Organic Waste: Water Pollution's Unseen Threat

Water pollution is a pressing issue that affects aquatic ecosystems and humans worldwide. Organic waste is a significant contributor to water pollution, and it can enter water bodies through various pathways, including agricultural runoff, sewage discharges, and leachate from landfills. The decomposition of organic waste in water leads to increased oxygen consumption, which can deplete oxygen levels and endanger aquatic life. Additionally, organic waste can contribute to eutrophication, promoting excessive growth of algae and phytoplankton, further reducing oxygen levels and causing harm to aquatic ecosystems. The presence of organic waste in water can also facilitate the release of harmful chemicals, impacting the health of both wildlife and humans.

Domestic sewage discharges

Domestic sewage, also known as domestic wastewater or municipal wastewater, is a type of wastewater generated by a community of people. It includes wastewater from residences, as well as commercial, institutional, and public facilities within a locality. Sewage consists of various components, including greywater from sinks, bathtubs, showers, dishwashers, and clothes washers, and blackwater, which is the water used to flush toilets, combined with human waste. Sewage also contains soaps, detergents, food waste, toilet paper, and municipal solid waste.

The management of domestic sewage typically involves collection and transport through a sewer system for release into the environment after treatment. The treatment level must comply with local requirements for discharge into water bodies, soil, or reuse applications. However, it is important to note that all disposal options carry a risk of causing water pollution.

Furthermore, domestic sewage can infiltrate and exfiltrate from sewer systems, especially older ones in need of rehabilitation. Infiltration increases with factors such as the length of the collection network, pipeline diameters, drainage area, and age of the sewer. Exfiltration occurs when sewage leaks from aging sewer joints and connections, polluting groundwater. Combined sewer systems, which mix sewage and stormwater, can also contribute to water pollution during heavy rainfall or snowmelt by discharging untreated sewage into nearby water bodies.

The Environmental Protection Agency (EPA) plays a crucial role in monitoring water quality and regulating sewage discharges in the United States. Under the Clean Water Act, municipal wastewater treatment plants must obtain permits to discharge pollutants into water bodies. However, there have been instances where facilities have exceeded their permit limits or illegally dumped significant amounts of pollution, emphasizing the need for improved compliance and monitoring to protect public health and water quality.

Eutrophication

Organic waste can cause water pollution, which in turn can lead to eutrophication. Eutrophication is a process in which nutrients, such as nitrogen and phosphorus, accumulate in a body of water, resulting in increased growth of organisms that can deplete the oxygen in the water. This can lead to substantial environmental degradation and negatively impact both people and ecosystems.

Nonpoint sources of pollution, such as agricultural runoff, are the primary contributors to eutrophication. Excessive nutrient concentrations, particularly phosphates and nitrates, from fertilizers and animal wastes, can enter water bodies through runoff. Atmospheric deposition of nitrogen from the combustion of fuels also contributes to nitrogen pollution. Additionally, wastewater discharge from urbanization and livestock farming intensification can further increase nutrient loads in water bodies.

To prevent and mitigate eutrophication, it is crucial to minimize point and nonpoint source pollution. This can be achieved through nutrient management techniques, such as applying fertilizers correctly and using organically fertilized fields. Waste disposal technology and cooperation between organizations are also important factors in eutrophication prevention. Additionally, introducing bacteria and algae-inhibiting organisms, such as shellfish and seaweed, can help reduce nitrogen pollution and control the growth of cyanobacteria.

Urbanisation

The impact of urbanisation on water pollution is a growing concern, particularly in the context of the 21st century, when most of the global population will live in urban areas. This shift towards urban living will result in an increased use of freshwater resources, with more competition for water between cities and agriculture. The concentration of people in cities will also result in more urban waste, which is likely to contaminate water with multiple pollutants. These pollutants include nutrients, pathogens from human excretion, plastics, and chemicals from personal care products.

The issue of wastewater is central to the discussion of urbanisation and water pollution. As the number of people living in urban areas with sewer connections increases, so does the demand for wastewater treatment plants. However, in many cases, the construction of these plants lags, and wastewater is discharged into rivers and other water bodies without proper treatment. This untreated wastewater contains a range of pollutants that can have detrimental effects on both human and aquatic life. For example, chemicals commonly used in conventional farming, such as the herbicide atrazine, can leach into groundwater and contaminate drinking water supplies.

