1. Element Loading and unloading

1.1 Storage of elements

Load elements immediately upon delivery, if possible. If you are not able to load the membranes immediately upon delivery, be sure to store elements out of direct sunlight. Only store within temperature a temperature range 32°F (0°C) to 95°F (35°C).

1.2 Flushing

If the system is new, it is strongly recommended that you flush the system (pipes, pumps, pressure vessels, etc.) with clean, fresh water prior to loading the element. This allows any debris, preservatives, and/or solvents to be flushed out so that they do not come into contact with the membranes.

1.3 Preparation (Material, tools and equipment requirements)

• Glycerin
• Pure silicone lubricant (Molykote 111)
• Permeate or fresh water to flush vessel
• PVC pipe or rope – length depends on the length of pressure vessels
• Sponge ball (to be fixed at one end of PVC pipe or rope)
• Towel or cotton rag
• 6” PVC Cap (when loading 8” pressure vessels)
• Shims (sizes of 1mm, 2mm, 2.5mm and 5 mm thickness recommended)
• Brush or dauber for lubrication of brine seals
• Tools as recommended by the manfacturer of your pressure vessel for removing and installing of the end cap assembly
• Spare parts for end caps (e.g. o-rings, lock rings, Victaulic clamps, nuts, bolts)
• Personal protection equipment (e.g. gloves, glasses, shoes, hard hat)

Note: When loading elements into the system, do not use oil, grease, or petroleum based compounds to lubricate o-rings or brine seals, as these may cause damage to membrane or other components of the element. Use only silicone-based gel or 100% glycerin to lubricate o-rings and brine seals.

1.4 Loading of Pressure Vessels

1. Remove pressure vessel end caps from both sides of the vessel (Note: Refer to pressure vessel manufacturer’s manual for removal and re-installation of end caps assemblies).
2. Before assembling all components, check the parts list and make sure all items are present and in the right quantities.
3. Carefully remove all dust, dirt, and foreign matter from the pressure vessels before opening.
4. Use a sponge ball wrapped in a towel or cotton rag and soaked in a 50-75% solution of glycerin and water. The sponge ball can be pushed/pulled through the vessel with a piece of rope or long PVC pipe. Alternatively, the sponge ball can be pushed through the length of the vessel with a piece of PVC pipe with a PVC flange attached to the end. The glycerin solution will lubricate the inside surface of the pressure vessel to ease the loading of elements.
5. After cleaning the pressure vessel, re-install the brine side end cap assembly without covering the side port openings with the thrust cone/sleeve. Before installation, lubricate end plate permeate adaptor O-rings and head seal with thin layer of pure silicone lubricant or 100% glycerin.

Note: A 65% Glycerin+30%Water+5%SBS (sodium metabisulfite) solution can be safely used to help disinfect the vessels. Also, a 15:1 mixture of water and SBS (add about 1 cup of SBS powder in 1 gallon of water) can be made to swab the vessels for disinfection and lubrication.

Caution: Be sure to avoid scraping the pipe along the vessel surface. Also, take care to push the end cap in squarely to avoid rolling the head seal.

1.5 Loading of elements

1. Prior to loading, ensure all brine side end cap assemblies (including thrust cone/sleeve, head seal, end adapters, O-rings, etc.) are installed in the pressure vessels.
2. Maintain a loading record of each element serial number, vessel location, and position.
3. Open the element bag partially and expose the upper one-third of the element. This allows for the operator to have minimum exposure to the Fiberglass Reinforced Plastic (FRP) shell, while installing each element.
4. Gently slide the first element into the feed side of the pressure vessel three-quarters of the way, unwrapping the element from its plastic wrapping as you go.

   Note: Always load elements in feed flow direction with brine seal properly seated in seal groove of anti-telescoping device (ATD) and facing the flow direction. If the element uses a V-cup brine seal, ensure that the V-cup seal opens in the flow direction (Figure 1.1).

   

   Figure 1.1 Element Loading Direction

   Note: The flow direction may not be the same for all vessels in a system.

   Caution: Never put V-cup brine seals on both ends of an element.

   Caution: RO elements are preserved with a solution containing 1% sodium bisulfite. Avoid direct contact with this solution.

5. Gently lubricate interconnector O-rings with a thin layer of pure silicone lubricant and insert interconnector in permeate tube of first element.
6. Lubricate element brine seal with glycerin solution using brush or dauber.
7. Connect the next element to the interconnector and push both elements into the pressure vessel up to three-quarters of the length of the element, continue to unwrap the element as you go.

   Caution: Ensure the weight of the outboard element is not supported by the interconnector by supporting the element if necessary (Figure 1.2).

   

   Figure 1.2 Interconnector Configuration Between Two RO Elements

8. Repeat above steps with all other elements.
9. When installing last element, push the element stack completely inside the pressure vessel towards the brine end until the last element fully connects with end plate permeate adaptor on brine side of the pressure vessel. Avoid “slamming” the stack up against brine end as damage may occur.

   Caution: It is extremely important to avoid pinch points where fingers and hands can be crushed while elements are moving into the vessels.

10. After loading all elements determine if shimming the vessel is necessary prior to installing the upstream end cap.

1.6 Pressure Vessel Shimming

All pressure vessels are built with some tolerance in length to account for small differences in the length of the elements. Furthermore, the length of the pressure vessel also changes slightly due to expansion during operation. Therefore it is recommended that you shim elements as needed, in order to take up free space in the vessel. This helps to prevent elements from moving when the system is shutting down and starting up. The appearance of leaks between elements is also minimized when the elements are shimmed and membrane's potential for movement is minimized. Insufficient shimming can lead to premature wear of interconnector and end plate adaptor O-rings or even to premature disconnections of elements from their end plate adaptors. This will result in feed-to-permeate leaks and poor permeate quality.

Note: Always shim vessels from feed end side. Shimming from brine end side can lead to telescoping of the elements.

The following procedure is recommended to shim the pressure vessel:

1. Remove the adapter O-ring and head seal from the feed end of these vessel components
2. Remove adapter from head assembly and gently lubricate adapter seal with pure silicone lubricant
3. Insert adapter into permeate port of the Test Head assembly
4. Gently install Test Head assembly into place until the bearing plate is seated properly up to the retaining ring groove on the pressure vessel
5. Gently remove Test Head assembly from pressure vessel and measure the remaining gap between adapter and permeate port (Figure 1.3).

