This technical service document refers to the fungicide applicable to the disinfection and preservation of reverse osmosis membranes and nanofiltration membrane components by Combat Technology (Dalian) Co., LTD.Operators should familiarize themselves with the technical service document and general preservation procedures for polyamide and PVD membrane elements prior to preserving or disinfecting membrane elements.The operator should determine the type of material for the membrane elements in the system to ensure that the appropriate fungicide is used. Usually our products suitable for Dow Filmtec, Hydranautics, FluidSystems, TORAY, GE, CSM and other reverse osmosis membrane components

The following information is based on studies using generic chemicals. Combat-Tech does not certify the conformity of specific membrane materials.The membrane material provider is responsible for the suitability of the membrane products.

If you are unsure of the material type of the membrane element, please consult the technical staff of the membrane material provider for confirmation. 

Warning: Some of the fungicides listed below are harmful to humans.Please flush the system thoroughly to remove residual fungicides before the system is put into operation. Combat Technology accepts no responsibility for the wrongful use of the chemicals listed below. Full responsibility for safety rests with the operator who sterilizes or preserves the system.Consult with the chemical manufacturer for proper use and discharge of the chemicals listed below.

Combat DB 20

It is well known in the membrane industry that polyamide membrane elements have very limited tolerance to free chlorine-based oxidants.Therefore, in the case of RO/NF system for sterilization or to prevent microbial growth/contamination, other high safety chemicals can be selected. One of these chemicals is DBNPA (2,2-dibromo-3-azo-propanamide), which is a fast acting non-oxidizing fungicide.The use of low concentrations of Combat DB 20 can effectively control the growth of aerobic bacteria, anaerobic bacteria, fungi and algae.The structural formula of Combat DB 20 is

 Combat DB 20 is an advantageous fungicide because of its rapid decomposition into carbon dioxide, ammonium and bromine ions in aqueous environments.It can be safely discharged even in sensitive water bodies.It can be broken down by water, nucleophilic reactions, ultraviolet light, etc., at a rate depending on pH and temperature. The half-life of DBNPA is estimated to be 24 hours @pH7, 2.0 hours @pH8, 15 minutes @pH9. The vast majority of microbes are killed after 5-10 minutes of contact with  Combat DB 20.

Product: Combat DB 20 for RO/NF systems is a direct dosing solution.

Recommended usage

When the impact is added, it is recommended to add 30 minutes to 3 hours every 5days, with a concentration of 10-30mg/L of active ingredients.Impact injection can be performed using a chemical cleaning system during system operation or low pressure flushing.Even low pressure film on DBNPA removal rate estimate more than 98%, more than 99.5% for desalination membranes, and some sites may require discharge of RO/NF production water when dosing. For more than 100CFU/ml of bacterial colonies in the water, or has formed a biofilm of RO/NF system, it is recommended to use 30mg/L of active ingredients for 3 hours.If the water produced is used for drinking water, the water produced during the addition should be discharged.

For continuous addition, 0.5-2 mg/L DBNPA active ingredient should be added.Continuous addition will be higher, please confirm whether to use this method according to the field situation.

Reducing agents will passivate  Combat DB 20, and if reducing agents (such as SBS) are present in the water,  Combat DB 20 concentrations should be higher.If running or washing water with sodium bisulfite (SBS), 1mg/LSBS need to add 1-1.3mg/L DBNPA passivation reaction, in addition to more concentration will have sterilization effect.

Although  Combat DB 20 is not oxidizing, when its concentration is 0.5-3mg/L, ORP value is about 400mv.(With 1mg/L residual chlorine, ORP reading is 700mv).

For chemical cleaning, it is recommended to circulate 30-50mg/L solution for 1hour.For severe biological contamination systems, alkali should be followed Wash.

Chemists have testing devices that can confirm the concentration of  Combat DB 20 and whether it has been completely flushed out of the system. 

Note:

 Combat DB 20 has corrosive to metal, plastic should be used when saving, and USES the dosing dosing pump. 

 Combat DB 20 toxicity is extremely low, but the supplier recommended in shock for overtime to produce water discharge.Drinking water applications, it only runs in the production of water use.

