Further study on particle size, stability, and complexation of silver nanoparticles under the composite effect of bovine serum protein and humic acid.

Silver nanoparticles (AgNPs) are widely used due to their unique antibacterial properties and excellent photoelectric properties. Wastewater treatment plants form a pool of AgNPs due to the social cycle of wastewater. During biological treatment processes, the particle size and stability of AgNPs change. We studied the particle size changes and stability of silver nanoparticles in the presence of bovine serum albumin (BSA) and humic acid (HA). The experimental results indicated that silver nanoparticles can complex with the functional groups in BSA. For AgNP-BSA composites, as the BSA concentration increases, the size of the silver nanoparticles first decreases and then increases. AgNPs can combine with the amide, amino, and carboxyl groups in HA. As the concentration of HA increases, the particle size and large particle size distribution of AgNPs increase. This increasing trend is more obvious when the HA concentration is lower than 20 mg L-1. When HA and BSA exist at the same time, HA will occupy the adsorption sites of BSA on the surface of AgNPs, and the AgNP-HA complex will dominate the system. This study aims to provide key operational control strategies for the process operation of wastewater treatment plants containing AgNPs and theoretical support for promoting water environment improvement and economic development such as tourism.

Modeling the Operating Performance of a Drinking Water Biological Aerated Filter and the Formation of Organic Nitrogen.

In this study, simultaneous storage and growth mechanism, as well as the formation processes of organic nitrogen (ON), were both introduced into activated sludge model 3 (ASM3), and ASM3-ON was formed to predict the operation of biofilm treatment processes and the formation of dissolved organic nitrogen (DON). ASM3-ON was applied to a lab-scale biological aerated filter (BAF) for water supply. During the simulation, the sensitivities of chemical oxygen demand (COD), ammonia nitrogen (NH4+-N), nitrate nitrogen (NOx--N), and DON to the stoichiometric and kinetic coefficients in the model were analyzed first by the Sobol method. Then, the model prediction results were compared with experimental values to calibrate ASM3-ON. In the validation process, ASM3-ON was applied to predict the variations of COD, NH4+-N, NO2--N, and NO3--N in BAF under different aeration ratios (0, 0.5:1, 2:1, and 10:1) and different filtration velocities (0.5, 2, and 4 m/h). The comparison with the experimental results showed that ASM3-ON could accurately predict the variation characteristics of COD, NH4+-N, NOx--N, and DON in BAF. This study provided a practical model approach to optimize the operating performance of BAF and reduce the formation of ON through nonexperimental methods.

Spectral characterization of the effect of gas-water ratio on dissolved organic nitrogen variation along a drinking water biological aerated filter.

To improve the understanding of dissolved organic nitrogen (DON) variation characteristics in a biological aerated filter (BAF) used for drinking water treatment, this study investigated the effects of gas-water ratios (0, 0.5:1, 2:1, and 10:1), a controlling factor of BAF operation, on DON characteristics. The dissolved organic carbon (DOC) removal efficiency in the BAF was consistent with DON concentration and increased as the gas-water ratio increased to a certain point, above which the increase gradually decreased. The optimal gas-water ratio in this study was considered to be 2:1 from the perspective of DOC removal and DON reduction. Use of fluorescence regional integration (FRI) and parallel factor (PARAFAC) model to analyze the effects of the gas-water ratio on the spectral characteristics of DON revealed that humic acid-like substances were not sensitive to the gas-water ratio, while protein-like substances were more sensitive. Increasing the gas-water ratio was beneficial to the reduction of biodegradable DON. Correlation analysis showed that the results obtained using FRI were consistent with those obtained using the PARAFAC model under different gas-water ratios.

[Improvement of "scatter degree" method and its application in evaluating river ecosystem health].

"Scatter degree" method is generally blamed for not capable of reflecting the subjective information of evaluator in comprehensive evaluation and for the complexity, uncertainty, and variety of the factors affecting river ecosystem health. In this paper, the "scatter degree" method was improved and applied to comprehensively evaluate the ecosystem health status of the upstream, midstream, and downstream of Beiyunhe River which flowed through Beijing and Tianjing. The ecosystem health value of upstream, midstream, and downstream was evaluated as 0.539, 0.521 and 0. 546, respectively, indicating that these streams were in sub-health condition. The environmental status of flowing water was the most important factor affecting the River' s ecosystem health. With the application of the improved method to evaluate river ecosystem health, both the evaluator' s subjective judgment and the data's objective information could be included, the evaluation process was transparent, and the evaluation results were scientific, reasonable, objective, and reliable, suggesting that this method could be served as a technical support and a basis for the comprehensive treatment of rivers.