   

   Figure 1.3 Shimming

6. Insert required number of shims in adaptor to completely fill the gap, then insert the adapter back into the Test Head assembly permeate port.
7. Install O-rings and head seals and lubricate them gently with pure silicone lubricant
8. Install all end cap assemblies.
9. Finally, install all end cap retaining devices (segmented ring or spiral lock ring).
10. Re-install all connecting pipes. Note: A gap of 2 mm between the end plate and the shims will not cause problems in performance
11. Slowly fill the system with water at low pressure to prevent hydraulic shock (water hammer) at start-up. When all air is purged from the system, slowly bring the system up to design pressure and flow. SpiroPure® recommends that the RO system be pressurized at no more than 10 psi (0.69 bar) per second to ensure no damage is done to the membrane element.
12. After operating for a few hours to a few days, stop the plant and inspect the end adaptor insertion. It is possible that the membranes will shift slightly 4 during initial operation. See Figure 1.4 and Figure 1.5 below.

    

    Figure 1.4 End Adaptor –Correct Position

    
    

    

    Figure 1.5. End Adaptor –Incorrect Position

1.7 Storage of new elements in pressure vessels

Once the elements are de-bagged and placed in the clean pressure vessel (PV) and shimmed, the PV should be closed and sealed from outside contamination. The elements will still have some SBS preservative in them, but this will be minimal and will not effectively prevent microbiological growth. SpiroPure® thus highly recommends that the elements be flushed with in-spec feedwater, clean permeate or other comparable water within 30 days after de-bagging.

1.8 Element unloading

Standard elements: Two operators are recommended when removing NF or RO elements from a train or system. Remove the element from each pressure vessel as follows:

1. Disconnect the hard plumbing at each end of the pressure vessel. Refer to the vessel manufacturer’s manual as required. Mark or tag all removed items for return to the same location. Note: Numbering of the endplates and reinstalling in the same vessel is very important, this makes reinstallation much easier and all the connections will line up properly.
2. Remove the head assemblies from each end of the pressure vessel.
3. Push the NF or RO elements from the pressure vessel in the same direction as feedwater flows. Push the elements out one at a time. Support each element as it is being pushed out of the vessel until the element is free of the pressure vessel.

2. System Operation

2.1 Introduction

Successful long-term performance of the membrane system (NF and RO) depends on proper operation and maintenance of the system. This includes the initial plant start-up and operational start-ups and shut-downs. Record keeping and data normalization is required in order to know the actual plant performance and to enable corrective measures when necessary. Complete and accurate records are also required in case of a system performance warranty claim.

2.2 Initial Start-Up

Before initiating system start-up procedures, you should complete all: pretreatment checks, loading of the membrane elements, instrument calibration and other system checks.

2.2.1 Equipment

The initial system start-up is typically performed just after the element loading. The material needed for element loading is listed in Section 1.3, Preparation. For start-up, the following additional equipment is recommended – this should also be part of the equipment at the site:

• Safety glasses when working with chemicals
• Thermometer
• pH meter
• Conductivity meter (range: from permeate to concentrate conductivity)
• SDI measuring equipment
• Adequate chemicals for cleaning, sanitization and preservation
• Scale to weigh one element
• Spare elements
• Single-element test stand (for large systems > 500 elements)
• Bottles for water samples:
  • Volume: at least 125 mL
  • Material: HDPE (high density polyethylene)
  • Number: sufficient to sample raw water, system feed, system permeate and system concentrate. In case of a system with more than one train, each train is to be sampled separately. In case of systems with more than one stage, permeate samples of the individual stages and feed/concentrate samples from in-between the stages have to be added. The operating conditions of the membrane system during sampling have to be provided.
• Analysis equipment for:
  • Total hardness
  • Calcium
  • Alkalinity
  • Chloride
  • Sulfate
  • Iron
  • Silica
  • Free chlorine
  • Redox potential
  • TOC
  • Color (a large white container may suffice to detect color in the permeate)

2.2.2 Pre-Start-Up Check and Commissioning Audit

After having loaded the elements into the pressure vessels and before starting up the membrane unit, make sure that the whole pretreatment section is working in accordance with the specifications.

Furthermore, absence of chlorine, turbidity and SDI must be determined.

The raw water intake must be stable with respect to:

• Flow
• SDI
• Turbidity
• Temperature
• pH
• Conductivity
• Bacteria (standard plate count)

The following checks of the pretreatment system and the membrane unit are recommended for the initial start-up (results to be included in the start-up report):

Pre-Start-Up Checklist

• Corrosion-resistant materials of construction are used for all equipment from the supply source to the membrane including piping, vessels, instruments and wetted parts of pumps
• All piping and equipment is compatible with designed pressure
• All piping and equipment is compatible with designed pH range (cleaning)
• All piping and equipment is protected against galvanic corrosion
• Media filters are backwashed and rinsed
• New/clean cartridge filter is installed directly upstream of the high-pressure pump
• Feed line, including RO feed manifold, is purged and flushed, before pressure vessels are connected
• Chemical addition points are properly located
• Check/anti-siphon valves are properly installed in chemical addition lines
• Provisions exist for proper mixing of chemicals in the feed stream
• Dosage chemical tanks are filled with the right chemicals
• Provisions exist for preventing the RO system from operating when the dosage pumps are shut down
• Provisions exist for preventing the dosage pumps from operating when the RO system is shut down
• If chlorine is used, provisions exist to ensure complete chlorine removal prior to the membranes
• Planned instrumentation allows proper operation and monitoring of the pretreatment and RO system
• Planned instrumentation is installed and operative
• Instrument calibration is verified
• Pressure relief protection is installed and correctly set
• Provisions exist for preventing the permeate pressure from exceeding the feed/concentrate pressure more than 5 psi (0.3 bar) at any time
• Interlocks, time delay relays and alarms are properly set
• Provisions exist for sampling permeate from individual modules
• Provisions exist for sampling raw water, feed, permeate and concentrate streams from each stage and the total plant permeate stream
• Pressure vessels are properly piped both for operation and cleaning mode
• Pressure vessels are secured to the rack or frame per manufacturer’s instructions
• Precautions as given in Section 4, Loading of Pressure Vessels, are taken
• Membranes are protected from temperature extremes (freezing, direct sunlight, heater exhaust, etc.)
• Pumps are ready for operation: aligned, lubricated, proper otation
• Fittings are tight
• Cleaning system is installed and operative
• Permeate line is open
• Permeate flow is directed to drain (In double-pass systems, provisions exist to flush first pass without permeate going through the second pass)
• Reject flow control valve is in open position
• Feed flow valve is throttled and/or pump bypass valve is partly open to limit feed flow to less than 50% of operating feed flow

2.2.4 Start-Up Sequence

Proper start-up of reverse osmosis (RO) and nanofiltration (NF) water treatment systems is essential to prepare the membranes for operating service and to prevent membrane damage due to excessive pressure/flow or hydraulic shock.

