Waterheads: Polluted By Two Major Contaminants

Watersheds are areas of land that drain water into a specific body of water, such as a stream, lake, or river. They play a crucial role in determining the quality of water in these bodies, as pollutants can wash off the land and into the water, causing substantial harm. The two main types of pollution that affect watersheds are point source pollution and non-point source pollution. Point source pollution originates from a single source, such as a manufacturer or oil refinery, and is discharged directly into a body of water. Non-point source pollution, on the other hand, comes from diffuse sources, such as agricultural or stormwater runoff, and is more challenging to regulate due to the lack of a single identifiable culprit. These types of pollution can contaminate water with harmful substances, including chemicals and microorganisms, degrading water quality and rendering it toxic to humans and the environment.

Sewage and wastewater

Sewage can be classified into greywater and blackwater. Greywater comes from sinks, bathtubs, showers, dishwashers, and clothes washers, while blackwater is the water used to flush toilets, combined with human waste. Sewage also contains soaps, detergents, food waste, and toilet paper. It is composed of around 99.9% water and the remaining 0.1% solids, which can be dissolved or suspended.

The management of sewage includes collection and transport for release into the environment after treatment compatible with local requirements. Disposal options include dilution, marine outfalls, land disposal, and sewage farms. However, all disposal options carry the risk of causing water pollution.

Wastewater treatment facilities are crucial in reducing the amount of pollutants in sewage before discharging the treated water back into waterways. These facilities help reduce pollutants such as pathogens, phosphorus, nitrogen, heavy metals, and toxic chemicals found in sewage and industrial waste.

Inadequately treated wastewater is a concern as it can introduce nutrients, pathogens, heterogeneous suspended solids, and organic fecal matter into water bodies. This can lead to the degradation of aquatic ecosystems, the spread of water-borne diseases, and a reduction in ecosystem services such as drinking water provision.

To address sewage and wastewater pollution, appropriate infrastructure, management plans, legislation, and technology solutions are necessary. Technology solutions can include improving sanitation, sewage treatment, and controlling urban runoff.

Industrial activities

• Release of toxic chemicals: Industrial processes often involve the use of toxic chemicals, such as solvents and heavy metals, which can leak or be discharged into nearby water sources. These chemicals can contaminate water, making it unsafe for human consumption and harmful to aquatic life.
• Industrial wastewater: Many industries generate large volumes of wastewater, which can contain a range of pollutants, including heavy metals, organic matter, toxins, pharmaceuticals, and endocrine-disrupting compounds. If this wastewater is not treated properly before release, it can pollute waterheads and harm aquatic ecosystems.
• Thermal pollution: Power plants and industrial manufacturers often use water as a coolant, which can result in thermal pollution. This involves a rise or drop in water temperature, altering the physical properties of water and harming aquatic organisms that are sensitive to temperature changes.
• Oil spills: While oil spills are often associated with marine environments, they can also occur on land and impact waterheads. The release of petroleum hydrocarbons can have severe environmental and economic consequences, damaging water quality and harming aquatic life.
• Volatile organic compounds (VOCs): Improper storage and handling of industrial solvents can result in VOC emissions, which can contaminate water sources. Organochlorides, such as polychlorinated biphenyls (PCBs) and trichloroethylene, are examples of VOCs that can pose significant risks to waterheads.
• Per- and polyfluoroalkyl substances (PFAS): PFAS are persistent organic pollutants released by some industrial processes. They are highly persistent in the environment and can accumulate in waterheads, posing risks to both aquatic life and human health.
• Inorganic contaminants: Industrial activities can release inorganic pollutants, such as ammonia from food processing waste and heavy metals from motor vehicles. These contaminants can find their way into waterheads, causing ecological damage and negatively impacting water quality.
• Pharmaceutical pollutants: Pharmaceutical residues in water are an emerging concern. While they may originate from various sources, including hospitals and households, industrial activities can also contribute to this issue, especially in the case of pharmaceutical manufacturing.

