Abstract: Nitrate contamination of groundwater has been recognized as a significant environmental problem world widely. Sulfur-driven mixotrophic denitrification has been demonstrated as a promising groundwater treatment process, which though plays an important role in nitrous oxide (N2O) emissions, significantly contributing to the overall carbon footprint of the system. However, the current process optimizations only focus on nitrate removal and excess sulfate control, with the N2O emission being ignored. In this work, an integrated mathematical model was proposed to evaluate the N2O emission as well as the excess sulfate production and carbon source utilization in sulfur-driven mixotrophic denitrification process. In this model, autotrophic and heterotrophic denitrifiers use their corresponding electron donors (sulfur and organic matter, respectively) to reduce nitrate to nitrogen gas, with each modeled as three-step denitrification (NO3 to N-2 via NO2 and N2O) driven by sulfur or organic matter to describe all potential N2O accumulation steps. The developed model, employing model parameters previously reported in literature, was successfully validated using N2O and sulfate data from two mixotrophic denitrification systems with different initial conditions. Modeling results revealed substantial N2O accumulation due to the relatively low autotrophic N2O reduction activity as compared to heterotrophic N2O reduction activity, explaining the observation that higher carbon source addition resulted in lower N2O accumulation in sulfur-driven mixotrophic denitrifying system. Based on the validated model, optimizations of the overall system performance were carried out. Application of the model to simulate long-term operations of sulfur-driven mixotrophic denitrification process indicates that longer sludge retention time reduces N2O emission due to better retention of active biomass. High-level total nitrogen removal with significant N2O emission mitigation, appropriate excess sulfate control and maximized COD utilization can be achieved simultaneously through controlling the influent nitrate and COD concentrations. (C) 2017 Elsevier Ltd. All rights reserved.

Abstract: Hierarchical semiconductors are the most important photocatalysts, especially for visible light-induced hydrogen production from water splitting. We demonstrate herein a hierarchical electrostatic assembly approach to hierarchical CdS/m-TiO2/G ternary photocatalyst, which exhibits high photoactivity and excellent photostability (more than twice the activity of pure CdS while 82% of initial photoactivity remained after 15 recycles during 80 h irradiation). The ternary nanojunction effect of the photocatalyst has been investigated from orbitals hybrid, bonding energy to atom-stress distortion and nano-interface fusion. And a coherent separation mechanism of charge carriers in the ternary system has been proposed at an atomic/nanoscale. This work offers a promising way to inhibit the photocorrosion of CdS and, more importantly, provide new insights for the design of ternary nanostructured photocatalysts with an ideal heterojunction.

Abstract: Five different pre-treatments were investigated to enhance the solubilisation and anaerobic biodegradability of kitchen waste (
KW) in thermophilic batch and continuous tests. In the batch solubilisation tests, the highest and the lowest solubilisation efficiency were achieved with the thermo-acid and the pressuredepressure pre-treatments, respectively. However, in the batch biodegradability tests, the highest cumulative biogas production was obtained with the pressuredepressure method. In the continuous tests, the best performance in terms of an acceptable biogas production efficiency of 60% and stable in-reactor CODs and VFA concentrations corresponded to the pressuredepressure reactor, followed by freezethaw, acid, thermo-acid, thermo and control. The maximum OLR (5 g COD L−1 d−1) applied in the pressuredepressure and freezethaw reactors almost doubled the control reactor. From the overall analysis, the freezethaw pre-treatment was the most profitable process with a net potential profit of around 11.5 ton−1 KW.

Abstract: Nitrogen oxides (NOx) and particulate matter (PM) currently are the main pollutants emitted by diesel engines. While there is a start in using hybrid and electric cars, ships will still be fueled by mineral oil products. In the quest to achieve zero-pollution and carbon-free shipping, alternative forms of energy carriers must be found to replace the commonly used mineral oil products. One of the possible alternative fuels is biodiesel. This paper explores the optimization of the composition of biodiesel in order to reduce the concentration of particulate matter and NOx in exhaust gases of a one-cylinder diesel generator.

Abstract: Air quality currently poses a major risk to human health worldwide. Transportation is one of the principal contributors to air pollution due to the quality of exhaust gases. For example, the widely used diesel fuel is a significant source of nitrogen oxides (NOx) and particulate matter (PM). To reduce the content NOx and PM, different oxygenated compounds were mixed into a mineral diesel available at the pump, and their effect on the composition of exhaust gas emissions was measured using a one-cylinder diesel generator. In this setup, adding methanol gave the best relative results. The addition of 2000 ppm of methanol decreased the content of NO by 56%, 2000 ppm of isopropanol decreased NO2 by 50%, and 2000 ppm ethanol decreased PM by 63%. An interesting question is whether it is possible to reduce the impact of hazardous components in the exhaust gas even more by adding oxygenates to biodiesels. In this article, alcohol is added to biodiesel in order to establish the impact on PM and NOx concentrations in the exhaust gases. Adding methanol, ethanol, and isopropanol at concentrations of 2000 ppm and 4000 ppm did not improve NOx emissions. The best results were using pure RME for a low NO content, pure diesel for a low NO2 content, and for PM there were no statistically significant differences.

