It is then predicted that there
are other unwanted passengers traveling in the bilge areas and
other damp dark places within ships that can cause problems
to the ships themselves. In water wells, these nuisance bacteria
can so substantially reduce water flow into a well that it has
to be abandoned. The developing practice in the water well industry
to prevent these infestations has evolved into the Sustainable
Water Well Initiative in Canada. The objective is to extend
the operating life span of wells by routine testing and suitable
preventative maintenance and/or radical treatment procedures,
depending upon the state of the bacterial infestation. In the
Canadian prairies, there are 200,000 operating wells that have
been found to have, on average, a life span of 15 years. The
capitalization of these wells has been estimated to be minimally
CAN$1 Billion and the annual replacement and/or rehabilitation
costs are CAN$67 Million.
In the maritime industry it is recognized that inspection of
a ship must be done on a routine basis. It is estimated that
20%, 320 ships of the world fleet of 1,744 tankers between 10,000-50,000-dwt
are 25 years of age or over, while more than 50 ships still
in operation were built in the 1960’s. The aging population
of tankers makes routine inspection a critical issue. This inspection
can be very expensive and time consuming. The sheer size of
today’s vessels makes this task daunting. Although there
are stated guidelines set by IACS (International Association
of Classification Societies, 1994), to follow when ship structures
are inspected, without the knowledge of the full breadth of
the problem these guidelines allow error, and in turn, possible
loss of structural integrity. The growth of rusticle's may be
a major factor affecting the operational life span of ships.
Studies to date have found that by using the biological knowledge
gained through the rusticle investigation, expanded guidelines
could be implemented. The inspection and diagnosis would involve
the following four stages:
I. Confirmation that rusticle's do grow
covertly in ocean going ships in manners that affect the sea
worthiness or structural integrity of the ship.
II. Development of thorough monitoring procedures
that would include video inspection, bacteriological examinations
for aggressivity, chemical analysis, etc.
III. Implementation of preventative maintenance
procedures to suppress the rusticle activity, or viable treatment
alternatives.
IV. Design strategies in ship construction
and operational procedures that would reduce the risk of biological
degradation to acceptable levels.
In the maritime industry, a similar scale
of impact on the life span of ships would also be causing
heavy replacement costs, pollution or unscheduled repairs.
These costs could be partially curtailed if the true level
of these microbial impacts was found to be significant and
controllable. In the shipping industry, there is also an average
life span for ships but sudden catastrophic sinking's continue
to occur on a regular basis. By improving detection and control
procedures to include microbial events that can weaken the
structure of the ship, it should be possible to lengthen the
life span of ships in much the same manner as water wells
are becoming more sustainable (Table One).
Rusticle's are a real, yet largely unrecognized, threat to
the long-term structural integrity of ships. A strategy could
be implemented to augment the existing inspection criteria
to include the monitoring and preventative maintenance procedures
to control biofouling. The initial focus for such investigations
would center on the bilge water and any “pooled”
water that may become entrapped within the ship’s structures.
The signatures for these potentially aggressive bacteria that
cause losses in steel strength include corrosive or extraction
processes. Table One is a list of the criteria that outlines
the detection of biological activity that may have the potential
to compromise the integrity of ship’s steel structures.
The list of criteria is based upon experiences in other industries.
There is a need for dedicated research and development to
address the problem of rusticle's and other microbial communities
having the capacity to cause sudden losses in steel strength
and integrity, with subsequent loss of the ship due to structural
failure.
Examination of Rusticle Biomass on
the RMS Titanic
The examination of rusticle growth rates on
the RMS Titanic has only been possible through annual or biennial
expeditions to the wreck site. Through the use of video and
high-resolution imagery, these growth rates and patterns of
the rusticle's can be closely analyzed. In 1996, the first
examination of rusticle's from the RMS Titanic occurred. This
examination has shown clear evidence of rusticle growth on
the outside of the bow section of the ship, however, the outside
of the stern, and the interior of the wreck, cannot be clearly
quantified because of the lack of adequate examination. One
aspect of this examination was to estimate the percentile
coverage of the various parts of the bow section together,
and the estimated thickness of the rusticle's at these various
sites (Table Two). From the 1998 Expedition, comparative assessments
through video imagery showed clear evidence that the rusticle's
continue to grow and there is evidence that the biomass is
approximately 30% greater than the mass observed in 1996.
Video surveys of the bow section of the RMS Titanic, in August
1996 and 1998, allowed a quantitative estimate of the total
volume of rusticle's This estimate is based on the area of
the steel covered by rusticle's at various points on the ship.
Calculations reveal that the bow section of the ship had a
total mass of 650 tons of rusticle's in 1996 and increasing
to 881 tons in 1998 (Table Three). The iron content in the
rusticle's had presumably been extracted from the ship’s
steel structures and was now accumulated within the rusticle's
The iron content has risen from 178 tons of iron in 1996 to
242 tons in 1998. While there is a significant amount of iron
present within this mass of rusticle's, there remains a concern
as to the rate at which iron is being released from the rusticle's
into the oceanic environment. Iron concentrations vary in
rusticle's along with their size, weight and density of the
ducts on the surface of the rusticle's (Table Three). These
estimates are based on examination of rusticle specimens recovered
from both the 1996 and 1998 Titanic Expeditions.
Focused Accumulation Sites for the Iron within the
Rusticle's
One concern arising from the examination of the RMS Titanic,
was the manner in which the iron is accumulating in the rusticle's
It is known that the rusticle's have a very large surface
area and a highly porous concretious structure, however, little
was known of the sites where the iron accumulates. Accumulation
occurs as various forms of ferric oxide and hydroxide, dominated
by goethites. To examine the sites of iron accumulation in
the Rusticle's, a Veterinary Grade Radiograph machine operated
at 100kV, 1/20 sec, using Kodak high-speed film was used.
Five rusticle's, collected from the 1996 and 1998 Expeditions,
were investigated using radiographic examination (Plate One).
It was found that the iron within the rusticle structure was
not evenly distributed throughout, but was concentrated into
two major regions. The first region where iron was dispersed
resembles “cloud-like” structures. The second
region had very dense channeling of the iron into localized
regions that spread web-like throughout the rusticle. The
first impression was that the region-channeled iron resembles
a primitive blood system.
The radiographic images confirmed the complex nature of the
rusticle structures and the fact that the rusticle's had entrapped
artifacts such as coal fragments and glass shards that rained
over the ship immediately after the collision with the ocean
floor. Microbiological examinations found that the microbial
consortia within the rusticle were not dispersed but remained
concentrated within localized regions of the rusticle. No
correlation could be established between the sites of iron
concentration and the various bacterial consortia present
in the rusticle.
It has been determined, based on extraction results, that
a cycle has been established in which iron is being biologically
extracted from the steel of the ship into the rusticle structures.
The iron is then exported into the oceanic environment as
“red dust” and “yellow colloids”.
The rate of extraction is increasing beyond the predicted
1996 rate of 0.1 tons of iron being mined by the rusticle's
per day.
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