Environmental Engineering Reference
In-Depth Information
There is a positive relationship between macrofouling and nutrient concentration.
D. polymorpha, D.
rostriformis
bugensis
and
L. fortunei
all require dissolved
calcium to build a calcite shell. Dissolved oxygen reduces the antifouling properties
of rosin-based, copper biocide antifouling coatings. The reasons for this behaviour
include oxidation of dissolved copper(I) and the partial re-precipitation of copper(II)
carbonate, copper(II)chloride or copper(II)hydroxide. Organic pollution affects
nutrient and dissolved oxygen concentrations. Solubility of oxygen decreases with
increase in dissolved salts. Organic and other macromolecule loadings inluence the
development of conditioning ilms. Particulate and colloidal matter adsorb biocides
and can alter the reaction and diffusion rates that determine biocide release rates
from coatings [12].
In the aquatic system, microalgae secrete extracellular polymeric substances,
predominantly (from 40 to as high as 90%) containing a biopolymeric material known
as exopolysaccharide (EPS). This extracellular polymeric substance also contains
lipids, nucleic acids, and proteins. EPS plays an important role in the attachment
and adhesion of cells to surfaces. Organisms that are attached to a surface increase
their chances of survival when compared to ones that are in the unattached state. EPS
forms a highly hydrated matrix and provides a layer of protection to the cells against
toxic compounds or against predation or digestion by other organisms. EPS may also
prevent cellular dehydration or damage caused because of ice crystal formation. EPS
forms the architectural network of bioilms and aggregates, protecting the cells and
assisting their intercellular communications and interactions with each other [13].
Season and monsoon conditions play an important role in the attachment of
macrofoulants to surfaces. For example, studies carried out in the coastal water of
the Bay of Bengal indicated that attachment of macrofoulants such as barnacles on
low-density polyethylene (LDPE), high-density polyethylene (HDPE), polypropylene
(PP) and polycarbonate (PC) were seen more during May−July 2009 and hydroids
were seen more during the monsoon period (November 2009) than any other months.
Apart from barnacles and hydroids, other foulants observed included polychaetes,
bryozoans and tube worms. They were not seen in all the samples and their relative
amount varied from month to month [9, 14, 15].
Balanus amphitrite
, on PC, LDPE,
HDPE and PP were dominant after the monsoon.
Season also plays an important role in total fouling load, total suspended solids,
barnacle and polychaete attachment. Barnacle attachment on SR, PU, polyethylene
terephthalate (PET), SF, GFRP and CFRP is highest in September and lowest
in January−March (
Table 4.2
). Generally, July is the culmination of the south-
west monsoon and November is the start of the north-east monsoon. The ocean
temperatures may be lowest during the January−March season which may be one
of the reasons for the low number of barnacles observed in the study. PU has the
