Some confusion over the implementation of the regulation MEPC 227(64), which governs the release of treated waste water from ships and was adopted on 5 October 2012, has arisen with the IMO clarifying the situation as following flawed interpretations from a number of sources.
According to the IMO the resolution MEPC 227(64) did come into force on 1 January 2016 and all its requirements will be enforced from this date except the elements concerning the concentrations of phosphorous and nitrogen, MEPC (69), which takes place in April, will consider the entry into force dates and an announcement on that issue should be expected following that meeting.
Essentially MEPC 227(64) will apply to sewage treatment plants installed on or after 1 January 2016 on ships, other than passenger ships, in all areas and passenger ships outside MARPOL Annex IV special areas. Currently the only ‘special area’ designated is the Baltic Sea, though there is an expectation that new areas will be stipulated in the near future.
The requirements of these Guidelines, including those in section 4.2, will apply to sewage treatment plants installed on new passenger ships when operating in a MARPOL Annex IV special area and intending to discharge treated sewage effluent into the sea on or after 1 January 2016 and on existing passenger ships when operating in a MARPOL Annex IV special area and intending to discharge treated sewage effluent into the sea on or after 1 January 2018.
Sewage treatment plants installed prior to 1 January 2016 and on or after 1 January 2010, on ships other than passenger ships operating in MARPOL Annex IV special areas and intending to discharge treated sewage effluent into the sea, should comply with the earlier resolution MEPC.159 (55). Sewage treatment plants installed prior to 1 January 2010 on ships other than passenger ships operating in MARPOL Annex IV special areas and intending to discharge treated sewage effluent into the sea, should comply with resolution MEPC.2 (VI).
In order to meet the required standards vessel owners and operators will need to use an approved waste water treatment plant to process grey water, that is water from showers and galleys and black water which comes from toilets and may contain faecal matter.
However, the IMO stipulates that: “an approved sewage treatment plant should not rely solely on the dilution
Treatment of effluent should meet the standards required by the IMO, that is, “The geometric mean of the thermotolerant coliform count of the samples of effluent taken during the test period should not exceed 100 thermotolerant coliforms/100ml as determined by membrane filter, multiple tube fermentation or an equivalent analytical procedure.”
In addition, the Total Suspended Solids (TSS) content of the samples of effluent taken during the test period should not exceed 35 Qi/Qe mg/l, where Qi is influent and Qe is effluent.
Meanwhile the IMO stipulates that the method of testing either be through filtration of a representative sample through a 0.45μm filter, followed by drying at 105°C and weighing. An alternative would be the centrifuging of a representative sample (for at least five minutes with mean acceleration of 2,800-3,200g), drying at a minimum of 105°C and weighing or any other internationally accepted equivalent
The IMO advises that: “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.”
According to ACO Marine MD Mark Beavis, which along with a number of other manufacturers, including, RWO, Scanship, Wärtsilä Hamworthy and Selmar’s Blue Sea technology among others, is in a position to offer an approved waste water treatment system: “Currently the Baltic Sea is the only IMO designated Special Area, but other areas are applying for special area status and so there would potentially be a wider impact on passenger ship operations. Owners and yards really do need to start specifying plant now if they are to comply with the new rules in time.”
The IMO says for the purpose of regulation 9.2.1 of MARPOL Annex IV, a sewage treatment plant installed on a passenger ship that intends to discharge sewage effluent in special areas should additionally meet the nitrogen and phosphorus removal standard when tested for its Certificate of Type.
The geometric mean of the total nitrogen and phosphorus content of the samples of effluent taken during the test period should
Total nitrogen: 20 Qi/Qe mg/l or at least a 70% reduction
Total phosphorus: 1.0 Qi/Qe mg/l or at least an 80% reduction.
The method of testing should meet either the ISO 29441:2010 standard for nitrogen and the ISO 6878:2004 standard for phosphorus or other internationally accepted equivalent test standards.
According to Lloyd’s Register MEPC 67 reviewed the nitrogen and phosphorus removal standards in the 2012 Guidelines on the implementation of effluent standards and performance tests for sewage treatment plants and the conclusion was that, “While there was concern about [the] availability of treatment systems meeting the MEPC.227(64) requirements, the majority view reflected a high degree of confidence that such treatment systems will be available. Subsequently, MEPC 67 decided not to revise (lower) the nitrogen and phosphorus removal standard given in paragraph 4.2.1 of the resolution.”