Linda V. González-Gutiérrez

Development of an activated carbon-packed microbial bioelectrochemical system for azo dye degradation

A microbial bioelectrochemical reactor (BER) was employed for the degradation of azo dyes without the use of an external electron donor, using activated carbon (GAC) as a redox mediator. Contribution of pH values, open circuit potential (OCP), dye concentration and applied current were individually studied. A batch system and an upflow fixed bed bioreactor were built for analyzing the effect of the applied current on biodegradation of the azo dye Reactive Red 272. The presence of GAC (20% w/v) regulated both pH and OCP values in solution and led to a removal efficiency of 98%. Cyclic voltammetry results indicate a dependence of the electron transfer mechanism with the concentration of the azo compound. With these results, a continuous flow reactor operating with J=0.045 mA cm(-2), led to removal rates of 95% (± 3.5%) in a half-residence time of 1 hour.

Reactive red azo dye degradation in a UASB bioreactor: Mechanism and kinetics

Textile industry uses azo dyes in its processes, which are complex organic molecules that are not easy to be degraded. Reactive dyes are especially difficult to remove from wastewater because of the characteristics of the molecule: one or more azo bonds, naphthalene‐disulfonate, triazine or chloro‐triazine, and phenyl‐amine groups. The degradation of the azo dye reactive red 272 was studied under anaerobic conditions in a hybrid Upflow Anaerobic Sludge Bed reactor (UASB) with an activated carbon bed. An adapted consortium of microorganisms was used in the kinetic study (batch) and to inoculate the UASB reactor. The experimental design identified the main factors determining the dye reduction efficiency are the initial concentration of dye and dextrose (as electron donor) and the residence time in the reactor. Dye reduction rate was decreased as the concentration increases in the wastewater; as a result, a kinetic model with a change from first to second order is proposed. The kinetic study showed that the process is first abiotic (adsorption) and then biotic (biodegradation).

Upflow fixed bed bioelectrochemical reactor for wastewater treatment applications

A cylindrical Upflow Fixed Bed Reactor (UFB-BER) with granular activated carbon, steel mesh electrodes and anaerobic microorganisms, was constructed for analyzing how hydrodynamic parameters affect the reactions involved during wastewater treatment processes for azo dye degradation. Dye removal percentage was not compromised by decreasing HRTm (99-90% upon changing HRTm from 4 to 1h in single pass mode). Using the residence time distribution method for hydrodynamic characterization, it was found that a higher dispersion in the reactor occurs for HRTm=1h, than for HRTm=4h. A kinetic analysis suggests that this dispersion effect could be associated to a higher specific reaction rate dependent on the azo dye concentration.