Sewage's Sinister Impact: Polluting Our Precious Waterways

Sewage pollution is a pressing issue that has gained significant attention in recent years. It refers to the contamination of water sources, such as rivers, streams, and oceans, by untreated or partially treated sewage. This pollution has severe consequences for both human health and the environment. In this discussion, we will delve into the various ways in which sewage pollutes water, the factors contributing to this problem, and the potential solutions and initiatives aimed at mitigating the impact of sewage pollution on our precious water resources.

Sewage overflows

Sanitary Sewer Overflows (SSOs) are a type of unauthorized discharge of untreated or partially treated wastewater from a collection system or its components (e.g. a manhole, lift station, or cleanout) before reaching a treatment facility. SSOs can contaminate our waters, causing serious water quality problems, and back up into homes, causing property damage and threatening public health. The EPA estimates there are at least 23,000-75,000 SSOs per year in the US, not including sewage backups into buildings.

SSOs are prohibited unless authorized by an NPDES permit. Permitted facilities and subscribers must report all SSOs, regardless of volume, as federal and state regulations do not specify a minimum reporting volume. They must report the date, location, volume, and contents of the SSO to their regional office within 24 hours. Each SSO incident is unique, and cleanup requirements should be based on individual circumstances. A typical cleanup plan includes stopping or mitigating the flow, containing the spill, returning spilled wastewater to the collection system or treatment facility, removing and disposing of solids, and treating and disinfecting the affected area.

SSOs can have severe negative consequences for the environment and society. When they enter oceans, bays, estuaries, rivers, lakes, streams, or brackish waters, they can render these bodies of water unusable for drinking water, shellfish harvesting, fishing, or recreation, causing economic losses. SSOs can also lead to beach closures, decreased tourism, and reduced waterfront property values.

SSOs are often caused by inadequate or improper operation or maintenance, insufficient system capacity, and improper system design and construction. To reduce or eliminate SSOs, communities should consider enlarging or upgrading sewer systems, pump stations, or sewage treatment plants, constructing wet weather storage facilities, and educating the public on how certain substances can clog sewers.

Sewage treatment

There are a variety of sewage treatment processes available, ranging from decentralized systems (including on-site treatment systems) to large centralized systems involving a network of pipes and pump stations that convey sewage to a treatment plant. In most cases, sewage treatment involves two main stages: primary and secondary treatment. Secondary treatment can further be classified into aerobic and anaerobic biological processes, which reduce organic matter from sewage.

One example of a secondary treatment process is the activated sludge process, which achieves high-quality effluent but is relatively expensive and energy-intensive. This process involves biological degradation, where microorganisms consume pollutants and transform them into cell tissue, water, and nitrogen. The treated wastewater then separates from the biology in large circular tanks called secondary clarifiers, resulting in an effluent that is over 90% treated.

Following secondary treatment, the clarified effluent undergoes filtration, disinfection, and oxygen uptake. Disinfection, often through ultraviolet treatment, ensures that the treated wastewater is free of bacteria. The treated water is then aerated if necessary to bring the dissolved oxygen levels up to the required standard.

In addition to secondary treatment, advanced treatment methods can be employed, including tertiary and even quaternary treatment steps. Tertiary treatment involves polishing processes and nutrient removal, while quaternary treatment addresses the removal of organic micropollutants, such as pharmaceuticals. These advanced treatment methods enhance the quality of the treated effluent and further protect the environment from pollution.

Water quality testing

Testing Methods:

• Biochemical Oxygen Demand (BOD) Test: This test counts the number of decomposer bacteria in the water as it leaves sewage treatment plants. A high number of bacteria indicates a higher amount of sewage and its potential impact on oxygen levels in waterways. However, the current version of this test only counts carbon-eating bacteria, and a switch to a complete BOD test, which includes nitrogen-eating bacteria, could provide a more accurate assessment.
• Fecal Coliform and Ammonia Testing: These tests can predict the probability of sewage-sourced pollution. Escherichia coli (E. coli) is a common indicator species, but it can also be present in the environment from other sources, leading to false positives. Testing for bacteria of the Enterococcus genus is considered a gold standard as they are found in the feces of all mammals but rarely elsewhere. Additionally, high ammonia levels can indicate sewage pollution, but this can also be due to agricultural runoff and animal feeding operations.
• Satellite Imaging: Satellite images can detect plumes of material where runoff meets water. Brown plumes indicate the presence of sediment, which is likely to include sewage. This method is useful after major polluting events like toxic spills or natural disasters.

