Waste management for ships and sea platforms - Shipbuilding & Water Transport
For those who have lived in the arms of the sea, the bond is powerful and eternal. When mariners discharge waste into the sea, it is not carelessness but desperation…a last resort used in the absence of practical alternatives. The waste generated on every ship comes from both people and machinery. People generate garbage and sewage. The various motors and shafts generate used oils, dirty rags and a wide variety of other waste. The mariner has three options for all this waste: (i) store it on board and discharge it at the next port; (ii) treat it on board; or (iii) discharge it at sea. Today, none of these options are practical.
Discharge at sea is extremely problematic. International laws limit the types of waste that can be discharged and the locations where such discharges are permitted. All waste must first be segregated to remove restricted items and then pulped or shredded prior to discharge. This practice requires significant labour resources and a wide variety of equipment. In any large ship, one will typically find young sailors sifting through garbage in an effort to remove plastic wrappers, cups, swizzle sticks and numerous other items before the remaining waste can be discharged. For ships with smaller crew size, the “pre-screening” of waste prior to discharge is rather impractical.
How practical is waste storage on board ships? In fact, it is problematic and potentially hazardous to people onboard. Storage areas smell and are infested with both bacteria and vermin. The longer the ship sails the more serious the problem becomes. Most ships transfer cargo over very long distances and stay at sea for many days at a time…long enough for waste to decompose and become a serious health risk for the crew. Some navies have tried to mitigate this problem by installing large refrigerated waste storing chambers, at significant cost and with other operational implications.
The obvious solution is to treat the organic, and potentially rotting, waste on board as it is being generated. Ships have been burning waste and treating sewage on board for the past two decades. The two principle technologies used are: (i) incineration for solid waste; and (ii) biological treatment for wastewater. Both of these technologies have been adapted from much larger land-based technologies and present significant operational problems.
Land-based incinerators require steady operation at very high temperature and a complex exhaust gas cleaning system to operate properly and minimize the emission of dangerous pollutants, such as dioxins. Ships however cannot operate incinerators in the same way as land-based facilities. Marine incinerators typically burn at much lower temperature, start and stop frequently and have minimal exhaust cleaning equipment. The result is poor emissions and high maintenance requirements. In fact, many fleets have tried and rejected incineration as a waste treatment option on board their ships.
Biological wastewater treatment systems have been used successfully in land-based communities. However, a ship does not offer the operational stability of a land-based facility. Wastewater treatment facilities for ships must handle frequent start-ups and shut-downs, large fluctuations in loads, constantly changing weather conditions and inexperienced operators. Such conditions make the use of biological wastewater treatment systems impractical for ships.
Mariners have been discharging waste at sea, either legally or illegally, since the first ships sailed. The marine industry needs a simple, practical and safe technology that will enable the elimination of both solid and liquid waste on board ships. International regulations alone cannot protect our seas until the mariners are given the practical tools to eliminate their waste.