RESUMO
Granular activated carbon (GAC) fixed bed adsorption technology was applied to remove carbamates carbaryl, methomyl and carbofuran from public water supply. In order to minimize the effect of clogging and to evaluate adsorbent saturation for carbamates, the microfiltration (MF) was previously used to adsorb and the backwash procedure of the GAC bed was carried out. The determination and quantification of the carbamates were performed by analytical technique in high performance liquid chromatography with post-column derivatization and fluorescence detector. The MF of the water previously adsorbed in the GAC fixed bed allowed the greater removal of 100% of the carbamates pesticides with an initial concentration of 25â µgâ L-1 during the first 48â h of operation. The saturation of the GAC fixed bed occurred in 240â h, due to the partial removal of the natural organic matter by the MF, consequently the competition for adsorptive sites of the GAC was smaller. The backwashing procedure contributed to the partial recovery of the performance of the hydraulic filtration and allowed to identify the saturation of the adsorption column, since the sealing phenomenon preceded the saturation. Finally, the use of public water supply was considered a relevant and positive aspect, since it allowed the identification of the performance of this technology in the removal of carbamates pesticides considering the presence of substances inherent to the public water supply.
Assuntos
Praguicidas , Poluentes Químicos da Água , Purificação da Água , Adsorção , Qualidade da Água , Abastecimento de ÁguaRESUMO
The application of a fixed bed adsorption column of granular activated carbon (FBAC-GAC), in the removal of carbaryl, methomyl and carbofuran at a concentration of 25â µgâ L-1 for each carbamate, from the public water supply was investigated. For the determination of the presence of pesticides in the water supply, the analytical technique of high-performance liquid chromatography with post-column derivatization was used. Under conditions of constant diffusivity, the FBAC-GAC was saturated after 196â h of operation on a pilot scale. The exhaust rate of the granular activated carbon (GAC) in the FBAC-GAC until the point of saturation was 0.02â kgâ GACâ m-3 of treated water. By comparing a rapid small-scale column test and FBAC-GAC, it was confirmed that the predominant intraparticle diffusivity in the adsorption column was constant diffusivity. Based on the results obtained on a pilot scale, it was possible to estimate the values to be applied in the FBAC-GAC (full scale) to remove the pesticides, which are particle size with an average diameter of 1.5â mm GAC; relationship between the internal diameter of the column and the average diameter of GAC ≥50 in order to avoid preferential flow near the adsorption column wall; surface application rate 240â m3â m-2â d-1 and an empty bed contact time of 3â min. ABBREVIATIONS: BV: bed volume; CD: constant diffusivity; EBCT: empty bed contact time; FBAC-GAC: fixed bed adsorption column of granular activated carbon; GAC: granular activated carbon; MPV: maximum permitted values; NOM: natural organic matter; PD: proportional diffusivity; pHPCZ: pH of the zero charge point; SAR: surface application rate; RSSCT: rapid small-scale column test; WTCS: water treated conventional system.
Assuntos
Praguicidas , Poluentes Químicos da Água , Purificação da Água , Adsorção , Carbono , Carvão Vegetal , Abastecimento de ÁguaRESUMO
One of the main problems faced by the oil industry is related to the amount of produced water generated during the oil extraction process. For proper disposal of this effluent, treatment processes should be applied to meet the requirements established by environmental agencies. Thus, the present study aimed to evaluate the efficiency of the combination of electroflotation process and down-flow granular filtration in the treatment of wastewater contaminated with oil. To this end, they were studied in a pilot system, to optimize the electroflotation process and combination of processes. The performance of the pilot system was determined by removal of oil and grease content (OG) in the treated effluent. According to the results, the electroflotation process had the best performance with an effluent input rate of 62â m3â m-2â d-1, current density of 80â Aâ m-2 and NaCl concentration of 7900â mgâ L-1. Under these conditions, the mean removal of OG from synthesized solution after 720 minutes of treatment was 86.64% (59.51â mgâ L-1) for the electroflotation process and 61.52% (12.91â mgâ L-1) after down-flow granular filtration. By combining the processes studied, we obtained an initial OG removal (470.55â mgâ L-1) of over 98% (6.42â mgâ L-1) in 720 minutes of treatment, with an energy consumption of the electrochemical reactor of 1.47â kWhâ m-3. ABBREVIATIONS: ANOVA: analysis of variance; CCRD: Central Composite Rotational Delineation; DOC: dissolved organic carbon; DSA: dimensionally stable anodes; LAPOA: Laboratory of Water Potabilization; OG: oil and grease; OPER: operating parameters of the electrochemical reactor; TDS: total dissolved solids; UFSC: Federal University of Santa Catarina.