How Storm Sewage Contributes To Point-Source Pollution

Storm sewer systems are considered point source pollution, as defined by Section 502 (14) of the Water Quality Act of 1987. During heavy rainfall, stormwater runoff can contain nitrogen and phosphorus pollutants from fertilizers, pet and yard waste, and even heavy metals. This runoff flows directly into water bodies or storm drains without treatment, causing water pollution and unsafe drinking water. In older cities, combined sewer systems may overflow, discharging raw sewage and rainwater runoff directly into nearby water bodies, which can have detrimental effects on human health and the environment. To address this, green infrastructure techniques such as rain gardens and pervious pavement can be implemented to slow down and filter stormwater runoff.

Stormwater runoff can be worsened by human activities, containing nitrogen and phosphorus pollutants

Stormwater runoff is often exacerbated by human activities, particularly in urban and suburban areas, where there are more paved and hard surfaces. This means that, instead of being absorbed into the ground, stormwater flows over these hard surfaces directly into storm drains or nearby bodies of water. During this process, stormwater collects pollutants such as nitrogen and phosphorus from sources like fertilizers, pet and yard waste, and leaves. This is a major source of nutrient pollution, causing physical, chemical, and microbial degradation of the water.

Nitrogen and phosphorus are of particular concern in stormwater runoff due to their role in eutrophication, the onset of harmful algal blooms, and fish kills. Urbanization increases the release and transport of these pollutants from land to water, impacting environmental and water quality. To address this issue, municipalities are implementing various practices to reduce the amount of nitrogen and phosphorus entering storm drains. For example, a study in Madison, Wisconsin, found that an active leaf collection and street cleaning program reduced loads of total and dissolved phosphorus by 46% and 51%, respectively, and total and dissolved nitrogen by 42% and 52%.

Another approach to mitigating stormwater runoff is the use of green infrastructure, which helps to slow down and spread out the runoff, allowing plants to filter out pollutants as the water slowly infiltrates the ground. Examples of green infrastructure techniques include rain gardens, pervious pavement, rain barrels, and green roofs. By implementing these strategies, communities can reduce the impact of stormwater runoff on the environment and improve water quality.

Additionally, it is important to note that stormwater runoff is considered point source pollution, as defined by Section 502 (14) of the Water Quality Act of 1987. This means that the discharge of pollutants from stormwater runoff can be traced to specific sources, such as pipes, ditches, channels, or tunnels. However, it is worth mentioning that agricultural stormwater discharges and return flows from irrigated agriculture are not included in this definition.

Stormwater is untreated and can deposit pollutants directly into water bodies

Stormwater is a significant contributor to water pollution, as it can carry various pollutants directly into water bodies without undergoing treatment. During heavy rainfall or snowmelt, stormwater runoff occurs when rainwater flows over hard, impervious surfaces such as streets, parking lots, and rooftops. These surfaces divert the natural flow of rainwater, channeling it directly into storm drains, retention ponds, or ditches, or nearby water bodies.

The problem is exacerbated in urban and suburban areas, where there are extensive paved and hard surfaces. As stormwater flows across these surfaces, it picks up and mobilizes a range of contaminants, including fertilizers, pet waste, yard waste, oils, heavy metals, soaps, and other pollutants from human activities. This polluted stormwater then enters water bodies without being treated, posing a significant risk to the environment and human health.

Combined sewer systems, found in many older cities, contribute to this issue. During heavy rains, these systems can become overwhelmed, resulting in combined sewer overflow (CSO). This occurs when rainwater mixes with raw sewage, creating a mixture that is then discharged directly into the nearest water body without treatment. CSO can cause severe environmental damage and restrict activities like fishing and swimming due to unsafe water conditions.

To address stormwater runoff and sewer overflow issues, green infrastructure solutions can be implemented. These techniques slow down the runoff, allowing plants to naturally filter out pollutants as the water infiltrates the ground. Examples of green infrastructure include rain gardens, pervious pavement, rain barrels, and green roofs. Additionally, individuals can take actions to reduce their stormwater pollution footprint, such as properly disposing of pet waste and minimizing the use of fertilizers.

While stormwater discharges are legally considered point source discharges, the true sources of stormwater pollution can be traced to runoff across land surfaces. This distinction is important, as it highlights the complex nature of stormwater pollution and the need for comprehensive solutions that address both point sources and nonpoint sources of pollution. By understanding the sources and impacts of stormwater pollution, we can develop effective strategies to protect and restore the quality of our precious water bodies.

Stormwater pollution can be caused by industrial activity, construction, and municipal sewer systems

Stormwater pollution is a pressing issue that can have detrimental effects on the environment and public health. It is caused by various factors, including industrial activity, construction sites, and municipal sewer systems.

