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571.
This work examines the performance of a hydrous ferric oxide (HFO) reactive filtration (RF) process with coupled chemically enhanced secondary treatment (RECYCLE) for phosphorus removal from municipal wastewater (HFO-RF-RECYCLE). A 3-month, 0.95-ML/d (0.25-mgd) demonstration of HFO-RF-RECYCLE was performed at a municipal wastewater treatment plant equipped with oxidation ditches and secondary clarifiers. Influent to the plant averaged 6.0 mg/L phosphorus, with a tertiary effluent average of 0.011 mg/L phosphorus. Iron doses to the plant were low, at 5 mg/L. Inline recycling of HFO solution rejects to the plant influent resulted in a maximum 90.3%, dose-dependent reduction of phosphorus in the secondary effluent at 4.5 ML/d (1.2 mgd). Other results included reduction of total suspended solids and turbidity. A mass balance analysis was performed. We conclude that HFO-RF-RECYCLE may allow very low levels of phosphorus discharge from municipal wastewater treatment plants with a ferric-iron-based tertiary filtration process and residual recycling. 相似文献
572.
Asbj?rn Haaning Nielsen Jes Vollertsen Henriette Stokbro Jensen Heidi Ina Madsen Thorkild Hvitved-Jacobsen 《Water environment research》2008,80(1):16-25
The formation and fate of sulfide in a force main and a downstream-located gravity sewer were investigated in an extensive field study. Sulfide formation in the force main was significant. However, during 14 minutes of transport in the gravity sewer, the sulfide concentration decreased 30%, on average. An application of a conceptual sewer process model for simulating the formation and fate of sulfide was demonstrated. Overall, the model predicted that approximately 90% of the decrease of the sulfide concentration in the gravity sewer was the result of sulfide oxidation and that only a small fraction entered the sewer atmosphere, causing odor and corrosion. Even so, the model predicted concrete corrosion rates of up to 1.2 mm/y in the gravity sewer section. 相似文献
573.
采用自行研发的泥-水界面微孔曝气系统,开展了底泥表面曝气和覆盖对城市重污染河道底泥磷释放及形态分布规律的影响研究.结果表明,微孔曝气能够有效提高上覆水的溶解氧(DO)和沉积物的氧化还原电位(Eh),能够将泥-水界面Eh维持在-100 m V左右,DO提高到6 mg·L-1以上.与对照比较,原位覆盖处理的上覆水DO和Eh有一定提高,但仍明显低于微孔曝气处理.与对照相比较,微孔曝气处理均有效降低上覆水中总磷(TP)和溶解性正磷酸盐(PO3-4)的含量.试验结束时,微孔曝气(A)和微孔曝气+原位覆盖处理(A+C)上覆水中TP含量由初始的0.201 mg·L-1分别降至0.062 mg·L-1和0.050 mg·L-1;上覆水中PO3-4含量由0.086 mg·L-1和0.078 mg·L-1分别降至0.026 mg·L-1和0.023 mg·L-1.与对照相比,微孔曝气处理明显降低了底泥间隙水中TP的浓度,在整个培养期间,其TP含量平均下降38.8%(A)和47.9%(A+C).底泥原位覆盖处理对抑制泥-水界面磷释放能力要弱于微孔曝气处理,而且在试验后期(50 d),上覆水中TP和PO3-4的含量均有所反弹.不管有无覆盖,泥-水界面微孔曝气处理均显著改变了表层底泥磷形态分布特征,显著降低了底泥中铁铝结合态磷(Fe/Al-P)组分比例,而钙结合态磷(Ca-P)含量比例却出现明显增加.单一的表面覆盖处理对底泥磷形态分布特征没有显著影响(P0.05).研究表明,与单一的处理效果相比较,泥-水界面纳米微孔曝气处理,并结合底泥原位覆盖,更有利于抑制城市重污染河道泥-水界面中磷的释放风险. 相似文献
574.
Degradation of azo dyes in water by Electro-Fenton process 总被引:19,自引:0,他引:19
Elodie?Guivarch Stephane?Trevin Claude?Lahitte Mehmet?A.?OturanEmail author 《Environmental Chemistry Letters》2003,1(1):38-44
The degradation of the azo dyes azobenzene, p-methyl red and methyl orange in aqueous solution at room temperature has been studied by an advanced electrochemical oxidation
process (AEOPs) under potential-controlled electrolysis conditions, using a Pt anode and a carbon felt cathode. The electrochemical
production of Fenton's reagent (H2O2, Fe2+) allows a controlled in situ generation of hydroxyl radicals (·OH) by simultaneous reduction of dioxygen and ferrous ions on the carbon felt electrode. In turn, hydroxyl radicals react
with azo dyes, thus leading to their mineralization into CO2 and H2O. The chemical composition of the azo dyes and their degradation products during electrolysis were monitored by high performance
liquid chromatography (HPLC). The following degradation products were identified: hydroquinone, 1,4-benzoquinone, pyrocatechol,
4-nitrocatechol, 1,3,5-trihydroxynitrobenzene and p-nitrophenol. Degradation of the initial azo dyes was assessed by the measurement of the chemical oxygen demand (COD). Kinetic
analysis of these data showed a pseudo-first order degradation reaction for all azo dyes. A pathway of degradation of azo
dyes is proposed. Specifically, the degradation of dyes and intermediates proceeds by oxidation of azo bonds and aromatic
ring by hydroxyl radicals. The results display the efficiency of the Electro-Fenton process to degrade organic matter.
