Rheological properties of thermally treated and digested sludge: Implications for energy requirements of pumps and agitators.

Understanding sludge rheology and optimizing equipment performance is crucial for energy efficiency in wastewater treatment plants (WWTPs). This study examined sludge rheology after thermal hydrolysis pre-treatment (THP) at 60, 80, and 120 °C for 2 h, followed by anaerobic digestion (AD) at 37 °C for 20 days, and assessed impacts on pump and agitator performance. Post-treatment, sludge showed reduced viscosity and improved flowability, indicated by changes in Herschel-Bulkley parameters, enhancing pump and agitator efficiency, particularly at 120 °C.

Mechanisms of extracellular electron transfer in anaerobic methanotrophic archaea.

Anaerobic methanotrophic (ANME) archaea are environmentally important, uncultivated microorganisms that oxidize the potent greenhouse gas methane. During methane oxidation, ANME archaea engage in extracellular electron transfer (EET) with other microbes, metal oxides, and electrodes through unclear mechanisms. Here, we cultivate ANME-2d archaea ('Ca.

Comparing theoretical and practical biomass yields calls for revisiting thermodynamic growth models for electroactive microorganisms.

Research on electroactive microorganisms (EAM) often focuses either on their physiology and the underlying mechanisms of extracellular electron transfer or on their application in microbial electrochemical technologies (MET). Thermodynamic understanding of energy conversions related to growth and activity of EAM has received only a little attention. In this study, we aimed to prove the hypothesized restricted energy harvest of EAM by determining biomass yields by monitoring growth of acetate-fed biofilms presumably enriched in Geobacter, using optical coherence tomography, at three anode potentials and four acetate concentrations.

Starvation combined with constant anode potential triggers intracellular electron storage in electro-active biofilms.

The accumulation of electrons in the form of Extracellular Polymeric Substances (EPS) and poly-hydroxyalkanoates (PHA) has been studied in anaerobic processes by adjusting the access of microorganisms to the electron donor and final electron acceptor. In Bio-electrochemical systems (BESs), intermittent anode potential regimes have also recently been used to study electron storage in anodic electro-active biofilms (EABfs), but the effect of electron donor feeding mode on electron storage has not been explored. Therefore, in this study, the accumulation of electrons in the form of EPS and PHA was studied as a function of the operating conditions.

Maximum thickness of non-buffer limited electro-active biofilms decreases at higher anode potentials.

The accumulation of protons in electro-active biofilms (EABfs) has been reported as a critical parameter determining produced currents at the anode since the very beginning of the studies on Bio-electrochemical systems (BESs). Even though the knowledge gained on the influence of this parameter on the produced currents, its influence on EABfs growth is frequently overlooked. In this study, we quantified EABfs thicknesses in real-time and related them to the produced current at three buffer concentrations, two anode potentials and two acetate concentrations.

Effects of Current on the Membrane and Boundary Layer Selectivity in Electrochemical Systems Designed for Nutrient Recovery.

During electrochemical nutrient recovery, current and ion exchange membranes (IEM) are used to extract an ionic species of interest (e.g., ion) from a mixture of multiple ions.

Opportunities for visual techniques to determine characteristics and limitations of electro-active biofilms.

Optimization of bio-electrochemical systems (BESs) relies on a better understanding of electro-active biofilms (EABfs). These microbial communities are studied with a range of techniques, including electrochemical, visual and chemical techniques. Even though each of these techniques provides very valuable and wide-ranging information about EABfs, such as performance, morphology and biofilm composition, they are often destructive.

Ammonia recovery from anaerobic digester centrate using onsite pilot scale bipolar membrane electrodialysis coupled to membrane stripping.

Ammonia recovery from centrate of an anaerobic digester was investigated using an onsite bipolar-electrodialysis (BP-ED) pilot scale plant coupled to two liquid/liquid membrane contactor (LLMC) modules. To investigate the process performance and robustness, the pilot plant was operated at varying current densities, load ratio (current to nitrogen loading), and in continuous and intermittent current (Donnan) mode. A higher load ratio led to higher total ammonium nitrogen (TAN, sum of ammonia and ammonium) removal efficiency, whereas the increase in the applied current did not have a significant impact the TAN removal efficiency.

