Water pollution occurs when people overload the water environment with wastes. It's defined as contamination of streams, lakes, underground water, bays or oceans by substances harmful to living things. Water is necessary to life on earth. All organisms contain it, some drink it, and some live in it. Plants and animals require water that is moderately pure, and they cannot survive if their water is loaded with toxic chemicals or harmful microorganisms. If severe, water pollution can kill large numbers of fish, birds, and other animals, in some cases killing all members of a species in an affected area.
There are two types of water pollution; point source and nonpoint source. Point sources of pollution occur when harmful substances are put directly into a body of water (such as an oil spill). A nonpoint source is when pollutants enter the water indirectly through environmental changes (for example: fertilizer is carried into a stream by rain). The major water pollutants are chemical, biological, and physical materials that lessen the water quality.
These are some of the most important ones.
Petroleum Products – oil and chemicals from oil are used for fuel, lubrication, plastics manufacturing, and many other purposes. The petroleum products get into water by accidental spills from ships, tanker trucks, and leaky underground storage tanks. Many petroleum products are poisonous if ingested by animals and spilled oil damages the feathers of birds and the fur of animals, often causing death.
Pesticides and Herbicides – chemicals used to kill unwanted animals and plants may be carried into streams by rainwater.
The chemicals in these that are not biodegradable can remain dangerous for a long time. When an animal eats a plant that's been treated with certain non-degradable chemicals, the chemicals are absorbed into the tissues or the organs of the animals. When other animals feed on a contaminated animal, the chemicals are passed up to them. As it goes up through the food chain, the chemical becomes more harmful, so animals at the top of the food chains may suffer cancers, reproductive problems, and death. But not only animals are affected. More than 14 million Americans drink water contaminated by pesticides and the EPA estimates that ten percent of wells contain pesticides. Nitrates can cause a lethal form of anemia called blue baby syndrome in infants.
Heavy Metals – heavy metals, such as copper, lead, mercury, and selenium, get into the water from industries, automobile exhaust, mines, and natural soil. Heavy metals also become more harmful as they follow the food chain. When they reach high levels in the body, they can be immediately poisonous, or can result in long-term health problems. They can sometimes cause diarrhea and, over time, liver and kidney damage. Children exposed to lead in water can suffer mental retardation.
Excess Organic Matter – fertilizers and other nutrients used to promote plant growth on farms and in gardens may fine their way into water. At first the nutrients will help the plants and algae in the water grow, but when they die and settle underwater, microorganisms decompose them, while decomposing them the microorganisms take in oxygen that is dissolved in the water. The oxygen levels in the water may drop so low that fish and other oxygen-dependent animals in the water suffocate, and die.
There has been an awareness of these serious problems for several decades and the government passed several laws on this topic amongst which is the Clean Water Act of 1972. Since then, each state has the authority to fix limits and set standards. The ultimate goal being to make the water clean enough to support life and be safe to swim in. Unfortunately, these laws are hard and costly to enforce and as a result, a significant number of factories do not abide by the legal limits and routinely release greater amounts of toxic waste than the maximums allowed. Maybe a tougher legislation with greater penalties and more controls could help in these cases.
What we, individuals, can do however is to learn about ways for disposing harmful household wastes so they don't end up in sewage treatment plants or landfills. In our yards, we should determine whether or not we need to add nutrients before fertilizers are applied, and look for alternatives where fertilizers may run off into surface waters. We need to preserve existing trees and plant new trees and shrubs to help prevent soil erosion. Around the house we should we need to keep litter, pet waste, leaves, and grass clippings out of gutters and storm drains, and buy as many heavily packaged foods, certain boxes, cartons, bottles, etc that are made without polluting dyes.