The correct answer is option 4, Reverse Osmosis. Reverse osmosis is a treatment process that uses a partially permeable membrane to remove contaminants and impurities from water. It works by applying pressure to push water molecules through the membrane, while leaving behind larger particles and pollutants. This process effectively removes dissolved salts, bacteria, viruses, heavy metals, and other harmful substances from water, making it safe for consumption or other uses.

Option 1, Bag house filter, is a technology used to control the emission of particulate matter in industrial processes, such as air pollution, but it is not specifically designed for treating water pollution.

Option 2, Windrow composting, is an organic waste management technique that involves composting organic materials, such as food waste and yard trimmings, to create nutrient-rich compost. While this process can indirectly improve water quality by diverting waste from landfills, it is not a direct treatment for water pollution.

Option 3, Venturi scrubber, is a pollution control device used to remove particulate matter and gases from gas streams. It operates by using a high-velocity liquid spray to capture pollutants, but it is not primarily used for treating water pollution.

Therefore, the correct option for the treatment of water pollution is Reverse