Gaussian Mixture Cardinalized Probability Hypothesis Density(GM-CPHD): A Distributed Filter Based on the Intersection of Parallel Inverse Covariances.

A distributed GM-CPHD filter based on parallel inverse covariance crossover is designed to attenuate the local filtering and uncertain time-varying noise affecting the accuracy of sensor signals. First, the GM-CPHD filter is identified as the module for subsystem filtering and estimation due to its high stability under Gaussian distribution. Second, the signals of each subsystem are fused by invoking the inverse covariance cross-fusion algorithm, and the convex optimization problem with high-dimensional weight coefficients is solved. At the same time, the algorithm reduces the burden of data computation, and data fusion time is saved. Finally, the GM-CPHD filter is added to the conventional ICI structure, and the generalization capability of the parallel inverse covariance intersection Gaussian mixture cardinalized probability hypothesis density (PICI-GM-CPHD) algorithm reduces the nonlinear complexity of the system. An experiment on the stability of Gaussian fusion models is organized and linear and nonlinear signals are compared by simulating the metrics of different algorithms, and the results show that the improved algorithm has a smaller metric OSPA error than other mainstream algorithms. Compared with other algorithms, the improved algorithm improves the signal processing accuracy and reduces the running time. The improved algorithm is practical and advanced in terms of multisensor data processing.

Effects of long-term nitrogen addition on dissolved organic matter characteristics in a temperate wetland of Northeast China.

Dissolved organic matter (DOM) plays an indispensable role in ecosystem services and functions in wetlands. While most wetlands have undergone increased nitrogen (N) loading due to intensive human activities, the response of DOM characteristics to long-term N addition remains unexplored. In this study, we assessed the changes in dissolved organic carbon (DOC), NH4+, NO3-, dissolved organic N (DON), dissolved total N (DTN), and dissolved total phosphorus (DTP) in surface water and soil pore water at 15 cm depth after 10 years of N addition at four levels (0, 60, 120, and 240 kg N hm-2 year-1) in a freshwater marsh of Northeast China. We also examined the effect of N addition on DOM aromaticity and humification by measuring the specific UV absorbance at 254 nm (SUVA254), the color per C unit (C/C ratio), and the fulvic acid/humic acid ratio (E4/E6 ratio). Our results showed that N addition significantly altered DOM properties, but the direction and magnitude of these changes generally did not vary with the N addition level. During the growing season, DOC, NH4+, NO3-, DON, and DTN concentrations in both surface water and soil pore water were increased by N addition. Accordingly, N addition increased the DOC/DTP and DTN/DTP ratios but decreased the DOC/DTN ratio in surface water and soil pore water. In addition, the SUVA254 value and C/C ratio increased, while the E4/E6 ratio reduced after N addition in surface water and soil pore water, indicating increases in DOM aromaticity and humification. These observations suggest that long-term N addition changes DOM characteristics by causing stoichiometric imbalances and increasing recalcitrant compounds in temperate freshwater wetlands, which may then deteriorate water quality, alter microbial-mediated ecological processes, and impact downstream aquatic ecosystem structures.

The short-term and long-term effects of Fe(II) on the performance of anammox granules.

Fe(II) is one of the commonly used additives in wastewater treatment and proved to be beneficial for promoting microbial activity. In this study, the effects of Fe(II) on the specific anammox activity (SAA) and reactor performance were proved to be concentration-dependent. In the short-term experiment, low concentration of Fe(II) (5-80 mg/L) significantly enhanced the SAA, while high concentration of Fe(II) (120-300 mg/L) inhibited the SAA. It was confirmed that anammox can be domesticated after long-term exposure to low Fe(II) concentration, and the SAA could be further enhanced by higher Fe(II) concentration in the following phases. In addition, as an important factor for anammox granulation and maintaining the SAA, the extracellular polymeric substance (EPS) was also affected by Fe(II) addition. In spite of the effects on SAA and EPS, Fe(II) was proved to be the key factor that enhances the N2 O emission via abiotic pathway in the anammox reactor. PRACTITIONER POINTS: Low Fe(II) concentrations enhanced SAA, while high concentrations inhibited SAA. Long-term acclimatization by Fe(II) improved the tolerance of anammox to Fe(II). Fe(II) affects the amount and constituent of EPS and the performance of anammox granules. Accumulation of Fe(II) in the AAFEB reactor promoted the N2 O emission.

Systematic approach to evaluating environmental and ecological technologies for wastewater treatment.

Evaluating the performance of wastewater treatment represents a challenging and complex task as it usually involves engineering, environmental and economic (3E) factors. In this study, we developed an 3E triangle model to evaluate the performance of environmental technologies (i.e., anaerobic-anoxic-oxic reactors, oxidation ditches, and membrane bioreactors) and ecological technologies (i.e., stabilization ponds, constructed wetlands, and slow-rate systems) for wastewater treatment. A total of 17 key performance indicators, such as energy consumption, pollutant removal, global warming potential and wastewater treatment fees, were considered in the 3E triangle model. The results indicated that, in terms of engineering performance, both the membrane bioreactors and constructed wetlands were stable, effective and reliable during their operating periods. When the environmental impacts of wastewater treatment technologies were compared via a life cycle assessment, the ecological technologies showed superior performance, in terms of environmental impacts, especially for the global warming potential and eutrophication potential. In general, environmental technologies exhibited higher treatment fees and unit construction costs because of their large power consumption and equipment costs. In contrast, ecological technologies had higher unit land use due to their large area requirements and low treatment capacity. In overall, both the membrane bioreactors and constructed wetlands showed excellent overall performance in the 3E triangle model. Wastewater treatment plant are typical case studies for addressing the interactions of water and energy elements. Reducing energy consumption is a hotspot for the research field of membrane bioreactors, while constructed wetlands are continually improved and optimized to have broad applications for rural wastewater treatment.