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Soares; Prospects in bioelectrochemical technologies for wastewater treatment. Water Sci Technol 2 November ; 78 6 : — Bioelectrochemical technologies are emerging as innovative solutions for waste treatment, offering flexible platforms for both oxidation and reduction reaction processes. A great variety of applications have been developed by utilizing the energy produced in bioelectrochemical systems, such as direct electric power generation, chemical production or water desalination.
This manuscript provides a literature review on the prospects in bioelectrochemical technologies for wastewater treatment, including organic, nutrients and metals removal, production of chemical compounds and desalination. The challenges and perspectives for scale-up were discussed. A technological strategy to improve the process monitoring and control based on big data platforms is also presented.
The management of water resources has been strongly influenced by the water shortage. Linked to it, the high costs associated with wastewater treatment call for a consideration of water use rationalization, adequacy of treatment methods and the viability of reuse techniques Mirre et al. Conventional wastewater treatment technologies are focused on purification rather than resource recovery.
In the field of biological treatment, the activated sludge process is the most common Shariati et al. However, these technologies consume large amounts of energy due to the necessity for aeration, in order to provide the amount of oxygen required for microorganisms involved in the process Ren et al. Nevertheless, this power consumption can be avoided through the adoption of innovative engineering processes, promoting resources recovery and providing a reusable water resource Chen et al.
In this context emerges the technologies based on bioelectrochemical systems BES. BES have a range of potential configurations and applications, including wastewater treatment, biofuels production, water desalination, biosensors and as a source of energy power for remote areas Logan et al. However, there are several challenges to be overcome in order to translate these technologies into commercial applications.
Given these prospects, this paper reviews the potential applications of BES to treat wastewater, focusing on the challenges and opportunities to improve their performance. Also, a technological strategy to improve the process monitoring and control based on big data platforms is presented. The basic BES principle is the reaction of microbial oxidation. Studies on BES have been focused on wastewater treatment, energy recovery, desalination, and synthesis of high-value products ElMekawy et al.
There are several effluents with potential application, such as sewage Kim et al. Organic wastes contain more internal energy than the amount required to treat them. However, this energetic potential is not exploited yet, mainly when traditional technologies are applied to treat wastewater. Under aerobic conditions, for example, the energetic consumption for aeration systems is around 0.
On the other hand, BES consume small amounts of energy and can simultaneously generate useful products, such as electricity, hydrogen, and chemicals, such as carboxylic acids, caustic compounds, acetate, hydrogen peroxide, methane, ethanol, and hydrogen Xu et al.
The low biomass yield is another positive factor, saving costs with sludge disposal. As an MFC is based in a biofilm system, and the cell yield of exoelectrogenic bacteria 0. The removal of nutrients in BES has also been studied Park et al. Sotres et al. The performance of a microbial electrolysis cell MEC for autotrophic nitrate removal from groundwater was assessed by Cecconet et al. A promising single-chamber MFC was proposed by Wang et al. Cusick et al.
Results indicated that energy consumption 0. Metal contamination is an environmental concern, as these compounds are not biodegraded and can be transferred across trophic levels, accumulating in the biota Nancharaiah et al.
In BES, metals can be spontaneously reduced on the cathode due to favorable half-cell redox relative to organic matter Cheng et al. There are several mechanisms related to the cathodic metal recovery, involving the direct metal recovery using biotic or abiotic cathodes, supplemented or not by an external power source. Carbon dioxide has been captured and used to produce organic compounds like methane for fuel and bioplastics e.
Watson et al. An increase in the current production was observed when the number of cell pairs was duplicated from 5 to 10 cell pairs. With 10 cell pairs, hydrogen yield was 1. By using acetate as the electron donor, Rabaey et al. The MDC appears as an innovative BES option to desalination technologies, as they can convert the energy stored in wastewater directly into electricity and utilize it in situ to drive desalination Perazzoli et al.
MDCs can be used as either a stand-alone for simultaneous organic and salt removal with energy production or a pretreatment for conventional desalination processes such as reverse osmosis, reducing salt concentration, and minimizing energy consumption and membrane fouling Li et al. The development of MDC-based systems to treat wastewater integrating both nitrogen removal, electricity generation and desalination is also possible.
In this case, the cathodic chamber can be fed with nitrogen ions e. However, studies exploiting this possibility are scarce Meng et al. BES applications are attractive as a complement to traditional wastewater treatment technologies, reducing energetic requirements as well as recovering resources and synthesizing new products by using wastes as raw material.
Several studies have demonstrated the ability of BES to treat wastewater with simultaneous electricity production Liu et al. However, the small amount of energy generated would be sufficient only for low-power applications. Thus, the simple production of electricity is not yet economically feasible when comparing well-established processes, such as anaerobic digestion.
Alternatively, it would be an advantage to utilize the electricity to conduct desalination Al-Mamun et al. Studies have suggested the integration of BES into the anaerobic processes, improving acidogenesis, and hydrogen or methane production Liu et al. These results show that energy recovery and organic removal from wastewater can be more effective with MFCs than MECs, but hydrogen production from MECs using wastewater as a carbon source can also be cost-effective, based on electrical energy requirements.
