Performance of the fixed-bed of granular activated carbon for the removal of pesticides from water supply

ABSTRACT

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 25 μg 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 196 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 0.02 kg GAC 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 1.5 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 240 m³ m⁻² d⁻¹ and an empty bed contact time of 3 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; pH_PCZ: pH of the zero charge point; SAR: surface application rate; RSSCT: rapid small-scale column test; WTCS: water treated conventional system

KEYWORDS:

• Adsorption
• carbamates
• carbaryl
• methomyl
• carbofuran

Acknowledgements

The authors are grateful to the Laboratório Central de Microscopia Eletrônica of the Federal University of Santa Catarina for performing the scanning electron microscopy tests.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

The authors are grateful to the Financiadora de Estudos e Projetos [CHAMADAS PÚBLICAS MCT/FINEP/AÇÃO TRANSVERSAL SA] and the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior for their financial support of the development of this research.