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Seidel, R. Sawhney, K. Methods Phys. A , — Download references. Philip E. Mason, H. Tillmann Buttersack, Ryan S. You can also search for this author in PubMed Google Scholar. In order to determine the amount of sodium hydroxide to add to your sodium hypochlorite solution, you will need to complete trial-and-error testing.
Add a known volume of sodium hydroxide to a known volume of sodium hypochlorite, and then measure the pH with a meter or kit. Because source water quality is different in each location, there is not one standard volume of sodium hydroxide to add to ensure pH is above You will have to start with a known volume perhaps 1 tablespoon in 1 gallon, or 5 ml in 1 liter and complete repeat trial-and-error testing.
The exact pH is not important in this context—you simply need to ensure that the pH level is above No, because when the sodium hypochlorite solution is added to water, the water decreases the pH and the sodium hypochlorite becomes more active. The chemistry behind this is: the pH scale is from 0 to Acids have a pH below 7, bases are above 7, and 7 is neutral.
Most natural water is around pH When sodium hypochlorite is in water, it is a mixture of two compounds, with the concentration of each compound dependent on pH. One of these compounds is significantly more reactive, volatile, and more effective at inactivating bacteria than the other.
At high pH above 11 the majority of the sodium hypochlorite is in the form of the less-reactive compound. Thus, when you add sodium hydroxide to the sodium hypochlorite, you are converting it into the less-reactive form.
However, water is around pH When you add a small amount 5 milliliters of solution at pH 11 to a large amount 20 liters of water at pH , the mixture becomes pH Thus, when you add the hypochlorite at pH 11 to your water in the SWS, you convert the hypochlorite back into the reactive form, and then it inactivates the disease-causing organisms.
This is very unlikely. If sodium hypochlorite is added to water that is already treated, the water would most likely still be within an acceptable range of chlorine residual. Typically, chlorinated urban water systems have free chlorine levels of around 0. We calculate our sodium hypochlorite solution dose to give untreated water a free chlorine level of around 1 part per million.
So if you add our solution to achieve 1 part per million to treated urban water 0. Chlorine is an extremely reactive chemical. Right after the sodium hypochlorite is added to the water, chlorine levels decline because the chlorine is reacting with inorganic and organic matter and microbes. After those reactions are complete, chlorine in water will slowly escape into the air as a gas.
This is the reason that free and total chlorine levels slowly degrade over time in a covered but not sealed container, and also why it is recommended that the pH level of the hypochlorite solution be raised to over 11 to extend the shelf life of the solution before it is used. Several factors make it unlikely that the hypochlorite solutions recommended in the Safe Water System could cause harm remembering that in most countries, the SWS SH is sold in ml bottles; in some countries, the ml bottles are used.
First, it is unlikely that a child would accidentally drink or milliliters of something that tastes as bad as the sodium hypochlorite does. Second, it is even less likely that, at the low concentration used in this project, anything harmful would occur. Despite these safety data, it is highly recommended that part of the educational materials emphasize the need to keep the sodium hypochlorite solution stored somewhere safe out of sunlight, sealed, away from children for health reasons; to protect the sodium hypochlorite from degradation; and to prevent spills in households that, due to limited incomes, would be unable to purchase more solution.
Giardia and Cryptosporidium are both protozoa and are highly tolerant to chlorination because they exist in water in a cyst or oocyst form. The hard coat of the cysts or oocysts protects Giardia and Cryptosporidium from being inactivated by chlorine.
Cryptosporidium is much more resistant to chlorine than Giardia see pathogen inactivation table for more details. Both protozoa, however, are fairly large, which means that they can be removed by filtration. If Giardia or Cryptosporidium are a significant health problem in the project area, a filtration step through ceramic, sand, or other filters can be added before adding the sodium hypochlorite.
Water that looks dirty or cloudy is called turbid water. Turbidity is a measure of the amount of light that is scattered as it passes through the water sample. If more particles are in the water, more light will be scattered, and the turbidity is thus higher. Turbidity is often used to represent the amount of total suspended solids and the amount of organic matter in the water.
Bacteria and other pathogens may also stick to particles in the water so high turbidity may increase the chance that there are pathogens in the water. There are two issues associated with adding chlorine to water that has a high turbidity: 1 Chlorine reacts equally with all the organic material in the water as well as with the bacteria and other pathogens.
Keep reading to find out the safe way to do it. Making a bleach solution to disinfect your home can be easy. You just need a few supplies to get started:. After gathering your supplies, putting together the ingredients safely requires a bit of know-how and preparation.
Wear clothes and shoes you don't mind messing up in case you spill some bleach. Pull back your hair and wear rubber gloves for added safety. When making a bleach solution, either go outside or find a well-ventilated room. Choose one with open windows and a cross-draft. Create a cross-draft by opening windows opposite each other or using a fan to direct the air. Full-strength bleach gives off toxic fumes and should never be used in small or closed-in spaces. The strength of the bleach mixture will depend on what you plan to use it for.
For example, to clean hard surfaces like plates and countertops, the ratio is This equals 1 cup milliliters of bleach to 5 gallons Never add any other ingredient to the bleach solution. These three are especially dangerous:. You can wash surfaces with soap and hot, clean water before using the bleach solution.
After applying the bleach solution, let the surface you are cleaning air dry. Chlorine bleach solution begins to lose its disinfectant power quickly when exposed to heat, sunlight, and evaporation when a liquid turns into a vapor or gas.
To make sure the solution is the right strength, mix a fresh batch each day and throw out whatever is left over. Always keep the bleach solution out of the reach of children. Do not reuse the bleach solution container for other cleaning products. Bleach is a powerful disinfectant that kills the germs that make people sick.
But it's important to learn how to use it safely whenever you try to clean things around the house. Using it the wrong way can lead to sickness or even death. Always add the correct amount of water to dilute the bleach before using it to clean.
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