Following the proper start-up sequence also helps ensure that system operating parameters conform to design conditions so that water quality and productivity goals can be achieved. Measurement of initial system performance is an important part of the start-up process. Documented results of this evaluation serve as benchmarks against which ongoing system operating performance can be measured.

Typical Start-Up Sequence

Following is the recommended RO system start-up sequence:

1. Before initiating the start-up sequence, thoroughly rinse the pretreatment section to flush out debris and other contaminants without letting the feed enter the elements. Follow the Pre-Start-up check described in Section 2.2.2, Pre-Start-up Check and Commissioning Audit.
2. Check all valves to ensure that settings are correct. The feed pressure control and concentrate control valves should be fully open.
3. Use low-pressure water at a low flow rate to flush the air out of the elements and pressure vessels. Flush at a gauge pressure of 30-60 psi (0.2-0.4 MPa). All permeate and concentrate flows should be directed to an appropriate waste collection drain during flushing. Air remaining in the elements and/or in the pressure vessels may lead to excessive forces on the element in flow direction or in radial direction and causing fiberglass shell cracking, if the feed pressure is ramped up too quickly.
4. During the flushing operation, check all pipe connections and valves for leaks. Tighten connections where necessary.
5. After the system has been flushed for a minimum of 30 minutes, close the feed pressure control valve.
6. Ensure that the concentrate control valve is open. Starting against a closed or almost closed concentrate valve could cause the recovery to be exceeded which may lead to scaling.
7. Slowly crack open the feed pressure control valve (feed pressure should be less than 60 psi (0.4 MPa).
8. Start the high-pressure pump.
9. Slowly open the feed pressure control valve, increasing the feed pressure and feed flowrate to the membrane elements until the design concentrate flow is reached. The feed pressure increase to the elements should be less than 10 psi (0.07 MPa) per second to achieve a soft start. Continue to send all permeate and concentrate flows to an appropriate waste collection drain. If the feed pressure and/or the feed flowrate are ramped up too quickly, the housing of the elements may be damaged by excessive forces in flow direction and/or in radial direction - especially if air is in the system - leading to telescoping and/or fiberglass shell cracking.
10. Slowly close the concentrate control valve until the ratio of permeate flow to concentrate flow approaches, but does not exceed, the design ratio (recovery). Continue to check the system pressure to ensure that it does not exceed the upper design limit.
11. Repeat steps "9" and "10" until the design permeate and concentrate flows are obtained.
12. Calculate the system recovery and compare it to the system's design value.
13. Check the addition of pretreatment chemicals (acid, scale inhibitor and sodium metabisulfite if used). Measure feedwater pH.
14. Check the Langelier Saturation Index (LSI) or the Stiff & Davis Stability Index (S&DSI) of the concentrate by measuring pH, conductivity, calcium hardness, and alkalinity levels and then making the necessary calculations.
15. Allow the system to run for one hour.
    Note: Permeate obtained from first hour of operation should be discarded.
16. Take the first reading of all operating parameters.
17. Check the permeate conductivity from each pressure vessel to verify that all vessels conform to performance expectations (e.g., vessels with leaking O-rings or other evidence of malfunction to be identified for corrective action).
18. After 24-48 hours of operation, review all recorded plant operating data such as feed pressure, differential pressure, temperature, flows, recovery and conductivity readings (please refer to Section 2.6.1). At the same time, draw samples of feedwater, concentrate and permeate for analysis of constituents.
19. Compare system performance to design values.
20. Confirm proper operation of mechanical and instrumental safety devices.
21. Switch the permeate flow from drain to the normal service position.
22. Lock the system into automatic operation.
23. Use the initial system performance information obtained in steps "16" through "18" as a reference for evaluating future system performance. Measure system performance regularly during the first week of operation to check for proper performance during this critical initial stage.

    

    Figure 2.1 Typical RO/NF system

2.2.4 Membrane Start-Up Performance and Stabilization

The start-up performance of an RO/NF membrane system and the time required to reach the stabilized performance depends on the prior storage conditions of the membrane. Dry membranes and wet preserved membranes, if properly stored, reach the same stabilized performance after some hours or a few days of operation. The flow performance of wet membranes is typically stable right from the start, while dry membranes tend to start at a slightly higher flow. The salt rejection of SpiroPure® Membranes in general improves during the first few hours or days of operation and remains stable then.

2.2.5 Special Systems: Double-Pass RO

When a double-pass system is started up, the first pass system must have been in operation for at least 24 hours before the permeate of the first pass is fed to the membranes of the second pass. Otherwise a permanent flux loss of the second pass may result. The pH of the feedwater to both passes have to be adjusted for optimal results in rejection. A final product water conductivity of ˂ 1 μS/cm is being obtained routinely from brackish water sources with double-pass BWRO membrane systems.

2.3 Operation Start-Up

Once a membrane system has been started up, ideally it should be kept running at constant conditions. In reality, membrane plants have to be shut down and restarted frequently. Start/stop cycles result in pressure and flow changes, causing mechanical stress to the membrane elements. Therefore, the start/stop frequency should be minimized, and the regular operation start-up sequence should be as smooth as possible. In principle, the same sequence is recommended as for the initial start-up. Most important is a slow feed pressure increase, especially for seawater plants.

The normal start-up sequence is typically automated through the use of programmable controllers and remotely operated valves. The calibration of instruments, the function of alarms and safety devices, corrosion prevention and leak-free operation have to be checked and maintained on a regular basis.

2.4 RO and NF Systems Shut-down

An RO/NF system is designed to be operated continuously. However, in reality, membrane systems will start up and shut down with some frequency. When the membrane system is shut down, the system must be flushed, preferably with permeate water, or alternatively with high quality feedwater, to remove the high salt concentration from the pressure vessels until concentrate conductivity matches feedwater conductivity. Flushing is done at low pressure (about 40 psi (3 bar)). A high feed flowrate is sometimes beneficial for a cleaning effect; however, the maximum pressure drop per element and per multi-element vessel – as stated on the SpiroPure® Membranes product information sheet - must not be exceeded. During low-pressure flushing, the vessels of the last stage of a concentrate-staged system are normally exposed to the highest feed flowrates and therefore they show the highest pressure drop.

