Rachel Beth Phillipson
At the plants in Honduras, the head loss through the lamella plates is much less than the head loss from the water flowing through the inlet ports. Because of this, the flow throughout the plate settlers is uniformly distributed. To even out these flows, a geotextile foam is placed on top of the plate settler to create the same head loss through the lamella plates and the water flowing through the inlet ports.
Eva Johnson, Jordanna Kendrot, Bill Kuzara
The stacked rapid sand filter has been proven to be an alternative to traditional rapid sand filtration systems, and their efficiency makes them an appropriate component in gravity powered municipal-scale water treatment facilities. In this study, a pilot-scale apparatus has been create as a model of the hydraulic controls throughout a full-scale stacked rapid sand filter system. After installation and field testing at Tamara, it is vital for the backwash segment of filter operation to be controlled for a more efficient use of the system. The purpose of the current experimentation and lab procedures are to determine the optimal backwash cycle time necessary for the filter to remove as much particulate matter as physically possible with a short filter-to-waste cycle, thus reducing the overall rinse cycle time. Further research will be needed in determining how to lessen bubble formation, be it in the inlet box or filter itself, and in measuring the change in flow distribution throughout filtration and backwash. A four-layer rapid sand filter was created to test filter efficiency versus monetary compensation from using less sand in the filter box, but was shown to have less than optimum particulate matter removal when compared to the tested six-layer.
Michelle Wang, Steph Lohberg, Chris Holmes
The purpose of this report is to effectively summarize the progress that has been made to fabrication methods for the stacked rapid sand filtration system over the course of the semester. The stacked rapid sand filtration system is a new technology developed by AguaClara. It has many advantages over traditional sand filtration systems. First, it uses less water to backwash, because the filter layers are stacked. The filtration system also uses the same water for to backwash all the filter layers, producing a concentrated waste stream and reducing backwash time. Furthermore, this technology is much easier to operate than conventional rapid sand filters. It fits all the criteria of AguaClara technology, as the normal filtration and backwash cycles are driven by gravity. Materials are relatively cheap and widely available in Honduras. Finally, this filtration system has been proven to lower the effluent turbidity sufficiently, producing treated water below the EPA standard of 0.3 NTU and often even less than 0.01 NTU. The first field scale design of this filtration system was recently implemented at the AguaClara plant in Tamara. There have been several previously unforeseen issues that have arisen. In Tamara, in order to fit the slotted pipes into the trunk line and end lines, compression slots were cut into the slotted pipes. However, this allowed sand to leak into the inlet and outlet plumbing. Sand leakage is a serious issue because it increases head loss in the filter, reduces the length of the filter cycles, lowers the efficiency of the filter, and makes it harder to backwash. One of our main goals for this semester was to find a way to make a sand-tight connection between the slotted pipes and the trunk line and end lines. Another challenge we are facing is to find a new construction method so that the manifold can be built outside of the filter box. After the manifold is completely assembled, it will be lowered into the filter box as a unit. A key part to our progress this semester is the steady feedback from the team in Honduras at the Tamara site. Changes that we make this semester will aid in the maintenance of the Tamara filter and the design and implementation of the next stacked rapid sand filtration system in San Nicolas.
Danhong Luo, Weiling Xu, Huifei Wu, Main Editor: Michael Adelman
Stacked rapid sand filltration (SRSF) is a novel technology for AguaClara water treatment plants. Our team goal is to improve the performance of the SRSF by studying fundamental questions such as the self-healing nature of ow distribution among layers and the effect of upstream energy dissipation rate on performance. In the self-healing test, we found that it is hard to let the sand bed itself control what the flow distribution will be, and that surface removal dominated in the filtration process. The depth filter test reveals that surface removal dominated in the self-healing test, and flow distribution improved when surface removal effects were eliminated. For the energy dissipation rate test, we assume the filter performance would be improved with the increasing energy dissipation rate, while current experiments have not show the result. Therefore, further testing should be addressed in the energy dissipation rate study.
