Mixtures of chlorinated ethenes and ethanes are often found at contaminated sites. In this study, we undertook a systematic investigation of the inhibitory effects of 1,1,1-trichloroethane (1,1,1-TCA) and 1,1-dichloroethane (1,1-DCA) on chlorinated ethene dechlorination in three distinct Dehalococcoides-containing consortia. To focus on inhibition acting directly on the reductive dehalogenases, dechlorination assays used cell-free extracts prepared from cultures actively dechlorinating trichloroethene (TCE) to ethene. The dechlorination assays were initiated with TCE, cis-1,2-dichloroethene (cDCE), or vinyl chloride (VC) as substrates and either 1,1,1-TCA or 1,1-DCA as potential inhibitors. 1,1,1-TCA inhibited VC dechlorination similarly in cell suspension and cell-free extract assays, implicating an effect on the VC reductases associated with the dechlorination of VC to nontoxic ethene. Concentrations of 1,1,1-TCA in the range of 30-270 μg/L reduced VC dechlorination rates by approximately 50% relative to conditions without 1,1,1-TCA. 1,1,1-TCA also inhibited reductive dehalogenases involved in TCE and cDCE dechlorination. In contrast, 1,1-DCA had no pronounced inhibitory effects on chlorinated ethene reductive dehalogenases, indicating that removal of 1,1,1-TCA via reductive dechlorination to 1,1-DCA is a viable strategy to relieve inhibition. 相似文献
In this article, we propose practical rules for tuning event-based PID controllers with two sampling strategies: symmetric send-on-delta (SSOD) and regular quantification (RQ). We present a detailed analysis about the effect of the derivative term of the controller when using SSOD or RQ and some guide lines are given to select the derivative filter coefficient. The two sampling strategies are compared, showing that, even when both of them lead to similar controlled output response, systems with RQ have better robustness properties than those with SSOD. The study is based on the describing function and the results are applicable to process with dynamic responses of different types: with time delays, non-minimum phase, under-damped response, etc. The rules presented here are given in terms of phase and gain margins that are measures of robustness used in the design of continuous PID controllers. This allows the application of conventional PID tuning methods to the case of event-based PID. The tuning rules are very simple and can be used for tuning PID, PI, PD and other controller structures. 相似文献
The shells of walnuts (WS) are major refuse in the global fruits and nuts trade. This, otherwise discarded, lignin-rich material can be carbonized to biochar—a value-added product with environmental applications such as carbon sequestration, soil amelioration, and pollutant adsorption. These applications are dictated by structural and chemical characteristics of the biochar carbon. Conventional controlled pyrolysis (CPy) of biomass is cost-intensive and technically too complex for widespread adoption, especially in emerging economies. Here, walnut shell biochar (BWS0) is derived through uncontrolled pyrolysis (UCPy) in a pyrolysis oven and further hybridized as magnetic biochar through ex-situ chemical co-precipitation. The physico-chemical characteristics of biochar and its water-extractable fractions are comprehensively investigated to understand their carbon structure and environmental applicability. The sp2 amorphous carbon sequestered in BWS0 is 0.84 kgCO2/kgbiomass with a BET (N2) surface area of 292 m2/g and is comparable to biochar from CPy in terms of carbon structure. The polyaromatic hydrocarbons present are only trace amounts of naphthalene, biphenyl, and phenanthrene. The magnetization decreases porosity of BWS0 while greatly facilitating its separation from aqueous media. BWS0 is suitable for adsorption of cations (between pH 2.8 and 9.45) and hydrophobic pollutants with only 19 mg L−1 fouling from their intrinsic dissolved organic carbon. In combination with fast-release N, P fertilizers, BWS0 (C/N of 24.8) is suitable for application in hydrophilic soils at higher loading rates. The results suggest an avenue where WS biochar can also be prepared via UCPy for direct environmental applications. Future investigations into soil incubation and adsorption tests are recommended.
Because of the current water crisis worldwide, it is of great importance to find alternative sources of drinking water, such as sulfur water. This review analyses laboratory, pilot and industrial-scale technologies available for sulfate removal from water produced for human consumption, from naturally occurring sulfur water and that resulting from human activities. Most of them exceed 90% removal efficiencies. However, the concentrations treated in each study were different; some technologies evaluate concentrations below recommended limits (250 mg L−1), while others evaluate much higher concentrations but require previous treatments. The technologies with higher energy requirements such as reverse osmosis and ion exchange have better removal efficiencies but require larger initial investments and have higher operational costs. Biological treatments, on the other hand, with lower energy and material requirements, are less expensive but require long retention times and depend on the season of the year and/or environmental conditions. Lastly, adsorption removal technologies fall in the middle, especially for energy requirements and operational costs and retention times. This review shows that although there are a variety of sulfate removal technologies suitable for use, there is still room for a novel methodology that removes sulfates from a wider range of concentrations more economically, more effectively and in less time than what is currently available. 相似文献
This work presents a reference conditioning anti-windup scheme based on passivity control theory. The main closed-loop is controlled by a proportional–integral–derivative (PID) control, and the injection and damping assignment technique ensures that PID variables are compatible with the process input. In the proposed algorithm, a fictitious actuator, modeled as a first-order filter, is incorporated to estimate the rate of change and the output of the actuator device. Amplitude and rate constraints are weight by coefficients that shape the energy function of the anti-windup scheme. Finally, to show how the algorithm can cope with the windup problem, simulation results are presented. Even when shown the results on a linear PID, the proposal can extend to any linear or nonlinear control in the main control loop. 相似文献
Pattern Analysis and Applications - Most commonly, stability analyses are performed using an external validation measure. For example, the Jaccard index is one of the indexes of choice for... 相似文献
Despite enormous progress and improvement in photocatalytic CO2 reduction reaction (CO2RR), the development of photocatalysts that suppress H2 evolution reaction (HER), during CO2RR, remains still a challenge. Here, new insight is presented for controllable CO2RR selectivity by tuning the architecture of the photocatalyst. Au/carbon nitride with planar structure (p Au/CN) showed high activity for HER with 87% selectivity. In contrast, the same composition with a yolk@shell structure (Y@S Au@CN) exhibited high selectivity of carbon products by suppressing the HER to 26% under visible light irradiation. Further improvement for CO2RR activity was achieved by a surface decoration of the yolk@shell structure with Au25(PET)18 clusters as favorable electron acceptors, resulting in longer charge separation in Au@CN/Auc Y@S structure. Finally, by covering the structure with graphene layers, the designed catalyst maintained high photostability during light illumination and showed high photocatalytic efficiency. The optimized Au@CN/Auc/G Y@S structure displays high photocatalytic CO2RR selectivity of 88%, where the CO and CH4 generations during 8 h are 494 and 198 µmol/gcat., respectively. This approach combining architecture engineering and composition modification provides a new strategy with improved activity and controllable selectivity toward targeting applications in energy conversion catalysis. 相似文献