The water used for flushing sould not contain any chemicals used for pretreatment--it is especially important that you use no scale inhibitors. After flushing the system, close the feed valves completely. If the concentrate line ends into a drain below the level of the pressure vessels, then an air break should be employed in the concentrate line at a position higher than the highest pressure vessel. Otherwise, the vessels might be emptied by a siphoning effect.

When the high-pressure pump is switched off, if the feed/concentrate side has not been flushed out with permeate water, a temporary permeate reverse flow will occur by natural osmosis. This reverse flow is sometimes referred to as permeate draw-back or suck-back. Permeate suck-back alone or in combination with a feed-side flush may provide a beneficial cleaning effect. To accommodate permeate suck-back, enough water volume should be available to prevent a vacuum from being drawn or air being sucked back into the membrane element.

If the permeate line is pressurized during operation and the system shuts down, the membrane might become exposed to a static permeate backpressure. To avoid membrane damage from backpressure, the static permeate backpressure must not exceed 5 psi (0.3 bar) at any time. Check valves or atmospheric drain valves in the permeate line can be used to safeguard the membrane. These safeguard valves need to work also and especially in case of non-scheduled shut- downs, e.g., because of a power failure, or emergency shut-downs.

When the system must be shut down for longer than 48 hours, take care that:

• The elements do not dry out. Dry elements will irreversibly lose flux.
• The system is adequately protected against microbiological growth, or regular flushing is carried out every 24 hours.
• When applicable, the system is protected against temperature extremes.

The membrane plant can be stopped for 24 hours without preservation and precautions for microbiological fouling. If feedwater for flushing every 24 hours is not available, preservation with chemicals is necessary for longer stops than 48 hours.

2.5 Adjustment of Operation Parameters

2.5.1 Introduction

A membrane system is designed on the basis of a defined set of data such as the permeate flow, feedwater composition and temperature. In reality, the plant operation has to be flexible to respond to changing needs or changing conditions.

2.5.2 Brackish Water

The normal way of operating brackish water RO and NF membrane plants is to keep the flows, and thus the recovery constant, at the design values. Any change in the membrane flux, e.g., by temperature or fouling, are compensated by adjusting the feed pressure. However, the maximum specified feed pressure must not be exceeded, nor should too much fouling be tolerated (for cleaning, please refer to Section 3 Cleaning).

If the feedwater analysis changes such that the scaling potential increases, the system recovery has to be decreased, or other measures have to be taken to cope with the new situation.

The most common situation is that the permeate capacity of the plant has to be adjusted to the needs. Normally, the capacity is designed to meet the peak needs. Operating with overcapacity is generally not recommended. Thus, adjustment means lowering the design permeate output. The easiest way is to shut the plant down when no permeate is needed. A high start/stop frequency, however, can lower the performance and the lifetime of the membranes. A permeate buffer tank may be used to allow a more constant operation.

Reducing the feed pressure is another way to reduce the permeate flow. Preferably, this is done by using a speed controlled pump in order to save energy. Normally, the system recovery is kept constant when the permeate flow is reduced. It has to be ensured by a system analysis using the computer program, that single-element recoveries do not exceed their limits. During low flow operation, the system salt rejection is lower than during design flow operation. Also, you must be certain that minimum concentrate flows are maintained during low flow operation.

2.5.3 Seawater

In principle, the operation parameters of seawater plants are adjusted the same way as in brackish water applications.

However, the maximum allowed feed pressure as specified on the product information sheet, and the permeate TDS are often the limiting factors.

Decreasing feedwater temperature can be compensated by increasing the feed pressure up to the maximum. Once the maximum pressure is reached, a further decreasing temperature causes the permeate flow to decrease.

Increasing temperature is compensated by lowering the feed pressure. This is only possible, however, as far as the tolerated permeate TDS is not exceeded. Alternatively, increasing temperature can be compensated by taking a number of pressure vessels out of service. By reducing the active membrane area, the feed pressure and the permeate TDS are kept about constant. A system analysis has to be run to make sure that maximum element permeate flows are not exceeded.

When some vessels are taken out of service, they have to be properly isolated and preserved.

An increase in the feedwater salinity can be compensated by increasing the feed pressure up to the maximum. If further pressure increase is not possible, than a lowered permeate flow and system recovery has to be accepted. A lower feedwater salinity allows to decrease the feed pressure and/or to increase the system recovery and/or to increase the permeate flow.

The adjustment of the permeate capacity to reduced needs is normally accomplished by sufficiently dimensioned permeate tanks.

Big plants are split up into a number of identical trains. Then the number of trains in service can be adjusted to the needs.

2.6 Record Keeping

2.6.1 Introduction

In order to be able to follow the performance of the RO unit, it is necessary that all relevant data are collected, recorded and kept on file. Apart from keeping track of the performance, the logsheets are also valuable tools for troubleshooting, and are needed in the cases of warranty claims.

This chapter is for general guidance only and must not be used in place of the operating manual for a particular plant. Site-dependent factors prevent specific recommendations for all record keeping. Thus, only the more general record keeping is covered here.

2.6.2 Start-Up Report

• Provide a complete description of the RO plant. This can be done using a flow diagram and equipment, instrumentation, and material list to show water source, pretreatment system, RO configuration and posttreatment system.
• Give results of checking according to check list (Section 2.2.2, Pre-Start-up Check and Commissioning Audit).
• Provide calibration curves of all gauges and meters based on manufacturers' recommendations.
• Record initial performance of RO and pretreatment system as provided below.

2.6.3 RO Operating Data

The following data must be recorded and logged into an appropriate logsheet at least once per shift, unless otherwise stated (see Table 2.1 for an example).

