Annex IV of IMO’s MARPOL Convention, adopted 40 years ago, set ambitious standards for ship black water discharges, but there are two shortfalls: firstly, grey water is not regulated, and secondly (and uniquely), there is no requirement for sewage discharges from ships to be monitored.
Alaska took the problem into its own hands in 2000 with the introduction of both grey water regulations and monitoring of discharges for passenger ships. “People know very well now that grey water is actually as polluting, if not more polluting, than sewage. On passenger and cruise ships, grey water is up to 10 times the volume of black water, so the pollution of the marine environment can be quite significant,” says Wei Chen, R&D manager for waste water systems at Wärtsilä.
In addition to Alaska’s clean-up efforts, the Great Lakes, US waters (EPA Vessel General Permit, 2013) and inland waterways in Europe (2012/49/EU) have also regulated grey water treatment in various shapes and forms, each affecting certain shipping sectors. This means there are four sets of different type approval specifications and more than five different compliance regimes to baffle vendors and ship operators. This lack of a universal approach has resulted in confusion regarding equipment selection, system design and operations.
All the major classification societies have introduced green notations for ships that treat grey water. This hasn’t really solved the problem, says Mr Chen, and most of the requirements of these notations are vague. “At least 95% of conventional sewage treatment plant vendors claim they can do black and grey water. That has been going on for many years. However, putting grey water through the final stage of a multi-stage black water treatment system is not really treating grey water, and it is compromising the performance of the type approved sewage treatment system.”
Even without grey water treatment, sewage treatment plants are failing to meet the earliest MARPOL requirements which are stricter than most land-based sewage discharge limits. In 2012, the Netherlands tabled a study at IMO on the results of testing the sewage treatment plants on 32 ships in Rotterdam. The vast majority of systems didn’t meet the requirements. Rather, most exceeded the requirements by 100 to 1,000 times.
Mr Chen points to the lack of monitoring as a major contributor to the situation. “There is no monitoring requirement in MARPOL Annex IV. What is relied upon is the type approval certificate of the equipment which is obtained from a test done on shore, almost under laboratory conditions.”
This has not proven to be effective enough, he says. “Compliance checking is a very basic principle for environmental regulations to work effectively. It is a big weakness in MARPOL Annex IV, that even after 40 years it hasn’t included any monitoring requirement.” Mr Chen contrasts this with regulations relating to oily water separators, ballast water treatment, garbage and even air emissions from the stack. The regulation of each of these has, or is developing, compliance monitoring systems.
The black water regulations under MARPOL are moving in the one, increasingly stringent direction. MEPC.2(VI) was tightened over the last five years, not once with MEPC.159(55), but twice with MEPC.227(64) which is entering into force in 2016. "What’s the point?" asks Mr Chen, "if systems aren’t meeting the older standards anyway, and no mechanisms are in place for port state control to act."
However, MEPC.227(64) has taken a step forward in the type approval process. There has been a class of sewage treatment plants that relies on dilution to meet the requirements, he says. Seawater is pumped into these systems at a rate of up to 40 times the volume of sewage being processed. The new requirements now take this into account during type approval testing to ensure treatment rather than just dilution.
The main change in MEPC.227(64) is the designation of the Baltic Sea as a Special Area for sewage discharge. As a result of eutrophication problems in the sea, stricter limits will be set on nutrient discharge. The topic was hotly debated at IMO, as these ships only account for 0.03% of the nutrient problem. Land-based sources are much higher, for example, agricultural discharges account for around 40% of the excess nutrient.
The advanced waste water treatment systems used on many cruise ships can meet the requirements set out by Special Area regulations and other Annex IV regulations too, even if they are a step up in price and complexity compared to what would normally be installed on a cargo vessel. Passenger ferries in the Baltic are unlikely to use them. Instead they will rely on the port reception facilities that must be made available as part of the Special Area designation.
Washington State is introducing legislation for its own special area that will forbid the discharge of any black water in Puget Sound. This again negates the need for ships to use advanced waste water treatment systems even though these systems produce treated wastewater of much higher qualities than that from the local municipal wastewater treatment works. It also brings compromises. “If you force a ship to hold waste water for longer periods, and they have to dash out and discharge, you end up causing higher air emissions,” says Mr Chen.
Ironically, Alaska, the state that introduced stricter regulations back in 2000, is now looking to relax them a bit. The reason? After monitoring performance they have realised that the requirements were unnecessarily and unrealistically strict. For Mr Chen, it is a sign, again, of the importance of monitoring regulations and working with all stakeholders to achieve a workable result that really does protect the marine environment.