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511.
This is the fourth in a series of papers through which the authors demonstrate how numerical transport modeling can assist the remediation design engineer in predicting the progress of enhanced reductive dechlorination remediation expected in the field. The first two papers dealt with the hydraulics of delivery and preliminary understanding of substrate‐limited degradation. The third paper compared a simulated substrate‐limited degradation progress to some early results measured at a site. Based on that comparison, conclusions were drawn regarding the differences in degradation rates between a field situation and laboratory studies, and inferences were made about the modeling steps needed to aid in designing enhanced reductive dechlorination systems. Since the presentation of those results, additional rounds of data have been obtained from the field, encompassing a more substantial range of degradation history. In this paper, the authors compare those results with the simulated predictions and present an illustrative example of design modification using the model. ©2016 Wiley Periodicals, Inc. 相似文献
512.
Ali Reza Gheisi Mohammad Reza Alavimoghaddam Amir Dadrasmoghaddam 《Environmental Fluid Mechanics》2006,6(6):549-572
The coherent structure in near-bed turbulent boundary layer of vortex chamber, particularly the bursting events and their associated shear stresses play the main role in sediment flushing process and consequently the trap efficiency of the vortex settling chamber. Hence, three-dimensional velocity measurements were made at 48 points near the bed of physical model of vortex chamber by using Micro-ADV. The pattern of sediment deposition at the bed of vortex settling chamber reveals three separate regions formed by three predominant currents of inlet flow, flushing flow and outlet over flow. Additionally, due to the instability and three-dimensional nature of the bursting events near the bed of chamber, the new method of Markovian–Octant analysis was applied to study the different classes of near-bed stable shear stresses of vortex chamber in three dimensions. Moreover, the role of each class of stable shear stresses on Sediment transport mechanism at the bed of vortex chamber is investigated. 相似文献
513.
The effect of wastewater cations on activated sludge characteristics: effects of aluminum and iron in floc. 总被引:1,自引:0,他引:1
Chul Park Christopher D Muller Mohammad M Abu-Orf John T Novak 《Water environment research》2006,78(1):31-40
Wastewater samples collected from seven wastewater treatment plants (WWTPs) were characterized to assess the impacts of wastewater cations on the activated sludge process. The cations included in this study were sodium (Na+), potassium, ammonium, calcium, magnesium, aluminum (Al), and iron (Fe). Among the selected cations, Al and Fe were of most interest to this study because their role in bioflocculation has not been extensively studied and remains largely unknown. The data showed that WWTPs contained highly varying concentrations of Na+, Al, and Fe in the wastewater and that these cations were responsible for differences between WWTPs as to sludge dewatering rates and effluent quality. In general, a high influent Na+ concentration caused poor sludge dewatering and effluent characteristics. However, when sufficient Al and Fe were present in floc, the deleterious effects of Na+ were offset. The data associated with Al further revealed that waste activated sludge with low Al contained high concentrations of soluble and colloidal biopolymer (protein + polysaccharide), resulting in a high effluent chemical oxygen demand, high conditioning chemical requirements, and poor sludge dewatering properties. These results suggest that Al will improve activated sludge effluent quality by scavenging organic compounds from solution and binding them to floc. 相似文献
514.
Mohammad Ajmal Rifaqat A. K. Rao Bilquees Ara Siddiqui 《Environmental monitoring and assessment》1995,38(1):25-35
The adsorption of metals from aqueous solutions of Pb2+, Zn2+ and Mg2+ on naturally occurring pyrolusite have been studied. The chemical stability of the pyrolusite has been determined in NaOH, H2SO4, HNO3, HCl, NaCl and NK4Cl solutions of various concentrations. Adsorption of the metal ions followed the order Pb2+>Zn2+>Cd2+.The maximum adsorption of Pb2+ (100%) occurred at pH 7. the relation between the amount of Pb2+ adsorbed per unit weight of pyrolusite and the concentration of Pb2+ at equilibrium follows the Freundlich adsorption isotherm.The efficiency of pyrolusite has been demonstrated by removing lead from synthetic waste water. 100% and 96% removal of lead have been achieved from synthetic waste water containing 5 mg l–1 and 120 mg l–1 of Pb2+ respectively at pH 7. The results of these studies suggest that pyrolusite might provide an economical method for the removal of lead from industrial waste water. 相似文献
515.
A study was conducted to determine the levels of heavy metals Cd, Cr, Cu, Fe, Mn, Ni, Pb, and Zn along with physico-chemical parameters in ground waters of Aligarh city, U.P. (India). Twenty seven samples of hand pump water and twenty three samples of municipal water supply were collected from different localities of the Aligarh city, five times during the period of two months at intervals of 12 days. The samples were analysed for physico-chemical characteristics (pH, electrical conductivity, chlorides, sulphates, total hardness, total alkalinity, nitrate-nitrogen, fluoride, calcium and magnesium) and heavy metal contents. The concentrations of heavy metals in the hand pump water samples were found in the ranges of Cd (ND-5.00); Cr (ND-30.00); Cu (ND-82.50); Fe (16.80–460.00); Mn (ND-425.00); Ni (ND-25.00); Pb (ND-25.00) and Zn (28.60–775.00) g l–1. The heavy metal concentrations in the municipal water supply samples were found to be Cd (ND-5.00); Cr (ND-25.00); Cu (ND-37.50); Fe (8.00–37.50); Mn (ND-320.00); Ni (ND-25.00); Pb (ND-25.00) and Zn (2.00–271.87) g l–1.It appears from the results of these studies the concentrations of Cd, Cr, Cu, Ni, Pb, and Zn in the ground waters of the Aligarh City were found to be lower than the prescribed limits of World Health Organisation (1984), whereas the values of Fe and Mn were found above the prescribed limits in some localities. The chloride total hardness and nitrate-nitrogen were comparatively higher in the hand pump water than the municipal supply water. The reason of higher values of these parameters may be ascribed to the surface disposal of sewage wastes, wastes from metal processing industries and other house hold refuses. 相似文献
516.
