Paradigm shift in Nutrient-Energy-Water centered sustainable wastewater treatment system through synergy of bioelectrochemical system and anaerobic digestion

By
Jim Eadie
-

Abstract

With advancements in research and the necessity of improving the performance of bioelectrochemical system (BES), coupling anaerobic digestion (AD) with BES is crucial for energy gain from wastewater and bioremediation. Hybridization of BES-AD concept opens new avenues for pollutant degradation, carbon capture and nutrient-resource recovery from wastewater. The strength of merging BES-AD lies in synergy, and this approach was employed to differentiate fads from strategies with the potential for full-scale implementation and making it an energy-positive system. The integration of BES and AD system increases the overall performance and complexity of combined system and the cost of operation. From a technical standpoint, the primary determinants of BES-AD feasibility for field applications are the scalability and economic viability. High potential market for such integrated system attract industrial partners for more industrial trials and investment before commercialization. However, BES-AD with high energy efficacy and negative economics demands performance boost.

Introduction

The dependence on fossil fuels and the need for green technology have forced researchers to explore alternative techniques to generate sustainable renewable energy. Anaerobic digestion (AD) is a well-adapted novel wastewater treatment technique with the potential for bioenergy recovery, as the generated biogas during the process can be supplied for electricity/heat production (Chae et al., 2008b). AD treats organic waste and can be highly useful for nutrient and biogas recovery, which can easily be integrated with existing renewable energy techniques (Madondo et al., 2023).

Alternatively, bioelectrochemical system (BES) is a novel, progressive technology for converting waste organics into energy and bioresources through various electrochemical redox reactions with the convergence of microbes. BES is an emerging and multidisciplinary field that creates the intersection of biology, chemistry, environmental science, and electrochemistry. By applying an external voltage, BES accelerates the efficient conversion of complex organic matter as well as volatile fatty acids. The BES-AD system might regulate the establishment of microbial community structures and electron transfer pathways, thereby increasing the entire system’s stability. System stability can be expressed in terms of successful stable operation and long-term viability of stable performance. Based on these applications, BES can be useful for harvesting electricity, hydrogen, volatile fatty acids, alcohols, and value-added industrial chemicals from organic waste. Considering the present need for a sustainable wastewater treatment process, AD and BES can form a syntrophic association for the extraction of energy and other valuable biocommodities from waste.

Although the practical efficiencies of these distinct processes may be modest, various strategies can be employed to overcome these obstacles and establish more efficient system by coupling both systems to treat complex wastewater and more resource recovery scenarios. To improve resource recovery and develop a sustainable system, BES can be a promising option to integrate with AD. Depending on the applications, BES variations, including microbial fuel cell (MFC), microbial electrolysis cell (MEC), microbial desalination cell (MDC), and microbial electrosynthesis system (MES), can be coupled with AD for boosting resource recovery. However, the operational parameters of both processes must be carefully controlled to ensure effective integration and support for upscaling applications. According to the Scopus data (2023), there has been tremendous growth in several documents published since 2000, addressing the different aspects of BES-AD integration and individual process optimization (Fig. 1).

Even though sewage treatment plants consume the most energy as a single facility, they face several difficulties in transitioning to energy self-reliance and carbon neutrality. Such BES-AD integration will guide bioelectrochemical-based tri-generation (energy, resources, and clean water) source technology for energy self-reliance and carbon neutrality of sewage treatment facilities to solve this problem. The present review highlights the strategies for performance enhancement, techno-economic feasibility, challenges, and perspectives, as well as the upscaling issues of the BES-AD integrated system.

Individually, AD has high treatment capability and can treat wide variety of substrates, and BES have multiple product recovery with potential of industrial use; however, both have low resource recovery and poor yield. By merging the both systems together, high resource recovery can be obtained with treating the high strength wastewater. Also, it opens avenue for carbon capture and utilization along with nutrient recovery both from liquid and gaseous effluents using algal BES hybridized with AD. Use of algal BES technology for such integration can be innovative approach to boost the biohydrogen and biomass production during effluent treatment. Moreover, understanding the feasibility, techno-economics, and operational challenges of large-scale AD and BES integration is essential before moving to industrial implementation. Although there have been many recent articles discussing the various aspects of BES-AD integration (Xu et al., 2024); however, there is no article discussing about the scalability of integrated system and its market expansion for commercialization. The present article focused on upscaling challenges and market analysis of integrated system along with development before moving it for industrial commercialization. Also, shift in nutrient-water-energy based wastewater treatment through BES-AD synergy has been elaborated along with circular economy.

