Cleaning Guidelines: Cleaning Pure Water Membrane Elements
Cleaning Guidelines: Cleaning Pure Water Membrane Elements
Cleaning Guidelines: Cleaning Pure Water Membrane Elements
Bulletin
Cleaning Guidelines
Cleaning Pure Water Membrane Elements
These guidelines address when to clean and what The deposits including the precipitates, adsorbed or-
cleaners or sanitizers to use for each type of GE Water ganics and the biofilm are all called foulants, and they
& Process Technologies membrane element. The all impede the flow of water through the membrane.
guidelines are based on technical information, which This can result in unacceptably low permeate flow rate,
GE believes to be accurate and reliable. They are in- high operating pressure, and an excessive pressure
tended for persons with technical skill to use at their drop in the system, which may lead to irreversible ele-
own discretion and risk. Because of the conditions of ment damage. The foulants also increase the amount
use are outside our control, GE does not assume liability of dissolved material passing through the membrane,
for results obtained or damages incurred through the resulting in product water of unacceptable quality.
application of the cleaning solutions or procedures
suggested. All foulants must be removed through a clean in place
(CIP) process before irreversible membrane damage
When selecting a cleaner or sanitizer, several things occurs. It is, however, much easier to remove foulants
must be considered, including the foulant to be re- in the beginning of the fouling process than when a
moved, membrane element compatibility, and mem- thick fouling layer has been formed, so a CIP should be
brane type. Cleaning solutions must fall within pH performed when there are strong indications that the
ranges specified for the membrane element. In addi- fouling process has started.
tion, the cleaner must not contain certain chemical
substances incompatible with the membrane element, There are exceptions, for example many wastewater
such as certain surface-active agents and, in some in- applications, where membrane fouling starts upon
stances, oxidizing agents such as chlorine. Use of start of operation, and in such cases, the suitable
cleaning solutions other than those known to be com- cleaning frequency has to be determined case by case.
patible may reduce membrane life and void the GE
membrane element warranty. When to Clean
Membrane elements should be cleaned if either of the
Why to clean following conditions occurs:
During the operation of a membrane separation sys- 1. Normalized permeate flow drops 15% or greater
tem, the incoming water frequently brings suspended after the initial flow stabilization
solids and organic materials to the membrane surface.
Note - In many cases, the operator may expect
The suspended solids might get stuck on the mem-
some irreversible loss of permeate flow due to sys-
brane surface, helped by the feed channel spacer that
tem stabilization during the first 100 hours of initial
is in contact with the membrane. Dissolved organics
use. This loss is usually normal flow loss and does
might be adsorbed by the membrane, both on the outer
not necessarily indicate a need for cleaning. How-
surface and on the membrane pore walls. Dissolved
ever, the amount of lost flow should be carefully
species are concentrated in the elements, and it is pos-
monitored in case it is the result of an RO pretreat-
sible that they reach saturation conditions and precip-
ment system malfunction or the existence of con-
itate to form a scale on the membrane. Besides,
ditions not anticipated during system design.
microbes might settle down on the membrane surface
and build a biofilm, which becomes thicker the higher
the nutrients concentrations are in the feed solution.
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TB1194EN.docx Nov-16
2. Salt passage increases by 30 - 40%. Cleaning Solutions Temperatures
Note - Abrupt and significant changes in permeate
flow or salt passage can also be attributed to other The circulation of a heated cleaning solution through
factors, such as defective O-rings or flow by-pass the membrane elements often proves advantageous
around element brine seals. because higher temperatures increase chemical reac-
tion rates. Warm solutions often strip scale and/or con-
3. An Increase in normalized pressure drop (∆P) of taminants faster than ambient temperature solutions.
25% or greater. However, cleaning solution temperatures should be
Membrane element ∆P increases when foulants or kept under the limits specified for each membrane ele-
precipitates plug the feed spacers between the ment model. The operator risks damaging the mem-
membranes in spiral-wound membrane elements. brane element if cleaning solution temperature goes
When the ∆P has increased markedly, a considera- above its maximum recommended cleaning tempera-
ble amount of contaminants/sediment already has ture.
built up in the membrane element, so cleaning is
required. Safety Precautions
If element is too badly fouled, it is difficult to restore the When using any cleaning chemical, follow accepted
membrane element’s performance. safety practices. Read the labels on cleaning chemical
container and refer to the system operating manual. If
A spreadsheet for RO unit performance normalization in doubt about handling, safety or disposal procedures,
is available upon request. Please contact GE repre- contact the cleaning chemical supplier for detailed in-
sentative. formation before proceeding to prepare or use the
products. Several cleaners contain surfactants. This
Recommended Cleaner Recirculation may cause foaming during the CIP. It is recommended
and Soaking Times to have anti-foam on site. Consult with GE Membrane
Chemical specialist for further recommendations.
