RESUMO
In this work, the effect of supporting electrolytes on the simultaneous electrochemical oxidation of the pharmaceuticals sulfamethoxazole (SMX), propranolol (PRO), and carbamazepine (CBZ) in aqueous solutions has been studied. Based on the identified by-products, the degradation mechanisms were proposed and the acute toxicity was evaluated for each electrolyte. Assays were carried out in batch mode in a 2 L undivided reactor using a niobium coated with boron-doped diamond (Nb/BDD) mesh anode and Ti cathode at 2.5 A in presence of different supporting electrolytes (Na2SO4, NaCl, or NaBr) at the same concentration of 7 mM. The degradation rates were higher in the assays with NaCl and NaBr. Reaction by-products were identified by gas chromatography-mass spectrometry. Indirect oxidation by electrogenerated reactive halogen species (RHS) was the main mechanism when halide ions were used as electrolytes. Ten by-products were detected using Na2SO4 as electrolyte, while 19 (12 non-halogenated and 7 halogenated) and 20 (10 non-halogenated and 10 halogenated) using NaCl and NaBr respectively. The proposed degradation pathways involve transformation (hydroxylation, deamination, desulfonation, and halogenation) and bond rupture to produce less molecular weight compounds and their further transformation until total degradation. Chlorinated and brominated by-products confirm halogenation reactions. The electrogenerated RHS presented a significant inhibition effect on Vibrio fischeri; nevertheless, acute toxicity was not presented using Na2SO4 as electrolyte and a pharmaceutical concentration of 5 µg/L. In this view, the role of the supporting electrolyte in electrochemical oxidation process is crucial since it strongly influence degradation rate, by-products, and acute toxicity.
Assuntos
Carbamazepina/química , Eletrólitos/química , Propranolol/química , Sulfametoxazol/química , Poluentes Químicos da Água/química , Boro , Carbamazepina/toxicidade , Diamante , Eletrodos , Cromatografia Gasosa-Espectrometria de Massas , Oxirredução , Propranolol/toxicidade , Sulfametoxazol/toxicidade , Titânio , Testes de Toxicidade Aguda , Poluentes Químicos da Água/toxicidadeRESUMO
The removal of polycyclic aromatic hydrocarbons by membrane bioreactor (MBR) under aerobic conditions had been studied using naphthalene (NAP) and phenanthrene (PHE) as model compounds. Three MBRs with submerged ultra-filtration hollow fiber membranes were operated applying different operational conditions during 6.5 months. Complete NAP and PHE removal was obtained applying loads of 7 gNAP kgTSS(-1) day(-1) and 0.5 gPHE kgTSS(-1) day(-1), while the organic loading rate was adjusted to 0.26 kgCOD kgTSS(-1) day(-1), with the biomass concentration being 6000 mgTSS L(-1), the hydraulic retention time (HRT) 8 h and the solids retention time (SRT) 30 days. Load increases, as well as HRT and SRT reductions, affected the NAP and PHE removals. Biodegradation was found to be the major NAP and PHE removal mechanism. There was no NAP accumulation in the biomass. Low PHE quantities remain sorbed in the biomass and the contribution of the sorption in the removal of this compound was estimated to be less than 0.01 %. The volatilization does not contribute to the PHE removal in MBRs, but the contribution of NAP volatilization can reach up to 0.6 % when HRT of 8 h is applied.
Assuntos
Reatores Biológicos , Naftalenos/metabolismo , Fenantrenos/metabolismo , Biodegradação Ambiental , Biomassa , Membranas Artificiais , Naftalenos/isolamento & purificação , Fenantrenos/isolamento & purificação , Eliminação de Resíduos LíquidosRESUMO
Si bien se ve un auge en el tratamiento de aguas residuales municipales e industriales en toda Latinoamérica no es lo mismo con el manejo y disposición adecuada para los lodos residuales generados. En este trabajo se presentan los principales aspectos para la planeación de un sistema de composteo con base en los diseños de dos plantas de tratamiento de aguas residuales. Se proporcionan los costos de inversión inicial y algunos aspectos para la comercialización del producto
Assuntos
Engenharia Sanitária , Purificação da Água , Estações de Tratamento , Congresso , ComércioRESUMO
Se presenta un panorama del desarrollo del derecho ambiental mexicano, la nueva política y legislación referente a la calidad de las aguas nacionales. Se aclaran las atribuciones para la elaboración de la normatividad, las verificaciones normativas y las responsabilidades por el incumplimiento de las disposiciones ambientales