Powdered activated carbon adsorption of two fishy odorants in water: Trans,trans-2,4-heptadienal and trans,trans-2,4-decadienal

Powdered activated carbon(PAC) adsorption of two fishy odorants, trans,trans-2,4-heptadienal(HDE) and trans,trans-2,4-decadienal(DDE), was investigated. Both the pseudo first-order and the pseudo second-order kinetic models well described the kinetics curves, and DDE was more readily removed by PAC. In isotherm tests, both Freundlich and Modified Freundlich isotherms fitted the experimental data well. PAC exhibited a higher adsorption capacity for DDE than for HDE, which could be ascribed to the difference in their hydrophobicity. The calculated thermodynamic parameters(ΔG~0, ΔH~0, and ΔS~0) indicated an exothermic and spontaneous adsorption process. PAC dosage, p H, and natural organic matter(NOM) presence were found to influence the adsorption process. With increasing PAC dosage, the pseudo first-order and pseudo second-order rate constants both increased. The value of p H had little influence on HDE or DDE molecules but altered the surface charge of PAC, and the maximum adsorption capacity occurred at p H 9. The presence of NOM, especially the fraction with molecular weight less than1 k Dalton, hindered the adsorption. The study showed that preloaded NOM impaired the adsorption capacity of HDE or DDE more severely than simultaneously fed NOM did.     

Activated carbon adsorption of quinolone antibiotics in water: Performance, mechanism, and modeling

The extensive use of antibiotics has led to their presence in the aquatic environment, and introduces potential impacts on human and ecological health. The capability of powdered activated carbon(PAC) to remove six frequently used quinolone(QN) antibiotics during water treatment was evaluated to improve drinking water safety. The kinetics of QN adsorption by PAC was best described by a pseudo second-order equation, and the adsorption capacity was well described by the Freundlich isotherm equation. Isotherms measured at different p H showed that hydrophobic interaction, electrostatic interaction,and π–π dispersion force were the main mechanisms for adsorption of QNs by PAC. A p H-dependent isotherm model based on the Freundlich equation was developed to predict the adsorption capacity of QNs by PAC at different p H values. This model had excellent prediction capabilities under different laboratory scenarios. Small relative standard derivations(RSDs), i.e., 0.59%–0.92% for ciprofloxacin and 0.09%–3.89% for enrofloxacin,were observed for equilibrium concentrations above the 0.3 mg/L level. The RSDs increased to 11.9% for ciprofloxacin and 32.1% for enrofloxacin at μg/L equilibrium levels, which is still acceptable. This model could be applied to predict the adsorption of other chemicals having different ionized forms.     

NirS-type denitrifying bacteria in aerobic water layers of two drinking water reservoirs: Insights into the abundance, community diversity and co-existence model

The nirS-type denitrifying bacterial community is the main drivers of the nitrogen loss process in drinking water reservoir ecosystems.The temporal patterns in nirS gene abundance and nirS-type denitrifying bacterial community harbored in aerobic water layers of drinking water reservoirs have not been studied well.In this study,quantitative polymerase chain reaction (qPCR) and Illumina Miseq sequencing were employed to explore the nirS gene abundance and denitrifying bacterial community structur...     

Characterization of bacterial community and iron corrosion in drinking water distribution systems with O3-biological activated carbon treatment

Bacterial community structure and iron corrosion were investigated for simulated drinking water distribution systems(DWDSs) composed of annular reactors incorporating three different treatments: ozone, biologically activated carbon and chlorination(O_3-BAC-Cl_2);ozone and chlorination(O3-Cl_2); or chlorination alone(Cl_2). The lowest corrosion rate and iron release, along with more Fe_3O_4 formation, occurred in DWDSs with O_3-BAC-Cl_2 compared to those without a BAC filter. It was verified that O_3-BAC influenced the bacterial community greatly to promote the relative advantage of nitrate-reducing bacteria(NRB)in DWDSs. Moreover, the advantaged NRB induced active Fe(III) reduction coupled to Fe(II) oxidation, enhancing Fe_3O_4 formation and inhibiting corrosion. In addition, O_3-BAC pretreatment could reduce high-molecular-weight fractions of dissolved organic carbon effectively to promote iron particle aggregation and inhibit further iron release. Our findings indicated that the O_3-BAC treatment, besides removing organic pollutants in water, was also a good approach for controlling cast iron corrosion and iron release in DWDSs.     