Christian Compton, Alli Hill, Amanda Rodriguez, Samuel Taube
Matt Cimini, Alex King, Tanvi Naidu
The objective for the Filter and Treatment Train Flow Control team (FTTFC team) this semester was to design and construct a weir module that would allow the plant operator to easily redirect sucient flow for filter backwash without shutting o↵ other filters’ flow. The goal of the design was to be easily constructible, easy to operate, strong enough to withstand water pressure and require no calculations for plant use. The team designed several removable weir options and ultimately chose a hinged design. The design is similar to a dog door that will be shut during normal flow and open during backwash. The model was fabricated and tested under conditions simulating a 20 L/s plant. The weir module was strong enough to withstand the flow, was easy to construct and was simple to open and close even with the water pressure against it and therefore was a success. There was some significant leakage around the weir flap. Therefore, construction and design should focus on recommendations for watertightness of the flap if this design is to be used in an AguaClara plant in the future.
Alexandra Cheng, Apoorv Gupta
The AguaClara water treatment plant in San Nicolas was inaugurated on April 5, 2014, and has successfully started operation. However, a major problem that has become apparent is the heating of raw water during the day from the source to the plant entrance tank. Raw water travels 4.5 km through a steel pipeline exposed to sunlight which has been identified as the likely cause for the temperature increase. Since the plant is hydraulic and gravity-powered, the temperature of the influent water affects its properties and behavior in the various stages of the AguaClara treatment system, particularly in the sedimentation tank. While the stacked rapid sand liter has been able to keep effluent turbidities low enough to be deemed acceptable, the resulting required amount of backwash places excess stress on the system; therefore, it is imperative to seek a method to maintain a relatively low raw water influent temperature to ensure plant success in producing potable water.
Carl Talsma, Sara Sanz, Adrian Cobo
Make a hydraulic working scale model of the SRSF weir system for two filters to demonstrate how the weir system is used to set the flow to the filter during backwash. The hydraulics of this system are sufficiently complicated that explaining how it works is difficult and thus we need a working model for demonstration.
No final report was available for this team for this semester. The final presentation is linked below.
Dhaval Mehta, Ariel Seidner, Sarah Sinclair, Lishan Zhu
The Low Flow Stacked Rapid Sand Filter (LFSRSF) is a scaled-down version of the AguaClara Stacked Rapid Sand Filter (SRSF). Similar in theory of operation to the SRSF, the LFSRSF is optimized to treat smaller flow rates of 0.8 L/s. The current LFSRSF design in India uses multiple valves to switch from filtration to backwash; the LFSRSF research subteam at Cornell seeks to reduce the number of valves by designing a filter that uses hydraulic controls. In detailing the teams work this semester, this report seeks to accomplish three main goals: to document the design process for such a filter, to document the fabrication process to facilitate easy technology-transfer to India, and to document filter performance as tested to date.
This semester, the team calculated appropriate design specifications for slotted manifold, trunks, plumbing systems and sand for the filter, as well as created a unique flexible-tubing derived sand drain. The team completed all fabrication, and also set up a water-recycle and leak containment system to support testing, as well as a pressure sensor array to test ow-distribution between sand layers. The team then solved multiple water- and air-leak issues. Ultimately, the team was successful in ensuring that the LFSRSF backwashes easily, efficiently and whenever an operator may so desire.
Teams working on the project further must tackle three major issues: the current filter cannot handle backwash flow rates greater than around 0.6 L/s, its entrance and exit tanks need to be raised, and the filter also faces significant challenges of larger-than-expected head loss during backwash. Once these issues are solved, the hydraulically-controlled LFSRSF shall be truly ready to be deployed in the field
Lotta Van Leeuwen, Tianchen Yu, Caroline Caglioni
Abstract unavailable for this team for this semester.
Please note, the final report is not available for this team for this semester and the Final Presentation is linked instead.
Marlana Hinkley, Alena Hutchinson, Ethan Keller, Alicia Peters
The primary goal of foam filtration is to design a low cost, locally sourced, easy to operate water filtration system. Throughout the semester, backwash cleaning efficiency experiments were performed on the small-scale filter, designed in Fall 2014 to hydraulically model the full scale filter implemented in El Carpintero. The objective of these experiments was to determine an empirical relationship between backwash pore velocity and the percent mass removal of the particles from the foam during the cleaning cycle. Experimentation with different pore sizes revealed a new mechanism for filtration: the foam acts as a sedimentation tank, providing a large surface area for the flocs to settle. This is contrary to the initial hypothesis that coagulant-covered flocs stuck to the inside of the pore walls, and that a large shear force would be required to remove the flocs during backwash. Evidently, there is still much to be understood with regards to the mechanisms behind filtration and backwash.
