Controlling biofouling of pond aerators on marine prawn farms

Abstract

PROJECT OBJECTIVES:
1. Review biofouling control options and select those with greatest potential for application on prawn farms.
2. Assess the impact of aerator biofouling on prawn farms.
3. Transfer methods for implementing aerator biofouling controls to the prawn farming industry.
4. Evaluate selected biofouling control options under commercial conditions.
OUTCOMES ACHIEVED
The overarching output from the research conducted under this project is an improved understanding and quantification of the problem of biofouling in the use
of aerators in marine prawn ponds. Farms are under pressure to become increasingly efficient production systems and the information arising from this project will substantially contribute to the farm knowledge base drawn on to optimise strategies that reduce aerator fleet management costs. The benefit and practicality of the most cost effective biofouling control method investigated by the project, ‘paddlewheel off duty days’ is supported by its practise on at least three farms.
LIST OF OUTPUTS PRODUCED
Project outputs of practical significance to prawn farms that will assist those managing aeration improve efficiency and production system sustainability include:
• Biofouling does not compromise the oxygen transfer capacity of the commonly used aerators which is of critical concern towards the end of the crop. There is a trend for improved oxygen transfer rate with increasing biofouling for paddlewheels but at the cost of efficiency.
• Paddlewheel ‘off-duty days’ is the most cost effective approach to reducing the impact of biofouling but is limited to controlling accumulation on above waterline surfaces.
• Non-toxic surface coatings can be an effective biofouling control for constantly submersed aerator surfaces but implementation and maintenance costs are currently prohibitive to their use for this application.
• The upper limit for the cost of biofouling prevention measures is approximately $1050/ha/crop which represents the current total real cost of aerator biofouling.
These outputs were supported by a series of technical reports that were provided to the industry throughout the conduct of the project.