Fertilisers And Sewage: Water Pollution's Unseen Threat

Water pollution is a pressing issue that has various sources, including fertilisers and sewage. Fertilisers, which are used to enhance plant growth, can contaminate water bodies through runoff and soil erosion, leading to excessive algae growth and oxygen depletion. Sewage discharge, often a result of overwhelmed sewer systems, releases untreated or partially treated waste into rivers and oceans, posing risks to human health and aquatic ecosystems. Both fertilisers and sewage contribute to water pollution, affecting water quality and the organisms that depend on it. This dual problem demands attention and action to safeguard water resources and the health of communities and natural environments.

Excess nutrients from fertilisers and sewage cause eutrophication, leading to uncontrolled algae growth

Fertilisers used in agriculture are a significant source of nutrient pollution in water. Nitrogen and phosphorus runoff from agricultural fields are some of the largest contributors to coastal "dead zones" across the United States. For example, farms in the Midwest drain into the Mississippi River, leading to a nutrient overload in the Gulf of Mexico, which has decimated the region's shrimp industry. Similarly, Norway and Finland have reported significant eutrophication of surface waters arising from agriculture, with high levels of nitrogen and phosphorus usage leading to increased algae proliferation in the Adriatic Sea.

The impact of algae blooms can be toxic to lakes and oceans, as they can create conditions that are harmful to both wildlife and humans. For instance, blue-green algae (cyanobacteria) can cause rashes, nausea, and respiratory problems in humans, and it has been known to kill livestock that drink from affected water sources. In addition, the depletion of oxygen in the water due to algae growth can lead to fish kills and a decrease in aquatic life.

The excess nutrients that cause eutrophication can come from a variety of sources, including runoff from urban areas, wastewater treatment facilities, and farming practices. For example, lawn and garden fertilisers can contribute to nutrient runoff, as rainfall or irrigation can carry excess phosphorus and agro-chemicals into ditches, streams, and eventually larger water bodies. Properly managing and reducing nutrient losses from farm fields and urban areas is essential to mitigating the impact of eutrophication and uncontrolled algae growth.

Algal blooms deplete oxygen in water, creating hypoxic dead zones where no aquatic life can survive

Algal blooms, also known as eutrophication, are a major cause of oxygen depletion in water bodies. This occurs when excess nutrients, particularly nitrogen and phosphorus, from sources like fertiliser runoff and sewage, stimulate rapid algae growth. While algae do produce oxygen during the day through photosynthesis, they consume more oxygen than they produce at night. As algal blooms grow denser, they block sunlight and limit photosynthesis, reducing the amount of oxygen produced.

Additionally, when trace minerals or nutrients needed by the algae are depleted, some or all of the bloom may die back temporarily. The resulting bacterial decomposition further reduces oxygen levels in the water. As the algae and bacteria decompose, they are consumed by microorganisms, which reproduce and use up the remaining oxygen in the water, creating hypoxic conditions.

The depletion of oxygen in water due to algal blooms can have severe ecological consequences. Fish and other aquatic organisms suffocate, leading to a buildup of dead organic matter that further degrades water quality. This creates "dead zones" where aquatic life cannot survive due to the lack of oxygen. These dead zones can impact bays, lakes, and coastal waters, affecting recreational activities, businesses, and property values.

Furthermore, the potential exists for the algae to be toxic. Certain types of blue-green algae (cyanobacteria) can cause rashes, nausea, and respiratory problems in humans, and have been known to kill livestock that drink from affected water sources.

To address the issue of oxygen depletion caused by algal blooms, proper management of nutrients and pollutants associated with fertilisers and sewage is essential. Reducing nutrient runoff, improving wastewater treatment, and preventing excess nutrients from entering water bodies can help mitigate the occurrence and impact of algal blooms, thereby preserving aquatic ecosystems and the communities that depend on them.

Phosphorus in fertilisers is carried by runoff into waterways, acting as junk food for algae

Phosphorus is a major cause of water pollution. When fertilisers are applied to fields, phosphorus from the fertiliser can be washed away by rainfall and carried by runoff into nearby waterways. This process is known as eutrophication. Eutrophication is the human-accelerated process by which a body of water becomes abundant in certain nutrients, causing an increase in aquatic plants and a decrease in oxygen content.

Phosphorus is a vital ingredient in fertilisers because it is essential for plant growth. It is the central number in the NPK analysis printed on a fertiliser bag, with N standing for nitrogen, P for phosphorus, and K for potassium. However, an excess of phosphorus in waterways can upset the natural balance of the ecosystem, leading to an overabundance of algae, also known as an algae bloom.

