Bioelectrochemical Treatment System Research Articles

Municipal landfill leachate remediation coupling acidogenesis and bioelectrogenesis for biohydrogen and volatile fatty acids production

This study aimed at sustainable treatment of municipal landfill leachate (MLL) along with resource recovery by integrating acidogenesis and bioelectrogenesis. Initially, during acidogenic fermentation, more than 60 % of MLL COD was converted to biohydrogen (0.23 L/g CODload) and volatile fatty acids (VFAs; 56.15 g COD/L). Acetic (25.09 g COD/L), propionic (1.27 g COD/L), and butyric acid (29.77 g COD/L) made up the majority of VFAs. To increase MLL's further treatment, the left-over COD in the acidogenic effluent was introduced into bio-electrochemical treatment system. Three differently configured bio-electrochemical treatment systems (BET1, BET2, and BET3) were evaluated varying their anode composition. BET1 was operated with a capacitive designed PANi/CNT composite electrode, while BET2 was operated with PANi-SSM and BET3 with a graphite electrode. The modified composite electrode in BET1 played a significant role in leachate treatment (COD removal, 71.21 %) displaying a power density of 35 mW/m2. Apart from higher removal of ammoniacal nitrogen, sulfates and phosphates, the composite electrodes in the BET1 resulted in improved bioelectrogenic activity and capacity of electrons migration between electrode and biocatalyst. Additionally, the modified anode showed higher redox peak currents, lower charge transfer resistance, and ohmic losses.

Removal of Coliphage MS2 Using a Microbial Fuel Cell Stack

Bioelectrochemical technologies offer alternative ways of treating wastewater and using this process to generate electricity. However, research in this area is just beginning to consider environmental transmission of viruses present in wastewater. The viral fecal indicator coliphage MS2 (the most frequently used pathogen model) was used in this study, since it is a well-known indigenous wastewater virus. The scaled-up bioelectrochemical system had a working volume of 167 L and coliphage MS2 concentration decreased from 8000 to 285 PFU/mL. The kinetics were quantified up to 15 h, after which excessive yeast growth in the system prevented further bacteriophage determination. The logarithmic reduction value (LRV) calculated within the first three hours was 3.8. From 4 hours to 14, LRV values were from 4.1 to 4.8, and in hour 15 the LRV increased to 5.3, yielding a more than 90% reduction. Overall, results obtained indicate that the scaled-up bioelectrochemical treatment system was efficient in reducing coliphage MS2 densities and could be used as a model to explore its further applicability for the reduction of viruses or pathogens in treated effluents.

Shell outlines transformation plan for Singapore refining, chemicals businesses.

The present study evaluates the sequential integration of two advanced biological treatment methods viz., sequencing batch reactor (SBR) and bioelectrochemical treatment systems (BET) for the treatment of real-field petrochemical wastewater (PCW). Initially two SBR reactors were operated in aerobic (SBRAe) and anoxic (SBRAx) microenvironments with an organic loading rate (OLR) of 9.68 kg COD/m3-day. Relatively, SBRAx showed higher substrate degradation (3.34 kg COD/m3-day) compared to SBRAe (2.9 kg COD/m3-day). To further improve treatment efficiency, the effluents from SBR process were fed to BET reactors. BETAx depicted higher SDR (1.92 kg COD/m3-day) with simultaneous power generation (17.12 mW/m2) followed by BETAe (1.80 kg COD/m3-day; 14.25 mW/m2). Integrating both the processes documented significant improvement in COD removal efficiency due to the flexibility of combining multiple microenvironments sequentially. Results were supported with GC–MS and FTIR, which confirmed the increment in biodegradability of wastewater.

