Filter Media Treatment – Fall 2011

Po-Hsun Lin

Abstract:

The post sedimentation addition of polyaluminum chloride (PACl) was investigated as a means to enhance particle removal efficiency in rapid sand filtration. The process modification was evaluated in laboratory studies and at the Cornell Water Filtration Plant (CWFP). PACl was continuously metered into CWFP filter influent to increase concentrations by 0.06 to 4.2 mg/L (as aluminum) during the filter-to-waste stage of the filter operation cycle to accelerate filter ripening. Lower influent PACl concentrations ranging from 0.056 to 0.43 mg Al/L were also continuously applied during filtration. In comparison to a control filter that received no PACl addition, the ripening time required decreased with PACl dose, and the incremental improvement in particle removal during filtration increased with PACl dose. The addition of 0.056 mg Al/L of PACl (the lowest concentration tested) significantly reduced initial filter ripening time at the CWFP from 10 hours to 2.5 hours, and effluent turbidity in the test filter over the 77 hour filter run was lower than the control filter by an average of 17%. Incremental head loss increase caused by the PACl feed was dose dependent and was negligible for the lowest dosage tested.

Foam Filtration, Summer 2012

Michelle Gostic, Sarah Levine, Leah Meyerholtz

Abstract

A reticulated polyurethane foam filtration system combined with coagulant dosing has proven capable of providing clean, low-turbidity water; however the necessary addition of coagulant combined with a non-conventional cleaning method makes the foam filtration system inefficient and not ideal to be used on a municipal scale. For this reason, research on foam filtration methods have been geared towards engineering a portable and effective filtration unit to provide clean water to devastated areas in emergency situations. There is a great demand for such technology as proven by the 1994 Rwanda Crisis. In this case, 85-90% of deaths in refugee camps were caused by diarrhea [Toole and Waldman; Doocy and Burnham]. Providing a low-cost, sustainable clean water source in emergency situations is the best way to prevent waterborne diseases and dehydration. The foam filtration team has worked towards designing an apparatus that will provide at least 15 liters of water per day per person, based on the UNHCR’s (United Nations High Commissioner for Refugees) recommendations for refugee situations [UNHCR]. The foam filter is small enough that it can be placed in the back of a pick up truck when needed and hooked up to the car’s engine to harvest electricity needed to power the filtration process. The current AguaClara foam filtration system utilizes a roughing and finishing filter to remove solid particles from influent water. Turbid water enters through the linear flow orifice meter (LFOM), which maintains a linear relationship between the water level and the flow rate of water through the system. Coagulant enters the LFOM in regulated doses to ensure consistent mixing of coagulant with influent water. The water flows through a 30 inch deep roughing filter, consisting of 30 ppi (pores per inch) foam, and then through a 15 inch deep finishing filter, consisting of 90 ppi foam. Before effluent water leaves the system, it is dosed with chlorine and exits the supercritical flow tube. Previous tests showed that head loss from the foam filters was negligible, but recent experimentation with an open system has proven otherwise. Due to the head loss and effluent turbidity standards, the foam filters need to be cleaned. A “plunger” method of cleaning has proven to be an efficient and easy way to clean the foam filters. A long pole with a porous disc attached to one end is used to compress the foam and release solid particles trapped in the 1 filters. This method is similar to squeezing out a dirty kitchen sponge. During the cleaning process, the foam must remain submerged in water to prevent the entrainment of air bubbles that would hinder filter performance. After plunging, the dirty water and released sediment flow out of exit valves located downstream of each filter. At the 2012 National Sustainable Design Expo in Washington D.C. the AguaClara team showed that the foam filter system is effective in removing particles from water at relatively high turbidities; however, data from these tests does not give concrete evidence of the filter’s performance in terms of realistic applications. At the expo, the turbidimeter was not properly calibrated, thus the data collected is not 100% accurate. Additionally, the filters were cleaned every 4 hours. Although this proved that the filters could return to their initial performance level after being cleaned via the plunger method, cleaning every 4 hours may be either too frequent or infrequent to maintain a high volume of treated water with acceptable effluent turbidity, in an emergency situation it is essential to maximize the volume of usable water while still maintaining quality standards. Effluent at the expo was dosed with clay and recycled so that the effluent became the influent. There is a possibility that coagulant built up in the filter columns, due to the recycle, improved performance beyond what it would have been in a more realistic experiment. As a new and relatively unexplored technology, there is much research to be done in the realm of foam filtration. Our current and future research will focus on providing extensive data as to the performance of the foam filtration system at different turbidities as well as identifying more efficient cleaning cycles. The World Health Organization included significantly reducing the number of “people without sustainable access to safe drinking-water and sanitation” in its list of 15 Millennium Development Goals [WHO]. Refining the foam filtration system has the potential to contribute to achieving this goal in addition to providing clean water to those who need it the most.

Foam Filtration, Spring 2012

Katie Edwards, Walker Grimshaw, Bradshaw Irish, Kelly McBride, Nadia Shebaro

Abstract

The Foam Filtration team developed a two-stage emergency water lter. The lter was presented at the 2012 National Sustainable Design Expo in Washington, D.C. as part of the P3 competition for sustainability. While at the expo, rough data was collected on the performance of the pilot scale lter as a proof of concept. The competition also involved submitting a grant proposal highlighting all past research on foam ltration and presenting a plan for future research and eventual implementation.

