Tanya Suntikul Cabrito
Stepping from previous research with velocity gradients, this experiment seeks to uncouple their effects on tube settler performance deterioration from those of the capture velocity. In the team's last experiments (detailed in Exploring the Coupled Effects of Capture Velocity on Settler Performance), it was hypothesized that maintaining a constant length to diameter ratio in tube settlers would minimize the effects of the capture velocity on performance.
Tanya Cabrito, Jae Lim, Cosme Somogyi
The goal of the Plate Settler Spacing Team (PSS) is to study the lamellar sedimentation process in plate settlers and the efficiency of the removal of flocculated particles and establish improved guidelines for plate settler spacing. The traditional guidelines for plate settlers state that the spacing between plates cannot be less than 5 cm and little to no justification can be found for this. The team's results show that performance in accordance with the US drinking water standard of 0.3 NTU can be achieved with spacings smaller than 5 cm. Also, all but one of the experiments meet the World Health Organization standard of 5 NTU. For AguaClara plants, having smaller spacings between plate settlers allow the sedimentation tank to be shallower and therefore cheaper. Smaller spacings also allow for increased head loss across the plate settlers. This would help even out the distribution of flow in AC plants and allow the plate settler system to function at its design capture velocity of 0.12 mm/s throughout. The team had finished velocity gradient experiments with a clay aluminum hydroxide system; however, a recently discovered mistake in documentation caused the team to reassess the data collected this semester and more tube trials must be run. Due to this error, the team changed the capture velocity for the velocity gradient from 0.12 mm/s to 0.10 mm/s. The major tasks completed by the Fall 2010 PSS team are catching a documentation error that happened at the end of Spring 2010, studying the effects of high velocity gradients and floc rollup on plate settler performance, developing a macro that significantly facilitates data analysis and a plate settler dynamics model that may better shed light into processes governing plate settler performance.
Yiwen Ng, Anna Lee, Tiffany Tsang
Previously our team worked on designing a scaled down model of sedimentation tank in order to study floc blanket formation in 3D models. However, we decided that it would be more effective to continue the study with the existing 2D sedimentation tank. Using this tank our first objective was to determine the minimum angle of repose. We have hypothesized that for an insert angle below 60 degree that a floc blanket would not form. The slope of the insert would not be sufficient for the flocs to be transported to the jet, thus the flocs would accumulate on the incline. However, even when we decreased our angle of repose to 30 degrees, we were successful in forming the floc blanket.
Surya Kumar, Larry Ge
The sedimentation tanks at AguaClara sustainable drinking water treatment plants are performing well, but they can perform better. When floc settles it becomes sludge. If there is sludge buildup in a sedimentation tank, a host of problems follow: uneven water flow through the sedimentation tank, impaired performance, anaerobic digestion, and methane production. However, if a sedimentation tank can be designed to prevent any flocs from settling, then the drinking water treatment process will never have to be stopped, and the sedimentation tanks will never have to be cleaned. AguaClara is investigating the creation/use of a “Floc Probe” to better understand floc behavior and achieve this improved tank design. The research tool will be used to survey currently functioning sedimentation tanks in Honduras to identify where sludge is building up. Sonar has been found to be a potential solution. Sonar can detect substances of varying densities as well as record at what depth the substance was found. This technology can therefore distinguish between flocs and sludge, and can also recognize the amount of sludge buildup.