Methane-Dependent Extracellular Electron Transfer at the Bioanode by the Anaerobic Archaeal Methanotroph " Methanoperedens".

Anaerobic methanotrophic (ANME) archaea have recently been reported to be capable of using insoluble extracellular electron acceptors extracellular electron transfer (EET). In this study, we investigated EET by a microbial community dominated by " Methanoperedens" archaea at the anode of a bioelectrochemical system (BES) poised at 0 V vs. standard hydrogen electrode (SHE), in this way measuring current as a direct proxy of EET by this community.

The effect of intermittent anode potential regimes on the morphology and extracellular matrix composition of electro-active bacteria.

Electro-active bacteria (EAB) can form biofilms on an anode (so-called bioanodes), and use the electrode as electron acceptor for oxidation of organics in wastewater. So far, bioanodes have mainly been investigated under a continuous anode potential, but intermittent anode potential has resulted in higher currents and different biofilm morphologies. However, little is known about how intermittent potential influences the electron balance in the anode compartment.

Effective orthophosphate removal from surface water using hydrogen-oxidizing bacteria: Moving towards applicability.

Effective orthophosphate removal strategies are needed to counteract eutrophication and guarantee water quality. Previously, we established that hydrogen-oxidizing bacteria (HOB) have the ability to remove orthophosphate from artificial surface water. In the present study, we expand the application of the HOB orthophosphate removal strategy (1) to treat artificial surface water with low initial orthophosphate concentrations, (2) to treat real surface water and real wastewater effluent, and (3) to remove orthophosphate continuously.

Donnan Dialysis for scaling mitigation during electrochemical ammonium recovery from complex wastewater.

Inorganic scaling is often an obstacle for implementing electrodialysis systems in general and for nutrient recovery from wastewater specifically. In this work, Donnan dialysis was explored, to prevent scaling and to prolong operation of an electrochemical system for TAN (total ammonia nitrogen) recovery. An electrochemical system was operated with and without an additional Donnan dialysis cell, while being supplied with synthetic influent and real digested black water.

Minimal Bipolar Membrane Cell Configuration for Scaling Up Ammonium Recovery.

Electrochemical systems for total ammonium nitrogen (TAN) recovery are a promising alternative compared with conventional nitrogen-removal technologies. To make them competitive, we propose a new minimal stackable configuration using cell pairs with only bipolar membranes and cation-exchange membranes. The tested bipolar electrodialysis (BP-ED) stack included six cell pairs of feed and concentrate compartments.

Enrichment of Hydrogen Oxidizing Bacteria from High Temperature and Salinity Environments.

There is an urgent need for sustainable protein supply routes with low environmental footprint. Recently, the use of hydrogen oxidizing bacteria (HOB) as a platform for high quality microbial protein (MP) production has regained interest. This study aims to investigate the added value of using conditions such as salt and temperature to steer HOB communities to lower diversities, while maintaining a high protein content and a high quality amino acid profile.

Enhanced Phototrophic Biomass Productivity through Supply of Hydrogen Gas.

Industrial production of phototrophic microorganisms is often hindered by low productivity due to limited light availability and therefore requires large land areas. This letter demonstrates that supply of hydrogen gas (H) increases in phototrophic biomass productivity compared to a culture growing on light only. Experiments were performed growing in batch bottles, with and without H in the headspace, which were exposed to light intensities of 70 and 100 μmol/m/s.

Hydrogen oxidizing bacteria are capable of removing orthophosphate to ultra-low concentrations in a fed batch reactor configuration.

This paper proposes the use of hydrogen oxidizing bacteria (HOB) for the removal of orthophosphate from surface water as treatment step to prevent cyanobacterial blooms. To be effective as an orthophosphate removal strategy, an efficient transfer of hydrogen to the HOB is essential. A trickling filter was selected for this purpose.

