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Joan Garcia - One of the best experts on this subject based on the ideXlab platform.
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Effect of climatic conditions, season and wastewater quality on Contaminant Removal Efficiency of two experimental constructed wetlands in different regions of Spain.
Science of The Total Environment, 2012Co-Authors: Marianna Garfí, Anna Pedescoll, Eloy Bécares, María Hijosa-valsero, Ricardo Sidrach-cardona, Joan GarciaAbstract:Abstract The aim of this study was to examine the effects of climate, season and wastewater quality on Contaminant Removal Efficiency of constructed wetlands implemented in Mediterranean and continental-Mediterranean climate region of Spain. To this end, two experimental horizontal subsurface flow constructed wetlands located in Barcelona and Leon (Spain) were compared. The two constructed wetland systems had the same experimental set-up. Each wetland had a surface area of 2.95 m 2 , a water depth of 25 cm and a granular medium of D 60 = 7.3 mm, and was planted with Phragmites australis . Both systems were designed in order to operate with a maximum organic loading rate of 6 g DBO m − 2 d − 1 . Experimental systems operated with a hydraulic loading rate of 28.5 and 98 mm d − 1 in Barcelona and Leon, respectively. Total suspended solids, biochemical oxygen demand and ammonium mass Removal efficiencies followed seasonal trends, with higher values in the summer (97.4% vs. 97.8%; 97.1% vs. 96.2%; 99.9% vs. 88.9%, in Barcelona and Leon systems, respectively) than in the winter (83.5% vs. 74.4%; 73.2% vs. 60.6%; 19% vs. no net Removal for ammonium in Barcelona and Leon systems, respectively). During the cold season, biochemical oxygen demand and ammonium Removal were significantly higher in Barcelona system than in Leon, as a result of higher temperature and redox potential in Barcelona. During the warm season, statistical differences were observed only for ammonium Removal. Results showed that horizontal subsurface flow constructed wetland is a successful technology for both regions considered, even if winter seemed to be a critical period for ammonium Removal in continental climate regions.
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Contaminant Removal Efficiency depending on primary treatment and operational strategy in horizontal subsurface flow treatment wetlands
Ecological Engineering, 2011Co-Authors: Anna Pedescoll, Angelica Corzo, Eduardo Alvarez, Jaume Puigagut, Joan GarciaAbstract:Abstract This study aimed to evaluate the Contaminant Removal Efficiency of shallow horizontal subsurface flow treatment wetlands (SSF TWs) as a function of (1) primary treatment (hydrolytic upflow sludge blanket (HUSB) reactor vs. conventional settling) and (2) operation strategy (alternation of saturated/unsaturated phases vs. permanently saturated). An experimental plant was constructed, operated and surveyed for the main water quality parameters over a period of 2.5 years. The plant had 3 treatment lines: a control line (settler-wetland permanently saturated), a batch line (settler-wetland operated with saturated/unsaturated phases) and an anaerobic line (HUSB reactor-wetland permanently saturated). In each line wetlands had a surface area of 2.80 m 2 , a water depth of 25 cm and a granular medium D 60 = 7.3 mm, and were planted with common reed. During the study period the wetlands were operated at a hydraulic and organic load of 28.5 mm/d and about 4.7 g BOD/m 2 d, respectively. Effluent average redox potential was lower for the anaerobic line (−45 ± 78 mV) than for the other two lines (3 ± 92.7 and −5 ± 71 mV for control and batch, respectively). Overall, chemical oxygen demand (COD), biochemical oxygen demand (BOD 5 ) and ammonium mass Removal efficiencies were slightly greater for the batch line (88%, 96% and 87%, respectively) than for the control line (83%, 94% and 80%) and the anaerobic line (80%, 87% and 73%). During cold seasons, COD and ammonium Removal in the batch line was around 30% and 50% higher than in the control line, respectively. The results of this study indicate that the implementation of a HUSB reactor as primary treatment did not enhance the treatment capacity of the system (in comparison with a conventional settler). The Efficiency of treatment wetland systems with horizontal subsurface flow can be improved using a batch operation strategy.
