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

BACKGROUND: 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 η ATZ near to 100% were reached, although accumulation of metabolic byproducts was detected. The fluidized‐bed biofilm reactor allowed atrazine removal rates R V , ATZ higher than that permitted by suspended cell cultures with similar removal efficiencies. In this system, the highest volumetric removal rate was obtained ( R V , ATZ = 12.2 mg L −1 h −1 ), with herbicide removal efficiencies η ATZ 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 R V , 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