Why wouldn't you pre-chlorinate?

Question

Why wouldn't you pre-chlorinate?

Answer 1

Without more details, I am taking an educated guess as to your waste stream.  In the areas I know where prechlorination can be done, it is the fact that prior, it can take 10-20 times the amount of chlorine to do it and it is much harder to control the residual.  Chlorine can react with many species (chemical and biological) and if you can take most of them out, your total chlorine usage will be much less.  There are some special cases where you have segregated streams that prechlorination can be done.

Answer 2

If you are talking about wastewater there is a possibility of formation of trihalomethanes and as the person told before lot of chlorine would be consumed than required.