Florida Wastewater Practice Test

How do chlorine (CL2), acid, and carbon dioxide (CO2) affect the pH level in wastewater?

1. Raise the pH

2. Have no effect on pH

3. Lower the pH

4. Stabilize the pH

The correct answer is: Lower the pH

Chlorine, acid, and carbon dioxide each play distinct roles in influencing the pH level of wastewater, and in this case, the correct answer is that they lower the pH. Chlorine, when introduced into water, can form hydrochloric acid (HCl) and other chlorinated compounds, contributing to a decrease in pH levels. This acidic reaction generally results in a more corrosive environment for the system, which can affect both the infrastructure and the biological treatment processes occurring in the wastewater. Acids directly lower pH by increasing the concentration of hydrogen ions (H+) in the water. When acids dissociate in solution, they release these ions, effectively lowering the pH and leading to a more acidic environment. This can be particularly relevant in wastewater treatment where precise pH levels are necessary for optimal microbial activity. Carbon dioxide behaves in a similar fashion when it dissolves in water. It reacts to form carbonic acid (H2CO3), which also dissociates into bicarbonate (HCO3-) and hydrogen ions. The increase in hydrogen ions results in a lower pH, thus contributing to the overall acidic nature of the wastewater. Understanding the effects of these substances on pH is critical in wastewater management to ensure