Final answer:
When the results from a secondary tank chlorine test are within the acceptable limits, one should continue monitoring without making any adjustments. This ensures the water stays properly disinfected without risking under or over-treatment.
Step-by-step explanation:
If the results from a secondary tank chlorine test are within the acceptable limits, the appropriate course of action would be a) Continue monitoring without any adjustments. This is because the existing chlorine levels are already adequate for disinfection purposes, and maintaining these levels is crucial for ensuring the safety and purity of the water supply. Adjusting chlorine concentrations when they are already appropriate could either lead to under-treatment or over-treatment both of which can be problematic. Under-treatment might not disinfect the water properly while over-treatment can lead to excessive chlorine residuals that might be harmful.
It is important to ensure that the water maintains its target chlorine residual to meet the chlorine demand. Chlorine demand is the amount of chlorine needed to react with all substances that can be oxidized by chlorine in the water while maintaining the desired residual for disinfection. This is determined by adding precalculated amounts such as those provided by compounds like sodium dichloro-s-triazinetrione ("dichlor") or trichloro-s-triazinetrione, to maintain safe effective and non-toxic levels of chlorine in the supply