February 2024

Membrane Bioreactors in Sewage Treatment Plants

Month/Year: February 2024

Name/Rank: Toplikiotis Anastasios, Third Engineer

Theme: Membrane Bioreactors in Sewage Treatment Plants


During a «MARPOL – Environmental Compliance» seminar in February 2024, the 3rd Engineer Officer Tasos Toplikiotis voluntarily undertook to study the operation manuals of a number of different Sewage Treatment Plants installed in Minerva Marine vessels and especially in DOUKATO, LITTLE EMMA, MINERVA ALEXANDRA, MINERVA KALLISTO and MINERVA OLYMPIA.

The idea came from the current developments in the review of the performance standard of treatment plants, the difficulties of ships to monitor the process of activated sludge, the need of treating both the grey waters and sewage and other reasons. Of particular interest was the MBR type (membrane bioreactor) that consists of an equalizing tank and a membrane unit submerged in the aeration tank which in turn includes a number of membrane panels sealed on both sides. Air is distributed from the air blowers and diffusers providing the required oxygen for the decomposition of the organic matter while treated effluent is practically filtered through the membrane by pressure. The design of the MBR practically combines the filtration with the assistance of membranes and the oxygen assisted biological process replacing the need for a separate aeration and settling tank in the conventional systems. There is an increased automation and control level, while at the same time if an ocean going ship needs to sail in areas that more environmental protection is required (such as a Special Area for sewage) the system can be supplemented with an additional module.

The 3rd Engineer went through the existing requirements of the Annex IV of MARPOL, the environmental and operational advantages of the treatment plants against the macerating/disinfection systems, the proper operation and maintenance procedures, the size of the holding tank and other information.