1. 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 2 CSIRO Marine Research, Cleveland, QLD, Australia Marine Botany

2. Shrimp Farm Plume Plume Suspended SolidsSuspended Solids PhytoplanktonPhytoplankton BacteriaBacteria NutrientsNutrients

3. Introduction Marine organisms (plants and animals) can act as biological filtersMarine 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)oysters can filter particulates (eg. phytoplankton, bacteria, small inorganic clay particles) macroalgae can assimilate dissolved organic and inorganic nutrientsmacroalgae can assimilate dissolved organic and inorganic nutrients

4. Aims Test a three stage integrated system for the treatment of aquaculture effluent using: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 phytoplanktonEstimate potential removal rates of bacteria, suspended solids, nutrients and phytoplankton

5. Experimental Design Laboratory treatment tanks

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

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

8. Suspended Solids Sedimentation & Control (no oysters or macroalgae) OysterFiltrationMacroalgalAbsorption Sedimentation Oyster Filtration MacroalgalAbsorption

9. Settlement Rates Sedimentation & Control (no oysters or macroalgae) OysterFiltrationMacroalgalAbsorption Sedimentation Oyster Filtration MacroalgalAbsorption OystercontrolOystertreatment

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

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

12. Chlorophyll a Sedimentation & Control (no oysters or macroalgae) OysterFiltrationMacroalgalAbsorption Sedimentation Oyster Filtration MacroalgalAbsorption

13. Bacteria Sedimentation & Control (no oysters or macroalgae) OysterFiltrationMacroalgalAbsorption Sedimentation Oyster Filtration MacroalgalAbsorption

14. Ammonium Sedimentation & Control (no oysters or macroalgae) OysterFiltrationMacroalgalAbsorption Sedimentation Oyster Filtration MacroalgalAbsorption

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

16. Phosphate Sedimentation & Control (no oysters or macroalgae) OysterFiltrationMacroalgalAbsorption Sedimentation Oyster Filtration MacroalgalAbsorption

17. Total Nitrogen Sedimentation & Control (no oysters or macroalgae) OysterFiltrationMacroalgalAbsorption Sedimentation Oyster Filtration MacroalgalAbsorption

18. Total Phosphorus Sedimentation & Control (no oysters or macroalgae) OysterFiltrationMacroalgalAbsorption Sedimentation Oyster Filtration MacroalgalAbsorption

19. Water Quality Improvements

20. Pond Effluent Settled Effluent Biofiltered Effluent

21. Conclusions Combined treatment effectively reduced the concentrations of: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 healthSedimentation 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 excretionOyster filtration significantly decreased the concentrations of total N and total P, but increased the dissolved nutrients through excretion Macroalgal absorption effectively removed dissolved nutrientsMacroalgal 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 -1Total 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