Question

why should we not use chorine tablets than specified

Answer 1

If you have ever smelled laundry bleach, or been in a swimming pool and noticed a smell to the water- that is the smell of chlorine (in a fairly mild form). Pure chlorine gas is pale green, has a choking, burning smell, and is deadly to breathe. Whether it is "worse" than the smell of wastewater would depend on the purity of the chlorine you smell- the more pure, the worse the smell.