Combination of bioelectrochemical systems and electrochemical capacitors: Principles, analysis and opportunities.

Bioelectrochemical systems combine electrodes and reactions driven by microorganisms for many different applications. The conversion of organic material in wastewater into electricity occurs in microbial fuel cells (MFCs). The power densities produced by MFCs are still too low for application.

Microbial Community and Metabolic Activity in Thiocyanate Degrading Low Temperature Microbial Fuel Cells.

Thiocyanate is a toxic compound produced by the mining and metallurgy industries that needs to be remediated prior to its release into the environment. If the industry is situated at high altitudes or near the poles, economic factors require a low temperature treatment process. Microbial fuel cells are a developing technology that have the benefits of both removing such toxic compounds while recovering electrical energy.

Haloalkaliphilic microorganisms assist sulfide removal in a microbial electrolysis cell.

Several industrial processes produce toxic sulfide containing streams that are often scrubbed using caustic solutions. An alternative, cost effective sulfide treatment method is bioelectrochemical sulfide removal. For the first time, a haloalkaliphilic sulfide-oxidizing microbial consortium was introduced to the anodic chamber of a microbial electrolysis cell operated at alkaline pH and with 1.

Energy-Efficient Ammonia Recovery in an Up-Scaled Hydrogen Gas Recycling Electrochemical System.

Nutrient and energy recovery is becoming more important for a sustainable future. Recently, we developed a hydrogen gas recycling electrochemical system (HRES) which combines a cation exchange membrane (CEM) and a gas-permeable hydrophobic membrane for ammonia recovery. This allowed for energy-efficient ammonia recovery, since hydrogen gas produced at the cathode was oxidized at the anode.

In situ Biofilm Quantification in Bioelectrochemical Systems by using Optical Coherence Tomography.

Detailed studies of microbial growth in bioelectrochemical systems (BESs) are required for their suitable design and operation. Here, we report the use of optical coherence tomography (OCT) as a tool for in situ and noninvasive quantification of biofilm growth on electrodes (bioanodes). An experimental platform is designed and described in which transparent electrodes are used to allow real-time, 3D biofilm imaging.

Gas diffusion electrodes improve hydrogen gas mass transfer for a hydrogen oxidizing bioanode.

Background: Bioelectrochemical systems (BESs) are capable of recovery of metals at a cathode through oxidation of organic substrate at an anode. Recently, also hydrogen gas was used as an electron donor for recovery of copper in BESs. Oxidation of hydrogen gas produced a current density of 0.

Prototype of a scaled-up microbial fuel cell for copper recovery.

Background: Bioelectrochemical systems (BESs) enable recovery of electrical energy through oxidation of a wide range of substrates at an anode and simultaneous recovery of metals at a cathode. Scale-up of BESs from the laboratory to pilot scale is a challenging step in the development of the process, and there are only a few successful experiences to build on. This paper presents a prototype BES for the recovery of copper.

Mixed Culture Biocathodes for Production of Hydrogen, Methane, and Carboxylates.

Formation of hydrogen, methane, and organics at biocathodes is an attractive new application of bioelectrochemical systems (BESs). Using mixed cultures, these products can be formed at certain cathode potentials using specific operating conditions, of which pH is important. Thermodynamically, the reduction of CO to methane is the most favorable reaction, followed by reduction of CO to acetate and ethanol, and hydrogen.

Hydrogen Gas Recycling for Energy Efficient Ammonia Recovery in Electrochemical Systems.

Recycling of hydrogen gas (H) produced at the cathode to the anode in an electrochemical system allows for energy efficient TAN (Total Ammonia Nitrogen) recovery. Using a H recycling electrochemical system (HRES) we achieved high TAN transport rates at low energy input. At a current density of 20 A m, TAN removal rate from the influent was 151 g m d at an energy demand of 26.