SafaPani: A Household Electrocoagulation Arsenic ... - ScienceDirect

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ScienceDirect Procedia Engineering 78 (2014) 274 – 278

Humanitarian Technology: Science, Systems and Global Impact 2014, HumTech2014

SafaPani: a household electrocoagulation arsenic water filter for Nepal and other developing countries Aditya Maharaab*, Jeremy Baskinb, Victoria Tersignia, Scott Gladstonea, Julie Ann Haldemana a

Dartmouth Humanitarian Engineering, Dartmouth College, 800 Cummings Hall, Hanover, NH 03755, USA b Thayer School of Engineering, Dartmouth College, 14 Engineering Dr, Hanover, NH 03755, USA

Abstract Arsenic contamination of drinking water is a major problem for many people worldwide, especially the inhabitants of Bangladesh and Nepal. Through Dartmouth Humanitarian Engineering (DHE) at Dartmouth College, we are working to create a home-based arsenic filtration system. The ultimate goal of this project is to provide highly effective, reliable and affordable filters for the people affected by this problem in Nepal and other countries. This paper illustrates the purpose of the project, reports results obtained while creating various components of the filer, and discusses future plans to create a fully assembled, deployable prototype. Our current working prototype can get arsenic concentration below the WHO safe drinking limit of 10ppb – specifically to 2.58ppb starting from 260 ppb. © 2014 2014 The Elsevier Ltd. This is an open access Ltd. article under the CC BY-NC-ND license © Authors. Published by Elsevier (http://creativecommons.org/licenses/by-nc-nd/3.0/). Selection and peer-review under responsibility of the Organizing Committee of HumTech2014. Selection and peer-review under responsibility of the Organizing Committee of HumTech2014 Keywords: Aresnic; clean water; Nepal; SafaPani; Village Tech Solutions; Dartmouth; DHE

1. Introduction The World Health Organization (WHO) has recognized arsenic contamination of drinking water in South Asia as “a public-health emergency” and “the largest mass poisoning of a population in history” [1]. Arsenic consumption poses severe health risks, particularly in concentrations above the maximum safe drinking water level of 10 parts per billion (ppb). More than hundreds of millions of people are at risk due to drinking arsenic-contaminated groundwater [2]. Developing countries like Nepal, which is largely rural, lacks the finance and infrastructure to implement industrial-scale water purification systems like those found in developed countries. Additionally, Nepal is a “lowtrust” society, in that citizens are suspicious of cooperative ventures and communal resources. This, along with Nepal’s caste system that frowns upon manual labor, makes it difficult to implement a community-level water purification system. The GDP per capita (US$) of Nepal during 2009-2013 was $690 [3] and illiterate children and

1877-7058 © 2014 Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/3.0/).

Selection and peer-review under responsibility of the Organizing Committee of HumTech2014 doi:10.1016/j.proeng.2014.07.067

Aditya Mahara et al. / Procedia Engineering 78 (2014) 274 – 278

women are the water collectors; therefore a purification device would need to be both inexpensive and easy to use. Accordingly, a simple method of water purification at the household level would address the problem of arsenic contamination in well water in these developing countries [4]. For this purpose, it has been reported that electrocoagulation is a potentially successful method to remove arsenic from water [5,6]. We hope that Thayer School of Engineering students and that Dartmouth Humanitarian Engineering (DHE) will be able to collaboratively design, test, market and eventually distribute a home scale arsenic-removing filter in Nepal. DHE was founded in 2004 in response to the growing need for global poverty reduction and student demand for service and engineering opportunities abroad. Today, DHE is an award-winning, impact-driven group of university students who are committed to making a difference through small-scale, sustainable solutions. We run a variety of technical projects in developing nations focused on providing fundamental needs. These include small-scale hydropower systems, improved cookstoves, and increased access to clean biofuels. Here, the SafaPani clean water project will discuss its purpose, its history and its plans for the future.

