Solids Management in BioflocBased Aquaculture Systems
Andrew J. Ray and Jeffrey M. Lotz Gulf Coast Research Laboratory The University of Southern Mississippi, Ocean Springs, MS 39564 USA
[email protected] Characterizing Suspended Solids • • • • • • •
TSS (Total Suspended Solids) VSS (Volatile Suspended Solids) Turbidity Settlable Solids Floc Volume Index Particle Size Microbial Composition – Microscopy – Phenotypic Techniques – Molecular Techniques
• Microbial Function – Oxygen Production/Demand – Nutrient Cycling •
De Schryver et al. 2008
Why Control Biofloc Concentration? • Issues with excessive particles – Gill Clogging – Increased Biochemical Oxygen Demand (BOD) – Promote the Occurrence of Harmful Microorganisms • ↓ Light Penetration • Cyanobacteria, zooplankton blooms?, dinoflagellates?
– Potential for Sludge Deposition
• Control over culture systems – Microbiota • Remove unwanted organisms • Promote a younger/healthier community
– System Stability – Nutrient Removal/Cycling
Particulate Control – Bead Filters/Sand Filters • Inadequate for intensive biofloc systems (ex. Mishra et al. 2008) – Particle load/water use – Size? Cost?
– Foam Fractionators • Benefits – Not prone to fouling – Range of particle sizes – Dissolved components
• Drawback
http://www.emperoraquatics.com/images/ff_diagram.jpg
– Can be inconsistent in what they remove and how much » Dependent on: bubble diameter, solids concentration, air-towater ratio, surface chemistry of solids, and the surfactant concentration in water » Cost?
Sedimentation Supply Line From Raceway Valve to Control Flow Rate
• Gravity – Ponds/tanks with drains – External ponds – External chambers • Benefits Simple Inexpensive Scale up or down easily Anaerobic zone separate from culture unit – Not prone to fouling – Denitrification • Drawbacks – Small particles? – Dissolved components? – Surface mats??? – – – –
Central Baffle to Slow Water Velocity
Return Line to Raceway
Settled Solids
Valve to Drain Settled Material
The Effects of Solids Management on Water Quality Final NO3 and PO4 Concentrations
Turbidity and TSS 100
Fishmeal Fishmeal Settled Plant Plant Settled
70
140 120
60 50 40 30
100
20
60 40 20
10
0
0 1200
140 120
800
100
mg PO4 L-1
1000
TSS (mg L-1)
Alkalinity
80
Alkalinity (as mg CaCO3 L-1)
80
mg NO3-N L-1
90
Turbidity (NTU)
160
600 400
160
Fishmeal
140
Fishmeal Settled Plant
120
Plant Settled
100 80 60 40 20 0
80
1
2
3
4
5
6
7
8
9
10
11
12
Week
60 40
200
20 0
0 1
2
3
4
5
6
7
8
9
10
11
12
Fishmeal
Week
• Settling Chambers in Shrimp BFT – 6200 L circular, outdoor tanks – 2 experiments one year apart • Exp. A = 16 tanks • Exp. B = 32 tanks
– ½ tanks with settling chambers, ½ without
Fishmeal Settled
Plant
Plant Settled
• BFT Settling Chambers – Exp. A – – – – –
59% ↓ TSS 60% ↓ NO3-N 61% ↓ Orthophosphate 33% ↑ Alkalinity Denitrification???
Solids Management and Microbial Communities PAR Extinction and Oxygen Production 800
25
Fishmeal Settled
20
Plant
15 Plant Settled
10 5
600 500 400
Fatty Acid Bacterial Indicators
300
Fishmeal
200
Fishmeal Settled Plant
100
0 1
2
3
4
5
6
7
8
9
10
11
12
Phaeopigments (µg L-1)
700
2.0
1.5
1.0
0.5
0.0
Plant Settled
0
Week
2.5
1600
Branched and Odd Chain Fatty Acids (µg L-1)
30
Fishmeal
Mean Photosynthetic Oxygen Production (mg L-1 h-1)
Chlorophyll and Phaeopigments
700
35
Chlorophyll-a (µg L-1)
PAR Extinction Coefficient
40
600 500 400
1200 1000 800 600 400 200 0 1
300
Fishmeal Settled
Plant
Plant Settled
200
0 1
2
3
4
5
6
7
8
9
10
11
12
Week
• BFT Settling Chambers – Exp. A – – – – –
2
3
4
5
6
7
Week
100
Fishmeal
Fishmeal Fishmeal Settled Plant Plant Settled
1400
47% ↓photosynthetically active radiation extinction coefficient 200% ↑ photosynthetic oxygen production 65% ↓ final chlorophyll-a 72% ↓ final phaeopigments 80% ↓ fatty acid bacterial indicators
8
9
10
11
12
Solids Management and Microbial Communities • Microbes – Exp. B – No detectable difference with respect to chlorophyte, diatom, or dinoflagellate abundance – 60% ↓ in final nematode abundance – 19% ↓ in final rotifer abundance – 23% (visual), 17% (epifluorescence) ↓ final cyanobacteria abundance – 60% ↓ final fatty acid bacterial indicators
Solids Management and Shrimp Production Biomass and FCR 4.5
70
4.0
60
3.5 kg shrimp m-3
Survival (percent)
Survival and Growth 80
50 40 30 20
2.5 2.0 1.5 1.0
10
0.5
0
Fishmeal
Fishmeal Settled
Plant
0.0
Plant Settled
12
2.5 Fishmeal Fishmeal Settled Plant Plant Settled
8
2.0
FCR
10
Weight (g)
3.0
6
1.5 1.0
4
0.5
2 0 0
1
2
3
4
5
6
7
8
9
10
11
12
0.0
Week
Fishmeal
Fishmeal Settled
Plant
Plant Settled
• Shrimp Production – Exp. A – No significant difference in survival – 28% Increase in growth rate
– 41% Increase in final biomass – 26% Decrease in FCR
Needed Research • Refining the optimal concentration of biofloc particles = This Afternoon! • Remediation of Removed Material – Dissolved Nutrients • Sequence batch reactors • Plants
– Solids • Nutritional supplement = This Afternoon!
Thank You
• Shrimp aquaculture research at The GCRL is supported by The USDA US Marine Shrimp Farming Program. • The two experiments described here were conducted at the Waddell Mariculture Center, Bluffton, South Carolina, USA; thank you to the staff of that facility.