Electronic Publication 相似文献
575.
The Influence of Mycorrhiza on Uranium and Phosphorus Uptake by Barley Plants from a Field-contaminated Soil (7 pp) 总被引:3,自引:0,他引:3
Chen B Zhu YG Zhang X Jakobsen I 《Environmental science and pollution research international》2005,12(6):325-331
Background Recent studies indicated that arbuscular mycorrhizal fungi (AMF) play important roles in plant accumulation of uranium (U)
from contaminated environments, but the impacts of fertilization practices on functioning of the symbiotic associations, which
are crucial factors influencing plant nutrition and growth responses to mycorrhiza, have rarely been considered.
Materials and Methods In a greenhouse experiment, a bald root barley mutant (brb) together with the wild type (wt) were used to test the role of
root hairs and AMF in uranium (U) uptake by host plants from a U contaminated soil. Nil, 20 and 60 mg KH2PO4-P kg–1 soil were
included to investigate the influences of phosphorus (P) fertilization on plant growth and accumulation of U.
Results Dry matter yield of barley plants increased with increasing P additions and wt produced significantly higher dry weight than
brb. Mycorrhiza markedly improved dry matter yield of both genotypes grown at nil P, whereas only brb responded positively
to mycorrhiza at 20 mg P kg-1. At the highest P level, mycorrhiza resulted in growth depressions in both genotypes, except
for the roots of wt. In general, plant P concentrations increased markedly with increasing P additions and in response to
mycorrhiza.
Mycorrhiza and P additions had no significant effects on shoot U concentrations. However, root U concentrations in both genotypes
were significantly increased by mycorrhiza. On the other hand, shoot U contents increased with increasing P levels, while
20 mg P kg-1 stimulated, but 60 mg P kg-1 marginally affected the U accumulation in roots. Root length specific U uptake was
moderately enhanced both by root hairs and strongly enhanced by mycorrhiza. Moreover, non-inoculated plants generally had
higher shoot-root ratios of U content than the corresponding inoculated controls.
Conclusion Our study shows that AMF and root hairs improves not only P acquisition but also the root uptake of U, and mycorrhiza generally
decreases U translocation from plant root to shoot. Hence, mycorrhiza is of potential use in the phytostabilization of U contaminated
environments.
Perspectives The complex impacts of P on U accumulation by barley plants suggested that U behavior in mycorrhizosphere and translocation
along the soil-fungi-plant continuum as affected by fertilization practices deserve extensive studies for optimizing the function
of mycorrhizal associations for phytoremediation purposes. 相似文献
576.
Yu X Zhou P Zhou X Liu Y 《Environmental science and pollution research international》2005,12(4):221-226
Background Little is known about metabolism rates of environmental chemicals by vegetation. A good model compound to study the variation
of rates among plant species is cyanide. Vascular plants possess an enzyme system that detoxifies cyanide by converting it
to the amino acid asparagine. Knowledge of the kinetic parameters, the half-saturation constant (Km) and the maximum metabolic
capacity (vmax), is very useful for enzyme characterization and biochemical purposes. The goal of this study is to find the
enzyme kinetics (KM and vmax) during cyanide metabolism in the presence of Chinese vegetation, to provide quantitative data
for engineered phytoremediation, and to investigate the variation of metabolic rates of plants.
Methods Detached leaves (1.0 g fresh weight) from 12 species out of 9 families were kept in glass vessels with 100 mL of aqueous
solution spiked with potassium cyanide at 23°C for 28 h. Four different treatment concentrations of cyanide were used, ranging
from 0.44 to 7.69 mg CN/L. The disappearance of cyanide from the aqueous solution was analyzed spectrophotometrically. Realistic
values of the half-saturation constant (KM) and the maximum metabolic capacity (vmax) were estimated by a computer program
using non-linear regression treatments. As a comparison, Lineweaver-Burk plots were also used to estimate the kinetic parameters.
Results and Discussion The values obtained for KM and vmax varied with plant species. Using non-linear regression treatments, values of vmax and
KM were found in a range between 6.68 and 21.91 mg CN/kg/h and 0.90 to 3.15 mg CN/L, respectively. The highest vmax was by
Chinese elder (Sambucus chinensis), followed by upright hedge-parsley (Torilis japonica). The lowest vmax was demonstrated
by the hybrid willow (Salix matssudana x alba). However, the highest KM was found in the water lily (Nymphea teragona), followed
by the poplar (Populus deltoides Marsh). The lowest KM was demonstrated by corn (Zea mays L.). The values of vmax were normally
distributed with a mean of 13 mg CN/kg/h.
