Find out how to best use chlorine for better sanitation in factories. Learn how to save money and improve efficiency by maintaining different levels in different situations.
The History of ChlorineChlorine was first used as a disinfecting agent in water and has since proven its efficacy for over a century. It has greatly improved the quality of life wherever is has been used in the war against infectious diseases, including cholera, typhoid and dysentery. It is the most widely used and inexpensive weapon available to kill undesirable micro-organisms, including bacteria, some viruses and protozoa.
In the past, very high rates of Chlorine were often used. Studies have shown that toxic by-products can result when high concentrations of Chlorine are used. Thus, it is important to obtain the correct balance – enough to kill the undesirable micro-organisms without harmful and wasteful overuse.
This is complicated by the properties of Chlorine. Once the chlorine in a solution has killed the micro-organisms, it binds to these particles and this chlorine is no longer “free” to disinfect further micro-organisms. Thus, we need to monitor chlorine concentrations to ascertain how much free chlorine is available.
pH and Chlorine
pH also needs to be monitored, as it has a great effect on chlorine. Between pH 6.5 and 7.0, free chlorine is 80 – 95% available. At pH greater than 8, the free chlorine concentration is less than 20%.
As part of a Quality Assurance Programme, it is important to remember the three R’s:
READ, RECORD parameter levels and REACT if they do not fit within the desired range.
Chlorine Test Kits measure the “free available Chlorine” in the process. They use colour comparisons to measure the amount of Chlorine in the solution. The higher accuracy of professional test kits also means that the tests conform to audit standards.
When measuring High Chlorine ranges (10 mg/l upwards), Potassium Iodide is used as a reagent, instead of the more common DPD tablets used to measure lower ranges. When measuring a range above 200 mg/l, a dilution will need to be done. This is very easily done in a Lovibond® Dilution Tube, which has dilution levels indicated on the side, eg 2x, 4x … The sample is diluted with distilled water.
A manual system which works in a way similar to a child’s viewfinder, such as the Lovibond® CheckIt Comparator & Disc system, can be used. This is a more economical option.
Alternatively, a modern electronic photometer, such as the Lovibond® MD100 is ideal.
5 Factors affecting Chlorine Efficacy:
- Oil, Dirt & Organic Material
- These cause chlorine to quickly lose its effectiveness.
- Wash water should be changed when it becomes dirty. For very dirty produce, it is best to remove excess dirt prior to the sanitizing treatment.
- The relative temperatures of food and disinfectant have an influence.
- Chlorine activity increases with warmer temperatures. It is recommended that the temperature of wash water be at least 10°C higher than that of fruits or vegetables.
- However, at high temperatures, chlorine compounds may release chlorine gas which is toxic. The level of corrosion also increases as temperatures go up.
- The recommended range for a chlorine solution is 6.5 – 7.0.
- Solutions with a pH lower than 6.0 are more corrosive – this can cause equipment to wear out. pH values lower than 5.0 generate harmful levels of chlorine gas.
- pH values greater than 8.0 are ineffective sanitizers, leaving harmful micro-organisms intact.
- Do not add acid, such as vinegar, to a chlorine solution without monitoring its pH. This can produce a toxic gas.
- Detergent residues are usually alkaline. If residues are left on surfaces, this will also cause a problem.
NB: WASH WITH HOT, SOAPY WATER, THOROUGHLY RINSE AND THEN SANITIZE WITH CHLORINE SOLUTION.
- High concentrations increase the effectiveness.
- A concentration of 50 – 200 ppm is recommended for some common usage, such as disinfection of food contact surfaces.
- If you are using a solution stronger than 200 ppm, rinse the surface with clean water after a few minutes of application.
- High concentrations are not recommended as they can cause an undesirable taste, ill-health, corrosion and even explosions.
- Longer exposure time increases the effectiveness.
- Contact times of one to five minutes are usually sufficient to achieve a thorough sanitization, depending on the above factors.
- Do not let the chlorine solution stay in contact with equipment for more than 30 minutes or it could corrode.
Storage of Chlorine:Chlorine is an unstable chemical, especially in a water solution. It can dissipate quickly, reducing its content and effectiveness. Chlorine powders (calcium hypochlorite, such as HTH) should be used to sanitize in commercial operations.
Preparation of a Chlorine Solution:
- To prepare a 100 ppm (parts per million) sanitizing solution, mix 15 g Calcium Hypochlorite with 100 liters water.
- To prepare 200 ppm solution, mix 15 g with 50 liters water.
- Test periodically with a chlorine testing kit to ensure that the free (available) chlorine does not drop below the acceptable range for your application, for example 50 ppm.
Maintaining Chlorine Levels:
A Sanitation Programme is most effective when Chlorine is measured continuously. It is ineffective to simply dump Chlorine into the container / tank occasionally. Similar to maintaining a healthy blue pool, one needs to Remember the three R’s: READ, RECORD parameter levels and REACT if they do not fit within the desired range.
Chlorine Test Kits measure the “free available Chlorine” in the process. They use colour comparisons to measure the amount of Chlorine in the solution. A manual system which works in a way similar to a child’s viewfinder, such as the Lovibond® Colorimeter Comparator & Disc system, can be used. Alternatively, a modern electronic photometer, such as the Lovibond® MD100 is ideal.
Chlorine in Specific Industries:
- On the Farm
- Fresh Fruit & Vegetables
- Food Service & Restaurants
- Meat, Poultry & Egg
- Fish & Seafood
Updated Aug. 2018.
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