Degradación de la mezcla comercial de los herbicidas atrazina y ametrina, utilizando cultivos con células en suspensión e inmovilizadas

The excessive use of herbicides has caused weeds resistance to these compounds; thus, it has been implemented the use of mixtures of herbicides to ensure its effect on weeds. One of the commercial mixtures used in Mexico is that of atrazine and ametryn. Information on processes for ametryn degradation is scarce, and virtually no references to the biodegradation of the commercial mixture of atrazine and ametryn exist. In this study, the biodegradation of this commercial mixture using a microbial community in different types of cultures, and using a chemostat and biobarrier is presented. To assess the degradation capability of the microbial community, planktonic cells were used in a semi-continuous batch system. From this system, the continuous process was started. In repeated batch cultures, complete removal of both herbicides was obtained. In the continuous system, at all tested volumetric loads, the removal efficiencies of ametryn and atrazine were of 100 and 97 % respectively. During continuous operation, biofilm formation on the reactor walls was observed; thus, it was decided to install a biobarrier using volcanic rock fragments (tezontle) as biofilm support. In this system, the removal efficiencies (ŋ) and the volumetric removal rates (Rv) of the herbicide mixture were 100 % and 287 mg/L/d, respectively. At all the loading rates tested, cyanuric acid accumulation was observed; however, when the biobarrier was operated at low volumetric loading rates, considerable metabolic degradation of this intermediate was achieved.