• Energy Research

To investigate the role of phosphorus in lipid production under nitrogen starvation conditions, five types of media possessing different nitrogen and phosphorus concentrations or their combination were prepared to culture Chlorella vulgaris. It was found that biomass production under nitrogen deficient condition with sufficient phosphorus supply was similar to that of the control (with sufficient nutrition), resulting in a maximum lipid productivity of 58.39 mg/L/day. Meanwhile, 31P NMR showed that phosphorus in the medium was transformed and accumulated as polyphosphate in cells. The uptake rate of phosphorus in cells was 3.8 times higher than the uptake rate of the control. This study demonstrates that phosphorus plays an important role in lipid production of C. vulgaris under nitrogen deficient conditions and implies a potential to combine phosphorus removal from wastewater with biodiesel production via microalgae.

Urine pretreatment has attracted increasing interest as it is able to relieve the nitrogen and phosphorus overloading problems in municipal wastewater treatment plants. In this study, an integrated process, which combines magnesium ammonium phosphate (MAP) precipitation with a microbial fuel cell (MFC), is proposed for the recovery of a slow-release fertilizer and electricity from urine. In such a two-step process, both nitrogen and phosphorus are recovered through the MAP process, and organic matters in the urine are converted into electricity in the MFCs. With this integrated process, when the phosphorus recovery is maximized without a dose of PO(4)(3-)-P in the MAP precipitation process, removal efficiencies for PO(4)(3)-P and NH(4)(+)-N of 94.6% and 28.6%, respectively, were achieved with a chemical oxygen demand (COD) of 64.9% accompanied by a power output of 2.6 W m(-3). Whereas removal efficiencies for PO(4)(3)-P and NH(4)(+)-N of 42.6% and 40%, respectively, and a COD of 62.4% and power density of 0.9 W m(-3) were obtained if simultaneous recovery of phosphorus and nitrogen was required through dosing with 620 mg L(-1) of PO(4)(3-)-P in the MAP process. This work provides a new sustainable approach for the efficient and cost-effective treatment of urine with the recovery of energy and resources.

A novel bioelectrochemical membrane reactor (BEMR), which takes advantage of a membrane bioreactor (MBR) and microbial fuel cells (MFC), is developed for wastewater treatment and energy recovery. In this system, stainless steel mesh with biofilm formed on it serves as both the cathode and the filtration material. Oxygen reduction reactions are effectively catalyzed by the microorganisms attached on the mesh. The effluent turbidity from the BEMR system was low during most of the operation period, and the chemical oxygen demand and NH(4)(+)-N removal efficiencies averaged 92.4% and 95.6%, respectively. With an increase in hydraulic retention time and a decrease in loading rate, the system performance was enhanced. In this BEMR process, a maximum power density of 4.35 W/m(3) and a current density of 18.32 A/m(3) were obtained at a hydraulic retention time of 150 min and external resister of 100 Ω. The Coulombic efficiency was 8.2%. Though the power density and current density of the BEMR system were not very high, compared with other high-output MFC systems, electricity recovery could be further enhanced through optimizing the operation conditions and BEMR configurations. Results clearly indicate that this innovative system holds great promise for efficient treatment of wastewater and energy recovery.

Microbial fuel cells (MFC) provide a new opportunity for simultaneous electricity generation and waste treatment. An improvement in the anode capacity of MFCs is essential for their scale-up and commercialization. In this work we demonstrate, for the first time, that plasma-based ion implantation could be used as an effective approach to modify carbon paper as an anode for MFC to improve its electricity-generating capacity. After the N(+) ion implantation, a decreased charge-transfer resistance is achieved, which is attributed to the increased C-N bonds after N(+) ion implantation. In addition, the surface roughness and hydrophobicity are also changed, which favor microbial adhesion on the anode surface. The cyclic voltammetry results show that both the electrochemical activity and the electron transfer are enhanced remarkably, leading to better MFC performance compared to the control. Such a plasma surface modification technique provides an effective way to modify the electrode for enhancing MFC performance for power generation.

Metal oxide semiconductors with surface homojunctions characteristic of continuous band bending and well-defined epitaxial interfaces show amazing potential for photocatalytic applications.

