Water Pollution and Water Treatment

Water pollution occurs when harmful substances enter bodies of water and degrade their quality, making them unsafe for living things or for human use. Sources include sewage and waste water, runoff carrying chemicals and fertilisers from farmland, industrial discharges, and spills of oil and fuel. Contaminants such as heavy metals and persistent chemical compounds are especially troubling because they do not break down readily and can accumulate in organisms. Pollution can affect surface water in rivers, lakes, and seas as well as groundwater stored beneath the surface.

Water moves continually through the environment in the water cycle, evaporating from the surface, forming clouds, falling as precipitation, and flowing through rivers and underground back to the sea. Because water is recycled in this way and shared across regions, pollution introduced in one place can spread widely. Acid rain, formed when certain air pollutants dissolve in atmospheric moisture, is one example of how contamination of the air can reach and harm water bodies and the soils around them.

Water treatment is the set of processes used to remove contaminants and make water suitable for drinking or for safe return to the environment. Treatment of drinking water typically removes suspended particles, filters the water, and disinfects it to kill harmful microorganisms. Waste water treatment, applied to used water before it is discharged, removes solids and breaks down organic matter so that the released water does less harm to rivers and seas. Together these processes protect both public health and the ecosystems that depend on clean water.

Frequently asked questions

What causes water pollution?

Common causes include sewage and waste water, agricultural runoff, industrial discharges, and spills of oil and fuel, as well as persistent contaminants such as heavy metals.

What is the water cycle?

The water cycle is the continuous movement of water as it evaporates, forms clouds, falls as precipitation, and flows through rivers and underground back to the sea.

What does water treatment do?

Water treatment removes contaminants to make water safe to drink or safe to return to the environment, by removing particles, filtering, and disinfecting or breaking down waste.