Abstract: Enhanced bioremediation of petroleum hydrocarbons in two biopiles was quantified by high-performance liquid chromatography (HPLC) followed by comprehensive two-dimensional gas chromatography (GCXGC). The attenuation of 34 defined hydrocarbon classes was calculated by HPLCGCXGC analysis of representative biopile samples at start-up and after 18 weeks of biopile operation. In general, a-cyclic alkanes were most efficiently removed from the biopiles, followed by monoaromatic hydrocarbons. Cycloalkanes and polycyclic aromatic hydrocarbons (PAHs) were more resistant to degradation. A-cyclic biomarkers farnesane, trimethyl-C13, norpristane, pristane and phytane dropped to only about 10% of their initial concentrations. On the other hand, C29C31 hopane concentrations remained almost unaltered after 18 weeks of biopile operation, confirming their resistance to biodegradation. They are thus reliable indicators to estimate attenuation potential of petroleum hydrocarbons in biopile processed soils.

Abstract: HPLC-GCXGC/FID (high-performance liquid chromatography followed by comprehensive two-dimensional gas chromatography with flame-ionization detection) and GCXGC/ToF-MS (comprehensive two-dimensional gas chromatography with time-of-flight mass spectrometry) were used to study the biodegradation of petroleum hydrocarbons in soil microcosms during 20 weeks. Two soils were studied: one spiked with fresh diesel and one field sample containing weathered diesel-like oil. Nutrient amended and unamended samples were included. Total petroleum hydrocarbon (TPH) levels in spiked soil decreased from 15000 to 7500 mg/kg d.m. and from 12000 to 4000 mg/kg d.m. in the field soil. Linear alkanes and aromatic hydrocarbons were better biodegradable (>60% degraded) than iso-alkanes; cycloalkanes were least degradable (<40%). Aromatic hydrocarbons up to three rings showed better degradability than n-alkanes. GCXGC/ToF-MS analysis of leaching water showed that initially various oxygenated hydrocarbons were produced. Compound peaks seemed to move up and rightward in the GCXGC chromatograms, indicating that more polar and heavier compounds were formed as biodegradation proceeded. Nutrient amendment can increase TPH removal rates, but had adverse effects on ecotoxicity and leaching potential in our experiment. This was explained by observed shifts in the soil microbial community. Ecotoxicity assays showed that residual TPH still inhibited cress (Lepidium sativum) seed germination, but the leaching water was no longer toxic toward luminescent bacteria (Vibrio fischeri).

Abstract: This research study reports the assessment of complementary split ring resonators based on Gielis transformation as basic elements for the design of high‐performance microwave components in printed technology. From the electromagnetic simulation of said structures, suitable equivalent circuit models are extracted and analyzed. Physical prototypes are fabricated and tested for design validation. The obtained results confirm that the adoption of supershaped geometries enables the synthesis of very compact scalable microwave filters.

Abstract: Wastewater is typically treated by the conventional activated sludge process, which suffers from an inefficient overall energy balance. The high-rate contact stabilization (HiCS) has been proposed as a promising primary treatment technology with which to maximize redirection of organics to sludge for subsequent energy recovery. It utilizes a feast famine cycle to select for bioflocculation, intracellular storage, or both. We optimized the HiCS process for organics recovery and characterized different biological pathways of organics removal and recovery. A total of eight HiCS reactors were operated at 15 degrees C at short solids retention times (SRT; 0.24-2.8 days), hydraulic contact times (t(c); 8 and 15 min), and stabilization times (t(s); 15 and 40 min). At an optimal SRT between 0.5 and 1.3 days and t(c) of 15 min and t(s) of 40 min, the HiCS system oxidized only 10% of influent chemical oxygen demand (COD) and recovered up to 55% of incoming organic matter into sludge. Storage played a minor role in the overall COD removal, which was likely dominated by aerobic biomass growth, bioflocculation onto extracellular polymeric substances, and settling. The HiCS process recovers enough organics to potentially produce 28 kWh of electricity per population equivalent per year by anaerobic digestion and electricity generation. This inspires new possibilities for energy-neutral wastewater treatment.

