Solar-driven rooftop interfacial evaporation system for decentralized rainwater purification.

Area of Science:

• Materials Science
• Environmental Engineering
• Water Treatment Technologies

Background:

• Global freshwater scarcity necessitates decentralized, low-energy water purification.
• Uneven distribution of existing water treatment infrastructure exacerbates the problem, especially in off-grid regions.

Purpose of the Study:

• To develop and evaluate a rooftop-based, solar-driven in situ rainwater evaporation and purification system (IREPS).
• To assess the system's performance, cost-effectiveness, and global applicability for decentralized clean water access.

Main Methods:

• A dual-network hydrogel (CSA-Fe) with embedded Fe₃O₄ nanoparticles was synthesized for the system.
• The IREPS was tested outdoors for 70 days, measuring water production flux and quality.
• Techno-economic analysis and a machine learning-based Solar Rainwater Purification Suitability Index (SRPSI) were employed.

Main Results:

• The IREPS achieved an average water production flux of 4.1 kg m⁻² d⁻¹ and a peak flux of 6.6 kg m⁻² d⁻¹.
• Purified water consistently met World Health Organization (WHO) drinking-water standards.
• The treatment cost was determined to be USD 3.85 per cubic meter, demonstrating cost-effectiveness.

Conclusions:

• The developed IREPS provides a practical and scalable solution for decentralized rainwater purification.
• The system is suitable for remote, arid, and resource-constrained settings, offering a feasible pathway to clean water.
• Priority regions for deployment include Central Africa, South Asia, and Southeast Asia based on the SRPSI.