The correct option is All of the above.
Water pollution control involves removing contaminants from water to make it safe for reuse or discharge back into the environment. Various physical, chemical, and biological techniques are used to achieve this. Let us examine how each of the listed techniques helps in controlling water pollution:
- Reverse osmosis: This is a membrane-based filtration method. By applying pressure greater than the osmotic pressure, water is forced through a semipermeable membrane that blocks the passage of dissolved salts, heavy metals, organic pollutants, and micro-organisms, leaving behind clean water.
- Adsorption process: In this process, pollutants (adsorbates) accumulate on the surface of a solid material (adsorbent). Activated carbon is a widely used adsorbent that effectively removes organic compounds, chlorine, odors, and toxic heavy metals from contaminated water.
- Ion exchange process: This chemical process replaces undesirable ions in wastewater with harmless ions. It is highly effective in softening hard water by exchanging calcium (Ca2+) and magnesium (Mg2+) ions with sodium (Na+) or hydrogen (H+) ions, and is also used to remove toxic heavy metals and nitrates.
Since all three methods—Reverse osmosis, Adsorption, and Ion exchange—are highly effective and widely used techniques for water pollution control, the correct choice is "All of the above".
