Hydrogen peroxide production in a pilot-scale microbial electrolysis cell

Scale-up and techno-economic analysis of microbial electrolysis cells for hydrogen production from wastewater

Microbial electrolysis cells (MECs) have demonstrated high-rate H₂ production while concurrently treating wastewater, but the transition in scale from laboratory research to systems that can be practically applied has encountered challenges. It has been more than a decade since the first pilot-scale MEC was reported, and in recent years, many attempts have been made to overcome the barriers and move the technology to the market. This study provided a detailed analysis of MEC scale-up efforts and summarized the key factors that should be considered to further develop the technology. We compared the major scale-up configurations and systematically evaluated their performance from both technical and economic perspectives. We characterized how system scale-up impacts the key performance metrics such as volumetric current density and H₂ production rate, and we proposed methods to evaluate and optimize system design and fabrication. In addition, preliminary techno-economic analysis indicates that MECs can be profitable in many different market scenarios with or without subsidies. We also provide perspectives on future development needed to transition MEC technology to the marketplace.

Promoted Sb removal with hydrogen production in microbial electrolysis cell by ZIF-67-derived modified sulfate-reducing bacteria bio-cathode

Bio-cathode Microbial electrolysis cell (MEC) has been widely discovered for heavy metals removal and hydrogen production. However, low electron transfer efficiency and heavy metal toxicity limit MEC treatment efficiency. In this study, ZIF-67 was introduced to modify Sulfate-reducing bacteria (SRB) bio-cathode to enhance the bioreduction of sulfate and Antimony (Sb) with hydrogen production in the MEC. ZIF-67 modified bio-cathode was developed from a bio-anode microbial fuel cell (MFC) by operating with an applied voltage of 0.8 V to reverse the polarity. Cyclic voltammetry, linear sweep voltammetry and electrochemical impedance were done to confirm the performance of the ZIF-67 modified SRB bio-cathode. The synergy reduction of sulfate and Sb was accomplished by sulfide metal precipitation reaction from SRB itself. Maximum sulfate reduction rate approached 93.37 % and Sb removal efficiency could reach 92 %, which relies on the amount of sulfide concentration generated by sulfate reduction reaction, with 0.923 ± 0.04 m³ H₂/m³ of hydrogen before adding Sb and 0.857 m³ H₂/m³ of hydrogen after adding Sb. The hydrogen was mainly produced in this system and the result of gas chromatography (GC) indicated that 73.27 % of hydrogen was produced. Meanwhile the precipitates were analyzed by X-ray diffraction and X-ray photoelectron spectroscopy to confirm Sb₂S₃ was generated from Sb (V).

Degradation of β-lactam antibiotic ampicillin using sustainable microbial peroxide producing cell system

The enormous use of synthetic antibiotic and personal care products has impacted the natural microbiome and ecosystem. Overtime, treatment technologies developed suffered due to incomplete removal hence, a pilot dual-chambered microbial peroxide-producing cell that degrades ampicillin catalyzed by homogenous Fenton-reaction was designed. The system reported maximum current at 16.714 ± 0.048 µAcm^-2, power output of 1.956 ± 0.015 mW m^-2; 88 ± 2.90 mM of H₂O₂ generation with Na₂SO₄ that degraded 95.9 ± 3.00 to 97.8 ± 3.20% of 10 mg L^-1ampicillin within 72 hrs with electro-active Shewanella putrefaciens. An E. coli bioactivity assay with ampicillin exhibited no sensitivity zone due to the loss of activity. Analytical spectroscopic studies reveal β-Lactam ring deformation; Liquid Chromatography-Mass Spectroscopy clearly shows the presence of degradation metabolites. A sustainable wastewater treatment with 72 ± 4.5% reduction in anodic chemical oxygen demand was achieved. Present results designate the technology, as promising for effective antibiotics removal for wastewater treatment concomitant with electricity generation.

A Review of Stand-Alone and Hybrid Microbial Electrochemical Systems for Antibiotics Removal from Wastewater

The growing concern about residual antibiotics in the water environment pushes for innovative and cost-effective technologies for antibiotics removal from wastewater. In this context, various microbial electrochemical systems have been investigated as an alternative to conventional wastewater technologies that are usually ineffective for the adequate removal of antibiotics. This review article details the development of stand-alone and hybrid or integrated microbial electrochemical systems for antibiotics removal from wastewater. First, technical features, antibiotics removal efficiencies, process optimization, and technological bottlenecks of these systems are discussed. Second, a comparative summary based on the existing reports was established to provide insights into the selection between stand-alone and hybrid systems. Finally, research gaps, the relevance of recent progress in complementary areas, and future research needs have been discussed.

