5.1 Testing of the operational performance of a sewage
treatment plant should be conducted in accordance with the following
subparagraphs. Unless otherwise noted, the subparagraphs apply to testing both
onboard and ashore.
5.2 Raw sewage
quality
5.2.1 Sewage treatment
plants tested ashore - the influent should be fresh sewage consisting of faecal
matter, urine, toilet paper and flush water to which, for testing purposes
primary sewage sludge has been added as necessary to attain a minimum total
suspended solids concentration appropriate for the number of persons and
hydraulic loading for which the sewage treatment plant will be certified. The
testing should take into account the type of system (for example vacuum or
gravity toilets) and any water or greywater that may be added for flushing to
the sewage before treatment. In any case the influent concentration of total
suspended solids should be no less than 500 mg/l.
5.2.2 Sewage treatment plants tested onboard
- the influent may consist of the sewage generated under normal operational
conditions. In any case the average influent concentration of total suspended
solids should be no less than 500 mg/l.
5.3 Duration and timing of test
5.3.1 The duration of the test period should be a minimum
of 10 days and should be timed to capture normal operational conditions, taking
into account the type of system and the number of persons and hydraulic loading
for which the sewage treatment plant will be type approved. The test should
commence after steady-state conditions have been reached by the sewage treatment
plant under test.
5.4 Loading
factors
5.4.1 During the test
period the sewage treatment plant should be tested under conditions of minimum,
average and maximum volumetric loadings.
- For testing ashore, these loadings will be as laid down in the
manufacturer’s specifications. Figure 1 shows suggested timings for sampling
each loading factor.
- For testing onboard, minimum loading will represent that generated by the
number of persons on the ship when it is alongside in port, and average and
maximum loadings will represent those generated by the number of persons on
the ship at sea and will take account of meal times and watch rotations.
5.4.2 The Administration should undertake to assess the
capability of the sewage treatment plant to produce an effluent in accordance
with the standards prescribed by section 4 following minimum, average and
maximum volumetric loadings. The range of conditions under which the effluent
standards were met should be recorded on the Certificate of Type Approval. The
form of the Certificate of Type Approval and appendix is set out in the annex to
these Guidelines. 5.5 Sampling methods and frequency
5.5 Sampling methods and frequency
5.5.1 Administrations should ensure that the
sewage treatment plant is installed in a manner which facilitates the collection
of samples. Sampling should be carried out in a manner and at a frequency which
is representative of the effluent quality. Figure 1 provides a suggested
frequency for sampling, however, the frequency should take account of the
residence time of the influent in the sewage treatment plant. A minimum of 40
effluent samples should be collected to allow a statistical analysis of the
testing data (e.g. geometric mean, maximum, minimum, variance).
5.5.2 An influent sample should be
taken and analyzed for every effluent sample taken and the results recorded to
ensure compliance with section 4. If possible, additional influent and effluent
samples should be taken to allow for a margin of error. Samples should be
appropriately preserved prior to analysis particularly if there is to be a
significant delay between collection and analysis or during times of high
ambient temperature.
5.5.3 Any disinfectant residual in samples should be
neutralized when the sample is collected to prevent unrealistic bacteria kill or
chemical oxidation of organic matter by the disinfectant brought about by
artificially extended contact times. Chlorine (if used) concentration and pH
should be measured prior to neutralization.
Figure 1:
Suggested hydraulic loading factors and sampling frequency for
testing sewage
treatment plants. May be modified as necessary
to take account of characteristics of
individual sewage
treatment plants
5.6 Analytical testing of effluent
5.6.1 The Administration should give
consideration to the recording of other parameters in addition to those required
(thermotolerant coliforms, total suspended solids, BOD5, COD, pH and residual
chlorine) with a view to future technological development. Parameters which
might be considered include total solids, volatile solids, settlable solids,
volatile suspended solids, turbidity, total phosphorus, total organic carbon,
total coliforms and faecal streptococci.
5.7 Disinfectant residual
5.7.1 The potential adverse environmental
effects of many disinfectant residuals and by-products, such as those associated
with the use of chlorine or its compounds, are well recognized. It is,
therefore, recommended that Administrations encourage the use of ozone,
ultra-violet irradiation or any other disinfectants which minimize adverse
environmental effects, whilst pursuing the thermotolerant coliform standard.
When chlorine is used as a disinfectant, the Administration should be satisfied
that the best technical practice is used to keep the disinfectant residual in
the effluent below 0.5 mg/l.
5.8
Scaling considerations
5.8.1 Only full-scale marine sewage
treatment plants should be accepted for testing purposes. The Administration
may certify a range of the manufacturer’s equipment sizes employing the same
principles and technology, but due consideration must be given to limitations on
performance which might arise from scaling up or scaling down. In the case of
very large, very small or unique sewage treatment plants, certification may be
based on results of prototype tests. Where possible, confirmatory tests should
be performed on the final installation of such sewage treatment plants.
5.9 Environmental testing of the
sewage treatment plant
5.9.1 The Administration should be satisfied
that the sewage treatment plant can operate under conditions of tilt consistent
with internationally acceptable shipboard practice.
5.9.2 Tests for certification should be
carried out over the range of temperature and salinity specified by the
manufacturer, and the Administration should be satisfied that such
specifications are adequate for the conditions under which the equipment must
operate.
5.9.3 Control
and sensor components should be subjected to environmental testing to verify
their suitability for marine use. The Test Specifications section in part 3 of
the annex to resolution MEPC.107(49) provides guidance in this respect.
5.9.4 Any limitation on the
conditions of operation should be recorded on the Certificate.
5.9.5 The Administration should also
consider requiring the manufacturer to include in the operating and maintenance
manuals, a list of chemicals and materials suitable for use in the operation of
the sewage treatment plant.
5.10
Other considerations
5.10.1 The type and model of the sewage
treatment plant and the name of the manufacturer should be noted by means of a
durable label firmly affixed directly to the sewage treatment plant. This label
should include the date of manufacture and any operational or installation
limits considered necessary by the manufacturer or the Administration.
5.10.2 Administrations
should examine the manufacturer’s installation, operating and maintenance
manuals for adequacy and completeness. The ship should have on board at all
times a manual detailing the operational and maintenance procedures for the
sewage treatment plant.
5.10.3 Qualifications of testing facilities should be
carefully examined by the Administration as a prerequisite to their
participation in the testing programme. Every attempt should be made to assure
uniformity among the various facilities.