Grantee Research Project Results
Final Report: AguaClara: Clean Water for Small Communities
EPA Grant Number: SU833179Title: AguaClara: Clean Water for Small Communities
Investigators: Weber-Shirk, Monroe , Bucher, Peter Von , Diminich, Alissa , Labelle, Amanda , Symonds, Amelia , Smith, Brianne , Serna, Carol , Yoo, Caroline , Scott, Cherish , Menendez, Daniel , Railsback, David , Foster, Earl , Leonard, Grace , Ou, Guojian , Tse, Ian , Erickson, John , Warner, Jordan , Capurso, Julia , Mahulikar, Kavita , Chu, Mandy , Wrolstad, Melissa , Stahl, Nikolaus , Walter, Ryan , Schwetschenau, Sara , Allen, Sara , Morey, Sara , Hiong, Sarah , Long, Sarah , Jordan, Steven , Sharabi, Tamar , Quesada, Tania , Kitirattragarn, Vincent , Tajani, Zaheer
Institution: Cornell University
EPA Project Officer: Page, Angela
Phase: I
Project Period: August 31, 2006 through August 31, 2007
Project Amount: $10,000
RFA: P3 Awards: A National Student Design Competition for Sustainability Focusing on People, Prosperity and the Planet (2006) RFA Text | Recipients Lists
Research Category: Nanotechnology , P3 Challenge Area - Safe and Sustainable Water Resources , Pollution Prevention/Sustainable Development , P3 Awards , Sustainable and Healthy Communities
Objective:
The project goal is to produce sustainable technology for the treatment of drinking water in small communities in Honduras and beyond. The resources, talent, time, and enthusiasm of students and faculty at Cornell are being utilized to develop an integrated set of processes that can economically treat turbid sources to produce potable water. We aim for technology transfer, that is, we are conducting research and developing designs for water treatment plants that can be customized, scaled, constructed, and operated in Honduras by Hondurans. The designs we develop must be simple, inexpensive, reliable, and able to be built and maintained with local materials in Honduras using local skills and knowledge. Rural Hondurans lack financial resources, reliable electric power and have weak logistical support for mechanical repair; thus, sustainable treatment plants must operate by gravity without the use of electricity or pumps.
Summary/Accomplishments (Outputs/Outcomes):
We have been taking a holistic system view of the water supply systems in the context of small communities in the Global South. Developing a water treatment system that is sustainable will require creating a whole set of technologies, the support infrastructure, and institutional and human capacity. We are conducting research on both sociological as well as engineered components that we have determined to be critical for production of safe drinking water and we are creating tools and programs to facilitate knowledge transfer that will be essential for technology adoption, adaptation, and dissemination.
Most small communities in Honduras (population less than about 50,000) are currently using hypochlorinators as the sole process to treat their water and most of the hypochlorinators that we have seen in Honduras are not in use. The drip hypochlorinators in use are a standard device that does not provide a consistent chlorine dose because of a poor hydraulic design and because calcium carbonate scaling causes valves to clog. AHJASA (association of Honduran Water Boards) has introduced tablet chlorinators, but supply and distribution of the tablets is a major challenge and there is some question about how well tablet-based systems control the chlorine dose. Some communities have abandoned the tablet feeders because the tablets are more expensive than calcium hypochlorite. Thus, research into alternative methods of controlling the chlorine dose using granular calcium hypochlorite is one of our research tasks.
Chlorination for the destruction of pathogenic organisms is not effective with waters having high turbidity (LeChevallier, Evans and Seidler (1981)). In addition, no one enjoys drinking water that is thick with sediment. Our strategy to address the turbidity problem is to add unit processes for particle removal to treatment systems prior to chlorination. We have explored the available technologies and have concluded that flocculation and sedimentation offer the best prospects for a sustainable solution. Flocculation works by the addition of a chemical coagulant (aluminum sulfate) to the turbid water. This chemical reacts with the particles in the water making them stick together and thereby increasing their sedimentation velocity. Coagulated particles can then settle out in a sedimentation tank. We are developing reliable, low maintenance, flocculation systems and plan to compare sedimentation tank designs. A requirement for all these systems is that they be gravity driven, and operate without the need for pumps.
We are not including filtration in the treatment plants because operation of rapid sand filters requires significantly more supervision, technical expertise, and usually require pumps for backwash. Filtration may be added by some of the larger communities as an additional refinement to their water treatment system, but we do not think that the current designs of rapid sand filters are sustainable in the Global South for small communities. Use of slow sand filters is potentially a viable alternative to rapid sand filters and we have ongoing NSF-funded research to develop systems that can reliably function under the technological constraints of rural communities.
