Accepta 2628 – Membrane Cleaner
Description and Use
ACCEPTA 2628 is a mildly-acidic cleaning agent for removing fouling caused by iron salts, oxides and hydroxides. It can also be used to remove light calcium carbonate scaling.
Membrane cleaning is recommended when any of the following fouling indications
- A 10-15% reduction in the normalised Permeate Flow
- A 10-15% increase in the normalised salt content of the permeate
- A 10-15% increase in the differential pressure across the membrane housing
A 4% solution should be made up with clean, chlorine-free water. The solution should be circulated through the membrane housings using an appropriate CIP rig. A typical cleaning cycle would involve alternately circulating and soaking for 15 minute intervals for 2-3 hours before draining and flushing with permeate or good quality water. If during the cleaning the solution becomes red/brown in colour it should be replaced by fresh solution because it has become exhausted.
Appearance ……………………………….. Colourless to pale straw coloured liquid
pH …………………………………………… approx. 3.5 – 4
Specific Gravity …………………………. approx. 1.16
Cleaning Programme Recommendations (CIP)
The membranes should be cleaned in line with the following changes in normalized data:
- Permeate Flow decreases by 10-15%
- Salt Passage Increases by 10-15%
- Pressure Drop (∆P) Increases by 10-15%
Allowing conditions to deteriorate significantly worse than these values is a major cause of permanent membrane damage.
There are many combinations of cleaning chemicals and conditions of use. It is good practice to vary the cleaning schedule, and from time to time use different cleaners. Experience will show what is best for a specific system and the cleaning sequence shown below is considered suitable for your system, based on the data available.
The following two-stage cleaning programme should be carried out every three months (or more often if necessary, according to the parameters mentioned above) to ensure that biofilm and associated organic matter, iron deposits and inorganics are removed from the membranes.
RO CLEAN A is a formulated blend of alkaline cleaners with a low foaming surfactant developed specifically for dispersing organic debris including silica. It is of vital importance that cleaning solution temperature should be 35 – 40°C in order to optimise cleaning but should not exceed the maximum allowable temperature as specified by the membrane manufacturer.
NB: If cleans are attempted below this temperature kinetics of the chemical reaction will not be sufficient to allow thorough membrane cleaning
Protocol: This may depend on allowable downtime and automated programming options, but we would suggest the following regime:
- CIP volume is based on 40 litres of permeate water per 8” membrane. Cleaning Stages 1 & 2 together – 24 elements total requires 960 litres of CIP solution.
- In order to minimise temperature drop during the cleaning process we recommend heating the CIP tank to 35°C with permeate water (no chemical) and soaking the membranes for a suitable period to ensure that membranes are at the optimum temperature at the start of the cleaning process. This will improve cleaning efficiency.
- The cleaning solution can then be prepared as below, again ensuring that solution pH and temperature are within membrane manufacturers guidelines.
- We suggest a 30 minute recycle period followed by a 20-minute soak, after each step take a sample of water – if visual inspection reveals the water is excessively dirty then we would recommend dumping to drain and starting with a fresh cleaning solution. Ensure pH remains at 11.0 by adjusting with RO CLEAN A as required.
- The soak/recycle should be repeated 3 times as a minimum or until cleaning solution appears satisfactory to visual inspection (total time 4 -6 hours)
- Divert CIP solution to drain and flush membranes with permeate water for 20 minutes or until pH is restored to natural values.
RO CLEAN C is an inorganic scale remover and iron deposit cleaner.
- Immediately after flushing from stage 1 prepare RO CLEAN C solution at temperatures as indicated below.
- Repeat soak/recycle protocol as per above, carrying out a visual inspection after each step to ensure solution is clean. Solution should be refreshed if excessively dirty.
- If the pH rises above 4.2 during the process, we recommend dumping the cleaning solution to drain and preparing a fresh solution.
- On completion flush with permeate water until natural values are restored.
Summary of Cleaning Protocol
|1||RO CLEAN A||3-4% vol/vol||11.0||35-40oC||4-6 hours|
|Flush||Permeate water||Natural values||20 mins|
|2||RO CLEAN C||2-3% vol/vol||3.7||25-30oC||As above|
|Flush||Permeate water||Natural values||30 mins|
Flushing: Always flush the membrane thoroughly between cleaning stages and before returning the system to routine operation. Ensure all traces of cleaning products have been removed.
Caution: Always follow the membrane manufacturers’ guidelines with respect to cleaning programmes.