ex 9: determination of Chlorine Demand Flashcards
what can be used to purify waters
physical or chemoical agents because they kill the microorganisms present
Why is chlorine a good way to purify water
because high lebvels of chlorine are not todxic to higher life forms
solutions of chlorine depend on what
the release of chlroine on its own (ie from sodium hypochlorite) and the oxidation of the enzymes and proteins by nascent O
ie hypochlorite to hypochlorous cid to hydrochloric acid + Nascent O
Because chrloine is a strong oxidizing agent…
it has a marked affinitiy for organic comppunds so water supplies with organic matter presnt have a chlorine demand
it is only the available chlorine that is not used by the chlroine demand that is bactericidal
What is chrline demand
Chlorine demand is defined as the amount of chlorine that is consumed or used up by the impurities, organic and inorganic substances,
When chlorine is added to water, it reacts with various substances such as organic matter, bacteria, algae, ammonia, and other reducing agents.
These reactions consume chlorine, reducing the amount of free chlorine available for disinfection.
the residual chrline is what is actually bactericidal
method
1) add 0.1 chlorine stock solutiom to A (peptone solution) and B the distilled water
2) Add 7 drops of orthotolidine reagent to the tube of A, mix and determine chrloine concentrationinitially (this will be the initial chrloine essetialy
3) do the same to the distilled water
4) add ecoli to each tube
5) put in lactose broth
how to calculate chlorine demand
initial chlorine conc- residual chlroine conc
or
Demand Free - Demand
results for lactose broth
peptone+chlroine (ecoli growth, so the chlorine demand was low)
distilled water and chlorine (no growth (purple no gas) chrloine demand was low (not used up alot so it had bactericidal properties)
Distilled water no chlroine (GRowth purple)
what does it mean if the chlroine demand is high
high chlorine demand means that a significant amount of chlorine is consumed by the substances present in the water before a measurable residual chlorine concentration is achieved. This indicates that there are many impurities, such as organic and inorganic materials, or high levels of microorganisms, which are reacting with and depleting the chlorine. Here are the implications of high chlorine demand:
