Environmental Engineering Reference
In-Depth Information
7
Bilge and Ballast Water Treatment
Using Nan
otechnology
Paul L. Edmiston
Department of Chemistry, The College of Wooster and ABSMaterials Inc., Wooster, Ohio, USA
CONTENTS
7.1 Introduction ........................................................................................................................ 127
7.2 Overview of Current Practices ......................................................................................... 129
7.3 Membrane Separation ....................................................................................................... 130
7.3.1 Nanotechnology-Based Membranes ................................................................... 130
7.3.2 Hydrophobic Mesh Coatings ............................................................................... 132
7.3.3 Nanoiber-Based Membranes ............................................................................... 134
7.4 Adsorbents .......................................................................................................................... 135
7.4.1 Surface-Modiied Mineral Particles .................................................................... 135
7.4.2 Organoclays and Modiied Polymers ................................................................. 137
7.4.3 Nanoengineered Animated Organosilica .......................................................... 137
7.4.3.1 Physical Characteristics.......................................................................... 137
7.4.3.2 Removal of Dispersed and Dissolved Oil ........................................... 138
7.4.3.3 Regeneration ............................................................................................ 139
7.5 Comparative Technology Status and Future of Bilge Water Management ............... 139
References ..................................................................................................................................... 141
7.1 Introduction
A generally unrecognized, yet important, challenge in environmental protection is the
disposal of wastewater generated by maritime vessels. Every ship must manage water
associated with bilge pumping and ballast tank level control. Of the two types, bilge water
poses the greater challenge in disposal owing to the presence of solids, colloids, and met-
als, in addition to free and dissolved oil. The volume of bilge water produced ranges from
0.5 to 50 m
3
/day (150-65,000 gal/day) depending on the size of the vessel.
1
A study of cruise
liners sailing in Alaskan waters indicated discharge rates of 25,000 gal/week.
2
Despite the
large volume, bilge water only represents about 20% of the several million tons of oily
wastewater discharged annually from seagoing vessels.
3
Other sources of water include
engine or turbine wash water, exhaust gas scrubbing, and boiler economizer blowdowns.
The International Maritime Organization (IMO) speciied in 1973 that bilge water dis-
charged into the sea must have a residual oil content below 15 ppm.
4
(This rule is often
referred to as MARPOL 73/78 as the protocol was modiied and ratiied in 1978.) In the
subsequent 40 years, many ports have developed regulations that are more stringent in
terms of water quality requirements. The ports of Long Beach and Los Angeles prohibit the
127
