Partition of Volatile Organic Compounds in Activated Sludge and Wastewater

Abstract

The Henry’s law constant is important in the gas-liquid mass transfer process. Apparent dimensionless Henry’s law constant, or the gas-liquid partition coefficient (K’ _H), for both hydrophilic (methanol, isopropyl alcohol, and acetone) and hydrophobic (toluene and p-xylene) organic compounds in deionized (DI) water, a wastewater with a maximum total dissolved organic carbon (DOC) content of 700 mg/L, and DI water mixed with a maximum activated sludge suspended solid (SS) concentration of 40,000 mg/L were measured using the single equilibrium technique at 293 K.

Experimental results demonstrate that the K’ _H of any of the test volatile organic compounds varied among three situations. First, the K’_H of the hydrophilic compounds in mixed liquor with the maximum SS concentration was 9–21% higher than those in DI water. Second, those for toluene and p-xylene were 77% and 93% lower, respectively, in the mixed liquor with the maximum SS concentration. Third, the K’_H values of all of the test compounds in the wastewater were only 10% lower than those in DI water.

A model was developed to relate K’ _H with wastewater DOC and the SS concentration in the activated sludge using an organic carbon-water partition coefficient and activated sludge-water partition coefficient as model parameters. The model was verified and model parameters for test compounds estimated.     

Establishment of a comprehensive analysis method for the microfaunal movement in activated sludge

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Polycyclic aromatic hydrocarbon and n-alkane pollution characteristics and structural and functional perturbations to the microbial community: a case-study of historically petroleum-contaminated soil

Characterization of the typical petroleum pollutants, polycyclic aromatic hydrocarbons (PAHs) and n-alkanes, and indigenous microbial community structure and function in historically contaminated soil at petrol stations is critical. Five soil samples were collected from a petrol station in Beijing, China. The concentrations of 16 PAHs and 31 n-alkanes were measured by gas chromatography-mass spectrometry. The total concentrations of PAHs and n-alkanes ranged from 973 ± 55 to 2667 ± 183 μg/kg and 6.40 ± 0.38 to 8.65 ± 0.59 mg/kg (dry weight), respectively, which increased with depth. According to the observed molecular indices, PAHs and n-alkanes originated mostly from petroleum-related sources. The levels of ΣPAHs and the total toxic benzo[a]pyrene equivalent (ranging from 6.41 to 72.54 μg/kg) might exert adverse biological effects. Shotgun metagenomic sequencing was employed to investigate the indigenous microbial community structure and function. The results revealed that Proteobacteria and Actinobacteria were the most abundant phyla, and Nocardioides and Microbacterium were the important genera. Based on COG and KEGG annotations, the highly abundant functional classes were identified, and these functions were involved in allowing microorganisms to adapt to the pressure from contaminants. Five petroleum hydrocarbon degradation-related genes were annotated, revealing the distribution of degrading microorganisms. This work facilitates the understanding of the composition, source, and potential ecological impacts of residual PAHs and n-alkanes in historically contaminated soil.

     

Delayed association of acute particulate matter 2.5 air pollution exposure with loss of complexity in cardiac rhythm dynamics: insight from detrended fluctuation analysis

Environmental Science and Pollution Research - There is a delayed (lag 1 to 2 days) correlation between acute PM 2.5 (particulate matter <?2.5 μm in aerodynamic...     

Desorption of CO2, SO2, and NH3 in the vacuum evaporation of desulfurization wastewater

Environmental Science and Pollution Research - Mechanical vapor compression and multi-effect evaporation have been widely used in achieving zero discharge of desulfurization wastewater as they are...     

Sugarcane monoculture drives microbial community composition,activity and abundance of agricultural-related microorganisms

Environmental Science and Pollution Research - Sugarcane monoculture (SM) often leads to soil problems, like soil acidification, degradation, and soil-borne diseases, which ultimately pose a...     

