Water Pollutants: Understanding The Three Major Types

Water pollution is the contamination of water by pollutants, rendering it unsuitable for human use and creating a dangerous environment for aquatic life. The three major types of water pollutants are: chemicals, waste, and microorganisms. Chemicals, such as pesticides and fertilizers, can enter water sources through agricultural practices or industrial waste, causing toxic contamination. Waste, including plastics and oil spills, can physically pollute water bodies, blocking sunlight and oxygen penetration. Microorganisms like bacteria and viruses can infiltrate water supplies, causing diseases and disrupting aquatic ecosystems. These pollutants have severe consequences for both human health and aquatic life, underlining the importance of understanding and addressing water pollution.

Industrial waste

The improper treatment and direct release of industrial effluents into sewerage drains can cause irreversible damage to the ecosystem. It pollutes groundwater and other water bodies, adversely affecting the health of animals and aquatic life. Under-treated effluents can also lead to air, land surface, and soil pollution. The casual disposal of industrial wastewater used in irrigating crops can cause serious damage to crop quality and can enter the food chain.

To address these issues, adequate treatment of industrial wastewater is crucial before it is released into water bodies. This includes physical, chemical, and biological treatment methods to eliminate toxicity and recycle water for conservation. Some industries have their own specialized facilities for treating wastewater, while others send their waste to centralized waste treatment (CWT) facilities. These treatments aim to remove organic and inorganic pollutants, such as heavy metals and other harmful compounds, before the water can be safely discharged back into the environment or reused.

The impact of industrial waste on water pollution is significant, and proper management and treatment strategies are essential to mitigate its environmental and health effects.

Marine dumping

History of Marine Dumping

Communities worldwide used the ocean as a dumping ground for waste until the 1970s. This practice changed as the harmful impacts of unregulated disposal became better understood.

International Regulation

The 1972 London Convention and the 1996 London Protocol establish the global rules and standards for preventing, reducing, and controlling marine pollution caused by dumping. The United States implements these agreements through the Marine, Protection, Research, and Sanctuaries Act. The 1982 United Nations Convention on the Law of the Sea directs states to adopt laws and regulations on ocean dumping that are no less effective than the London Convention and Protocol.

Types of Waste Dumped into the Ocean

The most toxic waste materials dumped into the ocean include dredged material, industrial waste, sewage sludge, and radioactive waste. Other types of waste include medical waste, litter, and plastics.

Environmental Impact

Sewage and wastewater

Sewage refers specifically to water that has been used and then disposed of, carrying waste products and impurities. Domestic sewage, also called sanitary sewage, carries used water from houses and apartments. It is composed of slightly more than 99.9% water by weight, with the remaining less than 0.1% containing a wide variety of dissolved and suspended impurities. These impurities include putrescible organic materials, plant nutrients, and disease-causing microbes such as bacteria and viruses. Industrial sewage contains used water from manufacturing or chemical processes, and typically includes specific chemical compounds. Finally, storm sewage carries organic materials, suspended and dissolved solids, and other substances picked up from the ground.

Wastewater, or sewage, is a broader term that encompasses domestic, industrial, and storm sewage. It introduces a range of toxic contaminants, including pathogens, pharmaceuticals, microplastics, heavy metals, and endocrine disruptors. These contaminants pose a significant threat to food and water security, as well as to marine species and ecosystems. For example, untreated sewage has been linked to seagrass die-offs, harmful algal blooms, and weakened reefs.

The inadequate treatment of wastewater exacerbates the problem of water pollution. Globally, 80% of wastewater is released into the environment without adequate treatment, leading to habitat loss, extinction, and negative impacts on climate resilience, aquatic biodiversity, and food and water security. In the UK, for instance, water companies routinely discharge raw sewage into rivers and the ocean through a network of licensed sewer overflows. This has resulted in poor water quality, with only 14% of rivers meeting good environmental standards.

To address sewage and wastewater pollution, effective wastewater treatment systems are crucial. However, many existing systems are based on outdated science and inadequate policies, requiring significant reform to protect human health and the environment.

