SECTION III. PRINCIPLES OF OPERATION
1-10. Sanitary System General. FIGURE 1-2 illustrates how the sanitation device interfaces with other
external components in the sewage system. For the operation of these individual system components, refer to
1-11. System Functional Description.
The following describes the sanitation system design and the
sewage treatment process.
a. System Design.
(1) The Marine Sanitation Device is a self-contained unit. All of the major components are
located within the enclosure panels of the unit, with the exception of the chlorine storage
(2) The system is equipped with an electronic monitoring system which automatically controls
the treatment of sewage, warns of any motor shutdown, and pinpoints the problem motor. It
also warns of any treatment tank overload condition, thus avoiding damage to other system
components or to the vessel's electrical supply.
(3) The control system comprises two modular units. The junction box (control module)
(FIGURE 1-3) houses the electronic monitoring circuit and an in- line circuit breaker. The
Remote Status indicator, located in the engine room control center, is a panel which indicates
individual motor operating conditions, treatment tank overload, and the system operating
condition. This is accomplished with constantly lit or flashing panel lights (FIGURE 1-4).
Refer to TM 55-1905-223-10.
b. Treatment Process.
(1) The Marine Sanitation Device (MSD) processes sewage from existing facilities. Raw sewage
from the sanitation facilities is routed into the treatment tank (1, FIGURE 1-5) for maceration.
The macerated sewage is continuously recycled through the treatment tank until the solids
are small enough to pass through the retention/reduction screen (2). This screen is under a
continuous backwash by an impact sprinkler (3) to prevent a buildup of solids and
consequent plugging of the screen. After passing through the retention/reduction screen, the
effluent flows into a series of sedimentation tanks where the movement of solids is restricted,
forcing fallout of suspended matter. The solids that fall out are then returned to the treatment
tank by a sludge return pump for reprocessing.
(2) The effluent will finally pass through the sedimentation modules and be discharged
overboard. Disinfection of the effluent is achieved through liquid hypochlorination with
common household bleach, and by chemical oxidation within the treatment tank. This is
accomplished by using a metering system, which allows an appropriate amount of liquid
hypochlorite to flow from a storage container into the treatment tank. A high level warning
system is provided with the MSD to indicate a treatment tank full condition. This is done by
using a sensor suspended in the tank (4, FIGURE 1-5). The sensor is activated when an
80% tank capacity level is reached. This activation immediately turns on a warning light