4.1 For the purpose of regulations 9.1.1 and 9.2.1 of MARPOL Annex IV, a sewage treatment
plant should meet the following effluent standards when tested for
its Certificate of Type Approval by the Administration:
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.1 Thermotolerant Coliform Standard
The geometric mean of the thermotolerant coliform count of the
samples of effluent taken during the test period should not exceed
100 thermotolerant coliforms/100 ml as determined by membrane filter,
multiple tube fermentation or an equivalent analytical procedure.
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.2 Total Suspended Solids (TSS) Standard
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.1 The geometric mean of the total suspended solids
content of the samples of effluent taken during the test period should
not exceed 35 Qi/Qe mg/l.
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.2 Where the sewage treatment plant is tested
on board ship, the maximum total suspended solids content of the samples
of effluent taken during the test period may be adjusted to take account
of the total suspended solid content of the flushing water. In allowing
this adjustment in maximum TSS, Administrations should ensure sufficient
tests of TSS are taken of the flushing water throughout the testing
period to establish an accurate geometric mean to be used as the adjustment
figure (defined as x). In no cases should the maximum allowed TSS
be greater than (35 plus x) Qi/Qe mg/l.
Method of testing
should be by:
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.1 filtration of representative sample through
a 0.45 μm filter membrane, drying at 105°C and weighing; or
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.2 centrifuging of a representative sample (for
at least five minutes with mean acceleration of 2,800-3,200 g), drying
at least 105°C and weighing; or
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.3 other internationally accepted equivalent test
standard.
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.3 Biochemical oxygen demand without nitrification
and chemical oxygen demand
Administrations should ensure the sewage treatment plant is
designed to reduce both soluble and insoluble organic substances to
meet the requirement that, the geometric mean of 5-day biochemical
oxygen demand without nitrification (BOD5 without nitrification)
of the samples of effluent taken during the test period does not exceed
25 Qi/Qe mg/l and the chemical oxygen demand (COD) does not exceed
125 Qi/Qe mg/l. The test method standard should be ISO 5815 1:2003
for BOD5 without nitrification and ISO 15705:2002 for COD, or other
internationally accepted equivalent test standards.
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.4 pH
The pH of the samples of effluent taken during the test period
should be between 6 and 8.5.
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.5 Zero or non-detected values
For thermotolerant coliforms zero values should be replaced
with a value of 1 thermotolerant coliform/100 ml to allow the calculation
of the geometric mean. For total suspended solids, biochemical oxygen
demand without nitrification and chemical oxygen demand values below
the limit of detection should be replaced with one half the limit
of detection to allow the calculation of the geometric mean.
4.2 For the purpose of regulation 9.2.1 of MARPOL Annex IV, a sewage treatment plant
installed on a passenger ship intending to discharge sewage effluent
in special areas should additionally meet the following effluent standards
when tested for its Certificate of Type Approval by the Administration:
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.1 Nitrogen and phosphorus removal standard
The geometric mean of the total nitrogen and phosphorus content
of the samples of effluent taken during the test period should not
exceed:
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.2 Method of testing should be:
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.1 ISO 29441:2010 for total nitrogen; and
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.2 ISO 6878:2004 for total phosphorus; or
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.3 other internationally accepted equivalent test
standard.
4.3 Where the sewage treatment plant has been
tested ashore, the initial survey should include installation and
commissioning of the sewage treatment plant.