Transcript Moreton Bay Prawn Farm

“Biofiltration of Shrimp Pond Effluent
by Oysters in a Raceway System”
Adrian B. Jones* and Nigel P. Preston
C.S.I.R.O. Division of Fisheries
Moreton Bay Prawn Farm
Research funded by the
Fisheries Research and Development Corporation
Saccostrea
commercialis
Oyster’s Filter Feeding

Oysters filter bacteria and phytoplankton and convert them to meat.

Oysters filter inorganic material and pellet smaller particles into larger
pseudofacaes which can settle out of suspension.
- Faeces (organic) and
Ammonia
- Psuedofaeces (inorganic)
Mantle
Heart
Anus
Gills
Adductor
Muscle
Intestine
Stomach
Style Sac
Labial Palps Hinge
(mouth)
- Bacteria
- Phytoplankton
- Inorganic particles
- Detritus
Study Area
Moreton
Island
Redcliffe
Brisbane
Moreton
Bay
Brisbane
City
North
Moreton Bay
Prawn Farm
Stradbroke
Island
Moreton Bay Prawn Farm
Need for Research

Need to recapture some of the nutrients from the high cost feed pellets which are not
converted into prawn biomass.

Prawn farm effluent contains elevated concentrations of bacteria, phytoplankton,
nutrients and suspended solids, which can potentially adversely affect the water
quality in the receiving waters.

Sewage treatment techniques are often ineffective due to the low specific gravity of
most of the effluent particles, and the high volume and salt content. They are also
prohibitively expensive.

To develop a system of long term sustainable aquaculture.
Objectives

Quantitative determination of the changes in the chemical and
biological composition of prawn farm effluent water after
biofiltration by different sizes of the Sydney Rock Oyster
(Saccostrea commercialis).






Phytoplankton
Bacteria
Nutrients (nitrogen & phosphorus)
Total Suspended Solids
Organic / Inorganic Ratio
Determine the most efficient system to facilitate maximum
filtration by the oysters, by adjusting flow rates and recirculation.
Methods
Effluent from shrimp pond
Shrimp pond waste
water pumped at
constant flow
rate
6 raceways stocked with
oysters (3 controls and 3 treatment
replicates)
Biofiltered water
recirculated back
through the oysters
for further filtering
Biofiltered water
released into the
environment
Moreton Bay
Collect 3 replicate samples
from each raceway (before and
after biofiltration) for
analysis of Chlorophyll a,
bacterial numbers, total
suspended solids, & nutrients
Raceways
Raceway Setup
Effluent Water Flow
Prawn
Ponds
Effluent Channel
Moreton Bay
Raceways
Recirculating Tank
Reduction in bacterial numbers after oyster biofiltration
Continual Flow
Recirculating
6
14
106 )
ml(xx 10
perml
Bacteriaper
ofBacteria
No. of
No.
1066)
ml(xx 10
perml
Bacteriaper
ofBacteria
No. of
No.
108%
12
10
8
6
37%
4
2
0
Control
Oysters
Treatment
Inflow
Outflow
30
25
20
15
54%
33%
10
19%
5
12%
0
09:00
11:00
13:00
Sampling Time
Inflow
Outflow
15:00
Reduction in chlorophyll a concentration after oyster
biofiltration
40
35
30
25
20
15
10
5
0
Recirculating
97%
39%
-1)
Chl
Chlaa concentration
concentration (µg.l
( g/L)
-1)
Chl aa concentration
concentration(µg.l
(  g/L)
Chl
Continual Flow
30
25
115%
20
15
54%
10
20%
20%
5
4%
0
Control
Oysters
Treatment
Inflow
Outflow
09:00
11:00
13:00
Sampling Time
Inflow
Outflow
15:00
Reduction in Total Suspended Solids after
oyster biofiltration
Recirculating
0.16
0.14
92%
76%
0.12
0.1
0.08
0.06
0.04
0.02
0
Control
Oysters
Treatment
Inflow
Outflow
Total Suspended Solids (g. l-1)
Total Suspended Solids (g. l-1)
Continual Flow
0.18
0.16
0.14
0.12
0.1
0.08
0.06
0.04
0.02
0
118%
54%
63%
32%
19%
09:00
11:00
13:00
Sampling Time
Inflow
Outflow
15:00
Reduction in Total Nutrient Concentrations after oyster
biofiltration
2
1.8
1.6
1.4
1.2
1
0.8
0.6
0.4
0.2
0
Phosphorus
89%
66%
Control
Oysters
Treatment
Inflow
Outflow
Total Phosphorus (mg. l-1)
Total Nitrogen (mg. l-1)
Nitrogen
0.2
0.18
0.16
0.14
0.12
0.1
0.08
0.06
0.04
0.02
0
85%
56%
54%
Control
Oysters
Treatment
Inflow
Outflow
Summary of Results
Water quality
Parameter
TSS
Bacteria
Chlorophyll a
Nitrogen
Phosphorus
% Reduced after once
through the oysters
35%
65%
61%
39%
44%
% Reduced after three
times through oysters
84%
88%
80%
nd
nd
Conclusions

Oysters can remove from suspension large quantities of phytoplankton, bacteria,
nutrients and total suspended solids.

By employing recirculating within the raceway system, the effects of the oysters
are enhanced significantly.

The use of oysters as natural filters of aquaculture effluent has the potential to
provide:






improved water quality of pond effluent and hence reduced environmental impact.
reduced pond water exchange through recirculation of biotreated water back into the
ponds.
recapturing of nutrients.
increased profits.
increased productivity.
more productive method of growing and fattening oysters.
Continued Research

Filtration efficiency of oysters at different densities.

Test effects of flow rate, versus recirculation of water through the oysters.

Test the efficiency of different sized oysters and determine their growth rate
versus those in control oceanic waters.

Test the ability of macroalgae (Gracilaria edulis) to remove dissolved nitrogen
and phosphorus.

Undertake commercial scale system at Rocky Point Prawn Farm.
Study Area
Moreton
Island
Redcliffe
Brisbane
Moreton
Bay
Brisbane
City
North
Moreton Bay
Prawn Farm
Stradbroke
Island
Pond Design Layout
Oyster Rafts
Settling
Area
Macroalgal
Area
Outflow
Inflow
Baffle to slow
water
Baffles
to force water up into oyster trays
Integrated Aquaculture Farm
Harvested
Harvested
- Bacteria
- Phytoplankton
- Inorganic particles
- Detritus
Harvested
- Faeces (organic)
and Ammonia
- Psuedofaeces
(inorganic)
Oyster
Macroalgae
- Faeces (organic)
and Ammonia
- Psuedofaeces
(inorganic)
Shrimp
Nutrient rich
food source high in amino
acids
Harvested
Harvested
Clam
Abalone