Meghan Hodges
Water pollution is the contamination of water bodies, including lakes, rivers, oceans, and groundwater, with toxic substances that render it unsafe for human use and harm aquatic ecosystems. It is predominantly caused by human activities, such as industrial waste discharge, agricultural runoff, and sewage systems, which release pollutants like toxic waste, petroleum, pesticides, heavy metals, and disease-causing microorganisms into water sources. The effects of water pollution are far-reaching, endangering the health of millions worldwide and stalling economic growth, particularly in regions heavily reliant on water-based resources. With finite sources of drinkable water and increasing global demand, addressing water pollution is essential to safeguard human health and sustain social and economic development.
| Characteristics | Values |
|---|---|
| Source | Point sources (storm drain, wastewater treatment plant, oil spill) and non-point sources (agricultural runoff) |
| Contaminants | Sewage discharges, industrial activities, agricultural activities, urban runoff, stormwater, toxic substances (oil, metals, plastics, pesticides, persistent organic pollutants, industrial waste products), chemical compounds, disinfection by-products, petroleum hydrocarbons, volatile organic compounds, pathogenic organisms, heavy metals |
| Impact | Degradation of aquatic ecosystems, waterborne diseases, reduced ecosystem services, negative impact on legitimate uses of water, unpleasant for human use, destruction of natural beauty and health of lakes, rivers, and oceans, corrosion of water-handling pipes and equipment |
| Water Bodies | Lakes, rivers, oceans, aquifers, reservoirs, groundwater |
| Detection and Control | Indicator organisms, appropriate infrastructure, management plans, legislation |
| Location | Jinpen Reservoir, Shibianyu Reservoir, Zhoucun Reservoir, Zhelin Reservoir, Oujiang Estuary, Huainan coal mining areas in China |
| Water Quality Indicators | pH, arsenic, organic pollutants, TN, NH3-N, TP, CODMn, COD, TOC, TN, Cr, Zn, nitrogen, phosphorus, heavy metals, cations |
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What You'll Learn
Sewage and wastewater treatment
Wastewater treatment aims to remove contaminants and suspended solids from sewage to produce effluent that can be safely discharged into the environment or reused. This process is crucial as it reduces the amount of pollutants released into water bodies, preventing contamination and minimizing the impact on aquatic life and ecosystems. Treatment plants play a vital role in this process, ensuring that wastewater is treated before being released back into natural water systems.
There are two main types of sewage treatment systems: decentralized and centralized. Decentralized systems treat sewage close to where it is created, such as on-site sewage facilities or septic tanks. In contrast, centralized systems collect and transport sewage through a network of pipes and pump stations to a municipal treatment plant. Centralized systems are further classified into high-tech (high-cost) and low-tech (low-cost) options, as well as intensive (mechanized) and extensive (natural) systems.
The treatment process typically involves primary and secondary stages. Primary treatment removes about 60% of suspended solids and includes aerating the wastewater to restore oxygen levels. Secondary treatment is more effective, removing more than 90% of suspended solids. Advanced treatment may also incorporate a tertiary treatment stage with additional polishing processes and nutrient removal.
Despite the presence of wastewater treatment facilities, water pollution remains a significant issue. Aging and overwhelmed sewage systems can release untreated wastewater, contributing to pollution. According to the United Nations, more than 80% of the world's sewage reaches rivers and seas without proper treatment, impacting water quality and ecosystems.
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Industrial activities
Industries account for about 20% of freshwater withdrawal worldwide, and this water, used in production, becomes polluted. In some cases, it is discharged untreated into nearby public waters, contaminating rivers, lakes, and seas. The production of industrial goods generates wastewater contaminated with toxic substances, including heavy metals, oils and greases, industrial salts, and hormones. Oil refineries, chemical and plastics manufacturers, and fertilizer plants are some of the biggest culprits. For example, U.S. oil refineries discharge nearly half a billion gallons of wastewater into waterways daily, including pollutants like arsenic, mercury, and selenium.
The coal and gas industries, as well as facilities creating nuclear energy, also contribute significantly to water pollution. Accidents at nuclear energy facilities can release highly toxic uranium into the environment. Additionally, the manufacturing process in the pharmaceutical industry often produces wastewater contaminated with active pharmaceutical ingredients, such as antibiotics and hormones, which can have harmful effects on the environment and human and animal health.
While wastewater recycling systems and environmental legislation have helped reduce industrial water pollution in some regions, such as Europe and the United States, it remains a pressing issue. Industrial wastewater continues to be a significant source of pollution, and in some cases, regulations are not stringent enough or properly enforced to prevent the release of harmful substances into water bodies.
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Agricultural activities
Agriculture is a major cause of water pollution. About 40% of the land in the United States is used for agriculture, and agricultural chemicals move into and through every component of the hydrologic system, including air, soil, soil water, streams, wetlands, and groundwater.
Agricultural non-point source pollution, or pollution via runoff, is the leading source of harm to water quality for surveyed rivers and streams. It is the third-largest for lakes and the second-largest for wetlands. Non-point source pollution arises from a broad group of human activities, and the pollutants have no obvious point of entry into watercourses. In contrast, point-source pollution refers to activities where wastewater is directly routed into water bodies and can be more easily measured and controlled.