Access through your organization

Check access to the full text by signing in through your organization.

Section snippets

Integration of AD and BES for wastewater treatment

Anaerobic digesters can be engineered to operate bio-reactors at different organic loading rates under batch or continuous modes of operation (Chae et al., 2004, Chae et al., 2008a). During the initiation of AD, the choice of substrate depends on the complexity, loading rate, ease of handling, and feeding requirements. To support the AD process, BES has been suggested as a polishing treatment phase for resource and nutrient recovery (Xu et al., 2024). BES provides a flexible electrochemical

Sludge pretreatment in AD

Pretreatment can be provided to the sludge to improve the efficiency of AD. Such pretreatment can be performed using physical means (ultrasonication), chemical dosing (acid/alkali, fatty acids, and nitroethane), thermal treatment (heat), thermochemical processes on the primary sludge to enhance the activities of acidogenic and methanogenic populations, as well as biological pretreatment using enzymes (Kim et al., 2003, Jadhav et al., 2019). Such pretreatment accelerates the solubilization of

Synergy of BES-AD coupled system for wastewater treatment

AD is highly mature in technical and theoretical aspects, but hydrolysis and methanogenesis are the two major steps that limit the rate of the process (Baek et al., 2018, Felchner-Zwirello et al., 2012, Wang et al., 2022e). During methanogenesis, the balance between anaerobes and methanogenic archaea is the key node because the two groups have huge differences in composition, nutritive demands, growth kinetics, and microenvironment (Martins et al., 2018, Xu et al., 2022). VFAs and hydrogen, the

Energy-positive-integrated system: Outlook of scenarios

In architecture, an energy-positive system is the one wherein the energy produced from the proposed system exceeds the energy consumed from renewable resources, the carbon emission and energy cost are reduced, and the overall performance of system increases (Kumar, 2021a, Kumar and Cao, 2021).

When this concept is extended to the BES-AD integrated system, a new conception of energy-positive BES-AD integrated system can be defined. In conventional BES-AD, the external electricity is necessary to

Upscaling of BES-AD integrated system

Considering the pilot scale demonstration, Xie et al. (2023) demonstrated BES-AD (5 m3 capacity of AD with 1 m3 BES) coupling with modular electrodes for treating membrane manufacturing wastewater. The result showed that the biodegradability of refractory organics was economical at 0.9 V (0.54 A) over 1.2 V (0.8 A) applied voltage. Enrichment of core genera was spatially selective and each electrode module showed different microbial community enrichments (Xie et al., 2023). Similarly, the

Existing challenges and marketing perspectives

Recently, researchers deployed artificial intelligence (AI) and machine learning (ML) tools to predict the performance of BES-AD and accomplish high operational stability (Cheon et al., 2022). From the 1-step ML algorithm, methane yield can be predicted by using pH single data and can be applicable for pilot demonstration. Meanwhile, a combination of AI, response surface methodology, and particle swarm optimization showed a low error of 0.0579 and an R-value of 0.9870 for predicted and actual

Conclusions

Utilization of VFAs/CO2 from AD effluent for algal BES post-treatment to enhance sustainability of waste management and resource-nutrient-energy-water recovery fits well within the framework of circular economy. Furthermore, BES-AD integration holds significant potential for commercialization, given its energy-efficient nature and technical–economic viability. However, the upscaling-issues including electrochemical and microbial constraints, cost economics, and engineering design constraints

CRediT authorship contribution statement

Dipak A. Jadhav: Writing – review & editing, Writing – original draft, Visualization, Validation, Investigation, Formal analysis, Data curation, Conceptualization. Zhe Yu: Writing – review & editing, Writing – original draft, Validation, Formal analysis, Data curation, Conceptualization. Mohammed Hussien: Writing – review & editing, Writing – original draft, Validation, Formal analysis. Ju-Hyeong Kim: Writing – review & editing, Visualization, Formal analysis, Conceptualization. Wenzong Liu:

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgments

This project was supported by National Research Foundation of Korea (NRF) grants from the Korean government (MSIT) (No. RS-2023-00209009), (RS-2023- 00219497), (RS-2023-00265777), British Council Reconnect Travel grant and Brain Pool grant (2021H1D3A2A02044903). This work was carried out with support of the ‘Cooperative Research Program for Agriculture Science and Technology Development (No. PJ016259022021)’, Rural Development Administration, Republic of Korea

References (148)

RELATED ARTICLESMORE FROM AUTHOR