Agricultural activities

• Streamside vegetation removal and soil tillage: Removing vegetation from the banks of streams and rivers can increase erosion and sedimentation in water bodies. Soil tillage, the process of preparing soil for planting by ploughing and smoothing, can expose bare soil, increasing its vulnerability to surface erosion. This leads to higher levels of suspended sediment in the water, which can smother aquatic life and degrade water quality.
• Application of fertilizers and pesticides: The use of fertilizers and pesticides in agriculture is a significant source of nutrient pollution in water bodies. Excess nutrients, particularly nitrogen and phosphorus compounds, from fertilizer applications, can cause eutrophication. This leads to increased primary production, such as algal blooms, and depletion of dissolved oxygen as excess organic matter decomposes, creating "dead zones" that are harmful to aquatic life. Pesticides can also contaminate water bodies, with toxic effects that may persist for several years even after their use has been discontinued.
• Grazing practices: Livestock grazing in riparian zones, the vegetated areas alongside rivers and streams, can result in increased sediment and debris input into streams due to "hoof shear" and trampling of bank vegetation. This can lead to downcutting by the destabilized stream, a drop in the water table, loss of fisheries, and direct deposition of animal wastes into waterways.
• Irrigation practices: Irrigation of agricultural fields can impact watershed hydrology by diverting and detaining running waters and overutilizing groundwater reserves. Inefficient irrigation practices can lead to water wastage, with less than half of the diverted water actually reaching the crops. This can result in reduced streamflows, harming aquatic communities.
• Runoff from agricultural lands: Agricultural runoff is a significant source of non-point source pollution. It often contains fertilizers, pesticides, and animal waste, which can wash into nearby water bodies during rainfall or irrigation. This can lead to nutrient pollution, causing algal blooms and eutrophication, as well as the introduction of harmful pesticides and pathogens.

To mitigate the impact of agricultural activities on water pollution, it is essential to implement best management practices (BMPs). These practices include retaining naturally vegetated buffer strips along streams, conservation tillage, crop nutrient management, and effective pest and weed management. By following these practices, farmers can minimize their impact on water quality while still maintaining agricultural production.

Oil leaks and spills

The impact of oil spills on aquatic ecosystems is significant. Oil on the ocean's surface inhibits sunlight penetration and reduces dissolved oxygen levels, affecting aquatic life. It also damages the insulating and waterproofing properties of birds' and marine mammals' feathers and fur, leading to hypothermia. Ingesting oil can be toxic to these animals, and the damage to their habitats and reproductive rates may slow their populations' long-term recovery. Oil spills also harm plant life, such as saltwater marshes and mangroves.

The economic consequences of oil spills are substantial. Tourism and commerce may suffer if beaches and populated shorelines are affected. Power plants and other utilities that rely on or discharge into seawater may also be impacted. One of the industries most affected is fishing, which often faces immediate suspension following major oil spills to prevent damage to equipment and contamination of catch.

The long-term ecological impact of oil spills is challenging to assess. However, the high cost of compensation for individuals and communities affected by oil spills has been a significant incentive to reduce the likelihood of future occurrences.

Several methods are employed to clean up oil spills, including containment with floating booms, skimming, the use of sorbents, chemical dispersants, and burning. Natural processes, such as biodegradation, where microorganisms break down hydrocarbons, also play a role in remediation.

To reduce the amount of oil polluting water sources, measures such as the United Nations MARPOL treaty have been implemented. This treaty mandates the use of oil-pollution prevention equipment, such as double hulls on ships, and reliable navigation and communication systems. These efforts have contributed to a notable reduction in oil spills. However, there is still progress to be made, particularly in raising awareness about the proper disposal of oil, paint, and hazardous chemicals.

Urban runoff

During rain, storms, and other precipitation events, these impervious surfaces, along with rooftops, transport polluted stormwater laden with contaminants. This includes gasoline, motor oil, heavy metals, trash, fertilizers, and pesticides, which can have detrimental effects on the environment and human health. Roads and parking lots are significant sources of polycyclic aromatic hydrocarbons (PAHs) and heavy metals such as nickel, copper, zinc, cadmium, and lead. Roof runoff also contributes high levels of synthetic organic compounds and zinc from galvanized gutters.

The improper application of fertilizers or over-fertilization of residential lawns, parks, and golf courses is another concern. It leads to increased levels of nitrates and phosphorus in urban runoff, further degrading water quality. Eroding soils or poorly maintained construction sites can exacerbate the problem, leading to increased sedimentation in runoff, which can directly impact aquatic ecosystems and human health.

The natural sediment load discharged to receiving waters decreases as stormwater is channelled into storm drains and surface waters, but the water flow and velocity increase. This increased flow can cause stream bank erosion, flooding, and property damage. Additionally, the higher temperatures in streams harm fish and other organisms, and the use of road salt to melt snow can further contaminate streams and groundwater aquifers.

One of the most significant impacts of urban runoff is on watercourses that typically have little or no water during dry weather periods, often called ephemeral streams. Urbanization around these streams leads to unnatural year-round streamflow, damaging vegetation, wildlife, and the stream bed. Eutrophication often occurs in these waterways due to the presence of fertilizer and organic waste in the runoff, leading to deadly consequences for fish and other aquatic organisms.

To address the issues caused by urban runoff, effective control measures are necessary. These include reducing the velocity and flow of stormwater, implementing pollution prevention practices, and utilizing runoff mitigation systems such as infiltration basins and bioretention systems. Local governments employ various stormwater management techniques, known as best management practices for water pollution (BMPs), to minimize the adverse effects of urban runoff on the environment and human health.

Frequently asked questions