RESUMO
Anaerobic bioreactors are an efficient technology for the biodegradation of emerging contaminants in environmental matrices. In this work, a horizontal-flow anaerobic immobilized biomass (HAIB) bioreactor was used to remove caffeine (CAF), which is frequently found in various aqueous matrices. The acrylic bench top bioreactor, with dimensions of 100 × 5.00 cm, was operated with a hydraulic retention time (HRT) of 12 h, during 45 weeks, under mesophilic conditions. The operation was performed in 4 phases: without CAF addition (phase I); CAF spiked at 300 µg L-1 (phase II); CAF at 600 µg L-1 (phase III); and CAF at 900 µg L-1 (phase IV). Samples of bioreactor influent and effluent were analyzed by liquid chromatography/tandem mass spectrometry (LC-MS/MS). The bioreactor removed organic matter (OM) and CAF with efficiencies of 88 and 93%, respectively. The first-order apparent removal constant (Kapp) values for OM and CAF were 0.419 and 0.304 h-1, respectively. Five transformation products (TPs) were identified, with m/z 243, 227, 211, and 181 (two products). The HAIB bioreactor is a suitable system for the removal of CAF present in wastewater, even at a concentration level of µg L-1.
Assuntos
Cafeína , Eliminação de Resíduos Líquidos , Anaerobiose , Eliminação de Resíduos Líquidos/métodos , Biomassa , Cromatografia Líquida , Espectrometria de Massas em Tandem , Reatores BiológicosRESUMO
In this article, a light-emitting diode (LED)-based photoreactor was designed and evaluated for degradation of the antibiotic sulfathiazole (STZ), using heterogeneous photo-Fenton process with an iron ore residue as catalyst. The effects of the type of magnetic stirrer bar, use of baffles, rotation speed, and type and intensity of irradiation source were evaluated. The results showed that the degradation of STZ was strongly influenced by rotation speed (1100 rpm) and that the use of an octagonal stirrer bar favoured high dispersion and greater contact of the catalyst with the reaction medium. Although the presence of baffles had little influence on STZ degradation, their use enabled good dispersion of the catalyst (due to axial flow) and eliminated the vortex formed at high stirring speeds. It was found that the iron mining residue could be activated by UV LEDs, visible light LEDs, and black light irradiation, with similar degradation efficiencies achieved. Using the LEDs, STZ concentrations below the detection limit were obtained after 40 min, with power consumption 38-fold (UV LEDs) and 22-fold (visible light LEDs) lower than required for black light irradiation. The results demonstrated the advantages of the use of LED devices as irradiation systems in heterogeneous photo-Fenton processes.