Grantee Research Project Results
2009 Progress Report: Electrochemical Arsenic Remediation in Rural Bangladesh
EPA Grant Number: SU834017Title: Electrochemical Arsenic Remediation in Rural Bangladesh
Investigators: Gadgil, Ashok , Sedlak, David L. , Cheng, Deborah , Huang, Jessica , Kowolik, Kristin , Muller, Marc , Kostecki, Robert , Amrose, Susan , Srinivasan, Venkat
Current Investigators: Gadgil, Ashok , Wang, John , Sedlak, David L. , vanGenuchten, Case M. , Wart, Sarah van , Enscoe, Abby , Torkelson, Andrew , Soares, Carol , Cheng, Deborah , Zielke, Eric , Abed, Farzana , Mangold, Jennifer , Huang, Jessica , Fulton, Julian , Harrington, Kayley , Kowolik, Kristin , Muller, Marc , Itten, Michèle , Cousino, Nicole , Lin, Rebecca , Kostecki, Robert , Ramesh, Shreya , Amrose, Susan , Srinivasan, Venkat
Institution: University of California - Berkeley
EPA Project Officer: Page, Angela
Phase: II
Project Period: August 15, 2008 through August 14, 2010
Project Period Covered by this Report: August 15, 2008 through August 14,2010
Project Amount: $75,000
RFA: P3 Awards: A National Student Design Competition for Sustainability Focusing on People, Prosperity and the Planet - Phase 2 (2008) Recipients Lists
Research Category: Pollution Prevention/Sustainable Development , P3 Challenge Area - Safe and Sustainable Water Resources , P3 Awards , Sustainable and Healthy Communities
Objective:
The purpose and scope of Phase I research was to develop ElectroChemical Arsenic Remediation (ECAR) technology to the point of prototyping and testing in the field. The purpose and scope of Phase II is to prove technical viability of an ECAR prototype in the field through preliminary and extended field trials (Year 1) and develop a pilot project with a business plan for implementation (Year 2).
Progress Summary:
Preliminary Field Trials in Bangladesh and Cambodia
Our student team built the first continuous flow ECAR prototype, dubbed “Sushi” for the inner sushi-like electrode roll, in 2008. The device was powered by a 12 V car battery via a small constant current circuit. It was used to treat water from two arsenic-contaminated tube wells (TWs) in Dhingaghanga village near Dhaka, Bangladesh (initial arsenic 200 and 250 ppb, respectively), and nine arsenic-contaminated tube wells from three communes (Preak Russei, Dei Edth and Preak Aeng) in Kandal Province, Cambodia (initial arsenic concentrations 80–760 ppb).
Table 1 lists the initial (immediately before ECAR treatment) and final (after ECAR treatment) arsenic concentrations for the two TW samples from Dhingaghanga village. For initial arsenic concentrations of 200–250 ppb, the final arsenic concentration was below the World Health Organization (WHO) limit of 10 ppb in both cases (final arsenic = 8 and 7 ppb respectively). This demonstrates that ECAR treatment is effective in typical groundwaters near Dhaka. It also demonstrates the effectiveness of the Sushi prototype design under field conditions. Field results are key to establishing efficacy because real groundwater contains organic and inorganic matter that could potentially interfere with the ECAR process and is difficult to reproduce in the laboratory.
Table 1 shows that 2 days of quiescent settling in place of costly 0.1 micron filtration (used in the laboratory) is sufficient to reduce arsenic to less than the Bangladesh limit of 50 ppb but not quite the WHO limit of 10 ppb. Final arsenic concentrations using this method were 12 and 16 ppb for TW 1 and TW 2, respectively. It is likely that a longer settling time, or the addition of a coagulant such as alum, could result in a final arsenic concentration below the WHO limit of 10 ppb.
Table 1. Arsenic concentrations before (initial) and after (final) ECAR treatment for tube well water samples taken from Dhingaghanga village near Dhaka, Bangladesh. Also shown (far right column) is the final arsenic concentration after 2 days of quiescent settling in place of 0.1 micron filtration.
Tube Well |
Initial Arsenic Concentration (ppb) |
Final Arsenic Concentration (ppb) |
Final Arsenic Concentration - 2 day settling only (ppb) |
TW 1 |
200 |
8 |
12 |
TW 2 |
250 |
7 |
16 |
Figure 1 shows the initial (immediately before ECAR treatment) and final (after ECAR treatment) arsenic concentrations for the nine TW water samples from Kandal Province. For initial arsenic concentrations of 80–760 ppb, the final arsenic concentration was below the WHO limit of 10 ppb in every case. In eight cases, the final arsenic concentration was below 5 ppb, including five cases in which no arsenic was detected in the final sample (reporting limit for ICPMS = 1 ppb). This demonstrates that ECAR treatment is effective in typical groundwaters of Kandal Province. It also reasserts the effectiveness of the Sushi prototype design under field conditions.
Figure 1. Initial and final arsenic concentrations for tube well samples from Cambodia treated using ECAR
Preparation for Extended Field Trials
Prototypes
Useful feedback on prototype design and villager preferences was obtained from both preliminary field trials. Based on feedback, we returned to a batch reactor design over the Sushi continuous flow design. This was due to (1) the lack of accurate valves available in Bangladesh, (2) the difficulty establishing a water-tight seal at low cost, and (3) the disadvantages of continuous flow devices in light of intermittent electricity and the batch nature of the settling process.