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effect of physico chemical pretreatment on the Removal Efficiency of horizontal subsurface flow constructed wetlands
Environmental Pollution, 2007Co-Authors: Aracelly Casellesosorio, Joan GarciaAbstract:Abstract In this study, we tested the effect of a physico-chemical pretreatment on Contaminant Removal Efficiency in two experimental horizontal subsurface-flow constructed wetlands (SSF CWs). One SSF CW was fed with settled urban wastewater, whereas the other with the same wastewater after it had undergone a physico-chemical pretreatment. The SSF CWs were operated with three different hydraulic retention times. During the experiments the effluent concentrations of COD, ammonia N and sulfate were very similar, and, therefore, the physico-chemical pretreatment did not improve the quality of the effluents. COD Removal Efficiency (as percentage or mass surface Removal rate) was slightly greater in the SSF CW fed with pretreated wastewater. Ammonia N Removal Efficiency was, in general, similar in both SSF CWs and very high (80–90%). At the end of the experiments it was observed that in the SSF CW fed with settled wastewater the hydraulic conductivity decreased by a 20%.
Yusong Li - One of the best experts on this subject based on the ideXlab platform.
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study on influencing factors on Removal of chlorobenzene from unsaturated zone by soil vapor extraction
Journal of Hazardous Materials, 2010Co-Authors: Yong Sheng Zhao, Wei Zheng, Yusong LiAbstract:Abstract This paper deals with the influencing factors on Removal of chlorobenzene from unsaturated soils by soil vapor extraction (SVE) method. A series of one-dimensional column experiments were conducted to study the influencing factors for SVE method, the factors included extracted vapor flow rate, soil grain size, extraction mode, soil organic matter content and water content. The results indicated that: (1) the increase of vapor flow rate led to higher Contaminant Removal Efficiency, but the increment of Removal was not significant at higher flow rate levels; (2) soil grain sizes had a great impact on chlorobenzene Removal Efficiency, the coarser the sand, the higher the Removal rate; (3) pulsed vapor extraction and continuous vapor extraction almost had the same Contaminant Removal effects in the sand column; (4) the higher organic content in the soil could decrease the Removal Efficiency; (5) water content in the soil had different impact on the Contaminant Removal Efficiency which related with the organic content in the soil.
Paul Hynds - One of the best experts on this subject based on the ideXlab platform.
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organic Contaminant Removal Efficiency of sodium bentonite clay bc mixtures in high permeability regions utilizing reclaimed wastewater a meso scale study
Journal of Contaminant Hydrology, 2018Co-Authors: Yang Xiao, Zigong Ning, Peiling Yang, Chengcheng Liu, Zhongwei Liu, Paul HyndsAbstract:Wastewater reclamation now represents an effective measure for sustainable water resource management in arid regions, however wastewater components (organic micropollutants) may potentially impact local ecological and/or human health. Previous studies have shown that sodium bentonite/natural clay (BC) mixes may be used to effectively reduce riverbed infiltration in regions characterized by excessively high hydraulic conductivity. Accordingly, the current study sought to investigate the Contaminant Removal Efficiency (Re) of several BC mass ratios in simulated dry riverbeds. Results indicate that the measured Re of NH4+-N, CODcr and BOD5 increased in concurrence with an increasing sodium bentonite ratio, up to a maximum Re of 97.4% (NH4+-N), 55.2% (CODcr), and 51.5% (BOD5). The primary Contaminant Removal site was shown to be the infiltration-reducing (BC) layer, accounting for approximately 40%, 60%, and 70% of NH4+-N, CODcr and BOD5 Removal, respectively. Conversely, the Removal Efficiency of NO3-N was found to be low (<15%), while total phosphorous (TP) was found to actively leach from the infiltration-reduction layer, resulting in measured TP discharges 2.4-4.8 times those of initial infiltration values. The current study provides a technical baseline for the efficacy of sodium bentonite as an effective bi-functional material in areas utilizing reclaimed water i.e. concurrent reduction of infiltration rates (Function 1) and decontamination of reclaimed wastewater infiltration/recharge (Function 2). Findings indicate that sodium bentonite-clay mixes may represent a feasible alternative for managing recharge of non-potable aquifers with reclaimed wastewater.
