脉冲电源电凝聚处理厨房废水的研究

将脉冲电源和直流电源分别作为电凝聚处理废水的外加电源,拟试验探明电源对电凝聚处理废水的电能消耗的影响和相关参数的优化.试验结果表明,脉冲电源相对直流电源能更加有效降低阳极的超电位,减缓电极的极化,从而降低槽电压,进而有效地降低电能消耗.在试验条件下,脉冲频率对处理效果影响不显著,而脉冲占空比对处理效果有明显的影响,较合适的脉冲电源电凝聚处理废水的优化参数是:脉冲频率1 000 Hz、占空比60%.同时,对电解槽沉积絮凝物的处理进行了说明.     

双循环两相生物处理工艺的中试研究

采用双循环两相生物处理工艺(BICT)系统对城市污水处理厂出水进行中试研究,探讨了中试试验工况下BICT系统对污染物的去除率.结果表明,独立膜反应区的设置消除了生物硝化与除磷的关联性,从而可通过在SBR反应器缩短泥龄来提高系统的除磷效率;系统中污泥转移的实现,使系统在反应阶段能保证较高的污泥浓度,从而提高污泥的释磷效果,为系统处理能力的提升提供较大潜力.在适宜的试验工况下,进水COD容积负荷小于1.00 kg/(m3·d)时,系统COD平均去除率80%左右,出水COD保持在60 mg/L左右;总氮容积负荷小于0.4 kg/(m3·d)时,总氮平均去除率在80%左右,出水总氮低于15 mg/L;总磷容积负荷3～35 g/(m3·d)时,总磷去除率稳定在90%以上,出水总磷低于0.5 mg/L;出水指标均可达到<城镇污水处理厂污染物排放标准>(GB 18918-2002)中的一级标准.     

Study on dissolved organic carbon in precipitation in Northern China

Dissolved organic carbon (DOC) was measured in 483 precipitation samples collected at 10 sites in Northern China from December 2007 to November 2008. The annual volume-weighted mean (VWM) concentrations and wet deposition fluxes of DOC for 10 sites ranged from 2.4 to 3.9 mg C/L and 1.4 to 2.7 g C m^?2 yr^?1, respectively. The proportion of DOC to total organic carbon (TOC) was 79% on average, suggesting that a significant fraction of TOC was present as insoluble particulate organic carbon. Due to intensive domestic coal use for house heating and smaller dilution of scavenged organic carbon, higher VWM concentrations of DOC were observed during winter and spring than during summer and autumn. When precipitation events were classified via air mass back-trajectories, the mixed trajectories from SE and NW always corresponded to significantly higher DOC than those from SE or NW alone, coinciding with the centre of a low pressure system moved eastward and the wind direction changed from southeast to northwest. The results also showed that each site had a similar seasonal variation for DOC wet deposition flux. The largest flux occurred during the rainy season, and the lowest flux appeared during winter months. The product of the TC/DOC ratio and the DOC flux yielded an average TC wet deposition flux of 3.2 g C m^?2 yr^?1 in Northern China, accounting for 8.6% and 22% of the carbon sink magnitude (37 g C m^?2 yr^?1) in terrestrial ecosystems and anthropogenic carbon emissions (14 g C m^?2 yr^?1), respectively. This indicates that atmospheric wet deposition of TC is a significant carbon flux that cannot be neglected in regional models of the carbon cycle, and should be considered along with dry deposition in the removal mechanism for carbon from regional atmosphere.     

Industrial-scale application of the plunger flow electro-oxidation reactor in wastewater depth treatment

Environmental Science and Pollution Research - Effluents after biochemical treatment contain pollutants that are mostly non-degradable. Based upon previous pilot-scale test results, an...     

Effects of high ammonium level on biomass accumulation of common duckweed Lemna minor L.

Growing common duckweed Lemna minor L. in diluted livestock wastewater is an alternative option for pollutants removal and consequently the accumulated duckweed biomass can be used for bioenergy production. However, the biomass accumulation can be inhibited by high level of ammonium (NH₄ ⁺) in non-diluted livestock wastewater and the mechanism of ammonium inhibition is not fully understood. In this study, the effect of high concentration of NH₄ ⁺ on L. minor biomass accumulation was investigated using NH₄ ⁺ as sole source of nitrogen (N). NH₄ ⁺-induced toxicity symptoms were observed when L. minor was exposed to high concentrations of ammonium nitrogen (NH₄ ⁺-N) after a 7-day cultivation. L. minor exposed to the NH₄ ⁺-N concentration of 840 mg l^?1 exhibited reduced relative growth rate, contents of carbon (C) and photosynthetic pigments, and C/N ratio. Ammonium irons were inhibitory to the synthesis of photosynthetic pigments and caused C/N imbalance in L. minor. These symptoms could further cause premature senescence of the fronds, and restrain their reproduction, growth and biomass accumulation. L. minor could grow at NH₄ ⁺-N concentrations of 7–84 mg l^?1 and the optimal NH₄ ⁺-N concentration was 28 mg l^?1.     

