Reverse osmosis membrane commonly used cleaning methods and pharmaceutical formulations, do you know what?

First, the pollutants of reverse osmosis membrane element

In normal operation for a period of time, reverse osmosis membrane elements will be in the feed water may exist in the suspended material or insoluble material pollution, these pollutants in the most common calcium carbonate scale, calcium sulfate scale, metal oxide scale, silicon deposits and organic or biological deposits.
The nature of the contaminants and the rate of contamination with the water supply conditions, the contamination is slowly developing, if you do not take early measures, the contamination will be in a relatively short period of time to damage the performance of the membrane element.
Regular testing of overall system performance is a good way to confirm that membrane element contamination has occurred, and that different contaminants can cause different levels of damage to membrane element performance. The table lists the effects of common contaminants on membrane performance.

The table corresponds to the common cleaning fluids listed below:

According to the site of the analysis of the situation can be based on the specific circumstances of the specific collocation.

Removal of contaminants

Removal of pollutants can be achieved through chemical cleaning and physical flushing, and sometimes by changing the operating conditions to achieve, as a general principle, when one of the following circumstances should be cleaned.
1, under normal pressure, such as water flow rate down to 10-15% of the normal value;
2, in order to maintain the normal flow of water, after the temperature correction of the feed water pressure increased by 10 ~ 15%;
3, the quality of the effluent water is reduced by 10～15%. Salt permeability increased by 10～15%;
4, the use of pressure increased by 10 ~ 15%;
5, RO between the sections of the pressure difference increases significantly (perhaps no instrumentation to monitor this sign);

Third, common pollutants and their removal methods

1, calcium carbonate scale
In the scale inhibitor addition system failure or acid addition system failure and lead to feed water pH rise, then calcium carbonate may be deposited. Calcium carbonate scale precipitation should be found as early as possible to prevent the growth of crystals on the membrane surface damage, such as early detection of calcium carbonate scale, can be used to reduce the feed water pH to 3.0 to 5.0 between the operation of the method of removal of 1 to 2 hours. For calcium carbonate scale that takes longer to settle, a citric acid cleaning solution should be used for cyclic cleaning or overnight immersion. Note: It should be ensured that the pH of any cleaning solution should not be lower than 2.0, the cup may cause damage to the RO membrane element, especially at higher temperatures should be more careful, the highest pH should not be higher than 11.0. check the use of ammonia to raise the pH, the use of sulfuric acid or hydrochloric acid to reduce the pH value.

2、Calcium sulfate scale
Sodium tripolyphosphate solution (see above table in sodium tripolyphosphate solution) is the best way to remove calcium sulfate scale from the surface of the reverse osmosis membrane.

3、Metal oxide scale
Calcium carbonate scale removal method described above can be used to easily remove the deposition of hydroxides (such as iron hydroxide).

4、Silicon scale
For silicon scale that is not symbiotic with metallization or organic matter, generally only through specialized cleaning methods to remove them.

5、Organic deposits
Organic deposits (such as microbial slime or mold) can be removed using the above table cleaning solution 3, in order to prevent repopulation, can be used to sterilize the solution in the system cycle, immersion, generally need a longer period of time immersion to be effective, such as reverse osmosis device out of service for three days, it is best to use disinfection treatment.

6, cleaning solution cleaning
Reverse osmosis membrane elements when it is recommended to use the cleaning solution listed in the table above. Determine the chemical analysis of the pollutants before cleaning is very important, a detailed analysis of the results of the analysis of the comparison, can ensure that the selection of the best cleaning agent and cleaning method, should be recorded each time the cleaning method and the cleaning effect obtained for the specific conditions of the water supply, to find out the best cleaning method to provide a basis. For inorganic pollutants recommended cleaning solution
1. for calcium sulfate and organic matter recommended cleaning solution
2. for severe organic contamination cleaning solutions are recommended.
3. all cleaning can be cleaned at a maximum temperature of 40 ℃ for 60 minutes, the amount of supplies required to each 100 gallons (379 liters) in the amount added to the preparation of cleaning solutions in proportion to the addition of pharmaceuticals and cleaning water, should be used without free chlorine reverse osmosis product water to prepare the solution and mix well. Cleaning will be cleaning solution at low pressure and high flow rate in the membrane of the high-pressure side of the cycle, this time the membrane element is still installed in the pressure vessel and the need to use a special cleaning device to complete the work.

