Showing papers by "Mônica Maria Diniz Leão published in 2019"

Degradation of carbendazim in water via photo-Fenton in Raceway Pond Reactor: assessment of acute toxicity and transformation products

Abstract: This study aimed at investigating the degradation of fungicide carbendazim (CBZ) via photo-Fenton reactions in artificially and solar irradiated photoreactors at laboratory scale and in a semi-pilot scale Raceway Pond Reactor (RPR), respectively. Acute toxicity was monitored by assessing the sensibility of bioluminescent bacteria (Aliivibrio fischeri) to samples taken during reactions. In addition, by-products formed during solar photo-Fenton were identified by liquid chromatography coupled to mass spectrometry (UFLC-MS). For tests performed in lab-scale, two artificial irradiation sources were compared (UVλ > 254nm and UV-Visλ > 320nm). A complete design of experiments was performed in the semi-pilot scale RPR in order to optimize reaction conditions (Fe2+ and H2O2 concentrations, and water depth). Efficient degradation of carbendazim (> 96%) and toxicity removal were achieved via artificially irradiated photo-Fenton under both irradiation sources. Control experiments (UV photolysis and UV-Vis peroxidation) were also efficient but led to increased acute toxicity. In addition, H2O2/UVλ > 254nm required longer reaction time (60 minutes) when compared to the photo-Fenton process (less than 1 min). While Fenton’s reagent achieved high CBZ and acute toxicity removal, its efficiency demands higher concentration of reagents in comparison to irradiated processes. Solar photo-Fenton removed carbendazim within 15 min of reaction (96%, 0.75 kJ L−1), and monocarbomethoxyguanidine, benzimidazole isocyanate, and 2-aminobenzimidazole were identified as transformation products. Results suggest that both solar photo-Fenton and artificially irradiated systems are promising routes for carbendazim degradation.

Reestruturação na forma do tratamento de efluentes têxteis: uma proposta embasada em fundamentos teóricos

Abstract: Resumo As industrias texteis utilizam grandes quantidades de agua nos processos de tingimento e beneficiamento das fibras, gerando volumes elevados de efluentes contendo corantes, surfactantes, ions inorgânicos, agentes umectantes, entre outros. O principal impacto ambiental desses efluentes esta relacionado com a absorcao de luz no meio aquatico, o que interfere na fotossintese de plantas e algas. Sendo assim, e relevante um planejamento ambiental propiciando o aumento da remocao dos corantes, reducao das perdas no tingimento e reuso da agua. Neste trabalho, foram realizados estudos visando a proposicao de medidas de contencao dos riscos ambientais e contribuir para melhor aderencia aos conceitos da ecoeficiencia no setor textil atraves de um estudo de caso. Os dados foram coletados em uma empresa localizada na area de abrangencia do Rio Doce, Minas Gerais, sendo proposta a inclusao do Processo Oxidativo Avancado (POA) e ultrafiltracao associada ao tratamento convencional para diminuicao do volume gerado e caracteristicas refratarias, e dessa forma oportunizando o reuso da agua. Identificou-se a necessidade do monitoramento da toxicidade do lodo gerado em funcao da presenca de teores de metais toxicos visando seu reaproveitamento, sendo sugerido estudo para incorporacao da massa em argila para fabricacao de blocos cerâmicos de vedacao utilizados na construcao civil.

Enhanced biodiesel industry wastewater treatment via a hybrid MBBR combined with advanced oxidation processes: analysis of active microbiota and toxicity removal.

Abstract: In the present study, a multistage route is proposed for the treatment of biodiesel industry wastewater (BWW) containing around 1000 mg L−1 of total organic carbon (TOC), 3500 mg L−1 of chemical oxygen demand (COD), and 1325 mg L−1 of oil and grease. Initially, BWW aerobic biodegradability was assessed via Zhan-Wellens biodegradability test to confirm the appropriate treatment route. Then, a hybrid moving bed bioreactor (MBBR) system was chosen as the first treatment stage. The hybrid MBBR achieved 69 and 68% removal of COD and TOC removals, respectively, and provided great conditions for biomass growth. The bacterial community present in the hybrid MBBR was investigated by PCR-DGGE and potential biodegraders were identified such as: members of Desulfuromonadales, Nocardioidaceae and Pseudomonadaceae. Since biodegradation in the hybrid MBBR alone was unable to meet quality requirements, advanced oxidation processes, such as Fenton and photo-Fenton, were optimized for application as additional treatment stages. Physicochemical properties and acute toxicity of BWW were analyzed after the multistage routes: hybrid MBBR + Fenton, hybrid MBBR + photo-Fenton and hybrid MBBR + UV-C254nm/H2O2. Hybrid MBBR + Fenton or photo-Fenton showed overall COD removal efficiencies greater than 95% and removed acute toxicity, thus being appropriate integrated routes for the treatment of real BWW.

Growth and differential salinity reduction between Portulaca oleracea and Eichhornia crassipes in experimental hydroponic units.

Abstract: We evaluated the salinity reduction of the experimental saline solutions through ion uptake capacity of two plant species, purslane (PU) (Portulaca oleraceae) and water hyacinth (WH) (Eichhornia crassipes). These species were grown in experimental hydroponic units simulating a floating system. The hydroponic system contained treatments with three nutrient solutions identified as A1, A2, and A3 composed of fixed concentrations of macro and micronutrients to which three different concentrations of sodium chloride had been added. After the experimental period, physicochemical and volume changes in the saline nutrient solutions were evaluated. The relative growth rate results were similar for both plant species, but with lower consumption of hydroponic nutrient solutions by PU. Despite higher solution volume loss, regardless of the nutrient solution applied, WH had greater weekly estimated potential of reduction of macronutrients (calcium and magnesium; >50%); however, PU showed the best weekly potential reduction of sodium (36%) with solution A2. Therefore, both plants present potential to be used for salinity reduction in the natural conditions.

Oxidation of ethylenethiourea in water via ozone enhanced by UV-C: identification of transformation products

Abstract: Ethylenethiourea (ETU) is a toxic degradation product of one class of fungicide which is largely employed in the world, the ethylenebisdithiocarbamates. In this study, ETU was degraded by ozonation enhanced by UV-C light irradiation (O3/UV-C) in aqueous medium. Degradation experiments were conducted at natural pH (6.8) and neutral pH (7.0, buffered). ETU was promptly eliminated from the reactive medium during ozonation in the presence and absence of light. Within the first few minutes of reaction conducted in natural pH, the pH decreased quickly from 6.8 to 3.0. Results show that ETU mineralization occurs only in the reaction conducted in neutral pH and that it takes place in a higher rate when enhanced by UV-C irradiation. Main intermediates formed during the O3/UV-C experiments in different conditions tested were also investigated and three different degradation mechanisms were proposed considering the occurrence of direct and indirect ozone reactions. At pH 7, ethylene urea (EU) was quickly generated and degraded. Meanwhile, at natural pH, besides EU, other compounds originated from the electrophilic attack of ozone to the sulfur atom present in the contaminant molecule were also identified during reaction and EU was detected within 60 min of reaction. Results showed that ozonation enhanced by UV-C promotes a faster reaction than the same system in the absence of light, and investigation of the toxicity is recommended.