Water Pollution: Understanding The Various Causal Agents

Water pollution is a pressing issue that poses a threat to human health and the environment. It occurs when harmful substances contaminate water bodies, degrading water quality and rendering it unsafe for human use and aquatic ecosystems. The main agents of water pollution can be categorised into two types: point sources and non-point sources. Point sources refer to specific identifiable causes, such as industrial activities, sewage discharges, and oil spills, while non-point sources are more diffuse, including agricultural runoff and atmospheric pollution from industries and power plants. These sources introduce a range of contaminants into water, including toxic chemicals, waste, plastics, fertilisers, pesticides, microorganisms, and even radioactive substances. The contamination of water has severe consequences, including the destruction of biodiversity, the spread of water-borne diseases, and economic impacts on regions dependent on water-related activities.

Characteristics and Values of the Agents of Water Pollution

Industrial activities

Asbestos, a carcinogenic pollutant, can be inhaled, leading to serious illnesses such as asbestosis, mesothelioma, lung cancer, intestinal cancer, and liver cancer. Lead, a metallic element, is non-biodegradable and harmful to human and animal health. Similarly, mercury, another metallic element, is challenging to clean up and can cause mercury poisoning in animals.

Agricultural runoff, which includes nitrates and phosphates from increased fertilizer use, contributes to eutrophication in marine environments. Eutrophication occurs when excessive nutrients stimulate plant and algae growth, reducing oxygen levels in the water and creating "dead zones" where aquatic life cannot survive. Sulphur, a non-metallic substance, is also harmful to marine life.

Oils and petrochemicals, derived from gas or petrol, pose additional threats to marine ecosystems. Oil spills form a thick layer on the water's surface, blocking light necessary for marine plant photosynthesis and harming fish and marine birds. Petrochemicals are toxic to marine life and can have detrimental effects on their lifespan and reproductive abilities.

Other industrial waste includes cafeteria garbage, dirt, gravel, masonry, concrete, scrap metals, solvents, chemicals, and organic matter. These contaminants can enter water bodies directly or through stormwater runoff, further degrading water quality.

To address this issue, the Ministry of Environment in each province regulates the discharge of solid, liquid, and gaseous wastes from industrial sources. They develop policies, conduct compliance activities, and leverage new technologies for separation and recycling to mitigate the impact of industrial activities on water pollution.

Sewage treatment plants

The sewage treated at these plants comes from households, businesses, and sometimes pre-treated industrial wastewater. It undergoes several stages of treatment, including primary, secondary, and tertiary treatment, to remove solids, reduce organic matter, and further improve effluent quality. The treated wastewater is then disinfected before being discharged into local water bodies or the ocean, where it can become a source of nitrogen and phosphorus pollution.

In the primary treatment stage, sewage is separated into liquid and solids, resulting in a liquid with a significantly reduced concentration of pollutants. Secondary treatment uses pure oxygen to stimulate the growth of microorganisms that break down organic material, followed by a second round of settling tanks to separate the microorganisms from the purified water. Tertiary treatment serves as a final stage to enhance the effluent's quality before discharge or reuse.

While sewage treatment plants aim to minimize water pollution, they can still contribute to it. The discharge of treated wastewater can introduce nitrogen and phosphorus into local water bodies, leading to nutrient pollution. Additionally, the early stages of sewage treatment can produce foul-smelling gases, requiring odor control measures in urban areas to mitigate their impact on nearby populations.

The optimization of sewage treatment plants is crucial to enhance their effectiveness in reducing pollution. Upgrades and technology advancements, such as nutrient removal technology, can help achieve nutrient reduction goals and improve the overall quality of treated effluent. By implementing various strategies and adhering to stringent discharge standards, sewage treatment plants play a vital role in mitigating water pollution and protecting both human health and aquatic ecosystems.

Agricultural activities

Agriculture is the leading cause of water degradation worldwide. The sector is responsible for 70% of water withdrawals globally, making it the single largest user of freshwater.

Agricultural pollution is often caused by small-scale family-sized farming, which is considered non-point-source pollution. This type of pollution is challenging to control because it comes from a broad unconfined area, such as the runoff from agricultural land.

Another way that agriculture contributes to water pollution is through the discharge of pollutants and sediments to surface and/or groundwater. Poor agricultural practices, such as net loss of soil, salinization, and waterlogging of irrigated land, can also lead to water pollution.

The use of wastewater and polluted surface and groundwater in agriculture can contaminate crops and transmit diseases to consumers and farm workers. This is particularly common in high-income countries and emerging economies, where agricultural pollution has overtaken contamination from settlements and industries as the main factor in the degradation of inland and coastal waters.

Urban runoff

One of the key challenges in managing urban runoff is the difficulty in controlling dispersed or non-point sources of pollution. Unlike point sources, where contaminated water is collected and treated at a single point, dispersed sources originate from broad areas, such as agricultural runoff, making it harder to address. The US National Research Council's 2009 report highlighted the need to address land-use changes that contribute to diffuse sources of pollution, as they pose significant challenges to restoring water bodies and aquatic ecosystems.

The effects of urban runoff extend beyond water pollution, as it is also a major cause of urban flooding. Urban flooding occurs when rainfall exceeds the capacity of drainage systems, leading to repetitive and costly impacts on communities, even in areas not typically prone to flooding. To mitigate the risks associated with urban runoff, various strategies can be employed, such as implementing additional flooding drains or exploring alternative flood-prevention methods in high-risk areas. Regular testing and monitoring of water quality are crucial for early problem identification, enabling local authorities and water companies to take appropriate action to maintain water safety.

Oil spills

One notable example of an oil spill is the Deepwater Horizon incident in 2010, which was the largest oil spill in U.S. waters. While technologies for drilling in deep water have improved, oil companies are moving to more challenging drilling sites, making it difficult to determine the frequency of offshore oil platform spills. Pipeline oil spills, caused by fishing boat trawling, natural disasters, pipe corrosion, construction defects, or sabotage, contribute to about 1% of oil pollution in the oceans.

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