The effects of urbanisation-related water pollution are already being felt around the world. River pollution in Europe, Southeast Asia, and North America is severe, and it is projected that by 2050, around 80% of the global population will live in sub-basins with multi-pollutant problems. The situation is even more dire in Africa, where future river pollution is expected to be significantly higher than in 2010. This will make it extremely challenging for the continent to meet its Sustainable Development Goals, particularly those related to clean water and sustainable cities.

While urbanisation poses significant challenges to water quality, there are also opportunities for improvement. Reusing wastewater, for example, can lead to less pollution, more water conservation, and additional water for recharging aquifers. Safe wastewater treatment in urban areas can have positive impacts on public and environmental health, and new storm-drainage systems can reduce flooding during storms, causing less damage to properties and streets. Implementing sustainable practices and technologies, such as those outlined in the New Urban Agenda, is crucial to addressing the water pollution challenges posed by urbanisation and ensuring the protection of public health and the environment.

Livestock farming

Organic waste can cause water pollution, and one of the sources of this pollution is livestock farming.

Livestock production is a source of multiple pollutants in rivers. The most common contaminants from livestock waste are nutrients, pathogens, veterinary pharmaceuticals, heavy metals, and naturally excreted hormones. The presence of these contaminants has been documented in both surface water and groundwater supplies in agricultural areas.

Cattle, pigs, and chickens are responsible for 74-88% of these pollutants in rivers. In a study of the Kaunas region, pig farms were found to affect surface water quality more than livestock farms. As the number of livestock units increased, the pH decreased, and the levels of suspended materials, nitrates, and phosphates increased in the surface water.

The growth of concentrated animal feeding operations (CAFOs) presents an increased risk to water quality due to the higher volume of waste and the presence of contaminants such as antibiotics and other veterinary drugs. These contaminants can enter the environment through leakage from poorly constructed manure lagoons, overflow during precipitation events, runoff from waste applications to farm fields, or atmospheric deposition.

To improve water quality, it is essential to take a multi-pollutant perspective when assessing water pollution from livestock production. By focusing on specific pollutants such as nitrogen, phosphorus, and Cryptosporidium (a pathogen), effective manure management practices can be implemented for individual livestock species in sub-basins to reduce multiple pollutants in rivers.

Climate change

Organic waste is a significant source of water pollution, and climate change is a contributing factor. Firstly, organic waste increases oxygen consumption in water, which is detrimental to aquatic life. As oxygen levels deplete, aquatic life in the stream will die. This process is known as eutrophication, where a lake or stream transitions from a clean, clear state to an oxygen-deficient, waste-filled environment. Climate change impacts this process by reducing the dilution capacity of rivers, further exacerbating the effects of organic pollution.

Secondly, organic waste can lead to secondary problems such as eutrophication, which is driven by phosphate and nitrate compounds. Excessive nutrients in water promote the growth of algae, sometimes resulting in algal blooms. When algae decompose, they consume oxygen, and the subsequent release of gases like methane and hydrogen sulfide harms aerobic life forms. Climate change, in this case, intensifies the issue by increasing wastewater discharge, which contributes to higher nutrient loads in water bodies.

The sources of organic waste contributing to water pollution include domestic sewage, food waste, animal and human excreta, and industrial activities such as food processing. Sewage containing organic waste, when disposed of in water bodies, poses a significant threat to aquatic ecosystems. The decomposition of organic matter by bacteria and other microorganisms depletes oxygen levels, endangering fish and other aquatic organisms. Climate change, in the context of sewage, can impact the effectiveness of wastewater treatment processes, which may not keep pace with increasing pollution levels.

Additionally, climate change interacts with other factors such as urbanization and livestock farming to worsen water pollution. Intensification of livestock farming, driven by increasing demand, leads to higher volumes of wastewater discharge, which can overwhelm natural degradation and dilution processes in rivers. Similarly, urbanization increases wastewater discharge, further contributing to organic river pollution. The combined effects of these factors, exacerbated by climate change, result in a growing need for affordable and effective wastewater solutions.

In summary, organic waste is a significant contributor to water pollution, and climate change amplifies its impact. The depletion of oxygen levels in water bodies, eutrophication, and the increasing volumes of wastewater discharge due to climate change and human activities all work together to degrade aquatic ecosystems and endanger public health. Addressing these issues requires a multifaceted approach that considers wastewater treatment, agricultural practices, and the mitigation of climate change.

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