Does reverse osmosis disinfectant water?

       In the fields of industrial water treatment, drinking water purification, and high-purity water preparation, reverse osmosis system, as the core separation technology, relies on effective control of microbial contamination for its stable operation. As a key chemical agent for ensuring water quality safety, reverse osmosis disinfectants achieve disinfection by disrupting the structure or metabolic processes of microbial cells. Their disinfection efficiency directly affects the service life of reverse osmosis membranes and the quality of effluent water. This article will systematically analyze the water disinfection ability of reverse osmosis disinfectants from three dimensions: mechanism of action, classification characteristics, and disinfection effectiveness.

1. The mechanism of action of reverse osmosis bactericides

      The disinfection function of reverse osmosis disinfectants is based on the dual effects of physical destruction and chemical inhibition of microorganisms. The core mechanism includes:

      1. Cell membrane penetration and protein denaturation

      Non oxidative fungicides (such as isothiazolinone and quaternary ammonium salts) penetrate microbial cell membranes through diffusion and react with thiol (- SH) or amino (- NH ₂) groups in proteins, causing changes in protein spatial structure and subsequently inactivating enzyme systems. For example, isothiazolinone can inhibit the electron transfer in the respiratory chain of microorganisms and block energy synthesis.

      2. Oxidative substances disrupt metabolism

      Oxidative fungicides (such as chlorine and hydrogen peroxide) attack microbial cell membrane lipids, DNA, and proteins by releasing reactive oxygen species (ROS). Hypochloric acid (HClO) generated by the hydrolysis of chlorine gas can penetrate the cell wall and undergo oxidation reactions with intracellular substances, leading to leakage of cellular contents. Hydrogen peroxide generates hydroxyl radicals (· OH) through the Fenton reaction, triggering a chain oxidation reaction.

      3. Genetic interference

      Ultraviolet fungicides use 254nm wavelength photons to disrupt the purine pyrimidine base pairing of microbial DNA, forming thymine dimers that hinder DNA replication and transcription. Although this method does not directly kill microorganisms, it can block their reproductive ability.

2. Classification and characteristics of reverse osmosis disinfectants

      According to their mechanism of action and chemical properties, reverse osmosis disinfectants can be divided into the following three categories, with significant differences in their disinfection characteristics:

      1. Oxidative fungicides

      Representative components: chlorine gas, sodium hypochlorite, hydrogen peroxide, ozone
Function characteristics:
       Broad spectrum bactericidal property, capable of quickly killing bacteria, viruses, and algae
      The reaction products may generate disinfection by-products such as trihalomethanes (THMs)
      Narrow applicable pH range (chlorine based agents are suitable for pH>; At 7 o'clock, the activity decreased
      Technical parameters:
      The usual dosage of chlorine gas is 0.5-2mg/L, and the contact time is ≥ 30min
      The concentration of hydrogen peroxide should be controlled below 0.2% to avoid membrane oxidation

      2. Non oxidizing fungicides

      Representative ingredients: isothiazolinone, DBNPA (2,2-dibromo-3-cyanopropanamide), glutaraldehyde
      Function characteristics:
      Durable antibacterial properties, capable of penetrating biofilms and peeling off sticky sludge
      Excellent compatibility with membrane materials, no oxidative damage
      Some components (such as DBNPA) decompose into harmless substances
      Technical parameters:
      The recommended concentration of isothiazolinone is 15-20mg/L, with a cycle time of 45-60min
      Glutaraldehyde needs to be controlled at pH 7-8 to maintain stability

      3. Compound fungicides

      Representative components: hydrogen peroxide+silver ions, chlorine+quaternary ammonium salts
      Function characteristics:
      Synergistic enhancement, complementary oxidative and non oxidative mechanisms
      Silver ions can persistently inhibit microbial regeneration
      Reduce the dosage of a single medication and minimize side effects
      Technical parameters:
      The silver content of the hydrogen peroxide/silver ion composite agent should be less than 0.1mg/L

      The pH range of chlorine/quaternary ammonium salt composite agent is extended to 5-9

3. Evaluation of disinfection effect of reverse osmosis bactericides

      The disinfection efficacy of reverse osmosis disinfectants needs to be comprehensively evaluated through multiple indicators:

      1. Microbial killing rate

      Under laboratory conditions, high-quality reverse osmosis disinfectants should have a killing rate of ≥ 99.9% against common water pathogens such as Escherichia coli and Pseudomonas aeruginosa. For example, at a concentration of 20mg/L, isothiazolinone can achieve complete inactivation of sulfate reducing bacteria with a contact time of 30 minutes.

      2. Biofilm stripping ability

      The stripping efficiency of non oxidizing fungicides on biofilms is a key indicator for evaluating their long-term effectiveness. DBNPA can peel off over 85% of mature biofilms after 2 hours of cyclic treatment at a concentration of 50mg/L.

      3. Membrane compatibility

      Verify the corrosiveness of the agent through membrane material contact tests. High quality reverse osmosis disinfectants should meet the following requirements:
The desalination rate of polyamide composite membrane decreases by ≤ 3% after contact
Change in water flux after contact with cellulose acetate membrane ≤ 10%

      4. Environmental safety

      Must comply with the restrictions on disinfection by-products in the "Sanitary Standards for Drinking Water" (GB 5749-2022). For example, the content of trichloromethane should be ≤ 0.06mg/L, and the total amount of halogenated acetic acid should be ≤ 0.08mg/L.

4. Optimization of application strategy for reverse osmosis bactericides

      To maximize disinfection effectiveness and reduce operating costs, it is necessary to optimize application strategies from the following dimensions:

      1. Staged processing

      In the pretreatment stage, oxidative fungicides are used to rapidly reduce microbial load, while non oxidative fungicides are used in the reverse osmosis unit to prevent membrane fouling. For example, sodium hypochlorite (1mg/L) is added after ultrafiltration, and isothiazolinone (10mg/L) is added before reverse osmosis.

      2. Dynamic concentration adjustment

      Adjust the concentration of the agent based on fluctuations in the incoming water quality. When SDI (Pollution Index)>5, the concentration of non oxidizing fungicides needs to be increased to 15-20mg/L.

      3. Combination use technology

      Adopting the alternating impact method of "oxidant+non oxidant" and switching the type of agent every 72 hours can delay the development of microbial resistance. For example, sodium hypochlorite is added on Mondays, Wednesdays, and Fridays, and DBNPA is added on Tuesdays, Thursdays, and Saturdays.

5. Conclusion: Reverse osmosis disinfectants - the technological shield for water disinfection

      Reverse osmosis disinfectants establish multiple lines of defense for water disinfection through precise chemical reactions and physical damage mechanisms. Its classification system covers three categories: oxidizing, non oxidizing, and composite, providing customized solutions for different water quality conditions and membrane material characteristics. The scientific evaluation system ensures a balance between disinfection efficiency and system safety, from microbial killing rate, biofilm stripping ability to membrane compatibility. In the future, with the development of nanomaterials and intelligent dosing technology, reverse osmosis disinfectants will evolve towards greater efficiency and environmental friendliness, continuously safeguarding the purity and safety of water resources.