There are three variations of sedimentation tanks that the demo plant team can use. The purpose of these experiments were to find which sedimentation tank produced the lowest effluent turbidity when run at a number of flow rates. The preferre d tank will be used in the production of additional demo plants. The tanks are displayed below.
Christine Lauren Catudal, Matthew William Hurst
This experiment explored the impact of water supersaturated with respect to atmospheric pressure on floc blanket formation and performance. This experiment involved collaboration with the Floating Floc Research Team, who supplied the saturated water that served as the influent water to the process.
Zachary N. Romeo
Floc roll-up occurs in tube settlers when the torque caused by a differential in the velocity profile exceeds the force of gravity whereby particles fall back out into the sedimentation basin. The Plate Settler Spacing team hypothesized that holding the length to diameter ratio in tubes of different diameters constant at 20 would decrease the capture velocity's sensitivity to flow rate. Two diameters representing the extremes in lamella spacing (23.5 mm and 6.35 mm) were tested in this experiment. Each experiment was run with the tube settler at two different heights (1.3 cm and 2.7 cm) above the floc blanket-clear water interface.
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.
The Effect of Floc Roll-up on Clay-Aluminum Hydroxide Flocs
Matt Hurst, Monroe Weber-Shirk*, Tanya Cabrito, Cosme Somogyi, Michael Adelman, Zachary Romero, Richard Pampuro, Rachel Phillipson, Sarah Long, Colette Kopon, Ying Zhang, Ashleigh Sujin Choi, Adela Kuzmiakova, Jae Lim, Alexander Duncan, Christine Catudal, Elizabeth Tutunjian, Ling Cheung, Kelly Kress, Tiara Marshall, and Leonard W. Lion
Inclined plate and tube settlers are commonly used to create compact sedimentation tanks. Conventional design guidelines are based on obtaining a desired sedimentation design capture velocity. Theoretically, this capture velocity can still be achieved while greatly reducing conventional plate spacing or tube diameter. The greatest concern with small plate spacing is the danger of settling sludge being swept out with the finished water. This research presents the basis of this failure mechanism as high velocity gradients present at small tube settler diameters and small plate settler spacings.
Ruonan Zhang, Xiaocan Sun, Yizhao Du
Through lab research we seek to understand the different influence of coagulant type, capture velocity, coagulant dose and raw water turbidity on the performance of the plate settler in AguaClara plants. We are using a tube settler to simulate those plate settlers in the full-scale plants. Through various changes in operating conditions, we expect to determine the best parameters, and this is of great significance in real practice. After that, we are going to pick out some of the best conditions and repeat the experiments with natural organics in order to see how humic acids affect overall performance.
Dhaval Mehta, Hui Zhi, Surya Kumar
AguaClara is an engineering program based at Cornell University that develops sustainable water treatment technology with current applications in developing countries. In Honduras, one of the countries with AguaClara technologies, the treatment plant at San Nicolas experiences raw water with a temperature gradient of around 1°C/hr during warming and cooling portions of a day. These gradients are primarily caused due to the approximately 15km of piping that brings raw water to the plant, much of which is exposed to the sun. Agua Clara plants use sedimentation tanks with floc blankets and plate settlers. The temperature gradient during warming periods causes a circulation current to form in the vertical Gflow sedimentation tank, due to the effect of continually warmer water displacing colder water. This current in the tank at San Nicolas causes flocs to aggregate on one side of the tank and rise up to the top with the hotter, less dense water; hence the effluent water leaving the tank is not sufficiently clean. Our experiment is motivated by this problem, with the goal of studying the problem’s origins and providing initial research towards its solution
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.
Jillian Whiting, Tianyi Wang, Janak Shah
The goal of the milli-sedimentation team was to find and explore the boundaries between sedimentation and filtration which could be used to reduce the size and residence time of AguaClara plants. The technology was designed using coffee straws that are sized between the spacing of plate settlers (10 mm) and the porosity of filter material (0.1 mm). The size of the plant would be on the scale of a small town or village, less than 1000 residents, replacing what the foam filter did in El Carpintero. One of the biggest challenges for the semester after building the sedimentation-filtration system was attempting to clean the apparatus, as this determined the feasibility of the design.
