Waste water treatment: Desalination

Objective: To reduce the concentration of dissolved solids... Warm salt water Heat Cold salt water Fresh water Boiler Distillation Negative pressure In class Exercise Brine C=?. Heat Col

Fujairah RO Plant

Objective: To reduce the concentration of dissolved solids.

Methods

Methods  Distillation (multi-stage)

 Reverse Osmosis

 Electrodialysis

Warm salt water Heat

Cold salt water

Fresh water

Boiler

Distillation

Negative

pressure

In class Exercise

Brine C=?

Heat

Cold salt water Q=10MGD C=38,000 mg/l

Fresh water Q=8 MGD C=50 mg/l Steam

Reverse Osmosis (RO)

Membrane

Fresh water Saline water

Osmosis

Water movement

Reverse Osmosis

Fresh water Saline water

Pressure

Basic components of an RO unit

Fujairah SWRO Flow Sheet

Dual-media filters Cartridge filters RO units

Spiral-wound Module

Hollow-fiber module

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video

RO Design Equation

) ( ∆ − ∆ ψ

F w

water flux, gal/(d.ft 2 )

mass transfer coefficient per membrane unit area

pressure difference

osmotic pressure difference

2

25 Q / F 200 , 000 / 10 675 18 , 735 ft

Determine the membrane area of a reverse osmosis system that is required to demineralize 200,000 gallon per day with temperature of 10°C Pertinent data are as follows: K= 0.035 gal/(day-ft2)(psi) at 25 °C, ∆ψ = 45 psi, ∆p= 350 psi, lowest operating temperature is 10 °C, and the membrane area correction

factor A 10°C/A 25°C =1.58

Solution

2

/ 675

10 )

45 350

( 035 0 )

K

2 25

10 1 58 A 29 , 602 ft

A o C = × o C =

Cathode

⊕ ⊝ ⊝

⊝ ⊝

⊝

⊕ ⊕ ⊕

⊕

⊝

Saline water

Fresh water

Anode

c

r

nE

FQNE

I=current F= 96,500 amp-sec per eq removed

Q=flow rate N=normality of solution

Er = removal efficiency

Ec = current efficiency n= number of cells

2 3

2

2640 10

4 26

8 69

/ 4

26 400

066

0

cm density

current

current A

cm amp

milli density

current

=

×

=

=

=

×

=

−

Given that n=200, Q=90,000 gal/d, Co=4000 mg/l, cation or anion content is 0.066 eq/l Current efficiency= 90% Salt removal efficiency= 50% Resistance 4.5 ohms, current density (milli amp/cm2)/normality ratio = 400 What is the required current, the area of the membrane, and the power needed?

Solution

amp

d gal

l l

eq d

gal eq

amp nE

FQNE

I

c r

8

69

} sec 400 , 86

785 3 { 9 0

1 200

1 5

0 066

0 000

, 90 sec

500

,

96

=

×

×

×

×

×

×

×

⋅

=

=

watts RI