If effluent is introduced into a saturated soil mass, what is the likely outcome?

• A. The treatment process will proceed normally
• B. The effluent will be absorbed quickly with no pollution
• C. The treatment process will not proceed, and the effluent may pollute the groundwater
• D. The soil will drain immediately

Answer: (C)

When effluent enters soil that is already saturated, there’s no empty pore space for it to move into and be treated. The absorption and filtration that happen in an unsaturated zone rely on air in the pores and available space for water to percolate slowly through the root zone. In a saturated mass, the pores are filled with water, infiltration drops dramatically, oxygen is limited, and the microbial processes that normally break down contaminants aren’t operating as effectively. The result is that the effluent cannot be treated properly as it would in unsaturated soil, and it may linger or move toward the groundwater, raising the risk of groundwater pollution. That’s why the likely outcome is that the treatment process will not proceed effectively and the effluent may contaminate groundwater.