In anaerobic digestion, the production of short-chain fatty acids (SCFAs) can be beneficial or harmful to the overall process, depending on the concentration of accumulated acids. Therefore, the accurate determination of the SCFA concentration in both fresh and stored sludge hydrolysates is important. To select a suitable method for monitoring SCFAs during the anaerobic digestion of sewage sludge, the accuracy of three available analytical methods, including 5 pH point acid titration (TITRA5), gas chromatography (GC), and spectrophotometry, were compared in the present study. The results revealed that TITRA5 and GC displayed better agreement in the achieved measurements and higher precision and accuracy than the spectrophotometric assay, as supported by the application of different statistical models. TITRA5 excelled in titrating unfiltered hydrolysate while simultaneously measuring the alkalinity, whereas the GC method provided detailed information on the contribution of different fatty acids to the total acidity. In contrast, the spectrophotometric assay suffered from many forms of interference, depending on the sample's matrix. SCFA production followed the pattern of enzymatic reactions and fitted the Michaelis-Menten model. In addition to promoting TITRA5 as an accurate and robust analytical tool for routine SCFA analyses, this comparative study also demonstrated the possibility of storing hydrolysate samples at different temperatures and durations without altering the SCFA measurements. 相似文献
长江经济带发展是我国重要国家战略,但面临着水环境保护难度大、污染来源不清和措施集成度低等问题.针对流域尺度多源污染协同治理面临的方法瓶颈,结合资料调研分析、机制模型模拟和智能算法优化,构建了"污染精准溯源-措施效果评价-措施整体优化"为主体的流域水环境保护框架,并以安徽省铜陵市顺安河流域为例进行了方案应用.结果表明,新框架可精准量化流域内种植业、农村生活、畜禽养殖、水产养殖、工业废水和生活污水的贡献,并评价多种防控措施及其集成的总体效果;多目标优化蛙跳算法通过系统对比多种方案的成本效益,提供了性价比高的流域多源污染协同治理方案,如通过合理投资可使顺安河流域总氮在丰、平和枯水年分别削减1274.24、855.24和381.96 t ·a-1,总磷削减321.42、159.80和42.93 t ·a-1,保障水质达到地表Ⅲ类水质标准.新框架可推广到其他流域,为流域高质量发展背景下的水环境保护提供模式参考. 相似文献
Richards, R. Peter, Ibrahim Alameddine, J. David Allan, David B. Baker, Nathan S. Bosch, Remegio Confesor, Joseph V. DePinto, David M. Dolan, Jeffrey M. Reutter, and Donald Scavia, 2012. Discussion –“Nutrient Inputs to the Laurentian Great Lakes by Source and Watershed Estimated Using SPARROW Watershed Models” by Dale M. Robertson and David A. Saad. Journal of the American Water Resources Association (JAWRA) 1‐10. DOI: 10.1111/jawr.12006 Abstract: Results from the Upper Midwest Major River Basin (MRB3) SPARROW model and underlying Fluxmaster load estimates were compared with detailed data available in the Lake Erie and Ohio River watersheds. Fluxmaster and SPARROW estimates of tributary loads tend to be biased low for total phosphorus and high for total nitrogen. These and other limitations of the application led to an overestimation of the relative contribution of point sources vs. nonpoint sources of phosphorus to eutrophication conditions in Lake Erie, when compared with direct estimates for data‐rich Ohio tributaries. These limitations include the use of a decade‐old reference point (2002), lack of modeling of dissolved phosphorus, lack of inclusion of inputs from the Canadian Lake Erie watersheds and from Lake Huron, and the choice to summarize results for the entire United States Lake Erie watershed, as opposed to the key Western and Central Basin watersheds that drive Lake Erie’s eutrophication processes. Although the MRB3 SPARROW model helps to meet a critical need by modeling unmonitored watersheds and ranking rivers by their estimated relative contributions, we recommend caution in use of the MRB3 SPARRROW model for Lake Erie management, and argue that the management of agricultural nonpoint sources should continue to be the primary focus for the Western and Central Basins of Lake Erie. 相似文献
This study designs and applies a new energy-conservation type solar-powered lighting system using a high-pressure sodium lamp to areas not having any utility company's electricity. The proposed system uses a zero-voltage-switching (ZVS) DC/DC converter in the batteries’ charge circuit to reduce the switching loss for a higher charging efficiency. Said system also adopts the maximum power point tracking (MPPT) technique to maximize the solar panels’ photovoltaic conversion capability. When dark, the batteries in the proposed system will discharge, with a raised voltage, through a push-pull DC/DC converter; said voltage, as the input voltage of the series-parallel resonant inverter, will be regulated to dim the lamp. To enable the efficient usage of the batteries’ stored energy capacity, this control scheme of the proposed system may adjust the night-time discharge time lengths, according to season difference, and compute the usable capacity for the load, according to the batteries’ charged voltage, so as to select a suitable pre-scheduled light-dimming curve for the lamp to achieve energy conservation for the batteries and continuity in lighting when dark. 相似文献
Objective: This study aimed at identifying and predicting in advance the point in time with a high risk of a virtual accident before a virtual accident actually occurs using the change of behavioral measures and subjective rating on drowsiness over time and the trend analysis of each behavioral measure.
Methods: Behavioral measures such as neck bending angle and tracking error in steering maneuvering during the simulated driving task were recorded under the low arousal condition of all participants who stayed up all night without sleeping. The trend analysis of each evaluation measure was conducted using a single regression model where time and each measure of drowsiness corresponded to an independent variable and a dependent variable, respectively. Applying the trend analysis technique to the experimental data, we proposed a method to predict in advance the point in time with a high risk of a virtual accident (in a real-world driving environment, this corresponds to a crash) before the point in time when the participant would have encountered a crucial accident if he or she continued driving a vehicle (we call this the point in time of a virtual accident).
Results: On the basis of applying the proposed trend analysis method to behavioral measures, we found that the proposed approach could predict in advance the point in time with a high risk of a virtual accident before the point in time of a virtual accident.
Conclusion: The proposed method is a promising technique for predicting in advance the time zone with potentially high risk (probability) of being involved in an accident due to drowsy driving and for warning drivers of such a drowsy and risky state. 相似文献