The scale-free network behavior of ambient volatile organic compounds

A scale-free network model with surface and vertical field measurements was used to identify the connectivity distribution of the scale-free network behavior of ambient volatile organic compounds (VOCs). The results show that the carbon number (C _n ) with the total amount of C _n compounds (P(C _n )) possesses an explicit relationship with the scale-free network behavior. The proportionate coefficient (α) and exponent ( γ) of the scale-free network model with spatial and temporal variations are estimated and discussed. The analytical results demonstrate that although photochemical reactions cause the VOCs fraction variation, they do not alter the fraction of C _n compounds observably. Therefore, the values of α and of γ did not vary with time, but with local regional characteristics. The results indicate that the influence of local VOCs emissions occurs at a height of 100 m, but becomes insufficient at a height of 300 m. Air mass mixing increases with greater height; thus, the influence of regional characteristics at a height of 700 m is low. Finally, a successful empirical model was established to evaluate the distribution of surface VOCs in various regions.     

Correlation analysis of major control factors for the formation and stabilization of aerobic granule

In recent years, aerobic granular sludge technology has demonstrated significant advantages in areas such as the sludge–water separation, residual sludge minimization, simultaneous biological nitrogen and phosphorus removal, and toxic organic compounds degradation in biological wastewater treatment. However, the critical control factors and their relation during sludge granulation have not been revealed indeed, and the stability of aerobic granular sludge is still not good. The Gray’s correlation analysis was used to investigate the relationship of aerobic granular characteristics and control factors in the study. Results showed that the organic loading rate, hydraulic shear stress, and sludge settling time were the major factors affecting the aerobic sludge granulation, and the associated regulating strategy was important for the stabilization of granular sludge system. Based on above results, the mechanism of aerobic sludge granulation was proposed, and it was expected to favor the application of aerobic granular sludge technology.     

Characterizing the interactions between polycyclic aromatic hydrocarbons and fulvic acids in water

Polycyclic aromatic hydrocarbons (PAHs) are persistent, bioaccumulative, and toxic chemicals and are listed as priority pollutants by the US EPA. Although they are sparsely soluble in water, their solubility can be increased by binding to dissolved organic matter in natural waters, which will further increase their environmental risk as toxic pollutants. In this study, the interaction between PAHs, exemplified by fluorene and anthracene, and fulvic acid (FA) was studied using fluorescence quenching titration method with fluorescence emission spectra, respectively. The association of FA with the mixture of fluorene and anthracene was also evaluated by excitation–emission matrix (EEM) fluorescence spectrometry combined with parallel factor (PARAFAC) analysis. Results demonstrate that EEM fluorescence spectrometry with PARAFAC analysis was sensitive and reliable to determine the binding properties of PAHs with FA in a mixed aqueous solution. The conditional stability constants and binding capacities show that both PAHs bind to FA tightly.     

基于密相半干法脱硫工艺的生石灰消化及改性

以某公司生产的生石灰作为脱硫剂,密相半干法脱硫工艺在某炼铁厂烧结烟气脱硫工程的应用为例,对生石灰的消化反应和调质改性进行实验,考察其满足脱硫要求的最佳消化条件和烧结机头灰作为改性剂的比重。实验表明,当水灰比在1.5～1.7、生石灰粒径在200μm以下、消化温度在55℃左右、搅拌轴转速在15～25 r/min的范围内,可以保证生石灰有最佳的转化率,烧结机头灰占比重的5%时为最佳改性剂量;同时对实验的工程运行成本和脱硫效果进行分析,使用自制改性脱硫剂即可以节约运行成本和水电资源,又能提高脱硫效果,为脱硫设备的长期稳定运行提供了可靠依据。     

