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

Adrian JonesAdrian Jones11, William Dennison, William Dennison11 & Nigel Preston & Nigel Preston22

11 Botany Department, The University of Queensland, Brisbane, QLD, Australia Botany Department, The University of Queensland, Brisbane, QLD, Australia22 CSIRO Marine Research, Cleveland, QLD, Australia CSIRO Marine Research, Cleveland, QLD, Australia

Marine BotanyMarine Botany

Shrimp Farm PlumeShrimp Farm Plume

PlumePlume

• Suspended SolidsSuspended Solids• PhytoplanktonPhytoplankton• BacteriaBacteria• NutrientsNutrients

IntroductionIntroduction• Marine organisms (plants and animals) can act as biological Marine organisms (plants and animals) can act as biological

filtersfilters

– natural, already existing ecosystems (eg. mangroves, seagrasses)natural, already existing ecosystems (eg. mangroves, seagrasses)

– introduced organisms for the purpose of improving effluent water introduced organisms for the purpose of improving effluent water qualityquality

• oysters can filter particulates (eg. phytoplankton, bacteria, small oysters can filter particulates (eg. phytoplankton, bacteria, small inorganic clay particles)inorganic clay particles)

• macroalgae can assimilate dissolved organic and inorganic macroalgae can assimilate dissolved organic and inorganic nutrients nutrients

AimsAims• Test a three stage integrated system for the Test a three stage integrated system for the

treatment of aquaculture effluent using:treatment of aquaculture effluent using:

– sedimentationsedimentation– oyster filtrationoyster filtration– macroalgal absorptionmacroalgal absorption

• Estimate potential removal rates of bacteria, Estimate potential removal rates of bacteria, suspended solids, nutrients and phytoplanktonsuspended solids, nutrients and phytoplankton

Experimental DesignExperimental DesignLaboratory treatment tanksLaboratory treatment tanks

Sampling ProtocolSampling Protocol

• Water column nutrients Water column nutrients (dissolved nh4, no3, po4 (dissolved nh4, no3, po4 and total N & P)and total N & P)

• Total suspended solidsTotal suspended solids• Chlorophyll Chlorophyll aa• pH, dissoved oxygen, pH, dissoved oxygen,

temp, salinitytemp, salinity• bacterial numbersbacterial numbers• % organic% organic• sedimentation ratessedimentation rates

ControlControl

Three replicate one litre water sampes Three replicate one litre water sampes collected from the control and collected from the control and three replicate treatment tanksthree replicate treatment tanks

1 L

sa

mpl

es

ana

lyse

d fo

r1

L s

am

ple

s a

naly

sed

for

OystersOysters

ControlControl MacroalgaeMacroalgae

Experimental TimelineExperimental Timeline

0 0 72 72 48 48 24 24 Time (h)Time (h)

Oysters (10 L)Oysters (10 L)(tanks aerated)(tanks aerated)

Macroalgae (5 L)Macroalgae (5 L)(tanks aerated)(tanks aerated)

RawRawEffluentEffluent

ControlControl(no algae)(no algae)

100g100gMacroalgaeMacroalgae

100g100gMacroalgaeMacroalgae

100g100gMacroalgaeMacroalgae

16 Oysters16 Oysters

16 Oysters16 Oysters

Control Control (16 oyster(16 oyster

shells)shells)

16 Oysters16 Oysters

Sedimentation (60 L)Sedimentation (60 L)(tank not aerated)(tank not aerated)

Suspended SolidsSuspended Solids

Sedimentation & Control Sedimentation & Control (no oysters or macroalgae)(no oysters or macroalgae)

OysterOysterFiltrationFiltration

MacroalgalMacroalgalAbsorptionAbsorption

SedimentationSedimentation Oyster Oyster FiltrationFiltration

MacroalgalMacroalgalAbsorptionAbsorption

00.10.20.30.40.50.60.7

0 20 40 60 80

Time (h)

TS

S (

g L

-1)

Settlement RatesSettlement Rates

Sedimentation & Control Sedimentation & Control (no oysters or macroalgae)(no oysters or macroalgae)

OysterOysterFiltrationFiltration

MacroalgalMacroalgalAbsorptionAbsorption

SedimentationSedimentation Oyster Oyster FiltrationFiltration

MacroalgalMacroalgalAbsorptionAbsorption

OysterOystercontrolcontrol

OysterOystertreatmenttreatment

0

0.05

0.1

0.15

0 10 20 30 40 50 60 70 80

Time (h)

Set

tled

part

icle

s (g

L-1

)

Suspended Solids (% Organic)Suspended Solids (% Organic)

Sedimentation & Control Sedimentation & Control (no oysters or macroalgae)(no oysters or macroalgae)

OysterOysterFiltrationFiltration

MacroalgalMacroalgalAbsorptionAbsorption

SedimentationSedimentation Oyster Oyster FiltrationFiltration

MacroalgalMacroalgalAbsorptionAbsorption

15

20

25

30

35

40

0 20 40 60 80

Time (h)

TS

S (

% O

rga

nic

)

Settled Particulates (% Organic)Settled Particulates (% Organic)

Sedimentation & Control Sedimentation & Control (no oysters or macroalgae)(no oysters or macroalgae)