T finding that microorganisms can convert chemical energy to electricity via respiration has inspired intensive research interests and rapid progress of microbial fuel cell (MFC) and its various derivative technologies, which are collectively called as bioelectrochemical systems (BESs). BESs offer an opportunity to directly recover electric energy from wastewater or for other applications, such as environmental remediation and chemical synthesis. Today, while efforts in the former direction of BES are continuing, its expanded applications beyond electricity recovery are gradually becoming a new focus of research. We believe that these beneficial opportunities to apply BES technology, alternative to direct large-scale power generation, should be pursued more aggressively. Currently, there is still very limited success in scaling-up and long-term operation of BES despite of the intensive studies over the past decade, which has leads to extensive concerns about the practical feasibility of this technology. Can MFC ultimately become an energy producer as we originally expected? How far are BESs from a real-world application? These are critical questions to be answered for guiding the research efforts for BES development, especially at the point when many of the BES processes have now become close to the threshold from laboratory bench to technological implementation. It should be recognized that the practical feasibility of a BES could be closely associated with its application niches. Hence, it is interesting to know which application niche, if any, would be more practically achievable. Herein, we offer a preliminary comparison on the practicability of BES for power generation and nonelectricity-recovery applications based on a cost balance analysis. For simplification, hydrogen-producing microbial electrolysis cells (MECs) is taken as an example of the latter niches. To be a practically viable technology, BES must have acceptable costs. A recent study shows that, to meet an economically balanced operation, an MFC requires the internal resistance <40 mΩ/m (relative to anode area, hereafter the same) at a current density of 25 A/m, whereas an MEC only needs to have an internal resistance <80 mΩ/m and reaches 20 A/m current. Clearly, an economic balance of MECs is theoretically more easily achievable than MFCs. Now let us have a look at their actually achievable levels. For the most reported liter-scale MFCs the internal resistance is generally above 100 mΩ/m and the current density below 5 A/m (Figure 1). By contrast,

Microbial fuel cells (MFCs) have been conceived and intensively studied as a promising technology to achieve sustainable wastewater treatment. However, doubts and debates arose in recent years regarding the technical and economic viability of this technology on a larger scale and in a real-world applications. Hence, it is time to think about and examine how to recalibrate this technology's role in a future paradigm of sustainable wastewater treatment. In the past years, many good ideas/approaches have been proposed and investigated for MFC application, but information is scattered. Various review papers were published on MFC configuration, substrates, electrode materials, separators and microbiology but there is lack of critical thinking and systematic analysis of MFC application niche in wastewater treatment. To systematically formulate a strategy of (potentially) practical MFC application and provide information to guide MFC development, this perspective has critically examined and discussed the problems and challenges for developing MFC technology, and identified a possible application niche whereby MFCs can be rationally incorporated into the treatment process. We propose integration of MFCs with other treatment technologies to form an MFC-centered treatment scheme based on thoroughly analyzing the challenges and opportunities, and discuss future efforts to be made for realizing sustainable wastewater treatment.

Photocatalytic oxidation mediated by TiO(2) is a promising oxidation process for degradation of organic pollutants, but suffers from the decreased photocatalytic efficiency attributed to the recombination of photogenerated electrons and holes. Thus, a cost-effective supply of external electrons is an effective way to elevate the photocatalytic efficiency. Here we report a novel bioelectrochemical system to effectively reduce p-nitrophenol as a model organic pollutant with utilization of the energy derived from a microbial fuel cell. In such a system, there is a synergetic effect between the electrochemical and photocatalytic oxidation processes. Kinetic analysis shows that the system exhibits a more rapid p-nitrophenol degradation at a rate two times the sum of rates by the individual photocatalytic and electrochemical methods. The system performance is influenced by both external resistor and electrolyte concentration. Either a lower external resistor or a lower electrolyte concentration results in a higher p-nitrophenol degradation rate. This system has a potential for the effective degradation of refractory organic pollutants and provides a new way for utilization of the energy generated from conversion of organic wastes by microbial fuel cells.

SummaryThe advances in synthetic biology bring exciting new opportunities to reprogram microorganisms with novel functionalities for environmental applications. For real‐world applications, a genetic tool that enables genetic engineering in a stably genomic inherited manner is greatly desired. In this work, we design a novel genetic device for rapid and efficient genome engineering based on the intron‐encoded homing‐endonuclease empowered genome editing (iEditing). The iEditing device enables rapid and efficient genome engineering in Shewanella oneidensis MR‐1, the representative strain of the electroactive bacteria group. Moreover, combining with the Red or RecET recombination system, the genome‐editing efficiency was greatly improved, up to approximately 100%. Significantly, the iEditing device itself is eliminated simultaneously when genome editing occurs, thereby requiring no follow‐up to remove the encoding system. Then, we develop a new extracellular electron transfer (EET) engineering strategy by programming the parallel EET systems to enhance versatile EET. The engineered strains exhibit sufficiently enhanced electron output and pollutant reduction ability. Furthermore, this device has demonstrated its great potential to be extended for genome editing in other important microbes. This work provides a useful and efficient tool for the rapid generation of synthetic microorganisms for various environmental applications.