Enhancement of the potential biodegradability and the mineralization of a pesticides mixture after being treated by a coupled process of TiO2-based solar photocatalysis with constructed wetlands.

Abstract

Solar heterogeneous photocatalysis is an advanced oxidation technology, which allows a successful treatment of many recalcitrant and emergent pollutants, such as: pesticides, industrial dyes and pharmaceutical compounds. Nonetheless, despite its effectiveness, the costs of applying this process are high when it is necessary to achieve a complete mineralization or to obtain an environment-friendly effluent. Photocatalytic–biological coupled systems have become in a feasible alternative able to treat efficiently these pollutants. In this work, a coupled system consistent of two compound parabolic collectors (CPC) solar photoreactors and a subsurface flow constructed wetland (SFCW) at pilot-scale was tested for degrading a mixture of commercial pesticides used in sugar cane crops. For measuring the process performance, regarding to the pollutant removal, the increase of the BOD5/COD ratio and the total organic carbon (TOC) removal were estimated for each separated system and the coupled system. Three different levels of solar UV accumulated energy and feed flow-rates to the SFCW were considered for the experimental design. The pilot-scale coupled system increased the BOD5/COD ratio from 0.15 to 0.90, and the TOC removal (total mineralization) was around 80%.

La fotocatálisis solar homogénea es un proceso de oxidación avanzada que permite tratar de forma exitosa un gran númerode contaminantes recalcitrantes, como: pesticidas, tintas industriales y compuestos farmacéuticos. No obstante, a pesar de suefectividad, los costos de aplicación de este proceso son altos cuando se trata de alcanzar la mineralización completa o deobtener un efluente amigable con el medio ambiente. Los sistemas acoplados fotocatalítico-biológicos se han convertido enuna alternativa factible para tratar de forma eficiente estos contaminantes. En este trabajo, un sistema acoplado de dos reactoressolares de colectores parabólicos compuestos (CPC) y humedales artificiales de flujos sub-superficial (HFSS) a escala piloto seevaluó para degradar un mezcla de pesticidas comerciales usados en el cultivo de la caña de azúcar. Para medir el desempeño delproceso para eliminar el contaminante, se estimaron el aumento de la relación DBO5/DQO y la reducción del carbono orgánicototal (COT) para cada sistema por separado y para el acople. Se consideraron tres diferentes niveles de radiación solar UVacumulada y de flujos de alimentación al HFSS en el diseño experimental. La relación DBO5/DQO aumentó de 0.15 a 0.90 y lareducción de COT (mineralización total) estuvo alrededor del 80%.