Microbial electrochemistry for bioremediation

Lack of suitable electron donors or acceptors is in many cases the key reason for pollutants to persist in the environment.Externally supplementation of electron donors or acceptors is often difficult to control and/or involves chemical additions with limited lifespan,residue formation or other adverse side effects.Microbial electrochemistry has evolved very fast in the past years–this field relates to the study of electrochemical interactions between microorganisms and solid-state electron donors or acceptors.Current can be supplied in such so-called bioelectrochemical systems(BESs)at low voltage to provide or extract electrons in a very precise manner.A plethora of metabolisms can be linked to electrical current now,from metals reductions to denitrification and dechlorination.In this perspective,we provide an overview of the emerging applications of BES and derived technologies towards the bioremediation field and outline how this approach can be game changing.

Electrochemically assisted production of biogenic palladium nanoparticles for the catalytic removal of micropollutants in wastewater treatment plants effluent

Biogenic palladium nanoparticles(bio-Pd NPs)are used for the reductive transformation and/or dehalogenation of persistent micropollutants.In this work,H2(electron donor)was produced in situ by an electrochemical cell,permitting steered production of differently sized bio-Pd NPs.The catalytic activity was first assessed by the degradation of methyl orange.The NPs showing the highest catalytic activity were selected for the removal of micropollutants from secondary treated municipal wastewater.The synthesis at different H2 flow rates(0.310 L/hr or 0.646 L/hr)influenced the bio-Pd NPs size.The NPs produced over 6 hr at a lowH2 flow rate had a larger size(D50=39.0 nm)than those produced in 3 hr at a high H2 flow rate(D50=23.2 nm).Removal of 92.1%and 44.3%of methyl orange was obtained after 30 min for the NPs with sizes of 39.0 nm and 23.2 nm,respectively.Bio-Pd NPs of 39.0 nm were used to treat micropollutants present in secondary treated municipal wastewater at concentrations ranging fromμg/L to ng/L.Effective removal of 8 compounds was observed:ibuprofen(69.5%)<sulfamethoxazole(80.6%)<naproxen(81.4%)<furosemide(89.7%)<citalopram(91.7%)<diclofenac(91.9%)<atorvastatin(>94.3%)<lorazepam(97.2%).Re-moval of fluorinated antibiotics occurred at>90%efficiency.Overall,these data indicate that the size,and thus the catalytic activity of the NPs can be steered and that the removal of challengingmicropollutants at environmentally relevant concentrations can be achieved through the use of bio-Pd NPs.

Microbial electrosynthesis of acetate from CO_(2)under hypersaline conditions

Microbial electrosynthesis(MES)enables the bioproduction of multicarbon compounds from CO_(2)using electricity as the driver.Although high salinity can improve the energetic performance of bioelectrochemical systems,acetogenic processes under elevated salinity are poorly known.Here MES under 35e60 g L^(-1)salinity was evaluated.Acetate production in two-chamber MES systems at 35 g L^(-1)salinity(seawater composition)gradually decreased within 60 days,both under-1.2 V cathode potential(vs.Ag/AgCl)and^(-1).56 A m^(-2)reductive current.Carbonate precipitation on cathodes(mostly CaCO3)likely declined the production through inhibiting CO_(2)supply,the direct electrode contact for acetogens and H2 production.Upon decreasing Ca2t and Mg2t levels in three-chamber reactors,acetate was stably produced over 137 days along with a low cathode apparent resistance at 1.9±0.6 mU m^(2)and an average production rate at 3.80±0.21 g m^(-2)d^(-1).Increasing the salinity step-wise from 35 to 60 g L^(-1)gave the most efficient acetate production at 40 g L^(-1)salinity with average rates of acetate production and CO_(2)consumption at 4.56±3.09 and 7.02±4.75 g m^(-2)d^(-1),respectively.The instantaneous coulombic efficiency for VFA averaged 55.1±31.4%.Acetate production dropped at higher salinity likely due to the inhibited CO_(2)dissolution and acetogenic metabolism.Acetobacterium up to 78%was enriched on cathodes as the main acetogen at 35 g L^(-1).Under high-salinity selection,96.5%Acetobacterium dominated on the cathode along with 34.0%Sphaerochaeta in catholyte.This research provides a first proof of concept that MES starting from CO_(2)reduction can be achieved at elevated salinity.

