What is the primary purpose of the ET system's drainfield?

The primary purpose of the evaporative-transpiration (ET) system's drainfield is to absorb and purify wastewater. In an ET system, wastewater is effectively treated as it percolates through the soil in the drainfield. This soil acts as a natural filter, where microorganisms break down harmful pathogens, organic matter, and nutrients present in the wastewater. By allowing the water to infiltrate the ground, the drainfield helps protect the surrounding environment by ensuring that the treated effluent is clean before it enters the groundwater or surrounding areas.

In contrast, other options do not align with the main function of a drainfield. For instance, while the drainfield allows for some level of moisture release into the environment, its primary role is treatment rather than storage. Additionally, the system does not aim to release excess chemicals, as that would negate the purpose of purification. Lastly, while the water may contribute to the irrigation of nearby plants indirectly, that is not the defined goal of the drainfield; its focus remains on the absorption and treatment of wastewater rather than providing irrigation directly.