Optimization of sensing performance in an integrated dual sensors system combining microbial fuel cells and upflow anaerobic sludge bed reactor

Recent Developments and Applications of Microbial Electrochemical Biosensors

This chapter provides a comprehensive overview of microbial electrochemical biosensors, which are a unique class of biosensors that utilize the metabolic activity of microorganisms to convert chemical signals into electrical signals. The principles and mechanisms of these biosensors are discussed, including the different types of microorganisms that can be used. The various applications of microbial electrochemical biosensors in fields such as environmental monitoring, medical diagnostics, and food safety are also explored. The chapter concludes with a discussion of future research directions and potential advancements in the field of microbial electrochemical biosensors.

Microbial Fuel Cell-Based Organic Matter Sensors: Principles, Structures and Applications

Wastewater contains a significant quantity of organic matter, continuously causing environmental pollution. Timely and accurate detection of organic content in water can facilitate improved wastewater treatment and better protect the environment. Microbial fuel cells (MFCs) are increasingly recognized as valuable biological monitoring systems, due to their ability to swiftly detect organic indicators such as biological oxygen demand (BOD) and chemical oxygen demand (COD) in water quality. Different types of MFC sensors are used for BOD and COD detection, each with unique features and benefits. This review focuses on different types of MFC sensors used for BOD and COD detection, discussing their benefits and structural optimization, as well as the influencing factors of MFC-based biomonitoring systems. Additionally, the challenges and prospects associated with the development of reliable MFC sensing systems are discussed.

The versatility of microbial fuel cells as tools for organic matter monitoring

Water monitoring and remediation require robust, low-cost, and reliable test systems that can couple with prompt treatment interventions. Organic matter (BOD, COD), toxicants, heavy metals, and other pollutants in water need to be regularly inspected. Microbial fuel cells (MFCs) have already gained popularity as BOD biomonitoring systems as these don't need an external transducer or power source. Moreover, these systems are cost-effective, compact, biodegradable, reusable, portable, and applicable for on-site measurements. MFCs truly stands out as online BOD measurement devices as they provide wide detection range (0-25 g/L), low response time (2-4 min) and longer stability in continuous operations (2-5 years) in a cost-effective approach. This review examines the benefits, kinds, performance metrics, and signal optimization of the current state-of-the-art of the BOD measurement, with detailed focus on MFC-based BOD biomonitoring systems. This review covers the important technological breakthroughs in practical applications with associated bottlenecks to develop reliable sensing systems.

Application of the EGSB-CMBR Process to High-Concentration Organic Wastewater Treatment

To decrease the cost of wastewater treatment at the plant, the Wuzhou Shenguan Protein Enteric Coating Production Plant designed and built an expanded granular sludge bed (EGSB)-ceramic membrane bioreactor reactor (CMBR) process for treating high-concentration organic wastewater with a capacity of 25 m3/d. The EGSB is divided into anaerobic and microaerobic sections. The purpose of the anaerobic section is to substantially degrade COD, and the main functions of the microaerobic section are to coordinate the relationship between hydrolytic acid-producing bacteria, methanogenic bacteria (MBP), and sulfate-reducing bacteria (SRB) and to mitigate the inhibitory effects between them to simultaneously remove COD and sulfate. Anaerobic ammonia-oxidizing bacteria were added to the CMBR reactor to remove both COD and ammonia nitrogen. The results of the operation showed that more than 99% of the COD was removed by the EGSB-CMBR process, while the removal rates of NH4+-N and SS were greater than 70% and 90%, respectively. In addition, the effluent met the requirements of the secondary standard of the Comprehensive Wastewater Discharge Standard (8978-1996). Economic and technical analyses showed that the modified EGSB-CMBR reactor has a high treatment efficiency, which greatly saves on the cost of the “commissioned treatment” of high-concentration organic waste liquid in the plant. Specifically, it can save more than 800,000 CNY for the plant annually.

Integrating anaerobic digestion with bioelectrochemical system for performance enhancement: A mini review

Strategies for enhancing performance of anaerobic digestion (AD) process has been widely studied. The bioelectrochemical system (BES), including microbial fuel cell, microbial electrolysis cell (MEC), microbial desalination cell, and microbial electrosynthesis, had been proposed to integrate with AD for performance enhancement. This mini-review summarizes the current researches that integrated AD with BES to enhance the performance of the former. The working principles of BES were introduced. The integrated configurations of AD-BES as well as the associated applications were summarized. The statistics analysis for AD-MEC performances reported in literature were then performed to confirm the effects of reactor size and applied voltage on the methane productivity and enhancement. The challenges and prospects of the integrated AD-BES were delineated, and the potential scenarios of applying integrated AD-BES in field were discussed.