OysterOysterFiltrationFiltration

MacroalgalMacroalgalAbsorptionAbsorption

SedimentationSedimentation Oyster Oyster FiltrationFiltration

MacroalgalMacroalgalAbsorptionAbsorption

15

20

25

30

35

40

0 20 40 60 80

Time (h)

Set

tled

part

icul

ates

(% O

rgan

ic)

Chlorophyll Chlorophyll aa

Sedimentation & Control Sedimentation & Control (no oysters or macroalgae)(no oysters or macroalgae)

OysterOysterFiltrationFiltration

MacroalgalMacroalgalAbsorptionAbsorption

SedimentationSedimentation Oyster Oyster FiltrationFiltration

MacroalgalMacroalgalAbsorptionAbsorption

0

50

100

150

200

250

300

0 20 40 60 80

Time (h)

Chl

orop

hyll

a (u

g L

-1)

BacteriaBacteria

Sedimentation & Control Sedimentation & Control (no oysters or macroalgae)(no oysters or macroalgae)

OysterOysterFiltrationFiltration

MacroalgalMacroalgalAbsorptionAbsorption

SedimentationSedimentation Oyster Oyster FiltrationFiltration

MacroalgalMacroalgalAbsorptionAbsorption

0

5

10

15

20

25

0 20 40 60 80

Time (h)

Ba

cte

ria

(n

o. ×

1010

L-1

)

AmmoniumAmmonium

Sedimentation & Control Sedimentation & Control (no oysters or macroalgae)(no oysters or macroalgae)

OysterOysterFiltrationFiltration

MacroalgalMacroalgalAbsorptionAbsorption

SedimentationSedimentation Oyster Oyster FiltrationFiltration

MacroalgalMacroalgalAbsorptionAbsorption

0

10

20

30

40

50

60

0 20 40 60 80

Time (h)

Am

mo

niu

m (

µM

)

Nitrate / NitriteNitrate / Nitrite

Sedimentation & Control Sedimentation & Control (no oysters or macroalgae)(no oysters or macroalgae)

OysterOysterFiltrationFiltration

MacroalgalMacroalgalAbsorptionAbsorption

SedimentationSedimentation Oyster Oyster FiltrationFiltration

MacroalgalMacroalgalAbsorptionAbsorption

0

5

10

15

0 20 40 60 80

Time (h)

Nitr

ate

/ N

itrite

(µ

M)

PhosphatePhosphate

Sedimentation & Control Sedimentation & Control (no oysters or macroalgae)(no oysters or macroalgae)

OysterOysterFiltrationFiltration

MacroalgalMacroalgalAbsorptionAbsorption

SedimentationSedimentation Oyster Oyster FiltrationFiltration

MacroalgalMacroalgalAbsorptionAbsorption

00.5

11.5

22.5

33.5

4

0 20 40 60 80

Time (h)

Pho

spha

te (

µM

)

Total NitrogenTotal Nitrogen

Sedimentation & Control Sedimentation & Control (no oysters or macroalgae)(no oysters or macroalgae)

OysterOysterFiltrationFiltration

MacroalgalMacroalgalAbsorptionAbsorption

SedimentationSedimentation Oyster Oyster FiltrationFiltration

MacroalgalMacroalgalAbsorptionAbsorption

0

100

200

300

400

0 20 40 60 80

Time (h)

Tota

l Nitr

ogen

(µ

M)

Total PhosphorusTotal Phosphorus

Sedimentation & Control Sedimentation & Control (no oysters or macroalgae)(no oysters or macroalgae)

OysterOysterFiltrationFiltration

MacroalgalMacroalgalAbsorptionAbsorption

SedimentationSedimentation Oyster Oyster FiltrationFiltration

MacroalgalMacroalgalAbsorptionAbsorption

0

5

10

15

20

25

0 20 40 60 80

Time (h)

Tota

l Pho

spho

rus

(µM

)

Water Quality ImprovementsWater Quality ImprovementsParameter Percent of initial F Value

TSS (g L-1 ) 12 1338***

TKN (µM) 28 609***

TP (µM) 14 4629***

NH4+ (µM) 2.3 2987***

NO3- (µM) 2.2 1176***

PO43- (µM) 4.8 162***

Bacteria (no. per L) 30 107***

Chl a (µg L-1) 0.7 202***

Water Quality ImprovementsWater Quality Improvements

Pond EffluentPond Effluent Settled EffluentSettled Effluent Biofiltered EffluentBiofiltered Effluent

ConclusionsConclusions• Combined treatment effectively reduced the concentrations of:Combined treatment effectively reduced the concentrations of:

– suspended solids (especially the small unsettleable inorganic particles)suspended solids (especially the small unsettleable inorganic particles)– water column nutrients (particulate and dissolved)water column nutrients (particulate and dissolved)– phytoplanktonphytoplankton– bacteriabacteria

• Sedimentation removed proportionally more inorganic than organic particles which is Sedimentation removed proportionally more inorganic than organic particles which is beneficial to the oyster’s filtration efficiency and healthbeneficial to the oyster’s filtration efficiency and health

• Oyster filtration significantly decreased the concentrations of total N and total P, but Oyster filtration significantly decreased the concentrations of total N and total P, but increased the dissolved nutrients through excretionincreased 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 haTotal removal efficiency for combined treatment can be calculated as 4 kg N ha -1-1 d d-1-1 and 0.6 kg P haand 0.6 kg P ha-1-1 d d-1-1