• Date, time and hours of operation.
• Pressure drop per filter cartridge and per stage.
• Feed, permeate and concentrate pressure of each stage.
• Permeate and concentrate flows of each stage.
• Conductivity of the feed, permeate, and concentrate streams for each stage. Test permeate conductivity of each pressure vessel weekly.
• TDS of feed, permeate and concentrate streams for each stage. The TDS is calculated from the water analysis. It can also be calculated from the conductivity (at 25°C) EC25 and an appropriate K factor: TDS = K EC25. (The K factor has to be determined for each specific stream. Typical K factors are shown in Table 2.2.)
• pH of the feed, permeate and concentrate streams.
• Silt Density Index (SDI) or turbidity of the RO feed stream, or both.
• Water temperature of the feed stream.
• Langelier Saturation Index (LSI) of the concentrate stream from the last stage (for concentrate streams ˂ 10,000 mg/L TDS).
• Stiff and Davis Stability Index (S&DSI) of the concentrate stream from the last stage (for concentrate streams > 10,000 mg/L).
• Calibration of all gauges and meters based on manufacturer’s recommendations as to method and frequency but no less frequent than once every three months.
• Any unusual incidents, for example, upsets in SDI, pH, and pressure and shut-downs.
• Complete water analysis of the feed, permeate and concentrate streams and the raw water at start-up and every week thereafter.
• The water analysis shall include:
  • Calcium
  • Magnesium
  • Sodium
  • Potassium
  • Strontium
  • Barium
  • Iron (total, dissolved and ferrous)
  • Aluminium (total and dissolved)
  • Bicarbonate
  • Sulfate
  • Chloride
  • Nitrate
  • Fluoride
  • Phosphate (total)
  • Silica (dissolved)
  • Total dissolved solids
  • Conductivity
  • pH
  • TOC

Factors for estimating TDS from conductivity

2.6.4 Pretreatment Operating Data

Since the RO system performance depends largely on the proper operation of the pretreatment, the operating characteristics of the pretreatment equipment should be recorded. Specific recommendations for all record keeping cannot be given, because pretreatment is site-dependent. Typically, the following items must be recorded:

• Total residual chlorine concentration in the RO feed (daily – unless known to be completely absent).
• Discharge pressure of any well or booster pumps (twice a day).
• Pressure drop of all filters (twice a day).
• Consumption of acid and any other chemicals (daily–if used).
• Calibration of all gauges and meters based on manufacturers' recommendations as to method and frequency but no less frequent than once every 3 months.
• Any unusual incidents, for example, upsets and shut-downs as they occur.

2.6.5 Maintenance Log

• Record routine maintenance.
• Record mechanical failures and replacements.
• Record any change of membrane element locations with element serial numbers.
• Record replacements or additions of RO devices.
• Record calibration of all gauges and meters.
• Record replacement or additions of pretreatment equipment, for example cartridge filters and include date,
• Brand name and nominal rating.
• Record all cleanings of RO membranes. Include date, duration of cleaning, cleaning agent(s) and concentration, solution pH, temperature during cleaning, flowrate and pressure (for cleaning procedures see Section 3.3).

3. Cleaning

3.1 Cleaning Requirements

In normal operation, the membrane in reverse osmosis elements can become fouled by mineral scale, biological matter, colloidal particles and insoluble organic constituents. Deposits build up on the membrane surfaces during operation until they cause loss in normalized permeate flow, loss of normalized salt rejection, or both.

Elements should be cleaned when one or more of the below mentioned parameters are applicable:

• The normalized permeate flow drops 10%
• The normalized salt passage increases 5-10%
• The normalized pressure drop (feed pressure minus concentrate pressure) increases 10-15%

If you wait too long, cleaning may not restore the membrane element performance successfully. In addition, the time between cleanings becomes shorter as the membrane elements will foul or scale more rapidly.

Differential Pressure (ΔP) should be measured and recorded across each stage of the array of pressure vessels. If the feed channels within the element become plugged, the ΔP will increase. It should be noted that the permeate flux will drop if feedwater temperature decreases. This is normal and does not indicate membrane fouling.

A malfunction in the pretreatment, pressure control, or increase in recovery can result in reduced product water output or an increase in salt passage. If a problem is observed, these causes should be considered first. The element(s) may not require cleaning.

3.2 Chemical Handling suggestions

When using any chemical indicated here or in previous or subsequent sections, follow accepted safety practices. Consult the chemical manufacturer for detailed information about safety, handling and disposal.

When preparing cleaning solutions, ensure that all chemicals are dissolved and well mixed before circulating the solutions through the elements.

It is recommended the elements be flushed with good-quality chlorine-free water (20°C minimum temperature) after cleaning. Permeate water or deionized water is recommended. Care should be taken to operate initially at reduced flow and pressure to flush the bulk of the cleaning solution from the elements before resuming normal operating pressures and flows. Despite this precaution, cleaning chemicals will be present on the permeate side following cleaning. Therefore, the permeate must be diverted to drain for at least 30 minutes or until the water is clear when starting up after cleaning.

During recirculation of cleaning solutions, there are temperature and pH limits. Please refer to Table 3.1.

For elements greater than 6 inches in diameter, the flow direction during cleaning must be the same as during normal operation to prevent element telescoping because the vessel thrust ring is installed only on the reject end of the vessel. This is also recommended for smaller elements. Equipment for cleaning is illustrated below.

Table 3.1 pH range and temperature limits during cleaning

3.3 Cleaning Equipment

The equipment for cleaning is shown in the cleaning system flow diagram (Figure 3.1). The pH of cleaning solutions used with SpiroPure® Elements can be in the range of 1-13, and therefore, non-corroding materials of construction should be used in the cleaning system.

Figure 3.1 Cleaning system flow diagram

Major cleaning system components are:

• RO Cleaning Tank: This tank needs to be sized properly to accommodate the displacement of water in the hose, piping, and pressure vessels. The tank should be designed to allow 100 % drainage, easy access for chemical introduction and mixing, a recirculation line from the RO Cleaning Pump, proper venting, overflow, and a return line located near the bottom to minimize foam formation when using a surfactant.
• RO Cleaning Pump: This pump needs to be sized to develop the proper crossflow velocity to scrub the membrane clean. The cleaning rate for a 8-inch diameter vessel is 30 to 40 gpm and for a 4-inch diameter vessel is 8 to 10 gpm. The maximum recommended pressure is 60 psi to minimize the production of permeate during cleaning and reduce the convective redeposition of foulant back on to the membrane surface.
• RO Cleaning Cartridge Filter: Normally 5 to 10-micron and is designed to remove foulants that have been displaced from the cleaning process.
• RO Tank Heater or Cooler: The optimal temperature for cleaning is 35 to 45^oC. One cannot forget that heat is generated and imparted by the RO Cleaning Pump during recirculation.
• RO Tank Mixer: This is recommended to get optimal mixing of chemical, though some designers rely solely on the slow introduction of chemical while maintaining a recirculation through the RO Cleaning Pump back to the tank.
• Instrumentation: Cleaning system instrumentation should be included to monitor flow, temperature, pressure, and tank level.
• Sample Points: Sample valves should be located to allow pH and TDS measurements off the RO Cleaning Pump discharge and the concentrate side recirculation return line.
• Permeate Return Line: A small amount of the cleaning solution can permeate through the membranes and so a permeate side return line is recommended.