Spatial variation of electrode position in bioelectrochemical treatment system: Design consideration for azo dye remediation

In the present study, three bio-electrochemical treatment systems (BET) were designed with variations in cathode electrode placement [air exposed (BET1), partially submerged (BET2) and fully submerged (BET3)] to evaluate azo-dye based wastewater treatment at three dye loading concentrations (50, 250 and 500 mg L−1). Highest dye decolorization (94.5 ± 0.4%) and COD removal (62.2 ± 0.8%) efficiencies were observed in BET3 (fully submerged electrodes) followed by BET1 and BET2, while bioelectrogenic activity was highest in BET1 followed by BET2 and BET3. It was observed that competition among electron acceptors (electrode, dye molecules and intermediates) critically regulated the fate of bio-electrogenesis to be higher in BET1 and dye removal higher in BET3. Maximum half-cell potentials in BET3 depict higher electron acceptance by electrodes utilized for dye degradation. Study infers that spatial positioning of electrodes in BET3 is more suitable towards dye remediation, which can be considered for scaling-up/designing a treatment plant for large-scale industrial applications.

Multi-electrode bioelectrochemical system for the treatment of high total dissolved solids bearing chemical based wastewater

Multi-electrode bioelectrochemical treatment system (ME-BET; membrane less) consisting of six electrode assemblies (E1–E6) was designed and fabricated for the treatment of complex chemical based wastewater with high salt concentration. The performance was compared with single electrode assembly BET reactor (SE-BET). Enhanced TDS and COD removal was observed in ME-BET (32%; 56%) compared to SE-BET (15%; 23%) as a result of in situ bio-potential from multi-electrodes through the oxidation of organic substrate in the wastewater. Inorganic pollutants viz., nitrates (28%; 8%), sulphates (25%; 9%) and phosphates (20%; 7%) removal was higher in ME-BET in comparison with SE-BET and this was also supported with bioelectrogenic activity (584; 160mW/m3). The study infers that designing of compact reactors with multiple electrodes in a single system enhances the anodic reactions and enable effective treatment of complex wastewaters with simultaneous power production.

Integrated electrochemical treatment systems for facilitating the bioremediation of oil spill contaminated soil

Bioremediation plays an important role in oil spill management and bio-electrochemical treatment systems are supposed to represent a new technology for both effective remediation and energy recovery. Diesel removal rate increased by four times in microbial fuel cells (MFCs) since the electrode served as an electron acceptor, and high power density (29.05 W m−3) at current density 72.38 A m−3 was achieved using diesel (v/v 1%) as the sole substrate. As revealed by Scanning electron microscope images, carbon fibres in the anode electrode were covered with biofilm and the bacterial colloids which build the link between carbon fibres and enhance electron transmission. Trace metabolites produced during the anaerobic biodegradation were identified by gas chromatography–mass spectrometry. These metabolites may act as emulsifying agents that benefit oil dispersion and play a vital role in bioremediation of oil spills in field applications.

Bioelectrochemical anaerobic sewage treatment technology for Arctic communities.

This study describes a novel wastewater treatment technology suitable for small remote northern communities. The technology is based on an enhanced biodegradation of organic carbon through a combination of anaerobic methanogenic and microbial electrochemical (bioelectrochemical) degradation processes leading to biomethane production. The microbial electrochemical degradation is achieved in a membraneless flow-through bioanode-biocathode setup operating at an applied voltage below the water electrolysis threshold. Laboratory wastewater treatment tests conducted through a broad range of mesophilic and psychrophilic temperatures (5-23°C) using synthetic wastewater showed a biochemical oxygen demand (BOD5) removal efficiency of 90-97% and an effluent BOD5 concentration as low as 7mgL-1. An electricity consumption of 0.6kWhkg-1 of chemical oxygen demand (COD) removed was observed. Low energy consumption coupled with enhanced methane production led to a net positive energy balance in the bioelectrochemical treatment system.

Cathodic material effect on electron acceptance towards bioelectricity generation and wastewater treatment