Long-term in situ bioelectrochemical monitoring of biohythane process: Metabolic interactions and microbial evolution

Microbial stability and evolution are a critical aspect for biosensors, especially in detecting dynamic and emerging anaerobic biohythane production. In this study, two upflow air-cathode chamber microbial fuel cells (UMFCs) were developed for in situ monitoring of the biohydrogen and biomethane reactors under a COD range of 1000-6000 mg/L and 150-1000 mg/L, respectively. Illumina MiSeq sequencing evidenced the dramatic shift of dominant microbial communities in UMFCs from hydrolytic and acidification bacteria (Clostridiaceae_1, Ruminococcaceae, Peptostreptococcaceae) to acetate-oxidizing bacteria (Synergistaceae, Dysgonomonadaceae, Spirochaetaceae). In addition, exoelectroactive bacteria evaluated from Enterobacteriaceae and Burkholderiaceae to Desulfovibrionaceae and Propionibacteriaceae. Especially, Hydrogenotrophic methanogens (Methanobacteriaceae) were abundant at 93.41% in UMFC (for monitoring hydrogen reactor), which was speculated to be a major metabolic pathway for methane production. Principal component analysis revealed a similarity in microbial structure between UMFCs and methane bioreactors. Microbial network analysis suggested a more stable community structure of UMFCs with 205 days' operation.

Recent developments in monitoring technology for anaerobic digesters: A focus on bio-electrochemical systems

With the increasing popularity of waste to energy conversion, demand for large-scale operation of anaerobic digestors has emerged in the market. However, the process instabilities in anaerobic digestors limit the expansion of facilities to high loading rates. The irregularities in the process can be addressed directly by altering the feedstock characteristics provided an on-hand, robust, and sensitive monitoring device is available. In this context, the bioelectrochemical system has emerged as an excellent tool for monitoring and optimizing the anaerobic process within the reactor. This article reviews the gradual evolution in techniques and approaches for monitoring of anaerobic digestion (AD) process. An analysis of the recently popular biosensing techniques has been done with a focus on the bioelectrochemical monitoring system and its operation mode. A brief attempt to highlight the current challenges in the field of bioelectrochemical process monitoring for AD has also been made, which can be supportive of future research.

A novel UASB-MFC dual sensors system for wastewater treatment: On-line sensor recovery and electrode cleaning in the long-term operation

In this research, the UASB-MFC dual sensors system was established and treatment the brewery wastewater. The COD removal rate attain about 90% and the NH₄⁺-N concentration less than 15 mg/L, MFCs has a voltage range of 0.34-0.42 V. Meanwhile, as the biosensor for coupling system, MFCs can be used to make simultaneous monitor COD and TVFA. The potential distribution can in-situ accelerate the reattachment of micro-organisms, which shorten the recovery time to 55% of the original. The long-term performance of MFCs were tested by electrochemical methods and found that the degradation of biosensors was mainly caused by the precipitation of Ca²⁺ and Mg²⁺ on the cathode surface and affected by concentration. More importantly, cleaning the electrode by an self-enhanced method without external assistance ECS (Electrodes Connection Switching) can improve the MFCs performance to 83.2 %-84.6%. Dual sensors system in UASB gives a novel possibility for UASB-MFC sensor self-sustaining in a long-term.

Using an anaerobic digestion tank as the anodic chamber of an algae-assisted microbial fuel cell to improve energy production from food waste

Anaerobic digestion is sensitive to a wide variety of inhibitory substances that are the primary cause of anaerobic digester failure. Herein, an anaerobic digestion (AD) tank, which also functioned as the anodic chamber of an algae-assisted microbial fuel cell (AMFC), was established to treat food waste (FW) under an inhibition-relieved condition. About 2.9 L of CH₄ was yielded by the AD-AMFC system, which was more than double the CH₄ produced by the AD system, and 34% higher than that from the AD-MFC system. The result suggests that the bioelectrochemical system and algae successfully improved the AD performance and energy production. The AD-AMFC system had the highest volatile fatty acid (VFA) concentration in the initial 20 days, but it maintained the lowest VFA concentration in the following days. Those results indicate that the AMFC shortened the acclimatisation phase of the AD process and then alleviated the adverse impact of VFAs by consuming VFAs as a substrate for electricity generation. Alkalinity generated by algal growth and cathode reactions buffered the H⁺ that migrated from the anolyte, which facilitated the pH recovery of the AD process. Ammonia inhibition of the AD was also relieved by the AMFC through reduction of the ammonia concentration to less than 500 mg/L in the anolyte. Additionally, the COD removal rate was improved to 89%, since the AMFC facilitated the decomposition of large molecules. The present study developed a practical structure for an AD tank and also explained the reason as to why the AMFC improved the AD performance.

