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Published on 28/04/2022

Sewage Water Testing Methods

Sewage effluent is an issue for all manned vessels – especially those spending considerable time at sea. Large or small, your ship is likely to have a sewage testing requirement and must comply with IMO legislation when processing raw waste.   

The benefits of proper sewage management and testing (and the risks associated with failing to do so) are extensive – even today, a significant number of incidents per year occur relating to mismanaged waste on board (in 2019, the most common reason for vessel detention in Singapore was sewage-related, according to the UK P&I Club). Due to the nomadic nature of the shipping industry, it also has a role to play in the spreading and development of diseases – most recently, a WHO report identified over 100 disease outbreaks associated with ships between 1970 and 2000. 


In the past, ships freely and routinely released raw sewage into the water – until the negative impact on aquatic life and human wellbeing was identified in the 1970s and 80s. Sewage effluent can pose several risks to crew health and the environment if improperly managed or untreated. 

Key risks associated with sewage at sea include:

Risk to human health: Untreated or raw sewage poses a significant threat to human health. Health hazards include gastroenteritis, ear infections, nose and throat and viruses such as hepatitis A and E and e-coli. Some of these become even more hazardous in confined spaces, such as those commonly found onboard sea-going vessels, where bacteria can build and sickness can spread quickly. Close to shore pollution can close beaches and make swimming hazardous due to the dangerous organisms released.

Environmental damage: Many people mistakenly believe that sewage is ‘natural waste’ – therefore, it’s not a problem if it is returned to nature. Yet, the volume of sewage released at any given time by vessels, can cause extreme and long-lasting damage to the marine environment, including oxygen depletion, higher levels of toxins, parasites, and bacteria that poison marine life.

Visual pollution: As many of our oceans are so vast, there’s a misconception that sewage release will go unnoticed – but it doesn’t always assimilate as you may expect – incredibly close to shore. In coastal areas, the discharge of raw sewage can cause unsightly slicks on the water’s surface. There is also the risk of articles washing up on beaches and the fall-out of related environmental pollution, such as dead fish and marine animals. 

There is also a broader ecological impact attached to improper management and disposal of sewage, as changes to local eco-systems have a far-reaching effect.  

The health and protection of our oceans are now in sharper focus, following several environmental initiatives over the years designed to raise awareness. Reducing the levels of sewage released into the world’s oceans and mitigating its impact was the first-ever ecological initiative – led by the IMO, efforts to produce and enforce legislation started in the late 1970s and eventually came into force in 2003.  

As a result of their efforts, extensive sewage testing legislation was introduced – the most recent of which, MARPOL Annex IV, (resolution MEPC.115(51)), published on 27th September 2008. It applies to ships on international voyages, which are either 400gt and greater or less than 400gt when certified to carry more than 15 persons, including passengers and crew. 


Regular testing offers reliable protection against effluent discharge running outside of MARPOL regulated consent levels, ensuring your sewage treatment systems onboard are running smoothly and efficiently. Coupled with water testing, you can protect your crew against cross-contamination and the risk of pathogens or chemicals entering your potable water supply. 

Testing at specific intervals also ensures that timely corrective action can be taken to restore balance to disinfection protocols, remove the risk of organic or chemical contamination and ensure that sewage treatment falls in line with current legislation. Testing sewage effluent also has several critical advantages for ship management, including reducing costs and a lower risk of operational downtime due to impaired crew health. 

Non-compliance can also be costly in terms of fines and penalties and the prospect of crew sickness and downtime should an investigation occur. 

Portable water testing solutions 

Alongside the above directives, the most widely-used (and recommended) line of defence against sewage effluent pollution and mismanagement is potable water testing. 

The testing method uses specialist kits which monitor and measure several vital markers, including Biological Oxygen Demand (BOC), Chemical Oxygen Demand (COD) and Total Organic Carbon (TOC) alongside pH levels, bacteria and coliforms. 

These kits can be used on a regular testing schedule to ensure that sewage is being correctly processed and that drinking water remains safe. 

How sewage testing solutions from Martek Marine can help

Our all-in-one Sewage Effluent Test Kit goes above and beyond the capabilities of most models to deliver reliable, responsive and hassle-free support, providing combined water and sewage testing capacity. Thanks to its innovative functionality and efficient design it’s also the most cost-effective and comprehensive testing kit currently available on the market, meaning spares can be ordered to keep the equipment fully operational rather than replacing the kit itself. 

You can download our informative free guide for more on Sewage Effluent Testing