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241.
以漂珠(FP)为载体,采用溶胶-凝胶-浸渍法制备了漂浮负载型CdS/TiO2/FP复合膜光催化剂,通过SEM、XRD对其结构进行了表征.以甘草膦农药的光催化降解为模型反应,使用不同光源研究了CdS/TiO2/FP的光催化性能,探讨了影响催化剂活性的因素及采用太阳光做光源处理草甘膦的可行性.结果表明,经4层镀膜500℃热处理的20%(w/w)CdS/TiO2/FP光催化剂具有良好的光催化性能,最佳降解条件为:催化剂加入量3 g/L,初始pH 7~9,Fe2 浓度为2.0×10-3 mol/L.通气量200 mL/min.在最佳条件下,对135 mg/L草甘膦溶液降解率可以分别达到96.3%(125 W高压汞灯,60 min)和82.4%(太阳光,180 min). 相似文献
242.
Pambrun V Marquot A Racault Y 《Environmental science and pollution research international》2008,15(7):592-599
Background, aims, and scope Sometimes, urban wastewaters convey a more or less significant part of toxic products from industries or the craft industry.
Nitrifying activity can be affected by these substances, implying higher ammonia concentrations in the outlet effluent and
contributing to toxicity for the aquatic environment. Moreover, the more stringently treated wastewater standards now require
a reliable treatment for nitrogen. One of the key issues is the identification of the inhibition behavior of nitrifying bacteria
facing a toxic substance. This new understanding could then finally be integrated into models in order to represent and to
optimize wastewater treatment plants (WWTP) operation in cases involving ‘toxic scenarios’.
Materials and methods The toxic substances studied in this work, cadmium and 3.5-dichlorophenol (3.5-DCP), are representative of chemical substances
commonly found in municipal sewage and industrial effluents and symbolize two different contaminant groups. The effects of
Cd and 3.5-DCP on nitrification kinetics have been investigated using respirometry techniques.
Results IC50 values determination gives concentrations of 3.1 mg/L for 3.5-DCP and 45.8 mg/L for Cd at 21 ± 1°C. The variation to
low temperature seems to have no real effect on IC50 for DCP, but induces a decrease of cadmium IC50 to 27.5 mg/L at 14°C.
Finally, specific respirometric tests have been carried out in order to determine the potential effect of these toxic substances
on the nitrifying decay rate b
a
. No significant effect has been noticed for Cd, whereas the presence of 3.5-DCP (at IC50 concentration) induced a dramatic
increase of b
a
at 20°C. The same behavior has been confirmed by experiments performed in winter periods with a sludge temperature around
12°C.
Discussion The target substances have different modes of action on activity and mortality, notably due to the abilities of the contaminant
to be precipitated, accumulated, or even to be progressively degraded. Studies realized at low temperature confirmed this
assumption, and put in evidence the effect of temperature on toxic substances capable of being biosorbed. However, the change
in the sludge sample characteristics can be pointed out as a problem in the investigation of the temperature effect on nitrification
inhibition, as biosorption, bioaccumulation, and predation are directly linked to the sludge characteristics (VSS concentration,
temperature) and the plant operating conditions (loading rates, sludge age, etc.).
Conclusions This work brings new understandings concerning the action mode of these specific contaminants on nitrifying bacteria and,
in particular, on the role of temperature. The experiments lead to the determination of the IC50 values for both toxic substances
on biological nitrification. The inhibition mechanisms of Cd and 3.5-DCP on nitrifying activity have been simply represented
by a non-competitive inhibition model.
Recommendations and perspectives Other experiments carried out in a continuous lab-scale pilot plant should be done with a proper control of the operating
conditions and of the sludge characteristics in order to better understand the mechanisms of nitrification inhibition for
each contaminant. Finally, these first results show that toxic substances can have an effect on the growth rate but also on
the decay rate, depending on the characteristics of the toxic substance and the sludge. This eventual double effect would
imply different strategies of WWTP operation according to the behavior of the contaminant on the bacteria. 相似文献
243.
Pb/Zn冶炼废渣中重金属的生物浸出-盐浸处理 总被引:3,自引:0,他引:3
利用中温嗜热菌对某铅锌冶炼废渣进行生物浸出盐浸处理研究,并根据国家固体废物浸出毒性方法(HJ/T299-2007)对盐浸后余渣进行毒性分析。研究结果表明,在pH 1.5、温度65℃、矿浆浓度5%的优化条件下生物浸出3 d后,废渣中Cu、In、Ga和Zn的浸出率分别达到了91.5%、91.8%、84.9%和93.4%;盐浸生物浸出渣,其浸出液中Ag、Pb浓度分别为7.6和247.5 mg/L,可从废渣中有效回收Cu、In、Ga、Zn、Ag和Pb。生物浸出盐浸处理后余渣约为原渣量的70%;毒性分析浸出液中重金属元素Ag、As、Cd、Cu、Pb和Zn浓度分别为2~3.5、2~3、0.3~0.5、30~50、2~4、20~60 mg/L,低于国家危险废物鉴别标准(GB5085.3-2007)。根据试验结果,提出了针对冶炼废渣资源化、减量化、无害化的生物浸出盐浸联用工艺。 相似文献
244.