2. The SafaPani Project at Dartmouth College Arsenic-contaminated groundwater is a severe problem for the many Nepalese people for whom it is their primary source of drinking water. Main failures are an inability to effectively and reliably remove arsenic from the water to recommended standards while keeping the device at a reasonably low cost. Our goal is to develop a lowcost electrocoagulation arsenic removal device that meets this standard. 2.1 History In the past, there have been teams of senior engineering students who have worked on this project as their culminating experience at Thayer School of Engineering [7,8]. DHE is currently collaborating with one such team of students to work on creating a deployable prototype of a home-based arsenic removal filter. These seniors are the third group to have worked on this project, and all these three groups have been commissioned and sponsored by an NGO called Village Tech Solutions (VTS). * After this month, this year’s group will have completed a final prototype and DHE will work on developing, marketing and eventually distributing this technology to people in need in Nepal. With previous senior project groups confirming the electrocoagulation process and performing successful chemical and mechanical sensitivity analyses on the prototype device, efforts for this project will firstly focus on development of a Computer Aided Design(CAD) model of a producible prototype while further ensuring user reliability, specifically within the electrocoagulation and filtration processes. Specifically, a device to inform the user when the extent of the electrocoagulation reactions is sufficient for appropriate arsenic removal will be explored, along with a device or method to extend the life and overall quality of the sand within the filter. From previous studies at Thayer School of Engineering, it has been reported that the amount of charge through the electrodes can be a gauge for reaction extent for the electrocoagulation process. An electrical device has been proposed to track this overall charge and to either visually alert the user when the reaction has been completed or to automatically open the valve to the electrocoagulation vessel. This design was chosen to eliminate the need for the user to manually open the valve, and to prevent premature emptying of the water to the filter. Routine filter maintenance requires replacement of the sand; to extend the life of the sand filter, the quality of sand used and the physical interaction of the arsenic-carrying precipitate with the sand must be analysed. Observations recorded by previous groups showed that the precipitate collects mostly at the very top of the sand layer, creating a crust or film of contaminated sand. Processes to remove or score this thin film are being explored along with standardizing sand use by routinely supplying pre-packaged sand cartridges to users.

*

Contact Information for VTS: Manager - David Sowerwine

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2.2. Current Operations In the winter of 2013, we conducted a pilot field study in Nepal to explore the arsenic contamination in the district of Nawalparasi, to learn the social impacts and requirements within these communities, and to make connections with NGOs who are interested in creating arsenic removal technologies. Results have been very useful in steering our direction for the project and they have helped us redesign our model. 3. Technology and Water Filtration System Design In this section, we present CAD model of the filter, followed by the electrocoagulation technology and finally some metrics and results obtained so far. 3. 1. CAD Model of the filtration unit

Fig. 1. A) CAD model of the filter B) Cross section of the filter where: i) the outside cylinder represents the ‘collection vessel’ which includes the diffusion plate and sand and ii) the inside cylinder represents the ‘reaction vessel’ which houses electrodes and is the vessel where the electrocoagulation takes places before the water is released to the collection vessel, and C) top view of the reaction vessel with a transparent lid, also showing blue flapper which is released to channel water from reaction vessel to collection vessel. CAD models made by Stefan J. Deutsch.

3. 2. Electrocoagulation Technology The main technology we use to create our filtration system is called electrocoagulation. Electrocoagulation can be viewed as a four-step process once a current is placed through the electrodes: Fe(s) Æ Fe2+(aq) + 2e-

(1)

2H2O(l) + 2e- Æ H2(g) + 2OH-

(2)

½ H2O(l) + ¼ O2(aq) + Fe2+(aq) Æ Fe3+ + OH-(aq)

(3)

Fe(OH)3 (s) + AsO43-(aq) Æ [Fe(OH)3 + AsO43-](s)

(4)


x x x x

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Iron is oxidized at the anode and released into solution. Water is separated into hydrogen gas and soluble hydroxide ions through electrolysis at the cathode. Iron is oxidized further while in solution. Iron ions react with soluble hydroxide in solution to form an insoluble precipitate. These flocs increase in size with time as the Fe(OH)3 continues to precipitate onto existing flocs. Throughout this process, arsenic is also trapped and bound into these larger Fe(OH)3 flocs and therefore removed from the water.

3.3. Metrics and Results Based on Faraday’s First Law of Electrolysis, the amount of time required for the solution to reach 25 ppm of iron is approximately 6 hours and 20 minutes. 25ppm of iron is required for best results to reduce the arsenic levels in the water. Once this concentration is reached, the solution is left to react for approximately an additional half hour without current flow—the time we define as “batch time”. In other words, “batch time” is the time after no more current is provided to the electrodes and before the valve is released to send the water to the collection vessel. Our results show that letting the solution settle during this “batch time” significantly reduced the amount of arsenic in the solution. We also have incorporated an electronic component within the device. The electronics is used to keep track of reaction time, shut current off to the electrodes once enough iron is released in the solution, and set a timer for allocated “batch time” before finally releasing the valve to let water flow to the sand in the collection vessel. At this point, we notify the user regarding the completion of the process by the illumination of an LED. Furthermore, the electronics are used to indicate when insufficient current is flowing through solution, and therefore, when the electrodes need to be moved closer together, adjusted, or replaced.

