Q. The world is facing an acute shortage of clean and safe freshwater. What are the alternative technologies which can solve this crisis? Briefly discuss any three such technologies citing their key merits and demerits.

Model Answer:

With the UN warning that 2 billion people lack safe drinking water and NITI Aayog projecting severe water stress, alternative technologies are crucial for global water security.

1. Emerging Alternative Technologies for Freshwater

• Desalination: Membrane-based (Reverse Osmosis) and thermal processes converting seawater to potable water.
• Wastewater Valorization: Ultra-filtration and reverse osmosis recycling sewage into pure drinking water.
• Atmospheric Water Generation (AWG): Condensing atmospheric humidity directly into purified water.
• Nanotechnology Filtration: Utilizing carbon nanotubes and graphene oxide to eliminate micro-pollutants and heavy metals.
• Solar Hydrogels: Employing sunlight-driven evaporation to extract clean water from contaminated or saline sources.

2. Analysis of Three Key Technologies

1. Desalination Technology: (Example: Nemmeli Plant, Chennai)
   • Merits: Provides an inexhaustible, climate-resilient freshwater source, guaranteeing supply security for rapidly growing coastal megacities.
   • Demerits: Extremely energy-intensive (large carbon footprint), high setup costs, and toxic hypersaline brine discharge threatens marine ecosystems.
2. Advanced Wastewater Recycling: (Example: NEWater, Singapore)
   • Merits: Drives a circular economy, mitigates sewage discharge into rivers, and ensures high resource-efficiency for industrial and domestic use.
   • Demerits: High initial capital requirement, continuous complex monitoring needs, and a strong psychological “yuck factor” hindering mass public acceptance.
3. Atmospheric Water Generators (AWG): (Example: ‘Meghdoot’ systems across Indian Railways)
   • Merits: Offers a decentralized, plug-and-play solution requiring no ground or surface water source, making it highly effective in humid, remote geographies.
   • Demerits: Yield remains heavily climate-dependent (fails in arid regions below 30% humidity) and incurs high per-liter electricity costs.

Achieving SDG 6 (Clean Water and Sanitation) requires transitioning from linear extraction to a circular water economy by integrating these technologies with robust conservation and Integrated Water Resources Management (IWRM).