In preparation for an extended technical field trial of an ECAR device, our team built and tested 20 L and 100 L batch reactor prototypes based on feedback from the preliminary trials. The 20 L batch reactor (Figure 2) was used as a bench scale device to test different electrode configurations, agitation methods and mixing times. The 100 L batch reactor was designed and fabricated to operate continuously over several weeks in the field. A schematic of the electrode assembly (operated inside a cylindrical water tank) is shown in Figure 3. This assembly is hooked up to a settling tank, where a coagulant is added and flocs are allowed to settle, leaving clean water. The 100 L prototype is wired to operate on intermittent grid electricity, using a battery and trickle charger to maintain current when power is out. Both prototypes were shown to remove arsenic more efficiently than the original bench tests.
Figure 2. 20 L ECAR reactor prototype containing 6 iron plate electrodes. This reactor prototype was used for bench- scale testing.
Figure 3. Schematic of the inner electrode assembly for a 100 L Batch ECAR reactor. This reactor will be used for an extended field trial.
Enhancing the Settling Rate of ECAR-Generated Particles
Without coagulant, the natural settling rate of ECAR-generated particles is approximately 3 days. A viable prototype system must complete treatment in several hours. To enhance the settling rate of ECAR-generated particles, our team tested several low cost coagulants, including Alum (aluminum sulfate), polyacrylamide, polyelectrolyte and salt. Alum was found to be extremely effective at neutral pH, leading to a 96 percent decrease in supernatant arsenic after 30 minutes. Increasing the charge density by a factor of two was found to also increase the settling rate, though not as effectively as Alum. We are currently comparing the cost and waste generation tradeoffs between these two methods.
Waste Disposal Plan
Arsenic-laden sludge produced from ECAR was submitted to the Toxic Characteristics Leaching Procedure (TCLP). The TCLP is designed to determine the mobility of inorganic analytes present in liquid wastes and determine if a waste meets the definition of toxicity, carrying a hazardous waste code under U.S. law. ECAR waste passed the TCLP test (which includes arsenic), making it safe for disposal in a U.S. landfill. Students performed a comprehensive review of waste disposal options viable in India and Bangladesh and recommended that we incorporate ECAR waste into concrete used in roads construction. Banerjee and Chakraborty (2005) showed that up to 40 percent by volume of concrete mixture could be replaced with arsenic-bearing sludge and still pass the Indian equivalent of the TCLP. This option is being researched further for ECAR.
Actual Versus Anticipated Outcomes
Over the past year, we have made some necessary changes and alterations to our original plan. The first change has been to focus on an arsenic-affected region in West Bengal, India, for our extended field trials instead of Bangladesh. West Bengal is geographically identical to our previous region of focus in Bangladesh, and our current partner village is only a few miles from the border. The change was made to leverage the interest and excellent local contacts of potential collaborators at Jadavpur University in Kolkata, India.
The second change has been to delay the extended technical trial and pilot project in response to advice from business contacts and the drastic change in funding and partner availability we experienced during the global economic recession of 2009. The delay will allow us to form more favorable business partnerships and increase the likelihood of ECAR successfully going to scale.
Future Activities:
ECAR was the subject of the Clean Tech 2 Market Program, in which graduate students from Haas School of Business partnered with a Berkeley science team to work on business plans and business pitch documents. As a team, we concluded that it is too soon for a detailed business plan to be developed, and a pilot project should be completed first in collaboration with an interested business partner to provide relevant inputs. We worked with the business students to develop a pamphlet, FAQ document and business pitch to help identify a business partner. We also held several stakeholder meetings in West Bengal to attract Indian business partners. We are in promising discussions with an Indian company considering licensing our technology and working towards commercialization.
Although we have diverged slightly from our original plan, our mission to enable clean water access in arsenic-affected regions has not changed. We have made some giant leaps toward our goal of implementation and scaling of the ECAR device, which would not have been possible without U.S. Environmental Protection Agency Phase II funding. Our current plan forward is to continue with an extended technical trial of the ECAR device, followed by a pilot project in collaboration with a business partner interested in taking ECAR technology to scale.
References:
Banerjee G, Chakraborty,R. Management of arsenic-laden water plant sludge by stabilization. Clean Technologies and Environmental Policy2005;7:270-278.
Beck R. World facing arsenic timebomb. BBC News: http://news.bbc.co.uk/2/hi/science/nature/6968574.stm. 2007.
Chowdhury UK, et al. Groundwater arsenic contamination in Bangladesh and West Bengal, India. Environmental Health Perspectives2000;108(5):393-397.
Kahn M. Arsenic in water a risk to 140 million people. Reuters: http://www.alertnet.org/thenews/newsdesk/L29757483.htm. 2007.
Smith AH, Lingas EO, Rahman M. Contamination of drinking-water by arsenic in Bangladesh: A public health emergency. Bulletin of the World Health Organization 2000;78(9).
Progress and Final Reports:
Original AbstractP3 Phase I:
Electrochemical Arsenic Remediation in Rural Bangladesh | 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.