Influence of cathode material on electron accepting conditions during the treatment of recalcitrant pharmaceutical wastewater (PWW) was comparatively evaluated at different organic loads (3, 6, 9 and 15 g/l) in three bioreactors. Two bio-electrochemical treatment systems employed with different electrode materials viz., BET-SS (graphite as anode and stainless steel (SS) as cathode) and BET-G (graphite as both anode and cathode) were evaluated for PWW degradation and bioelectricity generation in comparison to conventional anaerobic treatment (AnT). BET-G exhibited high bioelectrogenic activity than BET-SS, elucidating the impact of varied cathode material. High cathode potential necessary for effective reduction at cathode were observed with graphite-cathode than SS-cathode which are crucial for treatment and power generation. Ohmic losses ascribed to electrode material interference were relatively high in BET-SS in comparison to BET-G. Graphite-cathode exhibited high electron acceptance conditions leading to higher pollutant removal along with organic fraction degradation, bio-electrogenesis and inorganic salts removal, when compared to SS-cathode. Placement of electrode assembly while operating BET with different electrode materials is proved to be significant for treatment and bioelectricity production. Efficient electron accepting conditions and high cathode potential in BET-G proved graphite as promising cathode material over SS for the treatment of PWW.

Functional behavior of bio-electrochemical treatment system with increasing azo dye concentrations: Synergistic interactions of biocatalyst and electrode assembly

Treatment of dye bearing wastewater through biological machinery is particularly challenging due to its recalcitrant and inhibitory nature. In this study, functional behavior and treatment efficiency of bio-electrochemical treatment (BET) system was evaluated with increasing azo dye concentrations (100, 200, 300 and 500mg dye/l). Maximum dye removal was observed at 300mg dye/l (75%) followed by 200mg dye/l (65%), 100mg dye/l (62%) and 500mg dye/l (58%). Concurrent increment in dye load resulted in enhanced azo reductase and dehydrogenase activities respectively (300mg dye/l: 39.6U; 4.96μg/ml). Derivatives of cyclic voltammograms also supported the involvement of various membrane bound redox shuttlers, viz., cytochrome-c, cytochrome-bc1 and flavoproteins during the electron transfer. Bacterial respiration during BET operation utilized various electron acceptors such as electrodes and dye intermediates with simultaneous bioelectricity generation. This study illustrates the synergistic interaction of biocatalyst with electrode assembly for efficient treatment of azo dye wastewater.

Integrating sequencing batch reactor with bio-electrochemical treatment for augmenting remediation efficiency of complex petrochemical wastewater

The present study evaluates the sequential integration of two advanced biological treatment methods viz., sequencing batch reactor (SBR) and bioelectrochemical treatment systems (BET) for the treatment of real-field petrochemical wastewater (PCW). Initially two SBR reactors were operated in aerobic (SBRAe) and anoxic (SBRAx) microenvironments with an organic loading rate (OLR) of 9.68kg COD/m3-day. Relatively, SBRAx showed higher substrate degradation (3.34kg COD/m3-day) compared to SBRAe (2.9kg COD/m3-day). To further improve treatment efficiency, the effluents from SBR process were fed to BET reactors. BETAx depicted higher SDR (1.92kg COD/m3-day) with simultaneous power generation (17.12mW/m2) followed by BETAe (1.80kg COD/m3-day; 14.25mW/m2). Integrating both the processes documented significant improvement in COD removal efficiency due to the flexibility of combining multiple microenvironments sequentially. Results were supported with GC–MS and FTIR, which confirmed the increment in biodegradability of wastewater.

Bioelectrochemical treatment of paper and pulp wastewater in comparison with anaerobic process: Integrating chemical coagulation with simultaneous power production

The efficiency of a bioelectrochemical treatment system (BET) to treat complex paper and pulp wastewater at two different pH conditions (6 and 7) in comparison with conventional anaerobic treatment process (AnT) was evaluated. Among the operating conditions, BET showed good treatment efficiency at pH 7 in terms of COD (BET/AnT: 55%/51%), nitrates (33.5%/19.1%), phosphates (33%/19%) and sulfates (58%/41%) in removal. The effluent obtained from BET system was subjected to coagulation for further treatment which showed good COD removal (BET/AnT, 95%/69%) and color (100%/68%). Bioelectrochemical analysis revealed higher catalytic currents in BET than AnT specific to oxidation and reduction. Besides, derivative of cyclic voltammetric scans (DCV) also supported the involvement of various membrane bound electron transferring complexes like FAD(H) bound enzymes, ubiquinone, NADH+/H+ bound enzymes, etc. Experimental results demonstrated that BET system can be a viable platform to treat complex wastewaters with simultaneous energy recovery in integrated approach.

