As a common bactericide carrier in drinking water purification, water purification tablets primarily function by leveraging their bactericidal active ingredients to rapidly eliminate pathogenic microorganisms (such as bacteria, viruses, and protozoa) in water.
Additionally, certain types can assist in removing small amounts of impurities, ultimately bringing non-potable water up to temporary drinking standards. Their working principle and process can be broken down into three key stages: “Ingredient Release → Targeted Bactericidal Action → Safety Waiting Period”. The specific mechanisms of operation are as follows:
I. Core Mechanism: Precisely Damaging Microbial Structures via Bactericidal Active Ingredients
The effectiveness of water purification tablets depends entirely on their bactericidal components.While the mechanisms of action vary slightly among different ingredients, the ultimate goal is to destroy the critical structural components essential for microbial survival, which inhibits their reproduction and eliminates their pathogenicity.Currently, the active ingredients in mainstream water purification tablets fall mainly into two categories:
1. Chlorine-Containing Water Purification Tablets (Most Commonly Used, e.g., Chlorine Dioxide, Sodium Hypochlorite)
Step 1: Upon dissolving in water, the active ingredients decompose rapidly, releasing “chlorine free radicals” or “hypochlorite ions,” which have strong oxidizing properties.
Step 2: These oxidizing substances penetrate the cell membranes of bacteria and viruses (or the protein coats of viruses), damaging critical internal components. For instance, they oxidize the enzyme systems of bacteria (rendering them unable to metabolize) and destroy the nucleic acids (DNA/RNA) of viruses (preventing them from replicating).
Step 3: Ultimately, microorganisms are inactivated (killed) and can no longer cause infectious diseases such as diarrhea and dysentery.
Characteristics: Fast bactericidal speed (usually taking effect within 30 minutes to 1 hour), low cost, and effective against most common pathogenic bacteria (e.g., E. coli, Salmonella, and rotavirus). However, when there is a high organic matter content in water, a small amount of residual chlorine may be produced (evaporation should be allowed as per the instructions).
2. Silver-Containing Water Purification Tablets (Long-Term Bacteriostasis; Suitable for Stored Water)
The core of these tablets lies in the bacteriostatic effect of “silver ions” and they are often used for drinking water that requires long-term storage (e.g., outdoor camping; emergency water reserves):
Step 1: Silver ions released after dissolution adhere to the surfaces of microorganisms and enter their interiors through the cell membranes.
Step 2: Silver ions bind to the proteins and enzymes of microorganisms, causing denaturation (e.g., disabling the catalytic functions of enzymes) while disrupting the DNA replication abilities of bacteria.
Step 3: Not only do they kill existing microorganisms, but the residual silver ions can also maintain a bacteriostatic effect in water for several days, preventing the re-growth of bacteria during storage.
Characteristics: Excellent long-term bacteriostatic performance with no chlorine odor. However, their bactericidal speed is slower than that of chlorine-containing tablets (taking 1-2 hours). Additionally, the cost is higher, and their virus-killing effect is slightly weaker than that of chlorine-containing counterparts.
II. Key Factor: “Standardized Usage” to Ensure Effectiveness (Avoiding Inefficacy and Excessive Residues)
The effectiveness of water purification tablets relies not only on their ingredients but also on their “correct usage”.Improper dosage, dissolution methods, or waiting times may lead to incomplete bactericidal action or excessive residues.Specifically, three aspects require attention:
1. “Pretreatment”: Remove Visible Impurities to Enable Direct Contact Between the Bactericidal Ingredients and Microorganisms
The core function of water purification tablets is to “kill microorganisms”; however, they cannot remove visible impurities such as sediment and suspended solids from water.These impurities can encapsulate microorganisms, preventing the bactericidal ingredients from coming into contact with them and creating “bactericidal blind spots”.
Correct Operation: First, remove sediment and floating matter from the water through filtration (e.g., using gauze, a water filter jug screen, or even a clean piece of clothing). Next, add the water purification tablets. If the water is turbid, let it stand for 5-10 minutes to allow impurities to settle, then use the upper layer of clear water for treatment with the tablets.
2. Dosing “According to Dosage”: Precisely Add Tablets Based on Water Volume to Avoid “Insufficient Sterilization” or “Excessive Residues”
Different brands of water purification tablets have varying concentrations of active ingredients per tablet.It is essential to strictly match the water volume according to the instruction manual (e.g., “1 tablet for 1 liter of water,” “2 tablets for 5 liters of water”):
Insufficient Dosage: The concentration of bactericidal ingredients in the water is too low to completely kill all microorganisms, leaving a risk of infection after consumption.
Excessive Dosage: May lead to excessive residual chlorine (or silver ions). Consuming such water may result in a pungent chlorine odor, and long-term excessive intake of silver ions may cause skin pigmentation (though rare, it should be avoided).
3. Wait for “Sufficient Time”: Allow Bactericidal Ingredients to React Fully; Do Not Drink Prematurely
After adding water purification tablets, it is necessary to wait for the “contact time” specified in the instruction manual (usually 30 minutes to 2 hours).The reasons are as follows:
Bactericidal ingredients need time to diffuse throughout the water and react fully with microorganisms (especially in low-temperature environments, where the reaction speed slows down, requiring an appropriate extension of waiting time)..
Some chlorine-containing water purification tablets also require time for excess residual chlorine to evaporate (usually, after 30 minutes of waiting, residual chlorine levels will drop to within safe standards, leaving no obvious odor).
Common Misconception: Many people drink the water just a few minutes after adding the tablets. At this point, the bactericidal process is still incomplete, and the tablets are essentially “useless”.
III. Application Scenarios: Emergency “Temporary Purification” Not a Substitute for Long-Term Safe Water Supply
Water purification tablets are positioned for “emergency drinking water sterilization” and are suitable for the following scenarios:
During outdoor camping and hiking, they are for treating natural water sources such as streams and rivers.
After natural disasters (e.g., earthquakes, floods), when the tap water supply is interrupted, they are for treating stored rainwater and well water.
During field work, they are for meeting temporary drinking water needs when there is no stable and safe water source.
However, it should be noted that water purification tablets cannot replace long-term safe water supply systems.They cannot remove heavy metals (e.g., lead, mercury), or chemical pollutants (e.g., pesticide residues), or odors (e.g., the fishy smell produced by algae) from water, nor can they improve the taste of water (except for reducing chlorine odor).They can only address the core safety issue of “microbial contamination.”
IV. Conclusion
In summary, the working logic of water purification tablets is to “precisely kill pathogenic microorganisms using active ingredients”.To achieve their intended effect, they must be used in conjunction with standardized operations: “pretreating to remove impurities → accurately dosing → waiting for the reaction to complete”.Moreover, they are only applicable to the temporary purification of drinking water in emergency scenarios, with the core goal of ensuring the safety of “drinking without getting sick”.