What occurs during the process of anaerobic digestion in septic tanks?

During the process of anaerobic digestion in septic tanks, bacteria break down organic matter in the absence of oxygen, which significantly reduces the volume of solid waste. This process is essential in septic systems as it transforms complex organic materials into simpler compounds, resulting in a liquid effluent that is less harmful to the environment when properly treated.

Anaerobic digestion mainly occurs through the activity of specific types of bacteria that thrive without oxygen. These bacteria metabolize the organic waste, releasing gases such as methane and carbon dioxide as by-products while also producing a reduced amount of solid waste. This is crucial for the effective functioning of a septic system, as it minimizes the solids that need to be removed during maintenance.

The other options do not accurately describe the anaerobic digestion process. For instance, the presence of oxygen is not conducive to anaerobic digestion, and therefore, the breakdown of organic waste would not occur under those conditions. Additionally, anaerobic digestion does not involve the extraction of minerals or the conversion of wastewater into clean water without treatment—these processes require other forms of treatment and filtration. Thus, option B provides a precise understanding of the anaerobic digestion process occurring in septic tanks.