Enhancing biohydrogen production from sugar industry wastewater using Ni, Ni-Co and Ni-Co-P electrodeposits as cathodes in microbial electrolysis cells

Microbial electrolysis cell (MEC) can be utilized for the simultaneous treatment of actual industry wastewater and biohydrogen production. However, efficient and cost-effective cathode, working at ambient conditions and neutral pH, are required to make the MEC as a sustainable technology. In this study, MEC with electrodeposited cathodes (co-deposits of Ni, Ni-Co and Ni-Co-P) were utilized to evaluate the treatment efficiency and hydrogen recovery of sugar industry wastewater. MECs operation was carried out at 30 ± 2 °C temperature in batch mode at an applied voltage of 0.6 V in neutral pH with sugar industry effluent (COD 4850 ± 50 mg L^-1, BOD 1950 ± 20 mg L^-1) and activated sludge as a source of microorganism. The Ni-Co-P electrodeposit on both cases achieved the maximum H₂ production rate of 0.24 ± 0.005 m³(H2) m^-3 d^-1 and 0.21 ± 0.005 m³(H2) m^-3 d^-1 with ~50 % treatment efficiency for a 500 ml effluent in 7 days' batch cycles. It was also found that fabricated cathodes can treat real wastewater efficiently with considerable energy recovery than previously reported literature. This study showed the potentiality of the real-time industrial effluents treatment and biohydrogen production near to ambient atmospheric conditions that emphasizes the waste to energy bio-electrochemical system.

Cost-efficient microbial electrosynthesis of hydrogen peroxide on a facile-prepared floating electrode by entrapping oxygen

Microbial electrosynthesis of hydrogen peroxide is receiving growing interest for a green substitute for anthraquinone process.However, poor oxygen transmission of electrode remains an obstacle to enhance H₂O₂ production rate without aeration. Here, a superhydrophobic natural air diffusion floating electrode (NADFE), which naturally and efficiently entraps O₂ in the air, was proposed for the first time to improve microbial electrosynthesis of H₂O₂. Furthermore, a one-step calcined electrode preparation method was developed to reduce energy consumption further. In the microbial electrolysis cell with the NADFE, a high H₂O₂ production rate of 39 mg/L/h and current efficiency of 86% were achieved without aeration. The production rate of H₂O₂ was 2.2 times that of a gas diffusion electrode. Importantly, the energy consumption was 34.3 times lower than an electrochemical system. Therefore, the high H₂O₂ production rate and current efficiency, and low energy consumption of the process provide a superior alternative for environmental remediation.

Effects of nickle, nickle-cobalt and nickle-cobalt-phosphorus nanocatalysts for enhancing biohydrogen production in microbial electrolysis cells using paper industry wastewater

Paper industries are water-intensive industries that produce large amount of wastewater containing dyes, toxicity and high nutrient content. These industries require sustainable technology for their waste disposal and MEC could be one of them. However, effective MEC operation at neutral pH and ambient temperature requires economical and efficient cathodes that are capable to treat indusial wastewater along with recovery of energy/biohydrogen. Co-deposits of Nickel, Nickel-Cobalt and Nickel-Cobalt-Phosphorous on the surface of SS and Cu base metals distinctly were used as cathodes in MEC for the concurrent treatment of real paper industry wastewater and biohydrogen production. MECs were utilized in batch mode at neutral pH, applied voltage of 0.6 V and 30 ± 2 °C temperature with paper industry wastewater and activated sludge as microbial sources. The fabricated Nickel-Cobalt-Phosphorous gives the higher hydrogen production rate of 0.16 ± 0.002 m³(H₂) m^-3d^-1 and 0.14 ± 0.002 m³(H₂) m ^-3d ^-1 respectively, with ~33-42 % treatment efficiency for a 500 ml wastewater in 7-day batch cycle in both the cases; while it is lowest in the case of the control cathodes (SS1 (0.07 ± 0.002 m³(H₂) m^-3d^-1) & Cu1 (0.06 ± 0.004 m³(H₂) m^-3d^-1)). It was also found that fabricated cathodes have the capability to treat industrial wastewater at ambient conditions efficiently with higher energy recovery. Prepared cathodes show enhanced hydrogen production and treatment efficiency as well as are competitive to some reported literature.

Removal of aspirin from aqueous solution using electroactive bacteria induced by alternating current

This study aims to improve bacterial laccase enzyme activity (LEA) and dehydrogenase activity (DHA) affecting acetylsalicylic acid (ASA) biodegradation using an alternating current (AC). A microbial consortium was inoculated in an electroactive bioreactor supplied with an AC by a function generator under operating conditions of amplitude (AMPL) = 2-10 peak-to-peak voltage (Vpp), optical fiber splice tray (OFST) = 0.1 V, and sine wave frequency = 10 Hz. The obtained results revealed that at an applied voltage of 8 Vpp and an OFST of 0.1 for 12 h, the maximum bacterial LEA and DHA were 30.6 U/mL and 75.5 micro grTF/cm2.gr biomass; respectively. Cell viability and permeability were equal to 95.7% and 0.3%; respectively, at the voltage of 8 Vpp. Moreover, liquid chromatography-mass spectrometry (LC-MS) and gas chromatography-mass spectrometry (GC-MS) analyses showed that by-products had lower intensity at 8 Vpp compared with that of 2 Vpp voltage. Finally, the results demonstrated an optimum applied voltage of the AC, which could stimulate and promote bacterial LEA and DHA. Therefore, an electroactive bioreactor supplied with an AC can be a novel system for stimulation of enzyme activities in the process of ASA biodegradation.

