specific UV absorption (SUVA). Rapid fractionation is a technique that uses different resins to separate NOM fractions. The objective of this study was to characterize dissolved organic matter (DOM) in drinking water treatment processes using rapid fractionation and the parameters DOC, UV254, and SUVA. Turbidity, color, pH, and alkalinity were also analyzed. The effects of coagulation, sedimentation, filtration, and adsorption processes on the fractions forming the NOM were evaluated. Very hydrophobic acids (VHA) constituted the main fraction of DOM in the studied water, with a reduction of 89% between raw water and granular activated carbon filter (GAC) respect to raw water. The second predominant fraction consisted of slightly hydrophobic acids (SHA), reduced by 83% throughout the treatment processes. In raw water, the hydrophilic charged (MHC) and neutral (MHN) fractions showed concentrations of 0.11 and 0.04 mg L-1, which were not removed during treatment.

Utilização de carvão ativado biológico para o tratamento de água para consumo humano / Use of biological activated carbon for drinking water treatment

RESUMO: Este artigo de revisão aborda o uso do carvão ativado biológico no tratamento das águas para consumo humano. O tratamento biológico tem aplicação na redução da instabilidade da água potável causada por matéria orgânica biodegradável e compostos inorgânicos reduzidos presentes em baixas concentrações. A instabilidade tem efeitos prejudiciais à qualidade da água potável, tais como o crescimento de bactérias e a formação de biofilmes na rede de distribuição. O artigo discute as causas e consequências da instabilidade, as medidas de avaliação da matéria orgânica, os mecanismos de formação e controle de biofilmes no carvão ativado granular e as técnicas de avaliação microbiológica e da biodiversidade nos biofilmes. Além disso, analisa-se também a integração do carvão ativado biológico com outros processos usados no tratamento de água para consumo humano.

ABSTRACT: This review article portrays the use of biological activated carbon for drinking water treatment. Biological treatment has applications in the reduction of drinking water instability caused by the presence of low levels of biodegradable organic matter and reduced inorganic compounds. Instability causes deterioration in the quality of drinking water, such as bacterial growth and biofilm formation in the water distribution system. The article discusses the causes and consequences of instability, the measures used for organic matter evaluation, the formation and control mechanisms of biofilms in granular activated carbon and the techniques used for microbiological and biodiversity assessment of biofilms. In addition, it analyzes the integration of biological activated carbon with other processes used for drinking water treatment.

Degradation of the unbiodegradable particulate fraction (XU) from different activated sludges during batch digestion tests at ambient temperature.

One strategy for the management of excess sludge in small wastewater treatment plants (WWTPs) consists in minimizing the excess sludge production by operating the WWTP at very long solids retention times (SRTs > 30 days). A number of recent studies have suggested that sludge minimization at very long SRT results from the degradation of the unbiodegradable particulate fraction (XU) (influent unbiodegradable compounds and endogenous decay products). But the biodegradability of the unbiodegradable particulate fraction has only been evaluated during batch digestion test performed at ambient temperature with sludge fed with synthetic wastewaters. It is not clear to what extent observations made for sludge fed with synthetic influents can be transposed to sludge fed with real influent. The current study thus focused on evaluating the biodegradability of the unbiodegradable particulate fraction for sludge fed with real wastewater. Batch digestion tests (400 days, ambient temperature) were conducted with three different sludges fed with either synthetic or real influents and exposed to aerobic or intermittent aeration conditions. Our results indicate that volatile suspended solids (VSS) decreased even after complete decay of the active biomass (i.e., after 30 days of aerobic batch digestion) indicating that the unbiodegradable particulate fraction is biodegradable. However, very low degradation rates of the unbiodegradable particulate fraction were monitored after day 30 of digestion (0.7-1.7·10(-3) d(-1)). These values were in the lower range of previously published values for synthetic wastewaters (1-7.5·10(-3) d(-1)). The low values determined in our study indicate that the rate could decrease over time or that sludge composition influences the degradability of the unbiodegradable particulate fraction. But our results also demonstrate that extracellular polymeric substances (EPS) have a minor impact on the biodegradability of the unbiodegradable particulate fraction. Overall bound EPS were indeed biodegradable under all conditions and thus did not accumulate in the unbiodegradable particulate fraction. Different bound EPS pools (e.g., cation bound EPS) were associated with specific degradation behaviors. Besides improved mechanistic understanding of sludge degradation processes, our results have implications for the development of decentralized wastewater treatment technologies with on-site reduction of excess sludge.

The effect of different aeration conditions in activated sludge--Side-stream system on sludge production, sludge degradation rates, active biomass and extracellular polymeric substances.

On-site minimization of excess sludge production is a relevant strategy for the operation of small-scale and decentralized wastewater treatment plants. In the study, we evaluated the potential of activated sludge systems equipped with side-stream reactors (SSRs). This study especially focused on how the sequential exposure of sludge to different aeration conditions in the side-stream reactors influences the overall degradation of sludge and of its specific fractions (active biomass, extracellular polymeric substances (EPS), EPS proteins, EPS carbohydrates). We found that increasing the solid retention time from 25 to 40 and 80 days enhanced sludge degradation for all aeration conditions tested in the side-stream reactor. Also, the highest specific degradation rate and in turn the lowest sludge production were achieved when maintaining aerobic conditions in the side-stream reactors. The different sludge fractions in terms of active biomass (quantified based on adenosine tri-phosphate (ATP) measurements), EPS proteins and EPS carbohydrates were quantified before and after passage through the SSR. The relative amounts of active biomass and EPS to volatile suspended solids (VSS) did not changed when exposed to different aeration conditions in the SSRs, which indicates that long SRT and starvation in the SSRs did not promote the degradation of a specific sludge fraction. Overall, our study helps to better understand mechanisms of enhanced sludge degradation in systems operated at long SRTs.

A influência do tempo de detenção celular e decaimento endógeno na estequiometria de reações em processos biológicos de tratamento de águas residuárias: I - Crescimento quimioheterotrófico / The influence of cell detention time and endogenous decay on the stoichiometry reactions of biological processes in wastewater treatment: I - Chemoheterotrophic growth

No metabolismo quimioheterotrófico, um mesmo substrato orgânico é utilizado como fonte de energia e síntese celular. Este artigo apresenta uma metodologia que pode ser usada para calcular a estequiometria do metabolismo quimioheterotrófico considerando o tempo de detenção celular e o decaimento endógeno. O método se baseia em princípios da bioenergética e é útil para o desenvolvimento de balanços de massa em processos biológicos de tratamento de águas residuárias. Também serve para se estimar as necessidades de nutrientes, alcalinidade e aceptores de elétrons para as reações desejadas, assim como a biomassa formada e gases produzidos.

In chemohetrotrophic metabolism, an organic substrate is used as energy and cell synthesis sources. This article presents a methodology that can be used to calculate the stoichiometry of chemoheterotrophic metabolism, considering solids detention time and endogenous decay. The method is based on bioenergetic principles, and is useful for mass balance calculations for biological processes used in wastewater treatment. It is also applied to estimate nutrients, alkalinity and electron acceptor requirements for the intended reactions, as well as biomass and gas production.