Sensitivity analysis of source regions to PM2.5 concentration at Fukue Island,Japan

The authors analyze the sensitivities of source regions in East Asia to PM_2.5 (particulate matter with an aerodynamic diameter of ≤2.5 µm) concentration at Fukue Island located in the western part of Japan by using a regional chemical transport model with emission sensitivity simulations for the year 2010. The temporal variations in PM_2.5 concentration are generally reproduced, but the absolute concentration is underestimated by the model. Chemical composition of PM_2.5 in the model is compared with filter sampling data in spring; simulated sulfate, ammonium, and elemental carbon are consistent with observations, but mass concentration of particulate organic matters is underestimated. The relative contribution from each source region shows the seasonal variation, especially in summer. The contribution from central north China (105°E–124°E, 34°N–42°N) accounts for 50–60% of PM_2.5 at Fukue Island except in summer; it significantly decreases in summer (18%). Central south China (105°E–123°E, 26°N–34°N) has the relative contribution of 15–30%. The contribution from the Korean Peninsula is estimated at about 10% except in summer. The domestic contribution accounts for about 7% in spring and autumn and increases to 19% in summer. We also estimate the relative contribution to daily average concentration in high PM_2.5 days (>35 μg m^?3). Central north China has a significant contribution of 60–70% except in summer. The relative contribution from central south China is estimated at 46% in summer and about 30% in the other seasons. The contributions from central north and south China on high PM_2.5 days are generally larger than those of their seasonal mean contributions. The domestic contribution is smaller than the seasonal mean value in every season; it is less than 10% even in summer. These model results suggest that foreign anthropogenic sources have a substantial impact on attainment of the atmospheric environmental standard of Japan at Fukue Island.

Implications: The contribution from several source regions in East Asia to PM_2.5 concentration at Fukue Island, a remote island located in the western part of Japan and close to the Asian continent, is estimated using a three-dimensional chemical transport model. The model results suggest that PM_2.5 that is attributed to foreign anthropogenic sources have a larger contribution than that of domestic pollution and have a substantial impact on attainment of the atmospheric environmental standard of Japan at Fukue Island.     

Inhibition of thrombin by functionalized C60 nanoparticles revealed via in vitro assays and in silico studies

The studies on the human toxicity of nanoparticles (NPs) are far behind the rapid development of engineered functionalized NPs. Fullerene has been widely used as drug carrier skeleton due to its reported low risk. However, different from other kinds of NPs, fullerene-based NPs (C₆₀ NPs) have been found to have an anticoagulation effect, although the potential target is still unknown. In the study, both experimental and computational methods were adopted to gain mechanistic insight into the modulation of thrombin activity by nine kinds of C₆₀ NPs with diverse surface chemistry properties. In vitro enzyme activity assays showed that all tested surface-modified C₆₀ NPs exhibited thrombin inhibition ability. Kinetic studies coupled with competitive testing using 3 known inhibitors indicated that six of the C₆₀ NPs, of greater hydrophobicity and hydrogen bond (HB) donor acidity or acceptor basicity, acted as competitive inhibitors of thrombin by directly interacting with the active site of thrombin. A simple quantitative nanostructure-activity relationship model relating the surface substituent properties to the inhibition potential was then established for the six competitive inhibitors. Molecular docking analysis revealed that the intermolecular HB interactions were important for the specific binding of C₆₀ NPs to the active site canyon, while the additional stability provided by the surface groups through van der Waals interaction also play a key role in the thrombin binding affinity of the NPs. Our results suggest that thrombin is a possible target of the surface-functionalized C₆₀ NPs relevant to their anticoagulation effect.     

Estimating Root Zone Soil Moisture at Continental Scale Using Neural Networks

This study investigates the feasibility of artificial neural networks (ANNs) to retrieve root zone soil moisture (RZSM) at the depths of 20 cm (SM20) and 50 cm (SM50) at a continental scale, using surface information. To train the ANNs to capture interactions between land surface and various climatic patterns, data of 557 stations over the continental United States were collected. A sensitivity analysis revealed that the ANNs were able to identify input variables that directly affect the water and energy balance in root zone. The data important for RZSM retrieval in a large area included soil texture, surface soil moisture, and the cumulative values of air temperature, surface soil temperature, rainfall, and snowfall. The results showed that the ANNs had high skill in retrieving SM20 with a correlation coefficient above 0.7 in most cases, but were less effective at estimating SM50. The comparison of the ANNs showed that using soil texture data improved the model performance, especially for the estimation of SM50. It was demonstrated that the ANNs had high flexibility for applications in different climatic regions. The method was used to generate RZSM in North America using Soil Moisture and Ocean Salinity (SMOS) soil moisture data, and achieved a spatial soil moisture pattern comparable to that of Global Land Data Assimilation System Noah model with comparable performance to the SMOS surface soil moisture retrievals. The models can be efficient alternatives to assimilate remote sensing soil moisture data for shallow RZSM retrieval.     

臭气强度在恶臭污染物环境空气影响中的应用研究

以兰州某石化公司化工污水处理厂恶臭治理项目为例,在确定恶臭气体的污染源源强的基础上,采用AERMOD模式预测污染物扩散情况。结果表明,添置除臭装置后,NH3的臭气浓度减少了90%,VOCs的臭气浓度减少了88%。同时,当恶臭污染物浓度达到环境质量浓度标准时,NH3的臭气强度为1．40级,VOCs的臭气强度为0．82级,人们仍能感觉到气味。因此石化企业在进行恶臭治理过程中需综合考虑污染物的环境空气质量浓度标准和臭气强度,以期改善环境空气质量。