Substantial advances have occurred in the last years; however, the major bottlenecks to scale-up BES include the low power densities, and high capital and operational expenses Seelam et al. In fact, to overcome these gaps it is necessary to improve the electron transfer and electrode materials, reduce the costs involving membranes and separators, improve reactor design and also the technologies for process monitoring and control.
The successful BES applications and research efforts require a better understanding of the exoelectrogenic bacteria and their biochemical pathways used to release electrons to the acceptors outside the cell Logan In general, electrode materials should ideally be biocompatible, conductive, porous, easily made at low cost, recyclable, and scalable.
In addition, they should possess high specific surface area, corrosion resistance, and high mechanical strength Kalathil et al. General classification of electrode materials used for BES based on Sonawane et al. With recent advances in materials science and nanotechnology, the development of three-dimensional electrodes is promising, for example, graphene-based materials Tang et al.
Carbon paste electrodes also can be useful for this application. These electrodes are made from a paste of finely granulated carbon mixed with mineral oil like Nujol , paraffin oil or silicon grease; where the paste is packed into the electrode body cavity.
For more details, a review of recent developments of anode materials for MFCs is presented by Sonawane et al. The membrane, as well as structural materials, play a critical role in continuing the development of BES, because the architecture, materials and overall geometry, significantly affect performance levels and unit cost Santoro et al.
According to Daud et al. In the case of membrane-based technologies, the main challenge comes from membrane fouling biofilm growth and scaling hardness-causing cation deposition Song et al. Porous materials, such as ceramic, terracotta, earthenware, mullite and so many other clay materials, are promising materials.
However, the porosity, proton conductivity, and brittleness need to be improved Winfield et al. Khalili et al. According to the authors, due to the low production cost, high mechanical strength and increased output power density of the MFC, these separators proved to be a suitable alternative to replace costly polymeric membranes.
Chitosan-based membranes have been developed for biofuel cell applications Ikram et al. Colloidal silica and chitosan were the most sustainable options. Cathodes prepared with 2. As can be observed, these studies report the potential application of alternative materials for advancing BES, as they are not only comparable with conventional ion exchange membranes in terms of performance, but also substantially less expensive. BES commercialization could be limited by the reduction of the power produced at larger scales.
In this case, the major difficulty is to maintain the relationship between reactor geometry and electrode. In experiments assessing different MFC configurations treating brewery and piggery wastewaters, a higher power density of 4.
These findings show that electrode surface areas need to be maintained for larger reactor sizes Logan et al. Continuous research is needed to better understand and find appropriate solutions for those gaps addressed here.
It is fundamental to develop low-cost and effective materials associated with pilot-scale studies to assess their performance and maintenance at a larger scale, including parameters such as longevity and behavior with variations in wastewater composition and temperature for example to control fouling on electrodes Hatzell et al. The successful application of new technologies is highly dependent on the development of reliable strategies for process monitoring, control, and optimization.
In the next years, the investments in advanced solutions for data management and analytics are expected to grow by Due to the dynamic nature of the BES operations, there are numerous variables influencing process performance which need to be closely monitored, such as periods with fluctuations in the volume of influent to be treated, climatic conditions and electricity production variations.
Therefore, improved sensors and advanced analytics tools bring possibilities to utilize this information to predict, identify and correct eventual failures that affect the process performance, thus reducing losses and energy consumption Helmbrecht et al.
Considering a machine with a random-access memory RAM memory processing capacity of 8 GB, we assume the following cases:. It should be noted that in systems using smart sensors there is a need for high sampling rates with measurement intervals lower than 1 second Nielsen et al.
Big data platforms are attractive as they offer support to scale a large number of metrics. Also, they are strongly consistent data will not be lost , fault tolerant if any component fails, the system will not stop and can distribute the system in several infrastructures Oussous et al. Data acquisition occurs during the steps of monitoring and control.
According to Boe et al. This is mainly due to the complexity of the organic residues and fluctuations composition, pH, temperature, conductivity that occur during the operating cycles Recio-Garrido et al. These fluctuations can result in the system performance drop — electrical properties Gonzalez del Campo et al.
After the acquisition, data are processed, allowing extraction of knowledge and value. To process big data with scalability and high performance there are two main tools: Hadoop MapReduce and Spark. MapReduce is, therefore, suitable for cases where data operations are static, especially when processing is done in batches. However, when there is a need for continuous data analysis i. Once processed, data are stored in distributed file systems such as Hadoop distributed file systems.
In this step, files are divided into blocks that can be accessed simultaneously and replicated to be fault tolerant Garcia et al. All this information is extracted and managed by web services in the cloud computing Oussous et al.
Bioelectrochemical Systems: An Outlook for Practical Applications
Bioelectrochemical systems BESs hold great promise for sustainable production of energy and chemicals. This review addresses the factors that are essential for practical application of BESs. First, we compare benefits value of products and cleaning of wastewater with costs capital and operational costs. We compare these maximum resistances to reported internal resistances and current densities with special focus on cathodic resistances. Whereas the current densities of MFCs still need to be increased considerably i. For MFCs, the production of high-value products in combination with electricity production and wastewater treatment is a promising route.
Bioelectrochemical systems: an outlook for practical applications.
Skip to search form Skip to main content You are currently offline. Some features of the site may not work correctly. DOI: Bioelectrochemical systems BESs hold great promise for sustainable production of energy and chemicals.