Aerobic wastewater treatment requires extensive aeration, which primary function is to provide oxygen to the biomass responsible for degradation of wastewater constituents. Besides the effective oxygen transfer efficiency aeration is responsible for fluid flow created by bubbles. In this research bubbles were released from plate diffusers and the impact on mixing were analyzed. Various aeration flow rates and initial bubble sizes were calculated. Residence time distributions in each scenario were compared applying numerical tracer study. Outcome of the calculations is that the aeration reduces the theoretical residence time significantly and therefore the traditional sizing methods needs to be revisit in wastewater treatment.
The applications of radiotracers for determination of impulse response as Residence Time Distribution (RTD) as well as technical conditions for realization of experiment in industry create special requests for data processing. The table of required corrections and methods for RTD analysis with the basic information is presented. The methods for the raise background subtraction, correction for variable flow and new algorithms for RTD analysis from response to arbitrary input function and from the response distorted by the recirculation flow in so called black or gray box system are presented.
Authors:Matthew Coblyn, Agnieszka Truszkowska and Goran Jovanovic
Microchannel-based hemodialysis has a potential to improve survival rates and quality of life for end-stage renal disease patients compared to conventional hemodialysis technology. Characterization of hydrodynamic behavior in microchannel geometries is necessary for improving flow uniformity, a critical challenge in realizing a commercial device. A test loop was developed for measuring the impulse response of a tracer dye injected into a dialyzer test article for the purpose of developing residence time distributions (RTD) to characterize lamina design. RTD variance tended to lower for designs that are more dominated, volume-wise, by the microchannel array versus the headers. RTD results also emphasize how defect issues can significantly impact a microchannel device via discrepancies between conceptual and operational devices. A multisegmented CFD model, developed for pairing with the impulse response test loop and dialyzer, showed good agreement between visual observation of the tracer in simulations and experiments, and the shape and peak of the output profiles.
Batch contact and column experiments were performed to evaluate the effect of residence time on cesium removal from two simulated Hanford tank wastes using SuperLig® 644 resin. The two waste simulants mimic the compositions of tanks 241-AZ-102 and 241-AN-107 at the U.S. Department of Energy (DOE) Hanford site. A single column made of glass tube (2.7-cm i.d.), which contained ~100 ml of H-form SuperLig® 644 resin was used in the column experiments. The experiments each consisted of loading, elution, and regeneration steps were performed at flow rates ranging from 0.64 to 8.2 BV/h for AZ-102 and from 1.5 to 18 BV/h for AN-107 simulant. The lowest flow rates of 0.64 and 1.5 BV/h were selected to evaluate less than optimal flow conditions in the plant. The range of the flow rates is consistent with the River Protection Project design for the waste treatment plant (WTP) columns, which will operate at a flow rate between 1.5 to 3 BV/h. Batch contact experiments were also performed for two batches of SuperLig® 644 to determine the equilibrium distribution coefficients (Kd) as a function of Cs concentration. The column experiments revealed that adequate column loading for Cs on SuperLig® 644 (50% breakthrough at 100 bed volumes) can be achieved for the two simulated Hanford tank wastes at the nominal plant flow rates of 1.5 and 3 BV/h (residence times 40 and 20 minutes). The column performance was marginally improved at flow rates below the nominal rates. At flow rates higher than the nominal, the Cs loading deteriorated significantly. The SuperLig® 644 was eluted effectively with 0.5M nitric acid. The elution required approximately 15 BVs to reduce Cs concentration to below 1% of initial Cs concentration in the feeds.
Authors:S. Sugihara, S. Osaki, T. Baba, Y. Tagawa, Y. Maeda and Y. Inokura
Activity concentrations of radionuclides,7Be,210Pb and210Po, in precipitation (rain, throughfall and stemflow), wood and soil were determined by using gamma-ray and alpha-ray spectrometry
to estimate the migration behavior of these radionuclides in the forest canopy. The activity ratios between output and input
precipitations for the forest canopy were 0.53 of7Be, 0.79 of210Pb and 1.5 of210Po for Pasania edulis forest. A dynamic model of the transport and fate of radionuclides in the forest ecosystem was constructed.
Mean residence times of radionuclides were 56 days for7Be, 765 days for210Pb and 653 days for210Po for Pasania edulis forest.
Authors:Jun-ichi Yoshida, Heejin Kim and Aiichiro Nagaki
time (the time the solution remains in the reactor) is 10 s. If the flow speed is increased to 1 m/s, the average residencetime is 10 ms. The speed 1 m/s (3600 m/h) is a little bit slower than the speed at which the man is walking. The reaction time of
Authors:X. X. Han, X. M. Jiang, Z. G. Cui, J. W. Yan and J. G. Liu
retort at low retorting temperatures ranging from 400 to 520 °C [ 8 ], showing that an increase in the retorting temperature, the residencetime, and the heating time has positive significant effect on improving the yield of shale oil, and a middle
Moullec Y. Potier O., Gentric C., Leclerc J. P. Flow field and residencetime distribution simulation of a cross-flow gas-liquid wastewater treatment reactor using CFD, Chemical Eng. Science , Vol. 6., 2008, pp. 2436
Authors:Abdullah Altayban, Mahmoud Kandeel, Yukio Kitade and Mohammed Al-nazawi
level at zero time; MRT, mean residencetime; and Cl, clearance rate ( Table 2 ). Since MIC values of cefquinome against important pathogens of camel calves are not available, the MIC 50 values from other animal species were retrieved ( Table 3 ). The
necessary to get sufficiently high gas concentrations for the detection of even small concentration changes, and a short residencetime, which was needed to prevent peak broadening. These goals were reached by a newly designed measuring cell from Thermo