Final Report: Electrochemical Arsenic Remediation in Rural BangladeshEPA Grant Number: SU833553
Title: Electrochemical Arsenic Remediation in Rural Bangladesh
Investigators: Gadgil, Ashok , Cheng, Deborah , Huang, Jessica , Kowolik, Kristin , Muller, Marc , Kostecki, Robert , Amrose, Susan , Srinivasan, Venkat
Institution: University of California - Berkeley
EPA Project Officer: Page, Angela
Project Period: September 30, 2007 through September 30, 2008
Project Amount: $9,971
RFA: P3 Awards: A National Student Design Competition for Sustainability Focusing on People, Prosperity and the Planet (2007) RFA Text | Recipients Lists
Research Category: Pollution Prevention/Sustainable Development , P3 Challenge Area - Safe and Sustainable Water Resources , P3 Awards , Sustainable and Healthy Communities
Arsenic in drinking water is a major public health problem threatening the lives of over 140 million people worldwide. Primary drinking water supplies are contaminated in Argentina, Chile, Mexico, China, Hungary, Cambodia, Vietnam, West Bengal (India), Bangladesh, and areas of the United States. In Bangladesh alone, between 35-77 million people drink arsenic-laden water from shallow wells, leading to what has aptly been called the largest mass poisoning of a population in history. Over one million deaths are expected due to arsenic-related cancer in Bangladesh. Millions more will suffer from arsenic-related medical conditions unless something is done.
The primarily rural population of Bangladesh is too poor to afford arsenic remediation techniques that are cost effective only on large scales. Current technical approaches to low-cost arsenic removal involve the addition of chemical adsorbents, which frequently exhibit one or more of the following environmentally degrading qualities: toxicity, use of strong alkalies or corrosive acids to regenerate, production of large quantities of arsenic-laden toxic waste, a short shelf life, and/or the need for an extensive supply chain with corresponding greenhouse gas emissions. In addition, these technologies are often deployed as point-of-use devices, to be operated and maintained by the user. Point-of-use systems have been plagued by high abandonment rates after a short time due to difficult maintenance or operation, lack of time to devote, and low cultural acceptability. A new model is needed to ensure sustainability of water treatment for future generations.
Electrocoagulation (EC) overcomes many of the obstacles of chemical adsorbents and can be used affordably and on a small-scale, allowing for rapid dissemination into Bangladesh to address this arsenic crisis. In EC, electricity is used to continuously dissolve an iron anode, forming corrosion products (collectively called ferric (hydr)oxides or rust). Thus the arsenic adsorbent is manufactured at the time of use -eliminating the need for a costly supply chain. In addition, this process greatly enhances the capacity of rust to adsorb arsenic, due to (i) an increase in the rate of rust production (by factors of 10 to 100 over natural rusting rate of metallic iron), and (ii) the rapid oxidation of As(III) in the water to the more favorable As(V) which binds much more readily to rust. Thus the employment of a small amount of electricity leads to a large advantage in efficiency, lowering the cost and producing far less waste than chemical adsorbents. In addition, the electrodes are self-cleaning if current is alternated, reducing maintenance and eliminating the need for corrosive acids or toxic chemicals for regeneration.
The main disadvantage of EC in rural areas is the need for electricity, albeit a small amount. However, community systems with full cost recovery based on an electronic technology have been successfully disinfecting surface water in rural areas of nearby India for several years (www.waterhealth.com). If the operating costs are low enough, modest profits on the treated water can attract business investment making the model rapidly scalable, while fully recovering the cost of an electricity source, maintenance, and operation and ensuring that local villagers continue to have stake in successfully operating the technology. The retail cost remains affordable to the poor (1-2¢ US for 10 liters per day). In light of the barriers that plague point-ofuse systems, a community kiosk model is a promising way to sustain clean water access long term.
Phase I tested and optimized the arsenic removal efficacy of EC in Bangladesh. Specifically, we proposed to test the performance of EC using both synthetic (i.e. constituted in the laboratory to have ionic concentrations and properties found in Bangladesh) and real Bangladeshi groundwater in order to independently verify its ability to reduce high levels of arsenic (> 600 μg/L) to levels the current World Health Organization (WHO) standard (< 10 μg/L) in the water environment of interest. In addition we proposed to perform batch experiments using a small-scale electrochemical device in order to establish the optimum electrochemical cell parameters for arsenic remediation performance, namely current density and charge per liter, bearing in mind the economic and technical requirements to function successfully in remote Bangladesh. The overall goal was to determine if EC could be optimized to be cost-effective enough to pursue its use in a community treatment center with full cost recovery.
