Cleaning Instructions

 

Description: In operation it is normal for membrane elements to have some feed materials deposit on the membrane surface. When one or more of the fouling conditions have been a chemical cleaning of the membrane elements should be performed.

• Normalized* Permeate Flow Rate: 10% drop
• Normalized* Salt Passage: 10% increase
• Pressure Drop: 20% increase

Note: *Normalization is described in ASTM D4516-19a

Cleanings should be conducted before the elements are heavily fouled. In general, membrane cleanings should be expected to be required 1-4 times per year, although this can vary widely depending on the feedwater quality. If more than 4 cleanings are required per year, consider improved pre-treatment or altered operating conditions as frequent cleanings can reduce membrane life.

Optimal cleaners and cleaning procedures can vary from site to site based on feedwater composition and operating conditions. In the event that these instructions are unable to restore performance please reach out to your Aqua Membranes contact.

Tips:

• Keep the area clean
• Two people should be available for the cleaning process
• Ensure proper tools and materials are nearby:
  • Cleaning skid
  • Safety supplies and chemical spill neutralization kit
  • SDS for cleaning chemicals
  • Chemicals
  • pH meter
  • Temperature probe
  • Timer
• Clean one stage at a time to avoid feeding foulants into the next stage, and to minimize required pressures during cleaning
• When using surfactant-based cleaners, have return line below CIP solution to minimize foaming
• Neutralize all solutions before discharge per site and local requirements
• Don’t clean above pH 13
• Don’t use cleaners that contain free chlorine

Cleaning solution volume:

Cleaning solution volume will need to be sufficient both to fill the housings, provide excess volume to flush system during introduction of chemical agents, and to maintain the minimum volume the CIP skid needs to operate.

Cleaning batch size = (Element Volume + Piping Volume)*1.2 + minimum CIP volume

Element Volume = 2 gallons (7.6 liters) per 4040 / 8 gallons (30.3 liters) per 8040

Piping Volume and minimum CIP volume will vary with each system.

Cleaning Solutions:

1. High pH: 0.1% NaOH to pH 11.5, 0.03% Sodium Dodecyl Sulfate, 80F (26.7C)
2. Low pH: 2% Citric acid, HCl to pH2.5, 90F (32.2C)

Cleaning Procedure:

1. Record system data prior to shutdown
2. Flush feed from stage to be cleaned using RO permeate or DI water
3. Prepare CIP solution
4. Introduce the CIP solution at low flow rate
   a. 3 gpm (0.7 m3/hr) per vessel for 4040 based systems
   b. 15 gpm (3.4 m3/hr) per vessel for 8040 based systems
5. Discharge initial concentrate until pH is within 0.5 units of CIP solution
6. Recirculate for 0.5 hours starting time when solution is at temperature
   a. 10 gpm (2.3 m3/hr) per vessel for 4040 based systems
   b. 40 gpm (9.1 m3/hr) per vessel for 8040 based systems
7. Soak for 2-10 hours.
   a. Recirculate at a low flow as needed to maintain temperature
   b. Adjust pH as needed
   c. Discharge turbid or colored solution and replace as needed
8. Flush cleaning solution from skid with RO permeate
9. Neutralize used cleaning solution prior to discharge
10. Repeat as needed
11. Run to drain upon startup of the system for at least 10 minutes
12. Record system data 2 days after cleaning was conducted.

Cleaning Sequence:

Maintain a cleaning procedure that works for a specific site. In the absence of a known procedure, Aqua Membranes recommends the following sequence of cleaners:

1. High pH cleaning cycle
2. Low PH cleaning cycle

Membrane Element Start-up and Shut-down Procedures*

The first time Aqua Membranes RO elements are installed during normal operational startup, and during normal operational shutdown, certain precautions shall be observed to permit efficient operation of the elements.

Feedwater Requirements

• Free Chlorine: The free chlorine tolerance of the membrane is < 0.1 ppm. Continuous exposure may damage the membrane and should be avoided due to the potential to cause premature membrane failure. Aqua Membranes recommends removing residual free chlorine by pretreatment prior to membrane exposure.

• Turbidity: Confirm that RO feedwater turbidity and fouling potential, as measured by a 15-minute silt density index (SDI15), are within the limits. Spikes during start-up may result in membrane fouling that decreases permeance and requires higher pressures to maintain permeate flow.

• Temperature and pH: Confirm that RO feedwater temperature and pH are within the limits specified on the Aqua Membranes product data sheet. Operation at temperatures exceeding 45°C (113°F) may result in the compression of the RO membrane. This compression can result in compaction that permanently reduces the permeate flow through the membrane. Operation outside the listed pH limits may result in degradation of the RO membrane resulting in loss of rejection performance and shortened lifetimes.

Initial Start-up Steps

• Pre-Flushing: Prior to installing the membrane element(s), the system or train MUST be flushed to remove any debris, biological growth, and entrained air in the pressure vessel(s) and system piping.

• Element Loading: Confirm that all O-rings (end cap connectors and interconnectors) and brine seals are properly installed. Record loading schedule of Aqua Membranes elements using serial number and locations of each element, i.e.; pressure vessel and element position in pressure vessel. Ensure that the elements are shimmed to remove excess slack within the pressure vessel.
• Vent Entrained Air: Initiate a low pressure (15 – 20 psi/0.103- 0.137 mPa) flush to purge air from the membrane elements and pressure vessels prior to increasing to normal operating pressures. Venting should be performed with the permeate and concentrate valves completely open to drain. A soft-start mechanism or variable speed drive shall be used to avoid rapid pressure spikes.

• Membrane Flushing: After the air is entrained from the system, the feed pressure should be increased gradually using a soft-start mechanism or variable speed drive to the working pressure of the RO unit. The permeate produced for the first 15-minutes of plant operation should be discharged to waste. To ensure the highest quality permeate stream, the system should operate for 24-hours after the initial start-up. Depending on the application and needed permeate quality longer flushing may be needed.

Start-up Steps

• Control Valve: Prior to train or system start-up, confirm that the concentrate and permeate control valves are in the fully open position.

• Control Rate of Pressurization: No train or system should be brought online (pressurized) at a rate faster than 10 psi per second.

Data Collection

• Once the system has operated for 24-hours at the design pressure and recovery, data should be collected a minimum of once per day.

•  Data review can be provided by Aqua Membranes. Please inquire with your Aqua Membranes Sales or Engineering representative.

Shut-down Steps

Element Flush: Following system or train shutdown, it is required that the membrane
elements be flushed with RO Permeate or RO feedwater to remove the high concentration of salts contained in the membrane elements. An RO system or train should NEVER be shut down without immediately flushing the high TDS concentration from the membrane elements. Note that use of RO Permeate for element flush is preferred, particularly in applications where scaling may occur

*The information provided herein is deemed to be accurate and is o5ered in good faith, but without a guarantee of performance. Aqua Membranes assumes no liability for eitherresults obtained or damages incurred through the application of this information. The customer is responsible for determining whether the information presented is appropriate for the customer’s use and for ensuring that customer’s workplace and disposal practices are in compliance with applicable laws and other governmental enactments. Specifications subject to change without notice.