Marine Sewage Treatment Plant belongs to the key devices for prevention of pollution from ship in seas and oceans according to the revised Annex IV of the International Convention of the Prevention of Pollution (MARPOL 73/78).The resolution MEPC.2 (VI) adopted on 3 December 1976 is the present guidelines on implementation of effluent standards and performance tests for STP.which is called "old standards".This device is according to the resolution MEPC.159(55) enacted on 13 October 2006,which is called "new standards".The convention (MARPOL 73/78) provides that all STPs installed on board on or after 1 January 2010 should meet the resolution MEPC 159(55).The different effluent standards and days for type test in some organizations are as follows: