Upflow Bioelectrochemical Reactor Research Articles

Pave the way for successful treatment of Nylon wastewater by performance enhancement via unit stacking scale up of dual cathodes up-flow microbial fuel cell and C/N adjustment with urea

Integrating filtration membrane cathode and packed granular carbon cathode in an up-flow bio-electrochemical reactor can maintain both higher level treatment capacity and electricity generation in microbial fuel cell (MFC). Further, scale-ups via unit stacking (U-S) or size-enlarged reactor/electrode (SE-RE) were tested treating a Nylon wastewater with inadequate N and high C/N ratio, at suitable hydraulic residence time (HRT). U-S maintained both pollutants removal efficiency and power generation at higher levels than SE-RE, achieving 92.44% NH4+-N, 99.99% NO3--N and 99.66% total inorganic nitrogen removal, and maximum power density 3201 mW/m3 (average 2960 mW/m3). Adjusting influent C/N with urea as additional nitrogen, enhanced COD removal and reduced cathode membrane fouling significantly. The average COD removal reaching 99.28% and 4.23 kg m−3d−1, and average effluent COD concentration and UV254 was 30.37 mg/L and 0.06 cm−1, respectively. The average removals of NH4+-N, NO3--N and total inorganic nitrogen were up to 98.85%, 99.99% and 99.56%, respectively. The EEO (electrical energy at 90% removal) was between 0.48 and 1.40 kWh/m3. U-S scale-up with urea dosage was feasible in practical application of MFC in treating Nylon wastewater.

Impact of Voltage Application on Degradation of Biorefractory Pharmaceuticals in an Anaerobic-Aerobic Coupled Upflow Bioelectrochemical Reactor.

Diclofenac, ibuprofen, and carbamazepine are frequently detected in the environment, where they pose a threat to organisms and ecosystems. We developed anaerobic-aerobic coupled upflow bioelectrochemical reactors (AO-UBERs) with different voltages, hydraulic retention times (HRTs), and types of electrode conversion, and evaluated the ability of the AO-UBERs to remove the three pharmaceuticals. This study showed that when a voltage of 0.6 V was applied, the removal rate of ibuprofen was slightly higher in the system with aerobic cathodic and anaerobic anodic chambers (60.2 ± 11.0%) with HRT of 48 h than in the control systems, and the removal efficiency reached stability faster. Diclofenac removal was 100% in the 1.2 V system with aerobic anodic and anaerobic cathodic chambers, which was greater than in the control system (65.5 ± 2.0%). The contribution of the aerobic cathodic-anodic chambers to the removal of ibuprofen and diclofenac was higher than that of the anaerobic cathodic-anodic chambers. Electrical stimulation barely facilitated the attenuation of carbamazepine. Furthermore, biodegradation-related species (Methyloversatilis, SM1A02, Sporomusa, and Terrimicrobium) were enriched in the AO-UBERs, enhancing pharmaceutical removal. The current study sheds fresh light on the interactions of bacterial populations with the removal of pharmaceuticals in a coupled system.

Electrical stimulation on biodegradation of phenolics in a novel anaerobic–aerobic-coupled upflow bioelectrochemical reactor

• An anaerobic–aerobic-coupled upflow bioelectrochemical reactor was constructed. • Intermittent electrical stimulation mode promoted phenolics degradation. • Aerobic cathodic chamber showed high contribution to the phenolics removal. • Specific microbes were enriched in the cathodic and anodic chambers of the system. Phenolics were widespread in the effluents of coal gasification plants and oil refineries processes, while the impact of electrical stimulation on phenolics degradation in the combined biological processes remained unclear. Here, a novel anaerobic–aerobic–coupled upflow bioelectrochemical reactor (AO-UBER) was used to treat phenol-containing synthetic wastewater and simulated phenolic wastewater. The AO-UBER could treat phenolic compounds effectively via electrical stimulation. Phenol and total phenol removal efficiencies in the intermittently electrically stimulated system with a hydraulic retention time of 6 h were about 22.6% and 31.1%, respectively, higher than that in the biological system not exposed to voltage. The contribution of the aerobic cathodic chamber to the removal of phenolic compounds was higher than that of the anaerobic anodic chamber under the intermittent voltage application mode. High-throughput sequencing analysis indicated that electrical stimulation selectively enriched Acinetobacter , Cloacibacterium , Acidovorax, and Zoogloea in the phenol-containing synthetic wastewater treatment process, and Rhodococcus , Achromobacter , Chryseobacterium, and PSB-M-3 in the simulated phenolic wastewater treatment process. These results demonstrate that the AO-UBER under intermittent voltage application mode holds good potential for efficient phenolic wastewater treatment.

