Simultaneous removal of atrazine and nitrate using a biological granulated activated carbon (BGAC) reactor

The objective of this research was to characterize the performance of granulated activated carbon (GAC) as a carrier for Pseudomonas ADP in a non-sterile continuous fluidized bed reactor for atrazine degradation under anoxic conditions. The GAC was compared with two non-adsorbing carriers: non-adsorbing carbon particles ('Baker product') having the same surface area available for biofilm growth as the GAC, and sintered glass beads. The initial atrazine degradation efficiency was higher than 90% in the reactors with the non-adsorbing carriers, but deteriorated to 20% with time due to contamination by foreign denitrifying bacteria. In contrast, no deterioration was observed in the biological granulated activated carbon (BGAC reactor. A maximal atrazine volumetric and specific degradation rate of 0.820 ± 0.052 g atrazine dm^-3 day^-1 and 1.7 ± 0.4 g atrazine g^-1 protein day^-1 respectively were observed in the BGAC reactor. Concurrent atrazine biodegradation and desorption from the carrier was shown and an effluent concentration of 0.002 mg dm^-3 (below the EPA standard) was achieved in the BGAC reactor. The advantages of the BGAC reactor over the non-adsorbing carrier reactors can probably be explained by the adsorption-desorption mechanism providing favorable microenvironmental conditions for atrazine-degrading bacteria.