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Organic Contaminant Removal Efficiency of Sodium Bentonite/clay (BC) Mixtures in High Permeability Regions Utilizing Reclaimed Wastewater: A meso-scale study
Journal of Contaminant Hydrology, 2018Co-Authors: Xiao Yang, Zigong Ning, Peiling Yang, Chengcheng Liu, Zhongwei Liu, Paul HyndsAbstract:Wastewater reclamation now represents an effective measure for sustainable water resource management in arid regions, however wastewater components (organic micropollutants) may potentially impact local ecological and/or human health. Previous studies have shown that sodium bentonite/natural clay (BC) mixes may be used to effectively reduce riverbed infiltration in regions characterized by excessively high hydraulic conductivity. Accordingly, the current study sought to investigate the Contaminant Removal Efficiency (Re) of several BC mass ratios in simulated dry riverbeds. Results indicate that the measured Re of NH4+-N, CODcr and BOD5 increased in concurrence with an increasing sodium bentonite ratio, up to a maximum Re of 97.4% (NH4+-N), 55.2% (CODcr), and 51.5% (BOD5). The primary Contaminant Removal site was shown to be the infiltration-reducing (BC) layer, accounting for approximately 40%, 60%, and 70% of NH4+-N, CODcr and BOD5 Removal, respectively. Conversely, the Removal Efficiency of NO3-N was found to be low (
Yong Sheng Zhao - One of the best experts on this subject based on the ideXlab platform.
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study on influencing factors on Removal of diesel oil from unsaturated zone by soil vapor extraction
Advanced Materials Research, 2011Co-Authors: Li Na Jiao, Zhi Hui Qu, Yong Sheng Zhao, Bing WangAbstract:This paper deals with the influencing factors on Removal of diesel oil from by soil vapor extraction (SVE) method. A series of one-dimensional column experiments were conducted to study the influencing factors for SVE method, the factors included extracted vapor flow rate,water content and the concentration of the Contaminant. The results indicated that: (1) the increase of vapor flow rate led to higher Contaminant Removal Efficiency,but the increment of Removal was not significant at higher flow rate levels;(2) the moisture content is 12% coarse sand elimination rate is bigger than 1% coarse sand;(3) the soil index of oil is higher, the extraction time to be longer, it is not suitable processes with SVE that the diesel oil density is excessively low.
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study on influencing factors on Removal of diesel oil from unsaturated zone by soil vapor extraction
Advanced Materials Research, 2011Co-Authors: Li Na Jiao, Zhi Hui Qu, Yong Sheng Zhao, Bing WangAbstract:This paper deals with the influencing factors on Removal of diesel oil from by soil vapor extraction (SVE) method. A series of one-dimensional column experiments were conducted to study the influencing factors for SVE method, the factors included extracted vapor flow rate,water content and the concentration of the Contaminant. The results indicated that: (1) the increase of vapor flow rate led to higher Contaminant Removal Efficiency,but the increment of Removal was not significant at higher flow rate levels;(2) the moisture content is 12% coarse sand elimination rate is bigger than 1% coarse sand;(3) the soil index of oil is higher, the extraction time to be longer, it is not suitable processes with SVE that the diesel oil density is excessively low.
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study on influencing factors on Removal of chlorobenzene from unsaturated zone by soil vapor extraction
Journal of Hazardous Materials, 2010Co-Authors: Yong Sheng Zhao, Wei Zheng, Yusong LiAbstract:Abstract This paper deals with the influencing factors on Removal of chlorobenzene from unsaturated soils by soil vapor extraction (SVE) method. A series of one-dimensional column experiments were conducted to study the influencing factors for SVE method, the factors included extracted vapor flow rate, soil grain size, extraction mode, soil organic matter content and water content. The results indicated that: (1) the increase of vapor flow rate led to higher Contaminant Removal Efficiency, but the increment of Removal was not significant at higher flow rate levels; (2) soil grain sizes had a great impact on chlorobenzene Removal Efficiency, the coarser the sand, the higher the Removal rate; (3) pulsed vapor extraction and continuous vapor extraction almost had the same Contaminant Removal effects in the sand column; (4) the higher organic content in the soil could decrease the Removal Efficiency; (5) water content in the soil had different impact on the Contaminant Removal Efficiency which related with the organic content in the soil.
