RESUMO
Complex wastewater is generated during biodiesel production. We propose a new solution for the treatment of wastewater from enzymatic pretreatment of biodiesel production (WEPBP) by using a hybrid system based on the photo-Fered-Fenton process with O3 assistance (PEF-Fered-O3). We applied response surface methodology (RSM) to determine the suitable conditions for the PEF-Fered-O3 process: a current intensity of 3 A, an initial solution pH controlled at 6.4, an initial H2O2 concentration of 12,000 mg L-1, and an O3 concentration of 50 mg L-1. We performed three new experiments under similar conditions with slight changes to the conditions, namely a longer reaction time (120 min) and single or periodic H2O2 addition (i.e., small H2O2 additions at different reaction times). Periodic H2O2 addition provided the best removal results probably by reducing the occurrence of undesired side reactions that cause hydroxyl radical (â¢OH) scavenging. With the application of the hybrid system, the chemical oxygen demand (COD) and total organic carbon (TOC) decreased by 91% and 75%, respectively. We also evaluated the presence of metals such as iron, copper, and calcium; electric conductivity; and voltage at 5, 10, 15, 30, 45, 60, 90, and 120 min. We submitted raw and treated WEPBP sludge samples to X-ray diffraction to study the degree of crystallinity. There was a rearrangement of the compounds present in treated WEPBP, possibly caused by oxidation of a large fraction of organic matter. Finally, we evaluated the genotoxicity and cytotoxicity of WEPBP by using Allium cepa meristematic root cells. Treated WEPBP was less toxic to these cells, denoted by improvements in gene regulation and cell morphology. Given the current scenario for the biodiesel industry, applying the proposed hybrid PEF-Fered-O3 system at suitable conditions provides an efficient alternative to treat a complex matrix, namely WEPBP, to reduce its potential to cause abnormalities in the cells of living organisms. Thus, the negative impacts of the discharge of WEPBP in the environment might be reduced.
Assuntos
Águas Residuárias , Poluentes Químicos da Água , Peróxido de Hidrogênio/química , Biocombustíveis , Descontaminação , Poluentes Químicos da Água/química , Oxirredução , Eliminação de Resíduos Líquidos/métodosRESUMO
In this work, the application of an iron electrode-based electrocoagulation (EC) process on the treatment of a real textile wastewater (RTW) was investigated. In order to perform an efficient integration of the EC process with a biological oxidation one, an enhancement in the biodegradability and low toxicity of final compounds was sought. Optimal values of EC reactor operation parameters (pH, current density and electrolysis time) were achieved by applying a full factorial 3(3) experimental design. Biodegradability and toxicity assays were performed on treated RTW samples obtained at the optimal values of: pH of the solution (7.0), current density (142.9â Aâ m(-2)) and different electrolysis times. As response variables for the biodegradability and toxicity assessment, the Zahn-Wellens test (Dt), the ratio values of dissolved organic carbon (DOC) relative to low-molecular-weight carboxylates anions (LMCA) and lethal concentration 50 (LC50) were used. According to the Dt, the DOC/LMCA ratio and LC50, an electrolysis time of 15â min along with the optimal values of pH and current density were suggested as suitable for a next stage of treatment based on a biological oxidation process.
Assuntos
Eletrólise/métodos , Lactuca/efeitos dos fármacos , Águas Residuárias/química , Poluentes Químicos da Água/isolamento & purificação , Poluentes Químicos da Água/toxicidade , Purificação da Água/métodos , Biodegradação Ambiental , Resíduos Industriais/prevenção & controle , Indústria Têxtil , Poluentes Químicos da Água/efeitos da radiaçãoRESUMO
An electro-coagulation laboratory scale system using aluminium plates electrodes was studied for the removal of organic and inorganic pollutants as a by-product from leather finishing industrial process. A fractional factorial 2(3) experimental design was applied in order to obtain optimal values of the system state variables. The electro-coagulation (EC) process efficiency was based on the chemical oxygen demand (COD), turbidity, total suspended solid, total fixed solid, total volatile solid, and chemical element concentration values. Analysis of variance (ANOVA) for final pH, total fixed solid (TFS), turbidity and Ca concentration have confirmed the predicted models by the experimental design within a 95% confidence level. The reactor working conditions close to real effluent pH (7.6) and electrolysis time in the range 30-45 min were enough to achieve the cost effective reduction factors of organic and inorganic pollutants' concentrations. An appreciable improvement in COD removal efficiency was obtained for electro-coagulation treatment. Finally, the technical-economical analysis results have clearly shown that the electro-coagulation method is very promising for industrial application.
Assuntos
Alumínio/química , Técnicas Eletroquímicas/métodos , Curtume , Eliminação de Resíduos Líquidos/métodos , Purificação da Água/métodos , Análise de Variância , Cálcio/análise , Custos e Análise de Custo , Eletricidade , Técnicas Eletroquímicas/economia , Eletrodos , Eletrólise , Concentração de Íons de Hidrogênio , Ferro/química , Cinética , Nefelometria e Turbidimetria , Fatores de Tempo , Compostos Orgânicos Voláteis/análise , Eliminação de Resíduos Líquidos/economia , Poluentes Químicos da Água/isolamento & purificação , Purificação da Água/economiaRESUMO
In this study the pollutant removal from a textile dyeing wastewater has been investigated by using the electro-coagulation technique with iron electrodes. In order to obtain optimal values of the system state variables, a 3(3) full factorial experimental design was applied. The electro-coagulation (EC) process response was evaluated on the basis of COD removal and decolourization values. The electrolysis time and density current were statistically significant for the COD removal and decolourization. Based on the lettuce seeds (Lactuca sativa) and brine shrimp (Artemia salina), the lowest toxicity level was achieved in 5 min of electrolysis time. Due to the remaining high toxicity level above 30 min of electrolysis time, the EC process is not adequate to be used in a single effluent treatment, suggesting that this electrochemical process of up to 5 min could be used as part of a complete effluent treatment system.