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%.