Kinetics of atrazine biodegradation by suspended and immobilized mixed microbial cells cultivated in continuous systems

Abstract

AbstractBACKGROUND: Using a suspended or immobilized microbial community obtained through chemostat selection from agricultural soils formerly treated with triazinic herbicides, the atrazine biodegradation kinetics in continuous aerobic reaction systems was studied.RESULTS: When microbial cells were continuously cultivated on atrazine as the sole nitrogen and carbon source, atrazine removal efficiencies ηATZ near to 100% were reached, although accumulation of metabolic byproducts was detected. The fluidized‐bed biofilm reactor allowed atrazine removal rates RV, ATZ higher than that permitted by suspended cell cultures with similar removal efficiencies. In this system, the highest volumetric removal rate was obtained (RV, ATZ = 12.2 mg L−1 h−1), with herbicide removal efficiencies ηATZ near 100% and reduced accumulation of byproducts.CONCLUSIONS: With the operational conditions probed in continuous suspended‐cell culture, increasing the C:N ratio in the inflowing medium resulted in higher cell growth yields but not in better atrazine removal rates. Kinetic results showed that for similar working conditions higher RV, ATZ values and reduced amounts of degradation byproducts of recalcitrant organic compounds could be expected with multi‐stage biofilm reactors. Copyright © 2009 Society of Chemical Industry