Oil leaks and spills

Oil spills are harmful to marine life and the environment. Oil on the ocean surface prevents sufficient sunlight from penetrating and reduces the level of dissolved oxygen in the water. This, in turn, affects the growth of plants and aquatic life. Oil spills can also ruin the insulating and waterproofing properties of feathers and fur, causing birds and marine mammals to die from hypothermia. Ingesting oil can be toxic to animals, and the damage to their habitat and reproductive rate may slow the long-term recovery of animal populations. Oil spills can also affect shore ecosystems such as saltwater marshes and mangroves, as well as beaches and populated shorelines, impacting tourism and commerce.

Oil spills can also contaminate freshwater sources. The average oil change uses almost five litres of oil, which can contaminate approximately 3.8 million litres of freshwater. Oil spills can occur during transportation and transfers of oil between ocean tankers, pipelines, trains, and tanker trucks. As the number of transfers increases, so does the risk of spilling oil. Regions with intense industrial operations and transportation of oil tend to have a higher number of oil spills.

Cleanup activities after an oil spill can be challenging, and it is impossible to remove 100% of the spilled oil. In some cases, the cleanup methods may cause additional harm. For example, after the Exxon Valdez oil spill in 1989, it was found that high-pressure, hot-water hoses used to clean up beaches caused more damage than the oil alone. As a result, sensitive habitats require extra consideration during oil spill cleanup. The Oil Pollution Act of 1990 established that those responsible for oil spills can be held accountable for paying for cleanup and restoration efforts.

Agricultural pollution

Water pollution is defined as the contamination of water bodies such as seas, oceans, lakes, rivers, and groundwater. Water pollution can be caused by physical, chemical, and biological changes in the properties of water. These changes are often brought about by human activities, such as the use of harmful chemicals and waste products from factories, households, and farms.

Agriculture is a major contributor to water pollution, and it is the leading cause of water degradation worldwide. In the United States, agricultural pollution is the top source of contamination in rivers and streams, the second-biggest source in wetlands, and the third main source in lakes. The use of pesticides, fertilizers, and manure in agriculture can have detrimental effects on water quality.

• Chemical Usage: Farmers often use chemicals such as pesticides, herbicides, and fertilizers to protect their crops from pests and diseases and to promote crop growth. However, these chemicals can leach into the soil and be washed into nearby water bodies by rainwater. Once in the water, these chemicals can be toxic to aquatic life and can also contaminate drinking water sources. Pesticides like neonics are particularly harmful to pollinators, and their widespread use has contributed to the decline in populations of iconic insects like the monarch butterfly and native bee species.
• Livestock and Manure Management: Livestock farming generates large amounts of manure, which can contain high levels of nutrients such as phosphorus. Improper storage and management of manure can lead to runoff, which contaminates nearby water sources. Manure also emits ammonia, which combines with other air pollutants to form harmful solid particles that can cause respiratory and cardiovascular diseases in humans.
• Nutrient Runoff: Excess nutrients from fertilizers and manure can run off into nearby water bodies, causing nutrient pollution. This includes nitrates and phosphates, which, while essential for plant growth, can be detrimental to aquatic ecosystems when present in excessive amounts. Nutrient runoff can stimulate the growth of algae and weeds in water, making it undrinkable and clogging filters. Additionally, excessive algae growth can block sunlight, disrupting the ecosystem below the water surface, and can lead to hypoxic (low oxygen) conditions that are harmful to aquatic life.
• Soil Erosion and Sedimentation: Agricultural activities can lead to soil erosion, where valuable topsoil is washed away by water or wind. This eroded soil, or sediment, is then deposited into water bodies, becoming a leading pollutant in rivers and streams. Excessive sedimentation can smother breeding areas and degrade coastal and marine ecosystems, including coral reefs.
• Water Consumption and Wastewater: Agriculture is the biggest consumer of global freshwater resources, with farming and livestock production using about 70% of the earth's surface water supplies. The high water demand of agriculture can lead to water scarcity and put pressure on already limited water resources. Additionally, wastewater from agricultural processes can contain pollutants, such as chemicals and pathogens, which, if released into water bodies, can further contribute to water pollution.

To address agricultural pollution, farmers and policymakers can implement various strategies. These include adopting nutrient management practices, such as targeted fertilizer and manure application, using drip irrigation to minimize runoff, and storing livestock manure in covered stockpiles or protected areas to reduce the risk of runoff. Additionally, contour strip cropping can be employed to reduce erosion and runoff, and software tools like the Water, Energy, and Biogeochemical Model (WEBMOD) can help monitor and improve conservation efforts.

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