What is the primary function of bacteria in a septic system?

The primary function of bacteria in a septic system is to break down waste materials. This process is essential for the effective operation of septic systems, as bacteria digest the organic matter found in wastewater. When household wastewater enters the septic tank, it contains various solids and organic materials. The anaerobic bacteria present in the tank thrive in the absence of oxygen and begin to decompose these materials, resulting in a reduction of solid waste and the production of simpler compounds.

This breakdown process not only helps to reduce the volume of waste but also facilitates the further treatment of the effluent as it moves into the drain field, where it can continue to be further treated by soil microorganisms. While the other choices mention aspects of septic system functions, they do not capture the primary role of bacteria. For instance, filtering water and removing solids are processes that mechanically or physically occur, rather than biological, like the breakdown of waste. The production of methane gas is a byproduct of the decomposition process but is not the primary function of bacteria in a septic system. Thus, breaking down waste materials is the foundational role, ensuring the system operates correctly and efficiently.