Surface Water Pollution: Causes And Human Impact

Surface water pollution is a pressing global issue that poses a threat to human health, ecosystems, and economic activities. It refers to the contamination of surface water bodies, such as rivers, lakes, and oceans, by human activities or natural factors. The leading causes of surface water pollution include agricultural runoff, sewage leaks, and waste products from farms, as well as industrial activities and urban stormwater runoff. These sources introduce harmful chemicals, fertilizers, pesticides, and pathogens into water bodies, endangering aquatic life and rendering water unsafe for human consumption. Effective monitoring, control, and management are crucial to address this challenge and ensure a sustainable future with clean surface water supplies.

Industrial and agricultural wastewater

Agricultural Wastewater

Agricultural activities discharge a significant amount of wastewater, which can be a source of both point and non-point source pollution. Non-point source pollution, also known as "diffuse" source pollution, is harder to identify, measure, and control as it arises from a broad range of human activities with no obvious point of entry into water bodies. Examples of non-point source pollution in agriculture include nutrient pollution from excess nitrogen and phosphorus, as well as pesticide residues, which can contaminate both surface and groundwater. According to the 2017 National Water Quality Inventory of the Environmental Protection Agency (EPA), 46% of the US's rivers and streams are in "poor biological condition" due to high levels of nutrients and algae, which degrade water quality.

Agricultural runoff, or irrigation tailwater, is another major source of water pollution. When excess water runs off fields during surface irrigation, it carries sediments, nutrients, agrochemicals, and animal waste into nearby water sources. This type of runoff is a primary cause of sediment and nutrient pollution, which can lead to eutrophication and ecosystem damage. Intense cultivation and "factory" livestock operations have been identified as significant contributors to surface and groundwater pollution, with agriculture being the leading source of phosphorus compounds and sediment in Mediterranean countries.

Other sources of agricultural wastewater pollution include the use of fertilizers, pesticides, herbicides, crop residues, and dairy farming waste. These agrochemicals can contaminate both surface and groundwater, impacting the quality of water used for drinking and irrigation.

Industrial Wastewater

Industrial activities also generate a significant amount of wastewater, which can contain a range of contaminants. Industrial wastewater includes water released during manufacturing, cleaning, and other commercial activities. The nature of the contaminants present depends on the type of industry, but can include non-biodegradable waste such as heavy metals, pesticides, plastics, and other toxic substances.

Improper treatment and direct release of industrial effluents into sewerage drains can cause irreversible damage to groundwater and other major water bodies. This type of pollution is known as point source pollution, where contamination originates from a single source, such as a manufacturer, oil refinery, or wastewater treatment facility. Point source pollution can affect miles of waterways and oceans, even when the contamination comes from a specific place.

The increase in industrialization and population growth has led to a rise in industrial waste, which, without proper treatment and management strategies, can have devastating environmental and health consequences.

Sewage and septic systems

Sewage systems are a major source of surface water pollution. Wastewater from households, communities, and industries is treated at sewage treatment plants before being discharged into waterways. However, ageing infrastructure, poor planning, and increasing populations contribute to the problem of sewage pollution. During heavy rain or flooding, the surge in stormwater can overwhelm sewer systems, leading to overflows and the release of untreated sewage into rivers, lakes, and oceans. This untreated sewage contains harmful bacteria, viruses, parasites, chemicals, and nutrients that pose risks to human health and ecosystems.

Septic systems are commonly used for wastewater treatment, particularly in rural and suburban areas. When functioning properly, septic systems treat wastewater by allowing solids to settle and digesting sewage sludge with bacteria. The liquid effluent then flows into a drain field or leaching pool, eventually percolating through the soil to join groundwater and surface water. However, if a septic system is not properly designed, installed, or maintained, it can contaminate nearby water sources with untreated wastewater.

A failing septic system can discharge untreated wastewater containing pathogens (e.g., E. coli), nutrients, and other harmful substances directly into the ground or surface waters. This contamination poses a direct health hazard to anyone exposed, including children and pets, and can cause illnesses with gastrointestinal, dermatological, and flu-like symptoms. Additionally, excessive nitrogen discharges from septic systems can contaminate coastal waters, fuelling harmful algal blooms that put human health at risk and harm aquatic life.

To mitigate the impact of septic systems on surface water, proper maintenance is crucial. This includes practices such as annual inspections and regular pumping. Additionally, new septic technologies can remove a significant portion of nitrogen from wastewater and are better suited to coastal areas with high water tables. Connecting homes and businesses to centralised sewers and sewage treatment plants is preferred, as septic systems are more vulnerable to climate change impacts like sea level rise and increased storm events.

Upgrading and maintaining sewage treatment plants are essential to reducing sewage pollution. However, this requires significant investment and time. In the meantime, communities can implement natural solutions, such as planting trees, restoring wetlands, and creating green roofs, to expand the capacity of sewer systems and prevent overflows. These nature-based solutions not only help manage stormwater but also offer a cost-effective approach to enhancing water quality.

