Performance of a novel vertical-flow settler: a comparative study.
By increasing particle concentration and G value (root-mean-square velocity gradient) to enhance flocculation, a novel vertical-flow settler was designed to increase sedimentation effectiveness, and to simultaneously improve operational stabilization. Due to the gradual decrease in upward flow-rate of raw water, a flocs blanket would form and suspend in the middle section of the settler, not at the bottom as in a conventional clarifier. Enough large flocs, resulted from flocculation or filtration, would continuously settle out of the flocs blanket, and simultaneously, the flocs in raw water or those forming above the blanket would ceaselessly enter the flocs blanket. As a result, the flocs concentration in the blanket could keep a dynamic balance. The hydrodynamic shear in the blanket was improved by flow separation, which was induced by the abrupt change in flow channel. Due to the floes blanket and improved hydrodynamic shear, flocculation would be enhanced, which was helpful for removing fine particles in raw water. A comparative study showed that the novel vertical-flow settler had a much better performance in the removal of the particles in raw water than a conventional one, when they treated kaolin suspensions of different concentrations (500, 100 and 50 mg/L, respectively) coagulated by polyaluminum chloride(PAC1) at the up-flow rates of I and 2 mm/s, respectively.
Evaluation Of Parameters Affecting Steady-State Floc Blanket Performance
A laboratory-scale reactor was used to simulate a water treatment process sequence of rapid mix, hydraulic flocculation, upflow clarification with a floc blanket, and lamellar sedimentation to accomplish removal of colloidal particles. This process sequence, followed by chlorination, has been employed to create affordable designs for water treatment in the Global South. This study focused on variables affecting performance of the floc blanket including: condition of hydraulic flocculation, raw water turbidity, coagulant dose, upflow velocity through the floc blanket, floc blanket height, and bulk density and solids concentration of the floc blanket. An upflow clarifier velocity between 90-110 m/day produced the best floc blanket performance for most influent turbidities studied. The results show that particle removal efficiency in lamellar sedimentation improved linearly with respect to floc blanket heights up to 45 cm. Improved performance is also correlated with increased hydraulic flocculator residence time and energy dissipation rate. At floc blanket heights above 45 cm, there is still improvement in performance for most cases, but improved performance and blanket height no longer follow a linear relationship. Lamellar sedimentation with a capture velocity of 10 m/day is a key component in improving clarifier performance when utilizing a floc blanket. Future studies are needed to determine mechanisms of particle removal in a floc blanket.
Frequency selective surface design for blinds applications
In this paper, the reconfigurable blind structure with frequency selective surfaces(FSS) for the building applications are presented. Frequency transmission characteristics for different angles of the proposed blind-FSSs are investigated and verified through simulation and measurement. The simulation results show that we can implement the reconfigurable blind-FSS for multiband wireless applications. To verify the proposed paper, two kinds of blind-FSSs, crossed dipole FSS and circular ring FSS are fabricated and measurements are performed for different angles. The proposed structure in this paper which is very simple, can be easily applied to any planar surface for wireless security applications at low cost.