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A Review of Marine Growth Protection System (MGPS) Options for the Royal Australian Navy.

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Abstract

Biofouling of ship’s internal seawater systems can have serious implications for performance, continuing operational capability and crew habitability. Internal seawater piping systems and intakes are prone to heavy fouling pressure due to the relative inaccessibility and complexity of these systems. Fouling control in internal systems is optimally maintained by the installation and operation of Marine Growth Protection Systems (MGPS), which prevent fouling by operating within the internal seawater system to deliver antifouling agents. This review of available and emerging MGPS and other fouling control systems provides an overview of the current RAN MGPS experience, other available treatment options and recommendations for ongoing investigation into potential future protocols for fouling management in the RAN fleet.

Executive Summary

Internal ship seawater systems, as used for supply to fire suppression and cooling/heat exchangers, are often prone to heavy fouling pressure. Fouling of internal systems can have serious implications for a vessel’s short-term operational capability, habitability and survivability and may also have long term impacts on the integrity of internal piping.; The most commonly employed Marine Growth Protection Systems (MGPS) for shipboard internal seawater systems are anodic copper dosing or chlorine based systems; however, other options for fouling prevention and treatment exist, both within ‘traditional’ biocide chemistry as well as novel non-chemical antifouling strategies. The current RAN fleet employ a variety of strategies for the prevention of internal seawater system fouling, including: sacrificial anodic copper dosing (Cathelco® system), sodium hypochlorite dosing, freshwater flushing and Cu/Ni piping (which has inherent growth protection properties).; Despite the availability of existing technologies for fouling control in internal seawater systems, MGPS have substantial operational limitations and have failed to deliver reliable biofouling control. Peer reviewed scientific literature on shipborne MGPS for internal piping systems is not common, with most documented experiences and trial results derived from power station cooling systems, ship ballast water treatments and industrial water treatment and desalination plants.; It appears that a single MGPS strategy is unlikely to be able to control all fouling pressures experienced by RAN vessels, and a combination of treatments may be necessary. Currently, anodic copper dosing or electrochlorination (or a combination thereof) appears to be the only MGPS technologies mature enough to function effectively in the RAN operating profile and environment. This review examines additional MGPS options available to the RAN and provides recommendations for future trials of potentially suitable emerging technologies.; It is recommended that trials are performed using a field test rig designed to closely simulate conditions encountered in ship board sea chests and piping systems to provide realistic data regarding potential performance in on-board conditions. The review has identified the following options as being suitable for further investigation:; • The testing of carbon dioxide as a pre-treatment to halogen dosing. This technique may be of use as a remediation strategy for control of existing fouling populations (particularly macrofouling species such as bivalves which detect halogen biocides in the water).; • The use of multiple point ozone injection into seawater systems as well as the sea chest as a preventative strategy to protect against initial settlement at seawater intake points as well as throughout internal piping systems; • Trialling of different dosing regimes for biocides in an attempt to reduce overall biocide usage (and therefore discharge). Targeting biocide delivery in response to fouling levels and organism condition may reduce overall required levels of biocide dosing in comparison to continual dosing regimes. Variation of dosing schedules may also increase efficacy of the dosing regime as organisms are less likely to build resistance to a randomised dosing protocol; • The co-dosing of biocides (for example copper and chlorine) may increase the efficacy of the dosing regime; • Thermal treatment is highly desirable for development as a MGPS as both an environmentally benign and potentially sustainable treatment option (particularly if waste heat removed during cooling processes is able to be recirculated for treatment).

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