DESIGN
OF
REVERSE OSMOSIS
MEMBRANE
EXAMPLE 1
Estimate quality and quantity of the waste stream, and the
total quantity of the water that must be processed from a
reverse osmosis facility that is to produce 4000 m³/day of
water to be used for industrial cooling operations. Assume
that both the recovery rate and rejection rate are both 90
percent and that the concentration of the feed stream is
400g/m³.
SOLUTION:
1. Determine the flowrate of the concentrated waste stream and the total amount of water
that must be processed.
a. Concentrate stream flowrate equation:
𝑄𝑝 (1 − 𝑟)
𝑄𝑟 =
𝑟
b. Determine the concentrate stream flowrate:
3
4000 𝑚 𝑑𝑎𝑦 (1 − 0.9)
3
𝑄𝑟 =
= 444 𝑚 𝑑𝑎𝑦
0.9
3
c. Determine the total amount of water that must be processed to produce 4000 𝑚 𝑑𝑎𝑦 of
RO water:
3
𝑄𝑓 = 𝑄𝑝 + 𝑄𝑟 = 4000 + 444 = 4444 𝑚 𝑑𝑎𝑦
2. Determine the concentrate of the permeate stream:
𝑔
𝑔
𝐶𝑝 = 𝐶𝑓 1 − 𝑟 = 400
1 − 0.9 = 40
3
𝑚
𝑚3
3. Determine the concentration of the concentrated waste stream :
𝐶𝑐 =
3
𝐶𝑐 =
4444 𝑚 𝑑𝑎𝑦
400
𝑄𝑓 𝐶𝑓 − 𝑄𝑝 𝐶𝑝
𝑄𝑟
𝑔
3
− 4000 𝑚 𝑑𝑎𝑦
3
𝑚
3
444 𝑚 𝑑𝑎𝑦
𝐶𝑐 = 3643
𝑔
𝑚3
40
𝑔
𝑚3