Texas Wastewater Class B Practice Exam

What is formed when ammonia reacts with chlorine in wastewater?

1. Chlorine gas

2. Chloramines

3. Ammonium chloride

4. Hydrochloric acid

The correct answer is: Chloramines

When ammonia reacts with chlorine in wastewater, chloramines are formed as a result of the reaction. Chloramines are a group of compounds that are created when ammonia (NH3) comes into contact with free chlorine (Cl2). This is a key process in wastewater treatment because chloramines can serve as secondary disinfectants, offering a longer-lasting form of chlorination compared to free chlorine alone, which tends to dissipate quickly in water. Chloramines have lower toxicity than free chlorine and can be useful in controlling the formation of harmful disinfection by-products. They also help in maintaining residual disinfection in the water system, ensuring that any microbial contaminants are effectively managed. In contrast, chlorine gas itself would not be a product of the reaction with ammonia, and neither would ammonium chloride or hydrochloric acid be formed directly from this interaction. Ammonium chloride can form under different conditions but is not the primary product when chlorine acts on ammonia in this specific context. Hydrochloric acid might arise from the reaction of chlorine with water, but it does not relate directly to the interaction between ammonia and chlorine.