Operational and technical considerations for microbial electrosynthesis

Extracellular electron transfer has, in one decade, emerged from an environmental phenomenon to an industrial process driver. On the one hand, electron transfer towards anodes leads to production of power or chemicals such as hydrogen, caustic soda and hydrogen peroxide. On the other hand, electron transfer from cathodes enables bioremediation and bioproduction. Although the microbiology of extracellular electron transfer is increasingly being understood, bringing the processes to application requires a number of considerations that are both operational and technical. In the present paper, we investigate the key applied aspects related to electricity-driven bioproduction, including biofilm development, reactor and electrode design, substrate fluxes, surface chemistry, hydrodynamics and electrochemistry, and finally end-product removal/toxicity. Each of these aspects will be critical for the full exploitation of the intriguing physiological feat that extracellular electron transfer is today

Electrochemical technology enables nutrient recovery and ammonia toxicity control in anaerobic digestion

The aim of this study was to investigate the impact of an electrochemical system (ES) on the performance of an anaerobic digester during both low and high ammonium (NH4+) loading rates. For this, a Test (with ES) and Control (without ES) setup was used. Ammonia (NH3), in equilibrium with NH4+, is a toxic compound to the methanogenic community, limits the substrate loading rate and endangers process stability. We hypothesized that, through coupling of an ES to a digester, NH3 toxicity can be controlled with simultaneous recovery of this nutrient. The ES always had a temporary negative effect when switched on. However, during periods of high ammonium loading rates the CH4 production of the Test reactor was at maximum a factor 4.5 higher compared to the Control reactor, which could be explained through a combination of NH4+ extraction and electrochemical pH control. A nitrogen flux of 47 g N m-2 membrane d-1 could be obtained in the Test reactor, resulting in a current and removal efficiency of 38±5% and 28±2%, respectively. For this, an electrochemical power input 17±2 kWh kg-1 N was necessary. In addition, anodic oxidation of sulphide resulted in a significantly lower H2S emission

Biogenic palladium enhances diatrizoate removal from hospital wastewater in a microbial electrolysis cell

decrease the load of pharmaceuticals to the environment, decentralized wastewater treatment has been proposed for important point-sources such as hospitals. In this study, a microbial electrolysis cell (MEC) was used for the dehalogenation of the iodinated X-ray contrast medium diatrizoate. The presence of biogenic palladium nanoparticles (bio-Pd) in the cathode significantly enhanced diatrizoate removal by direct electrochemical reduction and by reductive catalysis using the H(2) gas produced at the cathode of the MEC. Complete deiodination of 3.3 mu M (2 mg L(-1)) diatrizoate from a synthetic medium was achieved after 24 h of recirculation at an applied voltage of -0.4 V. An equimolar amount of the deiodinated metabolite 3,5-diacetamidobenzoate (DAB) was detected. Higher cell voltages increased the dehalogenation rates, resulting in a complete removal after 2 h at -0.8 V. At this cell Voltage, the MEC was also able to remove 85% of diatrizoate from hospital effluent containing 0.5 mu M (292 mu g L(-1)), after 24 h of recirculation. Complete removal was obtained when the effluent was continuously fed at a volumetric loading rate of 204 mg diatrizoate m(-3) total cathodic compartment (TCC) day(-1) to the MEC with a hydraulic retention time of 8 h. At -0.8 V, the MEC system could also eliminate 54% of diatrizoate from spiked urine during a 24 h recirculation experiment. The final product DAB was demonstrated to be removable by nitrifying biomass, which suggests that the combination of a MEC and bio-Pd in its cathode offers potential to dehalogenate pharmaceuticals, and to significantly lower the environmental burden of hospital waste streams

(Bio)elektrochemie in de waterzuivering?

Waterzuivering is vandaag een noodzakelijke kost. Naast het verbruik van elektriciteit voor beluchting worden organische (voor denitrificatie) en anorganische (pH controle, neerslag van PO43-) chemicaliën routineus gedoseerd. Elektrochemie en bioelektrochemie kunnen hiervoor een aantal oplossingen voorzien: aangedreven door elektriciteit kan een zero-chemical-input plant vooropgesteld worden waarbij eventueel producten geoogst worden in plaats van verwerkt. In dit overzicht stellen we verschillende (bio)elektrochemische ontwikkelingen voor en evalueren we ze op toepasbaarheid in de hedendaagse waterzuivering

Principles and technology of microbial fuel cells

Microbial Fuel Cells (MFC) are bioelectrochemical systems (BES) where at least one of the two redox reactions is catalysed by a biological component (i.e. a whole bacterial cell, an enzyme or a metabolite). The involvement of biological catalysis differentiates them from chemical fuel cells (CFC). BES represents a technology capable to produce power, but also to poise an environmental site at a given redox potential. Moreover, valuable chemicals can be harvested such as hydrogen, methane, organic compounds, hydrogen peroxide or sodium hydroxide. Plenty of other application possibilities for BES have been reported at the level of ‘proof of principle’. Hence, the challenge is to upgrade BES from the lab-scale level to full-scale application and to demonstrate appropriate opportunities in terms of overall economics. Therefore, it is important to find niches where BES technology has clear cut advantages in terms of overall Life Cycle Assessment (LCA) relative to its competitors to turn BES into a mature technology. This chapter reviews recent advantages and challenges of BES from principals to applications