The mixing tank should be constructed of polypropylene or fiberglass-reinforced plastic (FRP). The tank should be provided with a removable cover and a temperature gauge. The cleaning procedure is more effective when performed at a warm temperature, and it is recommended that the solution be maintained according to the pH and temperature guidelines listed in Table 3.1. It is not recommended to use a cleaning temperature below 20°C because of the very slow chemical kinetics at low temperatures. In addition, chemicals such as sodium lauryl sulfate might precipitate at low temperatures. Cooling may also be required in certain geographic regions, so both heating/cooling requirements must be considered during the design. A rough rule of thumb in sizing a cleaning tank is to use approximately the empty pressure vessels volume and then add the volume of the feed and return hoses or pipes.

The cleaning pump should be sized for the flows and pressures given in Table 3.2, making allowances for pressure loss in the piping and across the cartridge filter. The pump should be constructed of 316 SS or nonmetallic composite polyesters.

Table 3.2 Recommeded feed flowrate per peressure vessel during high flowrate recycle

1. Dependent on number of elements in pressure vessel.
2. 4-inch full-fit elements should be cleaned at 12 – 14 gpm (2.7 – 3.2 m3/h).
3. For full-fit and 440 ft2 area elements.

Appropriate valves, flow meters and pressure gauges should be installed to adequately control the flow. Service lines may be either hard-piped or hoses. In either case, the flowrate should be a moderate 10 ft/s (3 m/s) or less.

3.4 Cleaning Steps

There are six steps in the cleaning of elements:

1. Make up cleaning solution.
2. Low-flow pumping. Pump mixed, preheated cleaning solution to the vessel at conditions of low flowrate (about half of that shown in Table 3.2) and low pressure to displace the process water. Use only enough pressure to compensate for the pressure drop from feed to concentrate. The pressure should below enough that essentially no or little permeate is produced. A low pressure minimizes redeposition of dirt on the membrane. Dump the concentrate, as necessary, to prevent dilution of the cleaning solution.
3. Recycle. After the process water is displaced, cleaning solution will be present in the concentrate stream. Then recycle the concentrate and permeate to the cleaning solution tank and allow the temperature to stabilize. Measure the pH of the solution and adjust the pH if needed.
4. Soak. Turn the pump off and allow the elements to soak. Sometimes a soak period of about 1 hour is sufficient. For difficult fouling an extended soak period is beneficial; soak the elements overnight for 10-15 hours. To maintain a high temperature during an extended soak period, use a slow recirculation rate (about 10% of that shown in Table 3.2).
5. High-flow pumping. Feed the cleaning solution at the rates shown in Table 36 for 30-60 minutes. The high flowrate flushes out the foulants removed from the membrane surface by the cleaning. If the elements are heavily fouled, a flowrate which is 50% higher than shown in Table 36 may aid cleaning. At higher flowrates, excessive pressure drop may be a problem. The maximum recommended pressure drops are 15 psi per element or 50 psi per multi-element vessel, whichever value is more limiting. Please note that the 15 psi per element or the 50 psi per multi-element vessel should NOT be used as a cleaning criteria. Cleaning is recommended when the pressure drop increases 15%. Pressure drop above 50 psi in a single stage may cause significant membrane damage.
6. Pre- filtered raw water or feedwater should be avoided as its components may react with the cleaning solution: precipitation of foulants may occur in the membrane elements. The minimum flush-out temperature is 20°C.

3.5 Cleaning Chemicals

Table 3.3 lists suitable cleaning chemicals. Acid cleaners and alkaline cleaners are the standard cleaning chemicals. The acid cleaners are used to remove inorganic precipitates including iron, while the alkaline cleaners are used to remove organic fouling including biological matter. Sulfuric acid should not be used for cleaning because of the risk of calcium sulfate precipitation. Reverse osmosis permeate or deionized water should be used for the preparation of cleaning solutions.

The temperatures and pH listed in Table 3.1 are applicable for SpiroPure® LP, ULP, ZLP, SWRO, Fouling resistence RO elements.

Notes:

1. (W) denotes weight percent of active ingredient.
2. Foulant chemical symbols in order used: CaCO3 is calcium carbonate; CaSO4 is calcium sulfate; BaSO4 is barium sulfate.
3. Cleaning chemical symbols in order used: NaOH is sodium hydroxide; Na4EDTA is the tetra-sodium salt of ethylene diamine tetraacetic acid; Na-DSS is sodium salt of dodecylsulfate; Sodium Laurel Sulfate; HCI is hydrochloric acid (Muratic Acid); H3PO4 is phosphoric acid; NH2SO3H is sulfamic acid; Na2S2O4 is sodium hydrosulfite.
4. For effective sulfate scale cleaning, the condition must be caught and treated early. Adding NaCl to the cleaning solution of NaOH and Na4EDTA may help as sulfate solubility increases with increasing salinity. Successful cleaning of sulfate scales older than 1 week is doubtful.
5. Citric Acid is another cleaning alternative for metal oxides and calcium carbonate scale. It is less effective. It may contribute to biofouling especially when it is not properly rinsed out.