Abstract: High-rate activated sludge processes allow for the recovery of organics and energy from wastewaters. These systems are operated at a short sludge retention time and high sludge-specific loading rates, which results in a higher sludge yield and better digestibility than conventional, low-rate activated sludge. Little is known about the microbial ecology of high-rate systems. In this work, we address the need for a fundamental understanding of how high-rate microbial communities differ from low-rate communities. We investigated the high-rate and low-rate communities in a sewage treatment plant in relation to environmental and operational variables over a period of ten months. We demonstrated that (1) high-rate and low-rate communities are distinctly different in terms of richness, evenness and composition, (2) high-rate community dynamics are more variable and less shaped by deterministic factors compared to low-rate communities, (3) sub-communities of continuously core and transitional members are more shaped by deterministic factors than the continuously rare members, both in high-rate and low-rate communities, and (4) high-rate community members showed a co-occurrence pattern similar to that of low-rate community members, but were less likely to be correlated to environmental and operational variables. These findings provide a basis for further optimization of high-rate systems, in order to facilitate resource recovery from wastewater.

Abstract: The impregnation of size-controlled gold nanoparticles (AuNPs) on an anatase TiO2 structure (AuNPs@TiO2) was studied for the photoelectrochemical detection of hydroquinone (HQ) under visible light illumination integrated into a flow injection analysis (FIA) setup. The crystalline form of TiO2 was preserved during synthesis and the homogeneous distribution of AuNPs over the TiO2 structure was confirmed. Its photoelectrocatalytic activity was improved due to the presence of AuNPs, preventing charge recombination in TiO2 and improving its light absorption ability by the surface plasmon resonance effect (SPR). The FIA system was used in order to significantly reduce the electrode fouling during electroanalysis through periodic washing steps of the electrode surface. During the amperometric detection process, reactive oxygen species (ROS), generated by visible light illumination of AuNPs@TiO2, participate in the oxidation process of HQ. The reduction of the oxidized form of HQ, i.e. benzoquinone (BQ) occurs by applying a negative potential and the measurable amperometric response will be proportional to the initial HQ concentration. The influencing parameters on the response of the amperometric photocurrent such as applied potential, flow rate and pH were investigated. The linear correlation between the amperometric response and the concentration of HQ was recorded (range 0.0125 – 1.0 µM) with a limit of detection (LOD) of 33.8 nM and sensitivity of 0.22 A M−1 cm−2. In this study, we illustrated for the first time that the impregnation of AuNPs in TiO2 allows the sensitive detection of phenolic substances under green laser illumination by using a photoelectrochemical flow system.

Abstract: Electromagnetic design problems involve optimizing multiple parameters that are nonlinearly related to objective functions. Traditional optimization techniques require significant computational resources that grow exponentially as the problem size increases. Therefore, a method that can produce good results with moderate memory and computational resources is desirable. Bioinspired optimization methods, such as particle swarm optimization (PSO), are known for their computational efficiency and are commonly used in various scientific and technological fields. In this article we explore the potential of advanced PSO-based algorithms to tackle challenging electromagnetic design and analysis problems faced in real-life applications. It provides a detailed comparison between conventional PSO and its quantum-inspired version regarding accuracy and computational costs. Additionally, theoretical insights on convergence issues and sensitivity analysis on parameters influencing the stochastic process are reported. The utilization of a novel quantum PSO-based algorithm in advanced scenarios, such as reconfigurable and shaped lens antenna synthesis, is illustrated. The hybrid modeling approach, based on the unified geometrical description enabled by the Gielis Transformation, is applied in combination with a suitable quantum PSO-based algorithm, along with a geometrical tube tracing and physical optics technique for solving the inverse problem aimed at identifying the geometrical parameters that yield optimal antenna performance.

Abstract: Electroporation technique is widely used in biotechnology and medicine for the transport of various molecules through the membranes of biological cells. Different mathematical models of electroporation have been proposed in the literature to study pore formation in plasma and nuclear membranes. These studies are mainly based on models using a single isolated cell with a canonical shape. In this work, a spacetime (x,y,t) multiphysics model based on quasi-static Maxwells equations and nonlinear Smoluchowskis equation has been developed to investigate the electroporation phenomenon induced by pulsed electric field in multicellular systems having irregularly shape. The dielectric dispersion of the cell compartments such as nuclear and plasmatic membranes, cytoplasm, nucleoplasm and external medium have been incorporated into the numerical algorithm, too. Moreover, the irregular cell shapes have been modeled by using the Gielis transformations.

Abstract: In this work, a nonlinear dispersive multiphysic model based on Maxwell and asymptotic Smoluchowsky equations has been developed to analyze the electroporation phenomenon induced by pulsed electric field on biological cells. The irregular plasma membrane geometry has been modeled by incorporating in the numerical algorithm the Gielis superformula as well as the dielectric dispersion of the plasma membrane has been modeled using the multi-relaxation Debye-based relationship. The study has been carried out with the aim to compare our model implementing a thin plasma membrane with the simplified model in which the plasma membrane is modeled as a distributed impedance boundary condition. The numerical analysis has been performed exposing the cell to external electric pulses having rectangular shapes. By an inspection of the obtained results, significant differences can be highlighted between the two models confirming the need to incorporate the effective thin membrane into the numerical algorithm to well predict the cell response to the pulsed electric fields in terms of transmembrane voltages and pore densities, especially when the cell is exposed to external nanosecond pulses.