خيارات البحث
النتائج 1011 - 1020 من 1,310
Optimization of the Adsorption Conditions for the Decolorization and COD Reduction of Methylene Blue Aqueous Solution using Low-Cost Adsorbent النص الكامل
2011
Low, Ling Wei | Teng, Tjoon Tow | Alkarkhi, Abbas F. M. | Ahmad, Anees | Morad, Norhashimah
The performance of raw bagasse (RB), and tartaric acid-modified bagasse (TAMB) as adsorbents on decolorization and chemical oxygen demand (COD) reduction of methylene blue (MB) aqueous solution was studied. The effects of five factors namely: adsorbent dosage, pH, shaking speed, contact time, and temperature on decolorization and COD reduction were studied and optimized using central composite design (CCD). The results of the analysis show that all selected factors exhibit significant effect on decolorization and COD reduction. Maximum decolorization (78.16%) and COD reduction (77.95%) for RB was achieved at 0.82 g of adsorbent dosage, pH 9.4, 122 rpm of shaking speed, 44 min of contact time, and 55°C. For TAMB, maximum decolorization (99.05%) and COD reduction (98.45%) was achieved at 0.78 g adsorbent dosage, pH 9.4, shaking speed of 120 rpm, 34 min contact time, and 49°C. TAMB was found to be more effective than RB in decolorization and COD reduction of MB aqueous solution.
اظهر المزيد [+] اقل [-]Efficiency of Mesocosm-Scale Constructed Wetland Systems for Treatment of Sanitary Wastewater Under Tropical Conditions النص الكامل
2011
Caselles-Osorio, Aracelly | Villafañe, Patricia | Caballero, Vanessa | Manzano, Yelena
Subsurface-flow constructed wetlands technology (SSFW) has been used successfully for treating sanitary wastewater throughout North America and Europe. However, treatment wetland technologies have not been used extensively in the tropics. To advance tropical studies, a pilot-scale SSFW was constructed on the campus of the University of the Atlantic in Barranquilla, Colombia. The systems performance was monitored from January to July of 2009. The treatment system consisted of a 760-L septic tank followed by three mesocsom-scale subsurface-flow constructed wetlands in parallel arrangement. Clarified wastewater was batch loaded to each unit at a rate of 53 L/m2/day to affect a hydraulic retention time of approximately 3 days. One of the treatment units served as a non-planted control (gravel only), while the other two treatment units were planted with either Eriochloa aristata or Eleocharis mutata. The objective of this study was to evaluate the comparative efficacy of the treatment units (planted vs. unplanted), with respect to their abilities to augment treatment of septic tank effluent (sanitary wastewater). Monitored parameters included plant biomass, oxidation–reduction potential, chemical oxygen demand (COD), temperature, dissolved oxygen, pH, ammonia–nitrogen (NH4 +–N) nitrate– and nitrite–nitrogen (NO3–N, NO2–N), phosphates (PO4 −), and coliform bacteria. Total biomass (dry matter) was 2.84 and 0.87 Kg/m2 for E. aristata and E. mutata, respectively. Redox potential in the plant rizospheres averaged −172 mV (±164.1) in E. aristata, 29 mV (±251.1) in E. mutata, and 32 mV (±210.5) in the unplanted control. COD removal was superior in planted vs. non-planted systems (>75% vs. 47%). Ammonia and total phosphorus removal averaged 69% and 85%, respectively, in planted systems versus 31% and 59% in the unplanted system. Removal of total and fecal coliforms averaged 96%. Results of this pilot study revealed that SSFW technology in the tropics can provide significant removal of organic matter, nutrients, and bacteria from clarified sanitary wastewater.
اظهر المزيد [+] اقل [-]Use of Anguilla anguilla for Biomonitoring Persistent Organic Pollutants (POPs) in Brackish and Riverine Waters in Central and Southern Italy النص الكامل
2011
Bettinetti, Roberta | Galassi, Silvana | Quadroni, Silvia | Volta, Pietro | Capoccioni, Fabrizio | Ciccotti, Eleonora | De Leo, Giulio A.
