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Controlling biofouling of pond aerators on marine prawn farms

Controlling biofouling of pond aerators on marine prawn farms. CRC project application 2011. David Mann AgriScience Qld, DEEDI. Aerator biofouling project. Interest across industry No ‘off-the-shelf’ practical method available no areas have proactive system (cheap labour o/s) Aims

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Controlling biofouling of pond aerators on marine prawn farms

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  1. Controlling biofouling of pond aerators on marine prawn farms CRC project application 2011 David Mann AgriScience Qld, DEEDI

  2. Aerator biofouling project • Interest across industry • No ‘off-the-shelf’ practical method available • no areas have proactive system (cheap labour o/s) Aims • Reduce production costs • Reduce the ‘pain-in-the-arse’ factor • difficulty in organising staff & resources to do the job

  3. What is the problem? Preliminary info from farms – questionnaire • Main culprits - barnacles, tubeworms and algae • Dominant foulant varies by farm & year • Fouling costs • Labour - de-fouling • Moving, scraping, pressure cleaning • Electricity use • Lower electrical efficiency (~50%) • Lower oxygenation efficiency (??) • Maintenance - more frequent/earlier replacement • Productivity losses (risk / unrealised) • Biofouling cost - ~$1k per ha per crop

  4. Aerator biofouling Results from questionnaire • 8 to10x 2hp (1.5kW) aerators /ha peak • Paddlewheels make up 50 to 60% of aeration fleet • Paddlewheels – greatest fouling impact • Typically aerators on 24h a day • At peak around 6,000 aerators across industry • Type of fouling varies by farm and year to year

  5. Aerator biofouling control • Biofouling affects all of the paddlewheel above and below the waterline • Zones • Blades (algae, barnacles) • below water-line surfaces (all) • Surfaces above water line (algae>barnacles) Algae Algae Algae, barnacles Algae Barnacles, tubeworms, algae

  6. Project Outline 1. Status of biofouling • Data for determining most effective strategy • Aerator fouling characteristics • Cost to industry • Practical measurements • efficiency of aerators affected by varying levels of fouling • Oxygen transfer rate (SOTR) • Aerator electrical efficiency (SAE)

  7. Project Outline 2. Options for pond aerators • Antifouling - big business / huge R&D effort • Aquaculture – shellfish and seacage finfish benefited • Coatings - biocides, various surface properties (‘fouling release’), anti-settlement chemicals • Ultrasound • Sacrificial / replaceable covers • Equipment design and materials • Light reducing cover

  8. Project Outline 3. On-farm tests • Short list of control options (farm assessed) • Practical comparison of different options • Info on • Costs (direct / indirect) • Practical implementation • Durability/effective period

  9. Project Outline 4. Information supply • Make sure all information gets to farms who want it in a useful form • Practical and economic data • make informed strategic choice

  10. Project status • Seafood CRC submission • Negotiating through project development process • Hoped that work will start ASAP in the coming season

  11. Biofouling control selection criteria • Commercial readiness – ie not developing new system • No APVMA issues – not restricted • Cost effective – cost of implementation significantly less than current de-fouling approach

  12. 21 weeks Biofouling control selection • inert fouling release products / attachment inhibitory surfaces • range of waxy and silicon based compounds

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