 Today's topic is break point chlorination. So break point chlorination is coming under water purification the last step chlorination. So water purification has three steps in slow sand the first step is storage whereas in rapid sand it has coagulation, flocculation, sedimentation then it reaches to the filtration chamber and finally it reaches the disinfection or chlorination chamber that is chlorine will be added to the water to make it portable or drinkable. So first we should understand what is turbidity so the chlorine we add to the water depends on the turbidity, turbidity is nothing but how dirty the water is what how much amount the contamination present in the water so the bacteria and other pathogens and other contaminants. So more turbid we need more chlorine less turbid means less chlorine more turbid means it is more dirty less turbid means it is less dirty so it is directly proportional to the amount of chlorine. So now let's see what is break point chlorination suppose you take one liter of water that is filtered water after the filtration step you take one liter of water and you keep adding chlorine. Chlorine can be added by various methods chloramide and HTS or chlorine gas whatever the method in the one liter of water we add chlorine so we keep adding like 1.5 gram or 1.6 gram so we keep adding just like how we did in our PUC or Plesto time the chemistry lab experiment 0.1 gram 0.1 gram we keep on adding and see what is happening inside the one liter of water so we increase the amount so it all get dissolved in this water because that much chlorine is required to decontaminate or disinfectant all the bacteria and other pathogens. So we keep on adding all get dissolved so we add 1.6, 1.7 till we add 2.4. Now 2.5 what happens is when we add 2.4 nothing happens this is just a hypothetical example based on the turbidity this amount will be changed more turbid means we need to add more chlorine. So when we add 2.5 there will be chlorine present in the water. This is known as free residual chlorine when the water is having free residual chlorine or the moment when the free residual chlorine appears in the water is known as break point chlorination. So till 2.4 it is dissolved so it was completely dissolved but 2.5 it starts reappearing because the water is completely disinfected there is no need of any chlorine for this water that is all bacteria all pathogens all contaminants is completely killed or destroyed by 2.4 grams of water. So what happens the next amount will start appearing so just like saturation once the saturation reaches the amount will be or the whatever we add in the water will be precipitated. So if we add sugar or salt in water once it reaches saturation it will not be dissolved anymore it starts precipitating the same way once it completely destroyed the bacteria other pathogens it start it is creating residues the residues will be formed in the water. That particular point is known as break point chlorination and this particular amount is known as chlorine demand it is nothing but same it is a technical name when the residual chlorine appears and this amount is known as chlorine demand and this depends this break point chlorination depends on turbidity if it is very much dirty we need more water more chlorine so it we reach sometimes at 3.5 or sometimes at 4.5 if it is very less turbidity more clear water it may reach at 1.6 or it may reach at 0.8 break point chlorination reaches so it all depends on the turbidity how dirty it is. So once we get this break point chlorination or chlorine demand what we need to do we need to add a 0.5 milligram so we get the required amount of chlorine for 1 liter of water why we need this 0.5 because it should be present 1 liter of water for 1 hour period after 1 hour period there should be presence of 0.5 milligram of free residual chlorine for make it to a drinkable water so this much amount should be there so this is break point chlorination and this is free residual chlorine so total is 3 milligram per liter so how much our this amount we multiply with 3 if we have 1000 liter we multiply with 1000 or 1 lakh liter we multiply it with and we add that particular amount to this water so that is a concept of break point chlorination or chlorine demand if it is very much high if it is 4.5 we just add 0.5 and we get 5 milligram per liter so that is the chlorine requirement we add 1 liter 5 milligram how much our liter is present we multiply and find out the total chlorine requirement so that is all about break point chlorination it is a very simple concept sometimes you get confused what is break point chlorination and chlorine demand it is more or less similar this is that technical term when this free residual chlorine appears and that particular amount is known as chlorine demand so that is break point chlorination I will come up with a new session on dentistry and more thank you.