Celebrity Cruises has four ships with gas-turbine engines, which release 80 percent to 95 percent less sulfur, fine particles, and nitrogen oxides, said Rich Pruitt, Royal Caribbean's director of environmental programs.
Other efforts include the Cruise Lines International Association's work with Conservation International scientists to develop a global map of coral reefs, shellfish beds, and other sensitive areas. The lines would then avoid discharging untreated wastewater within 6.5km of these places.
But some say more can be done. Teri Shore, the Bluewater Network's clean vessels campaign director, noted that while the advanced wastewater treatment systems are meeting legal criteria for removing germs from ship effluent, they do not treat contaminants like metals or nutrients.
To see how well new wastewater treatment systems actually work, the Environmental Protection Agency sampled wastewater from four large cruise ships in 2004 in Alaska. The data showed that they indeed seemed to remove germs, but "there are some questions we have on the nutrients and the metals," the agency's assistant administrator for water, Benjamin Grumbles, said.
The EPA is now testing the impact of wastewater nutrients and metals on marine life, and said it hoped to propose a ruling by the end of this year on whether it needs to set additional standards for waste discharges in Alaska.
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