Degradation of indomethacin in river water under stress and non-stress laboratory conditions: degradation products, long-term evolution and adsorption to sediment

The pharmaceutical compound indomethacin is not totally removed in wastewater treatment plants,whose effluents flow into aquatic environments;concentrations in the 0.1-100 ng/L range are commonly found in surface waters,and its fate is unknown.Here,biological,photochemical and thermal degradation assays were conducted under stress and non-stress conditions to estimate its degradation rate in river water and establish its degradation products over time.The results revealed that direct sunlight irradiation promoted the complete degradation of indomethacin(2 μg/L) in less than 6 hr,but indomethacin was detected over a period of 4 months when water was kept under the natural day-night cycle and the exposure to sunlight was partially limited,as occurs inside a body of water.The biological degradation in water was negligible,while the hydrolysis at pH 7.8 was slow.Residues were monitored by ultra-pressure liquid chromatography/quadrupole time-of-flight/mass spectrometry after solid-phase extraction,and six degradation products were found;their structures were proposed based on the molecular formulae and fragmentation observed in high-resolution tandem mass spectra.4-Chlorobenzoic and 2-acetamido-5-methoxybenzoic acids were the long-term transformation products,persisting for at least 30 weeks in water kept under non-stress conditions.Furthermore,the degradation in the presence of sediment was also monitored over time,with some differences being noted.The adsorption coefficients of indomethacin and degradation products on river sediment were calculated;long-term degradation products did not have significant adsorption to sediment.     

Influence of moderate pre-oxidation treatment on the physical, chemical and phosphate adsorption properties of iron-containing activated carbon

A novel adsorbent based on iron oxide dispersed over activated carbon(AC) were prepared, and used for phosphate removal from aqueous solutions. The influence of pre-oxidation treatment on the physical, chemical and phosphate adsorption properties of iron-containing AC were determined. Two series of ACs, non-oxidized and oxidized carbon modified by iron(denoted as AC-Fe and AC/OFe), resulted in a maximum impregnated iron of 4.03% and 7.56%, respectively. AC/O-Fe showed 34.0%–46.6% higher phosphate removal efficiency than the AC-Fe did. This was first attributed to the moderate pre-oxidation of raw AC by nitric acid, achieved by dosing Fe(II) after a pre-oxidation, to obtain higher iron loading, which is favorable for phosphate adsorption. Additionally, the in-situ formed active site on the surface of carbon, which was derived from the oxidation of Fe(II) by nitric acid dominated the remarkably high efficiency with respect to the removal of phosphate. The activation energy for adsorption was calculated to be 10.53 and 18.88 kJ/mol for AC-Fe and AC/OFe, respectively. The results showed that the surface mass transfer and intra-particle diffusion were simultaneously occurring during the process and contribute to the adsorption mechanism.     

Adsorption mechanisms of PFOA onto activated carbon anchored with quaternary ammonium/epoxide-forming compounds: A combination of experiment and model studies

When wood-based activated carbon was tailored with quaternary ammonium/epoxide (QAE) forming compounds (QAE-AC), this tailoring dramatically improved the carbon's effectiveness for removing perfluorooctanoic acid (PFOA) from groundwater. With favorable tailoring, QAE-AC removed PFOA from groundwater for 118,000 bed volumes before half-breakthrough in rapid small scale column tests, while the influent PFOA concentration was 200 ng/L. The tailoring involved pre-dosing QAE at an array of proportions onto this carbon, and then monitoring bed life for PFOA removal. When pre-dosing with 1 mL QAE, this PFOA bed life reached an interim peak, whereas bed life was less following 3 mL QAE pre-dosing, then PFOA bed life exhibited a steady rise for yet subsequently higher QAE pre-dosing levels. Large-scale atomistic modelling was used herein to provide new insight into the mechanism of PFOA removal by QAE-AC. Based on experimental results and modelling, the authors perceived that the QAE's epoxide functionalities cross-linked with phenolics that were present along the activated carbon's graphene edge sites, in a manner that created mesopores within macroporous regions or created micropores within mesopores regions. Also, the QAE could react with hydroxyls outside of these pore, including the hydroxyls of both graphene edge sites and other QAE molecules. This latter reaction formed new pore-like structures that were external to the activated carbon grains. Adsorption of PFOA could occur via either charge balance between negatively charged PFOA with positively charged QAE, or by van der Waals forces between PFOA's fluoro-carbon tail and the graphene or QAE carbon surfaces.     

