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Improvements in water quality of aquaculture effluent after treatment by sedimentation, oyster filtration and macroalgal

Marine Botany. Improvements in water quality of aquaculture effluent after treatment by sedimentation, oyster filtration and macroalgal absorption. Adrian Jones 1 , William Dennison 1 & Nigel Preston 2 1 Botany Department, The University of Queensland, Brisbane, QLD, Australia

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Improvements in water quality of aquaculture effluent after treatment by sedimentation, oyster filtration and macroalgal

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  1. Marine Botany Improvements in water quality of aquaculture effluent after treatment by sedimentation, oyster filtration and macroalgal absorption Adrian Jones1, William Dennison1 & Nigel Preston2 1 Botany Department, The University of Queensland, Brisbane, QLD, Australia 2 CSIRO Marine Research, Cleveland, QLD, Australia

  2. Shrimp Farm Plume • Suspended Solids • Phytoplankton • Bacteria • Nutrients Plume

  3. Introduction • Marine organisms (plants and animals) can act as biological filters • natural, already existing ecosystems (eg. mangroves, seagrasses) • introduced organisms for the purpose of improving effluent water quality • oysters can filter particulates (eg. phytoplankton, bacteria, small inorganic clay particles) • macroalgae can assimilate dissolved organic and inorganic nutrients

  4. Aims • Test a three stage integrated system for the treatment of aquaculture effluent using: • sedimentation • oyster filtration • macroalgal absorption • Estimate potential removal rates of bacteria, suspended solids, nutrients and phytoplankton

  5. Experimental Design Laboratory treatment tanks

  6. Sampling Protocol Three replicate one litre water sampes collected from the control and three replicate treatment tanks • Water column nutrients (dissolved nh4, no3, po4 and total N & P) • Total suspended solids • Chlorophyll a • pH, dissoved oxygen, temp, salinity • bacterial numbers • % organic • sedimentation rates Control Oysters 1 L samples analysed for Control Macroalgae

  7. Experimental Timeline Sedimentation (60 L) (tank not aerated) Macroalgae (5 L) (tanks aerated) Oysters (10 L) (tanks aerated) Raw Effluent Control Control (16 oyster (no algae) shells) 100g 16 Oysters Macroalgae 100g 16 Oysters Macroalgae 100g 16 Oysters Macroalgae 24 48 0 72 Time (h)

  8. Suspended Solids Sedimentation Oyster Filtration Macroalgal Absorption Sedimentation & Control (no oysters or macroalgae) Oyster Filtration Macroalgal Absorption

  9. Settlement Rates Sedimentation Oyster Filtration Macroalgal Absorption Oyster control Oyster treatment Sedimentation & Control (no oysters or macroalgae) Oyster Filtration Macroalgal Absorption

  10. Suspended Solids (% Organic) Sedimentation Oyster Filtration Macroalgal Absorption Sedimentation & Control (no oysters or macroalgae) Oyster Filtration Macroalgal Absorption

  11. Settled Particulates (% Organic) Sedimentation Oyster Filtration Macroalgal Absorption Sedimentation & Control (no oysters or macroalgae) Oyster Filtration Macroalgal Absorption

  12. Chlorophyll a Sedimentation Oyster Filtration Macroalgal Absorption Sedimentation & Control (no oysters or macroalgae) Oyster Filtration Macroalgal Absorption

  13. Bacteria Sedimentation Oyster Filtration Macroalgal Absorption Sedimentation & Control (no oysters or macroalgae) Oyster Filtration Macroalgal Absorption

  14. Ammonium Sedimentation Oyster Filtration Macroalgal Absorption Sedimentation & Control (no oysters or macroalgae) Oyster Filtration Macroalgal Absorption

  15. Nitrate / Nitrite Sedimentation Oyster Filtration Macroalgal Absorption Sedimentation & Control (no oysters or macroalgae) Oyster Filtration Macroalgal Absorption

  16. Phosphate Sedimentation Oyster Filtration Macroalgal Absorption Sedimentation & Control (no oysters or macroalgae) Oyster Filtration Macroalgal Absorption

  17. Total Nitrogen Sedimentation Oyster Filtration Macroalgal Absorption Sedimentation & Control (no oysters or macroalgae) Oyster Filtration Macroalgal Absorption

  18. Total Phosphorus Sedimentation Oyster Filtration Macroalgal Absorption Sedimentation & Control (no oysters or macroalgae) Oyster Filtration Macroalgal Absorption

  19. Water Quality Improvements

  20. Water Quality Improvements Pond Effluent Settled Effluent Biofiltered Effluent

  21. Conclusions • Combined treatment effectively reduced the concentrations of: • suspended solids (especially the small unsettleable inorganic particles) • water column nutrients (particulate and dissolved) • phytoplankton • bacteria • Sedimentation removed proportionally more inorganic than organic particles which is beneficial to the oyster’s filtration efficiency and health • Oyster filtration significantly decreased the concentrations of total N and total P, but increased the dissolved nutrients through excretion • Macroalgal absorption effectively removed dissolved nutrients • Total removal efficiency for combined treatment can be calculated as 4 kg N ha-1 d-1 and 0.6 kg P ha-1 d-1

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