Fig. 2. Prototype validation with i) inital [As] = 260.11ppb, ii) pre-batch time [As] = 209.78, iii) post-batch time [As] = 3.66 ppb, iv) post filtration - sample 1 [As] = 2.58ppb and v) post filtration – sample 2: [As] = 2.67 ppb. For this experiment, concentration of iron used was [Fe] = 25 ppm.

Before the reaction, [As] = 260.11 ppb and after going through the filter the final sample [As] = 2.58ppb. Another reading was taken to reconfirm the final [As] which was 2.67ppb. Therefore, at best, our current working prototype can get arsenic concentration below the WHO safe drinking limit of 10ppb – specifically to 2.58ppb starting from 260 ppb. For this experiment the concentration of arsenic was calculated using the help from Dartmouth Trace Elements Lab.

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4. Discussion and Future Work Our immediate plan is to continue testing and construct a manufacturable prototype within next few months. Throughout the year, we will be in contact with NGOs in Nepal such as Environment and Public Health Organization (ENPHO) to organize the deployment of some of these prototypes in areas in Nepal affected by most by arsenic contamination and to receive feedback on device robustness, reliability and user friendliness. Within the next two years, we hope to market and distribute these filters in Nepal, which will be highly effective, yet affordable for the users. Acknowledgements Members of Dartmouth Humanitarian Engineering come from all corners of the globe. Although DHE is, at heart, an organization dedicated to solving global issues through engineering solutions, implementing new technologies requires a thorough understanding of their economic, environmental and cultural impact. Our diverse membership, supportive partners, and experienced advisory board each bring a variety of skills to the group, all of which are crucial for successful implementation of our projects. The SafaPani project would like to thank David Sowerwine and Dr. Edward Stritter, Managers of VillageTech Solutions. For DHE, we would like to thank our faculty advisors from the Thayer School of Engineering: Dr. Charles Sullivan, Associate Professor of Engineering; Holly Wilkinson, Assistant Dean of Academic & Student Affairs; Dr. Joseph J. Helble, Dean of Thayer School of Engineering; Everett Poisson, Director of Development; and Jeanne West, Associate Dean of Development & External Relations. The ENGS 89/90 team thanks its review board and Professor Ryan Halter, Professor Mark Laser, and Professor Kofi Odame for their generous technical guidance. We would also like to thank the members of our Board of Overseers, including: Jessica Freedman, Global Health Program Coordinator of Dickey Center for International Understanding; Dr. Edward Stritter, President of Stritter Consulting; and Michel Zaleski, Chairman of Soros Economic Development Fund. We would lastly like to thank our partners and sponsors from around the globe: Thayer School of Engineering at Dartmouth; John Sloan Dickey Center for International Understanding; Jane Goodall Institute; CARE; Ministry of Infrastructure of the Republic of Rwanda; Wildlife Conservation Society; e.quinox; University of Dar es Salaam; Kigali Institute of Science and Technology; Tuck School of Business; Byrne Foundation; and Rockdale Foundation. References [1] Smith, Allan H., Elena O. Lingas, and Mahfuzar Rahman. "Contamination of Drinking-water by Arsenic in Bangladesh: A Public Health Emergency." Bulletin of the World Health Organization 78 (2000): 1093-103. WHO. World Health Organization. Web. 16 Oct. 2013. [2] Kumar, R. P., Chaudhari, S., Khilar, K. C., Mahajan, S. P. (2004) Removal of arsenic from water by electrocoagulation. Chemosphere, 55, 1245 – 1252. [3] The World Bank Group, (Feb 27, 2014) Data – GDP Per Capita (Current US$). data.worldbank.org. retrieved Feb 27- 2014 from http://data.worldbank.org/indicator/ [4] Holt, P. K., Barton, G. W., Mitchell, C. A. (2005) The future for electrocoagulation as a localised water treatment technology. Chemosphere, 59, 355 – 376. [5] Sasson, M. B., Calmano, W., Adin, A. (2009) Iron-oxidation processes in an electroflocculation (electrocoagulation) cell. Journal of Hazardous Materials, 171, 704 – 709. [6] Parga, J. R., Cocke, D. L., Valenzuela, J. L., Gomes, J. A., Kesmez, M., Irwin, G., Moreno, H., and Weir, M. (2005) Arsenic removal via electrocoagulation from heavy metal contaminated groundwater in La Comarca Lagunera México. Journal of Hazardous Materials, B124, 247 – 254. [7] Abdul-Shakoor, Muhammed, Remi Gottheil, and Chris Martin. ENGS 90 Final Report: Developing a Home-Scale Electrocoagulation Arsenic Filter. Rep. N.p.: n.p., 2011. Print. [8] Holiday, Lindsay, Dana Leland, and Philip Wagner. ENGS 290 Final Report: Arsenic Removal. Rep. N.p.: n.p., 2009. Print.