不同碳源添加量对垂直流人工湿地污水处理效果的影响

以垂直流人工湿地小试系统为研究对象,采用碱处理过的千屈菜(Lythrum salicaria)作为反硝化碳源补充材料,探讨了不同碳源添加量对系统COD及氮、磷去除效果的影响。结果表明,一定剂量经过碱处理的千屈菜材料可以为人工湿地系统脱氮提供反硝化所需要的碳源,而且具有缓效持续释放的特点。添加此碳源材料可明显提高系统的脱氮效率,最高可提升30.85%,但随着C/N比的增加,硝态氮去除率逐渐降低,C/N比为3、5、8时分别为91.20%、87.72%和84.19%。添加碳源量达到C/N比为3时系统能够发生最大程度反硝化,此时不仅人工湿地系统脱氮效果得到提高,同时人工湿地除磷能力也有所增强。碱处理过的千屈菜材料在本系统中的最适宜添加量为5 g,即100 g/m2(C/N=3),远低于在进水中为满足反硝化所需调控的C/N比(5～8),可以节约外加碳源成本。     

菲污染土壤黑麦草/苜蓿间作修复效应

多环芳烃类化合物(PAHs)是环境中普遍存在的持久性有毒有机污染物,因具有强烈的"三致"作用,业已引起各国环境科学工作者的广泛关注,PAHs污染土壤的修复也已成为环境科学与工程领域的研究热点。以菲为PAHs的代表,研究了黑麦草/苜蓿间作对多环芳烃(菲)污染土壤的修复效应。通过温室盆栽模拟实验,观察到5 mg/kg和50 mg/kg污染水平没有明显抑制黑麦草和苜蓿的生长;黑麦草/苜蓿间作促进了植物对土壤菲的吸收,且间作体系根系富集系数大于单作;土壤中菲的可提取浓度随时间的延长逐渐减少,在菲重度污染土壤上,黑麦草/苜蓿间作修复效果明显优于单作,菲去除率可高达90.53%。因此,对于重度PAHs污染土壤该体系是一种有实际应用价值的间作修复体系。     

罐底含油污泥萃取溶剂的选择与优化

针对某炼化企业在石油储运过程中产生的罐底油泥,进行了油泥样分析和不同萃取剂萃取回收油分实验.经分析该罐底油泥含水率约16.1％,总有机物含量约34.8％,其中可萃取石油类物质约占总有机物成分的67.0％.考察不同溶剂的萃取效果,结果表明,石脑油90 ～ 110℃沸程段的馏分油的萃取效果和工艺可操作性优越于其他常用溶剂,其萃取效果排序为石脑油90～ 110℃沸程段的馏分油＞120#溶剂油＞正庚烷＞石油醚(90 ～ 120℃)＞石油醚(60 ～ 90℃);用石脑油90 ～ 110℃沸程段的馏分油在优化萃取工艺条件下,经两次萃取可分离出大于96％的可萃取油分,罐底油泥中有机物的萃出率可达64％以上,比120#溶剂油萃取效果高出约3％～5％,实现了罐底油泥更深程度的萃取和资源化利用.     

密相半干法低温同时脱硫脱硝影响因素

针对90~160℃的低温条件下,SO₂对钙基吸收剂吸收NO_x的影响进行了实验研究,分析了烟气温度T、含氧率、含湿量等对SO₂促进钙基吸收剂吸收NO_x的影响。实验结果表明,当烟气中SO₂浓度的升高可促进钙基吸收剂对NO_x的吸收;同时,维持反应系统在9.2%的含湿量;保证烟气温度在结露点以上,使系统在90~100℃的温度区间;控制系统漏风率,防止含氧率的升高;保证前端电除尘效率的同时,将一部分电除尘捕集到的灰尘作为钙基脱硫剂的添加剂,并使之参与脱硫反应器内的钙基吸收剂循环过程中;可较多地脱除烟气中的污染物质。     

数学规划在水网络优化设计中的应用进展

综述了数学规划在连续过程水网络优化设计中的应用进展。分析了树搜索、线性规划、非线性规划、混合整数非线性规划、基于数学规划的复合方法等方法设计水网络的特点、求解策略及应用情况,探讨了模型求解的优化算法。