Boat Sewage Discharge: Understanding The Environmental Impact

Sewage management is a necessary part of a boat's systems. It is illegal to discharge untreated sewage into inland or coastal waters. Marinas and docks operating on public waters must provide a sewage removal service. When tied to a dock, onshore facilities must be used. There are several options for on-board sewage management, including toilets, holding tanks, and on-board treatment devices. Toilets on boats must be attached to a Marine Sanitation Device (MSD) to treat the waste before it is discharged.

Untreated sewage discharge is illegal in inland and coastal waters

The bacteria in untreated sewage can cause a range of symptoms, from nausea and upset stomachs to respiratory problems and skin infections. It can also lead to more serious waterborne diseases if people encounter polluted water or consume contaminated shellfish. In addition, the excess nutrients in sewage can contribute to harmful algal blooms, which block sunlight penetration and deplete oxygen levels in the water, making it difficult for aquatic life to survive.

To comply with the law and protect the environment, boat owners have several options for on-board sewage management. These include installing a toilet with a marine sanitation device (MSD), using a holding tank (also known as a Type III MSD), or investing in an on-board treatment device (Type I or Type II MSD). These options can help treat sewage and reduce bacteria and nutrient levels before discharge.

It is important to note that even with these systems in place, there are still restrictions on where sewage can be discharged. No Discharge Zones (NDZs) are areas where the discharge of treated or untreated sewage from boats is prohibited. Boat operators must retain their sewage discharges on board and dispose of them at a pump-out facility on shore or beyond a certain distance from the shore.

By following these regulations and properly managing sewage, boaters can play a crucial role in protecting the environment and human health.

No Discharge Zones (NDZ) prohibit all treated and untreated sewage discharge

No Discharge Zones (NDZs) are areas where the discharge of treated and untreated sewage from vessels is prohibited. These zones are established under the Clean Water Act (CWA) to protect water quality and the environment. NDZs require vessel operators to retain their sewage discharges on board for disposal at sea beyond three miles from shore or at onshore pump-out facilities.

The main concern with sewage in waterways is the presence of bacteria and excess nutrients, which can have negative impacts on the environment and human health. Bacteria can make boating and swimming unsafe and can lead to closures of waterways and shellfish beds. Excess nutrients can contribute to harmful algal blooms, which reduce oxygen levels in the water and harm aquatic life.

To comply with NDZ requirements, vessel operators must ensure that their sewage discharges are securely retained on board. This can be achieved through different methods, depending on the type of marine sanitation device (MSD) installed. For Type I and II MSDs, this can be done by closing and locking the seacock, using a non-releasable wire-tie, or locking the door to the toilet enclosure. For Type III MSDs, which are holding tanks, valves leading to overboard discharge must be closed and secured with locks or wire-ties.

NDZs are designated by states in collaboration with the U.S. Environmental Protection Agency (EPA). There are three main circumstances under which a state may initiate the process to establish an NDZ: protecting aquatic habitats, protecting special aquatic habitats or species, and safeguarding human health by protecting drinking water intake zones. As of January 2025, several states have designated some or all of their surface waters as NDZs, including California, New York, Washington, and others.

It is important for boaters to be aware of the locations of NDZs and to comply with the requirements to protect the environment and human health. Boaters should also consider other options for on-board sewage management, such as installing toilets with marine sanitation devices, using holding tanks, or utilising on-board treatment devices.

Marine Sanitation Devices (MSDs) are required for boats with installed toilets

Marine Sanitation Devices (MSDs) are required by law for boats with installed toilets. The Clean Water Act (CWA) of 1972 (amended in 1987) mandates that boats with installed toilets must be equipped with an operable MSD certified by the Coast Guard. This regulation aims to control sewage discharges from vessels by regulating the equipment used to treat or hold the sewage.

There are three types of MSDs: Type I, Type II, and Type III, each with specific design, certification, and discharge criteria. Type I and Type II MSDs are commonly found on large vessels and use special chemicals to treat waste before discharge. These systems employ physical, chemical, or biological treatment methods, such as maceration, chlorination, or aerobic digestion, to reduce bacteria and suspended solids in the sewage effluent. Type III MSDs, on the other hand, are holding tanks or portable toilets that do not provide treatment. The collected waste in Type III systems must be taken ashore and disposed of at pump-out stations or onshore toilets.