Algae blooms are harmful because they deplete the oxygen in the water, causing fish and other aquatic species to suffocate. As the algae die, they are used as a food source by microorganisms, which further reproduce and consume the remaining oxygen in the water. This can lead to unpleasant odours and a decrease in water quality, rendering the water unfit for recreational use and reducing the value of surrounding properties.

Furthermore, blue-green algae, or cyanobacteria, can be toxic to humans and livestock, causing rashes, nausea, and respiratory problems if ingested. Therefore, it is essential to manage the application of fertilisers properly and prevent the runoff of phosphorus into waterways to maintain a healthy aquatic ecosystem.

To mitigate the issue of phosphorus runoff, scientists have developed organic fertilisers, such as Dr. Earth®, that contain only water-insoluble forms of phosphorus. By using these fertilisers, farmers can ensure that the phosphorus remains in the soil and does not leach into nearby waterways. Additionally, improving wastewater treatment processes to remove and reuse phosphorus from sewage can help reduce pollution and provide an alternative source of phosphorus for fertilisers.

Animal manure contains harmful microorganisms, including bacteria, viruses, and parasites

Animal manure is a significant source of human pathogens. It contains harmful microorganisms, including bacteria, viruses, and parasites. For instance, dangerous pathogens like E. coli O157:H7, Listeria, and Cryptosporidium are found in cattle, sheep, and deer feces. Similarly, Salmonella bacteria can be transmitted through poultry, wild birds, and even pets' droppings. When manure enters surface water, the nutrients it releases stimulate microorganism growth, which then reduces the dissolved oxygen content of the water body, causing fish and other aquatic species to suffocate.

Fresh manure from warm-blooded animals contains countless microorganisms, some of which are pathogenic and can cause diseases in humans and animals. For example, several outbreaks of gastroenteritis have been traced to livestock operations, with pathogens including protozoans (Cryptosporidium parvum, Giardia spp.), bacteria (Listeria monocytogenes, Escherichia coli O157:H7, Salmonella spp., and Mycobacterium paratuberculosis), and some enteric viruses.

The presence of these harmful microorganisms in manure can have significant implications for water quality and public health. When manure is not properly managed or applied, these pathogens can contaminate water sources, leading to waterborne diseases. For instance, in 2011, an outbreak of diarrhea and hemolytic uremic syndrome in Oregon was linked to the consumption of strawberries grown in a field contaminated with deer feces.

To reduce the risk of pathogen transmission, it is crucial to handle and apply manure correctly. This includes storing manure away from water sources and fresh produce, treating manure through composting to reduce pathogens, and implementing procedures to limit wild and domestic animal access to production fields. By taking these precautions, the risk of water pollution and disease transmission associated with animal manure can be mitigated.

Additionally, ammonia-contaminated runoff from manure application sites can have toxic effects on aquatic life. High levels of ammonia in surface water can kill fish, even at low concentrations of 0.02 parts per million (ppm). This further highlights the importance of proper manure management to prevent water pollution and protect aquatic ecosystems.

Improper application of fertilisers can increase the risk of nutrient runoff into water bodies

Improper application of fertilisers can have detrimental effects on water bodies, increasing the risk of nutrient runoff and causing water pollution. This occurs when excess fertilisers are not absorbed by plants and lawns, leading to fertiliser residues that can be washed away by rainfall or irrigation. The process, known as eutrophication, results in an abundance of nutrients, particularly nitrogen and phosphorus, in water bodies.

Nitrogen and phosphorus are essential nutrients for plant growth and are commonly found in fertilisers. However, when applied in excess or improperly managed, they can contaminate water sources. This is especially true for water-soluble phosphorus, which can easily be carried by runoff across lawns, roads, and woods, eventually reaching streams, reservoirs, lakes, and even the ocean. The excessive phosphorus acts as ""junk food"" for algae, stimulating their growth and leading to algal blooms.

Algal blooms have severe ecological consequences. As the algae grow and reproduce, they deplete the oxygen content in the water, creating ""dead zones"" where fish and other aquatic species suffocate due to a lack of oxygen. Additionally, certain types of algae, such as blue-green algae (cyanobacteria), can produce toxins that are harmful to humans and livestock. These toxins can cause rashes, nausea, and respiratory problems if people come into contact with or consume affected water.

Improper fertiliser application can also introduce pathogens and nitrates into drinking water sources. Nitrates, in particular, can leach into groundwater due to their ability to move freely through the soil. High levels of nitrates can be toxic to both humans and animals, posing significant health risks if consumed through contaminated water.

To mitigate these issues, it is crucial to apply fertilisers properly and only when needed. This includes avoiding over-fertilisation, applying fertilisers during the correct season when plants are actively growing, and ensuring that fertilisers do not come into contact with waterways, such as lakes, streams, or ponds. By following best practices and guidelines, the risk of nutrient runoff and water pollution can be significantly reduced.

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