Anoxic bio-electrochemical system for treatment of complex chemical wastewater with simultaneous bioelectricity generation

Bioelectrochemical treatment system (BET) with anoxic anodic microenvironment was studied with chemical wastewater (CW) in comparison with anoxic treatment (AxT, sequencing batch reactor (SBR)) with same parent anaerobic consortia. BET system documented relatively higher treatment efficiency at higher organic load (5.0 kg COD/m(3)) accounting for COD removal efficiency of (90%) along with nitrate (48%), phosphate (51%), sulphates (68%), colour (63%) and turbidity (90%) removal, compared to AxT operation (COD, 47%; nitrate, 36%; phosphate, 32%; sulphate, 35%; colour, 45% and turbidity, 54%). The self-induced bio-potential developed due to the electrode assembly in BET resulted in effective treatment with simultaneous bioelectricity generation (631 mA/m(2)). AxT operation showed persistent reduction behaviour, while simultaneous redox behaviour was observed with BET indicating balanced electron transfer. BET operation illustrated higher wastewater toxicity reduction compared to the AxT system which documents the variation in bio-electrocatalytic behaviour of same consortia under different microenvironment.

Bio-electrochemical treatment of distillery wastewater in microbial fuel cell facilitating decolorization and desalination along with power generation

Microbial fuel cell (MFC; open-air cathode) was evaluated as bio-electrochemical treatment system for distillery wastewater during bioelectricity generation. MFC was operated at three substrate loading conditions in fed-batch mode under acidophilic (pH 6) condition using anaerobic consortia as anodic-biocatalyst. Current visualized marked improvement with increase in substrate load without any process inhibition (2.12–2.48 mA). Apart from electricity generation, MFC documented efficient treatment of distillery wastewater and illustrated its function as an integrated wastewater treatment system by simultaneously removing multiple pollutants. Fuel cell operation yielded enhanced substrate degradation (COD, 72.84%) compared to the fermentation process (∼29.5% improvement). Interestingly due to treatment in MFC, considerable reduction in color (31.67%) of distillery wastewater was also observed as against color intensification normally observed due to re-polymerization in corresponding anaerobic process. Good reduction in total dissolved solids (TDS, 23.96%) was also noticed due to fuel cell operation, which is generally not amenable in biological treatment. The simultaneous removal of multiple pollutants observed in distillery wastewater might be attributed to the biologically catalyzed electrochemical reactions occurring in the anodic chamber of MFC mediated by anaerobic substrate metabolism.

Integrated function of microbial fuel cell (MFC) as bio-electrochemical treatment system associated with bioelectricity generation under higher substrate load

Function of microbial fuel cell (MFC) as bio-electrochemical treatment system in concurrence with power generation was evaluated with composite chemical wastewater at high loading conditions (18.6gCOD/l; 56.8gTDS/l). Two dual chambered MFCs [non-catalyzed graphite electrodes; mediatorless anode] were studied separately with aerated and potassium ferricyanide catholytes under similar anodic operating conditions [mixed consortia; pH 6]. Marked improvement in power output was observed at applied higher substrate loading rate for extended period of time without any process inhibition. Catholyte nature showed significant influence on power generation [ferricyanide—651mV; 18.22mA; 6230mW/kg CODR (500Ω); 2321.69mA/m2 (100Ω); 11.80mW/m3 and aerated—578mV; 10.23mA; 2450mW/kg CODR (400Ω); 1220.68mA/m2 (100Ω); 5.64mW/m3] but not on wastewater treatment efficiency. Along with enhanced substrate degradation, relatively good removal of color (31%) and TDS (51%) was also observed during MFC operation, which might be attributed to the diverse bio-electrochemical processes triggered due to substrate metabolism and subsequent in situ bio-potential (voltage) generation. Apart from power generation, various unit operations pertaining to wastewater treatment viz., biological (anaerobic) process, electrochemical decomposition and electrochemical oxidation were found to occur symbiotically in the anode chamber. Among them anaerobic metabolism is considered to be a crucial and important rate limiting step. In view of inherent advantages, function of MFC as integrated bio-electrochemical treatment system in the direction of various wastewater treatment operations can be exploited.