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Claculating feeding rate using flow rate

 
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Stephanie Reiner



Joined: 28 Oct 2010
Posts: 1
Location: Virginia

PostPosted: Fri Oct 29, 2010 1:08 pm    Post subject: Claculating feeding rate using flow rate Reply with quote

I'm trying to calculate the feeding rate of larvae on algae cells in a tank that has water flowing into and out of it at a continuous rate but am not sure if this is right.

Inflow water: 1.4 L/min
Inflow algae: 0.055 L/min
Total inflow: 1.4 + 0.055 = 1.455 L/min (algae inflow connected to water inflow, so they enter tank through same pipe)
Outflow: 1.455 L/min (water flows out at rate it is coming in)
*Inflow conc. algae: 70,000 cells/mL
*Outflow conc. algae: 25,000 cells/mL

*I'm assuming the algae inflow/outflow conc. are constant for the entire day

Please let me know if this calculation is correct:

70,000 cells/mL * 1.455 L/min * 1 mL/0.001L = 101,850,000 cells/min coming in

25,000 cells/mL * 1.455 L/min * 1 mL/0.001L = 36,375,000 cells/min going out

101,850,000-36,375,000 = 65,475,000 cells/min retained in tank to be fed on

65,475,000 cells/min * 60 min/hr * 24 hr/day = 9.4 x 10^10 cells/day

This seems like way too many, and I feel like I'm missing a step. Any help is appreciated! Thanks!
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hepcj
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Joined: 23 Jun 2007
Posts: 125

PostPosted: Sat Oct 30, 2010 4:36 pm    Post subject: Reply with quote

I think the problem is in this part:

70,000 cells/mL * 1.455 L/min * 1 mL/0.001L = 101,850,000 cells/min coming in

25,000 cells/mL * 1.455 L/min * 1 mL/0.001L = 36,375,000 cells/min going out

Water is incompressible and so the rate of flow in will equal the rate of flow out. The question gives the inflow is 0.055 L/min = 55mL/min and the number of cells entering and exiting.

55 mL/min x 70,000 cells/mL = 3,850,000 cells/min
55 mL/min x 25,000 cells/mL = 1,370,000 cells/min

difference = 3,850,000 cells/min - 1,370,000 cells/min = 2,480,000 cells/min left in tank.

Thanks for your question.
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