Optimizing tilapia biofloc technology systems, part 1

Published on: 07/31/2018
Author/s : Ramon M. Kourie / Chief Technical Officer, SustAqua Fish Farm.

Engineering design at Chambo Fisheries, the world’s largest biofloc tank farm for tilapia Battery of eight multi-cohort sequential continuous culture BFT tanks at Chambo Fisheries.   Experience raising tilapia in biofloc technology (BFT), where aerial feeding rates are at least four to five orders of magnitude greater than in shrimp BFT systems, is limited. Areas that are particula...

print
(455)
(7)
July 31, 2018

Good Day Ray

I am finding this concept fascinating. The multicohort, leading to partial harvesting, was something that I modeled for our Dusky Kob and it makes economic sense.

I am intrigued to find out in practice how the screens, that are used to divide the tank for the different GSs, impact on the flow rate and subsequent solids removal.


Do you also have any metrics to share on the percentage oxygen saturation that these systems run at under optimal stocking and Biofloc levels?

Regards
Neil

Reply
July 31, 2018

Hi Neil

The only way to maximize throughput production relative to maximum carrying capacity is via the management of a single tank system as a multi-cohort sequential stock management system. This we call the Production: Capacity Ratio (P:C ratio). Apart from reduced CAPEX per unit fish production, the benefits filter down to energy costs for aeration, carbon dioxide stripping and horizontal water movement where power costs are basically halved when compared to a batch production system.
As far as water velocities are concerned there are two aspects that require hydraulic calculations 1) the frictional drag forces of the moving water mass which occurs at the wetted surface area (walls and floor) and 2) the frictional drag forces which occur through the screened compartments. The sum of which is called the system hydraulic gradient against which horizontal water movement needs to be balanced to achieve the design water velocity.
Screen selection, number of screens, % open area are all important affecting the final hydraulic gradient. An offset bottom bar raised three inches from the tank floor and the use of a round bar or cable to achieve complete closure of the screen are the tricks of the trade preventing solids collecting at the floor-bottom bar of the screens.

At velocities of 25-30cm/sec, the movement of heavier solids (dead material, fibrous material) the heavier material drifts on the tank floor at velocities around 15-20% slower than the water column velocities - movement is still achieved. Industrial aquaculture involves a significant amount of engineering design, hydraulics, fluid mechanics, thermodynamics, heat transfer etc. The objective being to produce fish sustainably at the lowest possible cost capitalizing on the benefits of scale economies. At 1130m above sea level we opted to run at 4.5mg/L while the added cost to take dO2 levels to 5mg/L was not great but not essential - calls for added floor diffusers. The combination of paddlewheels and floor diffusers greatly improved the driving gradient in R-ended tank systems increasing oxygen transfer efficiencies under field conditions. Our next project using sea-water BFT for O. mossambicus will, in addition, carry a nano-bubble aeration system to pick dO2 levels up into the 75-85% saturation range. Hope the above is satisfactory for now.

Best, Ray.

Reply
August 1, 2018
Thanks Ray for a detailed reply, greatly appreciated.
Reply
Pannita Seareaw Pannita Seareaw
Student
September 4, 2018

Nice forum! I will share it with all of my friends.

Reply
November 18, 2018
need some help

need small production capacity project report for fish culture using BFT
Reply
November 18, 2018
RAJENDRAKUMAR SHINGALA, SUPRINTENDENT OF FISHERIES, GUJARAT FISHERIES, GUJARAT, INDIA

Please mail me with the particulars of the request to .
Reply
Vijayakumar Patibandla Vijayakumar Patibandla
Marketing Manager
December 5, 2018

Please give complete practices of farming as some of the farmers are interested to go for Tilapia (TBT) on low salinity areas of shrimp ponds proposal of conversion.
Regards.

Reply
1
print
(455)
(7)
Would you like to discuss about this topic: Optimizing tilapia biofloc technology systems, part 1?
Engormix reserves the right to delete and/or modify comments. See more details
Post a comment
Create new discussion :
If this discussion does not cover topics of interest or raises new questions, you can create another discussion.
Consult a professional in private:
If you have a specific problem you can perform a consultation privately to a professional in our community.
Louis Landesman
Louis Landesman
Ph.D
  Petersburg, Virginia, United States
   | 
Copyright © 1999-2018 Engormix - All Rights Reserved
Aquaculture
search
search