The control of red water occurrence and opportunistic pathogens risks in drinking water distribution systems: A review

Many problems in drinking water distribution systems (DWDSs) are caused by microbe, such as biofilm formation, biocorrosion and opportunistic pathogens growth. More iron release from corrosion scales may induce red water. Biofilm played great roles on the corrosion. The iron-oxidizing bacteria (IOB) promoted corrosion. However, when iron-reducing bacteria (IRB) and nitrate-reducing bacteria (NRB) became the main bacteria in biofilm, they could induce iron redox cycling in corrosion process. This process enhanced the precipitation of iron oxides and formation of more Fe₃O₄ in corrosion scales, which inhibited corrosion effectively. Therefore, the IRB and NRB in the biofilm can reduce iron release and red water occurrence. Moreover, there are many opportunistic pathogens in biofilm of DWDSs. The opportunistic pathogens growth in DWDSs related to the bacterial community changes due to the effects of micropollutants. Micropollutants increased the number of bacteria with antibiotic resistance genes (ARGs). Furthermore, extracellular polymeric substances (EPS) production was increased by the antibiotic resistant bacteria, leading to greater bacterial aggregation and adsorption, increasing the chlorine-resistance capability, which was responsible for the enhancement of the particle-associated opportunistic pathogens in DWDSs. Moreover, O₃-biological activated carbon filtration-UV-Cl₂ treatment could be used to control the iron release, red water occurrence and opportunistic pathogens growth in DWDSs.     

Adsorptive removal of hydrophobic organic compounds by carbonaceous adsorbents: A comparative study of waste-polymer-based, coal-based activated carbon, and carbon nanotubes

Adsorption of the hydrophobic organic compounds (HOCs) trichloroethylene (TCE), 1,3-dichlorobenzene (DCB), 1,3-dinitrobenzene (DNB) and γ-hexachlorocyclohexane (HCH) on five different carbonaceous materials was compared. The adsorbents included three polymer-based activated carbons, one coal-based activated carbon (F400) and multiwalled carbon nanotubes (MWNT). The polymerbased activated carbons were prepared using KOH activation from waste polymers: polyvinyl chloride (PVC), polyethyleneterephthalate (PET) and tire rubber (TR). Compared with F400 and MWNT, activated carbons derived from PVC and PET exhibited fast adsorption kinetics and high adsorption capacity toward the HOCs, attributed to their extremely large hydrophobic surface area (2700 m²/g) and highly mesoporous structures. Adsorption of small-sized TCE was stronger on the tire-rubber-based carbon and F400 resulting from the pore-filling effect. In contrast, due to the molecular sieving effect, their adsorption on HCH was lower. MWNT exhibited the lowest adsorption capacity toward HOCs because of its low surface area and characteristic of aggregating in aqueous solution.     

Remediation of preservative ethylparaben in water using natural sphalerite: Kinetics and mechanisms

As a typical class of emerging organic contaminants(EOCs), the environmental transformation and abatement of preservative parabens have raised certain environmental concerns. However, the remediation of parabens-contaminated water using natural matrixes(such as, naturally abundant minerals) is not reported extensively in literature. In this study, the transformation kinetics and the mechanism of ethylparaben using natural sphalerite(NS) were investigated. The results show that around 63% of ethy...     