We are pleased to report that we have achieved and exceeded our Phase I objectives. The following is a summary of our findings:
- We have verified the ability of EC to remove high levels of arsenic from both synthetic Bangladeshi groundwater and real Bangladeshi groundwater collected in two geographically distinct regions of Bangladesh. In all cases, EC was able to reduce arsenic levels below the WHO limit of 10 μg/L.
- We have measured the arsenic removal effectiveness in two types of synthetic groundwater as a function of electrochemical parameters, allowing empirical optimization of removal efficiency bearing in mind technical requirements of Bangladesh. The minimum amount of charge required for efficient arsenic removal in Bangladesh was determined.
- In addition to the goals laid out for Phase I, we have expanded our scope to explore knowledge-based optimization, utilizing several powerful analytical and electrochemical techniques, including polarization studies and X-ray absorption spectroscopy (XAS), to understand the underlying mechanism of arsenic removal in EC. This understanding could allow selective tuning of the EC parameters to gain an additional increase (by a factor of 2 or more) in efficiency.
- We have estimated the operating cost of EC, including the cost of consumable iron, to be 0.38¢ US/person/day, assuming 10 L/person/day and a photovoltaic electricity source. Material costs of the current design are expected to be about US $50-100 per device serving 200 people (devices are modular and scalable). Iron requirements are expected to be 106 grams/person/year (or 635 kg/center/year where each center meets the needs of 6000 people). Waste produced is expected to be only 120 grams/person/year.
- We have incorporated additional students who have designed and built a continuous flow EC prototype ready to be tested in the lab and in Bangladesh.
To date, Phase I results indicate that EC is extremely promising for use in a community treatment center with full cost recovery. We have demonstrated that it is low-cost, effective in the water environment of Bangladesh, requires very little iron input, and produces little waste. A student team has designed and fabricated a modular and scalable laboratory-sized continuous flow prototype ready to be tested and taken into the field for preliminary technical trials.
By May 2008, we expect to have knowledge-based optimization with the potential to provide an additional factor of 2 increase in efficiency as well as provide new scientific insight on arsenic complexation in the presence of corroding iron (leading to two journal publications). Our prototype will be lab tested during spring/early summer of 2008. Following lab tests, students have arranged to conduct preliminary field testing in arsenic-affected regions of Cambodia. Cambodia was chosen to leverage an existing plan for a trip and strong student ties to a reputable NGO offering funding, as well as to begin an offshoot project to develop EC in Cambodia. The trip itself is outside the scope of the P3 project and funding, but will provide valuable information on the ability of the prototype to operate in a developing country. Field testing in Bangladesh is planned as a part of Phase II.
Proposed Phase II Objectives and Strategies:
The scientific work of Phase I has demonstrated that EC technology can operate effectively, cheaply, and efficiently enough to be successful in a for-profit community center model. The challenge of Phase II is to bring our prototype from a laboratory scale to a working pilot project providing sustainable clean water with full cost recovery to a village in Bangladesh.
We propose to meet the challenge of Phase II with several key objectives:
- Prove technical viability of the EC prototype under continuous use in Bangladesh. We will conduct two technical field trials of increasing rigor; a short-term (1-2 day) and extended (1 month) run during which we will clean and monitor groundwater water using our prototype device. For the extended trial, we will partner with a village to provide temporary clean water free of cost (without compromising villagers’ access to current water sources) and gather information on the social acceptability of the water, including taste and color. Waste removal strategies will be tried and evaluated.
- Develop a pilot scale business plan with full cost recovery suitable for rural Bangladesh. This will be done in parallel with (1) and will include waste removal strategies tested during (1).
- Design, develop, implement, and operate a pilot project for 8 months incorporating full cost recovery, including pre-and post-economic surveys, along with public health education and outreach.
Success will provide a financially and environmentally sustainable model for providing clean water to Bangladeshi villages ready for replication and scale-up.