Oil and chemical spills

Oil spills in water can result from the release of crude oil from tankers, offshore platforms, drilling rigs, and wells. They may also involve spills of refined petroleum products, such as gasoline and diesel fuel, as well as heavier fuels used by large ships, and any oily refuse or waste oil. Oil spills on roads, flushed into the oceans during rainstorms, are another example of land-based spills. These spills can have devastating and long-lasting effects on the environment, wildlife, and local economies.

The impact of oil spills on marine life is profound. It can result in the death or injury of sea creatures, including birds, sea mammals, fish, algae, and coral. Oil penetrates the feathers and fur of these animals, reducing their ability to insulate, and making them more susceptible to temperature changes and hypothermia. Oil also sinks below the water's surface, and if swallowed by fish, makes them unsafe for human consumption, leading to massive economic losses for the fishing industry.

Chemical spills, along with oil spills, are a significant concern for coastal waterways and estuaries. They can kill wildlife, destroy habitats, and contaminate critical resources in the food chain. These spills can originate from farms, factories, and cities, and are carried by streams and rivers into bays and estuaries, eventually reaching the sea.

The cleanup and recovery process for oil and chemical spills is challenging and expensive. While various methods exist, including physical and chemical remediation, they can never completely remove all traces of the spill. In some cases, cleanup activities can cause additional harm to the environment, as seen in the aftermath of the Exxon Valdez oil spill in 1989.

To manage and respond to oil and chemical spills, organizations like the National Oceanic and Atmospheric Administration (NOAA) utilize satellite technology, glider technology, and high-frequency radar technology to monitor and track spills. The Oil Pollution Act of 1990 also established that those responsible for oil spills can be held accountable for the cleanup and restoration costs.

Stormwater runoff

The impact of stormwater runoff on water quality is significant. As the polluted stormwater enters storm drains and ditches, it carries these contaminants with it, leading to the degradation of aquatic ecosystems. The nutrients, chemicals, and pathogens in the stormwater can cause algal blooms, eutrophication, and the spread of waterborne diseases, posing risks to both human health and the environment.

One of the key challenges with stormwater runoff is that it originates from numerous small, individual sources within a watershed. This nonpoint source pollution makes it difficult to regulate and manage compared to point source pollution, which comes from a single, identifiable source. However, it is important to note that residents and communities can play a crucial role in reducing stormwater pollution by making small changes to their everyday activities.

To mitigate the effects of stormwater runoff, it is essential to implement measures that prevent pollutants from entering water bodies. This can include maintaining vehicles, properly disposing of waste oils and other fluids, and recycling antifreeze. Additionally, residents can be mindful of washing their cars in commercial car washes or on lawns instead of in the street or driveways, as this helps reduce the amount of polluted water entering storm drains.

Another effective strategy to combat stormwater runoff is to increase the presence of vegetated land cover in residential areas. This can be achieved by replacing part of lawns with native, drought-resistant plants, adding compost and mulch to planting soil, and reducing impervious surfaces. These steps help to slow down and absorb stormwater, reducing the amount of runoff and allowing natural filtration processes to occur.

Fertilizers and pesticides

Agricultural Runoff

Agricultural activities, such as irrigation, manure application, and pesticide use, can contribute to surface water pollution. When excess fertilizers or manure are applied to fields, heavy rainfall or irrigation can wash them off the soil, leading to runoff that carries these pollutants into nearby water bodies. This runoff can contain high levels of nutrients, particularly nitrogen and phosphorus, which can cause eutrophication in water bodies, leading to algae blooms and depletion of oxygen, creating "dead zones" where aquatic life cannot survive.

Pesticide Leaching and Mobility

Pesticides applied to fields can also be carried away by water molecules during precipitation events, percolating downward into soil layers and eventually reaching groundwater and, in some cases, surface waters. This process is influenced by factors such as the amount of pesticide applied, the application method, solubility, and the strength of its bond with the soil. Pesticides with higher water solubility, such as organophosphates, are more likely to be transported to water bodies. Additionally, certain pesticides can bind strongly to soil particles, making them immobile, while others, like pyrethroids, can attach to soil particles and be carried by wind or water into waterways.

Point Source Pollution

Point source pollution occurs when pesticides and fertilizers are improperly stored, loaded, disposed of, or spilled. This includes chemical runoff during misapplication to water bodies and spills or illegal dumping into storm drains, which are intended to carry clean water. These contaminants can then enter surface waters, impacting aquatic ecosystems and water quality.

Non-Point Source Pollution

Non-point source pollution refers to the gradual leaching of pesticides and fertilizers from large areas, such as agricultural fields, across watersheds, eventually reaching water bodies. This type of pollution is influenced by factors such as improper land use management techniques, excessive fertilizer or pesticide application, and erosion events.

Health and Environmental Impacts

Surface water pollution caused by fertilizers and pesticides has significant health and environmental consequences. Contamination of drinking water sources with pesticides and fertilizers can pose serious health risks, especially to young children. Additionally, aquatic ecosystems are highly vulnerable to these pollutants. Aquatic invertebrates, which are essential to the aquatic food chain, are particularly susceptible to pesticide and fertilizer runoff. The presence of these chemicals in water bodies can also impact fish diversity and survival, as well as alter the genetic characteristics of amphibians, as evidenced by the feminization of male frogs exposed to atrazine.

Frequently asked questions