PANAJI
The Goa government is now exploring the use of treated wastewater from Sewage Treatment Plants (STPs) for green hydrogen (H2) production. The Goa Energy Development Agency (GEDA) has roped in Birla Institute of Technology and Science (BITS), Pilani to help the State achieve the goal.
The Institute will develop the optimised electrolysis system with integrated partial purification system with high-performance electrocatalysts to achieve enhanced H2 production rates, improved energy efficiency, and long-term stability.
BITS will conduct Real-world validation at the 600 cumec STP facility at its campus, enabling direct application of the developed strategy. Based on the successful completion of the project, specific larger scale units will be deployed at different STP plants in Goa.
According to the concept paper, prepared by Prof Pradeep Sow, submitted to GEDA despite undergoing multiple treatment stages, the effluent from STPs is not used as potable water and is commonly discharged into surface water bodies. “An alternative and sustainable approach, the project aims to develop a cost-effective strategy to repurpose this STPs water for green hydrogen (H2) production with minimal additional purification steps,” the study said.
According to Prof Sow, owing to its relatively lower ionic strength and contaminant levels, STP water presents a more promising alternative to seawater for electrolysis-based H2 production.
“However, STP water contains a wide variety of trace ions, which can negatively or positively affect water electrolysis. However, ICP analysis of the water obtained from the STP plant in Panaji reveals that, in addition to major contaminants, several minor impurities are also present in small amounts, which can, in turn, impact electrolyser performance,” he said.
BITS preliminary results using STP water obtained from Panaji STP plant suggest that contamination has minimal effect on the hydrogen evolution reaction (HER), but it significantly impacts the oxygen evolution reaction (OER).
“While this preliminary data lacks long term effects, it indicates that the STP water should not be used directly for water electrolysis. Notably, seawater, tap water, and STP water all show diminished OER performance relative to ultrapure water,” Prof Sow said.
He said that to address the challenges in using STP water for electrolysis, first a mapping of its ionic composition will be done. The mapping will also account for the systematic year-long season variation across the targeted STP plants in Goa.
BITS proposes the use of alkaline water electrolysis (AWE) powered by treated STP water as a cost-effective and sustainable pathway for green H2 production.
“Based on the mapping of ions and their effect on the HER and OER performance, we will identify targeted water treatment strategies, separately for the HER and OER segments and to selectively remove harmful ions,” the study said.