One of the aims of the Water Framework Directive 2000/60/CE is to assess the ecological status of water bodies in Europe in relation to priority contaminants, including some persistent organic pollutants (POPs). Recognizing the benefits of measuring hydrophobic compounds in biota tissues rather than in water, we used the European eel Anguilla anguilla in the present study as a bioindicator species for monitoring POPs in freshwater/brackish environments. We present the results of a contamination analysis of eels carried out in three Italian sites representative of different pollution levels: the last part of Tevere River, which flows through a very urbanized and industrialized area, Caprolace Lake and Lesina Lagoon, inside two different protected national parks. A very high pollution variability was recorded within each group of eels, in particular for those caught at Caprolace Lake. Due to this high variability, inter-population comparisons were carried out only between eels collected in Tevere River and Lesina Lagoon. PCBs values in Lesina Lagoon were two orders of magnitude lower than those measured in Tevere River, while no significant differences were found for levels of DDT compounds. Our results confirm the suitability of the eel as an indicator of persistent bioaccumulative pollutants in brackish environments and rivers where it can be easily caught, but we are sceptical of its use in deep lakes where its capture might be problematic considering standard operation procedures for fish sampling.
اظهر المزيد [+] اقل [-]Emissions from Ethers and Organic Carbonate Fuel Additives: A Review النص الكامل
2011
Arteconi, Alessia | Mazzarini, Alessandro | Di Nicola, Giovanni
This paper is a review of the available literature on the main features of 11 of the most widely adopted oxygenated additives to base gasoline and diesel, focusing particularly on the emissions from the oxygenates considered as additives. The oxygenated additives studied are methyl tert-butyl ether, ethyl tertiary butyl ether, tert-amyl ethyl ether, tertiary amyl methyl ether, isopropyl ether, dimethyl carbonate, dimethoxymethane, dibutyl ether, diglycol methyl ether, diethyl carbonate, and 2-methoxyethyl acetate.
اظهر المزيد [+] اقل [-]Heavy Metal Accumulation in Plant Species Indigenous to a Contaminated Portuguese Site: Prospects for Phytoremediation النص الكامل
2011
Moreira, Helena | Marques, Ana P. G. C. | Rangel, António O. S. S. | Castro, Paula M. L.
Phytoremediation is a promising alternative to conventional soil clean-up methods; however, up to date, there is still not enough information on plant species suitable for application in this field of science. Therefore, plant screening on contaminated sites can lead to the identification of further species of interest. In the present study, pedological and botanical characteristics of an industrialised area known for its metal contamination, in special with Zn—Esteiro de Estarreja, in Portugal—were examined in a 1-year screening. Twenty-seven species were found, with a higher occurrence and variability in the summer/spring season. Zinc levels in the tissues of the collected plant samples ranged from 34 mg kg−1 in shoots to 2,440 mg kg−1 in roots of different species. Species as Verbascum virgatum, Hypochoeris radicata, Phalaris arundinacea, Conyza bilbaoana, Paspalum urvillei and Aster squamatus have shown high Zn shoot accumulation and bioconcentration factors (BCFshootsâ>â1) and high metal translocation factors (TFâ>â1). Others, namely Spergularia capillacea, excluded Zn from the shoot tissues and stored the metal at the root zone (BCFrootsâ>â1), behaving as tolerant plants. Plants were also screened for arbuscular mycorrhizal fungi colonisation, and only few species showed mycorrhizal presence, namely C. bilbaoana, Hirschfeldia incana, Epilobium tetragonum, Conyza sumatrensis, Pteridium aquilinum, P. urvillei and A. squamatus. The present work showed important indigenous species that can cope with installed harsh conditions and with potential for utilisation in phytoremediation strategies, either through metal removal to aerial parts or through its immobilisation in the root zone.