Krishna R Reddy - One of the best experts on this subject based on the ideXlab platform.
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effect of ph control at the anode for the electrokinetic Removal of phenanthrene from kaolin soil
Chemosphere, 2003Co-Authors: Richard E Saichek, Krishna R ReddyAbstract:Polycyclic aromatic hydrocarbon (PAH)-contaminated soils exist at numerous sites, and these sites may threaten public health and the environment because many PAH compounds are toxic, mutagenic, and/or carcinogenic. PAHs are also hydrophobic and persistent, so conventional remediation methods are often costly or inefficient, especially when the Contaminants are present in low permeability and/or organic soils. An innovative technique, electrokinetically enhanced in situ flushing, has the potential to increase soil-solution-Contaminant interaction and PAH Removal Efficiency for low permeability soils; however, the electrolysis reaction at the anode may adversely affect the remediation of low acid buffering capacity soils, such as kaolin. Therefore, the objective of this study was to improve the remediation of low acid buffering soils by controlling the pH at the anode to counteract the electrolysis reaction. Six bench-scale electrokinetic experiments were conducted, where each test employed one of three different flushing solutions, deionized water, a surfactant, or a cosolvent. For each of these solutions, tests were performed with and without a 0.01 M NaOH solution at the anode to control the pH. The test using deionized water with pH control generated a higher electroosmotic flow than the equivalent test performed without pH control, but the electroosmotic flow difference between the surfactant and cosolvent tests with and without pH control was minor compared to that observed with the deionized water tests. Controlling the pH was beneficial for increasing Contaminant solubilization and migration from the soil region adjacent to the anode, but the high Contaminant concentrations that resulted in the middle or cathode soil regions indicates that subsequent changes in the soil and/or solution chemistry caused Contaminant deposition and low overall Contaminant Removal Efficiency.
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effect of ph control at the anode for the electrokinetic Removal of phenanthrene from kaolin soil
Chemosphere, 2003Co-Authors: Richard E Saichek, Krishna R ReddyAbstract:Polycyclic aromatic hydrocarbon (PAH)-contaminated soils exist at numerous sites, and these sites may threaten public health and the environment because many PAH compounds are toxic, mutagenic, and/or carcinogenic. PAHs are also hydrophobic and persistent, so conventional remediation methods are often costly or inefficient, especially when the Contaminants are present in low permeability and/or organic soils. An innovative technique, electrokinetically enhanced in situ flushing, has the potential to increase soil–solution–Contaminant interaction and PAH Removal Efficiency for low permeability soils; however, the electrolysis reaction at the anode may adversely affect the remediation of low acid buffering capacity soils, such as kaolin. Therefore, the objective of this study was to improve the remediation of low acid buffering soils by controlling the pH at the anode to counteract the electrolysis reaction. Six bench-scale electrokinetic experiments were conducted, where each test employed one of three different flushing solutions, deionized water, a surfactant, or a cosolvent. For each of these solutions, tests were performed with and without a 0.01 M NaOH solution at the anode to control the pH. The test using deionized water with pH control generated a higher electroosmotic flow than the equivalent test performed without pH control, but the electroosmotic flow difference between the surfactant and cosolvent tests with and without pH control was minor compared to that observed with the deionized water tests. Controlling the pH was beneficial for increasing Contaminant solubilization and migration from the soil region adjacent to the anode, but the high Contaminant concentrations that resulted in the middle or cathode soil regions indicates that subsequent changes in the soil and/or solution chemistry caused Contaminant deposition and low overall Contaminant Removal Efficiency. 2003 Elsevier Science Ltd. All rights reserved.
