Faecal coliform attachment to settleable suspended sediments in fresh surface waters: linear partition model validation and sediment concentration effects

Controlled experiments were conducted to examine the validity of the linear partition model for faecal coliform (FC) attachment to suspended sediments and assess the impact of sediment concentration on the attachment. Sediments were collected from a river in Beijing, China and the suspended particles <62 μm were separated out and mixed with FC suspensions. The experimental mass specific concentration of attached FC linearly increased with the free-floating FC concentration, with the partition coefficient for four different sediment concentrations ranging from 0.2286 to 0.2695 L/g. Actually, the results can be well described using a single partition coefficient of 0.2565 L/g. The rate of sediment particle surface covered by attached FC was in the range of 0.32 × 10−5–0.58 × 10−5, and the relatively low rate gave a possible explanation of the linear relationship. The experimental fraction of attached FC significantly increased with increasing sediment concentration, ranging from 7.5 to 54.2%, and this was well explained by the linear partition model. These results proved that the linear partition model was valid in describing FC attachment to suspended sediments in surface waters and the attached fraction was sediment concentration dependent, while the impact of suspended sediment concentration on the partition coefficient was insignificant.

Fluorescence Spectral Characteristics and Sorption Behaviors of Acenaphthene to Surface Sediment in Chongqing Section of Yangtze River

3-D Fluorescence Spectrometry analysis and sorption experiments of Acenaphthene (Acp), one of the polycyclic aromatic hydrocarbons (PAHs), were carried on in this paper. Under the experimental conditions, the optimized excitation/emission wavelength (λex/λem) was 280/320nm. The correlative coefficient of 0.998 and the relative standard deviation of 4.03%(n=5) could be obtained over the linear ranges of 0.025mg/L~1mg/L for the calibration curve. The sorption tests of Acp to surface sediment in Chongqing Section of the Yangtze River showed that the sorption isotherms were fitted with different types of model, including traditional linear partition model and Freundlich model. According to the fitted value of model, the sorption behaviors of Acp to the surface sediment was not affected by the single sorption mechanism but the combined action of linear partition process and surface sorption.

Optimum Synthesis of Multiloop Planar Mechanisms for the Generation of Paths and Rigid-Body Positions by the Linear Partition of Design Equations

The optimum synthesis of multiloop planar mechanisms for the generation of paths and rigid-body positions employing the linear partition of the design equations is presented. Design equations and their applications for the optimum synthesis of the three distinct types of the Stephenson’s six-bar mechanism for the generation of paths and rigid-body positions are presented. The optimum sets of dimensions of a mechanism are determined by minimizing the error in the loop-closure equation of the path dyad and of the loops of the mechanism. Design equations having nine to twelve unknown dimensions are presented. Industrial applications of the design equations are illustrated with design examples.