Grantee Research Project Results
Final Report: AguaClara Stacked Rapid Sand Filtration – A Robust Filtration Process For Sustainable Drinking Water Infrastructure
EPA Grant Number: SU835307Title: AguaClara Stacked Rapid Sand Filtration – A Robust Filtration Process For Sustainable Drinking Water Infrastructure
Investigators: Weber-Shirk, Monroe , Lion, Leonard William , LaPan, Kristopher , Rausch, Heidi
Institution: Cornell University
EPA Project Officer: Hahn, Intaek
Phase: I
Project Period: August 15, 2012 through August 14, 2013
Project Amount: $15,000
RFA: P3 Awards: A National Student Design Competition for Sustainability Focusing on People, Prosperity and the Planet (2012) RFA Text | Recipients Lists
Research Category: Pollution Prevention/Sustainable Development , P3 Challenge Area - Safe and Sustainable Water Resources , P3 Awards , Sustainable and Healthy Communities
Objective:
The objective of the Phase I research was to develop a low-flow stacked rapid sand filter (SRSF), suitable for providing safe drinking water to small rural communities (1000 individuals or less) that are common in the developing world. The low-flow SRSF is an adaption of the innovative filter design created by Cornell University’s AguaClara program. The SRSF is specifically to be constructed and maintained within the developing world. The fully-hydraulic process does not require electricity, and therefore it can operate without the necessity of a reliable electric grid.
The SRSF makes use of multiple layers of sand stacked on top of one another which operate in parallel during filtration and in series for backwash. The filter contains four inlet pipes and three outlets, creating six sand layers. During filtration, influent water flows in through all four inlet pipes, enters the separate layers of the sand bed through slots in the pipes, and flows out through the outlets. During backwash, the water only flows through the bottom inlet pipe, creating a six-fold increase in velocity sufficient to fluidize the filter media with no change in the fluid flow. As the increase in velocity is achieved hydraulically, there is no need for pumps or other expensive equipment to assist in fluidization of the sand bed. A full scale SRSF designed by the AguaClara program has been constructed in the city of Támara, Honduras and has been successfully operating for over a year delivering filtered water that meets US EPA drinking water standards for turbidity. The design of this full-scale unit is suitable for moderate community sizes greater than 1000 individuals, and the challenge of the EPA Phase I project was to scale down the design to function at the lower flows needed for smaller communities.
Scaling down the SRSF presented significant design challenges. The need for maintenance and assembly required that internal human access be retained within smaller pipe dimensions. New methods had to be devised for connecting different sized piping and leak free through-wall connections were needed. To constrain the size of the low-flow unit, a removable cap was needed to retain the filter sand during backwash. The presence of the cap creates both positive and negative pressures within the unit at different stages of operation and required seal designs that were water and air tight.
Beyond creation of the SRSF design suitable for a different scale, the Phase I goals were to construct a prototype unit and to perform initial laboratory tests of the hydraulic performance and turbidity removal. Initial field tests were also performed in Honduras on the prototype.
Teams working on the AguaClara project are comprised of students ranging from freshmen to PhD students from many different major areas of study. Student work takes place in the context of the network of international AguaClara partners and the communities that use AguaClara technologies. These ongoing relationships form the foundation for the proposed Phase II field testing.
Summary/Accomplishments (Outputs/Outcomes):
Figure 1. Cornell students in the AguaClara program make initial field tests of a prototype low flow SRSF in Honduras.
The main AguaClara team activity for summer and fall of 2012 was to modify the SRSF to operate with a low flow rate of approximately 0.8 L/s, achieve a high turbidity removal efficiency, and minimize filtration and backwash energy loss. The construction of the low-flow SRSF was completed during the summer of 2012. Laboratory tests with clay suspensions of varying concentrations were input into the prototype while simultaneously measuring and recording the influent and effluent turbidity. In line turbidity meters were installed at the inlet and outlet channels and the data was continuously recorded throughout the test. A turbidity removal efficiency of 97.5% was obtained at 30 minutes of operation for an input turbidity of 5 NTU. The removal efficiency reached a maximum of 99.2% for an input turbidity of 20 NTU resulting in an effluent concentration of 0.17 NTU.
The prototype for the low-flow SRSF device was transported to Honduras in January 2013 (see Figure 1), where field testing informed subsequent design modifications. The iterative feedback sequence of design - test - modify is a core component of the AguaClara philosophy and has led to continuing improvement of treatment systems created through the program.
Conclusions:
The first low-flow SRSF was successfully designed and tested at the bench scale in the Cornell Environmental Engineering Laboratories. Laboratory observation indicated particle removal from water sufficient to meet US EPA drinking water standards and successful backwashing process. A prototype filter was constructed and tested in Honduras. The low-flow device can operate at flow rates as low as 0.8 liters per second and extends the SRSF technology for use in smaller communities that otherwise lack access to safe drinking water.
Phase I results identified areas where design modifications that would benefit the prototype unit. These modifications guide the Phase II activities, which are expected to culminate in deployment of the low-flow SRSF in Honduras with ensuing evaluation of performance in the field.
Journal Articles on this Report : 2 Displayed | Download in RIS Format
Other project views: | All 5 publications | 2 publications in selected types | All 2 journal articles |
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Adelman MJ, Weber-Shirk ML, Cordero AN, Coffey SL, Maher WJ, Guelig D, Will JC, Stodter SC, Hurst MW, Lion LW. Stacked filters: a novel approach to rapid sand filtration. Journal of Environmental Engineering 2012;138(10):999-1008. |
SU835307 (Final) |
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Adelman MJ, Weber-Shirk ML, Will JC, Cordero AN, Maher W, Lion LW. Novel Fluidic Control System for Stacked Rapid Sand Filters. Journal of Environmental Engineering 2013;139(7):939-946. |
SU835307 (Final) |
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Supplemental Keywords:
Sustainable infrastructure, drinking water, municipal water, rapid- sand filtrationRelevant Websites:
AgusClara Wiki- Stacked Rapid Sand Filtration Exit
P3 Phase II:
Stacked Rapid Sand Filtration - A Robust Filtration Process for Sustainable Drinking Water InfrastructureThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.