Efficient removal of triclosan from water through activated carbon adsorption and photodegradation processes.

This study investigated the application of adsorption with activated carbons (ACs) and photodegradation to reduce the concentration of triclosan (TCS) in aqueous solutions. Concerning adsorption, ACs (Darco, Norit, and F400) were characterised and batch experiments were performed to elucidate the effect of pH on equilibrium. The results showed that at pH = 7, the maximum adsorption capacity of TCS onto the ACs was 18.5 mg g-1 for Darco, 16.0 mg g-1 for Norit, and 15.5 mg g-1 for F400. The diffusional kinetic model allowed an adequate interpretation of the experimental data. The effective diffusivity varied and increased with the amount of TCS adsorbed, from 1.06 to 1.68 × 10-8 cm2 s-1. In the case of photodegradation, it was possible to ensure that the triclosan molecule was sensitive to UV light of 254 nm because the removal was over 80 % using UV light. The removal of TCS increased in the presence of sulfate radicals. It was possible to identify 2,4-dichlorophenol as one of the photolytic degradation products of triclosan, which does not represent an environmental hazard at low concentrations of triclosan in water. These results confirm that the use of AC Darco, Norit, and F400 and that photodegradation processes with UV light and persulfate radicals are effective in removing TCS from water, reaching concentration levels that do not constitute a risk to human health or environmental hazard. Both methods effectively eliminate pollutants with relatively easy techniques to implement.

A pilot-scale electrocoagulation-treatment wetland system for the treatment of landfill leachate.

In the present study, the technical feasibility of an electrocoagulation-treatment wetland continuous flow system, for the removal of organic matter from landfill leachate (LL), was evaluated. The response surface methodology (MSR) was used to assess the individual and combined effects of the applied potential and distance between electrodes, on the removal efficiency and optimization of the electrocoagulation process. The hybrid treatment wetland system consisted of a vertical flow system coupled to a horizontal subsurface flow system, both planted with Canna indica. For a chemical oxygen demand (COD) concentration - without pretreatment of 5142.8 ± 2.5 mg L-1, the removal percentage for the electrocoagulation system was 79.4 ± 0.16%, under the optimal working conditions (Potential: 20 V; Distance: 2.0 cm). The COD removal efficiency in the treatment wetland with Canna indica showed a dependence with the hydraulic retention time, reaching 59.2 ± 0.2 % over 15 days. The overall efficiency of the system was about 91.5 ± 0.02 % removal of COD. In addition, a decrease in the biochemical oxygen demand (94.8 ± 0.14%) and total suspended solids (88.2 ± 0.22%), also related to the contamination levels of the LL, were obtained. This study, for the first time, shows that the coupling of electrocoagulation together with a treatment wetland system is a good alternative for the removal of organic contaminants present in LL.

Pollutants of emerging concern in tourist beaches of Guerrero, Mexico: A first approach to sources.

The presence of Emerging Pollutants (EPs) on the beaches of Acapulco, Mexico, is evaluated for the first time. Samples were taken from the discharge of the wastewater treatment plant at Olvidada beach, and at three beaches that receive contributions from different streams that cross through the city in Santa Lucia Bay (SLB). Using solid phase extraction and gas chromatography/mass spectrometry, 77 EPs were identified. A semiquantitative evaluation of their concentrations were made using the relative areas of the chromatographic peaks, showing that the contamination of the beaches of SLB is mainly due to the pollutants going into the streams of the micro-basins. A statistical factor analysis of all the EPs allowed differentiation of the sampling points, reducing the number of variables, which benefits future analytical determinations in the study area. Due to the toxicological characteristics of the compounds found, their presence on public-use beaches represents a risk to human health.

Valorization of Sargassum Biomass as Potential Material for the Remediation of Heavy-Metals-Contaminated Waters.

Sargassum algae has become a major environmental issue due to its abundance in the Pacific Ocean with hundreds of tons reaching the beaches of the Mexican Caribbean every year. This generates large quantities of decomposing organic matter that have a negative impact on the region's economy and ecosystems. Sargassum valorization has turned out to be a fundamental aspect to mitigate its environmental impact. This study proposes the use and application of untreated Sargassum biomass for the decontamination of waters polluted with lead (Pb) and cadmium (Cd) through single and binary adsorption tests. Physicochemical and textural properties examined by SEM, XRD, and FT-IR elucidated that Sargassum biomass is viable to be used as a potential environmental benign adsorbent, exhibiting Cd(II) and Pb(II) adsorption capacities as high as 240 mg g-1 and 350 mg g-1, respectively, outperforming conventionally used adsorbents. This is attributed to its morphology, favorable surface charge distribution, and the presence of -OH and -COH groups. A strong affinity between the biomass and metal pollutants was evidenced by a thermodynamics study, showing a spontaneous and endothermic process. This work sets a practical route for the utilization of the Sargassum biomass, demonstrating its applicability as a potential material for heavy-metal-polluted water remediation, making a substantial contribution to a circular economy system.

