Grantee Research Project Results
2014 Progress Report: Stacked Rapid Sand Filtration - A Robust Filtration Process for Sustainable Drinking Water Infrastructure
EPA Grant Number: SU835544Title: Stacked Rapid Sand Filtration - A Robust Filtration Process for Sustainable Drinking Water Infrastructure
Investigators: Weber-Shirk, Monroe , Lion, Leonard William , Chou, Vicki , Farino, Nick , Qi, Chenchao , Zhang, Rui
Current Investigators: Weber-Shirk, Monroe , Lion, Leonard William
Institution: Cornell University
EPA Project Officer: Hahn, Intaek
Phase: II
Project Period: November 15, 2013 through November 14, 2015
Project Period Covered by this Report: November 15, 2013 through November 14,2014
Project Amount: $90,000
RFA: P3 Awards: A National Student Design Competition for Sustainability Focusing on People, Prosperity and the Planet - Phase 2 (2013) Recipients Lists
Research Category: Pollution Prevention/Sustainable Development , P3 Awards , P3 Challenge Area - Safe and Sustainable Water Resources , Sustainable and Healthy Communities
Objective:
The ultimate goal of the EStaRS (Enclosed Stacked Rapid Sand) Filter team was to develop an appropriate configuration for the stacked rapid sand filter system that could be implemented to treat groundwater in India. The stacked rapid sand filter is an excellent choice for treating water near the city of Ranchi, India, as the primary water source there is groundwater. The low turbidity of groundwater means that the full AguaClara treatment process is not required and filtration with dosing will suffice. After testing the current apparatus, the goal was to improve the design so that modular EStaRS filters can be run in parallel efficiently and sand bed fluidization can be detected. This team set up a system to allow for extended backwash times, proposed a weir design to run multiple EStaRS Filters in parallel, and set up a manometer system to analyze bed fluidization during backwash.
Progress Summary:
e goal of the 2014 Fall EStaRS team was to develop and test a fully functioning enclosed stacked rapid sand filter that can be utilized in countries such as India where the source of water is groundwater and the full AguaClara process is therefore not necessary.
The filter apparatus built by the former LFSRSF (Low Flow Stacked Rapid Sand Filter) team was used throughout this semester’s research. The design of the filter was improved by setting up an organized way to test the efficiency of the filter, creating a backwash flow storage system, designing a model for running filters in parallel, analyzing the pressure on the filter cap, and developing a method to determine if the sand bed is fluidizing sufficiently.
This semester’s work sheds light on several different aspects of the filter design. Results from the backwash efficiency tests show that it consistently takes about 10 minutes in filtration before the filter clogs (at which point the filter efficiency drops below a pC* value of 2), demonstrating that backwashing between filter periods is consistently effective. Development of the weir design generated a new way of potentially running EStaRS filters in parallel. Construction and analysis of a manometer attached to the filter gave a potentially effective way of measuring sand bed fluidization.
Future Activities:
After setting up a backwash storage system, testing the EStaRS system in filtration and backwash mode, and observing several trial runs, the team’s backwash process has proven successful at producing consistent run times during subsequent forward filtrations. To further observe fluidization effectiveness during backwash, the team implemented a grid of manometers on the length of the filter sand bed that have confirmed the theoretical flow of water between sand bed layers. Although the team has been unable to reliably quantify to what degree the backwash system was fluidizing the sand bed (due to air bubble interference), the manometer system could be used in the future to analyze the effectiveness of the backwash. Finally, a rough draft of the weir system designed to allow for multiple filters in parallel has been sent to Maysoon in India, and dialogue about the implementation of this weir system should be continued.
Now that the filter system is running smoothly in both forward filtration and backwash (as well as smoothly transitioning from one to the other), future EStaRS teams should continue to repeat runs of the filter at a high turbidity to better determine the necessary amount of backwash time, while keeping the backwash intensity constant. This will enable them to run the filter in forward filtration mode for equal periods between backwashes without losing filtering capacity. In addition, future teams should conduct further mass balance tests to determine the inflow and outflow of floc mass through the filter column as well to obtain a reliable pC* number to analyze backwash efficiency. Using this mass balance and backwash efficiency, the necessary backwash frequency could be determined by setting limits on the allowable mass of floc in the filter at any given time and calculating the time over which the mass of floc accumulates in the filter column to the point of exceeding the set limit.
With the general concept of the new weir system fairly set, the next team should dedicate time to calculating the proper dimensions and spacing of the pipe and orifices. Once the calculations have been made, the next step will be to fabricate a set of weir pipes so that their functionality can be tested; the weirs must channel the right amount of flow individually and also work properly when being run in parallel.
The decision of whether each filter will have its own entrance tank or whether there will be a single large entrance tank distributing flow to each filter is yet to be made. In order to make more definitive designs for the weirs, the next team must communicate further with the group currently in India in order to decide what design is preferred. For example, if the filters are to have separate entrance tanks, the team will also need to design a way to adjust entrance tank heights between filters.
More calculations must be made to better understand the situation in which the filter column cap blows off, as well as to better understand how to prevent the problem. After the current cap design is analyzed for its capacity, a design for a cap that can withstand the calculated force from pressure in the column must be established. This work however, is less crucial to the overall goals of the team, and these calculations and potential fabrication should be considered if there is sufficient time.
While manometers were installed to analyze bed fluidization, they were unable to be used as a means of determining bed fluidization. This could be a simple and effective method if the issue of air bubbles was able to be resolved. Future teams should work on this, as well as more rigorously investigating the exact difference in water levels between manometers that should be observed to correlate to the desired 30% bed expansion. In the future it may also be interesting to make the more permanent addition of windows into the filter column to directly assess whether the sand bed is fluidizing. Windows may provide insight into the possibility of dead zones in the filter where sections of the sand bed aren’t fluidizing, as well as into the potential for shear along the filter walls causing uneven flow distributions through the filter.
Journal Articles on this Report : 2 Displayed | Download in RIS Format
| Other project views: | All 2 publications | 2 publications in selected types | All 2 journal articles |
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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. |
SU835544 (2014) SU835544 (Final) SU835307 (Final) |
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Adelman MJ, Hurst MW, Weber-Shirk ML, Cabrito TS, Somogyi C, Lion LW. Floc roll-up and its implications for the spacing of inclined settling devices. Environmental Engineering Science 2013;30(6):302-310. |
SU835544 (2014) SU835544 (Final) |
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Supplemental Keywords:
Sustainable infrastructure, municipal drinking water, resilient infrastructure, open sourceProgress and Final Reports:
Original AbstractP3 Phase I:
AguaClara Stacked Rapid Sand Filtration – A Robust Filtration Process For Sustainable Drinking Water Infrastructure | Final ReportThe 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.