Commissioning / Decommissioning
Part 1 • Page 8-3
Part 1 – Operating Instructions
Rev. 6.4 dated 2022-02
Software Released Version: 1
(Eco)RO Dia II
Part 1 • Chapt
er 8
8.6
Technical memo for PRESERVATION with sodium metabisulphite
Protection against contamination and stabilisation of reverse osmosis membranes
•
Before preservation, rinse the membranes with good-quality water free of chlorine (dissolved solid
matter < 5.0 g/l). Use 120 litres of water for each 8-inch membrane.
Table 8-1:
Filling volumes of preservative / antifreeze
Preservation using sodium metabisulphite
•
If biofouling of the membrane is not to be expected and if the membrane is to be protected for storage,
a solution with 0.5 wt./vol.% sodium metabisulphite can be used.
9.5% wt./vol.% glycerin must be added to guarantee frost protection down to -5 °C.
•
It is helpful to produce a basic solution with sodium metabisulphite in a 20-fold concentration and to fill
the supply tank with this basic solution.
Stabilisation
•
200 – 350 mg/l magnesium chloride (in the form of Mg++ MgCl2) must be added to maintain
membrane stability if this solution is to be stored for longer than one month.
•
Let the preservative solution circulate through the membrane. Recirculate the solution through the
mixing tank for one hour. The temperature must not exceed 35 °C.
•
It is helpful here, too, to produce a basic solution with MgCl
2
in a 20-fold concentration and to fill the
supply tank with this basic solution.
Emptying the supply tank
•
Empty the mixing tank down the waste drain when the protective treatment has been completed.
•
Only leave the preservative solution in the membrane after completing the steps above if the
membrane will not be subject to frost.
Flushing
•
To flush out the preservative solution (element 8040), a maximum permeate production and
a concentrate flow of at least 60 l/min (35 min – 45 min) is required.
•
Flushing can be terminated when the conductivity in the permeate (display)
is 2 –10 µS/cm (depending on yield and raw water constitution).
Number of
modules
Sodium
metabisulphite
[gr]
MgCl
[gr]
Glycerin
86% for
-5°C [litres]
Glycerin
86% for
-9°C [litres]
Glycerin
86% for
-17°C [litres]
Total volume of
liquid for RO
[litres]
1
450
30
9.0
12.8
18.0
90
2
550
35
11.0
15.7
22.0
110
3
650
40
13.0
18.5
26.0
130
4
750
45
15.0
21.5
30.0
150
5
850
50
17.0
24.5
34.0
170
6
950
55
19.0
27.5
38.0
190
NOTE
If the system is exposed to a temperature of
0 °C (during transport etc.), it must be
emptied completely (especially the membrane), as otherwise excess pressure due to water
anomaly could cause the pipelines and membrane to be destroyed.
