California Wastewater Treatment Operator Practice Exam

What could happen if the digester gas is mixed with air (85 to 95% by volume)?

1. Enhance treatment efficiency

2. Cause foaming

3. Curb odor issues

4. Cause an explosion

The correct answer is: Cause an explosion

When digester gas is mixed with air in substantial volumes, it can create an explosive mixture. Digester gas primarily consists of methane, which is highly flammable. When oxygen from the air is present in the right proportions, it can lead to a highly explosive environment, especially when there is a spark or other ignition source. This is a significant safety concern in wastewater treatment plants that handle digester gas. While mixing digester gas with air may seem beneficial in some theoretical contexts such as improving combustion or reducing odors, the primary and most pressing concern is the potential for explosion, which poses a serious risk to personnel and infrastructure. Hence, in this scenario, the correct outcome associated with mixing digester gas with air in the mentioned proportions is the potential for an explosion.