ADD.:No.6,Lutian RD,Lu Valley,Changsha Hunan,China
After Sales Service
1. Membrane Installation and System Operating Maintenance -----To Improve the Utilization Efficiency and extend the working life
1.1 Installation and Disassembling of Membrane Element(Please see the below image)
Installation: The concentrated water V-groove seal on the inlet side is opposite to the feed water inlet direction. Membrane element force direction is same as feed water, and please kindly use the professional tool to push the membrane element into housing.
Disassembling: When users remove the membrane element, the direction should be consistent with install process. Installer need to stably push the membrane element from the side of inflow. Please notice the connection of central connector, adapter and central tube of element. Avoid installing or disassembling forcefully. Make sure to use the water or glycerin as lubricant.
The inner length of membrane element’s pressure vessel has a little surplus size, which enables membrane element length to change in a small range. However, the surplus size may result in a gap between the adapter and membrane element after installation. Membrane element will slide back and forth in the pressure vessels during the process of boot and shut down the system because of the gap, which will accelerate the damage of sealing element. Besides, pressure vessels will extend when pressure rises. In extreme condition, the component closer to inflow water side and concentrated water maybe drop from end-plate, which will cause more serious leakage. Installers should adjust membrane axial clearance of membrane element in pressure vessels to decrease the axis motion, thus to ensure the firm seal between the inner joint and the front and the elements ends.
1.2 Operation of Membrane Element System at the First Time
(1). Before the system booting, operator should inspect all the notice in operation checklist in the situation that raw water did not enter the membrane element, which including completely wash the pre-treatment section to prevent the impurities and other contaminants from entering the high pressure pump and membrane element, check the effluent SDI15 value of pre-treatment, residual chlorine of inflow water should lower than 0.1mg/L, inflow water cannot have oxidizer, etc.
(2). Operator should fully ensure all the setting of valves is correct after careful inspection. Drain valve, inlet valve, concentrate valve of membrane system should be totally switched on. Pre-treatment system should use the low pressure and low flow expels the air in the membrane element and pressure vessel. The flushing pressure should control between 2.5 to 3 bars.
(3).Five hours of cleaning in low working pressure or one to two hours of flush recommended, when the wet or dry type of new membranes installed. One to two hours of flush again recommended after soaking in 1-2 hours. The wet membrane system usually will reach the stable performance after 12 hours continuously working. The dry membrane system may need around 48 hours or longer time working to reach the stable performance .
(4). Open the inlet valve slowly after started the high pressure pump. Evenly raise the flux of concentrate to the designed value. The rate of pressure rise should lower than 0.7bar per second.
(5). Inspect the quality of production water after one hour continuously operating of membrane system. Record the initial data of operating system. Then switch on the qualified water valve and switch off the drain off valve to deliver the water to following device.
1.3 Notice of Membrane System Halt
Membrane system stop running for 15-30 days is short-term halt. Operator should wash the membrane system and completely release the air per each five days. Switch off the related inlet valves and drain valve after washing. If the raw water quality is bad, please use the permeated flow of RO or NF system cleans the membrane system.
If membrane system needs to halt more than 30 days and membrane element still have to remain in pressure vessel, membrane system must wash with chemical cleaning after its stop. Then recycle wash the membrane system with the 1% sodium bisulfite of disinfection and fill the membrane system to achieve the purpose of long term storage. If water temperature is higher than 27℃, bactericide needs to change per each 15 days. When the membrane system start to work next time, please use the low pressure and high flux permeated flow clean the membrane system at least one hour till the permeated flow is to be the standard of qualified water.
1.4 The Cleaning of Membrane System
(1). Standard of Cleaning
The film of membrane element will be contaminated by inorganic salt, microbial, colloidal solid and not soluble organics after a period of running. These contaminants are deposited on the surface of membrane film, which cause the standard flux rate and salt rejection rate decline or even deteriorate. Membrane system needs to chemical clean when the following conditions occurrence:
a. Standardization water production permeate flux is lowered than 10-15%.
b. The difference of system pressure between inflow water and concentrated water reach the 1.5 times of initial value.
c. Standard salt permeate rate increase more than 10-15%. (RO series is subject to NaCl solution, NF series is subject to MgSO4 solution)
The choosing of cleaning agents will be determined by quality of raw water. The high hardness of water is easy to scale, which usually need to clean through acidic cleaning agents. However, the high content of organic can cause contamination of organic, membrane element need to clean through alkaline cleaning agents. When the membrane system mainly contaminated by the salt scaling, it needs acid pickling first, then alkali washing. When the membrane system is mainly caused by organic pollution, following recommendation is necessary: alkali cleaning first, then acid picking, alkali washing again.
(2). Process of Cleaning
Related cleaning solution should be prepared with permeated flow. Firstly, open or close relevant pipes to form a recycle cleaning pipe. Then, operate the cleaning pump, pour the cleaning solution into pressure vessel of membrane element. The circulation cleaning starts to work. It usually takes 1 - 2 hours for once cleaning. Membrane systems can also be soaking first then cleaning, if it is contaminated terribly. Please notice the flow changes of permeated flow and concentration.