Foam Filtration, Fall 2011

Bradshaw Irish, Anna Lee, Rachel Philipson

December 12, 2011

Abstract

The Foam Filtration team is attempting to determine an application that utilizes polyurethane foam as a water filtration medium. Our work consists of running experimental trials which characterize the filtration properties of polyurethane foam. Polyurethane foam is not a conventional filtration medium, and through extensive work, we have proven that it can successfully produce effluent turbidities below US EPA standards. In addition to the characterization of foam as a filter medium, we have previously investigated the possibility of utilizing polyurethane foam at the point-of-use scale. A feasibility study determined that a polyurethane foam point-of-use unit would require the addition of coagulant and expensive moving parts. Therefore, the new focus of the Foam Filtration research team is on the design of an emergency water treatment system using polyurethane foam. This unit will consist of a roughing and finishing filter. Previous research characterized the performance of the finishing filter and current laboratory tests are focused on evaluating performance of the roughing filter.

Stacked Rapid Sand Filer Pilot Scale, 2012 Spring

Eva Johnson, Jordanna Kendrot, Bill Kuzara

Abstract:

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.

Stacked Rapid Sand Filter Full Scale, Spring 2012

Michelle Wang, Steph Lohberg, Chris Holmes

Introduction:

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.

Stacked Rapid Sand Filter Bench Scale, Spring 2012

Danhong Luo, Weiling Xu, Huifei Wu, Main Editor: Michael Adelman

Abstract:

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.

Low Flow Stacked Rapid Sand Filter , Summer 2012

Christian Compton, Alli Hill, Amanda Rodriguez, Samuel Taube

Abstract:

No abstract available for this research.

EStaRS, Fall 2012

Mihir Gupta, Kris LaPan, Rachel Proske

Abstract:

The use of filtration units for the treatment of drinking water is a common practice in engineering design. However these units are generally used for the treatment of large volumes of water. To improve upon this limitation, a stacked rapid sand filter was designed for low 􏰃ow rates. Work for the semester began with an existing filtration unit which did not contain sand, due to predicted failure from large head losses in filtration and backwash. The existing design was modeled in AutoCAD 2013 to provide an illustration of the system. Updates to this drawing were completed and will continue to be as fabrication phases occur. One of the primary tasks was to develop a mathematical model in MathCAD to calculate the flows and head losses throughout the system. The model was completed for filtration and backwash, and includes calculations for both cycles with and without sand present. Hydraulic testing was completed to determine the head losses in filtration and backwash, risk of sand transport through the backwash pipe, and 􏰃ow rates. These measurements and observations were compared with the mathematical model to determine its validity. According to head loss values obtained from the mathematical model, several changes were made to the filter prototype. Such fabrications included complete reconstruction of the backwash pipe, changing of valve types, and installation of NPT fittings and ball valves. Finally performance testing was completed to determine the effectiveness of the prototype in regards to decreasing effluent turbidity. Overall, it was determined that the filter prototype is highly effective at decreasing turbidity for several influent concentrations at the designed flow rate.

Foam Filtration - Spring 2013

Jenny Guan, Monica Kuroki, Lishan Zhu

Abstract:

Originally, the foam filtration system was designed to provide clean water to small-scale communities. The system was also designed to provide water in emergency situations such as a refugee camps. The system was ideally powered by gravity and the optimal filtration rate was made to be 3 L/min. For the Spring 2013 semester, the foam filtration team began fabricating a new system and recording the process of the new system. The previous filtration system was designed and shipped to Honduras in January 2013. The current design focuses on pieces readily acquired in-country. This allows feasible construction in Honduras and, potentially, other developing countries. Products such as 8020 steel, clear PVC piping and flexible tubing have been removed from the design because they cannot be easily found outside of the US. The foam filtration team this semester is also working on making the design more compact for easy transportation. Additionally, the foam filtration team designed a new compact stand of PVC piping to hold the filtration system. The team included a larger collection tank to allow for the incorporation of a linear dosing system.

Foam Filtration - Fall 2013

Skyler Erickson, Melissa Shinbein, Jeffrey Suen, Kadambari Suri

EStaRS - Spring 2015

Sarah Bolander, Skyler Erickson, Liza Johnson, Subhani Katugampala, Lilly Mendoza

Abstract:

The Spring 2015 EStaRS team built upon the work of previous semesters to optimize the original filter design as well as to develop alternative strategies to sections of the filtering process. Over the course of the semester, the team altered the process for attaching the filter cap in order to prevent future cases of blow­off, adjusted the system for controlling water level height during backwash, and ran tests on filtration efficiency. While at the beginning of the spring semester the team’s goals also included developing a method of testing and recognizing bed fluidization within the filter, looking into a method of running multiple filters in parallel, and setting parameters for backwash duration and frequency, the team changed directions and concerned itself with the implementation of a new filter injection system to combat the problems associated with using slotted pipes.