微藻对海水养殖循环水高效碳氮磷一体化去除的研究

海水养殖循环水高盐分和波动的低碳氮比造成水处理困难和亚硝酸盐累积,影响循环水处理利用,其排放造成受纳海域生态环境破坏.本研究采用混合营养型钝顶螺旋藻结合膜光合反应器(MPBR)考察碳氮比对海水养殖循环水碳、氮、磷一体化去除效率及藻生物质产量的影响.结果 表明,在原水碳氮比为5时,钝顶螺旋藻可实现碳、氮、磷高效一体化去除...     

黄土高原两种针叶树种不同器官水碳氮磷分配格局及其生态化学计量特征

植物不同器官水、碳、氮、磷等元素含量及其生态化学计量特征能够反映植物的生态策略及其环境适应性。本研究以黄土高原两种乡土树种油松(Pinus tabulaeformis)和柴松(Pinus tabulaefirmis f.shekanensis)为研究对象,分析了研究区两种树种水、碳、氮和磷在不同器官的含量及其生态化学计量特征,探讨了两种树种基于水、碳、氮和磷分配格局的生态适应策略。结果表明:(1)油松和柴松对水分和碳素的分配格局总体表现为根和叶最大,其次为枝和干,树皮最小;对氮、磷的分配格局则表现为叶片显著高于其他器官。(2)油松将更多的水和氮分配给叶、根等生产性器官,而柴松将更多的水和碳分配给枝、干等防御性器官,反映了柴松较油松具有更加保守的生长策略,能够更好适应逆境条件。(3)植物器官不同元素间通过相互耦合后可以表现出较好的相关性,反映了植物元素之间具有高度复杂的协同关系,这种协同关系的体现形式可能与植物类型及其对外界环境变化的生长适应策略密切相关。     

Comparison of surface water chemistry and weathering effects of two lake basins in the Changtang Nature Reserve, China

The geochemistry of natural waters in the Changtang Nature Reserve,northern Tibet,can help us understand the geology of catchments,and provide additional insight in surface processes that influence water chemistry such as rock weathering on the Qinghai–Tibet Plateau.However,severe natural conditions are responsible for a lack of scientific data for this area.This study represents the first investigation of the chemical composition of surface waters and weathering effects in two lake basins in the reserve(Lake Dogaicoring Qiangco and Lake Longwei Co).The results indicate that total dissolved solids(TDS)in the two lakes are significantly higher than in other gauged lakes on the Qinghai–Tibet Plateau,reaching 20–40 g/L,and that TDS of the tectonic lake(Lake Dogaicoring Qiangco)is significantly higher than that of the barrier lake(Lake Longwei Co).Na+and Cl-are the dominant ions in the lake waters as well as in the glacier-fed lake inflows,with chemical compositions mainly affected by halite weathering.In contrast,ion contents of inflowing rivers fed by nearby runoff are lower and concentrations of dominant ions are not significant.Evaporite,silicate,and carbonate weathering has relatively equal effects on these rivers.Due to their limited scope,small streams near the lakes are less affected by carbonate than by silicate weathering.     

UV、H2O2、O3及其联用工艺对水中DMP的去除效果和降解机理分析

采用UV、H2O2、O3及其联用工艺对自来水本底条件下邻苯二甲酸二甲酯(DMP)的去除效果、特性及降解机理进行了对比和分析.采用单独的UV光照射不能有效去除DMP;而UV-H2O2联用工艺对DMP具有良好的去除效果.在DMP初始浓度约为1.0 mg·L-1,UV光强为133.9μW·cm-2,H2O2投加量为20 mg·L-1的条件下,30 min后DMP的去除效果可以达到73.08%,在降解过程中,监测到DMP氧化产物;当DMP初始浓度约为1.0 mg·L-1,O3投加量为3 mg·L-1时,单独O3氧化DMP的去除率为55.81%;UV-O3联用工艺对DMP的去除效果略优于单独O3氧化,去除效果提高了10%左右.单独O3和UV-O3氧化在初始氧化阶段可形成不同于UV-H2O2工艺的降解产物;UV-H2O2-O3联用工艺能高效氧化水中DMP,O3的投加不但极大的增强了UV-H2O2工艺的氧化性能,同时抑制了UV+H2O2降解过程中DMP氧化产物的生成,并使生成的产物快速降解.几种氧化工艺对DMP去除效果顺序依次为UV＜O3＜UV-O3＜UV-H2O2＜UV-H2O2-O3.     

