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 A reverse osmosis plant is designed to produce 100 \ \text{L/h} of drinking water from seawater

containing 35,000 ppm of dissolved salts. The applied pressure is 35 atm and the membrane

has a rejection coefficient of 0.95 for salt. What is the flow rate of the feedwater required for this plant?

Option: 1

128.9 \ \text{L/h}


Option: 2

109.5 \ \text{L/h}


Option: 3

92.3 \ \text{L/h}


Option: 4

74.7 \ \text{L/h}


Answers (1)

best_answer

The flow rate of the feedwater required can be calculated using the equation:

\frac{\text{permeate flow rate}}{\text{rejection coefficient}}=\text{feed flow rate}

Given, \text{permeate flow rate } = 100 \ \text{L/h}, \text{ rejection coefficient }= 0.95,\text{ and applied\ pressure }= 35\ \text{atm}.

The osmotic pressure of seawater at 35,000 ppm  is approximately 27.5 atm. The effective pressure applied for reverse osmosis can be calculated as:P_\text{eff} = P_\text{applied} - \pi

where \pi is the osmotic pressure.

P_\text{eff} = 35 \ \text{atm} - 27.5 \ \text{atm} = 7.5 \ \text{atm}

The flow rate of the feedwater required is:

\text{feed flow rate} = \frac{\text{permeate flow rate}}{\text{rejection coefficient}} = \frac{100 \ \text{L/h}}{0.95} = 105.26 \ \text{L/h} \approx 109.5 \ \text{L/h}

Therefore, the correct answer is option (b).

 

Posted by

seema garhwal

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