Water treatment and reclamation by implementing electrochemical systems with constructed wetlands

Seasonal or permanent water scarcity in off-grid communities can be alleviated by recycling water in decentralized wastewater treatment systems.Nature-based solutions,such as constructed wetlands(CWs),have become popular solutions for sanitation in remote locations.Although typical CWs can efficiently remove solids and organics to meet water reuse standards,polishing remains necessary for other parameters,such as pathogens,nutrients,and recalcitrant pollutants.Different CW designs and CWs coupled with electrochemical technologies have been proposed to improve treatment efficiency.Electrochemical systems(ECs)have been either implemented within the CW bed(ECin-CW)or as a stage in a sequential treatment(CW+EC).A large body of literature has focused on ECin-CW,and multiple scaled-up systems have recently been successfully implemented,primarily to remove recalcitrant organics.Conversely,only a few reports have explored the opportunity to polish CW effluents in a downstream electrochemical module for the electro-oxidation of micropollutants or electro-disinfection of pathogens to meet more stringent water reuse standards.This paper aims to critically review the opportunities,challenges,and future research directions of the different couplings of CW with EC as a decentralized technology for water treatment and recovery.

The next frontier of the anaerobic digestion microbiome:From ecology to process control

The anaerobic digestion process has been one of the key processes for renewable energy recovery from organic waste streams for over a century.The anaerobic digestion microbiome is,through the continuous development of novel techniques,evolving from a black box to a well-defined consortium,but we are not there yet.In this perspective,I provide my view on the current status and challenges of the anaerobic digestion microbiome,as well as the opportunities and solutions to exploit it.I consider identification and fingerprinting of the anaerobic digestion microbiome as complementary tools to monitor the anaerobic digestion microbiome.However,data availability,method-inherent biases and correct taxa identification hamper the accuracy and reproducibility of anaerobic digestion microbiome characterization.Standardisation of microbiome research in anaerobic digestion and other engineered systems will be essential in the coming decades,for which I proposed some targeted solutions.These will bring anaerobic digestion from a single-purpose energy-recovery technology to a versatile process for integrated resource recovery.It is my opinion that the exploitation of the microbiome will be a driver of innovation,and that it has a key role to play in the bio-based economy of the decades to come.

Immobilisation of electrochemically active bacteria on screen-printed electrodes for rapid in situ toxicity biosensing

are time-consuming and not sensitive enough.However,bacteria typically connect to electrodes through biofilm formation,leading to problems due to lack of uniformity or long device production times.A suitable immobilisation technique can overcome these challenges.Still,they may respond more slowly than biofilm-based electrodes because bacteria gradually adapt to electron transfer during biofilm formation.In this study,we propose a controlled and reproducible way to fabricate bacteria-modified electrodes.The method consists of an immobilisation step using a cellulose matrix,followed by an electrode polarization in the presence of ferricyanide and glucose.Our process is short,reproducible and led us to obtain ready-to-use electrodes featuring a high-current response.An excellent shelf-life of the immobilised electrochemically active bacteria was demonstrated for up to one year.After an initial 50% activity loss in the first month,no further declines have been observed over the following 11 months.We implemented our bacteria-modified electrodes to fabricate a lateral flow platform for toxicity monitoring using formaldehyde(3%).Its addition led to a 59% current decrease approximately 20 min after the toxic input.The methods presented here offer the ability to develop a high sensitivity,easy to produce,and long shelf life bacteria-based toxicity detectors.

面向有机污染物消除的“微生物、植物、电”多效耦合作用机制及低能耗型修复技术

中欧合作项目“面向有机污染物消除的‘微生物、植物、电’多效耦合作用机制及低能耗型修复技术”是由中国国家自然科学基金委和欧盟共同资助的重大国际合作项目。该项目研究领域属于环境生物技术,研究团队包括5个中方单位和17个欧方单位,项目主要围绕新有机污染物的生物降解过程和机制、低能耗生物修复技术开展研究工作。项目执行2年来,在降解污染物的微生物资源、弱电介入增效生物降解和强化电子传递、微生物3D打印等方面取得了阶段性成果的同时,项目团队还开展了有效的交流和实质性合作。未来,项目团队将克服新冠疫情影响,强化中欧双方团队内部和团队之间的合作交流,全面实现项目科学目标,圆满完成国际合作任务。

中欧环境和微生物科学家:共同担当起保护地球家园的责任

国际科技合作是促进科技进步和人类社会文明发展的重要举措,在环境保护和维护地球生态系统良好运行的目标下,最容易达成共识。中国国家自然科学基金委员会和欧盟委员会2018年和2019年分别发布了在环境生物技术领域合作的项目指南,共同支持环境生物修复技术和塑料降解微生物菌群相关领域的基础研究和成果转化。本专刊邀请了相关项目负责人介绍合作框架内项目的设计思想、主要内容以及获得的进展,并收录了在环境生物修复技术领域的基础研究和成果转化方面的论文23篇。