Sewage Pollution: Rivers, Boat Docks, And Raw Waste

Raw sewage is a pressing issue that affects rivers and other bodies of water. Sewage overflows from riverside boat docks can contaminate waterways with harmful bacteria, viruses, and parasites, posing risks to both environmental and human health. The decomposition of raw sewage in water also reduces oxygen levels, impacting aquatic life and contributing to harmful algal blooms. The management of sewage in boat docks is crucial to mitigating these negative effects, and proper sewage management options, such as toilets, holding tanks, and onboard treatment devices, are available to address this issue.

Sewage dumping in Cambridgeshire rivers

The Problem

Cambridgeshire's sewerage networks overflow in multiple locations across the region, particularly during periods of heavy rainfall. At these overflow sites, rainwater mixed with sewage is discharged directly into the rivers to prevent flooding. While this practice is intended to mitigate the risk of flooding, it poses a significant risk to public health. The sewage contains harmful bacteria and viruses, including E. coli, making it dangerous for individuals to enter the water, especially after heavy rainfall.

Impact and Concerns

The impact of sewage dumping on the environment and human health cannot be overstated. The sewage contributes to harmful algal blooms, reduces dissolved oxygen levels, and contaminates waterways and shellfish beds. The presence of pathogens in the water can cause various symptoms, including nausea, stomach issues, respiratory problems, and skin infections. In some cases, it can also lead to more severe waterborne diseases.

Action and Solutions

The government has acknowledged the severity of the issue and pledged to take action. In a policy shift, the Department of Environment, Food and Rural Affairs (Defra) announced plans to legally compel water companies to reduce the adverse impact of discharges from storm overflows. This announcement came after MPs faced backlash for voting against adding an amendment to the Environment Bill that would have forced water companies to halt the practice of sewage dumping.

Local councils in Cambridgeshire have also taken steps to address the problem. The South Cambridgeshire District Council, for instance, has begun working towards a formal application to the Department for Environment, Food & Rural Affairs to designate an inland bathing water stretch within their district. This designation would impose legal obligations on Anglian Water to improve water quality and reduce sewage pollution.

Precautions

While efforts are being made to address the issue, it is essential to prioritize public safety. The Rivers Trust advises individuals to avoid swimming downstream from a pump or overflow, especially after heavy rainfall, to minimize the risk of exposure to contaminated water.

Environmental and health problems

Raw sewage pumped into riverside boat docks poses significant environmental and health challenges. The environmental impact of untreated sewage from boats is comparable to, or even worse than, that of other sources of boat pollution. A single toilet flush of untreated sewage from a boat can have the same environmental impact as 10,000 flushes from a home toilet, where waste is processed by a sewage treatment facility.

One of the primary environmental concerns is the presence of excess nutrients in raw sewage, which contribute to harmful algal blooms. These blooms block sunlight penetration, reduce oxygen levels, and make it difficult for fish and other aquatic life to survive. Raw sewage also contaminates waterways with harmful pathogens, including bacteria, viruses, and parasites, which can cause various illnesses, from nausea and respiratory problems to more serious waterborne diseases.

The high concentration of waste in raw sewage increases the Biological Oxygen Demand (BOD), which is the amount of dissolved oxygen required to decompose organic matter in the water. High BODs, often found in marinas and poorly flushed areas, further contribute to the depletion of oxygen levels, creating an inhospitable environment for aquatic life.

In addition to the environmental impact, raw sewage also poses risks to human health. Water contaminated with sewage can contain a range of viruses and harmful bacteria, including E. coli. Encountering polluted water or consuming shellfish from contaminated beds can lead to serious health issues.

To address these environmental and health problems, proper sewage management is crucial. Boat owners are legally required to have Marine Sanitation Devices (MSDs) installed and must follow regulations regarding the disposal of untreated sewage. It is illegal to discharge untreated sewage into coastal and inland waters within three miles of the shore. To comply with regulations, boat owners must use on-board treatment devices or holding tanks to store and dispose of waste properly.

Sewage overflow sites

The sewage in these overflow sites contains harmful bacteria, viruses, and parasites, including E. coli, which can cause various illnesses such as nausea, stomach issues, respiratory problems, and skin infections. In addition, the sewage contains excess nutrients that contribute to harmful algal blooms, which further reduce oxygen levels in the water, making it difficult for aquatic life to survive.