- Fertilizer use: Excess nutrients from fertilizers, such as nitrogen and phosphorus, can enter water bodies through runoff, infiltration, and irrigation return flows. These nutrients can cause eutrophication in lakes and coastal waters, impacting biodiversity and fisheries.
- Pesticide use: Pesticides are important for agriculture in the United States, and atrazine is one of the most widely used and detected pesticides in surface water. Older chlorinated agricultural pesticides have been linked to various human health issues and ecosystem dysfunction.
- Livestock and manure management: Livestock production accounts for 70% of all agricultural land and 30% of the planet's land surface. Manure management is a significant source of agricultural greenhouse gas emissions, emitting ammonia and other harmful air pollutants. Bacteria and nutrients from livestock and poultry manure can contaminate waterways and affect drinking water supplies.
- Irrigation: The area equipped for irrigation has more than doubled in recent decades, transferring agricultural pollution to water bodies.
- Aquaculture: The use of antibiotics, fungicides, and anti-fouling agents in aquaculture may contribute to polluting downstream ecosystems. Fish excreta and uneaten feeds from fed aquaculture can also diminish water quality.
- Soil erosion: Agricultural practices can lead to soil erosion, which contributes to sedimentation in water bodies, overwhelming aquatic ecosystems and degrading coastal and marine ecosystems.
To mitigate the harmful impacts of agricultural activities on water resources, diagnosis, prediction, and monitoring are key requirements. Farmers can adopt soil and water conservation practices, such as edge-of-field monitoring, nutrient management, and regenerative agriculture strategies, to reduce the runoff of pollutants and improve water quality.
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Urban runoff and stormwater
Urban stormwater runoff is a significant contributor to water pollution. It is generated from rain and snowmelt that flow over impervious surfaces, such as paved streets, parking lots, and building rooftops, without soaking into the ground. These impervious surfaces are associated with urbanization and include roads, roofs, and parking lots. Urbanization alters the natural hydrology, leading to increased surface runoff, which carries contaminants to urban streams.
The increased volume, altered patterns, and degraded quality of flow in urban stormwater runoff challenge conventional approaches to stormwater management and environmental flow assessment. The rapidity and frequency of stormwater runoff in urban areas can overwhelm sewage treatment systems, resulting in the release of untreated wastewater into water bodies.
Stormwater runoff picks up and deposits harmful pollutants, including trash, chemicals, dirt, and sediment, into streams, lakes, and groundwater. Construction sites, lawns, improperly stored hazardous wastes, and illegal dumping are all potential sources of stormwater pollutants. The pollutants can be carried into water bodies, degrading the water quality and harming aquatic ecosystems.
To address stormwater pollution, communities can employ management practices, such as implementing erosion and sediment control measures, educating homeowners and businesses on proper waste management, and using Low Impact Development (LID) and green infrastructure systems to slow down, detain, or filter contaminants from stormwater. Local governments can also play a role by using land-use controls, such as subdivision growth controls and zoning ordinances, to limit impervious surfaces and encourage open spaces.
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Microplastics and plastic pollution
Water pollution is the release of substances into bodies of water that render the water unsafe for human use and disrupt aquatic ecosystems. Plastic pollution is a significant contributor to water pollution. Plastic is the most prevalent type of marine debris found in our oceans and lakes.
Microplastics are tiny plastic particles that are less than five millimeters in length, or about the size of a pencil eraser. They can come from a variety of sources, including larger plastic pieces that have broken apart, resin pellets used for plastic manufacturing, or microbeads found in health and beauty products. These microbeads are very small pieces of manufactured polyethylene plastic that are added as exfoliants. They easily pass through water filtration systems and end up in oceans and lakes, posing a potential threat to aquatic life.
Microplastics can also be classified as primary or secondary. Primary microplastics are microscopic synthetic polymers used in various processes, such as chemical formulations and the manufacturing of synthetic clothing. Secondary microplastics are particles that result from the breakdown of larger plastic items, such as water bottles. The problem with microplastics is that they do not readily break down into harmless molecules, and can persist in the environment for hundreds or thousands of years.
The presence of microplastics in the ocean is often due to littering, but also from storms, water runoff, and winds that carry plastic and microplastics into the water. They have been detected in marine organisms of all sizes, from plankton to whales, in commercial seafood, and even in drinking water. While scientists are still unsure of the specific dangers, many countries are taking action to reduce microplastics due to their potential threat to wildlife and human health.
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Frequently asked questions
Water pollution is caused by the release of contaminants into water bodies, which can be either surface water or groundwater. The main sources of water pollution are sewage discharges, industrial activities, agricultural activities, and urban runoff including stormwater. Sewage treatment plants are a point source of pollution, but they are not the actual source as they treat the wastewater that comes from our toilets and sinks.
Water pollution has a negative impact on the uses of water bodies. It can lead to the degradation of aquatic ecosystems and the spread of water-borne diseases when people use polluted water for drinking or irrigation. Water pollution can also reduce ecosystem services, such as drinking water provided by the water resource. It can also result in economic impacts, such as stalling economic growth and exacerbating poverty in many countries.
There are some simple ways to prevent water contamination and reduce your contribution to it. You can reduce your plastic consumption and properly dispose of chemical cleaners, oils, and non-biodegradable items to keep them from going down the drain. Maintaining your car can also help prevent oil leaks, and if you have a yard, consider landscaping that reduces runoff and avoids the use of pesticides and herbicides.