During the past year we have made significant advances in our ability to conduct fully automated parametric testing using process control software. We are beginning to characterize the fundamental parameters that control flocculation using a laboratory scale tube flocculator with the goal of developing solid guidelines for designing full scale hydraulic flocculators that will consistently produce high quality finished water. We have invented a low cost mechanical alum dose test apparatus that will replace the need for electric jar test apparatus in water treatment plants. Last year we developed the rolling bottle test protocol and this year we developed a method to ensure that all of the samples are treated identically by placing the bottles in a spinning bucket. We have developed new fabrication techniques for assembling plate settlers and hydraulic flocculator baffles that we will be implementing in Honduras in the coming weeks. The plate settlers and baffles are built using materials that are available in Honduran hardware stores. We also have installed the first gravity-driven dosing device for a hypochlorinator capable of delivering a calibrated dose. We had not intended to introduce this technology this soon, but we needed a chlorinator for the water treatment plant we built in Ojojona, Honduras and the complete lack of alternatives forced us to try the system we had developed for dosing aluminum sulfate. The chlorinator is already working better than the standard designs used in Honduras. We also built a 100 liter/minute hydraulic flocculator that we are installing inside the Cornell University Water Filtration Plant with the goal of being able to test alternate hydraulic flocculator designs. We will also use the full scale flocculator to confirm our ability to scale the results form the laboratory scale tube flocculator.
Conclusions:
The AguaClara project team has identified the need for a well designed municipal water treatment plant for small communities. We recognize that to obtain a sustainable solution we must address all aspects of the technology as well as the interactions of the technology with society. We have designed and built a second water treatment plant in Honduras working with our partner organization, Agua Para el Pueblo (APP), that does not require electricity and that is simple to operate and maintain. We have developed simple modular designs for building plate settlers and hydraulic flocculators using commonly available Honduran building materials. We have developed chemical feed systems that can be easily calibrated to deliver a desired flow without the use of electricity.
We have identified the need for research to optimize hydraulic flocculation and have recognized that optimization will require an extensive set of parametric experiments. We have concluded that the paucity of design guidance for flocculators is due to the difficulty of conducting the experiments necessary to fully characterize the requirements for efficient flocculation. Over the past decade we have developed automated test capabilities at Cornell University that integrate process control, data acquisition, and the ability to conduct a set of experiments complete with controls and replicates. We have begun using this test capability to characterize optimal shear levels in flocculators.
The AguaClara project is serving as a powerful recruitment tool for both undergraduate and graduate students. The students know that the design work and research that they are doing is already making a difference and has the potential to revolutionize water treatment in the Global South. Our project teams have become incubators for learning and knowledge generation where students learn from doing and learn from each other and from “experts”. More senior members of the teams are able to practice teaching and junior members of the team get a rich experience with learning in a team environment.
The AguaClara project also prepares students for the grand challenge of maintaining the environmental infrastructure that society requires. The skills that they are learning will be equally applicable in the industrialized Global North where aging infrastructure will need to be refurbished and replaced in the coming decades. And we are training students to tackle environmental engineering challenges in a rich context where they can experience the complex interplay between science, technology, culture, and institutions.
Proposed Phase II Objectives and Strategies:
Our primary objective for the next two years is to further refine the AguaClara technology so that we can begin to ramp up the dissemination of the water treatment plants in the Global South. We will take on the challenge with a three pronged approach. In Ojojona, Honduras we will compare the performance of vertical and horizontal flow hydraulic flocculators. In the AguaClara laboratory at Cornell we will conduct parametric tests in the well characterized shear environment of a tube flocculator to determine the optimal distribution of shear and the optimal combination of velocity gradient and residence time. At the Cornell University Water Filtration Plant we will compare the performance of alternative configurations of a 100 L/min vertical flow flocculator.
Second tier objectives for the next two years include developing a modular float valve, constant head tank, and metering tube apparatus that can be used for metering corrosive chemical solutions including chlorine and aluminum sulfate. We will also refine the design and protocol for the spinning bottle test to eliminate the need for the jar test apparatus.
By the end of Phase II we anticipate having two more AguaClara designed water treatment plants completed in small Honduran towns and two additional plants in the initial construction phase. Our goal is to have plant capacity for at least 10,000 people under construction by the end of the summer of 2008. As the AguaClara project expands and as our partner Agua Para el Pueblo begins building more water treatment plants we will need to help identify funding sources for the capital costs of the treatment plants. We plan to increase the number of individual donors who are supporting AguaClara, add support from Foundations, and begin to make connections with USAID and development banks.
Ultimately, even a well engineered water treatment system can fail if it is not implemented with attention to the context and cultural constraints. We believe completion of our task will ultimately require that we evaluate the entire water treatment system including the supply of chemicals to operate the plants, the impact on communities of higher water tariffs, the accountability of the local water boards to the communities to ensure that the water treatment plants are being operated well, the ability of the operators to monitor plant performance and to receive rapid feedback on the effects that operational changes have on water quality, and to make needed repairs when components fail. Students participating in the project are developing treatment plant operator training programs and methods for community outreach that will result in robust systems that will continue to operate long after the “Gringos” have left.
Journal Articles on this Report : 1 Displayed | Download in RIS Format
Other project views: | All 4 publications | 1 publications in selected types | All 1 journal articles |
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Weber-Shirk ML, Chan KL. The role of aluminum in slow sand filtration. Water Research 2007;41(6):1350-1354. |
SU833179 (Final) |
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Supplemental Keywords:
Gravity powered water treatment, hydraulic flocculation, sedimentation, gravity dosing system, spinning bottle test,, RFA, Geographic Area, Water, Sustainable Industry/Business, Sustainable Environment, Technology for Sustainable Environment, Drinking Water, International, sustainable development, flocculation, turbidity, Honduras, environmental engineering, drinking water treatmentRelevant Websites:
http://eswserver.cee.cornell.edu/aguaclara/ Exit
The 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.