天津冬季一次重污染过程颗粒物中水溶性离子粒径分布特征

为研究天津冬季重污染天气过程中颗粒物水溶性离子的粒径谱分布及二次离子生成机制,于2014年1月利用Anderson撞击式分级采样器在中国气象局天津大气边界层观测站内采集颗粒物样品,并使用离子色谱仪分析Na~+、NH_4~+、K~+、Mg~(2+)、Ca~(2+)、Cl~-、NO_3~-、SO_4~(2-)等8种水溶性无机离子(TWSII).结果表明,采样期间PM_(2.5)和PM_(10)质量浓度均值分别为(138±100)μg·m~(-3)和(227±142)μg·m~(-3),粗、细粒子中TWSII的平均浓度分别为(34.07±6.16)μg·m~(-3)和(104.16±51.76)μg·m~(-3).细粒子中SO_4~(2-)、NO_3~-和NH_4~+这3种离子的浓度远高于其他离子,且相关性较好,粗粒子中NO_3~-、SO_4~(2-)、Cl~-浓度较高.随着污染程度加剧,细粒子中TWSII浓度增加明显,粗粒子中则变化不大.水溶性离子的粒径谱分布显示,SO_4~(2-)以单模态分布,优良天峰值出现在0.43~0.65μm,NO_3~-在优良日呈现三模态分布,峰值分别出现在0.43~0.65、2.1~3.3和5.8~9.0μm,NH_4~+呈双模态分布,优良日峰值出现在0.43~0.65μm和4.7~5.8μm,污染日3种二次离子峰值均以0.65~1.1μm的单模态分布为主,与三者之间的热动力平衡过程有关.细粒子中NH_4~+除与SO_4~(2-)和NO_3~-结合外,还与部分Cl~-结合,粗粒子中NH_4~+全部与NO_3~-和SO_4~(2-)结合后,剩余的NO_3~-和SO_4~(2-)与其他阳离子结合.     

不同湿地模型中根系微生物的多样性

为了研究不同植物和滤料组合的小型湿地模型在处理养殖池塘水体过程中根系微生物群落的特征,并分析植物对根系微生物富集的影响,本研究对两种植物(茭白和慈菇)和两种滤料(石榴石和磁铁矿)进行组合构建了6种不同的湿地模型,并利用高通量测序技术分析湿地植物根系微生物的结构特点和多样性.结果表明:不同湿地模型根系微生物的种类和数量各不相同;所有收集的微生物总体上属于52个门,118个纲,455科,905个属和1 426个种;根据Shannon指数,茭白(平均为5.77)比慈菇(平均为5.29)在微生物富集方面具有更强的能力;但是,慈菇和茭白根系微生物中变形菌门的比例分别平均为61.97%和51.78%,说明慈菇能够更好地富集变形菌.β-变形菌纲为实验期间不同植物根际富集的主要细菌类群.本研究结果为人工湿地植物优化选择提供了理论基础和湿地组合最佳构建提供了基础资料.     

Simultaneous removal of Cu(II) and Cr(VI) by Mg–Al–Cl layered double hydroxide and mechanism insight

Mg–Al–Cl layered double hydroxide (Cl-LDH) was prepared to simultaneously remove Cu(II) and Cr(VI) from aqueous solution. The coexisting Cu(II) (20 mg/L) and Cr(VI) (40 mg/L) were completely removed within 30 min by Cl-LDH in a dosage of 2.0 g/L; the removal rate of Cu(II) was accelerated in the presence of Cr(VI). Moreover, compared with the adsorption of single Cu(II) or Cr(VI), the adsorption capacities of Cl-LDH for Cu(II) and Cr(VI) can be improved by 81.05% and 49.56%, respectively, in the case of coexisting Cu(II) (200 mg/L) and Cr(VI) (400 mg/L). The affecting factors (such as solution initial pH, adsorbent dosage, and contact time) have been systematically investigated. Besides, the changes of pH values and the concentrations of Mg²⁺ and Al³⁺ in relevant solutions were monitored. To get the underlying mechanism, the Cl-LDH samples before and after adsorption were thoroughly characterized by X-ray powder diffraction, transmission electron microscopy, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy. On the basis of these analyses, a possible mechanism was proposed. The coadsorption process involves anion exchange of Cr(VI) with Cl⁻ in Cl-LDH interlayer, isomorphic substitution of Mg²⁺ with Cu²⁺, formation of Cu₂Cl(OH)₃ precipitation, and the adsorption of Cr(VI) by Cu₂Cl(OH)₃. This work provides a new insight into simultaneous removal of heavy metal cations and anions from wastewater by Cl-LDH.