It might not be the first thing that comes to mind when you think of cruise ships, but those huge ships generate a lot of wastewater. there’s a lot of that Grey WaterLiquid waste from things like showers, laundry facilities, dishwashers, baths, and washbasin drains.
Greywater may not seem as related as sewage (drainage from toilets and urinals), but a report by the US Environmental Protection Agency (EPA) concluded that untreated greywater has characteristics similar to domestic sewage and may even that there may also be high concentrations of certain pollutants. For example, fecal coliform concentrations in untreated vessel greywater are one to three times higher than in untreated household wastewater! Worse, unlike sewage, the discharge of greywater is not regulated in most parts of the world, meaning ships can discharge greywater directly into the ocean without any treatment.
Fortunately, this is not the case in Alaska. Alaska has needed both sewage and graywater from large passenger ships by the Advanced Wastewater Treatment System (AWTS) for nearly 20 years. In that time, the state has sampled greywater and sewage discharge from passenger ships in its waters.
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The Ocean Conservancy worked with an outside expert to analyze 19 years of data from Alaska’s sampling program. earlier this year, We released the results of that analysis in a new report that summarizes the lessons learned and provides recommendations for the research needed to proceed and how to improve greywater management both in Alaska and internationally.
First, greywater is gross and cruise ships discharge a lot of it.
Sampling in Alaska confirms that untreated greywater contains bacteria, nutrients, solids and a variety of pollutants, some of which are at or above the level of raw sewage. These concentrations are high enough to impair human and environmental health. Data reported by ships in Alaska also shows that ships discharge much greater amounts of greywater than sewage. Greywater discharge is often eight to 12 times greater than sewage discharge.
Second, advanced wastewater treatment systems can work well.
The AWTS systems required on large ships are very effective in treating greywater. After vessels need to treat graywater with AWTS, their fecal coliform level is usually tested below the limit of detection. Similarly, solids and nutrients were extracted at a higher rate.
Third, good results are not automatic.
The mere presence of AWTS on a ship does not mean that ships treat wastewater according to Alaska standards at all times and in all locations. AWTS should be maintained and monitored to ensure good results. The data support the need for monitoring the performance of greywater treatment. The data also shows that non-AWTS treatments—used by many smaller cruise ship ships—have greater variability in their test results.
With its high concentrations and high values of pollutants and bacteria, it is concerning that, unlike sewage, is not handled internationally or even nationally in many parts of the world.
Data from the Alaska program shows that greywater can be treated to a level safe for discharge. Performance monitoring through sampling of graywater and sewage discharge in Alaska can be used as an example for future requirements on graywater elsewhere in the world.
An important step is to ensure that the International Maritime Organization (IMO) – the United Nations body that regulates international shipping – takes action to address and regulate greywater. The IMO regulates other forms of waste from ships, including sewage, ballast water and exhaust gas cleaners. Greywater – with its high levels of bacteria and nutrients and potential toxins – deserves equal levels of attention. While achieving IMO regulation of greywater will take years, ocean conservation will continue to outstrip the importance of such a measure.
Post Untreated greywater is gross – we need to do better for our ocean first appeared ocean protection.
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