As Earth’s population continues to grow, people are putting water pollution control pdf-increasing pressure on the planet’s water resources. In a sense, our oceans, rivers, and other inland waters are being “squeezed” by human activities—not so they take up less room, but so their quality is reduced.

19th century Industrial Revolution, people lived more in harmony with their immediate environment. As industrialization has spread around the globe, so the problem of pollution has spread with it. When Earth’s population was much smaller, no one believed pollution would ever present a serious problem. It was once popularly believed that the oceans were far too big to pollute. According to the environmental campaign organization WWF: “Pollution from toxic chemicals threatens life on this planet. Every ocean and every continent, from the tropics to the once-pristine polar regions, is contaminated.

Photo: Detergent pollution entering a river. Water pollution can be defined in many ways. Usually, it means one or more substances have built up in water to such an extent that they cause problems for animals or people. Oceans, lakes, rivers, and other inland waters can naturally clean up a certain amount of pollution by dispersing it harmlessly. If you poured a cup of black ink into a river, the ink would quickly disappear into the river’s much larger volume of clean water. Photo: Pollution means adding substances to the environment that don’t belong there—like the air pollution from this smokestack. Pollution is not always as obvious as this, however.

Sewage is a completely natural substance that should be broken down harmlessly in the environment: 90 percent of sewage is water. Chemical fertilizers used by farmers also add nutrients to the soil, and they work together as a team. The oil can wash up on nearby beaches, destroying the environment ultimately reduces the quality of our own lives, around 5 million tons of sewage was dumped by barge from New York City each year. They were once widely used to manufacture electronic circuit boards — a spill from an oil tanker creates an oil slick that can affect a vast area of the ocean.

A small quantity of a toxic chemical may have little impact if it is spilled into the ocean from a ship. But the same amount of the same chemical can have a much bigger impact pumped into a lake or river, where there is less clean water to disperse it. Water pollution almost always means that some damage has been done to an ocean, river, lake, or other water source. Fortunately, Earth is forgiving and damage from water pollution is often reversible. What are the main types of water pollution?

When we think of Earth’s water resources, we think of huge oceans, lakes, and rivers. The most obvious type of water pollution affects surface waters. For example, a spill from an oil tanker creates an oil slick that can affect a vast area of the ocean. Not all of Earth’s water sits on its surface, however. A great deal of water is held in underground rock structures known as aquifers, which we cannot see and seldom think about. Aquifers feed our rivers and supply much of our drinking water.

They too can become polluted, for example, when weed killers used in people’s gardens drain into the ground. Groundwater pollution is much less obvious than surface-water pollution, but is no less of a problem. In 1996, a study in Iowa in the United States found that over half the state’s groundwater wells were contaminated with weed killers. Surface waters and groundwater are the two types of water resources that pollution affects. There are also two different ways in which pollution can occur. A great deal of water pollution happens not from one single source but from many different scattered sources. Photo: Above: Point-source pollution comes from a single, well-defined place such as this pipe.

Below: Nonpoint-source pollution comes from many sources. All the industrial plants alongside a river and the ships that service them may be polluting the river collectively. When point-source pollution enters the environment, the place most affected is usually the area immediately around the source. For example, when a tanker accident occurs, the oil slick is concentrated around the tanker itself and, in the right ocean conditions, the pollution disperses the further away from the tanker you go. This is less likely to happen with nonpoint source pollution which, by definition, enters the environment from many different places at once. Sometimes pollution that enters the environment in one place has an effect hundreds or even thousands of miles away. One example is the way radioactive waste travels through the oceans from nuclear reprocessing plants in England and France to nearby countries such as Ireland and Norway.