There is black water, otherwise known as human sewage. This is the waste from cruise ship toilets and medical facilities. A cruise ship produces more than eight gallons of sewage per day per person. The cumulative amount per day for a mid-sized ship is more than 40,000 gallons; almost 300,000 gallons on a one week cruise. These wastes contain harmful bacteria, pathogens, disease, viruses, intestinal parasites and harmful nutrients. If not adequately treated they can cause bacterial and viral contamination of fisheries and shellfish beds. In addition, nutrients in sewage, such as nitrogen and phosphorous, promote algal growth. Algae consume oxygen in the water that can be detrimental or lethal to fish and other aquatic life.
In Canada, sewage treated by a Marine Sanitation Device (MSD) can be discharged beyond four miles of the shore; sewage treated by an Advanced Wastewater Treatment System (AWTS) is unregulated. MSDs have been found to not perform up to standards, producing results labeled by Alaska's governor as “disgusting and disgraceful.” The waste from an AWTS is considerably better, however there are still problems with nutrient loading and with inadequate treatment of constituents such as ammonia, zinc, copper, zinc, phosphorous, and nitrogen. In 2009, 72 percent of the ships permitted to discharge waste from an AWTS in Alaska were found at least once to be out of compliance with Alaska Water Quality Standards.
A second type of waste water is graywater. Its release is unregulated in Canada, which is out of step with our neighbors to the north (Alaska) and south (Washington), where there are clear regulations. Gray water is waste water from sinks, showers, galleys, laundry, and cleaning activities aboard a ship. It is the largest source of liquid waste from a cruise ship: as much as 90 gallons per day per person; nearly half a million gallons per day for a mid-sized ship. Like sewage, gray water can contain a variety of pollutants. These include fecal coliform bacteria, detergents, oil and grease, metals, organic petroleum hydrocarbons, nutrients, food waste and medical and dental waste. The greatest threat posed by gray water is from nutrients and other oxygen-demanding materials. The cruise industry characterizes gray water as innocuous, at worst. A 2008 report from the U.S. EPA disagrees, stating that “…untreated graywater from cruise ships can contain pollutants at variable strengths and that it can contain levels of fecal coliform bacteria several times greater than is typically found in untreated domestic wastewater. Graywater has potential to cause adverse environmental effects because of concentrations of nutrients and other oxygen-demanding materials, in particular.”
Cruise ships also produce sewage sludge – about 4,000 gallons per day. The sludge poses the same problem as sewage, but in a more concentrated form. Sludge and biosolids are not permitted for discharge within 12 miles of the shoreline in Washington, but in Canada it can be discharged beyond four miles. This means that cruise ships empty their holding tanks in Canadian waters before crossing into Washington state waters. It is interesting to note that ships in Vancouver for the Olympics were required to connect to Metro Vancouver’s sanitary sewer and pump barges to properly dispose of liquid waste, but ships homeporting or visiting Vancouver have no similar requirements. In fact, gray water is not regulated by Canada – it is not even mentioned in Canada’s Regulations for the Prevention of Pollution from Ships and for Dangerous Chemicals.
Cruise ships also produce huge volumes of solid waste – as much as 3.5 kilograms per passenger per day – accounting for 24% of solid waste from all ocean-going vessels. Some of this waste is recycled, some is incinerated, and some is thrown into the ocean. As long as the waste can fit through a 2.5 centimetre screen it can be discharged beyond three miles from shore. These food wastes can contribute to increases in biological oxygen demand, chemical oxygen demand, and total organic carbon, diminish water and sediment quality, adversely effect marine biota, increase turbidity, and elevate nutrient levels. They may be detrimental to fish digestion and health and cause nutrient pollution. An additional problem with discharging food waste at sea is the inadvertent discharge of plastics.