Impact of electrical stimulation modes on the degradation of refractory phenolics and the analysis of microbial communities in an anaerobic-aerobic-coupled upflow bioelectrochemical reactor

An electrically stimulated anaerobic–aerobic coupled system was developed to improve the biodegradation of refractory phenolics. Expected 4-nitrophenol, 2, 4-dinitrophenol, and COD removals in the system with aerobic cathodic and anaerobic anodic chambers were approximately 53.7%, 45.4%, 22.3% (intermittent mode) and 37.9%, 19.8%, 17.3% (continuous mode) higher than that in the control system (26.0 ± 6.4%, 30.7 ± 7.1%, 49.8 ± 3.0%). 2, 4-dichlorophenol removal in the system with aerobic anodic and anaerobic cathodic chambers was approximately 28.5% higher than that in the control system (71.4 ± 5.7%). The contribution of the aerobic cathodic/anodic chambers to the removal of phenolic compounds was higher than that of the anaerobic cathodic/anodic chambers. The species related to phenolic biodegradation (Rhodococcus, Achromobacter, PSB-M-3, and Sphingobium) were enriched in the cathodic and anodic chambers of the system. These results showed that intermittent electrical stimulation could be a potential alternative for the efficient degradation of refractory phenolics.

Reinjection oilfield wastewater treatment using bioelectrochemical system and consequent corrosive community evolution on pipe material

The corrosive issues are comprehensively caused in oilfield rejection system, in which sulfide is one of (bio-)chemical factors leading to high corrosive rate and blocking problem. Generally, aerobic treatment is a well-established and cost-effective unit for sulfide removal before oilfield wastewater reinjection. However, the residual dissolved oxygen (DO), which causes chemical, biological and electrochemical corrosion to water injection pipeline equipment, is still high after multi-stage filtration of DO removal. Here, a novel system to achieve quick and efficient DO removal through a three-electrode (cathode-anode-cathode)-upflow bioelectrochemical reactor (RCAC) was constructed before wastewater reinjection. Bioelectrodes were well established by utilizing organic matters of oilfield wastewater and conducted extracellular electron transport to achieve a steady DO removal from ∼5mg/L to 0.01mg/L (HRT 6h), the DO removal efficiency reached approximately 100%, and the downside biocathode made the largest contribution for DO removal. In the treated wastewater, the corrosion rate of stainless steel N80 ultimately declined over 30 days testing. As a result of DO removal and ammonia conversion to nitrate by bioelectrodes, the corrosive microorganisms were substantially changed. Especially, sulfate-reducing bacteria (SRB) on the surface of N80 immersed in treated wastewater were decreased in abundance; while nitrate-reducing bacteria (NRB) enriched more, which can compete with SRB to prevent biological corrosion.

Simultaneous nitrification and denitrification using a novel up-flow bio-electrochemical reactor

Nitrogen removal is a problem in the field of water treatment, especially in the presence of sulfate. Conventional nitrification and denitrification are usually carried out in two separate reactors. In addition, the effect of sulfate on hydrogenotrophic denitrification is not clear. In this study, simultaneous nitrification and denitrification (SND) for nitrogen removal from water was conducted using a single novel up-flow bio-electrochemical reactor (UBER). The influence of dissolved oxygen (DO) on nitrogen removal was investigated. When influent DO was 7.0 – 8.0 mg L-1, a heterotrophic nitrification zone (with DO 3.2 – 5.5 mg L-1) and a hydrogenotrophic denitrification zone (with DO 1.6 – 4.2 mg L-1) were obtained within the reactor, and the removal rates of NH4+-N and TN reached more than 90%. The distribution of DO inside developing biofilms was measured using microelectrodes. When DO in the hydrogenotrophic denitrification zone was 2.9 mg L-1, DO inside the biofilm was just 0.5 mg L-1. The effect of sulfate on hydrogenotrophic denitrification was studied by regulating the S/N ratio of influent water. Simultaneous removal of nitrate and sulfate can be achieved at low S/N, and the removal rates of nitrate and sulfate were ~80%. With increasing S/N ratio, sulfide produced by sulfate reduction inhibited both denitrification and further sulfate reduction.

Influence of conductive material on the bioelectrochemical removal of organic matter and nitrogen from low strength wastewater

The treatment of low strength wastewater that has the level of discharge standard for wastewater treatment plant was studied using an upflow bioelectrochemical reactor with an applied voltage of 0.6 V. The direct interspecies electron transfer (DIET) between electroactive bacteria was activated in the upflow bioelectrochemical reactor, which improved the substrate affinity of bacteria. The effluent qualities in COD and ammonia nitrogen was stable at less than 3.5 mg/L and 7.46 mg/L at 1 h of hydraulic retention time, respectively. The conductive materials, including conductive sheets and conductive particles, further increased the biomass retention and the DIET by altering the abundance of dominant bacterial groups. The effluent qualities in COD and ammonia nitrogen was improved up to 1.98 mg/L and 2.65 mg/L, respectively, by the conductive sheets. The upflow bioelectrochemical reactor with conductive materials is a good tertiary treatment process for improving the quality of the final effluent discharged from wastewater treatment plant.