In Cambridgeshire, UK, for example, raw sewage was pumped into rivers almost 2,000 times in a year, according to data from an environmental charity. The Rivers Trust has raised concerns about the potential health risks associated with these overflow sites, especially after heavy rainfall when the risk of encountering harmful bacteria and viruses is higher.

To address this issue, governments are taking action to reduce the adverse impacts of sewage discharges. For instance, the UK government has pledged to legally compel water companies to reduce the negative consequences of discharges from storm overflows. Similarly, in California, discharging raw sewage into lakes, rivers, or coastal waters within three miles of the shore is prohibited, and fines of up to $2,000 can be imposed for illegal discharges.

To manage sewage effectively, boat owners should follow proper on-board sewage management practices. This includes installing an onboard toilet with a Marine Sanitation Device (MSD) that meets the requirements set by authorities. There are three types of MSDs: Type I, which uses physical and chemical treatments; Type II, which is a biological or aerobic digestion-based system; and Type III, which is a holding tank that prevents the discharge of any sewage. Boat owners should also use onshore restrooms whenever possible and properly maintain their MSDs and plumbing to reduce odours.

No Discharge Zones

Within an NDZ, vessel operators must retain their sewage discharges on board and can only dispose of their sewage at sea beyond three miles from the shore or onshore at a pump-out facility. There are currently 91 NDZs across 27 states in the US, and these zones are clearly marked on NOAA charts and the EPA's website.

NDZs are designated when a state determines that a water body needs greater environmental protection than current federal standards allow, and the EPA finds that there are adequate pump-out facilities available. The EPA may also establish an NDZ for drinking water intake zones to safeguard human health.

To comply with NDZ requirements, vessel operators with Type I or II marine sanitation devices (MSDs) must secure their devices to prevent any discharge. This can be done by closing and padlocking the Y valve, using a non-releasable wire-tie, or removing the Y valve handle. Alternatively, they can lock the door to the toilet with a padlock or a door handle key lock. For Type III MSDs, valves leading to overboard discharge must be closed and padlocked or held closed using a non-releasable wire-tie.

NDZs are an important tool to protect aquatic habitats, safeguard human health, and ensure that sewage is disposed of safely and responsibly.

Sewage management options

Sewage management is a critical aspect of modern society, aiming to reduce the number of pollutants in wastewater before it is discharged into water bodies or reused. This process involves collecting, treating, and disposing of wastewater from households, industries, and commercial establishments. Here are some options for sewage management:

Decentralized Systems

These are smaller-scale, on-site treatment systems that treat sewage close to where it is generated. Examples include septic tanks, waste stabilization ponds, and constructed wetlands. Decentralized systems are often used in rural areas or small to medium-sized communities, as they require large areas of land but have low energy requirements and operational costs.

Centralized Systems

Centralized systems collect and transport sewage through a network of pipes and pump stations to a municipal treatment plant. This option is more common in urban areas and includes large centralized systems with sewerage infrastructure. While centralized systems can serve a larger population, they are more complex and costly to operate and maintain.

Biological Treatment Processes

Biological treatment processes use bacteria and microbes to treat sewage. This includes both aerobic and anaerobic processes. Aerobic processes, such as activated sludge systems, use oxygen to break down organic matter, while anaerobic processes, like anaerobic digesters, operate without oxygen. Biological treatment is effective in removing organic matter, nutrients, and pathogenic organisms from sewage.

Chemical Treatment Processes

Chemical treatment processes involve the use of chemicals to treat wastewater. Chlorination, for example, is a common method that uses chlorine to disinfect and treat sewage. While chemical treatment can be effective, it may also produce harmful by-products and require proper handling of chemicals to avoid environmental and health risks.

Physical Treatment Processes

Physical treatment processes employ mechanical means to remove solid wastes from sewage. This includes sedimentation, where heavy particles settle, and filtration, where contaminants are filtered out. Physical treatment is often used in conjunction with other methods and helps reduce the volume of solid waste.

Advanced Treatment Options

Advanced treatment options involve additional stages, such as tertiary treatment, to further improve the quality of the treated sewage. This may include nutrient removal, disinfection, and the removal of micropollutants like pharmaceuticals. Advanced treatment is more costly and energy-intensive but can be necessary to protect sensitive ecosystems and ensure safe reuse of wastewater.

Frequently asked questions