Which factor does NOT contribute to stratification in a septic tank?

Stratification in a septic tank refers to the layering of different densities of materials, such as liquids, solids, and scum. Various factors influence this process, and among the choices, liquid temperature does not directly contribute to the stratification within the tank.

The input flow rate impacts how quickly waste enters the tank, which can affect the interaction of materials and influence stratification patterns. Retention time, or how long the influent remains in the tank, is crucial as it allows for the settling of solids, which contributes significantly to the formation of layers. Tank volume is also influential because larger tanks can lead to more effective stratification due to increased retention capacity and the ability to handle varying amounts of waste.

In contrast, while liquid temperature can influence biological activity and the decomposition of solids within the tank, it does not substantially affect the physical layering of materials. The physical properties that lead to stratification, like density differences among solids, liquids, and scum, are primarily dictated by the more immediate factors of flow rate, retention time, and tank size, rather than temperature variations. Hence, it is the absence of a direct connection between temperature and stratification that indicates it does not contribute to this process.