Conclusions Significant removal of cyanide from aqueous solution was observed in the presence of plant materials without phytotoxicity,
even at high doses of cyanide. This gives rise to the conclusion that the Chinese plant species used in this study are all
able to efficiently metabolize cyanide, although with different maximum metabolic capacities. A second conclusion is that
the variation of metabolism rates between species is small. All these plants had a similar KM, indicating the same enzyme
is active in all plants.
Recommendations and Outlook Detoxification of cyanide with trees seems to be a feasible option for cleaning soils and water contaminated with cyanide.
For phytoremediation projects, screening appropriate plant species adapted to local conditions should be seriously considered.
More chemicals should be investigated to find common principles of the metabolism of environmental chemicals by plants. 相似文献
577.
Atmospheric BTEX concentrations in the vicinity of the crude oil refinery of the Baltic region 总被引:1,自引:0,他引:1
Baltrėnas P Baltrėnaitė E Serevičienė V Pereira P 《Environmental monitoring and assessment》2011,182(1-4):115-127
Among chemical industries, petroleum refineries have been identified as large emitters of a wide variety of pollutants. Benzene, toluene, ethylbenzene, and xylene (BTEX) form an important group of aromatic volatile organic compounds (VOCs) because of their role in the troposphere chemistry and the risk posed to human health. A very large crude oil refinery of the Baltic States (200,000 bbl/day) is situated in the northern, rural part of Lithuania, 10 km from the town of Ma?eikiai (Lithuania). The objectives of this study were: (1) to determine of atmospheric levels of BTEX in the region rural and urban parts at the vicinity of the crude oil refinery; and (2) to investigate the effect of meteorological parameters (wind speed, wind direction, temperature, pressure, humidity) on the concentrations measured. The averaged concentration of benzene varied from 2.12 ppbv in the rural areas to 2.75 ppbv in the urban areas where the traffic was determined to be a dominant source of BTEX emissions. Our study showed that concentration of benzene, as strictly regulated air pollutant by EU Directive 2008/50/EC, did not exceed the limit of 5 ppbv in the region in the vicinity of the crude oil refinery during the investigated period. No significant change in air quality in the vicinity of the oil refinery was discovered, however, an impact of the industry on the background air quality was detected. The T/B ratio (0.50-0.81) that was much lower than 2.0, identified other sources of pollution than traffic. 相似文献
578.
Tamer?Karay?ld?r?mEmail author Jale?Yan?k Mithat?Yüksel Mehmet?Sa?lam Michael?Haussmann 《Journal of Polymers and the Environment》2005,13(4):365-374
Degradation of a model polymer mixture (PVC/PS/PE) and a waste polymer mixture in the presence of HCl fixators (Red Mud, precipitated CaCO3 and dolamite) was studied using thermal gravimetric analysis (TGA) and a cycled-spheres-reactor. The experiments in cycled-spheres reactor model were performed by stepwise pyrolysis. Liquid products and HCl from each step were collected separately. For the model polymer mixture, the precipitated CaCO3 showed the best effect on the fixation of evolved HCl and the reduction of chlorine content in the liquid products whereas RM yielded the best result for the waste polymer mixture. In addition, using HCl fixator also affected the degradation of both types of polymer mixture, leading to the formation of more gaseous and less residue. 相似文献
579.
M.?A.?de?FigueiredoEmail author D.?M.?Reiner H.?J.?Herzog 《Mitigation and Adaptation Strategies for Global Change》2005,10(4):647-657
This paper examines how legal standards of liability may apply to geologic carbon storage. The liability regime governing
geologic carbon storage will shape the technology's cost-effectiveness and overall attractiveness. We classify potential sources
of liability into operational, in situ, and climate liability. As a first step, we explore in situ liability in the United States. After summarizing legal standards of liability including negligence, breach of implied warranty,
strict liability, and product liability, we discuss how liability may be addressed at the level of the federal government,
state government, industry, and the firm. Finally, we address the implications of judicial treatment of liability for carbon
storage, including the apportionment of liability and the adequacy of current regulations. 相似文献
580.
Prabhata K. Swamee Anil Kumar Misra Rohith P. Poyil Lokesh Choudhary Amandeep Kaur Sudheer Chintalapati 《Environment, Development and Sustainability》2018,20(6):2623-2642
In this study using linear and nonlinear approach, aggregate indices for various water quality parameters were analyzed. Using a linear and nonlinear interpolating surface, various water quality variables at grid points were investigated that is essential for mapping. The values help in constituting a key approach for determining the water quality index (WQI), which converts pollutant concentration data into subindex values and then combines them into a single score. One of the biggest advantages of WQI is its summary and intuitive communication capability which will be extremely helpful for demarcating safe aquifer zones of groundwater and in the selection of suitable method for remedial. The present study also describes pollution potential in ground water of Madhya Pradesh, India. The aggregate indices suggest intermediate to high pollution susceptibility in some region of Madhya Pradesh that may increase further if not managed. The overall interpretation of the study will be helpful in formulating suitable approach for water quality interpretation and sustainable planning of groundwater resources. 相似文献