TY - JOUR
T1 - Long-term electrode behavior during treatment of arsenic contaminated groundwater by a pilot-scale iron electrocoagulation system
AU - Bandaru, Siva R.S.
AU - Roy, Abhisek
AU - Gadgil, Ashok J.
AU - van Genuchten, Case M.
N1 - Funding Information:
We acknowledge funding provided by the Dutch Organization for Scientific Research in a Veni Grant to CMvG (Project No. 14400). SRSB gratefully acknowledges support from Andrew and Virginia Rudd Family Foundation Chair Funds of Prof. Gadgil, and from a CHED funded project at UC Berkeley on ECAR research for application in the Philippines. We gratefully acknowledge guidance from Joyashree Roy and Anupam DebSarkar (Jadavpur University) and technical assistance from Sebastian Krogh during the field experiments. Synchrotron experiments were performed partly at the DUBBLE beam line at the ESRF, Grenoble, France, with assistance from Dipanjan Banerjee. We also thank Ryan Davis for technical support during synchrotron data collection at SSRL. Use of SSRL, SLAC National Accelerator Laboratory, was supported by the U.S. Department of Energy, Office of Science, Basic Energy Sciences, under Contract No. DE-AC02-76SF00515.
Funding Information:
We acknowledge funding provided by the Dutch Organization for Scientific Research in a Veni Grant to CMvG (Project No. 14400 ). SRSB gratefully acknowledges support from Andrew and Virginia Rudd Family Foundation Chair Funds of Prof. Gadgil, and from a CHED funded project at UC Berkeley on ECAR research for application in the Philippines. We gratefully acknowledge guidance from Joyashree Roy and Anupam DebSarkar (Jadavpur University) and technical assistance from Sebastian Krogh during the field experiments. Synchrotron experiments were performed partly at the DUBBLE beam line at the ESRF, Grenoble, France, with assistance from Dipanjan Banerjee. We also thank Ryan Davis for technical support during synchrotron data collection at SSRL. Use of SSRL, SLAC National Accelerator Laboratory, was supported by the U.S. Department of Energy, Office of Science, Basic Energy Sciences , under Contract No. DE-AC02-76SF00515 .
Publisher Copyright:
© 2020 The Authors
PY - 2020/5/15
Y1 - 2020/5/15
N2 - Iron electrocoagulation (Fe-EC) is an effective technology to remove arsenic (As) from groundwater used for drinking. A commonly noted limitation of Fe-EC is fouling or passivation of electrode surfaces via rust accumulation over long-term use. In this study, we examined the effect of removing electrode surface layers on the performance of a large-scale (10,000 L/d capacity) Fe-EC plant in West Bengal, India. We also characterized the layers formed on the electrodes in active use for over 2 years at this plant. The electrode surfaces developed three distinct horizontal sections of layers that consisted of different minerals: calcite, Fe(III) precipitates and magnetite near the top, magnetite in the middle, and Fe(III) precipitates and magnetite near the bottom. The interior of all surface layers adjacent to the Fe(0) metal was dominated by magnetite. We determined the impact of surface layer removal by mechanical abrasion on Fe-EC performance by measuring solution composition (As, Fe, P, Si, Mn, Ca, pH, DO) and electrochemical parameters (total cell voltage and electrode interface potentials) during electrolysis. After electrode cleaning, the Fe concentration in the bulk solution increased substantially from 15.2 to 41.5 mg/L. This higher Fe concentration led to increased removal of a number of solutes. For As, the concentration reached below the 10 μg/L WHO MCL more rapidly and with less total Fe consumed (i.e. less electrical energy) after cleaning (128.4 μg/L As removed per kWh) compared to before cleaning (72.9 μg/L As removed per kWh). Similarly, the removal of P and Si improved after cleaning by 0.3 mg/L/kWh and 1.1 mg/L/kWh, respectively. Our results show that mechanically removing the surface layers that accumulate on electrodes over extended periods of Fe-EC operation can restore Fe-EC system efficiency (concentration of solute removed/kWh delivered). Since Fe release into the bulk solution substantially increased upon electrode cleaning, our results also suggest that routine electrode maintenance can ensure robust and reliable Fe-EC performance over year-long timescales.
AB - Iron electrocoagulation (Fe-EC) is an effective technology to remove arsenic (As) from groundwater used for drinking. A commonly noted limitation of Fe-EC is fouling or passivation of electrode surfaces via rust accumulation over long-term use. In this study, we examined the effect of removing electrode surface layers on the performance of a large-scale (10,000 L/d capacity) Fe-EC plant in West Bengal, India. We also characterized the layers formed on the electrodes in active use for over 2 years at this plant. The electrode surfaces developed three distinct horizontal sections of layers that consisted of different minerals: calcite, Fe(III) precipitates and magnetite near the top, magnetite in the middle, and Fe(III) precipitates and magnetite near the bottom. The interior of all surface layers adjacent to the Fe(0) metal was dominated by magnetite. We determined the impact of surface layer removal by mechanical abrasion on Fe-EC performance by measuring solution composition (As, Fe, P, Si, Mn, Ca, pH, DO) and electrochemical parameters (total cell voltage and electrode interface potentials) during electrolysis. After electrode cleaning, the Fe concentration in the bulk solution increased substantially from 15.2 to 41.5 mg/L. This higher Fe concentration led to increased removal of a number of solutes. For As, the concentration reached below the 10 μg/L WHO MCL more rapidly and with less total Fe consumed (i.e. less electrical energy) after cleaning (128.4 μg/L As removed per kWh) compared to before cleaning (72.9 μg/L As removed per kWh). Similarly, the removal of P and Si improved after cleaning by 0.3 mg/L/kWh and 1.1 mg/L/kWh, respectively. Our results show that mechanically removing the surface layers that accumulate on electrodes over extended periods of Fe-EC operation can restore Fe-EC system efficiency (concentration of solute removed/kWh delivered). Since Fe release into the bulk solution substantially increased upon electrode cleaning, our results also suggest that routine electrode maintenance can ensure robust and reliable Fe-EC performance over year-long timescales.
KW - Anodic dissolution
KW - Arsenic removal
KW - Electrode surface layers
KW - Iron electrocoagulation
KW - Sustainable water treatment
UR - http://www.scopus.com/inward/record.url?scp=85081001211&partnerID=8YFLogxK
U2 - 10.1016/j.watres.2020.115668
DO - 10.1016/j.watres.2020.115668
M3 - Article
C2 - 32163769
AN - SCOPUS:85081001211
SN - 0043-1354
VL - 175
JO - Water Research
JF - Water Research
M1 - 115668
ER -