Texas Wastewater Class B Practice Exam

Which of the following is NOT a chemical characteristic of sewage?

1. pH

2. O2 Demand

3. Heavy metals

4. Dissolved oxygen

The correct answer is: Heavy metals

The correct identification of heavy metals as not a chemical characteristic of sewage is based on the typical parameters used to evaluate sewage. Most chemical characteristics refer to substances that are consistently present and measured in sewage to assess its quality and treatment needs. pH is crucial as it determines the acidity or alkalinity of the wastewater, influencing biochemical processes and chemical reactions during treatment. O2 demand, including biochemical oxygen demand (BOD) and chemical oxygen demand (COD), is essential for understanding the amount of oxygen required to decompose organic material in sewage. Dissolved oxygen is also a critical measure, indicating the amount of oxygen available in water, which is essential for aerobic microorganisms that break down organic matter. While heavy metals can be present in sewage, they are generally considered contaminants rather than standard chemical characteristics used for routine assessment of sewage. Their presence is more of a concern for specific industrial discharges or contamination events rather than a regular parameter in evaluating typical municipal wastewater.