A laboratory staged anaerobic fluidized membrane bioreactor (SAF-MBR) system was applied to the treatment of primary clarifier effluent from a domestic wastewater treatment plant with temperature decreasing from 25 to 10 °C. At all temperatures and with a total hydraulic retention time of 2.3 h, overall chemical oxygen demand (COD) and biochemical oxygen demand (BOD5) removals were 89% and 94% or higher, with permeate COD and BOD5 of 30 and 7 mg/L or lower, respectively. No noticeable negative effects of low temperature on organic removal were found, although a slight increase to 3 mg/L in volatile fatty acids concentrations in the effluent was observed. Biosolids production was 0.01-0.03 kg volatile suspended solids/kg COD, which is far less than that with aerobic processes. Although the rate of trans-membrane pressure at the membrane flux of 9 L/m(2)/h increased as temperature decreased, the SAF-MBR was operated for longer than 200 d before chemical cleaning was needed. Electrical energy potential from combustion of the total methane production (gaseous and dissolved) was more than that required for system operation.
This paper presents the design optimization of a centrifugal compressor impeller with a hybrid multi-objective evolutionary algorithm. Reynolds-averaged Navier-Stokes (RANS) equations are solved with the shear stress transport turbulence model as a turbulence closure model. Flow analysis is performed on a hexahedral grid through a finite-volume solver. Two objectives, viz., the isentropic efficiency and the total pressure ratio (PR), are selected with four design variables that define the impeller hub and shroud contours in meridian terms for optimizing the system. The validation of numerical results was performed through experimental data for the total PR and the isentropic efficiency. Objective-function values are numerically evaluated through the RANS analysis at design points that are selected through the Latin hypercube sampling method. A fast and elitist non-dominated sorting genetic algorithm (NSGA-II) with an ε-constraint strategy for local search coupled with a surrogate model is used for multi-objective optimization. The surrogate model, the radial basis neural network, is trained on discrete numerical solutions by the execution of leave-one-out cross-validation for the dataset. The trade-off between the two objectives has been ascertained and discussed in the light of Pareto-optimal solutions. The optimization results show that the isentropic efficiency and the total PR are enhanced at both design and off-design conditions through multi-objective optimization.
Bright blue light emission was obtained from a hybrid sol−gel film at room temperature under ultraviolet
(UV) illumination after thermal treatment. The emission intensity was dramatically enhanced and band gap
energy shifted toward red when the heating process continued. The luminescence enhancement pattern of the
sol−gel material doped with methacrylic acid (MA) and zirconium (Zr) was complicated due to the catalytic
role of the MA and/or Zr to form Si−O−C bonds. Both MA and Zr enhanced the luminescence intensity.
The essential components to form the chromophore were a silica backbone and an ester carbon. The Fourier
transform infrared (FTIR) spectra gave evidence of the new bond formation on the ester carbon.
This paper presents field-dependent Bingham and response characteristics of ER fluid under shear and flow modes. Two different types of electroviscometers are designed and manufactured for the shear mode and flow mode, respectively. An ER fluid consisting of soluble chemical starches (particles) and silicon oil is made and its field-dependent yield stress is experimentally distilled at two different temperatures using the electroviscometers. Time responses of the ER fluid to step electric fields are also evaluated under two operating modes. In addition, a cylindrical ER damper, which is operated under the flow mode, is adopted and its measured damping force is compared with predicted one obtained from Bingham model of the shear and flow mode, respectively.
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