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SHIPBOARD POLLUTION CONTROL: U.S. Navy Compliance With MARPOL Annex V
Submarine waste streams differ in some respects from the waste generated by surface ships. Table 7.2 gives Navy data obtained from brief surveys taken on two submarines. Surface ship waste generation data are included for comparison. The differences in the numbers are impressive. One must suppose that there is submarine-to-submarine variation that is substantial, but the accuracy of the data is probably not high. The data do support the diligent job the submariners have done in reducing unnecessary packaging materials.
It has been suggested that the cardboard portion (0.10 and 0.50, for the two submarines) is not discharged, but stored on board. With present practice, the weight of the metal TDU cans (including metal weights), which ranges from 0.26 to 0.61 lb/person/day, must be added to the submarine waste streams. These additional TDU metal weights are not included in Table 7.2, since they have no counterpart in the surface fleet and result solely from the current submarine discharge process. The data suggest that a storage volume as low as 0.01 ft3/person/day would be necessary to accommodate this waste if it is not discharged. This assumes a compaction ratio for the total waste stream of about 15, which is commercially obtainable.
Another important result of the shipboard surveys is that a substantial portion of the paper and plastic (but not the cardboard, metal, and glass) is food contaminated (Table 7.3). The compacted volume of the food-contaminated paper and plastic is not very large, less than 0.01 ft3/person/day, or about 1 ft3/day for the entire ship. If this waste cannot be eliminated and has to be stored under Annex V, storage in the frozen food lockers appears to be the only solution. Precautions to avoid contamination of unused supplies will be necessary.
Since submarines operate as closed systems leaving port with everything they will use aboard, an argument can be made that there is space to continue storing the Annex V waste rather than discharge it through the TDU. The waste-handling study (U.S. Navy, 1994) for the new design NSSN concluded that proper management of the solid waste stream could allow storage and eliminate any waste discharges. Again, food-contaminated waste materials would need special handling, probably storage in sealed cans held in the frozen food lockers. There appears to be a strong conservation ethic among submariners, and a number of crews have already voluntarily made significant reductions in the amount of solid waste discharged.
The consensus of the committee is that there are no technological solutions to the submarine waste problem beyond installation of garbage disposals, better compactors, and sealed storage packages. Thermal destruction in the submarine environment is not appealing. Further, the committee sees no route to an integrated solution to the larger waste problem going beyond Annex V. Submarines generate food waste, gray water, and black water in proportion to the complement. Present storage and discharge strategies have not been improved upon by committee deliberation. The submariners have done an excellent job on their own.
Table 7.2 Rate of Generation of Annex V Solid Waste (lb/person/day)