Electrochemical oxidation of imazapyr with BDD electrode in titanium substrate.

In this work we have studied the treatment of imazapyr by electrochemical oxidation with boron-doped diamond anode. Electrochemical degradation experiments were performed in a one-compartment cell containing 0.45 L of commercial formulations of herbicide in the pH range 3.0-10.0 by applying a density current between 10 and 150 mA cm(-2) and in the temperature range 25-45 °C. The maximum current efficiencies were obtained at lower current densities since the electrochemical system is under mass transfer control. The mineralization rate increased in acid medium and at higher temperatures. The treatment was able to completely degrade imazapyr in the range 4.6-100.0 mg L(-1), although the current charge required rises along with the increasing initial concentration of the herbicide. Toxicity analysis with the bioluminescent bacterium Vibrio fischeri showed that at higher pollutant concentrations the toxicity was reduced after the electrochemical treatment. To clarify the reaction pathway for imazapyr mineralization by OH radicals, LC-MS/MS analyses we performed together with a theoretical study. Ions analysis showed the formation of high levels of ammonium in the cathode. The main final products of the electrochemical oxidation of imazapyr with diamond thin film electrodes are formic, acetic and butyric acids.

Analysis of a microbial community associated with polychlorinated biphenyl degradation in anaerobic batch reactors.

The degradation of polychlorinated biphenyls (PCBs) was investigated under fermentative-methanogenic conditions for up to 60 days in the presence of anaerobic biomass from a full-scale UASB reactor. The low methane yields in the PCBs-spiked batch reactors suggested that the biomass had an inhibitory effect on the methanogenic community. Reactors containing PCBs and co-substrates (ethanol/sodium formate) exhibited substantial PCB reductions from 0.7 to 0.2 mg mL(-1). For the Bacteria domain, the PCBs-spiked reactors were grouped with the PCB-free reactors with a similarity of 55 %, which suggested the selection of a specific population in the presence of PCBs. Three genera of bacteria were found exclusively in the PCB-spiked reactors and were identified using pyrosequencing analysis, Sedimentibacter, Tissierela and Fusibacter. Interestingly, the Sedimentibacter, which was previously correlated with the reductive dechlorination of PCBs, had the highest relative abundance in the RCS-PCB (7.4 %) and RCS-PCB-PF (12.4 %) reactors. Thus, the anaerobic sludge from the UASB reactor contains bacteria from the Firmicutes phylum that are capable of degrading PCBs.