Tennessee Wastewater Operator Practice Exam

What can cause an increase in chlorine demand in the chlorine contact chamber?

1. Low temperature

2. Intermediate oxidation state of nitrogen

3. High salinity

4. Excessive filtration

The correct answer is: Intermediate oxidation state of nitrogen

An increase in chlorine demand in the chlorine contact chamber can occur primarily due to the intermediate oxidation state of nitrogen. This situation arises when there are forms of nitrogen present in the wastewater that are partially oxidized, such as nitrites or certain organic nitrogen compounds. These compounds require chlorine for their further oxidation or conversion into less harmful substances, thus increasing the overall chlorine demand. When chlorination is applied, the chlorine combines with these compounds instead of solely disinfecting the pathogenic microorganisms. This interaction results in a higher quantity of chlorine needed to achieve effective disinfection, as more chlorine is utilized for oxidation processes rather than for disinfection of the water itself. Low temperature influences the efficiency of chemical reactions but does not directly heighten chlorine demand in the context defined by the question. High salinity can impact the behavior of chlorine in water but does not necessarily lead to a significant increase in chlorine demand. Excessive filtration might improve the quality of the water but usually doesn't directly affect the chlorine demand negatively, rather it could reduce the amount of particulate matter that chlorine might otherwise have to react with.