我国城市黑臭水体综合整治:问题分析、治理思路与措施

随着城市化进程加快和污染物排放量的增大,我国很多城市水体污染负荷超出水体自净能力,水质恶化甚至出现黑臭现象,城市黑臭水体已成为当前公众反映强烈的水环境问题。国务院及相关部门高度重视,接连出台了一系列政策和文件,明确了城市黑臭水体综合整治的目标和方向。介绍了我国城市黑臭水体整治的背景和意义;从点源、面源、内源以及水动力学条件等方面,解析了水体黑臭成因和污染来源;在问题分析的基础上,结合黑臭水体“标本兼治”的目标,提出了黑臭水体整治的总体思路和技术路线;明确了统筹考虑控源截污、内源治理、生态修复、活水保质、监控与管理的黑臭水体治理措施。为加快全国范围内黑臭水体治理,实现治理目标起到重要的借鉴作用。     

华北平原节水技术、灌溉用水量反弹效应与地区异质性——基于Malmquist和LMDI指数分析

很多地区节水技术的应用并未带来农业灌溉用水总量的下降。通过应用中国华北平原地级（直辖）市2000—2018年的面板数据,采用Malmquist指数和LMDI指数进行分解,测算出节水技术带来的农业灌溉用水反弹量和预期农业节水量。结果表明：中国华北平原节水技术引起的农业灌溉用水反弹效应均值为15.02%,这表明华北平原整体并未完全达到节水技术应用带来的预期农业节水量。节水技术应用放松了水资源约束,农户会扩大灌溉面积或高耗水高收益作物的种植,从而削弱节水技术的节水效果。黄河区的农业节水反弹效应程度最大,部分地区甚至会造成农业灌溉用水的增加。节水灌溉面积的增加是农业节水反弹效应的直接原因,农田灌溉水利建设投资的增加和水权市场建设的不完善则是根本原因。     

Nitrated and parent PAHs in the surface water of Lake Taihu, China: Occurrence, distribution, source, and human health risk assessment

Nitrated polycyclic aromatic hydrocarbons (NPAHs) have toxic potentials that are higher than those of their corresponding parent polycyclic aromatic hydrocarbons (PAHs) and thus have received increasing attention in recent years. In this study, the occurrence, distribution, source, and human health risk assessment of 15 NPAHs and 16 PAHs were investigated in the surface water from 20 sampling sites of Lake Taihu during the dry, normal, and flood seasons of 2018. The ΣPAH concentrations ranged from 255 to 7298 ng/L and the ΣNPAH concentrations ranged from not-detected (ND) to 212 ng/L. Among the target analytes, 2-nitrofluorene (2-nFlu) was the predominant NPAH, with a detection frequency ranging from 85% to 90% and a maximum concentration of 56.2 ng/L. The three-ringed and four-ringed NPAHs and PAHs comprised the majority of the detected compounds. In terms of seasonal variation, the highest levels of the ΣNPAHs and ΣPAHs were in the dry season and flood season, respectively. Diagnostic ratio analysis indicated that the prime source of NPAHs was direct combustion, whereas in the case of PAHs the contribution was predominantly from a mixed pattern including pollution from unburned petroleum and petroleum combustion. The human health risk of NPAHs and PAHs was evaluated using a lifetime carcinogenic risk assessment model. The carcinogenic risk level of the targets ranged from 2.09 × 10^?7 to 5.75 × 10^?5 and some surface water samples posed a potential health risk.     

Development of systems for detection, early warning, and control of pipeline leakage in drinking water distribution: A case study

The integrated system for the detection, early warning, and control of pipeline leakage has been successfully developed to manage the pipeline networks of Beijing.