Basic Wastewater Operator Practice Exam

The amount of BOD in sludge entering a digester would be an indirect measure of what in the digester?

1. Plant matter

2. Food

3. Oxygen

4. Microorganisms

The correct answer is: Food

The amount of Biochemical Oxygen Demand (BOD) in sludge entering a digester serves as an indirect measure of the food available for microorganisms within that digester. BOD is a critical parameter that reflects the organic matter present in the wastewater, essentially indicating the amount of biodegradable material that could be oxidized by microorganisms. In the context of anaerobic digestion, which is a common process in wastewater treatment, the microorganisms rely on this organic matter as their source of food. The higher the BOD in the sludge, the more food there is for the microorganisms to consume and convert into biogas and other byproducts. This relationship between BOD and microbial activity is vital for the efficient operation of digesters, as the microorganisms play a crucial role in breaking down the organic material. Conversely, while the other choices—plant matter, oxygen, and microorganisms—are components or factors involved in the digestion process, they do not directly relate to the measurement of available food for those microorganisms in the same way that BOD does. Therefore, the amount of BOD in the incoming sludge effectively indicates the food source available for the microbial population within the digester.