2.3 Wastewaters

2.3.1 Compliance with MARPOL 73/78
Ships granted with the additional class notation CLEANSHIP or CLEANSHIP AWT have to comply with the relevant requirements of MARPOL 73/78, Annex IV, revised according to IMO Resolution MEPC.115(51):

• Reg. 10 for standard discharge connection
• Reg. 11 for discharge criteria.

2.3.2 Design and arrangement of the sewage and grey water systems
The ship is to be fitted with a sewage and grey water system designed and arranged in accordance with item a) or item b) below:

1. Collected sewage is to be stored in an untreated sewage holding tank then:
   • treated in an approved sewage treatment plant or sewage comminuting and disinfecting system, then discharged to sea when authorised, or
   • discharged ashore.
   Collected grey waters are to be led to a grey water holding tank then:
   • discharged to sea when authorized, or
   • discharged ashore.
   Galley grey water is to be collected separately from other grey water and led through a grease trap prior to storage or discharge.
   The sewage and grey water collecting and discharge lines and tanks are to be separated.
2. Collected sewage is to be treated in an approved sewage treatment plant or sewage comminuting and disinfecting system then:
   • stored in a treated sewage holding tank, or
   • discharged to sea when authorized, or
   • discharged ashore.
   Collected grey waters are to be led to a grey water holding tank then:
   • discharged to sea when authorized, or
   • discharged ashore.
   Galley grey water is to be collected separately from other grey water and led through a grease trap prior to storage or discharge.
   Treated sewage and grey water holding tanks may be combined together.

2.3.3 Holding tanks
Holding tanks for sewage and grey water are to be of sufficient capacity to allow storage during the number of days of the no discharge period, having regard to the operation of the ship, the maximum number of persons on board, the daily production of wastewater given in Tab 1 and other relevant factors.
The holding tanks are to be efficiently protected against corrosion and fitted with a level indicator and a high level alarm.

2.3.4 Sewage treatment plants and piping
Sewage treatment plants are to be of a type approved in accordance with the effluent standards provided in Ch 9, App 1.
Provisions are to be made in the design for easy access points for the purpose of obtaining representative influent and effluent samples.
Plastic garbage is to be separated from sewage and/or grey water before entering the treatment unit.
The sewage piping system is to be designed taking into consideration the possible generation of toxic and flammable gases (such as hydrogen sulfide, methane, ammonia) during the sewage treatment.
Air pipes from the sewage and grey water systems are to be independent of all other air pipes and to be led to the outside of the ship, away from any air intake.

2.3.5 Sewage sludges
Sludges from sewage treatment are to be collected and stored then discharged ashore or incinerated onboard.
Incineration devices are to completely burn the sludges to a dry and inert ash and not to discharge fly ash, malodors or toxic substances.
Ashes from sludge incineration are be disposed ashore except where permitted under [2.4.7].

2.3.6 Discharge records
Provisions are to be made to record the following parameters related to the sewage and grey water discharge:

• date and time of discharge
• position of the ship (latitude and longitude)
• quantity of sewage or grey water discharged
• quantity of sludges discharged ashore.