Scaling-up of microbial electrosynthesis with multiple electrodes for in situ production of hydrogen peroxide

Microbial electrosynthesis system (MES) has recently been shown to be a promising alternative way for realizing in situ and energy-saving synthesis of hydrogen peroxide (H₂O₂). Although promising, the scaling-up feasibility of such a process is rarely reported. In this study, a 20-L up-scaled two-chamber MES reactor was developed and investigated for in situ and efficient H₂O₂ electrosynthesis. Maximum H₂O₂ production rate of 10.82 mg L⁻¹ h⁻¹ and cumulative H₂O₂ concentration of 454.44 mg L⁻¹ within 42 h were obtained with an input voltage of 0.6 V, cathodic aeration velocity of 0.045 mL min⁻¹ mL⁻¹, 50 mM Na₂SO₄, and initial pH 3. The electrical energy consumption regarding direct input voltage was only 0.239 kWh kg⁻¹ H₂O₂, which was further much lower compared with laboratory-scale systems. The obtained results suggested that the future industrialization of MES technology for in situ synthesis of H₂O₂ and further application in environmental remediation have broad prospects.

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Up-scaled microbial electrosynthesis with multiple electrodes to synthesize H₂O₂

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The H₂O₂ yield was higher than that of laboratory-scale systems using graphite cathode

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Energy consumption was lower than that of laboratory-scale (bio)electrochemical systems

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Systematic evaluation of the influence of operating parameters on H₂O₂ production

Sewage enhanced bioelectrochemical degradation of petroleum hydrocarbons in soil environment through bioelectro-stimulation

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Acetate and sewage were evaluated for enhanced hydrocarbons degradation in soil bioelectrochemical systems.

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Sewage has superior function in improving in situ bioelectrochemical degradation.

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Both acetate and sewage improved power density, substrate and sulfate removal.

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Soil contaminated with produced water was remediated by more than 70 %.

The impact of readily biodegradable substrates (sewage and acetate) in bioelectroremediation of hydrocarbons (PW) was evaluated in a bench-scale soil-based hybrid bioelectrochemical system. Addition of bioelectro-stimulants evidenced efficient degradation than control operation. Acetate and sewage were exhibited power density of 1126 mW/m² and 1145 mW/m², respectively, which is almost 15 % higher than control (without stimulant, 974 mW/m²). Increased electrochemical activity was correlated well with total petroleum hydrocarbons (TPH) degradation through addition of acetate (TPH_R, 525 mg/L, 67.4 %) and sewage (TPH_R, 560 mg/L,71.8 %) compared to the control operation (TPH_R, 503 mg/L, 64.5 %). Similarly, chemical oxygen demand (COD) reduction was also enhanced from 69.0 % (control) to 72.1 % and 74.6 % with acetate and sewage, respectively. Sewage and acetate also showed a positive role in sulfates removal, which enhanced from 56.0 % (control) to 62.9 % (acetate) and 72.6 % (sewage). This study signifies the superior function of sewage as biostimulant compared to acetate for the bioelectroremediation of hydrocarbons in contaminated soils.

A proof of concept study for wastewater reuse using bioelectrochemical processes combined with complementary post-treatment technologies

This article describes a proof-of-concept study designed for the reuse of wastewater using microbial electrochemical cells (MECs) combined with complementary post-treatment technologies. This study mainly focused on how the integrated approach works effectively for wastewater reuse. In this study, microalgae and ultraviolet C (UVC) light were used for advanced wastewater treatment to achieve site-specific treatment goals such as agricultural reuse and aquifer recharge. The bio-electrosynthesis of H₂O₂ in MECs was carried out based on a novel concept to integrate with UVC, especially for roust removal of trace organic compounds (TOrCs) resistant to biodegradation, and the algal treatment was configured for nutrient removal from MEC effluent. UVC irradiation has also proven to be an effective disinfectant for bacteria, protozoa, and viruses in water. The average energy consumption rate for MECs fed acetate-based synthetic wastewater was 0.28±0.01 kWh per kg of H₂O₂, which was significantly more efficient than are conventional electrochemical processes. MECs achieved 89±2% removal of carbonaceous organic matter (measured as chemical oxygen demand) in the wastewater (anolyte) and concurrent production of H₂O₂ up to 222±11 mg L^-1 in the tapwater (catholyte). The nutrients (N and P) remaining after MECs were successfully removed by subsequent phycoremediation with microalgae when aerated (5% CO₂, v/v) in the light. This complied with discharge permits that limit N to 20 mg L^-1 and P to 0.5 mg L^-1 in the effluent. H₂O₂ produced on site was used to mediate photolytic oxidation with UVC light for degradation of recalcitrant TOrCs in the algal-treated wastewater. Carbamazepine was used as a model compound and was almost completely removed with an added 10 mg L^-1 of H₂O₂ at a UVC dose of 1000 mJ cm^-2. These results should not be generalized, but critically discussed, because of the limitations of using synthetic wastewater.