Most cleaning solutions should be circulated for 10-30
minutes, followed by a 10 to 30-minute soaking period Cleaning Solution Preparation
and then a final 10-minute recirculation prior to dis-
charging it. Chemical addition may be required during All solid cleaning chemicals should be fully dissolved
the recirculation to maintain the desired pH. The spent and well mixed before the cleaning solution is intro-
cleaning solution should be thoroughly flushed with RO duced into the system. Use RO quality water or filtered,
quality water to drain or holding tank. Please refer to low hardness water (less than one grain per gallon or
Table 2 for recommended cleaning solutions. 17 mg/L as CaCO3 of hardness to prepare cleaning so-
lutions. Reuse of cleaning solutions is not recom-
NOTE: Enzyme cleaners require longer residence times mended. Some cleaners have limited shelf life so check
to allow for complete reaction with the contaminate. the age of cleaners before using them.
Detergents containing enzymes should be allowed to
recirculate and soak for at least 1-2 hours before flush-
ing.
Suggested Cleaning Equipment
When contaminant removal is difficult, longer circula- A cleaning solution mixing tank with a cover and a tem-
tion and possibly additional soaking times may be use- perature gauge is suggested. Appropriate valving,
ful. An additional cleaning cycle with fresh cleaning sample ports, flow meters, pH monitor, pressure
solution is usually more effective. A foulant may be gauges, recirculation pump and cartridge filter are also
composed of different types of materials, making dif- recommended. When selecting cleaning system equip-
ferent cleaners and/or multiple cleaning cycles neces- ment, the material of construction of the system’s com-
sary to increase cleaning effectiveness. ponents should be chemically and physically
compatible with the cleaners and temperatures to be
The circulation flow during cleaning should be in the used. A cartridge filter on the cleaning solution return-
same direction as during normal system operation. Do to-tank or feed line to the crossflow filtration machine
not reverse flush from permeate manifolding through will remove particles dislodged from the membrane el-
membrane element as damage will occur. ements.
² NSF/ANSI Standard 60 Approved. This product is designed to be used off-line and flushed out prior to using the system for drinking
water.
Table 4: pH range during a 30-min cleaning - Refer to the element product fact sheet for further data
Element type Max temp > 50°C (122°F) 50°C > Temp > 35°C 35°C > Temp > 20°C Max Temp < 20°C
AC, AD, AE Contact GE for assistance 2.0-10.0 2.0 – 11.0 2.0 – 12.0
AG, AK, AP, MUNI RO, Industrial RO5 & RO6
J-Series, P-Series, BEV UF
Contact GE for assistance 1.0 – 10.5 1.0 – 12.0 1.0 - 13.0
S-Series, DuraSlick* RO, Industrial RO3 Contact GE for assistance 1.0 - 10.5 1.0 – 11.0 1.0 – 11.5
D-Series, DuraSlick NF, Industrial NF1
H-Series, MUNI NF
Contact GE for assistance 3.0 – 10.0 2.0 – 11.0 2.0 – 11.0
C-Series, BEV RO CA, BEV NF Contact GE for assistance Not allowed 4.0 – 6.0 3.0 - 8.0
G-Series Contact GE for assistance 2.0 – 11.0 1.0 – 12.0 1.0 – 13.0
M-Series Contact GE for assistance 3.0 - 10.0 2.0 – 11.0 2.0 – 11.0
Table 5: Chlorine tolerances - Refer to the element product fact sheet for further data
Element type Chlorine tolerance
A-series, MUNI RO, Industrial RO5 & RO6 < 1000 ppm x hours, dechlorination recommended
H-Series, MUNI NF < 1000 ppm x hours, dechlorination recommended
C-Series, BEV RO CA, BEV NF 1ppm maximum continuous 30ppm for 30 min. during sanitization
D-Series, DuraSlick NF, Industrial NF1 500 ppm x hours, dechlorination recommended
G-series 20-50 ppm x days
M-series 8,000 ppm x days
J-Series, P-series, BEV UF 5,000+ ppm x days
S-Series, DuraSlick RO, Industrial RO3 500 ppm x hours, dechlorination recommended