Electrochemistry-stimulated environmental bioremediation:Development of applicable modular electrode and system scale-up

Bioelectrochemical systems(BESs)have been studied extensively during the past decades owing primarily to their versatility and potential in addressing the water-energy-resource nexus.In stark contrast to the significant advancements that have been made in developing innovative processes for pollution control and bioresource/bioenergy recovery,minimal progress has been achieved in demonstrating the feasibility of BESs in scaled-up applications.This lack of scaled-up demonstration could be ascribed to the absence of suitable electrode modules(EMs)engineered for large-scale application.In this study,we report a scalable composite-engineered EM(total volume of 1 m^(3)),fabricated using graphite-coated stainless steel and carbon felt,that allows integrating BESs into mainstream wastewater treatment technologies.The cost-effectiveness and easy scalability of this EM provides a viable and clear path to facilitate the transition between the success of the lab studies and applications of BESs to solve multiple pressing environmental issues at full-scale.

Efficient treatment of azo dye containing wastewater in a hybrid acidogenic bioreactor stimulated by biocatalyzed electrolysis

In this study, a novel scaled-up hybrid acidogenic bioreactor（HAB） was designed and adopted to evaluate the performance of azo dye（acid red G, ARG） containing wastewater treatment. Principally, HAB is an acidogenic bioreactor coupled with a biocatalyzed electrolysis module. The effects of hydraulic retention time（HRT） and ARG loading rate on the performance of HAB were investigated. In addition, the influent was switched from synthetic wastewater to domestic wastewater to examine the key parameters for the application of HAB. The results showed that the introduction of the biocatalyzed electrolysis module could enhance anoxic decolorization and COD（chemical oxygen demand） removal. The combined process of HAB-CASS presented superior performance compared to a control system without biocatalyzed electrolysis（AB-CASS）. When the influent was switched to domestic wastewater, with an environment having more balanced nutrients and diverse organic matters, the ARG, COD and nitrogen removal efficiencies of HAB-CASS were further improved, reaching 73.3% ± 2.5%, 86.2% ± 3.8% and 93.5% ± 1.6% at HRT of 6 hr, respectively, which were much higher than those of AB-CASS（61.1% ± 4.7%,75.4% ± 5.0% and 82.1% ± 2.1%, respectively）. Moreover, larger TCV/TV（total cathode volume/total volume） for HAB led to higher current and ARG removal. The ARG removal efficiency and current at TCV/TV of 0.15 were 39.2% ± 3.7% and 28.30 ± 1.48 mA,respectively. They were significantly increased to 62.1% ± 2.0% and 34.55 ± 0.83 mA at TCV/TV of 0.25. These results show that HAB system could be used to effectively treat real wastewater.

A tartrate-EDTA-Fe complex mediates electron transfer and enhances ammonia recovery in a bioelectrochemical-stripping system

Traditional bioelectrochemical systems(BESs)coupled with stripping units for ammonia recovery suffer from an insufficient supply of electron acceptors due to the low solubility of oxygen.In this study,we proposed a novel strategy to efficiently transport the oxidizing equivalent provided at the stripping unit to the cathode by introducing a highly soluble electron mediator(EM)into the catholyte.To validate this strategy,we developed a new kind of iron complex system(tartrate-EDTA-Fe)as the EM.EDTA-Fe contributed to the redox property with a midpoint potential of
0.075 V(vs.standard hydrogen electrode,SHE)at pH 10,whereas tartrate acted as a stabilizer to avoid iron precipitation under alkaline conditions.At a ratio of the catholyte recirculation rate to the anolyte flow rate(RC-A)of 12,the NH4 t-N recovery rate in the system with 50mM tartrate-EDTA-Fe complex reached 6.9±0.2 g Nm^(-2) d^(-1),approximately 3.8 times higher than that in the non-EM control.With the help of the complex,our system showed an NH4 t-N recovery performance comparable to that previously reported but with an extremely low RC-A(0.5 vs.288).The strategy proposed here may guide the future of ammonia recovery BES scale-up because the introduction of an EM allows aeration to be performed only at the stripping unit instead of at every cathode,which is beneficial for the system design due to its simplicity and reliability.