Rapid detection of biodegradable organic matter in polluted water with microbial fuel cell sensor: Method of partial coulombic yield

The quantification of biodegradable organic matter (BOM) in polluted water plays an essential role for biodegradation-based processing of wastewater and management of water environment. Compared with the traditional detection of five-day biochemical oxygen demand (BOD₅), microbial fuel cell (MFC) sensors have shown an advantage for rapid and more accurate BOM assessment in several hours using coulombic yield of MFC as the signal. In this study, we propose a new calculation method that relies on the partial coulombic yield (P-CY) to further shorten the duration of the measurement. The P-CY is the cumulative coulomb at the point at which the voltage acquisition reaches a maximum voltage drop rate. The detection results with the standard GGA solution (a mixture of glucose and glutamic acid) show an enhanced linear relationship ranging from 37.5 mg L^-1 to 375 mg L^-1 in comparison to conventional methods. Notably, the response time for P-CY is remarkably shortened (0.99 ± 0.18-18.08 ± 0.58 h). The cutoff point for P-CY has more stable electrochemical characteristics, which enhances the accuracy of BOM detection. Furthermore, the validity of our determination of the cutoff point for P-CY is demonstrated by a mathematical model based on the Michaelis-Menten equation. Thus, the P-CY method is viable for the rapid detection of BOM in polluted water.

Recent development of biofuel cell based self-powered biosensors

BFC-based SPBs have been used as power sources for other devices and as sensors for detecting toxicity and BOM.

Fluctuation of electrode potential based on molecular regulation induced diversity of electrogenesis behavior in multiple equilibrium microbial fuel cell

In this study, the electrogenesis behaviors and mechanisms in multiple equilibrium microbial fuel cells (MEMFCs) which volatile fatty acids as multiple electron donors are investigated. The electrochemical property and energy recovery can be enhanced in propionic acid dominant systems (HPr-D-MEMFCs) which compares to butyric acid dominant systems (HBu-D-MEMFCs), increase power density from 0.04 to 0.43 W/m² and energy recovery efficiency from 2.07 to 5.44%, respectively. With isotope experiment analysis, the fluctuation of electrode potentials induce diverse electrogenesis pathways that high utilization efficiencies and bioconversion efficiency of hybrid acids observed in HPr-D-MEMFCs which different with HAc-D-MEMFCs and HBu-D-MEMFCs. In addition, the electrochemical and microbial community variation of MEMFCs reveal that the direct interspecies electron transfer stimulated with higher electric double layer capacitance, and activities of exoelectrogens enhanced with high relative abundance in HPr-D-MEMFCs. The findings present an intensive study in electrogenesis, providing a promising way to promote energy recovery and further extend its application value.

Bioelectrochemically-assisted vermibiofilter process enhancing stabilization of sewage sludge with synchronous electricity generation

Bioelectrochemically-assisted vermifilter (VBF_BE) with sewage sludge as the anode fuel was constructed to accelerate composting of sewage sludge, which could increase the quality of the compost and harvest electric energy in comparison with vermicomposting and electrochemical only. Results revealed that the sludge stabilization with a higher soluble chemical oxygen demand (SCOD) and lower NH₄⁺-H during 40 days of composting. At the composting, pH, C/N, electrical conductivity (EC) and germination index (GI) results demonstrated that the maturity degree of VBF_BE4 was higher than that of other VBF_BE. The VBF_BE4 yielded a voltage of 1.024 V and maximum power density of 105.28 mW/m² on 3th day. The bacteria in VBF_BE4 were richer and higher in terms of diversity than those in other VBF_BE, that was demonstrated that combination vermicomposting and electrochemistry could improve the sludge stabilization degree, accelerate sludge composting process and enhance composting maturity.

The investigation on Fe3O4 magnetic flocculation for high efficiency treatment of oily micro-polluted water

For the low-concentration oily micro-polluted water formed by the leakage of refined oil products, an unexpensive and high-efficiency magnetic enhanced flocculation method was introduced in this study. First, the performance of magnetic flocculation(MF) to remove oily contaminants was discussed. The results indicated that it achieved more than 95% removal in only 1min with 50mg/L-Polyaluminum chloride(PAC), 50mg/L-Fe₃O₄ and10mg/L- Polyacrylamide (PAM). The novel indexs R_δand S_i were proposed to evaluate the oil removal with UV-Abs in-situ method. According to the adsorption kinetics of oil contaminants, the adsorption kinetics changed from pseudo-first-order to pseudo-second-order kinetics after the addition of Fe₃O₄ on the basis of conventional coagulation (CF). It was transformed into intraparticle diffusion kinetics when the PAM continued to be added. Combined with the Fe-O-Al bond in the FTIR spectrum of flocs, the main mechanism of MF is enhanced charge neutralization and hydrogen bond adsorption. In addition, it was shown that satisfactory oil removal after recover, which indicated the great potential of a sustainable way by reusing low-cost magnetic seeds.