EStaRS - Fall 2015

Skyler Erikson, Lilly Mendoza, Natalie Mottl, Lishan Zhu

Abstract:

The Fall 2015 EStaRS team reworked the lab scale setup of the EStaRS filter to work without a large pool to preserve lab space. The team then finished the orifice inlet implementation that was begun in Spring 2015, and provided an operating procedure for both filtration and backwash to avoid trapping sand in the inlets during the transition. The biggest takeaway from the operating procedure is that orifices can be operated successfully as long as the backwash transition does not create a drastic pressure change. Slowly closing the gate valve on the backwash siphon provides a gradual change and does not trap sand in the inlets. This procedure was the result of numerous inlet cloggings, and thus the team also devised a method for unclogging inlets without disassembling the filter. The team also implemented a pressure sensor to track headloss accumulation through the filter bed in the entrance tank. This pressure sensor was used to measure a clean bed headloss which is very close to the design clean bed headloss.

Foam Filtration - Spring 2014

Kristin Chu, Skyler Erickson, Melissa Shinbein, Jeffrey Suen, Kadambari Suri

Abstract:

The Spring 2014 foam filtration team will focus on improving the water treatment system designed in Fall 2013 and incorporating the knowledge learned on the trip to Honduras in January, 2014. This includes: redesign- ing the cleaning techniques to improve efficiency in removing dirty water off of the top of the foam, investigating foam re-expansion in a drum with vertical sides, designing the LFOM, and implementing a coagulant doser. The goal for this semester is to design, build, and test a compact system that can be easily transported and eventually implemented in small communities. In order to achieve this long-term goal, the Foam Filtration team will need to investigate multiple design options and create an operational system in the AguaClara lab. The foam filter will then be tested in Honduras.

Foam Filtration - Summer 2014

Abby Brown, Ethan Keller, Skyler Erickson, Ji Young Kim

Abstract:

The Summer 2014 Foam Filtration team will continue to improve the water treatment system, aiming to send a complete filter design to Honduras in July 2014. The goal of the summer is to verify the safety of the foam filter itself and to improve the design of the filtration system for better performance, easy fabrication and transportation. The foam filter will be additionally tested in Honduras.

Foam Filtration - Fall 2014

Kristin Chu, Marlana Hinkley, Ethan Keller, Valerie Pietsch

Research report not available. Research presentation attached below.

StaRS Backwash, Fall 2014

Vicki Chou, Nick Farino, Chenhao Qi, Rui Zhang

Abstract

The goal of StaRS Backwash is to determine the sand grain sizes and distribution for the most efficient and effective backwash in the stacked rapid sand filters. The proper fluidization velocity for efficient backwash must first be determined. An expansion ratio of 1.3 is the current standard for the sand bed during fluidization. A sand size ratio below 1.5 is suggested for minimal segregation during backwash. The team ran experiments with sands sized by sieve combinations of 20­40 and 30­40 at different backwash velocities to test for segregation. Through the experiments, the team found that the 20­40 sized grains always segregated at all backwash velocities, but the 30­40 sand, which is under the 1.5 sand size ratio, did not segregate below backwash velocities of 15 mm/s. Current AguaClara plants use a backwash velocity of 11 mm/s, so using 30­40 sand would be a good option because it should not segregate according to the data collected.

StaRS Backwash Alternative, Fall 2014

Alberto Arnedo, Ainhoa Arribas Llona, Jorge Guevara

Abstract

The current slotted pipes being used in the backwash system of the AguaClara filtration plants have been clogging up with sand, thus posing a problem for the backwash system since the slotted pipes’s purpose is not being fulfilled. Given this issue, the Alternative Backwash without Slotted Pipes subteam will work to find an alternative pipe for the backwash system that will not clog up with sand at any point of backwash or filtration and will be easy to manufacture on site in Honduras and India given the resources available in each respective country. The team has successfully built a STaRS scale model to be used to accurately experiment with alternative pipes for both an inlet and an outlet valve. Through experimentation, it was found that the alternative tubes in the shape of a hollow rectangular prism cut in half lengthwise and placed with the interior facing down did not fill up with sand during the processes of filtration or backwash.Once the pump was turned off, however, the sand would settle underneath the outlet pipe. This led the team to two possible courses of action: the first being that the team could leave the pump running the water at a low flow rate and the second being that the team build a second alternative for the outlet pipe. Both actions would solve the issue of the sand clogging up, but the team pursued the second alternative. The new shape for the alternative was a hollow cylinder with wings that extended out tangentially from the top of the cylinder with a hole in the middle of the cylinder’s bottom. In experimentation, the new alternative outlet pipe worked well for the first trial, but filled up with sand in the subsequent trials. Through more experimentation with the current alternatives, or perhaps new alternatives, future subteams will work to find a solution that will consistently work without filling up with sand.

Fabrication - Fall 2014

Carl Talsma, Sara Sanz, Adrian Cobo

Abstract:

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.

Enclosed Stacked Rapid Sand Filter - Spring 2014

Dhaval Mehta, Ariel Seidner, Sarah Sinclair, Lishan Zhu

Abstract:

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