Apart from work in the laboratory, the team continues to analyze data collected from experiments performed on the full-scale filter in El Carpintero by AguaClara engineer, Walker Grimshaw, to understand the discrepancies between performance in the laboratory and in the field.
Much of the semester was spent preparing for the EPA P3 Conference held on April 10th and 11th in Washington, DC. The team fabricated a small scale model of the technology, prepared a technical report, and created a poster display for the competition, and received an Honorable Mention for its efforts in creating an “Off-Grid Solution to Drinking Water Treatment.”
Isha Chaknalwar, Theresa Chu, Michelle Lee
Modeling the physics of particle capture in stacked rapid sand filters allows for greater understanding and further innovation in filtration. A two-layer sand filter will be built to measure filtration performance parameters of effluent turbidity, head loss, and time until turbidity breakthrough or excessively high head loss. Sand filtration should be effective in removing small flocs, so flocculated influent water with coagulant and clay will enter the filter to simulate filtration and clogging.
Theresa Chu, Nick Coyle, Alexandra Schwab
The Stacked Rapid Sand Filter Theory team designed and built an apparatus to induce clogging and test the head loss across a slotted pipe, which allows the water to flow directly into the filter without sand leaving the filter. Experiments were run with high turbidity and coagulant doses to clog the slotted pipe and determine which influent conditions led to clogging and high head loss. Slotted pipes as an injection system for the stacked rapid sand filters have proven to be problematic due to clogging. Results show that floc build up of coagulant clay increased head loss and clogged the slots.
Anna Doyle, Juan Guzman, Lilly Mendoza, Felix Yang
The Low Flow Stacked Rapid Sand Filter (LFSRSF) team was originally tasked with building a small, stan-alone sand filter to be implemented in communities in India. This semester the Enclosed Stacked Rapid Sand Filtration (EStaRS) team fabricated a new filter based on the design the Fall 2016 team created. The new design modifies the original LFSRSF; the filter column itself is shorter, the manifolds are sized differently, and the entrance and exit plumbing is now rigid PVC instead of flexible PVC. Next semester, the new EStaRS filter will be connected to the 1 L/s plant that has been built in the lab.
Mengqi Jiang, Subhani Katugampala
The construction of Open Stacked Rapid Sand Filters, or OStaRS, has been determined to be a difficult and labor-intensive process. the absence of a uniform installation procedure and proper construction methods leads to the overall inefficiency of the OStaRS assembly process. The Spring 2016 OStaRS Fabrication Sub-Team was tasked with developing three design modifications to ease with installation, which include a spacer system to be installed between filter modules, a movable platform for operators to stand on during assembly, and a holder system to fixate the dead end of the filter trunk line. The team has designed and fabricated the spacer and the platform systems. These designed were successfully stress tested, approved for field implementation, and are currently set for installation in one AguaClara treatment plant.
Natalie Mottl, Michelle Bowen, Lilly Mendoza, Erica Marroquin
Manometer research & head loss modeling for greater efficiency and ease of use in Honduras and India.
No research report was available for this team for this semester. The final presentation is linked instead
Susan McGrattan, Victoria Zhang, Elizabeth Johnson, Mikel Aurteneche
The EStaRS team’s goals for this semester were to design a new EStaRS filter that was compatible with the recently built 1 L/s plant. The 1 L/s plant’s sedimentation exit elevation provided a height constraint of 6 feet and required a scaled-down version of the existing EStaRS filter. The team first worked to gain a complete understanding of the EStaRS filter design and operation using experiences and observations recorded by previous teams. MathCAS calculations from the AguaClara design server were adjusted for the new design and AutoCAD drawings were created to provide a completed design that was ready for fabrication.
Barbara Oramah, Lainey Reed, Emily Spiek
Stacked Rapid Sand Filtration is the last stage in an AguaClara treatment plant. The filters are used to further reduce the turbidity of water to meet EPA standards of 0.3 NTU or less. This semester, the Stacked Rapid Sand (StaRS) Filter Theory team constructed 3 StaRS filters with sand of varying sizes. These filters will be used in future experiments to analyze how specific parameters, including sand grain size and coagulant dosage, affect filter performance. The StaRS Filter Theory team has spent the semester compiling a manual so that future teams can run experiments and reconstruct experimental filters if necessary.
