Total Chlorine, Free Chlorine , Active Chlorine (Redox - Flipr), Potential Chloramines and Stabilizer
Different Types of Chlorine
Different forms of chlorine used in swimming pool treatment and their interaction are crucial for effective water disinfection. The following is a detailed overview of these forms and their interactions, as well as measurement and management methods:
- Free Chlorine: This is the sum of hypochlorous acid (HCIO) and hypochlorite ions (IOC-) present in water. These compounds are active disinfectant agents, capable of destroying microorganisms and organic materials. The effectiveness of free chlorine depends heavily on the pH of the water. At low pH, pre-domine hypochlorous acid, which strengthens disinfectant efficacy. For example, at a pH of 7, about 76.2% of free chlorine is in active form, while at pH 8, only 24.3% is active
- Combined Chlorine or Chloramines: These compounds are formed when free chlorine reacts with nitrogen organic materials present in water, including ammonia (NH3), to form chloramines such as monochloramine (NH2Cl) and dichloramine (NHCl2). Chloramines are less effective as disinfectants and are often responsible for the smell of "chlorine" and eye or skin irritation in swimming pools. Too high chloramines indicates ineffective disinfection and active free chlorine deficiency.
- Total chlorine: This is the sum of free chlorine and chlorine combined. Pool legislation generally sets a maximum limit for chlorine combined to ensure water quality. For example, the combined chlorine concentration should not exceed 0.6 mg/L compared to the concentration of free chlorine
- Active Chlorine (Measured through Redox by Flipr AnlaysR): This is the fraction of free chlorine that is actually available for infection. Its quantity can be calculated from free chlorine as a function of the pH of the water. The measurement of active chlorine is often done indirectly by measuring free chlorine and applying conversion tables that take into account the pH of the water.
- Potential Chlorine or Reserve Chlorine: This term refers to hypochlorite ions (IOC-) that are not as potent for deinfection as hypochlorous acid. They represent a chlorine reserve that can convert to active chlorine when the pH of the water is adjusted.
Chlorine Stabilizers: Compounds such as isocyanuric acid help protect chlorine from UV degradation. However, an excess of stabilizer can reduce chlorine efficiency and impede disinfection. Regulating the stabilizer is therefore essential to maintain chlorine efficacy in pool water.
It is important to regularly measure these different forms of chlorine and adjust pH to optimize chlorine disinfectant efficacy and ensure healthy and safe pool water. Regular testing and appropriate adjustment of chemicals are essential to maintaining the pool water.
Flipr measures Active Chlorine in your pond. This is chlorine that can disinfect your pond. This is measured by Redox / ORP (oxido-reduction factor).
Total chlorine = Free chlorine + Chloramines = Active chlorine + Potential chlorine + Chloramines
Active chlorine (Flipr/Redox) = Free chlorine - Potential chlorine
Measures Flipr measurements
It is very important to note that Flipr measures the oxidation-reduction potential (Redox / ORP) of water that represents the presence of Active Chlorine and therefore the ability to disinfection. This value is a component of Free Chlorine and Total Chlorine that are generally measured by tests such as strip, photometers or chemical reagents.
In conclusion, it is normal that you have different data between Flipr values and those measured by other traditional processes.
Measurement by photometer, drops or strips cannot be compared with active chlorine and therefore with FLipr measurements which displays only active chlorine (Redox / ORP).
Active chlorine is the most important plate because it represents the ability to detect real water disinfection
Redox
The Redox potential, also known as oxidation-reduction potential, is a measure of water's ability to oxidize contaminants, which is an indicator of its disinfectant power. Redox is expressed in millivolts (mV) and reflects the activity of oxidizing agents present in water â€" mainly active chlorine for swimming pools.
Here is how the Redox potential relates to the measurement of active chlorine:
- Direct Measurement of Active Chlorine: The Redox potential increases with the concentration of active chlorine, because chlorine is a strong oxidant. A high Redox value generally indicates that the water contains sufficient active chlorine to effectively disinfect.
- pH Awareness: The Redox potential is also affected by water pH. Since active chlorine efficacy is optimal in a certain pH range (generally around 7.2-7.6), pH variations can influence the Redox value even if the chlorine concentration remains constant.
- Disinfection Indicator: A Redox adequate measure can be considered an indicator that pool water is properly disinfected. Typically acceptable values for a good deinfection of pool water are around 650 to 750 mV, but this may vary depending on local guidelines and specific pool conditions.