Polycyclic aromatic hydrocarbons and heavy metals in the Cispata Bay, Colombia: A marine tropical ecosystem.

The concentrations of polycyclic aromatic hydrocarbons and heavy metals were evaluated in shallow sediments, water, fish and seabird samples from the Cispata Bay, Colombia. The heavy metals concentrations in the sediment was in the following order: Cu>Pb>Hg>Cd. The heavy metal concentration was different (p<0.05) in juvenile and adult birds. High concentrations of mercury were registered in the seabird (10.19±4.99mgkg-1) and fish (0.67µgg-1) samples. The total concentration of polycyclic aromatic hydrocarbons ranged from 7.0-41ngg-1 in sediment, 0.03-0.34ngmL-1 in water samples, 53.24ngg-1 in fish, and 66ngg-1 in seabirds. The high concentrations of heavy metals in seabirds may be explained by their feeding habits. The presence of polycyclic aromatic hydrocarbons in the Cispata Bay may be due to hydrocarbon spills during oil transport at the nearby oil port.

Total mercury concentrations in fish from Urrá reservoir (Sinú river, Colombia). Six years of monitoring / Concentraciones de mercurio total en peces del embalse Urrá (río Sinú, Colombia). Seis años de monitoreo

Objective. The aim of this study was to monitor the total mercury (T-Hg) concentrations in fish from the Urrá reservoir, after impoundment. Materials and methods. Five fish species at different trophic levels were sampled from 2004 to 2009 and analyzed by cold-vapor atomic absorption spectroscopy for T-Hg concentrations in muscle tissue. Water quality parameters were evaluated. Results. The highest (1.39±0.69 µg/g ww) and lowest (0.15±0.02 µg/g ww) T-Hg concentrations were detected in Hoplias malabaricus (piscivorous) and Cyphocharax magdalenae (iliophagous/detritivorous) respectively, whereas Leporinus muyscorum (omnivorous) had an intermediate level (0.40±0.11 µg/g ww). The organic matter content in the water increased with time and depth, whereas dissolved oxygen and pH decreased. A covariance analysis (with fish length as a covariate) shows a steady increase of T-Hg levels in all the studied species after impoundment. Conclusions. The T-Hg concentrations in the evaluated fish species, increased after impoundment. The water quality variables showed conditions favoring Hg methylation and its biomagnification, this last was evident in the fish food chain of the reservoir.

Objetivo. El objetivo de este estudio fue monitorear las concentraciones de mercurio total (Hg-T) en peces del embalse Urrá después del represamiento. Materiales y métodos. Cinco especies de peces de diferentes niveles tróficos fueron muestreadas de 2004 a 2009 y analizadas por espectroscopia de absorción atómica para las concentraciones de Hg-T en tejido muscular. Se evaluaron parámetros de calidad de agua. Resultados. Las mayores (1.39±0.69 µg/g ph) y menores (0.15±0.02 µg/g ph) concentraciones de Hg-T fueron detectadas en Hoplias malabaricus (piscívoro) y Cyphocharax magdalenae (iliófago/detritívoro) respectivamente, mientras que Leporinus muyscurum (omnívoro) tuvo un nivel intermedio (0.40±0.11 µg/g ph). El contenido de materia orgánica en el agua se incrementó con el tiempo y la profundidad, mientras que el oxígeno disuelto y el pH disminuyeron. Un análisis de covarianza (con la longitud del pez como covariante) mostró un incremento sostenido de los niveles de Hg-T en todas las especies evaluadas después del represamiento. Conclusiones. Las concentraciones de Hg-T en las especies de peces evaluadas, incrementaron después del represamiento. Las variables de calidad de agua mostraron condiciones favorables para la metilación del Hg y su biomagnificación, estos último fue evidente en la cadena alimenticia de los peces del embalse.