Water Pollution Uses and Effects
Water pollution occurs when water bodies like rivers, lakes, oceans and groundwater aquifers are polluted with chemicals. Chemical contaminants include sewage spills, chemical cleaners and automotive oil. Chemical pollutants such as chlorinated solvents and Freons sink in water, while other pollutants like nitrates and phosphates can form sheens on the surface of the water.
Most industries use water in their production processes and produce a substantial amount of wastewater. This is known as industrial effluent and it can pollute water. Industrial effluent can contain organic pollutants like pesticides, solvents, dissolved residue from food processing and leather tanning or inorganic contaminants such as brine salts.
Chemicals from the smelting industry, nuclear power plants and metal refineries are common sources of industrial wastewater. Fossil fuel power plants typically discharge wastewater containing high levels of toxic metals such as lead, mercury, cadmium and arsenic.
Oils, acids and alkalis from the automotive industry are other sources of industrial wastewater. These contaminants can contaminate the water with harmful chemicals and cause a variety of problems including corrosion, blockage of pipes and water logging. The total dissolved solids (TDS) value of industrial wastewater can also be extremely high. This raises the density of the water, influences osmoregulation of fresh water organisms and reduces the solubility of gases (like oxygen) in the water.
The oil pollution we see most often results from tankers, drilling rigs and barges at sea or pipelines on land that break or leak. These accidents are usually due to mechanical failure, human error or deliberate acts by terrorists, countries at war or vandals.
Because petroleum products don’t mix well with water, spilled oils float on the surface of the water and form large, thick slicks that are difficult to clean up. To make them more manageable, cleanup workers spread dispersants over slicks to break them into small droplets that can be more easily degraded by sunlight and bacteria.
When a spill reaches open, sandy beaches or rocky shores, people use booms and skimmers to remove the oil from the water. They also apply sorbents, such as straw, volcanic ash or shavings of polyester-derived plastic, to soak up the oil before it can be washed away by waves or by tides. In a marine ecosystem, an oil spill is a serious problem that can kill fish and wildlife and damage corals.
Pesticides are chemicals that kill or control pests such as insects, mice and other rodents, unwanted plants (herbicides), fungi and bacteria. They are widely used in agriculture, around homes and businesses, on lawns, gardens and in recreational areas. There are hundreds of different pesticide chemicals in use. Some can be toxic to fish, wildlife and humans, and others can contaminate surface water and groundwater.
Runoff and erosion are the main ways that pesticides reach the water. Some of them bind tightly to the soil particles, and when the soil is eroded by storms or flood waters they are carried downstream and may contaminate surface water sources. Other pesticides are more water-soluble and leach into the groundwater.
The low activities of drug-metabolizing enzymes in aquatic mammals make them especially susceptible to high concentrations of contaminants. As a result, the dolphins living in riverine ecosystems have been found to accumulate organochlorines at levels above United States Environmental Protection Agency standards.
The natural water cycle helps to make life on Earth possible, but excessive greenhouse gas emissions are disrupting that process. Warming temperatures alter rainfall patterns, accelerate soil erosion and lead to increased flooding, drought and wildfires. In addition, they melt ice caps and glaciers and cause ocean levels to rise, which threatens coastal communities, harms fisheries and leads to the loss of freshwater supplies for millions of people.
Unsafe water sickens a billion people every year, with low-income populations at greater risk. Pathogens in unsafe water can cause illnesses like cholera, giardia and typhoid. In the United States, accidental or illegal releases of pathogens from sewage treatment plants and runoff from farms and cities contribute to water pollution.
Eutrophication of inland waters can increase nutrient concentrations and drive global climate change through methane (CH4) emissions. The present value of avoided damages from preventing further eutrophication is estimated to be $0.66-24 trillion in 2050. Moreover, a decrease in CH4 emissions will reduce the damage from other forms of water pollution.