wastewater
A black and grey perspective on wastewater rules
Forty years after Annex IV of the MARPOL Convention was adopted and 10 years after it entered into force, Wei Chen, head of research and development at Wärtsilä Water Systems, looks at how it protects marine water against pollution from ships’ sewage
NO one can be sure exactly how Annex IV of the MARPOL Convention serves to protect marine water against sewage pollution from ships, said head of research and development at Wärtsilä Water Systems Wei Chen. After all, he pointed out, there is no monitoring of discharges from ships – rather, inspectors often rely on one thing: type approval certificates. But is this enough? In 2012, after a voluntary sampling programme of 32 ships
(including two small passenger ships), the Netherlands found “a vast majority of the equipment did not meet the existing sewage treatment standards due to improper use of detergent, lack of maintenance or not following the operational instructions” (MEPC64/23). Average performance missed the targets by a long way. So far, it is unclear how this important finding may be used for corrective actions. However, past experience in the US may serve a useful reference. In 2000, similarly poor performances were found on cruise ships operating in Alaska. The US state immediately introduced tougher limits which were more stringent than IMO standards (33CFR159.301 Subpart E). Importantly, for the first time in marine history, a sampling and monitoring regime was introduced for black and grey water discharge. The analysis results are published on the Alaska state’s web page. Grey water, which has high flow and contains high concentration of pollutants, was regulated to the same standards as black water. The industry reacted swiftly. Advanced wastewater treatment
(AWT) systems were developed. The challenges were immense, but improvement was dramatic. After detailed surveys in 2004, the US Environmental Protection Agency (EPA) concluded that AWTs are proven, and that they represent the ‘best available technologies’. The same stringent limits were later introduced to regulate ship’s grey water discharges in all US waters under EPA’s Vessel General Permit. It is interesting to note that these AWTs are not type approved against the Alaskan standards, as such procedures
56 I Passenger Ship Technology I 2nd Quarter 2013
Wärtsilä Water Systems’ membrane bio-reactors treat black and grey water separately
www.passengership.info
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