When the pH value changes 0.5, operator should add cleaning agents. Membrane system should be washed with permeated flow after first cleaning. Then re-clean with another kind of cleaning agent. After these processes, membrane system need to be washed with low pressure water first, then gradually exhausting to boost the pressure until the permeated flow is qualified.
If membrane element blocked up in a serious condition or it don’t have obvious recovery for flow after cleaning, pour the cleaning agent again to the pressure vessels of membrane element and then soaking the membrane element for 6 to 12 hours. Then membrane system can be cleaned again.
(3). The Use and Preparation of Cleaning Agent
Acid cleaner: 2% citric acid solution with pH ranges from 2-3 or 0.2% hydrochloric acid solution with pH ranges from 2-3.
Alkaline cleaner: 0.1% caustic soda solution and 0.025% Sodium Dodecyl Sulfonate (Na-SDS) with pH ranges from 11-12.
Membrane system should be cleaned with low pressure and high flux water. At the initial fiveminutes, circulation cleaning should be controlled with 1/3 of deigned flow rate. Then the flux should be adjusted the 2/3 of designed flux to full value in each ten minutes. Usually it needs at least one hour circulation cleaning.
(5) .Cleaning Limit of pH
Scaling, organic compounds and biological film can be cleaned with high efficiency, when the cleaning solution pH at 1 or 13. The cleaning solution temperature must be controlled to avoid damage for membrane elements. If the limit cleaning is necessary, contact the technical support of manufacturer for the guidance.
(6) . Cleaning Limit of Temperature
The regular chemical cleaning solution temperature should be controlled between 30 to 35 ℃. If limit cleaning is necessary, the solution temperature should be controlled within 25 ℃. The membranes system needs to avoid limit cleaning under too low temperature. The suggested cleaning temperature is between 20 to 25℃ to increase the cleaning efficiency.
2. Packing and Storage of Keensen Membrane Element
2.1 Majority of Keensen membrane element are dry type, wet type membranes also are available.
The wet membrane element should be stored in 1% food grade sodium bisulfite of standard protective liquid (When the temperatures lower than zero degrees celsius, the wet membranes also
need to protected by 10% of propylene glycol antifreeze). It is protected from microorganism breeding and contamination and frozen in the process of storage and transportation.
2.2 Precautions for Storage and Transportation
(1). The membrane elements shall be stored in a shadow place (within 5-35℃) out of direct sunlight.
(2). Forbidden the rough handing for membrane elements, such as throwing, dropping from high place, etc.
(3). Avoid the membrane element remain in upright for a long period.
(4). It is recommended to use the wet membrane elements within six months. When it is over than six month, the protection solution should be replaced.
(5). It is forbidden to add any of chemical agents has influence on membrane elements during storage and transportation process.
2.3 If users are against above rules, it probably does permanent damage to membrane elements.
3. Analysis and Suggestion for Common Bug of Membrane System
3.1 Analysis and Solution for Common Bug
|No.||Permeate Flow||Rejection Rate||Pressure Difference||The Cause of Bug||Solution|
|1||Decline||Rise||Unchanged||Membrane Flat Sheet Densification by Water Hammer||Replace Membrane Element; Improving Membrane System|
Improving the Pretreatment
|3||Decline||Keep||Rise||Microbial Contamination||Chemical Cleaning; Disinfection;Improving the Pretreatment|
|4||Decline||Decline||Rise||Scaling or Colloidal Contamination||Chemical Cleaning; Improving the Pretreatment|
|5||Rise||Decline||Unchanged||O-ring Leakage||Inspect or Replace the O-ring|
|6||Rise||Decline||Unchanged||Back Pressure or Oxidation||Replace Membrane Element|
3.2 Judgement for Common System Contamination
|No.||Type of Contamination||Change of Feed Water Pressure||Change of Pressure Difference||Change of Rejection Rate||Possible Fouling Position|
|1||Inorganic Salt Scaling||Rise||Rise||Rise||The Membrane Element in the end of Final Stage|
|2||Organic Contamination||Rise||Keep||Decline or Keep||All the Membrane Element|
|3||Fouling by Metallic Oxides||Rise Quickly||Rise Quickly||Rise Quickly||The Membrane Element in the front of First Stage|
|Rise Quickly||Rise Quickly||Rise Slowly||Anyone of Membrane Element in the front of Stage|
|5||Colloidal Contamination||Rise Slowly||Rise Slowly||Rise Slowly||The Membrane Element in the front of First Stage|
|6||Scaling Contamination||Rise||Rise||Rise||The Membrane Element in the Second Stage|
|7||Polymerization Silicon Deposits||Rise||Rise||Rise||The Membrane Element in the end of Final Stage|