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 TM 55-1905-222-14
c. The sewage flows by gravity from the receiving tank into the first of four compartments in the treatment
tank. The sewage follows the same over and under flow path as In the receiving tank. The first three
compartments provide for further sedimentation and anaerobic decomposition before entering the final
chamber. An electric motor-pump installed on the treatment tank pumps the clarified effluent from the final
chamber to the filter-disinfector at a rate of 021 gpm. The pump is controlled by a float switch which is
attached to the suction pipe and suspended from the hatch cover on the final chamber of the treatment tank.
d. The filter assembly is a standard water filter The filter housing can be unscrewed from the cap, permitting
easy replacement of the 50 micron filter element. The element can be washed and reused several times. The
sewage liquor is pumped through the filter element into the disinfection unit. The outlet of the filter has a built-
in check valve to prevent backflow of liquid chlorine into the filter housing. The tablets of solid disinfecting
agents inside the disinfector dissolve at a rate that provides for a three to six week period between recharge
operations, depending on flow conditions. The maximum capacity is seven tablets.
e. The effluent flows by gravity from the disinfector into the retention canisters. The retention canisters
provide the proper residence time for oxidation of solid matter and disinfection of the liquid effluent. The
effluent is discharged overboard from the retention canisters.
f. The marine head or "skipper" features a foot pedal and a smooth working easily accessible vertical pump
handle. The seacock allows sea water into the bowl when the foot pedal is engaged. The three-way valve
permits flushing the toilet through the MSD or directly overboard when the vessel is in the open sea. The swing
check valve in the sewage discharge line prevents backflow.
g. The rotary switch is used to furnish electrical power to the pump motor to operate the marine sanitation
device.
1-23.2 Treatment Method.
a. The sewage system uses a combination of sewage treatment principles to achieve a safe acceptable
effluent. The incoming sewage is subjected to sedimentation in the receiving and treatment tanks. While the
sewage passes through these tanks it is subjected to a second treatment, natural decomposition by anaerobic
action. This natural action is accelerated by the addition of selected bacteria for use in the digestion and
liquification of sewage. These enzymes reduce the complex fats, proteins and carbohydrates in the sewage to
stable sludge through a chain of reactions. The bacteria supplements the action of the enzymes as well as to
attack and liquify the fibrous components of raw sewage. The temperature at which the enzyme-bacterial
action Is most effective is 86F(30C).
b. The third treatment is a filtration stage consisting of final removal of all particles above 50 microns that
have passed through the preceding stages of treatment If the recommended flush water is exceeded, solids will
not be separated from the liquor and the filter will become clogged. The final stage of treatment consists of
chlorination which disinfects the effluent. The residence time in the retention canisters is approximately 5
minutes. The oxidizing action of the chlorine solution not only results in elimination of pathogens but also
reduces the biochemical oxygen demand (BOD) of the effluent.
1-37
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