Testing Protocols:

• Sampling and Classification: In the UK, water quality testing is conducted during the bathing season, which varies across England and Wales, Scotland, and Northern Ireland. Samples are taken once a week by environmental regulators such as the Environment Agency (EA), and they are sent to specialist labs for testing within 24 hours. The results classify bathing waters as "excellent," "good," "satisfactory," or "poor."
• Challenges and Criticisms: The current water quality testing regimes in the UK have been criticized for ignoring significant pollution events and misleading the public about water safety. There are concerns about the high number of false positives and the permission granted to regulators to discount samples during short-term pollution events. This has led to a call for real-time water quality monitoring and the removal of loopholes in the testing regime.

Community Initiatives:

• The Rivers Trust: The Rivers Trust has formed the Catchment Monitoring Cooperative to support local communities in monitoring the water quality of their rivers. They provide standardized methodologies, resources, and guidance to ensure robust and accurate testing.
• Riverfly Partnership: Led by Dr. Cyril Bennett, this partnership trains volunteers to monitor biodiversity at various sites by taking standardized samples and scoring different groups of insects. If the scores fall below a certain level, indicating an issue, the Environment Agency is contacted to investigate.

In conclusion, water quality testing is a complex and challenging task, and it is crucial to employ a range of testing methods and protocols to accurately identify sewage pollution and protect water bodies and the health of humans, animals, and the environment.

Sewage in the natural environment

Sewage can enter natural waterways through various means. In some cases, water companies are permitted to discharge sewage into rivers in emergencies, such as during heavy rain, to prevent sewers from backing up into buildings. However, this has been grossly abused, with water companies in the UK self-reporting over 400,000 instances of sewage release into waterways in 2020, totalling over 3.1 million hours of wastewater overflow. Southern Water, for instance, was fined £90 million for thousands of illegal discharges between 2010 and 2015. Antiquated sewer systems, poor waste management, and misconnections further exacerbate the problem, leading to sewage overflows and leaks that contaminate natural water sources.

The impact of sewage pollution on the natural environment is devastating. It destroys delicate ecosystems, kills wildlife, and threatens ocean recovery. Sewage can cause harmful algal blooms, which starve the water of oxygen, leading to the death of aquatic species. It introduces contaminants that can result in the spread of diseases such as E. coli, diarrhea, and hepatitis A, posing risks to both human and animal health. Even properly treated sewage has its drawbacks, as microscopic plastic fibres can pass through wastewater treatment plants and harm marine life and the food chain.

The continuous discharge of treated sewage is the largest source of water pollution from water companies. Phosphorus, a nutrient present in waste discharge from sewage works, contributes to the eutrophication of freshwaters. This occurs when nutrient levels are too high, damaging water quality and local ecology. While natural recovery of ecosystems is possible if they are not overwhelmed, chronic pollution can cause irreversible harm.

To address sewage pollution in the natural environment, governments and water companies must work together to implement effective solutions. This includes reducing storm overflows, improving wastewater treatment infrastructure, and enforcing regulations to hold polluters accountable. Public awareness and participation are also crucial, as everyone can play a part in improving water quality by properly disposing of waste and supporting campaigns like #EndSewagePollution.

Health risks of sewage pollution

Sewage pollution has a detrimental impact on water quality and poses significant health risks to humans. The discharge of untreated or partially treated sewage into rivers, streams, and oceans has raised public concern in England, with only 14% of rivers meeting good ecological standards. This pollution not only affects ecosystems but also endangers human health.

One of the primary health risks associated with sewage pollution is the spread of waterborne diseases. Contaminated water can harbor various pathogens, including bacteria, viruses, and parasites, which can cause severe illnesses in humans. Campylobacteriosis, caused by the bacterium Campylobacter, is the most common diarrheal illness in the United States, with symptoms including bloody diarrhea, abdominal pain, nausea, and fever. Cryptosporidiosis (Crypto), caused by the parasite Cryptosporidium, is another prevalent waterborne disease, resulting in diarrhea, stomach cramps, and fever.

Viral gastroenteritis, often referred to as "stomach flu," is another illness linked to sewage-contaminated water. It is caused by a range of viruses, including rotaviruses, adenoviruses, and caliciviruses, leading to watery diarrhea, vomiting, headache, and fever. Giardiasis, caused by the parasite Giardia intestinalis, is also common, resulting in diarrhea, stomach cramps, and an upset stomach. Hepatitis A, a liver disease, is another concern, with symptoms such as jaundice, fatigue, and abdominal pain.

In addition to these specific diseases, sewage pollution can lead to the presence of harmful viruses, antimicrobial-resistant bacteria, and other pathogens in the water. This can further elevate health risks for individuals who come into contact with or consume contaminated water.

The impact of sewage pollution extends beyond the immediate health risks to humans. It also has a detrimental effect on natural ecosystems, threatening ocean recovery and reducing biodiversity. Sewage can cause harmful algal blooms, which starve the water of oxygen, leading to the death of aquatic species. The presence of phosphorus in treated sewage contributes to eutrophication, further damaging the local ecology.

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