- Ongoing Monitoring: Pool management systems such as Flipr can use the Redox measurement to continuously monitor the level of water disinfection. This allows automatic adjustments to water treatment, thus ensuring constant quality.
It is important to note that the Redox potential is influenced by all oxidants present in water, not just active chlorine. Other factors such as the presence of metals, ozone, or peroxides may also affect Redox measurements. This is why Redox measurements are often used in addition to other chemical tests to obtain a complete picture of the sanitary state of pool water.
Treatments
Chlorinated treatments are methods of water infection used to kill or inactivate pathogens. The main types of chlorinated treatments are used, particularly in the context of swimming pools:
- Sodium Hypochlorite (NaClO): Often known as " Bleach", it is one of the most common disinfectants. It is effective against many microorganisms and is easy to use. However, it can increase the pH of pool water.
- Calcium Hypochlorite (Ca(ClO)2): This treatment is similar to sodium hypochlorite but contains calcium, which can contribute to water hardness. It is particularly used in swimming pools where calcium intake is desired.
- Lithium Hypochlorite: Less common due to its higher cost, it is used in specific situations where other types of hypochlorites may be problem, such as in systems where sodium and calcium residues are undisirable.
- Sodium and Potassium Dichloro-isocyanurate: These compounds, available as granules or pellets, are used for "shock treatments" or point chlorations because of their good solubility and rapid effect.
- Trichloro-isocyanuric: This stabilized chlorine is often used for slow and regular treatment, in the form of slow-dissolving pebbles or pellets, placed in skimmers or distributors.
- Gas chlorination: The use of chlorine gas is a very effective method of deinfection, but requires special equipment and safety precautions due to gas toxicity.
- Salt electrolysis: In this system, salt (sodium chloride) is converted to chlorine through an electrolysis process that rolls in a cell installed in the pool return circuit.
Each type of chlorinated treatment has its own and inconvenience, and the choice depends on several factors, including pool size, budget, water management preferences, and local regulations. For all these treatments, it is crucial to regularly test water to ensure that active chlorine levels remain effective and safe for bathers.
Stabilizing
Chlorine stabilizer, mainly isocyanuric acid, plays a key role in protecting chlorine against degradation due to the sun's ultraviolet (UV) rays. However, the rate of stabilizer in pool water must be carefully managed to avoid problems of disinfection. Different cases of stabilizer rates that may be encountered in managing a pool:
Optimal Level:
In general, a level of stabilizer is considered optimal when it is between 30 and 50 ppm (parts per million).
This allows effective protection of chlorine without interfering with its disinfectant activity.
Low level:
A level below 30 ppm may not provide sufficient UV protection, resulting in rapid degradation of chlorine and increased consumption of disinfectant products.
This may result in a need to add chlorine more frequently to the pool to maintain effective disinfection.
High Level:
When the stabilizer rate exceeds 50 ppm, there is a decrease in chlorine efficacy.
Very high levels, such as more than 100 ppm, can result in "overstabilization" where chlorine becomes so protected that it is no longer effective for deinfection.
Overstabilization:
A stabilizer level greater than 100 ppm can almost completely block free chlorine activity.
This phenomenon of overstabilization generally requires dilution of pool water to bring the stabilizer level to an optimal level.
Legal Standards:
In France, for public swimming pools, legislation requires that cyanuric acid content be less than 75 mg/L to be compliant.
Excess stabilizer can result in chlorine blockage, preventing the formation of active chlorine required for effective infection at 12â€.
To properly manage stabilizer rates, it is recommended to perform regular tests with an appropriate test kit. It is also important to follow the recommendations of manufacturers of pool chemicals and public health guidelines for stabilizer levels.
When the stabilizer level is too high, it can not only reduce the effectiveness of free chlorine in pool water, but also affect the accuracy of Redox (reduction-oxidation) potential measurements performed by devices such as Flipr. The Redox potential is a measure of the ability of water to oxidize (or reduce) substances, and is directly influenced by the presence of active chlorine. A high stabilizer rate can block chlorine to prevent a reliable measure of Redox, as the amount of active chlorine available for deinfection is reduced. This makes it more difficult for monitoring systems such as Flipr to properly assess the water disinfectant potential, which is crucial for maintaining pool water quality and safety.
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