The choice of MSD depends on the size of the boat and the type of boating activities. Vessels 65 feet or less in length can use any of the three types, while larger vessels over 65 feet must install a Type II or Type III MSD. It is important to note that MSD regulations do not apply to vessels without installed toilets, such as those with portable toilets or "porta-potties."

To comply with environmental and health standards, boat owners should be aware of No Discharge Zones (NDZs). NDZs are areas where the discharge of treated or untreated sewage from boats is strictly prohibited. In these zones, vessels must retain their sewage discharges on board and dispose of them properly onshore or beyond three miles from the shore. It is the responsibility of boat operators to know the locations of NDZs, which are clearly marked on NOAA charts and listed by the EPA.

By following these regulations and properly maintaining their MSDs, boat owners can play a crucial role in protecting aquatic habitats, safeguarding human health, and ensuring a pleasant boating experience for everyone.

MSDs come in three types, treating waste with chemicals or storing it

Marine Sanitation Devices (MSDs) are a crucial part of a boat's systems. They are defined as "any equipment for installation on board a vessel which is designed to receive, retain, treat, or discharge sewage, and any process to treat such sewage."

The U.S. Coast Guard categorizes MSDs into three types, each with its own design, certification, and discharge criteria:

Type I MSD

Type I MSDs are on-board treatment devices that use a physical/chemical-based system. They rely on maceration and chlorination to treat sewage. The sewage is pulverized and macerated, and then disinfected with specialized chlorine tablets to neutralize it and reduce harmful bacteria to safe levels. In some cases, electrodes may be used to enhance the disinfection process. Once the sewage is treated, it can be safely discharged from the vessel, as long as it is done in an area where it is an accepted practice. Type I MSDs are typically found on smaller recreational boats that are 65 feet or less in length.

Type II MSD

Type II MSDs are also on-board treatment devices, but they use a biological or aerobic digestion-based system. This system breaks down the waste using oxygen-dependent bacteria and then treats it with a disinfectant. Type II MSDs are more commonly found on larger commercial vessels than recreational boats. They are more effective at treating waste than Type I MSDs, making it easier to meet Coast Guard standards for safe discharge and reducing the risk of fines.

Type III MSD

Type III MSDs are the simplest of the three types. They consist of a holding tank that prevents the overboard discharge of treated or untreated sewage. These MSDs do not treat the waste but simply store it until it can be discharged shore-side or at sea beyond three miles from the shore. Type III MSDs are typically found on smaller recreational boats as they are less complex and less effective at treating waste.

It is important to note that discharging untreated sewage into inland or coastal waters is illegal. Boat operators must either have an on-board treatment device (Type I or Type II MSD) or a holding tank (Type III MSD) to store the waste and have it pumped out ashore. In addition, No Discharge Zones (NDZs) prohibit the discharge of treated boat sewage, requiring vessel operators to retain their sewage discharges on board for proper disposal.

Pump-out systems are an effective way to dispose of sewage

There are three types of MSDs. Type I and Type II MSDs are usually found on large vessels and use special chemicals to treat waste and kill bacteria before it is discharged. Type III MSDs, on the other hand, provide no treatment and are either holding tanks or portable toilets. For Type III MSDs, the collected waste should be taken ashore and disposed of at a pump-out station or onshore toilet.

Pump-out stations are marked by a universal symbol that directs boaters to the correct location. It is important to carefully follow the instructions for using a pump-out station, as mistakes can lead to a messy situation. The general process involves removing the cap from the boat's deck waste fitting, inserting the pump-out hose nozzle, and turning on the pump. Once the waste has been pumped out, the hose is rinsed with water, and the pump is turned off.

Pump-out systems are an effective way to ensure that sewage is disposed of properly and does not end up in waterways, where it can cause significant environmental and human health problems. Untreated sewage contains excess nutrients that contribute to harmful algal blooms, deplete oxygen levels, and contaminate shellfish beds with pathogens. By using pump-out systems, boaters can play a crucial role in protecting the environment and maintaining safe recreational waterways.

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