اظهر المزيد [+] اقل [-]Occurrence of Sexual Hormones in Sediments of Mangrove in Brazil النص الكامل
2011
Froehner, Sandro | Machado, Karina Scurupa | Stefen, Elisa | Nolasco, Marcelo
The presence of sexual hormones (female estrogens) was assessed in sediments of a mangrove located in the urban region of southern Brazil. The estrogens are involved in human sexual reproduction. They act as the chemical messengers, and they are classified as natural and synthetic. The estrogens inputs in the environment are from treated and untreated sewage. The presence of estrogens in sewage is excretion from the female due to natural production and use of contraceptives (synthetic estrogens). With the indiscriminate release of sewage into the environment, estrogens can be found in rivers, lakes, and even in oceans. In this work, the presence of estrone (E1), 17-β-estradiol (E2), and 17-α-ethynilestradiol (EE2) in eight sedimentary stations in Itacorubi mangrove located on Santa Catarina Island, south Brazil, was investigated. Historically, the Itacorubi mangrove has been impacted by anthropogenic activities because the mangrove is inserted in the urban area of the Florianopolis. The estrogen EE2, used as contraceptive, had the highest concentration in mangrove sediment, 129.75 ± 3.89 ng/g. E2 was also found, with its concentration ranging from 0.90 ± 0.03 to 39.77 ± 1.19 ng/g. Following the mechanism, under aerobic or anaerobic conditions, E2 will first be oxidized to E1, which is further oxidized to unknown metabolites and finally to CO2 and water (mineralized). EE2 is oxidized to unknown metabolites and also finally mineralized. Theoretically, under anaerobic conditions, EE2 can be reduced to E1 even in environments such as mangrove which is essentially anaerobic.
اظهر المزيد [+] اقل [-]Significance of Silver Birch and Bushgrass for Establishment of Microbial Heterotrophic Community in a Metal-Mine Spoil Heap النص الكامل
2011
Sułowicz, Sławomir | Płociniczak, Tomasz | Piotrowska-Seget, Zofia | Kozdrój, Jacek
Differences in the culturable fractions of total and metal-tolerant bacteria inhabiting bulk soil of a metal-mine spoil heap and the rhizosphere of silver birch (Betula pendula) or bushgrass (Calamagrostis epigejos), completed with changes in total microbial community structure in the soil, were assessed by MIDI-FAME (fatty acid methyl ester) profiling of whole-cell fatty acids. In addition, the abundance of metal-tolerant populations among the culturable bacterial communities and their identity and the metal-tolerance patterns were determined. The high proportions of Cu- and Zn-tolerant bacteria that ranged from 60.6% to 94.8% were ascertained in the heap sites. Within 31 bacterial isolates obtained, 24 strains were Gram-positive and Arthrobacter, Bacillus, Rathayibacter, Brochothrix, and Staphylococcus represented those identified. Minimum inhibitory concentration (MIC) data indicated that several strains developed multi-metal tolerance, and the highest tolerance to Cu (10 mM) and Zn (12 mM) was found for Pseudomonas putida TP3 and three isolated strains (BS3, TP12, and SL16), respectively. The analysis of FAME profiles obtained from the culturable bacterial communities showed that Gram-positive bacteria predominated in bulk soil of all heap sites. In contrast, the rhizosphere communities showed a lower proportion of the Gram-positive group, especially for silver birch. For the total microbial community, mostly Gram-negative bacteria (e.g., Pseudomonas) inhabited the heap sites. The results suggest that the quantitative and qualitative development of heterotrophic microbiota in the soil of the metal-mine spoil heap seems to be site-dependent (i.e., rhizosphere vs. bulk soil), according to differences in the site characteristics (e.g., enrichment of nutrients and total metal concentrations) and impact of plant species.
