SUSTAINABLE
PRODUCTION FOR
AQUACULTURE
The problems
Rapid growing food producing sector
(8,9%)…capture fisheries (1.2%) & farmed-meat production (2.8%) FAO, 2004)
Ocean fisheries stock are fully or over-fished
Intensive development…. environmental impacts
The problems
Intensive aquaculture = ground waste of
community with 50 inhibitans (Helfman et al.
1997)
Live fish biomass = 5x more waste than live human biomass
The Problems
Small fraction of nutrients added to aquaculture ponds is absorbed by target species
Large fraction of nutrients added to aquaculture ponds is exported
Nutrient enrichment of receiving waters could have potential deleterious impact on ecological health
Sediment
NH4
15000
10400 Effluent
Feed 2600
7000
5400
(g/ha/d)
n
NH 3 NH 4 +
Ammonia Un -ionized
Ammonium Ionized
Low pH
Low Temp High pH
High Temp
Nitrogen Cycle
Removal N in aquaculture
1. Out side the culture unit
Earthen treatment ponds
Biofiltration
2. Within culture unit
Bioflocs technology
Periphyton treatment technique
Removal ammnonia-nitrogen within culture
1. Photoautotrophic removal by algae
2. Autotrophic bacterial conversion of ammonia- nitrogen to nitrate-nitrogen
3. Heterotrophic bacterial conversion of ammonia-nitrogen directly to microbial biomass
Accelerating the biological removal of organic and inorganic waste
Developing and controling:
1. Heterotropic microbial floc, bio-floc technology
2. Attached organism (periphyton) periphyton-based aquaculture
Bio-flocs technology (BFT)
Bio-flocs technology (BFT)
Bio-flocs technology (BFT) is the utilization of microbial processes within animal rearing units to treat water and provide food resources
(Crab et al., 2012)
BFT component
1. Solids : inorganic and organic particulate solids
2. Bacteria and Fungi : heterotropic and chemoautrotrophic
3. Algae: Photoautrophic and heterotrophic 4. Microorganisms: protozoa (amoebas,
ciliates), nematodes , zooplankton 5. Special component
BFT component – Bacterial detrital aggregate
• Combined cocci, rod and filamentous bacteria
• floc particle size : 10 -1000 up m
BFT component – Algae
• Pelagic and benthic diatom
• Green algae
• Blue-green algae
BFT component – Microorganism
(Douglas H. Ernst, 2010)
BFT component – special component
• Extracellular polymeric substances (EPS)
• Storage polymers (poly-β-hydroxybutyrate/PHB, glycogen and polyphosphate)
EPS production: CDC – PHIL – IOWA (USA) http://phil.cdc.gov/phil/home.asp
Storage polymers
• PHB/glycogen/polyphosphate: accumulate as carbon/energy or reducing-power storage material in microbial cells
Verstraete et al., 2010
Amino acid and vitamin
profile of
biofloc
BFT pathways
Carbon-Nitrogen Management
Ammonia removal pathways:
1. Photoautrophic : Ammonia algae biomass
2. Chemoautrotrophic : Ammonia Nitrite Nitrate
3. HETEROTROPIC : Ammonia Bacterial biomass Photoautotrophic, chemoautotrophic, heterotrophic composition of biofloc is determined by:
• Light intensity
• Feed application intensity
• C/N ratio of feed inputs
• Rate of solids removal
C:N Ratio (CNR)
Effect of CNR on nitrogen utilization by heterotropic bacteria:
• CNR<10 : Organic nitrogen used, ammonia released
• CNR >10 : Organic and inorganic N sources used
• CNR >12-15 : Net consumption of ammonia
How to do it????
1. Enough aeration to maintain oxygen above 4-5 mg/l.
2. Lined pond: Plastics, concrete, soil concrete, laterite.
3. Placement of aerators in a way that all pond volume will be mixed. NO ACCUMULATION OF SLUDGE!!
How to do it
Stagnant area 1,2 ha (Water velocity < 1 cm/sec) equipped with long arm paddle wheel aerators (2 hp each)
How to do it ???
4. Feed with low protein % (20%) or add enough carbon (molasses, starch, cassawaetc.)
5. If inorganic nitrogen accumulates, add
carbohydrates at a rate of 20 kg per kg N you want to remove.
6. Maintain alkalinity > 50-100 mg.
Advantages
Upgrade strach to protein
No need water treatment system
Applicable to extensive to intensive system
Controlling effect on pathogenic bacteria (poly- β-hydroxybutyrate)
How to do it???
7. Minimize water exchange.
8. If sludge accumulates, drain sludge out or dry/clean between seasons.
9. It was demonstrated that the same principles can be used in stagnant ponds!!!
10. Every farm is some what different. Learn from yours and others experience.
Bio-flocs practises in
tilapia
(Y. Avnimelech,Tilapia, an ideal fish for Biofloc Technology
• Grow well in dense cultures
• Resistant
• FILTER FEEDER
Tilapia biomass
• Fish Biomass Normally, 20-30 kg/m2 10 times
higher than shrimp BFT ponds!
IMPLICATIONS
• High Biomass 20-30 kg/m3
• High feeding (ca 500 g feed/m3 per day!)
• Very high microbial activity
• High floc volume (20-50 ml/l).
• Very high natural feed storage.
• High levels of feed residues
• Need to drain out daily (or twice daily) excessive sludge.
• Pond constructed to facilitate sludge draining and perfect mixing.
• High and effective aeration: 10-20 hp/1000 m2 pond
Protein recycling in BFT
• Normally, fish or shrimp recover just ~25% of feed protein.
• In bacterial controlled ponds, they eat the protein twice; Once in the feed and then they consume microbial protein. The protein recovery reaches almost 50%.
Floc contribution
Exp 1 (51 days) Control BFT
Feed CNR 11.1 16.6
Daily gain 1.59 2.0
FCR 2.62 2.17
PCR 4.38 2.42
Exp 2 (30 days) Control BFT
Feed CNR 11.1 16.6
Daily gain 1.63 2.22
FCR 2.62 2.02
PCR 4.38 2.18
Data on feed protein utilization
• Conventional fish, shrimp ponds 20-25%
• BFT Tilapia ponds (Avnimelech) 45%
• BFT Shrimp ponds (McIntosh) 45%
• Closed shrimp tanks (Velasco) 63%
• BFT shrimp ponds, 15N study 18-29% of total N consumption (Michele Burford et al.)
• *Tilapia, 15N Study, flocs supplied about 50% of fish protein requirement. (Avnimelech).
Conclusion
Biofloc technology is especially adapted to raise tilapia production up to 20-30 kg/m2.
This can be done using not too expensive system.
BFT enables feed recycling, high feed quality and reduced expenses.
BFT reduces disease.
The system is friendly and forgiving.
More research is needed