Table 3.3 Recommended Cleaning Solutions

3.6 Cleaning Tips

1. It is strongly recommended to clean the stages of the RO or NF system separately. This is to avoid having the removed foulant from stage 1 pushed into the 2nd stage resulting in minimal performance improvement from the cleaning. If the system consists of 3 stages, stage 2 and stage 3 should also be cleaned separately. For multi-stage systems, while each stage should be cleaned separately, the flushing and soaking operations may be done simultaneously in all stages. Fresh cleaning solution needs to be prepared when the cleaning solution becomes turbid and/or discolored. High-flow recirculation, however, should be carried out separately for each stage, so the flowrate is not too low in the first stage or too high in the last. This can be accomplished either by using one cleaning pump and operating one stage at a time, or by using a separate cleaning pump for each stage.
2. The fouling or scaling of elements typically consists of a combination of foulants and scalants, for instance a mixture of organic fouling, colloidal fouling and biofouling. Therefore, it is very critical that the first cleaning step is wisely chosen. SpiroPure® strongly recommends alkaline cleaning as the first cleaning step. Acid cleaning should only be applied as the first cleaning step if it is known that only calcium carbonate or iron oxide/hydroxide is present on the membrane elements.
3. Acid cleaners typically react with silica, organics (for instance humic acids) and biofilm present on the membrane surface which may cause a further decline of the membrane performance. Sometimes, an alkaline cleaning may restore this decline that was caused by the acid cleaner, but often an extreme cleaning will be necessary. An extreme cleaning is carried out at pH and temperature conditions that are outside the membrane manufacturer’s guidelines or by using cleaning chemicals that are not compatible with the membrane elements. An extreme cleaning should only be carried out as a last resort as it can result in membrane damage.
4. If the RO system suffers from colloidal, organic fouling or biofouling in combination with calcium carbonate, then a two-step cleaning program will be needed: alkaline cleaning followed by an acid cleaning. The acid cleaning may be performed when the alkaline cleaning has effectively removed the organic fouling, colloidal fouling and biofouling.
5. Always measure the pH during cleaning. If the pH increases more than 0.5 pH units during acid cleaning, more acid needs to be added. If the pH decreases more than 0.5 pH units during alkaline cleaning, more caustic needs to be added.
6. Long soak times. It is possible for the solution to be fully saturated and the foulants can precipitate back onto the membrane surface. In addition, the temperature will drop during this period, therefore the soaking becomes less effective. It is recommended to circulate the solution regularly in order to maintain the temperature (temperature should not drop more than 5°C) and add chemicals if the pH needs to be adjusted.
7. Turbid or strong colored cleaning solutions should be replaced. The cleaning is repeated with a fresh cleaning solution.
8. If the system has to be shut down for more than 24 hours, the elements should be stored in 1% w/w sodium metabisulfite solution.
9. Effect of pH on foulant removal. In addition to applying the correct cleaning sequence (alkaline cleaning step first), selecting the correct pH is very critical for optimal foulant removal. If foulant is not successfully removed, the membrane system performance will decline faster as it is easier for the foulant to deposit on the membrane surface area. The time between cleanings will become shorter, resulting in shorter membrane element life and higher operating and maintenance costs. Most effective cleaning allows longer system operating time between cleanings and results in the lowest operating costs. Calcium carbonate is best removed by cleaning with hydrochloric acid at pH 1-2. Biofouling is best removed by cleaning at pH 12.

4. Membrane Element Storage and shipping

4.1 Membrane Element Preservation

Most of SpiroPure® membrane elements are dry elements and a small number are wet membrane element that have been tested with storage solution. These tested wet membrane elements are stored in standard storage solution containing a buffered 1wt% food-grade sodium pyrosulfite (SMBS), which can prevent microbial growth during the storage and shipping of elements. After sampling and testing by the quality control department of SpiroPure®, the wet membrane element is soaked in the storage solution for 1 hour, removed and drained, and sealed with a plastic bag to isolate the air. The SpiroPure® dry membrane element is not individually evaluated, only in a single layer of plastic packaging, and does not require any storage solution. Before opening and using, the package must be sealed in good condition.

Any SpiroPure® membrane element that has been used and removed from the pressure vessel for storage or shipping must be preserved in a preservation solution as follows:

1. Use the standard storage solution of 1% food-grade SMBS (not cobalt-activated) in good-quality water (preferably reverse osmosis (RO) or nanofiltration (NF) permeate).
2. Soak the element for 1 h in the solution; keep it in a vertical position so that the entrapped air can escape. Allow it to drip out, and seal it into an oxygen barrier plastic bag. We recommend reusing the original bag or original spare bags available from SpiroPure® . Do not fill the plastic bag with the preservation solution-the moisture in the element is sufficient, and leaking bags might create a problem during transport.
3. Identify the element and the preservation solution on the outside of the bag.

4.2 Re-wetting of Dried Out Elements

Elements that have dried out after use may irreversibly lose water permeability. Re-wetting might be successful with one of the following methods:

1. Soak in 50/50% ethanol/water or propanol/water for 15 minutes.
2. Pressurize the element at 150 psi (10 bar) and close the permeate port for 30 minutes. Take care that the permeate port is reopened before the feed pressure is released. This procedure can be carried out while the elements are installed in a system. In this case, the pressure drop from the feed side to the concentrate side must not exceed 10 psi (0.7 bar) during high pressure operation with closed permeate port-otherwise the permeate backpressure near the concentrate end will become too high. Preferably, the permeate port is not completely closed but throttled to a value equal the concentrate pressure. Then there is no need for a special pressure drop limit.
3. Soak the element in 1% HCl or 4% HNO3 for 1-100 h. Immerse the element in a vertical position to allow the entrapped air to escape.

4.3 Storage

Please follow these guidelines for storage of SpiroPure® membrane element

1. Store inside a cool building or warehouse and not in direct sunlight.
2. Temperature limits: 25°F to 95°F (−4°C to +35°C). New dry elements will not be affected by temperatures below 25°F (−4°C). Elements stored in 1% SMBS will freeze below −4°C, but the membrane will not be damaged, provided the elements are thawed before loading and use.
3. Keep new elements in their original packaging.
4. Preserved elements should be visually inspected for biological growth 12 months after shipment and thereafter every three months. If the preservation solution appears to be not clear the element should be removed from the bag, soaked in a fresh preservation solution and repacked. Re-soak in fresh storage solution for 1 hour, drain and then re-seal packaging. Refer to Section 4.1.
5. In case no equipment for re-preservation (fresh solution, clean environment, bag sealing device) is available, the elements can be left in their original packaging for up to 18 months. When the elements are then loaded into the pressure vessels, they should be cleaned with an alkaline cleaner before the plant is started up.
6. The pH of the preservation solution must never drop below pH 3. In the absence of a buffer such as is used in the original preservative for wet Elements, a pH decrease can occur when bisulfite is oxidized to sulfuric acid. Therefore, the pH of the bisulfite preservation solution should be spot checked at least every 3 months. Re-preservation is mandatory when the pH is 3 or lower.
7. Wear protective gloves and sleeves to avoid prolonged contact with skin and sleeves when working with preservative.

4.4 Shipping

When SpiroPure® membrane elements have to be shipped, they must be preserved with a preservation solution according to Section 4.1.

Make sure that:

• The plastic bag does not leak.
• The element is properly identified.
• The preservation solution is correctly labelled.

We recommend using the original packaging with the original polystyrene foam cushions to protect the element from mechanical damage. Elements with non flush-cut product water tubes should be protected against damage to the product water tube ends.

