Solar photo-Fenton optimization at neutral pH for microcontaminant removal at pilot plant scale

Abstract

The increasing occurrence of micropollutants in natural water bodies has medium to long-term effects on both aquatic life and human health. The aim of this study is to optimize the degradation of two pharmaceutical pollutants of emerging concern: amoxicillin and acetaminophen in aqueous solution at laboratory and pilot scale, by solar photo-Fenton process carried out at neutral pH using ethylenediamine-N,N'-disuccinic acid (EDDS) as a complexing agent to maintain iron in solution. The initial concentration of each compound was set at 1 mg/L dissolved in a simulated effluent from a municipal wastewater treatment plant (MWTP). A factorial experimental design and its surface response analysis were used to optimize the operating parameters to achieve the highest initial degradation rate of each target. The evolution of the degradation process was measured by ultra-performance liquid chromatography (UPLC/UV), obtaining elimination rates above 90% for both contaminants. Statistical study showed the optimum concentrations of Fe(III) at 3 mg/L at an Fe-EDDS ratio of 1:2 and 2.75 mg/L H₂O₂ for the almost complete removal of the target compounds by solar photo-Fenton process. Validation of the experimental design was successfully carried out with actual MWTP effluent spiked with 100 μg/L of amoxicillin and acetaminophen, each at pilot plant scale.

Keywords: Antibiotics; Contaminants of emerging concern; Fe-EDDS; Optimization; Solar photo-Fenton; Tertiary treatment.

Fig. 1

Experimental device employed in the performance of the experimental design, Suntest, XLS + Heraeus, Germany

Fig. 2

Pareto chart showing the influence of each variable (Fe(III) in the EDDS complex and H₂O₂) versus a standardized effect

Fig. 3

Main effect graph of each selected variable (Fe (III) complexed with EDDS and H₂O₂) on the initial degradation rate for each target contaminant (response factor)

Fig. 4

Response surfaces showing the variation of influence of each variable (Fe (III) complexed with EDDS and H₂O₂) on the initial degradation rate of A AMX and B ACT

Fig. 5

Contour graph showing the influence potential of each studied range for each variable (Fe(III) complexed with EDDS and H₂O₂) on the initial degradation rate of both target contaminants

Fig. 6

Normal probability plot of the residuals from the statistical model obtained in the central composite design