Industrial Activity

Stormwater runoff that comes into contact with exposed materials during industrial activities can contaminate water bodies. This type of pollution is regulated by permits such as the National Pollutant Discharge Elimination System (NPDES) and the Florida Multi-Sector Generic Permit for Stormwater Discharge Associated with Industrial Activity (MSGP). Industrial activities that discharge stormwater into surface waters or municipal separate storm sewer systems (MS4) are required to obtain coverage under the MSGP and implement best management practices (BMPs) to control stormwater flow and prevent pollution runoff.

Construction Sites

Construction sites are another significant source of stormwater pollution. Common pollutants include sediment, microorganisms, nutrients, heavy metals, "oxygen-demanding" wastes, and toxic chemicals such as oils and grease. Construction sites may also harbor dangerous bacteria, viruses, and parasites, which can be washed into water bodies through stormwater runoff. Fertilizers, pesticides, and other chemicals used on construction sites can contain nutrients harmful to aquatic life. Proper erosion and sediment controls, as well as implementing BMPs outlined in Stormwater Pollution Prevention Plans (SWPPPs), are essential to mitigating stormwater pollution from construction sites.

Municipal Sewer Systems

Municipal separate storm sewer systems (MS4) are designed to route sewage and stormwater into separate underground pipes. However, stormwater can pick up litter, oil, road salt, and other pollutants before flowing into streams and rivers, causing harm to water quality, fish, wildlife, and recreation. Illicit discharges, such as yard waste, can also block and clog storm drains, contributing to flooding and further water pollution. To address this issue, cities like Pittsburgh have implemented stormwater management programs to reduce pollutant discharge from MS4 systems and protect local waterways.

Sewage discharge in rivers can alter plant, animal, and microbe communities, increasing harmful species

Sewage discharge in rivers can have a detrimental impact on the environment and human health. During heavy rainfall, stormwater runoff can overwhelm combined sewer systems, causing untreated sewage to overflow directly into nearby rivers or other water bodies. This is known as a combined sewer overflow (CSO) and is considered point source pollution. While agricultural runoff can also contribute to water pollution, recent studies by the University of Oxford have found that sewage discharge has a more significant impact on river quality.

Sewage pollution, whether treated or untreated, increases the levels of nutrients, algae, and sewage fungus in rivers. This, in turn, alters the plant, animal, and microbe communities within the river ecosystems. For example, sewage input has been observed to cause a shift in macroinvertebrate and algae communities downstream, with an increase in more pollution-tolerant species such as cyanobacteria and worms.

Cyanobacteria, in particular, are known for producing toxic chemicals that can be deadly for many aquatic organisms. As a result, the increase in cyanobacteria populations due to sewage pollution has the potential to alter and degrade critical ecosystem processes by causing the loss of sensitive and critical species. For instance, certain sensitive insect groups, such as mayflies, stoneflies, and caddisflies, have been found to decline in populations due to sewage pollution.

The impact of sewage discharge on river ecosystems highlights the urgent need for improved wastewater management and stricter regulations. Early identification and intervention of sewage pollution events are crucial to prevent negative consequences for local wildlife and to safeguard the integrity and safety of rivers, which are fundamental for both ecosystems and human wellbeing. Conservation efforts must address the threat of sewage pollution to protect the biodiversity and health of aquatic ecosystems.

Farms that do not treat animal waste may allow it to enter water bodies as raw sewage

CAFOs produce a significant amount of animal waste, which, if not treated properly, can have detrimental effects on the environment and human health. The waste from these farms is often stored in large pits or lagoons and is rich in organic matter and biochemical oxygen-demanding materials (BOD). For example, swine waste slurry can contain 20,000–30,000 mg BOD/L, compared to 300–400 mg BOD/L in raw human sewage. Animal waste also carries parasites, viruses, bacteria, and pathogens that can cause illnesses and diseases in humans, such as E. coli, cryptosporidium, and salmonella.

Additionally, CAFO waste contains contaminants such as antibiotics and other veterinary drugs, heavy metals, and hormones that can enter water bodies through various pathways. These include leakage from poorly constructed manure lagoons, overflow during heavy precipitation events, and runoff from farm fields where waste has been applied. The magnitude of this environmental impact depends on factors such as soil properties, contaminant properties, and crop management practices.

The Clean Water Act established the National Pollutant Discharge Elimination System (NPDES), which requires factories, sewage treatment plants, and other point sources, including CAFOs, to obtain permits before discharging waste into any body of water. However, the regulation of CAFO waste has been largely left to individual states, with varying standards and enforcement practices.

To address the issue of stormwater runoff and combined sewer overflows (CSOs), which can also contribute to point source pollution, green infrastructure techniques can be employed. These techniques slow down and spread out stormwater, allowing plants to filter out pollutants before they enter water bodies or storm drains. Examples of green infrastructure include rain gardens, pervious pavement, rain barrels, and green roofs.

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