The effectiveness of rotating brush devices for management of vessel hull fouling

Abstract

The present study tested two diver-operated rotating brush systems, coupled with suction and collection capabilities, to determine their efficacy in the management of vessel biofouling. Both rotating brush systems proved effective (>80%) in removing low-to-moderate levels of fouling from flat and curved experimental surfaces (Perspex plates). However, performance was generally poorer at removing more advanced levels of fouling. In particular, mature calcareous organisms were relatively resistant to the rotating brushes, with a high proportion (up to 50%) remaining on plates following treatment. On average, >95% of defouled material was collected and retained by both systems. The amount of lost material generally increased when treating curved plates with increasing biomass, whereas the material lost from flat plates was typically less and remained relatively constant throughout the trials. The majority (>80%) of fouling not captured by the systems was crushed by the brushes (ie non-viable). However, a diverse range of viable organisms (eg barnacles and hydroids) was lost to the environment during the defouling trials. When defouling a vessel, unintentional detachment of fouling organisms is likely to be high through physical disturbance by divers operating the devices and by associated equipment (eg hoses). Furthermore, residual biosecurity risks are also likely to remain due to diver error, persistent fouling remaining on treated surfaces and the inaccessibility of niche areas to the brush systems. To address these limitations, further research into alternative treatment methods is required.

Keywords:

• in-water cleaning
• biofouling tools
• marine invasion
• biosecurity

Acknowledgements

The authors thank Tony Thew (Diver Services New Zealand Ltd), Dougal Fergus and Matt Fabish (New Zealand Diving & Salvage), and Captain Charles Smith (Centreport Wellington). They also thank Chris Denny and Tim Dodgshun (Cawthron Institute) for their assistance in the field, and Peter Stratford and Liz Jones (MAF Biosecurity New Zealand) for their input throughout the project. This project was funded by MAF Biosecurity New Zealand (Project ZBS2005-21) and the New Zealand Foundation for Research Science and Technology (OBI contract C01X0502; Effective Management of Marine Biodiversity and Biosecurity).