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.

► The biodegradation rate of azo dyes is increased when an electric field is applied.
► Activated carbon in the bioelectrochemical reactor regulates both pH and open circuit potential.
► Synergistic effect of electrical and biological parameters reduce the residence time of the reactor.
► Growth of microorganisms increases in response to the applied current.