The membrane elements will not be damaged by freezing temperatures during shipping, provided the elements are thawed before loading and use.

Three-year Proportional Limited Quality Assurance

Agreement for reverse osmosis membrane elements

The company provides users (hereinafter referred to as the buyer) with the following limited quality assurance regarding the materials, manufacturing and element performance of the roll reverse osmosis membrane elements they produce:

1． Material and manufacturing guarantee

The company guarantees that the reverse osmosis membrane elements it sells are free from defects in materials and manufacturing. In accordance with applicable compulsory laws and regulations, the company assumes guarantee obligations in terms of materials and manufacturing within 12 months from the date the buyer receives the product. Under the declared materials and manufacturing guarantees, the buyer's specific compensation requirements and the company's (including the organization in the process of transportation and sales) the buyer's guarantee obligations are limited. In the event of problems due to membrane element materials and manufacturing, and after confirmation by the company, the company is responsible for repair or replacement within the delivery period specified in the original sales contract. The cost of replacing the membrane element is the responsibility of the buyer. In order to avoid misunderstanding, the company reiterates that this material and manufacturing warranty do not apply to damage to membrane elements caused by failure to follow the requirements of the company's operation and operation manual, or operation under good conditions.

2． Initial performance guarantee

According to the test conditions specified in the company's product manual, the membrane element has the initial minimum water production and minimum desalination rate specified in the product manual. If any membrane element does not reach the required initial performance, the buyer must notify the company of the relevant defects timely. After confirming the performance defects, the company will decide whether to repair or replace the new elements. In this case, the company will bear the shipping costs.

3． Performance guarantee

During the warranty period (see "4. Warranty Period"), under the standard test conditions specified in the company's product sample manual, the company provides the following performance guarantee for membrane elements:

• its salt transmission rate does not exceed three times the maximum salt transmission value;
• Its water production is not less than 70% of the minimum water production value specified in the product brochure.

4． Warranty period

The company guarantees the performance of the membrane element for three years, and the starting time of the three years is subject to the following time points ("guarantee period"): date of commissioning of the reverse osmosis membrane elements, or six months after shipment from the membrane element manufacturer (whichever comes first).

5． Warranty conditions

If any of the conditions listed below cannot be satisfied, the warranty terms guaranteed by the company in the above section are invalid.

• The design of the membrane system must meet the requirements of the engineering conditions and the requirements recommended by the company's operation and operating instructions. The operating conditions of the operation must not exceed the engineering conditions defined in the company's product brochure.
• The design parameters of the membrane system, including the arrangement and recovery of membrane elements, and the pressure vessels on which the instruments and membrane elements are placed must comply with reliable engineering and technical requirements. SpiroPure® reserves the right to review the system design. Regardless of whether SpiroPure® exercises the right to review the system design, the company does not assume compensation for damage caused by system design.
• The inlet water temperature must be below 45°C;
• Influent SDI (15min, 30psi) must be less than 5.0; feed water turbidity ≤ 1.0NTU;
• Membrane elements must not be contaminated by sediments, suspended matter, and any organic matter, inorganic scales, chemicals or organisms that affect membrane performance; the incoming water must not contain oil, grease, or other organic substances that are harmful to the membrane elements And inorganic substances; must not contain ozone, active chlorine and other strong oxidants that have proven to be harmful to the operation of membrane elements;
• Do not use non-ionic surfactants or cationic active agents, and coagulants for chemical cleaning, and do not allow membrane elements to come into contact with them;
• The membrane element shall not be subjected to any physical shock during startup, normal operation and cleaning, such as damage caused by load shock, vibration, pulsation, air or water hammer. Back pressure at any time (reverse osmosis water production side static pressure minus concentrated water side static pressure) must not exceed 0.7kg / cm2 (10psi);
• When the system performance (water production, desalination rate or pressure loss) decreases under standard conditions, corresponding measures should be taken in a timely manner;
• The buyer is responsible for providing reasonable system operation and maintenance manuals to the end user, and shall provide training for operators and managers to ensure that the user has the ability to perform cleaning and other system performance recovery and disposal and general troubleshooting;
• The buyer must keep all operation records of the membrane system after it starts operation, including fault handling, daily maintenance management, etc., and organize these data in a standard format to facilitate analysis and search for the cause of the fault. When the buyer submits a compensation claim to the company in accordance with the terms of the warranty, he must also provide the company's operation record data;
• Before installation and use, the membrane elements must be stored in their original packaging, avoiding direct sunlight, and the ambient air temperature during storage must not be higher than 35°C (95°F) or lower than 0°C (32°F).

6． Warranty liability

• Under this quality guarantee, the buyer's specific compensation requirements and the company's (including the organization in the process of transportation and sales) guarantee obligations are limited. If any membrane element does not meet the required guaranteed performance, the company will determine what measures to take, such as repairing, restoring, replacing or adding membrane elements, etc., and discount the appropriate price at the current selling price (the unfulfilled warranty period). After replacing the element, the price does not include the various costs such as customs duties, VAT, and installation.
• The company's warranty liability is limited to the total number of repairs or replacements that is less than or equal to the number of elements that were originally installed with performance issues. The buyer shall be responsible for the expenses incurred in the replacement of the membrane element.
• The company may, at its discretion, (i) send its engineers to the site for testing, or (ii) require the buyer to return the suspected defective membrane element to the company for inspection at the expense of the other party. If the test results show that: 1 the degradation of the membrane element is caused by a violation of the performance guarantee, or 2 the operating performance of the membrane element meets the performance guarantee, the buyer will need to pay the company the inspection fee, and in addition The company pays the costs related to the testing and transportation of returned membrane elements.

7． Additional information

• When a scale inhibitor is required for the membrane system, please check the compatibility with the manufacturer.
• Permeate must be discharged during the first hour of operation.
• When using formalin as a fungicide, the membrane element must operate normally for at least 24 hours. If the membrane is exposed to formalin during this time, it will result in a significant reduction in water production.
• Before sending to our company a membrane element that requires quality inspection, please contact our customer representative.

8． Warranty statement

Other than the above, no other warranty is provided. Any commercial, implied warranties, and warranties applicable to a particular purpose are excluded from the warranty. The company is not responsible for any damage caused by the buyer's intention or negligence, or damage caused by other third parties. The expiration, termination, or cancellation of this warranty does not affect all limitations on liability. Any failure or refusal to completely provide the company with the use and operating parameters of the membrane element will invalidate all warranties other than material and manufacturing guarantees.