245.
The present paper describes an effort for developing the total maximum daily load (TMDL) for phosphorus and a load reduction
strategy for the Feitsui Reservoir in Northern Taiwan. BASINS model was employed to estimate watershed pollutant loads from
nonpoint sources (NPS) in the Feitsui Reservoir watershed. The BASINS model was calibrated using field data collected during
a 2-year sampling period and then used to compute watershed pollutant loadings into the Feitsui Reservoir. The simulated results
indicate that the average annual total phosphorus (TP) loading into the reservoir is 18,910 kg/year, which consists of non-point
source loading of 16,003 kg/year, and point source loading of 2,907 kg/year. The Vollenweider mass balance model was used
next to determine the degree of eutrophication under current pollutant loading and the load reduction needed to keep the reservoir
from being eutrophic. It was estimated that Feitsui Reservoir can becoming of the oligotrophic state if the average annual
TP loading is reduced by 37% or more. The results provide the basis on which an integrated control action plan for both point
and nonpoint sources of pollution in the watershed can be developed. 相似文献
246.
Use of USLE/GIS Methodology for Predicting Soil Loss in a Semiarid Agricultural Watershed 总被引:1,自引:0,他引:1
The Universal Soil Loss Equation (USLE) is an erosion model to estimate average soil loss that would generally result from
splash, sheet, and rill erosion from agricultural plots. Recently, use of USLE has been extended as a useful tool predicting
soil losses and planning control practices in agricultural watersheds by the effective integration of the GIS-based procedures
to estimate the factor values in a grid cell basis. This study was performed in the Kazan Watershed located in the central
Anatolia, Turkey, to predict soil erosion risk by the USLE/GIS methodology for planning conservation measures in the site.
Rain erosivity (R), soil erodibility (K), and cover management factor (C) values of the model were calculated from erosivity
map, soil map, and land use map of Turkey, respectively. R values were site-specifically corrected using DEM and climatic
data. The topographical and hydrological effects on the soil loss were characterized by LS factor evaluated by the flow accumulation
tool using DEM and watershed delineation techniques. From resulting soil loss map of the watershed, the magnitude of the soil
erosion was estimated in terms of the different soil units and land uses and the most erosion-prone areas where irreversible
soil losses occurred were reasonably located in the Kazan watershed. This could be very useful for deciding restoration practices
to control the soil erosion of the sites to be severely influenced. 相似文献
247.
Syed S 《Environmental monitoring and assessment》2007,130(1-3):311-322
‘Metal ash’ presents a waste disposal problem in most of the developing countries as the industries employ obsolete technologies.
In this paper we describe analysis of tin ash, zinc ash and aluminium ash by means of optical methods, such as X-ray diffraction
(XRD), inductively coupled plasma mass spectrometry (ICP-MS), electron probe micro analysis (EPMA), scanning electron microscopy
(SEM) and chemical methods. The results of tin ash obtained by XRD method matched well with the cassiterite, a naturally occurring
mineral of tin. ICP-MS studies reveal the presence of a large number of tracer metals, which may cause pollution by tertiary
dispersion and this aspect is discussed. Conversely, the data generated by chemical methods are limited. However, the methods
are simple and cost-effective. Then, they can easily be adopted by low-budget industries. Simple and cost-effective process
to recover tin from tin ash is described. It is based on heating tin ash with sodium cyanide to about 900°C to separate tin
component from the metal ash. The process recovers good quality tin and offers a very high yield. The process can be scaled
up to small pilot plant. 相似文献
248.
249.
250.
山东省主要河流中抗生素污染组成及空间分布特征 总被引:1,自引:0,他引:1
采用固相萃取-液相色谱/串联质谱法研究了山东省境内四大流域主要河流中抗生素污染组成及空间分布特征,涉及我国用量最大的6类共20种抗生素。结果表明:20种抗生素均有检出,且大环内酯类、喹诺酮类和四环素类抗生素整体检出浓度较高。就流域而言,半岛诸河流域抗生素污染较小,平均总质量浓度61.4 ng/L;海河流域、小清河流域和淮河流域相对较为严重,平均总质量浓度分别为232、175、118 ng/L。抗生素空间分布呈现一定的规律,检出浓度较高的点位主要集中在人口密集区下游,抗生素污染与周边生活污水、养殖企业废水和城市污水处理厂排水密切相关,而且抗生素组成可从一定程度上反映出污染来源。 相似文献