Fourth, the general steps for cleaning reverse osmosis membrane elements

1, with a pump will be clean, no free chlorine reverse osmosis product water from the cleaning box (or the corresponding water source) into the pressure vessel and discharge a few minutes.
2, with clean water in the cleaning tank preparation cleaning solution.
3, the cleaning solution will be circulated in the pressure vessel for 1 hour or a predetermined period of time, for 8-inch or 8.5-inch pressure vessel, the flow rate of 35 ~ 40 gpm (133 ~ 151 l / min), for 6-inch pressure vessel flow rate of 15 ~ 20 gpm (57 ~ 76 l / min), for the 4-inch pressure vessel flow rate of 9 ~ 10 gpm (34 ~ 38 l / min), for the 4-inch pressure vessel flow rate of 9 ~ 10 gpm (34 ~ 38 l / min), for the 4-inch pressure vessel flow rate of 9 ~ 10 gpm (34 ~ 38 l / min). 38 liters / minute )
4、After the cleaning is completed, drain and rinse the tank, then fill the tank with clean water for the next rinse.
5, pump clean, free chlorine-free water from the cleaning tank (or the appropriate water source) into the pressure vessel and discharge for a few minutes.
6, after flushing the reverse osmosis system, in the discharge valve open state to run the reverse osmosis system until the product water is clean, no foam or no detergent (usually takes 15 ~ 30 minutes).


Fifth, reverse osmosis membrane pollution characteristics and treatment methods

1、Bacterial pollution
General characteristics: desalination rate may be reduced, the system pressure drop increased significantly, the system water production decreased significantly; cleaning method: pH 10, 2% sodium tripolyphosphate solution, 0.8% EDTA tetrasodium (serious replacement for 0.25% Na-DDBS), the temperature 40 ℃; 0.1% NaOH and 0.03% SDS, pH = 11.5.
2、Calcium sulfate pollution
General characteristics: desalination rate decreased significantly, the system pressure drop slightly or moderately increased, the system water production slightly reduced; cleaning method: pH 10, 2% sodium tripolyphosphate solution, 0.8% EDTA tetrasodium (serious replacement of 0.25% Na-DDBS), the temperature of 40 ℃; sometimes also available pH less than 10 NaOH aqueous solution cleaning.
3、Precipitation of organic matter
General characteristics: desalination rate may be reduced, the system pressure drop gradually increased, the system water production gradually decreased; cleaning method: pH 10, 2% sodium tripolyphosphate solution, 0.8% EDTA tetrasodium salt (replaced by 0.25% Na-DDBS), temperature 40 ℃.
4, oxide / hydroxide (iron, nickel, copper) pollution
General characteristics: desalination rate decreased significantly, the system pressure drop increased significantly, the system water production decreased significantly cleaning method: ammonia pH 4, 2% citric acid solution, temperature 40 ℃, sometimes can also be used pH2-3 (0.5%) of hydrochloric acid aqueous solution cleaning.
5, inorganic salt precipitate pollution
General characteristics: desalination rate decreased significantly, the system pressure drop increased, the system water production decreased slightly cleaning method: 2% citric acid solution, ammonia pH 4, temperature 40 ℃, can also be used pH2-3 (0.5%) of hydrochloric acid solution cleaning.
6, a variety of colloids (iron, organic matter and silica colloid) pollution
General characteristics: desalination rate will be slightly lower, the system pressure drop rose slightly, the system gradually reduced water production. Cleaning method: sulfuric acid pH 10, 0.2% sodium tripolyphosphate STTP solution, temperature 40 ℃; sometimes can also be used pH less than 10 NaOH water solution cleaning.

Six, reverse osmosis membrane cleaning several commonly used formulas
Cleaning formula one
1% -2% citric acid solution or 0.4% HCl solution, applicable to iron pollution and carbonate crystallization fouling;
Cleaning formula two
0.2% NaClO + 0.1% NaOH solution, suitable for cleaning by organic matter and active biological pollution caused by the membrane module;
Cleaning formula three
0.3% H2O2 + 0.3% NaOH solution, suitable for cleaning the contamination of the membrane module caused by glutamic acid fermentation solution;
Cleaning formula IV
1% formaldehyde solution, suitable for ultrafiltration of bacterial contamination;
Cleaning formula V
A 0.5% aqueous solution of HNO3, suitable for cleaning membrane modules fouled by lead phosphate during electrophoretic paint treatment (this cleaning must be carried out after other routine chemical cleaning.) .;
Cleaning formula VI
20% Na2CO3, 7% Na3PO4, 3% NaOH, 0.5% EDTA, mainly for membrane fouling caused by colloidal contaminants;
Cleaning formula VII
9% sodium dodecylbenzene sulfonate, 9% surfactant, 0.4% NaOH, 0.15 anhydrous sodium carbonate, 11% sodium phosphate, 10% sodium silicate, cleaning should pay attention to the control of pH, some membranes are not suitable for high pH cleaning solution cleaning, to be carefully selected, mainly used for cleaning oily wastewater caused by membrane contamination;
Cleaning formula eight
3% H3PO4, 0.5% disodium EDTA, 0.5% LBOW special cleaning agent, mainly used for cleaning protein and grease contaminants caused by pollution;
Cleaning formula IX
20% H2SO4, mainly used for the pollution caused by silicon scale crystallization.

RO membrane element is the most important part of the reverse osmosis equipment system, its daily maintenance of good and bad directly affects the quality of the system's effluent water, here for the reverse osmosis membrane cleaning method to be outlined, the system explains the reverse osmosis membrane in the operation of the pollutants that may occur and the corresponding cleaning methods.