Environmental Engineering Reference
In-Depth Information
mechanical damage, blockages and corrosion to equipment, and submerged pipes
and pumps as well as causing their failure [5, 6].
The quagga mussel (
Dreissena rostriformis bugensis
), and the zebra mussel
(
Dreissena polymorpha
), cause damage by clogging screens and pipes and fouling
hard substrates. It is reported that such damage cost the municipal water districts
in Nevada, Arizona and California millions of dollars per year for additional
maintenance and lead to several lake closures [7, 8].
Surfaces such as polyurethane (PU), polyester, silicon rubber (SR), syntactic foam (SF),
glass glass ibre reinforced polymers (GFRP) and carbon ibre reinforced polymers
(CFRP) become rough because of the action of wind, ocean currents and micro/macro
fouling. Macrofouling can affect the tensile strength, elongation, hardness, roughness
and contact angle of polymers, rubbers and composites after one year of immersion
in the ocean. Tensile strength had decreased by 20−30%, hardness by 10−20% and
surface energy by 30−50% (
Table 4.1
) [9].
4.3 Impact of Environmental Factors on Macrofouling
Dreissena mussels are dangerous macrofoulers because they can settle on and
attach to hard surfaces even in the absence of a microbial bioilm. Generally such
a bioilm is needed by many other fouling organisms. Macrofouling by the golden
mussel (
Limnoperna fortunei
)
decreases in regions of high low and turbulence.
Light has direct and indirect effect on macrofouling.
D. polymorpha
exhibits strong
negative phototaxis, namely, a preference for shaded rather than sunlit surfaces.
Light indirectly inluences fouling by affecting the water temperature and the amount
of phytoplankton growth in the water. The three-dimensional orientation of surface
also affects macrofouling, although it is not clearly understood [10].
Chemical parameters such as pH, salinity, concentrations of calcium, magnesium,
chlorophyll a, nitrogenous compounds, dissolved oxygen, hardness, organic and
other macromolecules, colloidal matter and pollution can all affect macrofouling.
The solubility and bioavailability of biocides (e.g., cuprous oxide) is inluenced by pH
and hardness which in turn affects macrofouling [11]. Rosin is used in the production
of antifouling coatings and its solubility increases with increasing pH.