Azo dye decolorization in an up-flow bioelectrochemical reactor with domestic wastewater as a cost-effective yet highly efficient electron donor source

A major challenge of employing bioelectrochemical system (BES) for reductively degrading recalcitrant contaminants in industrial wastewater is lacking sufficient electron donors. In this work, domestic wastewater (DW) was demonstrated to efficiently drive BES for implementing the decolorization of azo dye, acid orange 7 (AO7). Side benefit was the simultaneous treatment of DW. Decolorization efficiency in BES fed with DW (RDW) was found to be comparable with that either fed with glucose (RGlu) or acetate (RAc). Much lower reductant usage ratio was observed in RDW. As a result, when the ratio of electron donors to azo dye decreased to 4.4 mol COD mol−1 AO7, DE of RDW kept over 90% while DEs of RAc and RGlu were significantly dropped due to the insufficient electrons donation. Besides serving as electron donor, DW was proved to also provide some conductivity and buffer capacity. Accordingly, DE of RDW was less deteriorated when fully removing the external buffer slats. This study comprehensively revealed the feasibility and superiority of DW as a cost-effective electron donor source in BES and brings this technology closer to the practice.

A twin chamber up-flow bio-electrochemical pumparound system for sequential nitrification and denitrification of reject water

In this study, a modified twin chamber up-flow bioelectrochemical reactor (TCUBER) was investigated during sequential bioelectrochemical nitrification and denitrification of reject water experimentally. A twin chamber up-flow bioelectrochemical pump-around system (TCUBEPS) makes it possible to investigate the effects of different pH values (6.5 ± 0.1, 7.5 ± 0.1, 8.5 ± 0.1, and 9.5 ± 0.1) on the system efficiency at different applied current intensities (I = 20–50 mA) and HRT (6–24 h) values. The results show that the pump-around system succeeded to stabilize the pH and the most favorable values of pH for the activation of nitrifying and denitrifying bacteria in both compartments were 7.5 and 8.5, respectively, whereas the removal percentage of NH4-N was 96% at higher applied HRT (24 h) and constant I (50 mA). This study contributed to a better understanding of the function of variables, namely HRT, pH, and I to treat reject water with high concentration of ammonium.

Sequential nitrification and denitrification in a novel palm shell granular activated carbon twin-chamber upflow bio-electrochemical reactor for treating ammonium-rich wastewater

In this study, a twin-chamber upflow bio-electrochemical reactor packed with palm shell granular activated carbon as biocarrier and third electrode was used for sequential nitrification and denitrification of nitrogen-rich wastewater under different operating conditions. The experiments were performed at a constant pH value for the denitrification compartment. The effect of variables, namely, electric current (I) and hydraulic retention time (HRT), on the pH was considered in the nitrification chamber. The response surface methodology was used based on three levels to develop empirical models for the study on the effects of HRT and current values as independent operating variables on NH4+–N removal. The results showed that ammonium was reduced within the function of an extensive operational range of electric intensity (20–50mA) and HRT (6–24h). The optimum condition for ammonium oxidation (90%) was determined with an I of 32mA and HRT of 19.2h.

Control of pH during water denitrification in an upflow bio-electrochemical reactor (UBER) using a pumparound system

In this study a new reactor design is proposed to control the pH during the bio-electrochemical denitrification process. A previously developed UBER was modified by including a pumparound system. With the pumparound system a portion of the treated water is continuously withdrawn from the UBER into a CO 2 sparging bottle to decrease its pH to about 6.1 ± 0.1, before being returned to the cathode zone where denitrification process takes place. Continuous denitrification was studied with a HRT of 24 h applying an electric current in the range of 15–25 mA. The effects of circulation flow rate ( F c) on the pH and on the concentrations of nitrate and nitrite ions in the effluent were investigated. The pumparound system succeeded to stabilize the cathode pH around 7–8 through alteration of circulation flow rate ( F c). Complete denitrification with no trace of nitrite was therefore achieved at circulation flow rate of 0.7 mL/min and electric current 25 mA. A further investigation in absence of bicarbonate sodium resulted in a satisfactory nitrate treatment showing that the carbon dioxide gas dissolved in the CO 2 sparging bottle supplied enough carbon for the autohydrogenotrophic microorganisms.

Nitrate remediation in a novel upflow bio-electrochemical reactor (UBER) using palm shell activated carbon as cathode material

This study investigated the biological denitrification method which is a treatment method able to reduce inorganic nitrate compounds to harmless nitrogen gas. Autohydrogenotrophic denitrifying bacteria were used in this study to prevent any problematic outcomes associated with heterotrophic microorganisms. An upflow bio-electrochemical reactor (UBER) was used to accommodate hydrogenotrophic denitrifying bacteria employing palm shell granular activated carbon (GAC) as the biocarrier and cathode material. Bicarbonate as the external inorganic carbon source was fed to the reactor and hydrogen as the electron donor was generated in situ through electrolysis of water. Central composite design (CCD) and response surface methodology (RSM) were applied to investigate the effects of two operating parameters, namely electric current ( I) and hydraulic retention time (HRT), on performance of the UBER. Electric current range of 0–20 mA and HRT range of 6–36 h were examined and results showed that nitrate can be entirely reduced within application of a wide operational range of electric current (10–16 mA) as well as HRT (13.5–30 h). However, increase of pH at cathode zone up to 10.5 inhibited nitrite reduction, and it was not reduced to the satisfactory level.