 Combat DB 20 is weak sensitization.Please read the notes according to the chemical safety manual (MSDS), proper use and storage.  Combat DB 20 is not suitable for longterm preservation of membrane element.

Important: the user should review all technical documents and communicate with suppliers, ensure the safety of  Combat DB 20 use note information is a new and more accurate.

Combat BV 14
Combat BV 14 as Isothiazolinone is another non-oxidized, broad-spectrum fungicide used to control aerobic, anaerobic, fungi and algae, among others.Its common form is:

Combat BV 14 bactericidal rate is much slower than DBNPA.Impact casting is generally 50-100mg/L, and the time is 4 hours.in Isothiazoline is more effective than DBNPA in influents with high organic content.The pH range should be 6-9 when used.It can be dosed continuously at low concentrations of 10-20mg/L during operation.Continuous dosing of isothiazoline is to prevent biological growth, should be used in the upstream of the system as far as possible, in order to control the microbial growth of the entire system process.It is recommended to wash contaminants, especially natural organic matter, from RO/NF systems before using isothiazoline.

Combat BV 14 can be used as a protective solution during system outage protection.For long-term protection, the concentration is 500-1000mg/L for no more than 6 months.

Note: thiazole moiety is sensitization.Please read the notes according to the chemical safety manual (MSDS), proper use and storage.

Combat SBS

Sodium bisulfite (SBS) inhibits microbial growth, especially against aerobic bacteria, when administered in higher concentrations.When SBS is added at a higher concentration, it has the biostatic property of inhibiting microbial growth, removing the oxygen needed by aerobic bacteria and creating an environment that is not conducive to the growth of bacteria, algae and fungi.When SBS is used to control microorganisms, 500mg/L sodium bisulfite solution is added for 30 -60 minutes every day.

A protective solution of 1.0% sodium bisulfite can be used for long-term storage.When the membrane element is protected in the membrane shell with 1%SBS solution, it needs to be checked once a month.If the pH value of the solution drops below 3 due to air oxidation, the protective solution must be replaced.

Combat GD 50

Glutaraldehyde solutions with concentrations of 0.1--1.0% are suitable for system disinfection or long-term storage use and should not come into contact with glutaraldehyde until at least 24 hours after the membrane element has been used.

Note: The use of formaldehyde or glutaraldehyde on new membrane elements may result in a 10-50% decrease in water flux, so contact with the above fungicides should not be allowed until at least 24 hours after the membrane elements have been in use. In any case, the first contact with formaldehyde or glutaraldehyde may cause a permanent decrease in water flux;Subsequent use of either fungicide will result in a temporary reduction in water flux, and the residual fungicide will need to be adequately rinsed until the system is back to its pre-application water flux.

Combat H2O2

Combat H2O2 as hydrogen peroxide can not use if the water contains hydrogen sulfide, or dissolved iron, manganese, etc.Hydrogen peroxide or a hydrogen peroxide solution containing peracetic acid can be used for disinfection.When using hydrogen peroxide for sterilization, it is necessary to ensure that the water in which the solution is prepared is free of transition metals (iron, manganese, etc.) to avoid catalytic oxidation and damage to the membrane elements.The concentration of hydrogen peroxide should not exceed 0.2% and the temperature should not exceed 25℃.Hydrogen peroxide should not be used as the protective liquid for the long -term shutdown of the membrane.

Combat THPS 75

Tetramethylpho sphine sulfate is in the membrane system of the rig and is used to control sulfate-reducing bacteria (SRBS).Tetramethylphosphine sulfate has been reported to be an environmentally frien dly fungicide that is effective against SRBS.

Phosphine tetramethylsulfate is stable under acidic abiotic conditions.It breaks down within a week when pH is higher than 8.The dissociation products are trihydroxymethyl phosphine (THP) and trihydroxymethyl phosphine oxide (THPO).The concentration is 50-100mg/L when shock dosing is added. 10 to 20 mg/L for continuous casting.600-1000mg/L when used as long-term protection fluid for RO/NF systems on drilling platforms. Dosing results in a 25-30% reduction in flux.Studies have shown that water flux can be restored by alkaline washing or certain surfactant washes.