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assessment of electrokinetic Removal of heavy metals from soils by sequential extraction analysis
Journal of Hazardous Materials, 2001Co-Authors: Krishna R Reddy, Charlie Y Xu, Supraja ChinthamreddyAbstract:Electrokinetic remediation of metal-contaminated soils is strongly affected by soil-type and chemical species of Contaminants. This paper investigates the speciation and extent of migration of heavy metals in soils during electrokinetic remediation. Laboratory electrokinetic experiments were conducted using two diverse soils, kaolin and glacial till, contaminated with chromium as either Cr(III) or Cr(VI). Initial total chromium concentrations were maintained at 1000 mg/kg. In addition, Ni(II) and Cd(II) were used in concentrations of 500 and 250 mg/kg, respectively. The contaminated soils were subjected to a voltage gradient of 1 VDC/cm for over 200 h. The extent of migration of Contaminants after the electric potential application was determined. Sequential extractions were performed on the contaminated soils before and after electrokinetic treatment to provide an understanding of the distribution of the Contaminants in the soils. The initial speciation of Contaminants was found to depend on the soil composition as well as the type and amounts of different Contaminants present. When the initial form of chromium was Cr(III), exchangeable and soluble fractions of Cr, Ni, and Cd ranged from 10 to 65% in kaolin; however, these fractions ranged from 0 to 4% in glacial till. When the initial form of chromium was Cr(VI), the exchangeable and soluble fractions of Cr, Ni and Cd ranged from 66 to 80% in kaolin. In glacial till, however, the exchangeable and soluble fraction for Cr was 38% and Ni and Cd fractions were 2 and 10%, respectively. The remainder of the Contaminants existed as the complex and precipitate fractions. During electrokinetic remediation, Cr(VI) migrated towards the anode, whereas Cr(III), Ni(II) and Cd(II) migrated towards the cathode. The speciation of Contaminants after electrokinetic treatment showed that significant change in exchangeable and soluble fractions occurred. In kaolin, exchangeable and soluble Cr(III), Ni(II), and Cd(II) decreased near the anode and increased near the cathode, whereas exchangeable and soluble Cr(VI) decreased near the cathode and increased near the anode. In glacial till, exchangeable and soluble Cr(III), Ni(II), and Cd(II) were low even before electrokinetic treatment and no significant changes were observed after the electrokinetic treatment. However, significant exchangeable and soluble Cr(VI) that was present in glacial till prior to electrokinetic treatment decreased to non-detectable levels near the cathode and increased significantly near the anode. In both kaolin and glacial till, low migration rates occurred as a result of Contaminants existing as immobile complexes and precipitates. The overall Contaminant Removal Efficiency was very low (less than 20%) in all tests.
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mechanisms controlling toluene Removal from saturated soils during in situ air sparging
Journal of Hazardous Materials, 1998Co-Authors: Robin Semer, Krishna R ReddyAbstract:In situ air sparging is an effective method for removing volatile organic compounds from saturated soils and groundwater. Removal Efficiency levels as high as 98% are often reported, and the remediation time is significantly less than that required for conventional pump and treat technology. However, predictions of the time required for Contaminant mass Removal by air sparging have been approximate at best due to a lack of understanding of the relative importance of the various mechanisms that are responsible for this Contaminant Removal. Volatilization is considered the most dominant mass transfer mechanism during the air sparging process. Dissolution, desorption and biodegradation are the other major mechanisms that determine the rate at which Contaminants are partitioned into different phases or transformed into nonhazardous substances. Additionally, advection, dispersion and diffusion are the transport mechanisms that dictate the overall Contaminant Removal Efficiency. This paper first describes these different mechanisms along with the factors that affect these mechanisms. Then, experimental data is presented for toluene Removal from Ottawa sand and fine gravel by means of air sparging. The tests performed included batch tests to characterize the adsorption characteristics of toluene on the Ottawa sand, and air sparging column tests on both the sand and the gravel to provide information on the effects of soil type and injected air flow rate on the overall air sparging remedial Efficiency. These test results are assessed in light of the mechanisms affecting Contaminant Removal during air sparging.