Environmental Engineering Reference
In-Depth Information
discharge of bilge water and other types of engine room wastewaters within their jurisdic-
tion.
5
Establishment of such regulations are due, in part, to the lack of shipboard treatment
systems that have the ability to remove dissolved contaminants such as antifreeze, gasoline,
surfactants, and cleaning agents. Moreover, while at dock, there exists the ability to pump
bilge water to shore where a more extensive treatment infrastructure can be installed. It is
uncertain whether stricter international regulations will be developed as maritime trafic
increases and ever-larger ocean transport vessels are being built. Using statistics from the
Port of Los Angeles, total tonnage to the port has increased from 26.2 million metric tons
(MT) in 1973 to 158.2 million MT in 2011, a nearly 6-fold increase.
6
It may be time to reex-
amine wastewater discharge regulations from an international perspective to ensure the
environmental quality of the oceans. However, enforcement of regulations is dificult while
ships are in transit in international waters. Veriication of MARPOL regulations is currently
accomplished through the use of oil-in-water monitors and appropriate logbooks.
Ballast water has a different management strategy as the water is typically free of chemi-
cal contaminants. The concern is that the water is transported en masse from port to port
and may contain invasive species or pathogens when discharged in a new environment.
7
It has been hypothesized that the North American invasion of freshwater zebra mussels
occurred via ballast water discharged by ocean-going ships en route from the Black and/
or Caspian seas.
8,9
Treatment of ballast water generally involves either iltration or chlo-
rination of the water before discharge to remove or kill organisms, respectively.
10
Some
port facilities have ballast water exchange systems that prevent discharge of water into the
environment. Overall, technologies to manage ballast water are relatively mature with a
reduced need for advanced technologies outside of monitoring.
The composition of bilge water varies among vessels. Bilge luids are becoming more
complex owing to the sources of contamination from oil additives, solvents, and particles
contained within the various potential input streams (Figure 7.1).
11
Certain waste streams,
Sludge water
from oil
storage tanks
Soot from
economizer
wash water
Piston cooling
water
Wa sh-down
operations
Oil leaks from
machinery
Suspended and
colloidal particles,
detergents and
solvents
Suspended iron,
biological
detritus, oil
Suspended and
colloidal particles,
oxidized carbon
Suspended
particulates, oil,
and antifreeze
Oil and oil
additives
Leads to emulsions and
sources of dissolved
organics
Adds discoloration and
potentially dissolved
organics
OCM
Oil-water
separator
Overboard
discharge
Bilge water
FIGURE 7.1
Diagram of the various bilge water contaminant sources. OCM, oil content monitor.