اظهر المزيد [+] اقل [-]An Approach to Temporally Disaggregate Benzo(a)pyrene Emissions and Their Application to a 3D Eulerian Atmospheric Chemistry Transport Model النص الكامل
2011
Aulinger, Armin | Matthias, Volker | Quante, Markus
To simulate the atmospheric fate of air pollutants, it is first necessary to know the emission rates that describe the release of pollutants into ambient air. For benzo(a)pyrene emission data are currently only available as yearly bulk emissions while the simulation models typically require temporally resolved emissions (e.g. hourly). Because residential heating is by far the most important source for benzo(a)pyrene, we developed a method to temporally disaggregate these bulk emission data using the linear dependency of benzo(a)pyrene emission rates stemming from residential combustion on ambient temperature. The resulting time-dependent hourly emission rates have been used in a chemical transport model to simulate concentrations and deposition fluxes of benzo(a)pyrene in the year 2000. The same simulations were repeated with constant emission rates and emission rates that varied only seasonally. By comparing the modeling results of the three emission cases with monthly measurements of air concentrations, the characteristic and the benefit of our disaggregation approach is illustrated. The simulations with disaggregated emissions fitted best to the measurements. At the same time the spatial distribution as well as the yearly total deposition was notably different with each emission case even though the yearly total emissions were kept constant.
اظهر المزيد [+] اقل [-]A New Approach to Calculate EMEA’s Predicted Environmental Concentration for Human Pharmaceuticals in Groundwater at Bank Filtration Sites النص الكامل
2011
Müller, Beate | Scheytt, Traugott | Zippel, Matthias | Hannappel, Stephan | Klein-Goedicke, Jutta | Duscher, Klaus
In recent years, human pharmaceutical substances have been increasingly detected in the aquatic environment. Specific attention has been drawn to the occurrence of pharmaceutical substances at bank filtration sites which are used for drinking water production. In the course of the authorisation application for new pharmaceutical compounds, an environmental risk assessment is required. Currently, the expected concentration of the human pharmaceutical compound in groundwater at bank filtration sites is calculated following the guideline Pre-Authorisation Evaluation of Medicines for Human Use issued by the European Medicines Agency (EMEA 2006). A simple estimation is applied: The predicted environmental concentration (PECGW) is the predicted environmental concentration in surface water (PECSW) multiplied with 0.25. A new approach considering the hydraulic and hydrogeological characteristics of bank filtration sites as well as transport processes is presented in this study. First, a numerical groundwater flow model was developed to simulate the groundwater flow processes at bank filtration sites in general. Flow times were calculated as a function of the hydraulic and hydrogeological parameters: hydraulic conductivity, shore-well distance, screen depth and extraction rate. In a second step, the PECGW was calculated based on the compound concentration in surface water and the modelled groundwater flow times considering linear sorption and first-order decay. Sorption and degradation can only be calculated based on the data provided by the pharmaceutical company in the course of the authorisation application. The current approach following the EMEA guideline invariably connects the PECGW with the PECSW without considering sorption and/or degradation processes. We introduce an approach that incorporates the hydraulic process bank filtration and the main transport processes sorption and degradation. The new approach is compound specific as well as aquifer, flow and transport specific resulting in a more realistic PECGW value compared to the old approach.
اظهر المزيد [+] اقل [-]Bioremediation of Pulp and Paper Mill Effluent by Tannic Acid Degrading Enterobacter sp النص الكامل
2011
Singh, Yogendra Prakash | Dhall, Purnima | Mathur, R. M. | Jain, R. K. | vadde Thakur, Vasanta | Kumar, Virendra | Kumar, Rita | Anil Kumar,
Wastewaters from pulp and paper mills are highly toxic and around 250 xenobiotic compounds have been reported in the effluents. Tannic acid degrading bacterium, Enterobacter sp. was isolated from soil by tannic acid enrichment. This isolate was used for bioremediation of pulp and paper mill effluents. Parameters like temperature, agitation, inoculum size and treatment duration were optimized by using Qualiteck-4 software. Reduction in lignin 73% and colour up to 82% was also observed. Encouraging results were observed is reduction of COD, BOD with 16-h retention time in batch culture.
اظهر المزيد [+] اقل [-]