Understanding Biological Water Pollution: An Ecological Concern

Biological water pollution refers to the presence of microbes and pathogens in water sources, including viruses, bacteria, algae, protozoa, nematodes, and parasites. These contaminants can cause various waterborne diseases and illnesses, such as typhoid, cholera, and diarrheal illnesses, leading to a significant number of deaths, especially among children. One example of a biological water pollutant is Giardia, a parasite that can cause the waterborne disease Giardiasis, which can be treated with specific antibiotics. Other examples include Salmonella, Shigella, Vibrio cholerae, and E. coli, which can indicate the presence of harmful, disease-causing organisms. These biological contaminants can enter water supplies through various means, such as rainwater runoff, sewage discharge, or open defecation, posing risks to human health and the environment.

Bacteria, viruses, and parasites

Bacteria are present in the environment, including surface waters and groundwater. While some bacteria are harmless, others can be harmful to human health. For example, E. coli bacteria indicate the presence of faecal matter in water, which can contain many pathogens. Testing drinking water for coliform bacteria is a simple way to determine if there may be harmful pathogens in the water.

Viruses can also contaminate water resources, and their survival, transport, and sorption in porous media are influenced by various factors such as solution chemistry, virus properties, soil properties, temperature, and association with solid particles.

Parasites are another type of biological contaminant. Schistosomiasis, for example, is a parasitic disease that affects people living in close proximity to large reservoirs and irrigation schemes. In 2021, over 251.4 million people required preventative treatment for schistosomiasis, which is caused by parasitic worms contracted through exposure to infested water.

To ensure clean water, disinfection methods are employed to remove biological pollutants such as bacteria, viruses, and parasites. However, it is not practical to remove all microorganisms completely. Therefore, organisations like the WHO and EPA have set minimum allowed microbial limits for safe drinking water.

Waterborne pathogens

Waterborne diseases have been a problem for centuries, with historical examples including cholera and typhoid, which caused serious gastrointestinal illnesses and sometimes resulted in death. However, with the implementation of effective drinking water treatment, disinfection, and sanitation measures, these diseases have become rare in many parts of the world. Today, waterborne diseases are still responsible for a variety of illnesses, including respiratory illnesses, neurological illnesses, skin problems, gastrointestinal illnesses, and bloodstream infections.

The detection and characterization of waterborne pathogens are crucial for maintaining water safety. Advances in detection methods, such as molecular techniques, have improved the ability to identify waterborne pathogens and track their sources. Additionally, water management programs and infrastructure updates play a vital role in limiting the growth and spread of waterborne pathogens. These programs are now standard for large buildings and are required for healthcare facilities.

To prevent waterborne diseases, it is essential to educate the public on protecting themselves and implementing prevention campaigns and messages. Additionally, collaboration between policymakers, industry partners, building managers, public health professionals, and other stakeholders is necessary to address the complex nature of waterborne pathogen contamination.

Salmonella, Shigella, Vibrio cholerae

Biological water pollution refers to the contamination of water by microbes or microbiological contaminants. These include bacteria, viruses, protozoa, and parasites. Salmonella, Shigella, and Vibrio cholerae are examples of bacteria that can cause biological water pollution and subsequent diseases in humans.

Salmonella is a common cause of foodborne disease outbreaks, with contaminated produce being a significant vector. It is frequently found in surface water, which is often used for irrigation. Irrigation water has been identified as a source of Salmonella transmission to produce, with the pathogen surviving in aquatic environments by entering a viable but non-culturable state or residing within free-living protozoa. The presence of Salmonella in water and food has significant implications for public health and food safety.

Shigella is a group of bacteria that cause shigellosis, an acute intestinal illness. It is commonly found in soil, food, water, and surfaces contaminated with the feces of infected individuals. Shigella is more prevalent in surface waters, such as rivers and lakes, than in groundwater sources due to its susceptibility to chlorine treatment in water treatment plants. Effective sewage treatment and water supply protection are crucial for reducing the incidence of shigellosis.

Vibrio cholerae is the bacterium responsible for cholera, an acute diarrheal illness. Cholera was once prevalent but has become rare in developed countries due to advancements in sewage treatment and drinking water sanitation. However, it remains a significant health concern in developing countries with inadequate sanitation and water treatment infrastructure. V. cholerae accumulates in the stomach, producing toxins that affect the gastrointestinal tract, leading to severe fluid loss and potentially fatal dehydration.

To prevent biological water pollution and the associated health risks, it is essential to ensure proper sewage disposal, treat drinking water effectively, and maintain good hygiene practices, especially when handling food and water. These measures can help reduce the presence and transmission of harmful bacteria like Salmonella, Shigella, and Vibrio cholerae, protecting public health and improving water quality.

Microbes and pathogens

Sources of microbial water pollution include stormwater runoff, agricultural runoff, industrial wastewater, and domestic wastewater. For example, livestock can contribute to microbial water pollution, as can human and animal faecal waste.

The presence of pathogenic bacteria in water is usually sporadic and erratic, and the levels are typically low. However, safe water demands that water is free from pathogenic bacteria. The discovery and testing of indicator bacteria have helped address this issue. Indicator bacteria are used to predict the presence of pathogens in water. They are chosen because they are not pathogenic to humans, can be easily and cheaply detected in environmental waters, and have similar die-off behaviour to pathogens.

The removal of biological pollutants such as bacteria, protozoa, and viruses is known as disinfection. While it is not possible to completely remove these microorganisms from water, standard guidelines have been put in place by organisations such as the WHO and the EPA to ensure clean water. These guidelines specify the minimum allowed microbial limit of pollutants in water.

Sewage and wastewater

Wastewater is broadly classified into four types: stormwater runoff, agricultural runoff, industrial wastewater, and domestic wastewater. All of these sources can contain biological contaminants that pose risks to human health and the environment. For example, stormwater runoff can carry pollutants from agricultural fields, ponds, and forests, while domestic wastewater can contain high levels of nutrients, pathogens, pharmaceuticals, and heavy metals.

Sewage pollution, in particular, has been identified as a global issue, with contamination hotspots occurring in terrestrial, aquatic, and marine systems. The impact of sewage pollution on natural habitats, such as coral reefs, salt marshes, and fish-rich river systems, is a growing concern for conservation biologists and managers. Untreated or poorly treated sewage can lead to elevated concentrations of nutrients, pathogens, endocrine disruptors, heavy metals, and pharmaceuticals, which threaten biodiversity and ecosystem health.

The treatment of sewage and wastewater is essential to mitigate the negative effects of biological pollution. Traditional sewage treatment methods, such as activated sludge treatment, often require high energy consumption and can produce large amounts of poor-quality sludge. However, innovative solutions are being explored, such as the use of microalgae and bacteria to treat wastewater more sustainably and cost-effectively. These microorganisms can enhance the treatment process by reducing nutrient concentrations, removing organic pollutants, and improving photosynthetic activity, resulting in cleaner water.

Overall, sewage and wastewater pollution pose significant risks to both human health and the environment. Adequate treatment of these waste streams is crucial to prevent the spread of waterborne diseases and protect aquatic ecosystems, biodiversity, and public health. By improving wastewater treatment technologies and raising awareness about the impacts of biological pollution, we can work towards mitigating this global issue.

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