517.
Abdul Wahab Khan Mohammad Shahedur Rahman Umme Salma Zohora Masahiro Okanami Takashi Ano 《环境科学学报(英文版)》2011
Interest in microbial surfactants has been steadily increasing in recent years due to their diversity, mass production possibility, selectivity, performance under extreme conditions and potential applications in environmental protection. In this study two pentose sugars (xylose and arabinose) were investigated for the submerged fermentation (SmF) of Bacillus subtilis in surfactant production medium for bio-surfactant surfactin production. An excellent vegetative growth of B. subtilis (× 1010 CFU/mL) was observed for xylose and arabinose containing medium which were comparable to glucose supplemented medium. Low growth (× 108 CFU/mL) was found when medium was not supplemented with any of the sugars. Surfactin production in xylose, arabinose and glucose containing medium was 2700, 2600 and 2000 mg/L, respectively, whereas, medium without any sugar showed low surfactin (700 mg/L) production. These results clearly indicate the effect of pentose sugars on production of surfactin. Gradual depletion of the xylose and arabinose were confirmed by HPLC analysis during the growth phase of the strain that ultimately produced the surfactin. 相似文献
518.
Mohammad Mahdi Rezaei Mohammad R. Movahhedy Hamed Moradi Mohammad T. Ahmadian 《Journal of Manufacturing Processes》2012,14(3):199-207
Recently, receptance coupling substructure analysis (RCSA) is used for stability prediction of machine tools through its dynamic response determination. A major challenge is the proper modelling of the substructures joints and determination of their parameters. In this paper, a new approach for predicting tool tip FRF is presented. First, inverse RCSA formulation is extended so that the holder FRFs can be identified directly through experimental modal tests. The great advantage of this formulation is its implementation in arbitrary point numbers along joint length. Therefore, in comparison with previous inverse RCSA approaches, a more realistic joint model can be considered. In addition, due to applying the new approach, additional costly modal tests on the gauged tool are not required. This characteristic makes it possible to determine the holder FRFs without separating the tool; especially in situations where the holder end is inaccessible. The inclusion of joint parameters effect in the identified holder FRFs is another main advantage of such approach. Consequently, for identification of joint parameters, there is no need to use common error optimization based on fitting methods. The effect of overhang length is investigated through some analytical study and also experimental validation. Results show that the predicted tool tip FRF is exact in analytical case. Moreover, due to less noise effect, the predictions based on identified FRFs of longer tools are more accurate than the shorter ones (in experimental case). 相似文献
519.
Iturin A is a cyclic lipopeptide antibiotic and eight different kinds of iturin A have been reported based on its alkyl side chains. As iturin A is a promising biocontrol agent, total production of iturin A was tried to enhance and comparative production of its homologues was investigated by using different nitrogen and carbon sources. When Polypepton S and defatted soybean meal were used, total production as well as the ratio of the iturin A homologues were similar. However, production of iturin A was relatively lower and also the ratio of the iturin A homologues was different when Polypepton was used, where A2 was decreased and A4 was increased. Production ratio of the iturin A homologues was similar for the carbon sources like maltose, mannitol, sucrose and starch but relative production of iturin A2 was much enhanced compared to A3 when lactose or galactose was used. Interestingly production ratio of A4 was increased and A2 and A3 were decreased when no additional carbon source was used, and similar tendency was observed in the homologue ratio with glucose and fructose. Production of iturin A homologue A6 was significantly increased whereas A2 and A3 were decreased when defatted rapeseed cake was used. Utilization of different amino acids did not show significant differences in their production of the iturin A homologues. Oxygen supply found to be the factor affecting the production of iturin A homologues when it was investigated in a varied culture volume size and shaking speed. A2 found to be increased with increased oxygen supply where the production of A3 was affected inversely. 相似文献
520.
Hadi Farahani Mohammad Shokouhi Mehdi Rahimi-Nasrabadi Rouhollah Zare-Dorabei 《毒物与环境化学》2016,98(7):714-726
A simple and totally organic-free (green) method, viz. headspace water-based liquid-phase microextraction combined with high-performance liquid chromatography-ultraviolet detection has been successfully developed for analysis of formic acid and acetic acid in environmental water samples. A microdrop of an aqueous solution of sodium hydroxide was suspended from the tip of a microsyringe needle over the headspace of the stirred sample solution containing the analytes at pH 1.0 for a given time. The microdrop was then retracted into the microsyringe, diluted with HPLC mobile phase, and injected to HPLC. Optimum efficiency has been achieved for: 3.0 µL NaOH microdrop (0.1 mol L?1) exposed for 15 min over the headspace of an aqueous sample of 6.5 mL at 55 °C, containing 15% w/v of Na2SO4, adjusted to pH = 1.0 and stirred at 750 rpm. Under these conditions, enrichment factors of 162 and 187, limits of detection of 0.3 and 0.1 µg L?1 (S/N = 3) with dynamic linear ranges of 1–500 and 0.5–500 µg L?1 were obtained for formic acid and acetic acid, respectively. A reasonable repeatability (5.8% ≤ RSD ≤ 8.8%, n = 6) and satisfactory linearity (r2 ≥ 0.997) illustrated the performance of the method. 相似文献