The marine domestic sewage treatment plant (biochemical method) is used to treat the fecal sewage from the toilet sewer of the ship, so that it reaches the international discharge standard and is discharged to the outboard. It can also be used for disinfecting the gray water on the boat (referring to kitchen washing water, bathroom bath water, washing water and washing water discharged from the ship).

The principles are summarized as follows: biological wastewater treatment plant (marine sewage treatment system) is used to treat marine sewage by biological contact oxidation and physicochemical treatment and disinfection principle. It is composed of five cabinets: aeration cabinet, contact oxidation cabinet, sedimentation tank and disinfection cabinet. In the aeration cabinet, the activated sludge micelles based on aerobic bacteria form a floc like floc with sticky floc to adsorb organic matter, and become harmless carbon dioxide and water under the condition of oxygen filling, and the activated sludge is propagated, and the soft fillers are suspended in the contact oxidation cabinet to be a biofilm, and the organic matter is further eliminated. The activated sludge deposits accumulated in the sedimentation tank are then returned to the aerator as the bacteria and reproduced and retreated; the treated sewage is finally entered into the disinfector with chlorine containing drugs, and then discharged from the discharge pump to the outboard.