The number of point-of-use water purifiers sold annually in India is expected to double between 2018 and 2023. Driven by the lack of reliable municipal water supply services and the increase in consumer awareness of water-borne diseases, sales are predicted at over $1 billion USD by 2023. However, with the per-capita water consumption in the country forecasted to nearly double from 2000 to 2025, the condition of the water supply in India is approaching a critical state. In this environment, the use of RO systems, which waste between 50 to 75% of the input water, is becoming undesirable. Instead, the GEAR Lab is developing an alternative solution that relies on electrodialysis (ED) to achieve a higher recovery of up to 90% while maintaining cost-competiveness with existing RO products in India.

Functional requirements for a home-scale ED system were identified by interviewing stakeholders across India, including end users, distributors, and manufacturers. A model for brackish water ED desalination was developed by the GEAR Lab to facilitate design and analysis of different stack configurations and system architectures. Applying these models, the optimal geometry, flow-rates, and applied voltage for total cost minimization were explored using a genetic algorithm, for satisfying the production rate (9-15 L/hr) and product concentration (100-300 mg/L) requirements for the device.

The first two bench-scale prototype systems were developed in conjunction with our partner, Eureka-Forbes Limited, experimentally demonstrated >80% recovery from feed concentrations as high as 3000 mg/L in a batched operation mode. To further reduce capital cost, a continuous flow system was developed to decrease the number of valves and tanks. Additionally, a novel single-pump architecture was developed to further reduce costs. Typically, two pumps are used, one for the product stream and one for the brine stream. To recover more than half of the feedwater as product water, the brine is recirculated. In this new single-pump architecture, a flow restrictor on the brine stream reduces the flow rate to ensure more of the feedwater is recovered as product water. Electrodialysis is able to achieve higher recoveries than reverse osmosis with less impact on membrane lifetime. However, due to rising component costs, in order to achieve a salinity decrease competitive with reverse osmosis (>90%), optimizations by the GEAR Lab show that an electrodialysis stack alone will cost the same or higher than an entire retail reverse osmosis system. The GEAR Lab is continuing to explore innovative ways to reduce the cost of electrodialysis systems while maximizing performance.

Peer-Reviewed Journal Articles

Using feed-forward voltage-control to increase the ion removal rate during batch electrodialysis desalination of brackish water
Shah, S. R., Walter, S. L., & Winter, A., Desalination (2019) || download

Cost-Optimal Design of a Batch Electrodialysis System for Domestic Desalination of Brackish Groundwater
Shah, S. R., Wright, N. C., Nepsky, P. A., & Winter, A., Desalination (2018) || download

A Robust Model of Brackish Water Electrodialysis Desalination with Experimental Comparison at Different Size Scales
Wright, N. C., Shah, S. R., Amrose, S.E., & Winter, A., Desalination (2018) || download

Feasibility Study of an Electrodialysis System for In-Home Water Desalination and Purification in Urban India 
Nayar, K. G., Sundararaman, P., Schacherl, J. D., O’Connor, C. L., Heath, M. L., Gabriel, M. O., Shah, S., Wright, N. & Winter, A., Development Engineering (2017) || download

Peer-Reviewed Conference Articles

Optimal Design of a Batch Electrodialysis System for Domestic Desalination
Shah, S.R., Wright, N.C., Nepsky, P., & Winter, A., Proceedings of the International Desalination Association World Congress on Water Reuse and Desalination (2017), IDA17WC-58064, Sau Paulo, Brazil

Feasibility Study of an Electrodialysis System for In-Home Water Desalination and Purification in Urban India.
Nayar, K. G., Sundararaman, P., Schacheri, J. D., Connor, C. L. O., Heath, M. L., Wright, N. C., & Winter, A., ASME IDETC/CIE (2015)

Theses

Making Decentralized Desalination More Affordable Using Improved Process Design, Control, and Energy Recovery
Sahil Shah, PhD Thesis (MIT, August 2021)

Architecture and unit design of a capital cost optimized, household electrodialysis desalination device with continuous flow
Hannah Varner, Master’s Thesis (MIT, August 2020)

Cost-optimal design of a household batch electrodialysis desalination device
Shah, S.R., Master's Thesis (MIT, 2017)

Decentralized Water Treatment in Urban India, and the Potential Impacts of Reverse Osmosis Water Purifiers
Connor, C., Master's Thesis (MIT, 2016)

Press

PhD candidate Sahil Shah awarded the J-WAFS fellowship for his work on desalination, on MIT News

Best Paper Award IDA 2017 World Congress (São Paulo) in the Category of State-of-the-Art: “Optimal Design of a Batch Electrodialysis System for Domestic Desalination.,  in Pumps & Systems