Tennessee Wastewater Operator Practice Exam

A high sewage pH can result in the production of toxic gases due to which of the following?

1. Hydrogen

2. Nitrogen

3. Ammonia

4. Methane

The correct answer is: Ammonia

A high sewage pH can lead to the production of toxic gases primarily due to the release of ammonia. When the pH of sewage increases, it promotes the conversion of ammonium ions (which are less toxic) into free ammonia gas, a process that is pH-dependent. Free ammonia is significantly more toxic to aquatic life and can create hazardous conditions in wastewater systems. High pH levels can also enhance the volatilization of ammonia, meaning that it can be released into the atmosphere more readily, contributing to air quality issues and posing a risk to workers in sewage treatment facilities. This relationship between pH and ammonia production is crucial for wastewater operators, as they need to monitor and manage pH levels to minimize the formation of toxic substances. Other gases that might be produced in a sewage environment — such as hydrogen, nitrogen, or methane — do not have the same direct association with high pH levels or pose a comparable toxicity concern resulting from an increase in pH.