Influence of ethanol as a co-substrate on bioremediation of water contaminated with glyphosate-based comercial formulation

ABSTRACT

This study aimed to evaluate the efficiency and degradation kinetics of commercial glyphosate formulation in previously contaminated water samples via aerobic process using ethanol as a co-substrate. An aerobic reactor with 1L volumetric capacity operated in sequential batch system with 24-hour cycles and suspended biomass was used. Four different nutritional conditions were tested: one with no ethanol addition; and three others with ethanol: glyphosate ratios of 7.8:1, 27.5:1 and 18.3:1. Operating with no ethanol addition, the efficiency of glyphosate removal was 18% and increased to 78% when ethanol was added to the system in a 7.8:1 ratio. However, when glyphosate concentration was further increased in the next phases, it did not result in higher removal efficiency, probably due to the preference of organisms for ethanol use as a carbon source over glyphosate. The results of the kinetic tests adjusted to first-order degradation models considering residual glyphosate. Phase 3 with 27.5:1 ethanol/glyphosate ratio showed the highest apparent kinetic constant value, k = 0.01746. The results of this study suggest that using ethanol as a co-substrate can be an alternative for decontamination of glyphosate contaminated waters.

Keywords:
glyphosate; co-substrate; aerobic treatment