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.

Desalination

Reverse osmosis and thermal methods, such as NIOT's Low-Temperature Thermal Desalination plant at Kavaratti (2005), turn seawater into freshwater.

Recycling

Membrane bioreactors and tertiary treatment turn sewage into usable water.

Atmospheric and recharge methods

Atmospheric water generators and fog nets draw water from air, while managed aquifer recharge stores runoff underground.

Seawater desalination

It offers a rain-independent supply, as at Chennai's Minjur and Nemmeli plants, but uses about 3-4 kWh per cubic metre and leaves roughly 1.5 litres of brine per litre of freshwater.

Wastewater recycling

Singapore's NEWater meets up to 40% of demand and Welspun's Anjar unit runs on 30 MLD of recycled sewage, though public aversion, residual contaminants and missing sewers hold it back.

Atmospheric water generators

Modular kiosks, as at Secunderabad station (2019), need no source, but are energy-hungry and fail in dry air.

Reuse and green power

Implement the National Framework on Safe Reuse of Treated Water (2022) and AMRUT 2.0's recycling targets, and run desalination on renewables.

Cut demand first

Pair new supply with micro-irrigation under Per Drop More Crop and volumetric pricing.